Evaluation of natural and anthropogenic influences on the Guadalquivir River (Spain) by dissolved heavy metals and nutrients

Influence of the Atlantic inflow on trace metal enrichments in sediments and particulate matter of the NW Alboran Sea (SW Mediterranean)

Trace metal contents and fluxes in downward particulate matter and dated sediment cores of the NW Alboran Sea are analysed in this study with the aim of assessing the role of the Atlantic inflow on their transport. Increases in Zn, Cu and Pb were detected in downward particulate matter collected by sediment traps after river flooding events and after the Aznalcollar mining spill. Their arrival coincided within the recently estimated time range for river particles discharged into the Gulf of Cádiz to reach the Alboran Sea, indicating that their transfer is enhanced during events of increased river inputs of contaminated particulate matter. This also suggests that the effects of potential tailing dam failures in the Gulf of Cádiz watersheds could reach the Alboran Sea. These trace metals also increased in the sediment cores from the continental rise since the second half of the 19th century, suggesting that contaminated particles have been continuously transferred towards the Mediterranean Sea since that time, when mining concessions and production increased in the SW Iberian Pyrite Belt.

Assessment of seasonal and annual patterns in phosphorus content in a monitored catchment through a partitioning approach based on hydrometeorological data

High amounts of phosphorus (P) in rivers come mainly from two sources: fertilizers washed off from agricultural and urban areas by runoff water (non-point sources) and urban and industrial development which are translated in P discharges from wastewater treatment plants (WWTP). This work analyses the content of P in water for nearly 40 years inquiring into the origin of the sources, based on the hypothesis of runoff generation from the detection of river streamflow increases during the P contribution episode and the previous precipitation. For this purpose, the Guadaira River, which is located in the South of Spain and has a drainage surface of 1524 km2, was selected. In this watershed agricultural land use converges with numerous human activities resulting in high pressures on water quality. We found 40% of the P contribution episodes found seem to come from the runoff generated after the heaviest rainfall events, which normally occur between November and May. The remaining 60% of the P contribution episodes were found to be linked to point sources, which become more relevant from June to September, reaching the highest concentration values (6-17 mg/L). The results highlight that the target phosphate concentration value of 0.34 mg PO4/L imposed by the national legislation for a good state following the Water Framework Directive 2000/60/EC is exceeded by 96% of the measurements during the period from 1981 to 2022. On a monthly basis, PO4 loads showed a linear relationship with river streamflow (R2 = 0.94). However, on field measurements scale, a potential relationship between both variables was found, which changed according to the improvement in the wastewater treatment and facilities for 1982-1994, 1995-2017 and 2018-2022. In these three periods, different significant decreasing trends of the P content were found, mainly marked by the setup of each individual WWTP.

Long-term performance of a deep oxidation pond with horizontal subsurface flow constructed wetland for purification of rural polluted river water

A full-scale deep oxidation pond with horizontal subsurface flow constructed wetland (DOP-HSCWs) was constructed and used to investigate the nutrient removal and establish a practical inversion prediction model. The high long-term performances of nearly 7 years were obtained with the average removal efficiencies of 76.48 ± 10.11% (chemical oxygen demand, COD), 60.61 ± 29.21% (ammonia nitrogen, NH4+-N), 54.04 ± 21.92% (total phosphorus, TP) and 88.44 ± 6.86% (suspended solids, SS), respectively. The removal efficiency actually increased after 2016 with outflow concentrations lower as compared to initial phase of operation. The effluent concentration in autumn were obviously higher than that in other seasons because of high influent loadings. The Flaml model achieved good performance demonstrating the ability to predict water quality of DOP-HSCWs without human intervention. In addition, COD, NH4+-N, TP concentration of effluent can be significantly affected by SS concentration of influent according to the generalized additive model (p < 0.001). Compared with HSCWs, the DOPs was mainly contributed to pollutant removal. In summer, Cyanobacteria, Cyanobacteria and Proteobacteria were dominated in DOPs, while Proteobacteria was dominated in winter. Although the relative abundance of Proteobacteria in anaerobic zone decreased by 14.99%, the relative abundance of Firmicutes and Chloroflexi increased by nearly 10%, which ensured decontamination effect of the DOPs. Proteobacteria was also dominated in HSCWs, but it was lower than that in DOPs. This study indicated that DOP-HSCWs can achieve a sustainably excellent purification of rural polluted river water during the long period of operation.

Exploring the trend effects of diffuse anthropogenic pollution in a large river passing through a densely populated area

The detection of non-point pollution in large rivers requires high-frequency sampling over a longer period of time, which, however presumably provides data with large spatial and temporal variance. Variability may mean that data sets recorded upstream and downstream from a densely populated area overlap, suggesting at first glance that the urban area did not affect water quality. This study presents a simple way to explore trend-like effects of non-point pollution in the Danube based on data that varied strongly in space and time. For one year, biweekly sampling was carried out upstream and downstream from a large city with negligible emission of untreated wastewater and the surrounding settlements, industrial and agricultural areas. Although most of the values of the 34 examined physicochemical characteristics fell within the range of data previously published for the Danube, and the mean values of all parameters indicated unpolluted surface water, different water quality was revealed upstream and downstream from the metropolitan area at each sampling time. Since the physicochemical characteristics causing the separation also differed from time to time, univariate tests and consensus ordination were used to determine which variables changed similarly during most of the examined period. With this evaluation method, several diffuse pollutants of anthropogenic origin contaminating the Danube in the long term were identified, such as nitrogen, phosphorus, sulphate, chloride, potassium and vanadium. The results demonstrated that trend-like effects of non-point pollution can be detected even in a large river, where physicochemical measurements can vary strongly in space and time.

Biosorption of Pb(II) Using Natural and Treated Ardisia compressa K. Leaves: Simulation Framework Extended through the Application of Artificial Neural Network and Genetic Algorithm

This study explored the effects of solution pH, biosorbent dose, contact time, and temperature on the Pb(II) biosorption process of natural and chemically treated leaves of A. compressa K. (Raw-AC and AC-OH, respectively). The results show that the surface characteristics of Raw-AC changed following alkali treatment. FT-IR analysis showed the presence of various functional groups on the surface of the biosorbent, which were binding sites for the Pb(II) biosorption. The nonlinear pseudo-second-order kinetic model was found to be the best fitted to the experimental kinetic data. Adsorption equilibrium data at pH = 2-6, biosorbents dose from 5 to 20 mg/L, and temperature from 300.15 to 333.15 K were adjusted to the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. The results show that the adsorption capacity was enhanced with the increase in the solution pH and diminished with the increase in the temperature and biosorbent dose. It was also found that AC-OH is more effective than Raw-AC in removing Pb(II) from aqueous solutions. This was also confirmed using artificial neural networks and genetic algorithms, where it was demonstrated that the improvement was around 57.7%. The nonlinear Langmuir isotherm model was the best fitted, and the maximum adsorption capacities of Raw-AC and AC-OH were 96 mg/g and 170 mg/g, respectively. The removal efficiency of Pb(II) was maintained approximately after three adsorption and desorption cycles using 0.5 M HCl as an eluent. This research delved into the impact of solution pH, biosorbent characteristics, and operational parameters on Pb(II) biosorption, offering valuable insights for engineering education by illustrating the practical application of fundamental chemical and kinetic principles to enhance the design and optimization of sustainable water treatment systems.

Dissolved metal assessment in surface seawater: A spatial-seasonal evaluation in the Zhejiang coastal waters, the East China Sea

The spatial-seasonal distributions and variations, correlations with environmental variables and the pollution degrees of dissolved metals in the Zhejiang coastal seawater were investigated. The concentrations of six dissolved metals (i.e. Cu, Pb, Zn, Cd, As and Hg) were in the ranges of 0.10-6.40 (1.6 ± 0.8), 0.16-3.60 (1.2 ± 0.7), 2.50-24.0 (8.5 ± 4.8), 0.011-0.180 (0.07 ± 0.03), 0.85-4.20 (2.1 ± 0.8) and 0.001-0.110 (0.06 ± 0.02) μg/L, throughout the four seasons, respectively. Significant differences in all the dissolved metals were found among seasons, whereas no significant differences were found among stations. The average concentrations of metals were in the following order: Zn > As>Cu > Pb > Cd > Hg. Single metal contamination factor was in the following order: Pb > Hg > Zn > Cu > As>Cd. The pollution level of dissolved metals in the Zhejiang coastal waters (ZCW) was low. Most of the dissolved metals were correlated to temperature, indicating seasonal differences. The redundancy analysis (RDA) indicated that depth, temperature, nitrate and phosphate could best explain the variance pattern of dissolved metals in the ZCW.

Effects of maintenance dredging on the macrofauna of the water column in a turbid estuary

Many human activities in or near aquatic habitats generate alterations in their environmental conditions, which could affect the organisms that inhabit them. Maintenance dredging of navigation channels in order to allow large ships access to inland ports is one such source of disturbance. In this study, by taking multiple approaches (immediate-, short- and medium term), we analysed the effects of a maintenance dredging operation on physiochemical variables and the early life stages of fish and other macrofauna groups present in two zones of the Guadalquivir estuary with different salinity ranges (poly- and mesohaline). Most physiochemical variables were homogenized in the water column immediately after the water mass passed by the dredger, including sediment resuspension. However, this process seemed to be transient as no significant increments in the depth-averaged levels of turbidity were observed in the short- and medium-terms. Instead, metal concentrations of Cr, Fe and Zn increased in the polyhaline station. Even so, these perturbations did not appear to be severe enough to influence the macrofauna. Still, organisms can suffer direct mechanical impacts of the trailer suction. Hyperbenthic species, like Pomatoshcistus spp. or decapods, tended to decrease slightly, while pelagic species such as Engraulis encrasicolus or mysids did not, indicating that benthic organisms are usually more susceptible to high entrainment. Nonetheless, the possible effects of this disturbance were of the same order or less than those of natural ones; therefore, organisms of the macrofauna could be well adapted to cope with them.

The fate of Guadalquivir River discharges in the coastal strip of the Gulf of Cádiz. A study based on the linking of watershed catchment and hydrodynamic models

A catchment model for river basins and a hydrodynamic model were combined in order to simulate the spreading of the turbidity plume produced by sediment discharges from the Guadalquivir River basin within the Gulf of Cádiz under different meteorological conditions. The current fields provided by the hydrodynamic model and a transport-diffusion scheme based on tracking virtual particles tracking released at the river mouth have enabled us to simulate turbidity plumes that show great similarity with the plumes observed in satellite images. The most relevant results of the study show that in the absence of winds, the plume tends to spread very slowly, gradually progressing northwards; this is because of the symmetry between the filling and draining flows at the mouth of the Guadalquivir and low intensity of the tidal currents beyond the mouth. In addition, the transport of the plume towards the Strait of Gibraltar requires wind conditions with a northerly, north-westerly or westerly component. Westwards transport, however, requires winds with an easterly, southerly, or south-easterly component. The periods of heaviest rainfall in the Guadalquivir River basin coincide with winds mainly from the west; therefore, the times of maximum discharge at the mouth of the river occur when there are wind conditions that favour the transport of the matter suspended in the plume, southwards along the coast, towards the Strait of Gibraltar and the Alboran Sea. Linking the watershed catchment and hydrodynamic models has proved its suitability to predict the evolution and reaching of the sediment plumes from the Guadalquivir River discharges and the experience encourages the use of that methodology to be applied in a future prediction system for the creation and evolution of those sediment plumes.

Dissolved rubidium to strontium ratio as a conservative tracer for wastewater effluent-sourced contaminant inputs near a major urban wastewater treatment plant

Municipal wastewater (MWW) effluent discharges can introduce contaminants to receiving waters which may have adverse impacts on local ecosystems and human health. Conservative chemical constituents specific to the MWW effluent stream can be used to quantify and trace wastewater effluent-sourced contaminant inputs. Gadolinium (Gd), a rare earth element used as a contrasting agent in medical magnetic resonance imaging, can be found in urban MWW streams. Dissolved anthropogenic Gd has been shown to be an indicator and potential conservative tracer for MWW effluent in receiving waters. Like other known MWW tracers, it can be difficult and expensive to measure. Dissolved rubidium (Rb) to strontium (Sr) ratio enrichment in biological materials such as blood and urine can lead to enriched Rb/Sr values in MWW effluent relative to natural waters. This ratio is relatively easy and inexpensive to measure and represents a promising additional indicator for MWW effluent in receiving waters in urbanized freshwater systems. In July 2015 and 2016 surface water samples were collected from sites in the tidal-fresh Potomac River in the vicinity of the Blue Plains Advanced Wastewater Treatment Plant (BPAWWTP) outfall near Washington, DC USA along with treated MWW effluent samples from the BPAWWTP. Dissolved Rb/Sr ratios were measured in these waters and compared to dissolved Gd concentrations in order to demonstrate the potential of the dissolved Rb/Sr ratio as a conservative indicator for MWW effluent. Results suggest the dissolved Rb/Sr ratio represents a simple and cost-effective indicator and conservative tracer for MWW effluent. It can be used with, or in place of, other proven tracers to investigate wastewater impacts in highly-urbanized, anthropogenically-impacted freshwater systems like the tidal fresh Potomac River and perhaps in a wider range of geologic settings than previously thought. A case study is presented as an example to demonstrate the potential of using dissolved Rb/Sr ratios to trace MWW-sourced nutrient inputs from a major WWTP like BPAWWTP to the receiving waters of tidal-fresh Potomac River.

Rapid monitoring of heavy metal pollution in lake water using nitrogen and phosphorus nutrients and physicochemical indicators by support vector machine

A novel method of predicting heavy metal concentration in lake water by support vector machine (SVM) model was developed, combined with low-cost, easy to obtain nutrients and physicochemical indicators as input variables. 115 surface water samples were collected from 23 sites in Chaohu Lake, China, during different hydrological periods. The particulate concentrations of heavy metals in water were much higher than the dissolved concentrations. According to Nemerow pollution index (Pi), pollution degrees by Fe, V, Mn and As ranged from heavy (2 ≤ Pi < 4) to serious (Pi ≥ 4). The concentrations of most heavy metals were the highest during the medium-water period and the lowest during the dry season. Non-metric Multidimensional Scaling Analysis confirmed heavy metal concentrations had slight spatial difference but relatively large seasonal variation. Redundancy Analysis indicated the close associations of heavy metals with nutrient and physicochemical indicators. When both nutrient and physicochemical indicators were used as input variables, the simulation effects for most elements in total and particulate were relatively better than those obtained using only nutrient or only physicochemical indicators. The simulation effects for As, Ba, Fe, Ti, V and Zn were generally good, based on their training R values of 0.847, 0.828, 0.856, 0.867, 0.817 and 0.893, respectively, as well as their test R values of 0.811, 0.836, 0.843, 0.873, 0.829 and 0.826, respectively; and meanwhile, in both the training and test stages, these metals also had relatively lower errors. The spatial distribution of heavy metals in Chaohu Lake was then predicted using the fully trained SVM models.

Hydrochemical Assessment of the Irrigation Water Quality of the El-Salam Canal, Egypt

The El-Salam canal in Egypt is considered an important stream of fresh water for the agricultural sector that extends from the Nile River to Sinai, while it is subjected to several anthropogenic stresses. In this study, five-georeferenced stations (named from S1 to S5) were monitored along the El-Salam Canal before El-Sahara of the Suez Canal, via the estimation of the WQ index based on major cations and anions analysis including salinity hazard, permeability index, residual sodium carbonate, magnesium hazard, sodium percentage, sodium adsorption ratio, Kelley index, potential salinity, total hardness, and irrigation water quality index (IWQI). The sequence of average concentration of cations in water were Na+ > Ca2+ > Mg2+ > K+. The major cations constitute around 60% of the total dissolved salts. While the sequence of major anions in water were SO42− > HCO3− > Cl− > CO32−. These cations and anions showed an increasing trend from S1 (intake of the canal) to S5 (before El-Sahara) of the El-Salam Canal. Moreover, the order of heavy metals was Zn < Cd < Cr < Ni < Fe < Mn < Co < Cu < Pb. According to the US EPA (1999) guidelines, the levels of Fe and Zn in the El-Salam Canal are within the permissible limits for drinking and irrigation purposes, while Mn, Pb, Cu, Co, Ni, Cr, and Cd were detected at higher concentrations than those recommended. The value of IWQI in water samples varied from 40.26 to 114.82. The samples of S1 showed good water, the samples of region S2 (after mixing with Faraskour drainage) showed poor water quality, samples of regions S3 (after mixing with the El-Serw drain waters) and S5 (before El-Sahara) fell under the very poor water category and samples of region S4 (after mixing with the Hadous drainage) showed unsuitable water. Croplands irrigated with such water will not be exposed to any alkaline risks but will be exposed to the risk of salinity, which is more severe after mixing at the S3 and S4 sites. It is recommended to treat the drainage water before mixing with the irrigation water of El-Salam Canal to raise the suitability of irrigation water for crops, particularly for the Hadous drain.

Spatiotemporal Variation Characteristics of Water Pollution and the Cause of Pollution Formation in a Heavily Polluted River in the Upper Hai River

Blackening and odorization of heavily polluted rivers has become a serious concern and threat to ecological and human health. This paper aims to gain a deeper understanding of changes in water pollution and the cause of pollution formation in a heavily polluted river in the upper Hai River. In this study, comprehensive water quality index (CWQI) and multivariate statistical techniques (MSTs) were applied to assess the spatiotemporal variation characteristics of water pollution and to identify potential pollution sources. The seasonal Mann–Kendall (SMK) test and the SMK test of flow-adjusted concentrations were effectively used to explore the temporal variation trends of major pollutants and the causes of their formation. Data of 15 water quality parameters were analyzed during 1980–2018 at 19 monitoring sites in the mainstream and major tributaries of the Xinxiang Section of the Wei River (XSWR). The results showed that the rivers were seriously polluted from 1991 to 2009, but the water quality improved after 2010. Nineteen sampling sites were divided into a low pollution region and a high pollution region. In the flood season, the pollution sources were mainly domestic sewage, industrial wastewater, agricultural runoff, biochemical pollution, and natural sources. In the nonflood season, the pollution sources were mainly domestic sewage and industrial wastewater. In recent years, the water quality of seriously polluted river has generally improved, mainly due to reductions in pollutant discharge from point sources and nonpoint sources.

The assessment of metal contamination in water and sediments of the lowland Ilova River (Croatia) impacted by anthropogenic activities

The aim of the present study was to assess physico-chemical water parameters, granulometric sediment characteristics and concentrations of trace and macroelements in the water and sediments of the Ilova River. Samplings were conducted at three sampling sites (near villages Maslenjača, Ilova and Trebež) along the Ilova River, differing in the source and intensity of the anthropogenic influence. This study indicated disturbed environmental conditions, most pronounced in the downstream part of the river (Trebež village) impacted by the activity of fertilizer factory. Water from the Ilova and Maslenjača villages was of good quality, whereas COD, nitrates and phosphates exceeded the good quality levels in Trebež village. Trace and macroelement concentrations in water were mostly below thresholds set by environmental quality standards at all locations, but levels of Al, As, Cd and Ni were few times higher in Trebež village than at other locations. Metal contamination assessment of sediments (trace and macroelement concentrations, contamination and enrichment factor, pollution load index) confirmed deteriorated environmental quality in Trebež village. However, the overall assessment performed in this study revealed that anthropogenic impact was still not particularly strong in the Ilova River ecosystem. Nevertheless, the observed water and sediment characteristics serve as a warning and suggest that stricter protection measures should be initiated, including continuous monitoring and comprehensive quality assessment of the downstream part of the Ilova River, especially because it is a part of the protected area of the Lonjsko Polje Nature Park.

The role of the Gulf of Cadiz circulation in the redistribution of trace metals between the Atlantic Ocean and the Mediterranean Sea

The GoC shelf waters present much higher concentrations of dissolved Cu, Cd, and Zn than other coastal areas, constituting an important source of these elements onto its neighbouring basins, i.e., the Atlantic Ocean and the Mediterranean Sea. In this study we assessed the role of the GoC surface currents in the trace metals transport. For this purpose, ten dissolved (<0.22 µm) trace metals were sampled (Ag, Cd, Co, Cu, Fe, Mo, Ni, Pb, Zn, V) along the GoC continental shelf, and their spatial and temporal distribution was interpreted according to the surface circulation. Results show that the complex surface circulation over the shelf confines the metals concentration mainly along the inner shelf and determines their transport patterns: under southeastward currents, Cd, Co, Cu, Ni, and Pb are transported toward the Mediterranean Sea; under northwestward countercurrents, Cd, Co, Cu, Fe, Ni, and Zn are transported toward the southern and, occasionally, the western Portuguese shelf; under variable currents, Ag, Cd, Co, Cu, Fe, Pb, and Zn tend to accumulate near their source. Considering that some of these metals have not been analysed before in this region (Ag, Mo, V), or that the spatial distribution of certain metals (Ag, Fe, Mo, Pb, V) has not been interpreted in terms of the ocean circulation, this work could be considered as a baseline study for future comparisons.

Responses of resident (DNA) and active (RNA) microbial communities in fluvial biofilms under different polluted scenarios

Pollution from human activities is a major threat to the ecological integrity of fluvial ecosystems. Microbial communities are the most abundant organisms in biofilms, and are key indicators of various pollutants. We investigated the effects some human stressors (nutrients and heavy metals) have on the structure and activity of microbial communities in seven sampling sites located in the Ter River basin (NE Spain). Water and biofilm samples were collected in order to characterize physicochemical and biofilm parameters. The 16S rRNA gene was analysed out from DNA and RNA extracts to obtain α and β diversity. Principal coordinates analyses (PCoA) of the operational taxonomic units (OTUs) in the resident microbial community revealed that nutrients and conductivity were the main driving forces behind the diversity and composition. The effects of mining have had mainly seen on the taxonomic composition of the active microbial community, but also at the OTUs level. Remarkably, metal-impacted communities were very active, which would indicate a close link with the stress faced, that is probably related to the stimulation of detoxification.

Comparison of HPLC Pigment Analysis and Microscopy in Phytoplankton Assessment in the Seomjin River Estuary, Korea

The distribution of microalgal species in estuaries shows marked gradients because of the mixing of marine and fresh water during tidal exchanges. To assess the spatio-temporal distribution of phytoplankton in the Seomjin River estuary (SRE), Korea, we investigated the seasonal phytoplankton communities along a salinity gradient in the estuary using both high performance liquid chromatography (HPLC) pigment analysis and light microscopy. Both types of analysis indicated that marine planktonic diatoms generally dominated at downstream sites having salinities >10, whereas freshwater species dominated at upstream sites having salinities <5. High levels of the pigments fucoxanthin and alloxanthin were found at upstream sites in the SRE in late spring. During summer, relatively high levels of the pigment peridinin were present in downstream areas of the SRE, and relatively high levels of diatoms occurred in upstream areas. In autumn, small Cryptomonas species were found in high abundance based on microscopic analysis, while CHEMTAX analysis of photosynthetic pigments showed relatively high concentrations of the diatom pigment fucoxanthin, implying the co-occurrence of a small unidentified phytoplankton. During winter, when the estuarine waters were well mixed, both the microscopic and CHEMTAX analyses showed that diatoms dominated at most stations. Seasonal and horizontal gradients in environmental conditions were clearly influenced by the salinity and nutrient loadings, especially the nitrate+nitrite and silicate concentrations. In particular, the ratio of photoprotective carotenoid pigments (PPCs) to photosynthetic carotenoid pigments (PSCs) was relatively low during all four seasons. This was predominately because of the high productivity of diatoms, which have a very low ratio of PPCs to PPSs. The SRE is a favorable habitat for diatoms because it is a high turbulence area having rapid water movement as a result of tidal changes. Overall, there was consistency in the data derived from the microscopy and chemotaxonomy analyses, suggesting that both methods are useful for analysis of the phytoplankton community structure in this complex estuarine and coastal water ecosystem.

Long-term changes of water quality in aquaculture-dominated lakes as revealed by sediment geochemical records in Lake Taibai (Eastern China)

The rapid development and exploitation of the Yangtze River basin in order to ensure human food security and increase living space in recent decades has resulted in significant potential for degradation of water quality in the river and in hundreds of lakes. Understanding how lake environments have evolved to their present state under a variety of external influences is crucial for evaluating their current status and anticipating future scenarios of environmental changes. However, the lakes along the middle reaches of the Yangtze River (MRY) are as yet little studied. Here, we described the long-term anthropogenic environmental transformations of a small lake (Lake Taibai) in the MRY area, based on a detailed quantitative geochemical analysis of the aliphatic hydrocarbons, nutrients (N and P), biogenic silica (BSi), and major and trace elements present in a dated sediment core retrieved from the lake. Our data revealed that levels of short-chain n-alkanes, αβ-hopanes and the trace elements arsenic (As) and cadmium (Cd) were all low for the entire record in sediments prior to ca. 1970, reflecting unpolluted natural state of the lake. Pronounced anthropogenic effects began to appear in sediments deposited in the subsequent years ca. 1970-1990, during which the levels of all these components were elevated, most likely driven by input of nitrogen (N) and phosphorus (P) containing chemical fertilizers, pesticides and diesel oil respectively. Since ca. 1990, changes of short-chain n-alkane levels in the sediment suggested the lake had undergone dramatic eutrophication in which existing anthropogenic stressors were exacerbated by technological advances that extended the use of chemical fertilizer into aquaculture. This pattern contrasted with an otherwise comparable lake in the lower Yangtze River basin, Lake Changdang, in which trace element and petroleum pollution were much more prominent due to dramatic urbanization and industrialization of the catchment.

Sediment quality assessment in the Guadalquivir River (SW, Spain) using caged Asian clams: A biomarker field approach

This study assesses the sediment quality of the Guadalquivir River watercourse between the Alcalá del Río dam and the city of Seville. The main objective of this work is to address sediment quality in the area using an integrative approach that links sediment contamination and toxicity using the Asiatic clam (Corbicula fluminea) under field conditions. This is the first study conducted in the area that use of a battery of biomarkers from exposure (GST, GPx) to adverse biological effect (DNA and histopathological damage) to identify the contamination adverse effects in a river area affected by a cocktail of different anthropogenic activities (urban, industrial, agricultural, etc.). The sediment quality characterized in the area shows a significant biological stress related to metal(loid)s at station located in Alcalá del Río in the river upper part of the studied area, being this stress toxic when approaching the city of Seville. The sediments located nearby this city showed toxicity by means of positive values in the biomarkers of effects measured in the caged clams and related to contaminants with an industrial and urban discharge origins. These results have shown the useful and strength of the biomarker approach used in this study that combines biomarker responses from exposure to effects and allows identifying the contamination adverse effects by means of using caging individuals of the Asian clam. It has been proved in the different experiments how once the exposure biomarkers reach a maximum value of their system the detoxification ability of the organisms is collapsed and then the biomarkers of effect are measured significantly in the different tissues. The use of field surveys using tolerant specie such as the Asian clam is recommendable to determine sediment quality under an integrative point of view as here reported.

Trace metal characterization and fluxes from the Guadiana, Tinto-Odiel and Guadalquivir estuaries to the Gulf of Cadiz

Metals transported into the coastal zone by the South Iberian rivers are key to understand the biogeochemical cycles and distribution of trace elements in the Gulf of Cadiz (GoC hereinafter) and the exchange with the Mediterranean Sea. Previous studies carried out in the 80s have suggested that metal enrichment in the Alboran Sea (Western Mediterranean) is related with fluvial inputs from acid mine drainage from the Tinto and Odiel rivers. The present study evaluates the contribution of dissolved trace metal concentrations (i.e. Cd, Co, Cu, Fe, Mo, Ni, Pb, V, Zn) from the three main rivers discharging into the GoC (i.e. Guadiana, Tinto-Odiel and Guadalquivir rivers). Our results show that the metal composition of water discharged from each river is impacted by the activities developed in the course of the rivers, which clearly influence the GoC coastal surface waters composition. Metal fluxes from the Guadalquivir river are quantitatively higher than those from the Tinto-Odiel (e.g. up to 73% and 19% higher for Ni and Cu, respectively). Although the metal concentrations spatial distributions in the GoC are dominated by the circulation pattern between the Atlantic and the Mediterranean Sea, the concentrations within the GoC continental shelf could be explained by a greater contribution from the Guadalquivir estuary (e.g. 80.5%, 54.6%, 56.5% and 56.6% for Ni, Cu, Mo, and V respectively).

Spatial and seasonal characteristics of dissolved heavy metals in the surface seawater of the Yellow River Estuary, China

Spatial-seasonal variations, sources and correlations with seawater physiochemical factors and the pollution indexes of dissolved heavy metals in the surface seawater of the Yellow River Estuary in China were investigated. The concentrations of copper (Cu), lead (Pb), zinc (Zn), cadmium (Cd), arsenic (As) and mercury (Hg) had ranges of 0.04-31.0 (11.6 ± 7.08), 0.42-13.3 (5.61 ± 3.55), 1.97-42.2 (14.9 ± 12.0), 0.10-1.90 (0.66 ± 0.37), 0.16-5.89 (2.59 ± 1.12) and 0.10-0.52 μg/L (0.24 ± 0.07), respectively, throughout the four seasons of the year. The concentrations of Cu, Pb, Zn and Cd were significantly high in winter relative to those in the other seasons, and the highest concentrations of Zn and Hg were detected in spring. The single contaminator factors of the elements are in the following order: Pb > Hg > Cu > Zn > Cd > As. The obtained degree of contamination showed that the Yellow River Estuary was highly polluted. The Cu and Zn concentrations were significantly correlated with temperature and suspended particulate matter (SPM). The Cd concentrations were significantly correlated with temperature, SPM, chemical oxygen demand (COD) and dissolved oxygen (DO). The As concentrations were significantly correlated with temperature, salinity, SPM and DO. The Hg concentrations were significantly correlated with salinity. We performed hierarchical cluster and principal component analyses to investigate the possible sources of heavy metals. Agricultural, industrial and atmospheric deposition resources were found to be possible sources of dissolved heavy metals in the studied area. Longshore currents, upwelling and the physicochemical parameters were possible influence factors of dissolved heavy metals spatial and seasonal distribution.

Hazard potential of widespread but hidden historic offshore heavy metal (Pb, Zn) contamination (Gulf of Cadiz, Spain)

Natural and human-induced seabed sediment disturbances affect wide areas of the global coastal ocean. These recurrent to chronic disturbances mobilize significant amounts of material, including substances that have the potential to significantly harm the environment once re-released. This very challenging issue is difficult to deal with if sub-surface contaminant concentrations are unknown. Based on the analysis of 11 new, up to 5-m long sediment cores taken offshore in the Gulf of Cadiz, the contamination history (using the trace elements lead and zinc) is well documented over major parts of the gulf. Ore mining and metal processing industries on the southwestern Iberian Peninsula started five thousand years ago and experienced a first peak during the Roman Period, which can be detected over the entire gulf. The Industrial Era added a massive, shelf-wide heavy metal excursion of unprecedented dimension. This metal contamination to the coastal ocean decreased in the 1990s and appears to be today limited to larger areas off the Tinto/Odiel and Guadiana River mouths. The unforeseen, significant finding of this study is that the gulf-wide, peak heavy metal concentration, stemming from the Industrial Era, is widely overlain by a modern sediment veneer just thick enough to cover the contaminant horizon, but thin enough to have this layer within the reach of natural or human-induced sediment mobilization events.

The impacts of seawater physicochemical parameters and sediment metal contents on trace metal concentrations in mussels-a chemometric approach

The concentrations of Al, Ba, Cd, Co, Cr, Cu, Fe, Li, Mn, Ni, Pb, Sr, Zn, and Hg were studied in Mytilus galloprovincialis collected from the coastal area of Montenegro. The impact of seawater temperature, salinity, dissolved oxygen, total organic carbon (TOC), and metal content in sediment samples on the metal contents in mussels collected from three locations in four different seasons was analyzed by a Pearson correlation coefficient (r), principal component analysis (PCA), and cluster analysis (CA). These analyses were used to discriminate groups of samples, elements, and seawater parameters, according to similarity of samples chemical composition in different seasons, as well as the impact of seawater parameters and surface sediment composition on the mussels' element concentrations. Synergistic interactions occurred between seawater TOC, Fe, and Al concentrations in mussels. Compared with other studies, which are usually performed under constant laboratory conditions where mussels undergo only one stress at a time, this study was performed in nature. The analyses showed the importance of considering simultaneously acting environmental parameters that make determining of separate impacts of each factor selected very difficult and complex.

Influence of human-induced pressures on dissolved and particulate metal concentrations in a South American estuary

Coastal areas are urbanized and industrialized environments, affected by dredging operations, discharges of untreated municipal wastewaters, and farming. Developing countries are in continuous growth and will deal, in a close future, with the highest rate of coastal transformation, posing serious risks for the ecological and environmental value of ecosystem assets. This research aims to study the dissolved and particulate Cr, Ni, Pb and Zn values within an argentinean estuarine environment which is currently under human-induced pressures. Concentrations of all the metals under analyses showed seasonal variability of both dissolved and particulate metals. An important outcome of this study was that dissolved Cr, Pb and Zn attained maximum values and overall increased concentrations with respect to previous records from the same area. Indeed, the highest concentrations were found during the dredging operations or in association with increases in the metal levels from wastewater discharges. The results also indicated that human activities contributed the least to the dissolved Ni concentrations. The particulate fraction of Cr, Ni and Zn showed an upward trend in the concentrations, particularly during the last two sampling dates, being also positively correlated between each other. Regarding their respective environmental quality standards, many samples achieved dissolved Cr and Zn concentrations above the maximum values recommended by international guidelines. Thus, this study highlights the possibility of stressors like dredging activities and municipal wastewaters to cause increases in the water column pollution levels.

Assessment of Douro and Ave River (Portugal) lower basin water quality focusing on physicochemical and trace element spatiotemporal changes

Water quality of Douro and Ave lower basin was evaluated regarding physicochemical parameters (pH, conductivity, dissolved oxygen and temperature), nutrient compounds (nitrates, nitrites, ammonium and orthophosphates), chlorophyll a and occurrence of trace elements (Li, Be, Al, Ti, V, Cr, Co, Ni, Cu, Zn, Se, Mo, Ag, Cd, Sb, Ba, Tl, Pb, Th and U). To study spatiotemporal variations and possible anthropogenic sources, estuarine samples were collected at nine sampling sites in Douro and five in Ave distributed along the estuaries at four sampling campaigns (spring, summer, fall and winter). According to the water quality standards for aquatic life and recreation, Douro and Ave river water quality was found out of safe limits regarding several parameters. Nitrate levels were systematically high (> 50 mg L^-1 in a significant number of samples) and mean levels of trace elements were higher than the established values of Canadian Environmental Quality Guidelines for aquatic life protection for Al, Cu, Se, Ag, Cd and Pb in Douro and Ave, and also Zn in Ave. Significant spatial differences were found in Ave river estuary for trace elements with a clear trend for higher values from upstream to downstream found. Seasonal differences were also observed particularly in Douro river estuary with higher levels in spring for most elements.

Using Non-supervised Artificial Neural Network for Determination of Anthropogenic Disturbance in a River System

The study of river water quality plays an important role in assessing the pollution status and health of the water bodies. Human-induced activities such as domestic activities, aquaculture, agriculture and industries have detrimentally affected the river water quality. Pinang River is one of the important rivers in Balik Pulau District that supplies freshwater for human consumption. A total of 442 physical and chemical parameters data of the Pinang River, Balik Pulau catchment were analysed to determine the sources of pollutants entering the river. Non-supervised artificial neural network (ANN) was employed to classify and cluster the river into upstream, middle-stream and downstream zones. The monitored data and non-supervised ANN analysis demonstrated that the source of nitrate was derived from the upper part of the Pinang River, Balik Pulau while the sources of nitrite, ammonia and ortho-phosphate are predominant at the middle-stream of the river system. Meanwhile, the sources of high total suspended solid and biological oxygen demand were concentrated at the downstream of the river.

Environmental impact of coal mining and coal seam gas production on surface water quality in the Sydney basin, Australia

The extraction of coal and coal seam gas (CSG) will generate produced water that, if not adequately treated, will pollute surface and groundwater systems. In Australia, the discharge of produced water from coal mining and related activities is regulated by the state environment agency through a pollution licence. This licence sets the discharge limits for a range of analytes to protect the environment into which the produced water is discharged. This study reports on the impact of produced water from coal mine activities located within or discharging into high conservation environments, such as National Parks, in the outer region of Sydney, Australia. The water samples upstream and downstream from the discharge points from six mines were taken, and 110 parameters were tested. The results were assessed against a water quality index (WQI) which accounts for pH, turbidity, dissolved oxygen, biochemical oxygen demand, total dissolved solids, total phosphorus, nitrate nitrogen and E .coli. The water quality assessment based on the trace metal contents against various national maximum admissible concentration (MAC) and their corresponding environmental impacts was also included in the study which also established a base value of water quality for further study. The study revealed that impacted water downstream of the mine discharge points contained higher metal content than the upstream reference locations. In many cases, the downstream water was above the Australia and New Zealand Environment Conservation Council and international water quality guidelines for freshwater stream. The major outliers to the guidelines were aluminium (Al), iron (Fe), manganese (Mn), nickel (Ni) and zinc (Zn). The WQI of surface water at and downstream of the discharge point was lower when compared to upstream or reference conditions in the majority of cases. Toxicology indices of metals present in industrial discharges were used as an additional tool to assess water quality, and the newly proposed environmental water quality index (EWQI) lead to better trend in the impact of coal and coal seam gas mining activities on surface water quality when compared to the upstream reference water samples. Metal content limits were based on the impact points assigned by the Agency for Toxic Substances and Disease Registry, USA. For environmental and health impact assessment, the approach used in this study can be applied as a model to provide a basis to assess the anthropogenic contribution from the industrial and mining activities on the environment.

Dissolved trace elements in a nitrogen-polluted river near to the Liaodong Bay in Northeast China

Dissolved trace element concentrations (Ba, Fe, Mn, Si, Sr, and Zn) were investigated in the Haicheng River near to the Liaodong Bay in Northeast China during 2010. Dissolved Ba, Fe, Mn, and Sr showed significant spatial variation, whereas dissolved Fe, Mn, and Zn displayed seasonal variations. Conditions such as water temperature, pH, and dissolved oxygen were found to have an important impact on redox reactions involving dissolved Ba, Fe, and Zn. Dissolved Fe and Mn concentrations were regulated by adsorption or desorption of Fe/Mn oxyhydroxides and the effects of organic carbon complexation on dissolved Ba and Sr were found to be significant. The sources of dissolved trace elements were found to be mainly from domestic sewage, industrial waste, agricultural surface runoff, and natural origin, with estimated seasonal and annual river fluxes established as important inputs of dissolved trace elements from the Haicheng River into the Liaodong Bay or Bohai Sea.

Typha latifolia (broadleaf cattail) as bioindicator of different types of pollution in aquatic ecosystems-application of self-organizing feature map (neural network)

The contents of Cd, Cu, Fe, Mn, Ni, Pb, and Zn in leaves of Typha latifolia (broadleaf cattail), water and bottom sediment from 72 study sites designated in different regions of Poland were determined using atomic absorption spectrometry. The aim of the study was to evaluate potential use of T. latifolia in biomonitoring of trace metal pollution. The self-organizing feature map (SOFM) identifying groups of sampling sites with similar concentrations of metals in cattail leaves was able to classify study sites according to similar use and potential sources of pollution. Maps prepared for water and bottom sediment showed corresponding groups of sampling sites which suggested similarity of samples features. High concentrations of Fe, Cd, Cu, and Ni were characteristic for industrial areas. Elevated Pb concentrations were noted in regions with intensive vehicle traffic, while high Mn and Zn contents were reported in leaves from the agricultural area. Manganese content in leaves of T. latifolia was high irrespectively of the concentrations in bottom sediments and water so cattail can be considered the leaf accumulator of Mn. Once trained, SOFMs can be applied in ecological investigations and could form a future basis for recognizing the type of pollution in aquatic environments by analyzing the concentrations of elements in T. latifolia.

Assessment of heavy metal enrichment in the offshore fine-grained sediments of the Caspian Sea

Sampling of the offshore seabed sediments of southwestern part of the Caspian Sea was carried out by gravity corer in order to study heavy metal concentration and the physicochemical factors controlling their distribution in the fine-grained fraction. The grain size distribution, amount, and type of clay minerals, total organic carbon (TOC) content, and Eh-pH of the sediments were determined. The average concentrations of the heavy metals in ppm are Mn (563), Cu (207.5), Sr (187), Zn (94), Pb (26.3), Ni (14.5), Co (11.5), Cd (2.56), and Ag (1.04) in their order of abundances. Co and Zn mostly indicate increase in silt-size fraction of the sediments suggesting their probable detrital provenance but the Mn, Ni, Cu, Sr, Pb, Cd, and Ag concentrations show a similar trend to distribution of the clay-size fraction. The concentrations of Mn, Co, and Cd increase with increase in the TOC content but the Cu, Pb, Ni, Ag, and Sr concentrations decrease with increase of the TOC content. The amounts of Zn, Cu, Sr, Pb, Cd, and Ag increase with increase in the CaCO3 content. The calculated enrichment factor indicates that the sediments are very strong to extremely enriched in Ag, significantly enriched in Cu and Cd, and depleted to mineral for Pb, Sr, Co, Ni, and Zn. Variations of the Cu, Sr, Cd, Ag, and Pb concentrations are similar to the clay and CaCO3 distributions.

Temporal variation and regional transfer of heavy metals in the Pearl (Zhujiang) River, China

Heavy metals are highly persistent in water and have a particular significance in ecotoxicology. Heavy metals loading from the Pearl River are likely to cause significant impacts on the environment in the South China Sea and the West Pacific. In this study, using monthly monitoring data from a water quality monitoring campaign during 2006-2012, the temporal variation and spatial transfer of six heavy metals (lead (Pb), copper (Cu), cadmium (Cd), zinc (Zn), arsenic (As), and mercury (Hg)) in the Pearl River were analyzed, and the heavy metal fluxes into the sea were calculated. During this period, the annual heavy metal loads discharged from the Pearl River into the South China Sea were 5.8 (Hg), 471.7 (Pb), 1524.6 (Cu), 3819.6 (Zn), 43.9 (Cd), and 621.9 (As) tons, respectively. The metal fluxes showed a seasonal variation with the maximum fluxes occurring from June to July. There is a close association between metal fluxes and runoff. The analysis of the heavy metal transfer from the upstream to the downstream revealed that the transfer from the upstream accounted for a major portion of the heavy metals in the Pearl River Delta. Therefore, earlier industry relocation efforts in the Pearl River watershed may have limited effect on the water quality improvement in surrounding areas. It is suggested that watershed-based pollution control measures focusing on wastewater discharge in both upstream and downstream areas should be developed and implemented in the future.

Bioaccumulation of macro- and trace elements by European frogbit (Hydrocharis morsus-ranae L.) in relation to environmental pollution

The aim of present study was to investigate the level of trace metals and macroelements in Hydrocharis morsus-ranae collected from regions differing in the degree and type of pollution. Concentrations of 17 macro- and microelements were determined in roots and shoots of European frogbit as well as in water and bottom sediments from 30 study sites. Plants differed in concentrations of elements and bioaccumulation capacity depending on the characteristics of dominant anthropogenic activities in the vicinity of the sampling site. Shoots of H. morsus-ranae growing in the vicinity of organic chemistry plants and automotive industry contained particularly high levels of Cd, Co, and S. Plants from area close to heat and power plant, former ferrochrome industry and new highway, were distinguished by the highest concentrations of Cr, Cu, and Pb. European frogbit from both these regions contained more Fe, Hg, Mn, Ni, and Zn than plants from agricultural and recreational areas. The concentrations of alkali metals and Co, Fe, and N in H. morsus-ranae were elevated in relation to the natural content in macrophytes irrespectively to their content in the environment. Based on the values of Bioaccumulation and Translocation Factors, European frogbit is an accumulator for Co, Cr, Cu, Fe, K, Mn, Ni, Pb, and Zn and a good candidate for phytoremediation of water polluted with Co, Cu, Hg, K, Mn, and Ni. The amount of Co and Mn removed from water and accumulated in the plant biomass during the vegetation season was considerably high.

Assessment of the environmental significance of nutrients and heavy metal pollution in the river network of Serbia

In this paper, the data for ten water quality variables collected during 2009 at 75 monitoring sites along the river network of Serbia are considered. The results are alarming because 48% of the studied sites were contaminated by Ni, Mn, Pb, As, and nutrients, which are key factors impairing the water quality of the rivers in Serbia. Special attention should be paid to Zn and Cu, listed in the priority toxic pollutants of US EPA for aquatic life protection. The employed Q-model cluster analysis grouped the data into three major pollution zones (low, moderate, and high). Most sites classified as "low pollution zones" (LP) were in the main rivers, whereas those classified as "moderate and high pollution zones" (MP and HP, respectively) were in the large and small tributaries/hydro-system. Principal component analysis/factor analysis (PCA/FA) showed that the dissolved metals and nutrients in the Serbian rivers varied depending on the river, the heterogeneity of the anthropogenic activities in the basins (influenced primarily by industrial wastewater, agricultural activities, and urban runoff pollution), and natural environmental variability, such as geological characteristics. In LP dominated non-point source pollution, such as agricultural and urban runoff, whereas mixed source pollution dominated in the MP and HP zones. These results provide information to be used for developing better pollution control strategies for the river network of Serbia.

Identifying spatial and seasonal patterns of river water quality in a semiarid irrigated agricultural Mediterranean basin

A detailed understanding of the study area is essential to achieve key information and optimize the monitoring, analysis, and evaluation of water quality of natural ecosystems that have been highly transformed into agricultural areas. Using classification techniques like the hierarchical cluster analysis (CA) and partial triadic analysis (PTA), we assessed the sources of water pollution and the seasonal influence of human activities in water composition in a river basin from northeastern Spain. The results suggested that a strong connection existed between water quality and the seasonality of the human activities. The CA showed the spatial relationship between water chemistry and the adjacent land uses. The PTA associated the analyzed variables to their pollutant source. Electrical conductivity (EC), Cl(-), SO4(2-)-S, Na(+), and Mg(2+) ions were related with agricultural sources, whereas NH4(+)-N, PT, and PO4(3-)-P were linked with urban polluted sites. Concentration of NO3(-)-N was associated with urban land use. Differences in water composition according to the irrigation intensity were also found during the irrigation season. The statistical tools used in this work, especially the PTA, allowed us to jointly analyze the spatial and seasonal components of water pollutant trends. We obtained a more comprehensive knowledge of water quality patterns in the study area, which will be essential when taking measures to minimize the effects of water pollution.

Water quality of the Luján river, a lowland watercourse near the metropolitan area of Buenos Aires (Argentina)

Luján river is a lowland watercourse which runs 130 km before flowing into the Río de la Plata Estuary, and receives a mixture of domestic and industrial wastewaters originating at its margins. In order to know the physicochemical profile of its surface water, 36 physical-chemical variables were analyzed in samples collected seasonally between 2004 and 2006 at three sampling stations. The results obtained through the principal component analysis (PCA) suggest that the variations in water quality are explained by natural components (soluble salts; metals), nonpoint inputs (nutrients), and anthropogenic (organic and bacterial) and industrial (toxic heavy metals) pollutants. The cases did not fit a clear spatial or seasonal pattern when plotted against the first two PCA axes. The three water quality indices calculated gave middle scores; Sampling station 1 gave a baseline for the comparison of the river's water quality along its course while Sampling station 3 (downriver) was the most degraded. A variety of pollution pulses reach and affect the watercourse downstream. Cities' sewage discharges into the river seem to be the major polluting factor, together with natural metals and other solutes loads that are present from the headwaters. The results may be useful for the development of local and regional mitigation and remediation programs regarding toxic and eutrophying loads in the upper basin of the river.

Characteristics and source identification of dissolved trace elements in the Jinshui River of the South Qinling Mts., China

Dissolved trace elements and physiochemical parameters were analyzed to investigate their physicochemical characteristics and identify their sources at 12 sampling sites of the Jinshui River in the South Qinling Mts., China from October 2006 to November 2008. The two-factor ANOVA indicated significant temporal variations of the dissolved Cu, Fe, Sr, Si, and V (p < 0.001 or p < 0.05). With the exception of Sr (p < 0.001), no significant spatial variations were found. Distributions and concentrations of the dissolved trace elements displayed that dissolved Cu, Fe, Sr, Si, V, and Cr were originated from chemical weathering and leaching from the soil and bedrock. Dissolved Cu, Fe, Sr, As, and Si were also from anthropogenic inputs (farming and domestic effluents). Correlation and regression analysis showed that the chemical and physical processes of dissolved Cu was influenced by water temperature and dissolved oxygen (DO) to some degree. Dissolved Fe and Sr were affected by colloid destabilization or sedimentary inputs. Concentrations of dissolved Si were slightly controlled by biological uptake. Principal component analysis confirmed that Fe, Sr, and V resulted from domestic effluents, agricultural runoff, and confluence, whereas As, Cu, and Si were from agricultural activities, and Cr and Zn through natural processes. The research results provide a reference for ecological restoration and protection of the river environment in the Qinling Mts., China.

A Methodological Approach for Spatiotemporally Analyzing Water-Polluting Effluents in Agricultural Landscapes Using Partial Triadic Analysis

Multivariate techniques for two-dimensional data matrices are normally used in water quality studies. However, if the temporal dimension is included in the analysis, other statistical techniques are recommended. In this study, partial triadic analysis was used to investigate the spatial and temporal variability in water quality variables sampled in a northeastern Spain river basin. The results highlight the spatiality of the physical and chemical properties of water at different sites along a river over 1 yr. Partial triadic analysis allowed us to clearly identify the presence of a stable spatial structure that was common to all sampling dates across the entire catchment. Variables such as electrical conductivity and Na and Cl ions were associated with agricultural sources, whereas total dissolved nitrogen, NH-N concentrations, and NO-N concentrations were linked to polluted urban sites; differences were observed between irrigated and nonirrigated periods. The concentration of NO-N was associated with both agricultural and urban land uses. Variables associated with urban and agricultural pollution sources were highly influenced by the seasonality of different activities conducted in the study area. In analyzing the impact of land use and fertilization management on water runoff and effluents, powerful statistical tools that can properly identify the causes of pollution in watersheds are important. Partial triadic analysis can efficiently summarize site-specific water chemistry patterns in an applied setting for land- and water-monitoring schemes at the landscape level. The method is recommended for land-use decision-making processes to reduce harmful environmental effects and promote sustainable watershed management.

Spatial monitoring of arsenic and heavy metals in the Almyros area, Central Greece. Statistical approach for assessing the sources of contamination

The purpose of this work was to provide information on As and heavy metals content in surface soils of the Almyros area, in Central Greece. A 3-year (2009-2011) research was conducted, in order to investigate the possible temporal variation of As and heavy metal levels. Each year, a number of 251 soil samples (753 totally number of samples) were collected from the area studied, using a Differential Global Positioning System (D.G.P.S.). Soil samples were analyzed for physicochemical parameters and for pseudo-total content of metals, after digestion with Aqua Regia. Thematic maps were created, with Geographic Information Systems (GIS) techniques, using geostatistical tools. The corresponding topographical diagrams covering 15,000 ha of the study area were digitized. The thematic maps and the geostatistical analysis tools were conducted with the use of ArcGIS and the extensions Geostatistical Analyst, Spatial Analyst, and 3D analyst. Factor analysis was conducted in order to assess the possible sources of the pollution. The levels of As and metals determined were lower than the maximum permitted, except for Cd, which content was, in some cases, higher than the critical limits for soils. No statistical differences were observed among the years of the study, although a trend of continuous increasing of their content was detected. Significant correlations between heavy metal fractions and soil physicochemical parameters were obtained and discussed.

The nutrient, total petroleum hydrocarbon and heavy metal contents in the seawater of Bohai Bay, China: Temporal-spatial variations, sources, pollution statuses, and ecological risks

Seawater samples collected between 2007 and 2012 were determined the concentrations of nutrient (DIN and DIP), total petroleum hydrocarbon (TPH), and six different heavy metals (As, Cu, Zn, Pb, Cd and Hg). The DIN, DIP, TPH, Pb, and Cd concentrations decreased from 2007 to 2009 or 2010 and increased after 2010. However, the Hg and Cu concentrations increased from 2007 to 2012. In contrast, the As and Zn gradually decreased during the study period. All of the pollutant concentrations gradually decreased from the shoreline to the offshore sites. PCA result showed that urban and port areas, agriculture, and atmospheric deposition were the main sources of pollutants in the bay. Although most of the pollutants were present at concentrations bellow the highest seawater quality standards in China, eutrophication was a risk in Bohai Bay. In addition, DIN was the main pollutant and was responsible for the eutrophication risk in Bohai Bay.

Identification of Surface Water Quality along the Coast of Sanya, South China Sea

Principal component analysis (PCA) and cluster analysis (CA) are utilized to identify the effects caused by human activities on water quality along the coast of Sanya, South China Sea. PCA and CA identify the seasonality of water quality (dry and wet seasons) and polluted status (polluted area). The seasonality of water quality is related to climate change and Southeast monsoons. Spatial pattern is mainly related to anthropogenic activities (especially land input of pollutions). PCA reveals the characteristics underlying the generation of coastal water quality. The temporal and spatial variation of the trophic status along the coast of Sanya is governed by hydrodynamics and human activities. The results provide a novel typological understanding of seasonal trophic status in a shallow, tropical, open marine bay.

Spectrophotometric characterization of dissolved organic matter in a rural watershed: the Madon River (N-E France)

In the last 20 years, increasing dissolved organic carbon (DOC) concentrations have been observed in several rivers and lakes in Europe. This increase has reduced the quality of the aquatic environment. In this study, UV-vis spectroscopy and synchronous fluorescence spectroscopy with a difference of 50 nm between the excitation and emission (SF50) were used to characterize the DOC in a rural river (Madon River). The specific absorbance index at 254 nm (SUVA254) which is related to the aromaticity of DOC was extracted from UV-vis spectra, whose maximum of the second derivative (occurring near 225 nm) is related to nitrates. SF50 spectra which are characterized by well-defined peaks indicated large spatial and temporal variations. Two methods were used to analyze and compare these spectra. The first method was based on the decomposition of the SF50 spectra into four Gauss functions: B1 (related to tryptophan-like fluorescence), B2 and B3 (related to humic substances), and B4 (related to chlorophyll-like substances). The second method was principal components analysis (PCA), which results yielded three principal components that accounted for 95% of the variance. Although PCA enables the consideration of the spectra without making assumptions regarding the number of fluorophores, the results from the decomposition in Gauss function were easier to interpret.

Environmental concentrations of metals in the catalan stretch of the ebro river, Spain: assessment of temporal trends

The aim of this study was to investigate the environmental impact and the human health risks associated with exposure to a number of metals before and after initiating the decontamination process in Flix dam (Catalonia, Spain). The concentrations of As, Cd, Cr, Cu, Mn, Hg, Ni, and Pb were determined in samples of drinking water, river water, and soils collected in the Catalan stretch of the Ebro River, Spain. The results were compared with those of previous surveys performed in the same zones. Human exposure to metals, as well as the associated carcinogenic and non-carcinogenic risks, was also estimated. In river and drinking waters, most analyzed metals showed increases, being significant that of Cr. The movements of polluted sludge in Flix dam could be the reason for the Cr levels found in the current survey. However, Hg was not detected in both drinking and river waters. Important differences on Mn levels were found, being higher those in river water than in drinking water. In turn, although soil concentrations of all analyzed metals showed a decreasing temporal trend, the reductions were only significant for Ni. The hazard quotient (HQ) of all elements was below the unity, considered the safe threshold. For carcinogenic risks, all values were found to be lower than 10(-5), which has been defined as the maximum recommended excess of cancer risk according to the Spanish Legislation. The only exception was the As exposure through soil and drinking water, which slightly exceeded this threshold. The current results indicate the need to perform a continuous assessment of metal levels not only in river waters, but also in drinking water in order to assure the harmlessness of the decontamination process for the health of the population living downriver (Ebro) the Flix dam.

Multi-way analysis for decadal pollution trends assessment: the Guadalquivir River estuary as a case study

Alongside history, human activities have contributed to the deployment of environmental quality. In particular, during the last decades the problem of water preservation has gained increasing attention. Statistical analysis is essential to analyze environmental data and to identify trends of pollutants over space and time. Usually applied techniques for data treatment are based on the organization of data in a two-way array, missing some shades on pollutants distribution. This fact supports the use of multi-way techniques, which allow the analysis of the results through different directions at the same time. For Three Modes Principal Components Analysis (3MPCA) a principal components analysis is conducted using three modes and a "core" matrix that allows assessing their interactions. In the case of environmental studies, it offers information about the spatial-temporal evolution of pollutants in a certain water body. The Guadalquivir River estuary has been used as a model system. It is a representative human influenced system, where different pollution inputs have been characterized. In this study, decadal evolution of pollutants has been discussed, to evaluate among others the effects of EU legislation on river water quality. The aim of this work is the establishment of the evolution, during the last decade, of nutrients and metals ultra-traces distribution in an estuary affected by anthropic activities. As examples, Pb and PO4(3-) show a trend to decrease their weight on water pollution, total suspended solids (TSS) behavior is related with massive rain events, and the rising of new technologies appears as a source of emerging pollutants as Co in urban-industrial areas.

Assessment and rationalization of water quality monitoring network: a multivariate statistical approach to the Kabbini River (India)

The establishment of an efficient surface water quality monitoring (WQM) network is a critical component in the assessment, restoration and protection of river water quality. A periodic evaluation of monitoring network is mandatory to ensure effective data collection and possible redesigning of existing network in a river catchment. In this study, the efficacy and appropriateness of existing water quality monitoring network in the Kabbini River basin of Kerala, India is presented. Significant multivariate statistical techniques like principal component analysis (PCA) and principal factor analysis (PFA) have been employed to evaluate the efficiency of the surface water quality monitoring network with monitoring stations as the evaluated variables for the interpretation of complex data matrix of the river basin. The main objective is to identify significant monitoring stations that must essentially be included in assessing annual and seasonal variations of river water quality. Moreover, the significance of seasonal redesign of the monitoring network was also investigated to capture valuable information on water quality from the network. Results identified few monitoring stations as insignificant in explaining the annual variance of the dataset. Moreover, the seasonal redesign of the monitoring network through a multivariate statistical framework was found to capture valuable information from the system, thus making the network more efficient. Cluster analysis (CA) classified the sampling sites into different groups based on similarity in water quality characteristics. The PCA/PFA identified significant latent factors standing for different pollution sources such as organic pollution, industrial pollution, diffuse pollution and faecal contamination. Thus, the present study illustrates that various multivariate statistical techniques can be effectively employed in sustainable management of water resources.

HIGHLIGHTS

The effectiveness of existing river water quality monitoring network is assessed. Significance of seasonal redesign of the monitoring network is demonstrated. Rationalization of water quality parameters is performed in a statistical framework.

Macro- and microelement distribution in organs of Glyceria maxima and biomonitoring applications

The content of nutrients (N, P, K, Ca and Mg) and of trace metals (Fe, Cu, Mn, Zn, Pb, Cd, Co and Ni) in water, bottom sediments and various organs of Glyceria maxima from 19 study sites selected in the Jeziorka River was determined. In general, the concentrations of nutrients recorded in the plant material decreased in the following order: leaf>root>rhizome>stem, while the concentrations of the trace elements showed the following accumulation scheme: root>rhizome>leaf>stem. The bioaccumulation and transfer factors for nutrients were significantly higher than for trace metals. G. maxima from agricultural fields was characterised by the highest P and K concentrations in leaves, and plants from forested land contained high Zn and Ni amounts. However, the manna grass from small localities showed high accumulation of Ca, Mg and Mn. Positive significant correlations between Fe, Cu, Zn, Cd, Co and Ni concentrations in water or sediments and their concentrations in plant indicate that G. maxima may be employed as a biomonitor of trace element contamination. Moreover, a high degree of similarity was noted between self-organizing feature map (SOFM)-grouped sites of comparable quantities of elements in the water and sediments and sites where G. maxima had a corresponding content of the same elements in its leaves. Therefore, SOFM could be recommended in analysing ecological conditions of the environment from the perspective of nutrients and trace element content in different plant species and their surroundings.

Spatial and seasonal characteristics of river water chemistry in the Taizi River in Northeast China

Anthropogenic activities have led to water quality deterioration in many parts of the world, especially in Northeast China. The current work investigated the spatiotemporal variations of water quality in the Taizi River by multivariate statistical analysis of data from the 67 sampling sites in the mainstream and major tributaries of the river during dry and rainy seasons. One-way analysis of variance indicated that the 20 measured variables (except pH, 5-day biological oxygen demand, permanganate index, and chloride, orthophosphate, and total phosphorus concentrations) showed significant seasonal (p ≤ 0.05) and spatial (p < 0.05) variations among the mainstream and major tributaries of the river. Hierarchical cluster analysis of data from the different seasons classified the mainstream and tributaries of the river into three clusters, namely, less, moderately, and highly polluted clusters. Factor analysis extracted five factors from data in the different seasons, which accounted for the high percentage of the total variance and reflected the integrated characteristics of water chemistry, organic pollution, phosphorous pollution, denitrification effect, and nitrogen pollution. The results indicate that river pollution in Northeast China was mainly from natural and/or anthropogenic sources, e.g., rainfall, domestic wastewater, agricultural runoff, and industrial discharge.

Application of termite nest for adsorption of Cr(VI)

This work proposes the use of tree termite nest as an adsorbent for the reduction/removal of Cr(VI) present in aqueous solution. In laboratory experiments, adsorption of Cr(VI) was sensitive to pH in the range investigated (2-5), with maximum adsorption capacity achieved at pH 2 (3.70 ± 0.04 mg g(-1), representing 93.2% removal of Cr). The termite nest was characterized by off-line pyrolysis GC/MS (py-GC/MS), infrared spectroscopy (FTIR), and electron paramagnetic resonance spectroscopy (EPR). Pyrolysis of the adsorbent produced a complex mixture of aromatic compounds, including the guaiacyl and syringilic derivatives that are characteristic of lignocellulosic materials. Infrared spectroscopy revealed deprotonation of the carboxylic acid group of the biomass with increasing pH, which was associated with a decrease in the capacity for adsorption of Cr(VI). The EPR g-factor for the termite nest samples varied between 2.0037 and 2.0038, indicating the presence of organic free radicals that were responsible for the redox reaction. A second line with g-factor values of 1.9790, only observed for the samples after contact with Cr(VI) solutions at different pH values, was assigned to Cr(III)-Cr(III) exchange coupled pairs, which explained the capacity of the adsorbent to retain a large portion of the Cr(III) ions produced after reduction of Cr(VI) to Cr(III). Fixed-bed column experiments showed that the termite nest had a maximum adsorption capacity of 18.60 mg Cr g(-1), an adsorption efficiency varying between 60.8 and 97.4%, and a desorption efficiency varying between 54.5 and 91.4%, for three successive cycles. The adsorbent presented excellent performance in the removal of chromium under acidic conditions, with the advantage that it could be regenerated and reused.

Assessment of semi-volatile organic compounds in drinking water sources in Jiangsu, China

Many xenobiotic compounds, especially organic pollutants in drinking water, can cause threats to human health and natural ecosystems. The ability to predict the level of pollutants and identify their source is crucial for the design of pollutant risk reduction plans. In this study, 25 semi-volatile organic compounds (SVOCs) were assessed at 16 monitoring sites of drinking water sources in Jiangsu, east China, to evaluate water quality conditions and source of pollutants. Four multivariate statistical techniques were used for this analysis. The correlation test indicated that 25 SVOCs parameters variables had a significant spatial variability (P<0.05). The results of correlation analysis, principal component analysis (PCA) and cluster analysis (CA) suggested that at least four sources, i.e., agricultural residual pesticides, industrial sewage, water transportation vehicles and miscellaneous sources, were responsible for the presence of SVOCs in the drinking water sites examined, accounting for 89.6% of the total variance in the dataset. The analysis of site similarity showed that 16 sites could be divided into high, moderate, and low pollutant level groups at (D(link)/D(max))×25<10, and each group had primary typical SVOCs. These results provide useful information for developing appropriate strategies for contaminants control in drinking water sources.

Metal concentrations and pathological responses of wild native fish exposed to sewage discharge in a Mediterranean river

The requirements of the Water Framework Directive suggest the need for further research to test and develop sensitive tools that will allow freshwater managers to detect impacts on fish communities. Diagnostic refinement often encompasses the use of lethal diagnostic tools that are incompatible with the conservation of native ichthyofauna. Here we determine the metal concentration and the pathological response of Squalius laietanus exposed to sewage discharges in the Ripoll river (north-eastern Spain), and compare these findings with our previous studies on Barbus meridionalis using lethal and non-lethal diagnostic tools. Metals concentrations (Zn, Cu, Pb, Hg, Fe, Cd and Ni) were determined in liver and muscle. A complete blood cell profile (haematocrit, haemoglobin, differential leukocyte count, erythrocytic nuclear abnormalities, erythrocytes in division and the development stage of erythrocytes) was used as a non-lethal diagnostic tool to determine early warning signs of disease in these two fish species. As the reference range for these haematological variables is lacking, liver histology, calculation of body condition (CF) and organosomatic indices (HSI and GSI) were employed to support the findings of the blood analyses. Compared to our previous results on B. meridionalis, S. laietanus appeared to have fewer pathological responses than B. meridionalis under the environmental conditions measured and the fish size range examined in this study. Both species showed a similar bioaccumulation pattern, but B. meridionalis stored high Hg and Cu concentrations in muscle and liver, respectively. Hg, Cu and Pb concentrations in fish tissues exceeded the thresholds of European and Spanish legislation. Our findings pinpoint the potential suitability of the blood variables determined in the health diagnoses of these species. Further research will be necessary to establish the natural variability of these and other haematological variables to convert haematology into a sensitive and useful non-lethal diagnostic tool in wild fish populations.