A spatial and seasonal assessment of river water chemistry across North West England

Leveraging the genetic diversity of trout in the rivers of the British Isles and northern France to understand the movements of sea trout (Salmo trutta L.) around the English Channel

Populations of anadromous brown trout, also known as sea trout, have suffered recent marked declines in abundance due to multiple factors, including climate change and human activities. While much is known about their freshwater phase, less is known about the species' marine feeding migrations. This situation is hindering the effective management and conservation of anadromous trout in the marine environment. Using a panel of 95 single nucleotide polymorphism markers we developed a genetic baseline, which demonstrated strong regional structuring of genetic diversity in trout populations around the English Channel and adjacent waters. Extensive baseline testing showed this structuring allowed high-confidence assignment of known-origin individuals to region of origin. This study presents new data on the movements of anadromous trout in the English Channel and southern North Sea. Assignment of anadromous trout sampled from 12 marine and estuarine localities highlighted contrasting results for these areas. The majority of these fisheries are composed predominately of stocks local to the sampling location. However, there were multiple cases of long-distance movements of anadromous trout, with several individuals originating from rivers in northeast England being caught in the English Channel and southern North Sea, in some cases more than 1000 km from their natal region. These results have implications for the management of sea trout in inshore waters around the English Channel and southern North Sea.

Evaluation of impact of land use and landscape metrics on surface water quality in the northeastern part along Lake Tanganyika, Africa

As the second deepest lake in Africa, Lake Tanganyika plays an important role in supplying fish protein for the catchment's residents and is irreplaceable in global biodiversity. However, the lake's water environment is threatened by socioeconomic development and rapid population growth along the lake. This study analyzed the spatial scale effects and seasonal dependence of land use types and landscape metrics on water quality in 16 sub-basins along northeastern Lake Tanganyika at different levels of urbanization. The results revealed that land use types had a higher influence on water quality in urban areas than that in rural areas; the explanatory variance in the urban area was 0.78-0.96, while it was 0.21-0.70 in the rural area. The explanatory ability of land use types on water quality was better at the buffer scale than at the sub-watershed scale, and the 500 m buffer scale had the highest explanatory ability in the urban area and rural area both in the rainy season and dry season, and artificial surface and arable land were the main contributing factors. And this phenomenon was more obvious in dry season than in rainy season. We identified that CONTAG was the key landscape metric in urban area and was positively correlated with nutrient variables, indicating that water quality degraded in less fragmented landscapes. The sub-watershed scale had the highest explained ability, while in rural area, the 1500 m buffer scale had the highest explained ability and IJI had the highest explanatory variance, which had a negative effect on water quality. Research on the relationship between land use and water quality would help assess the water quality in the unmonitored watershed as monitoring is expensive and time-consuming in low-income area. This knowledge would provide guideline to watershed managers and policymakers to prioritize the future land use development within Lake Tanganyika basin.

Combined Multivariate Statistical Techniques and Water Quality Index (WQI) to Evaluate Spatial Variation in Water Quality

In present study, Water Quality Index (WQI) has been assessed of the Rawal Lake which is a major source of drinking water for people in the Federal Capital, Islamabad, and its adjacent city Rawalpindi in Pakistan. For this, the principal component analysis (PCA) and WQI were applied as an integrated approach to quantitatively explore difference based on spatial variation in 11 water quality parameters of the five major feeding tributaries of the Rawal Lake, Pakistan. The results of temperature in water, total dissolved solids, pH, electrical conductivity, chlorides and sulfates were well within the allowable World Health Organisation's (WHO) limits. However, the heavy metals like cadmium and lead were above permissible limits by the WHO in tributaries of Bari Imam and Rumli. Moreover, this has been proven by the Pearson correlation which suggested strong positive correlation (0.910*) between lead and cadmium. The results of present study were subjected to statistical analysis, i.e., PCA which gave three major factors contributing 96.5% of the total variance. For factor 1, pH, TDS, alkalinity, chlorides, sulfates and zinc have highest factor loading values (>0.60) and presented that these parameters were among the most significant parameters of first factor. As per the WQI results, the water was categorised in two major classes indicating that water of Bari Imam and Rumli is highly contaminated with heavy metals and totally unsuitable for drinking purposes. Based on the results of the present study, it is suggested to make heavy metals consideration as an integrated component in future planning for maintaining water quality of the Rawal Lake and its tributaries.

Systematic tracing of nitrate sources in a complex river catchment: An integrated approach using stable isotopes and hydrological models

Quantitative estimation for tracking the transport of various nitrate sources is required to effectively manage nitrate loading in complex river systems. In this study, we validated an integrated framework using field isotopic data (δ¹⁵N_NO3 and δ¹⁸O_NO3) of nitrates and hydrological modeling (hydrological simulation program FORTRAN; HSPF) to determine anthropogenic nitrate flux among different land-use types within a watershed. Nitrate isotopic compositions showed different ranges among four land-use types (4.9 to 15.5‰ for δ¹⁵N_NO3, -4.9 to 12.1‰ for δ¹⁸O_NO3), reflecting the different nitrate sources (sewage, synthetic fertilizer, effluent and soil) within watersheds. Based on the integration of HSPF modeling, we also found that total nitrate loads might be partially controlled by hydrological conditions such as water discharge (12,040.3-22,793.2 L/s) from upstream to downstream. Among the nitrate sources, the sewage transport showed unique enhancement near urban boundaries, along with an increase in total nitrate load (>193.5 NO₃-N g/s km²) in downstream areas. In addition, the isotopic- and model-based nitrate fluxes showed good correlation for urban sources (R²=0.73, p < 0.05) but poor correlations for agriculture-dominated land use (R²=0.13, p > 0.05), reflecting the potential influence of surface runoff and ground infiltration into the watershed. Consequently, this research provided useful information to establish nitrogen management policy controlling point and non-point nitrate source loads in various land-use types for the restoration of water quality and aquatic ecosystem in the complex river system. Considering the recent increase in human activities near aquatic environments, this framework would be effective for individually estimating the quantitative contributions of anthropogenic nitrate sources transported along river-coastal systems.

Combined Effect of Climate and Anthropopressure on River Water Quality

This study was a continuation of our investigation of the spatio-temporal variability of the Bzura River's water chemistry. Our research is of particular importance in the context of the recent ecological disaster on the Oder River and concerns the international problem of surface water contamination. The study area was a 120 km section of the Bzura River. We tested more measurement points and with a higher sampling frequency than those used in the national monitoring of river water quality. During two hydrological years, 360 water samples were collected. The selected parameters: electrical conductivity, temperature, dissolved oxygen, dissolved organic carbon, nitrates, phosphates, bicarbonates, chlorides, sodium, potassium, calcium, and magnesium were determined. Numerous results exceeded the Polish threshold limits. Spatio-temporal variability and water quality were assessed using principal component analysis (PCA), cluster analysis (CA), and water quality index (WQI) approaches. Many point sources of pollution related to urbanization, agriculture, and industry were detected. Moreover, due to the changing climatic conditions, a significant difference between temporal variability in both years was observed. Our results indicated that it is necessary to increase the number of measurement stations for surface water monitoring; it will allow for a faster detection of the threat.

Isotopic and hydrogeochemical tracking of dissolved nutrient dynamics in the Brahmaputra River System: A source delineation perspective

The Brahmaputra river system (BRS) produces the largest discharge in India, supplying water to more than 62 million inhabitants. The present study aims to quantify the environmental elements that affect the spatio-temporal variation of nutrients in the Brahmaputra river system (BRS). The association of physico-chemical characteristics of floodplain sediments with the distribution pattern of P during wet and dry periods in different depths were also studied. The seasonal variation suggest that the average dissolved inorganic nitrogen and dissolve inorganic phosphorus are found higher in monsoon while the average dissolve silica were higher in post-monsoon. The spatial variation of dissolve inorganic phosphate and nitrate concentration suggests both the nutrient are higher in upstream sites. The DiS concentrations tended to be higher in downstream. In 70% of the sampled tributaries, the average molar ratio for dissolved inorganic nitrogen/dissolved inorganic phosphorous (DIN/DIP) was greater than 16:1, which indicates phosphate limited biological productivity. In contrast, an average molar ratio of dissolved inorganic silica/DIN (DSi/DIN) of 3.8 ± 3.0 favoured diatom growth in those tributaries where DSi/DIN molar ratio was lower than 1, indicating eutrophication. The BRS transported 24.7, 5.93, and 312 × 10⁴ tons/year^-1 of DIN, PO₄-P and SiO₂-Si, respectively. The depth-wise variation of P-fraction during monsoon suggests that the authigenic phosphorus was most abundant followed by Fe-bound, exchangeable, detrital and organic. In the post-monsoon, Fe-bound P was found at a higher concentration followed by authigenic phosphorus. High nutrient concentrations with more δ¹⁸O depleted water implied precipitation being the major source of nutrients in the BRS.

Response of water quality to land use in hydrologic response unit and riparian buffer along the Dan River, China

Land uses determine water quality within riparian environments to a certain extent and directly affect human health via drinking water. The main objective of this paper is to investigate the influences of land use, both in hydrologic response units (HRUs) and 200-m-wide buffer areas, on surface water quality. The variations and interrelationships between water physicochemical properties and land uses were assessed for better management of water environment. Nitrogen was the dominant nutrient and was significantly correlated with other water quality parameters. In the HRUs and buffer areas, the dominant landscape was grassland and farmland, respectively. Total organic carbon (TOC) and dissolved oxygen (DO) had negative correlation with land use factors; nitrate nitrogen, total nitrogen, total phosphorus, electrical conductivity, and temperature, in contrast, were positively correlated with them. Industrial and residential land was the critical land use for the aquatic environment in the Dan River, indicating that point pollution should receive more attention. Vegetation area had strong regression relationships with TOC and DO. Furthermore, more specific types of land use (subcategory classification) had a greater role in water quality. The land use in buffers can act on the water body more directly and effectively.

Global variation in freshwater physico-chemistry and its influence on chemical toxicity in aquatic wildlife

Chemical pollution is one of the major threats to global freshwater biodiversity and will be exacerbated through changes in temperature and rainfall patterns, acid-base chemistry, and reduced freshwater availability due to climate change. In this review we show how physico-chemical features of natural fresh waters, including pH, temperature, oxygen, carbon dioxide, divalent cations, anions, carbonate alkalinity, salinity and dissolved organic matter, can affect the environmental risk to aquatic wildlife of pollutant chemicals. We evidence how these features of freshwater physico-chemistry directly and/or indirectly affect the solubility, speciation, bioavailability and uptake of chemicals [including via alterations in the trans-epithelial electric potential (TEP) across the gills or skin] as well as the internal physiology/biochemistry of the organisms, and hence ultimately toxicity. We also show how toxicity can vary with species and ontogeny. We use a new database of global freshwater chemistry (GLORICH) to demonstrate the huge variability (often >1000-fold) for these physico-chemical variables in natural fresh waters, and hence their importance to ecotoxicology. We emphasise that a better understanding of chemical toxicity and more accurate environmental risk assessment requires greater consideration of the natural water physico-chemistry in which the organisms we seek to protect live.

Linking water environmental factors and the local watershed landscape to the chlorophyll a concentration in reservoir bays

The frequency of harmful algal blooms caused by eutrophication is increasing globally, posing serious threats to human health and economic development. Reservoir bays, affected by water environment and local watershed landscape, are more prone to eutrophication and algal blooms. The chlorophyll a (Chl a) concentration is an important indicator for the degree of eutrophication and algal bloom. Exploring the complex relationships between water environment and landscape background, and Chl a concentration in the reservoir bays are crucial for ensuring high-quality drinking water from reservoirs. In this study, we monitored Chl a concentrations of 66 bays in Danjiangkou Reservoir and the related water quality parameters (e.g., water temperature, turbidity, nutrients) in waterbodies of these reservoir bays in the storage and discharge periods from 2015 to 2018. Partial least squares-structural equation modeling (PLS-SEM) was used to quantify the relationship between water environmental factors and watershed landscapes, and Chl a concentrations in reservoir bays. The results showed that mean Chl a concentration was higher in storage period than that in discharge period. Two optimal PLS-SEMs explained 66.8% and 53.6% of Chl a concentration variation in the storage and discharge periods, respectively. The net effect of water chemistry on Chl a concentration was more pronounced during the discharge period (total effect = 0.61, 37% of the total effect on Chl a), while the net effect of land-use composition on Chl a concentration was more significant during the storage period (total effect = 0.57, 30% of the total effect on Chl a). The landscape pattern had significant indirect effects on Chl a concentration, especially during the discharge period (indirect effect = -0.31, 19% of the total effect on Chl a). Our results provide valuable information for managers to make rational decisions, thereby contributing to the prevention of eutrophication and algal blooms in reservoir bays.

Invertebrate turnover along gradients of anthropogenic salinisation in rivers of two German regions

Rising salinity in freshwater ecosystems can affect community composition. Previous studies mainly focused on changes in freshwater communities along gradients of absolute levels of electrical conductivity (EC). However, both geogenic and anthropogenic drivers contribute to the EC level and taxa may regionally be adapted to geogenic EC levels. Therefore, we examined the turnover in freshwater invertebrates along gradients of anthropogenic EC change in two regions of Germany. The anthropogenic change of EC was estimated as the difference between the measured EC and the modeled background EC driven by geochemical and climate variables. Turnover in freshwater invertebrates (β-diversity) was estimated using the Jaccard index (JI). We found that invertebrate turnover between EC gradient categories is generally greater than 47%, with a maximum of approximately 70% in sites with a more than 0.4 mS cm^-1 change compared to the baseline (i.e. no difference between predicted and measured EC). The invertebrates Amphinemura sp., Anomalopterygella chauviniana and Leuctra sp. were reliable indicators of low EC change, whereas Potamopyrgus antipodarum indicated sites with the highest EC change. Variability within categories of EC change was slightly lower than within categories of absolute EC. Elevated nutrient concentrations that are often linked to land use may have contributed to the observed change of the invertebrate richness and can exacerbate effects of EC on communities in water. Overall, our study suggests that the change in EC, quantified as the difference between measured EC and modeled background EC, can be used to examine the response of invertebrate communities to increasing anthropogenic salinity concentrations in rivers. However, due to the strong correlation between EC change and observed EC in our study regions, the response to these two variables was very similar. Further studies in areas where EC change and observed EC are less correlated are required. In addition, such studies should consider the change in specific ions.

Review of the distribution and detection methods of heavy metals in the environment

Heavy metals can be enriched in living organisms and seriously endanger human health and the ecological environment, which has evolved into a significant global environmental problem. Based on summarizing the spatial distribution of heavy metals in the environment, this review introduces heavy metal detection technologies such as inductively coupled plasma mass spectrometry/atomic emission spectrometry, atomic absorption spectrometry, atomic fluorescence spectrometry, and laser-induced breakdown spectrometry. It summarizes their respective advantages, characteristics, and applicability. Besides, atmospheric pressure discharge plasma as a potential heavy metal detection technology is also introduced and discussed in this review. The current research mainly focuses on improving the analytical performance and optimizing the practical application. Furthermore, this review not only summarizes the advantages of atmospheric pressure discharge plasma in the field of element analysis but also summarizes the principal scientific and technical problems to be solved urgently.

Effect of local watershed landscapes on the nitrogen and phosphorus concentrations in the waterbodies of reservoir bays

Reservoir bays, which are affected by the reservoir and watershed characteristics, are the initial and most sensitive areas in the evolution process of reservoir water quality. However, the relationship between the watershed characteristics and nitrogen and phosphorus concentrations in reservoir bays is poorly understood. We selected 66 bays from the Danjiangkou Reservoir and sampled twice per year (storage and discharge periods) from 2015 to 2018 to monitor the total nitrogen (TN) and total phosphorus (TP) concentration in the waterbodies of the reservoir bays. Four types of watershed characteristic indices (topographic variables, soil variables, land-use composition, and landscape patterns) around these bays were obtained. We quantified the relationship between the TN and TP concentrations and watershed characteristics in the waterbodies of the reservoir bays using partial least squares regression (PLSR). The results showed that the mean concentrations of TN and TP in the storage period (TN:1.69 mg·L^-1, TP:0.088 mg·L^-1) were higher than those in the discharge period (TN:1.22 mg·L^-1, TP:0.063 mg·L^-1). The optimal PLSR models explained 67.9% and 82.5% of the TN concentration variability, and 65.4% and 67.2% of the TP concentration variability during the storage and discharge period, respectively. Based on the variable importance in the projection (VIP) values, soil erodibility had significant effects on the TN and TP concentrations. The key factors affecting the TN concentration were the slope gradient, basin relief, topographic wetness index, forest and agricultural land use, whereas the factors controlling the TP concentration were the landscape shape index, edge density, Shannon's diversity index and grass land use, although the TP concentration was also controlled by the patch density and contagion during the storage period, and by mean patch size and largest patch index during the discharge period. This study provides critical insights into sustainable landscape planning and effective reservoir water quality management.

Impact of Human Activities and Natural Processes on the Seasonal Variability of River Water Quality in Two Watersheds in Lampung, Indonesia

This study identified seasonal water quality characteristics in two adjacent mountainous rivers (Sangharus and Sekampung Hulu Rivers) in Lampung, Indonesia and determined the impacts of fertilizer application on river chemistry as a result of social forestry management. In 2016, we measured water chemistry and conducted a farmers’ questionnaire survey to obtain information on fertilizer application. The water quality results indicated that several parameters, including nitrate (NO3) and phosphate (PO4), were significantly higher in the Sangharus River than in the Sekampung Hulu River. In addition, several parameters were influenced by dilution from high river flow in the rainy season. Some parameters were likely influenced by the weathering of parent materials. By contrast, electrical conductivity (EC) and NO3 were higher in the rainy season, which was likely linked to the dominant timing of urea fertilizer application during this season. Despite the application of fertilizers in the watersheds, NO3 levels remained below the recommended standard. However, aluminum and iron concentrations were higher than the recommended level for drinking water, which was likely due to elevated soil erosion from improper land management. Therefore, we recommend that effective land management policies be implemented through the adoption of soil conservation practices for nutrient loss prevention.

Spatiotemporal variability of heavy metals and identification of potential source tracers in the surface water of the Lhasa River basin

The Lhasa River basin is the economic and population center of Tibet and has abundant resources. Due to its harsh weather condition, high elevation, and inconvenient accessibility, few studies have focused on heavy metal distributions in this region. In the present study, to investigate the dissolved trace metal pollution and its controlling factors, 57 water samples from the Lhasa River and its tributaries were collected during three water flow regimes in 2016. The data on the dissolved fraction revealed that the Lhasa River basin appeared to have no to low pollution levels. However, the Lhasa River water showed alkaline characteristics which may affect the presence of heavy metal elements in a dissolved fraction. The concentration of heavy metal elements in colloidal or particulate matter therefore needs attention. Multivariate analyses were performed to determine the significant relationship between the data and to identify controlling factors for dissolved heavy metals in the study area. The results suggested that Mn, Cd, Cu, and Zn originated from a natural geological background, whereas Pb originated from mining drainage and As was influenced by geothermal flows. The concentration of dissolved heavy metals in the Meldromarchu tributary was greatly affected by the mining drainage water, while that in the Tölungchu tributary was greatly influenced by the geothermal water sources. This paper provides the first comprehensive analysis of dissolved heavy metal pollution characteristics and the controlling factors of pollution during the three different water flow regimes of the Lhasa River basin.

Predicting current and future background ion concentrations in German surface water under climate change

Salinization of surface waters is a global environmental issue that can pose a regional risk to freshwater organisms, potentially leading to high environmental and economic costs. Global environmental change including climate and land use change can increase the transport of ions into surface waters. We fit both multiple linear regression (LR) and random forest (RF) models on a large spatial dataset to predict Ca²⁺ (266 sites), Mg²⁺ (266 sites), and [Formula: see text] (357 sites) ion concentrations as well as electrical conductivity (EC-a proxy for total dissolved solids with 410 sites) in German running water bodies. Predictions in both types of models were driven by the major factors controlling salinity including geologic and soil properties, climate, vegetation and topography. The predictive power of the two types of models was very similar, with RF explaining 71-76% of the spatial variation in ion concentrations and LR explaining 70-75% of the variance. Mean squared errors for predictions were all smaller than 0.06. The factors most strongly associated with stream ion concentrations varied among models but rock chemistry and climate were the most dominant. The RF model was subsequently used to forecast the changes in EC that were likely to occur for the period of 2070 to 2100 in response to just climate change-i.e. no additional effects of other anthropogenic activities. The future forecasting shows approximately 10% and 15% increases in mean EC for representative concentration pathways 2.6 and 8.5 (RCP2.6 and RCP8.5) scenarios, respectively.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.

Land use affects total dissolved nitrogen and nitrate concentrations in tropical montane streams in Kenya

African tropical montane forests are facing fast and dynamic changes in land use. However, the impacts of these changes on stream water quality are understudied. This paper aims at assessing the effect of land use and physical catchment characteristics on stream water concentrations of dissolved organic carbon (DOC), total dissolved nitrogen (TDN), nitrate (NO₃-N) and dissolved organic nitrogen (DON) in the Mau Forest, the largest tropical montane forest in Kenya. We conducted five synoptic stream water sampling campaigns at the outlets of 13-16 catchments dominated by either natural forest, smallholder agriculture or commercial tea and tree plantations. Our data show a strong effect of land use on TDN and NO₃-N, with highest concentrations in stream water of catchments dominated by tea plantations (1.80±0.50 and 1.62±0.60mgNl^-1, respectively), and lowest values in forested catchments (0.55±0.15 and 0.30±0.08mgNl^-1, respectively). NO₃-N concentration increased with stream temperature and specific discharge, but decreased with increasing catchment area. DOC concentrations increased with catchment area and precipitation and decreased with specific discharge, drainage density and topographic wetness index. Precipitation and specific discharge were also strong predictors for DON concentrations, with an additional small positive effect of tree cover. In summary, land use affects TDN and NO₃-N concentrations in stream water in the Mau Forest region in Kenya, while DOC and DON were more related to hydrologic regimes and catchment properties. The importance of land use for NO₃-N and TDN concentrations emphasizes the risk of increased nitrogen export along hydrological pathways caused by intensified land use and conversion of land to agricultural uses, which might result in deterioration of drinking water quality and eutrophication in surface water in tropical Africa.

Effects of land use types on dissolved trace metal concentrations in the Le'an River Basin, China

Using land use types in multiple spatial scales (entire basin, buffer zones, and slopes) as well as statistical and spatial analysis, relationships between land use types and concentrations of dissolved trace metals were determined in the Le'an River Basin, China. The result showed that farmland and urban land were determined as the source of the pollutants, while forestland and grassland were identified as the sink of the pollutants. The temporal differences of relationships between land use types and concentrations of dissolved trace metals mainly due to the discrepancy of rainfall characteristics. Land use type close to river was a better indicator for the effectiveness of concentrations of trace metals, especially at scale of 0-200 m. Forestland and grassland on lower slopes greatly affected the water quality, and the former had no significant or weak influences on higher slopes. Urban land had the greater positive correlations with concentrations of dissolved trace metals on higher slopes, which are mainly due to frequent mining activity. Further analysis suggested that the buffer zones with low slope needed to be seriously taken into consideration for effective land use management in similar basin.

Unravelling organic matter and nutrient biogeochemistry in groundwater-fed rivers under baseflow conditions: Uncertainty in in situ high-frequency analysis

In agricultural catchments, diffuse nutrient fluxes (mainly nitrogen N and phosphorus P), are observed to pollute receiving waters and cause eutrophication. Organic matter (OM) is important in mediating biogeochemical processes in freshwaters. Time series of the variation in nutrient and OM loads give insights into flux processes and their impact on biogeochemistry but are costly to maintain and challenging to analyse for elements that are highly reactive in the environment. We evaluated the capacity of the automated monitoring to capture typically low baseflow concentrations of the reactive forms of nutrients and OM: total reactive phosphorus (TRP), nitrate nitrogen (NO₃-N) and tryptophan-like fluorescence (TLF). We compared the performance of in situ monitoring (wet chemistry analyser, UV-vis and fluorescence sensors) and automated grab sampling without instantaneous analysis using autosamplers. We found that automatic grab sampling shows storage transformations for TRP and TLF and do not reproduce the diurnal concentration pattern captured by the in situ analysers. The in situ TRP and fluorescence analysers respond to temperature variation and the relationship is concentration-dependent. Accurate detection of low P concentrations is particularly challenging due to large errors associated with both the in situ and autosampler measurements. Aquatic systems can be very sensitive to even low concentrations of P typical of baseflow conditions. Understanding transformations and measurement variability in reactive forms of nutrients and OM associated with in situ analysis is of great importance for understanding in-stream biogeochemical functioning and establishing robust monitoring protocols.

Orthophosphate-P in the nutrient impacted River Taw and its catchment (SW England) between 1990 and 2013

Excess dissolved phosphorus (as orthophosphate-P) contributes to reduced river water quality within Europe and elsewhere. This study reports results from analysis of a 23 year (1990-2013) water quality dataset for orthophosphate-P in the rural Taw catchment (SW England). Orthophosphate-P and river flow relationships and temporal variations in orthophosphate-P concentrations indicate the significant contribution of sewage (across the catchment) and industrial effluent (upper R. Taw) to orthophosphate-P concentrations (up to 96%), particularly during the low flow summer months when maximum algal growth occurs. In contrast, concentrations of orthophosphate-P from diffuse sources within the catchment were more important (>80%) at highest river flows. The results from a 3 end-member mixing model incorporating effluent, groundwater and diffuse orthophosphate-P source terms suggested that sewage and/or industrial effluent contributes ≥50% of the orthophosphate-P load for 27-48% of the time across the catchment. The Water Framework Directive (WFD) Phase 2 standards for reactive phosphorus, introduced in 2015, showed the R. Taw to be generally classified as Poor to Moderate Ecological Status, with a Good Status occurring more frequently in the tributary rivers. Failure to achieve Good Ecological Status occurred even though, since the early-2000s, riverine orthophosphate-P concentrations have decreased (although the mechanism(s) responsible for this could not be identified). For the first time it has been demonstrated that sewage and industrial effluent sources of alkalinity to the river can give erroneous boundary concentrations of orthophosphate-P for WFD Ecological Status classification, the extent of which is dependent on the proportion of effluent alkalinity present. This is likely to be a European - wide issue which should be examined in more detail.

Effects of land-use patterns on in-stream nitrogen in a highly-polluted river basin in Northeast China

This study investigated the effects of land-use patterns on nitrogen pollution in the Haicheng River basin in Northeast China during 2010 by conducting statistical and spatial analyses and by analyzing the isotopic composition of nitrate. Correlation and stepwise regressions indicated that land-use types and landscape metrics were correlated well with most river nitrogen variables and significantly predicted them during different sampling seasons. Built-up land use and shape metrics dominated in predicting nitrogen variables over seasons. According to the isotopic compositions of river nitrate in different zones, the nitrogen sources of the river principally originated from synthetic fertilizer, domestic sewage/manure, soil organic matter, and atmospheric deposition. Isotope mixing models indicated that source contributions of river nitrogen significantly varied from forested headwaters to densely populated towns of the river basin. Domestic sewage/manure was a major contributor to river nitrogen with the proportions of 76.4 ± 6.0% and 62.8 ± 2.1% in residence and farmland-residence zones, respectively. This research suggested that regulating built-up land uses and reducing discharges of domestic sewage and industrial wastewater would be effective methods for river nitrogen control.

A critical re-evaluation of controls on spatial and seasonal variations in nitrate concentrations in river waters throughout the River Derwent catchment in North Yorkshire, UK

Since mean nitrate concentration along single river channels increases significantly with percent arable land use upstream of sampling points and autumn/early winter flushes in nitrate concentration are widespread, it is generally concluded that farmers contribute most of the nitrate. For the River Derwent in North Yorkshire, the correlation between nitrate concentration and percent arable land use is much poorer when tributary data are included in the equation, because of greater variations in dilution by water draining upland areas and in other N input sources. For the whole river system therefore, percent upland moorland/rough grazing land cover is an appreciably better predictor than percent arable land use for nitrate concentration. Upland land use encompasses the higher precipitation and runoff in such areas, and the subsequent greater dilution downstream of both arable land runoff and effluent from treatment works, as well as an inverse correlation to percent arable land use. This is strongly supported by the observation that, for the Derwent, Meteorological Office rainfall data alone proved even better than percent moorland rough grazing for predicting nitrate concentration. The dilution effect is therefore substantial but highly seasonal; lower runoff and dilution in summer offset the lower leaching losses from arable land, and higher dilution and runoff in winter offset greater nitrate leaching losses from arable soils. Because of this, coupled to improved efficiency of nitrogen fertilizer use, seasonality trends in nitrate concentrations that were pronounced a decade ago now have all but disappeared in the catchment.

Land use/land cover water quality nexus: quantifying anthropogenic influences on surface water quality

Anthropogenic forces widely influence the composition, configuration, and trend of land use and land cover (LULC) changes with potential implications for surface water quality. These changes have the likelihood of generating non-point source pollution with additional environmental implications for terrestrial and aquatic ecosystems. Monitoring the scope and trajectory of LULC change is pivotal for region-wide planning, tracking the sustainability of natural resources, and meeting the information needs of policy makers. A good comprehension of the dynamics of anthropogenic drivers (proximate and underlying) that influence such changes in LULC is important because any potential adverse change in LULC that may be inimical to sustainable water quality might be addressed at the anthropogenic driver level rather than the LULC change stage. Using a dense time stack of Landsat-5 Thematic Mapper images, a hydrologic water quality and socio-geospatial modeling framework, this study quantifies the role of anthropogenic drivers of LULC change on total suspended solids and total phosphorus concentrations in the Lower Chippewa River Watershed, Wisconsin, at three time steps-1990, 2000, and 2010. Results of the study demonstrated that proximate drivers of LULC change accounted for between 32 and 59% of the concentration and spatial distribution of total suspended solids, while the extent of phosphorus impairment attributed to the proximate drivers ranged between 31 and 42%.

The contribution of household chemicals to environmental discharges via effluents: combining chemical and behavioural data

Increased concentrations and loads of soluble, bioavailable forms of phosphorus (P) are a major cause of eutrophication in streams, rivers and lakes in many countries around the world. To implement P control measures, it is essential to identify P sources and their relative load contributions. A proportion of P loading generated from household wastewaters is derived from detergents yet the P compositions of the range of domestic detergents and their usage is poorly understood. To quantify P loads from household detergents, we analysed a large range of detergents and cleaning products commonly available in the UK and Europe, comparing regular and eco-labelled products. Chemical data were coupled with survey results on typical household detergents preferences and usage (n = 95 households). We also determined whether the major and trace element signatures of these household detergents could potentially be used as anthropogenic tracers in watercourses. The greatest P concentrations were found for regular dishwasher detergents (43-131 mg P/g detergent) whilst the range of P in eco-labelled dishwasher detergents was much lower (0.7-9.1 mg P/g detergent). Other household cleaning groups contained relatively smaller P concentrations. Considering the survey results, detergents' total P loading generated from one household using either regular or eco labelled products, was 0.414 and 0.021 kg P/year, respectively. Given a household occupancy of 2.7, the P load from all detergent use combined was 0.154 kg P/person/year of which the dishwasher contribution was 0.147 kg P/person/year. In terms of elemental signatures, (DWD) dishwasher detergents were significantly (P-value <0.001) different from other household cleaning products in their As, Na, TP, Si, Sr, SRP, Ti, Zn and Zr signatures. Na, P and B were all positively correlated with each other, indicating their potential use as a tracer suite for septic tank effluent in combination with other indices. We conclude that forthcoming legislation for reducing P contents in domestic laundry detergents will not address the dominant environmental P load from DWD and studies such as this are important in promoting and allowing scenarios of benefits from future legislation for DWD.

A neighborhood statistics model for predicting stream pathogen indicator levels

Because elevated levels of water-borne Escherichia coli in streams are a leading cause of water quality impairments in the U.S., water-quality managers need tools for predicting aqueous E. coli levels. Presently, E. coli levels may be predicted using complex mechanistic models that have a high degree of unchecked uncertainty or simpler statistical models. To assess spatio-temporal patterns of instream E. coli levels, herein we measured E. coli, a pathogen indicator, at 16 sites (at four different times) within the Squaw Creek watershed, Iowa, and subsequently, the Markov Random Field model was exploited to develop a neighborhood statistics model for predicting instream E. coli levels. Two observed covariates, local water temperature (degrees Celsius) and mean cross-sectional depth (meters), were used as inputs to the model. Predictions of E. coli levels in the water column were compared with independent observational data collected from 16 in-stream locations. The results revealed that spatio-temporal averages of predicted and observed E. coli levels were extremely close. Approximately 66 % of individual predicted E. coli concentrations were within a factor of 2 of the observed values. In only one event, the difference between prediction and observation was beyond one order of magnitude. The mean of all predicted values at 16 locations was approximately 1 % higher than the mean of the observed values. The approach presented here will be useful while assessing instream contaminations such as pathogen/pathogen indicator levels at the watershed scale.

Spatial assessment of water quality in the vicinity of Lake Alice National Wildlife Refuge, Upper Devils Lake Basin, North Dakota

Runoff from concentrated animal feeding operations and croplands in the Upper Devils Lake Basin (Towner and Ramsey Counties), North Dakota, has the potential to impact the water quality and wildlife of the Lake Alice National Wildlife Refuge. Water samples were collected at eight locations upstream and downstream of the refuge, beginning in June 2007 through March 2011, to identify the spatial distribution of water quality parameters and assess the potential impacts from the upstream land use practices. Geographic Information Systems, statistical analysis, and regulatory standards were used to differentiate between sample locations, and identify potential impacts to water quality for the refuge based on 20 chemical constituents. Kruskal-Wallis analysis of variance (ANOVA) showed significant differences between sample locations based on boron, calcium, Escherichia coli, phosphorus, aluminum, manganese, and nickel. Hierarchical agglomerative cluster analysis of these constituents identified four distinct water quality groupings in the study area. Furthermore, this study found a significant positive correlation between the nutrient measures of nitrate-nitrite and total Kjeldahl nitrogen, and the percentage of concentrated animal feeding operation nutrient management areas using the non-parametric Spearman rho method. Significant correlations were also noted between total organic carbon and nearness to concentrated animal feeding operations. Finally, dissolved oxygen, pH, sulfate, E. coli, total phosphorus, nitrate-nitrite, and aluminum exceeded state of North Dakota and/or US Environmental Protection Agency water quality standards and/or guidelines. Elevated concentrations of phosphorus, nitrate-nitrite, and E. coli from upstream sources likely have the greatest potential impact on the Lake Alice Refuge.

Environmental management for dredging sediments - the requirement of developing nations

Scientific research has characterized the effects of dredging, an underwater excavation process for navigational purposes or material extraction, and has shown its association with a number of chemical, physical and biological impacts. Due to this, much environmental management has been applied in the dredging industry in order to manage its detrimental effects. However, developing nations may have different approaches towards their dredging environmental management to compare to their companions with higher economic strength. Moreover, scientific evidence to make an informed decision is often lacking, hence affecting the number of research executed at these nations, limiting their efforts to preserve the environment. This paper reviews the dredging environmental impacts and its two important factors, dredging technology and sediment characteristic, that determine the magnitude of impacts through literature review, and discusses the need for a more integrated dredging environmental management to be developed for developing nations.

Understanding nutrient biogeochemistry in agricultural catchments: the challenge of appropriate monitoring frequencies

We evaluate different frequencies of riverine nutrient concentration measurement to interpret diffuse pollution in agricultural catchments. We focus on three nutrient fractions, nitrate-nitrogen (NO3-N), total reactive phosphorus (TRP) and total phosphorus (TP) observed using conventional remote laboratory-based, low-frequency sampling and automated, in situ high-frequency monitoring. We demonstrate the value of low-frequency routine nutrient monitoring in providing long-term data on changes in surface water and groundwater nutrient concentrations. By contrast, automated high-frequency nutrient observations provide insight into the fine temporal structure of nutrient dynamics in response to a full spectrum of flow dynamics. We found good agreement between concurrent in situ and laboratory-based determinations for nitrate-nitrogen (Pearson's R = 0.93, p < 0.01). For phosphorus fractions: TP (R = 0.84, p < 0.01) and TRP (R = 0.79, p < 0.01) the relationships were poorer due to the underestimation of P fractions observed in situ and storage-related changes of grab samples. A detailed comparison between concurrent nutrient data obtained by the hourly in situ automated monitoring and weekly-to-fortnightly grab sampling reveals a significant information loss at the extreme range of nutrient concentration for low-frequency sampling.

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.

A critical re-evaluation of the prediction of alkalinity and base cation chemistry from BGS sediment composition data

The model of Begum et al. (2010) that predicts alkalinity and Ca and Mg concentrations in river water from available sediment composition data has been critically re-evaluated using an independent validation data set. The results support the hypothesis that readily available stream water sediment elemental composition data are useful for prediction of mean and minimum concentrations of alkalinity and Ca and Mg in river water throughout the River Derwent catchment in North Yorkshire without requiring land-use data inputs as stream water sediment composition reflects all aspects of the riparian zone soil system, including land-use. However, it was shown for alkalinity prediction that rainfall exerts a significant dilution effect and should be incorporated into the model in addition to flow path-weighted sediments Ca% and Mg%. The results also strongly suggest that in catchments with substantial rough moorland land-use neutralization of organic acids consumes alkalinity and this fact should be considered in any future development of the model.

Coupled effects of natural and anthropogenic controls on seasonal and spatial variations of river water quality during baseflow in a coastal watershed of Southeast China

Surface water samples of baseflow were collected from 20 headwater sub-watersheds which were classified into three types of watersheds (natural, urban and agricultural) in the flood, dry and transition seasons during three consecutive years (2010–2012) within a coastal watershed of Southeast China. Integrating spatial statistics with multivariate statistical techniques, river water quality variations and their interactions with natural and anthropogenic controls were examined to identify the causal factors and underlying mechanisms governing spatiotemporal patterns of water quality. Anthropogenic input related to industrial effluents and domestic wastewater, agricultural activities associated with the precipitation-induced surface runoff, and natural weathering process were identified as the potential important factors to drive the seasonal variations in stream water quality for the transition, flood and dry seasons, respectively. All water quality indicators except SRP had the highest mean concentrations in the dry and transition seasons. Anthropogenic activities and watershed characteristics led to the spatial variations in stream water quality in three types of watersheds. Concentrations of NH₄⁺-N, SRP, K⁺, COD_Mn, and Cl⁻ were generally highest in urban watersheds. NO₃^–N Concentration was generally highest in agricultural watersheds. Mg²⁺ concentration in natural watersheds was significantly higher than that in agricultural watersheds. Spatial autocorrelations analysis showed similar levels of water pollution between the neighboring sub-watersheds exhibited in the dry and transition seasons while non-point source pollution contributed to the significant variations in water quality between neighboring sub-watersheds. Spatial regression analysis showed anthropogenic controls played critical roles in variations of water quality in the JRW. Management implications were further discussed for water resource management. This research demonstrates that the coupled effects of natural and anthropogenic controls involved in watershed processes, contribute to the seasonal and spatial variation of headwater stream water quality in a coastal watershed with high spatial variability and intensive anthropogenic activities.

Water quality trends in New Zealand rivers: 1989-2009

Recent assessments of water quality in New Zealand have indicated declining trends, particularly in the 40 % of the country's area under pasture. The most comprehensive long-term and consistent water quality dataset is the National Rivers Water Quality Network (NRWQN). Since 1989, monthly samples have been collected at 77 NRWQN sites on 35 major river systems that, together, drain about 50 % of New Zealand's land area. Trend analysis of the NRWQN data shows increasing nutrient concentrations, particularly nitrogen (total nitrogen and nitrate), over 21 years (1989-2009). Total nitrogen and nitrate concentrations were increasing significantly over the first 11 years (1989-2000), but for the more recent 10-year period, only nitrate concentrations continued to increase sharply. Also, the increasing phosphorus trends over the first 11 years (1989-2000) levelled off over the later 10-year period (2000-2009). Conductivity has also increased over the 21 years (1989-2009). Visual clarity has increased over the full time period which may be the positive result of soil conservation measures and riparian fencing. NRWQN data shows that concentrations of nutrients increase, and visual clarity decreases (i.e. water quality declines), with increasing proportions of pastoral land in catchments. As such, the increasing nutrient trends may reflect increasing intensification of pastoral agriculture.

Contamination in a brazilian river: a risk of exposure to untreated effluents

Due to natural or anthropogenic activities, various chemical contaminants, such as toxic metals and organic compounds, enter water systems and can have multiple deleterious effects on many living organisms. The Todos os Santos River (TSR) in Brazil receives a high discharge of untreated effluents from various sources. The purpose of this study was to determine trace element concentrations in water samples from the TSR, evaluate the toxicological effects of these elements by using the (onion) test, and verify the physical-chemical parameters to establish the risk of exposure related to the contaminated river. The samples were taken in 2011 at six selected points (two upstream of an urban area, two in the urban area, and two downstream of the urban area) with physical-chemical parameters evaluated. The concentrations of Al (21.63-1688.84 μg L), P (38.59-1760.87 μg L), and Fe (478.9-8296.3 μg L) were above the maximum levels permitted under Brazilian law (and the World Health Organization); little dissolved O was observed. Based on the test, genotoxic and mutagenic effects may occur in the river and could be due to anthropogenic increases in metal content. These important results have serious implications for the ecosystem as well as the health of the people who use the water.

Water Quality of River Kosi and Rajera System at Rampur (India): Impact Assessment

River Kosi, an important tributary of river Ramganga, is one of the important rivers of Uttaranchal and Uttar Pradesh After traveling for about 100 kms in lower Himalayas with higher velocity, it emerges at Ramnagar in Indo-Gangetic plains. Here, the major portion of city sewage is discharged into it. Then, it flows through the famous rice belt area of Kashipur, where a number of polluting industries discharge their highly polluted effluents into it. To determine the extent of pollution in downstream district Rampur, a study was conducted. The aim of this study was to evaluate the effect of dilution caused by the merger of river Rajera with Kosi River. For this samples, were collected from three stations and analyzed for various parameters for the period of one year. The study revealed higher levels of industrial pollution as compared to domestic pollution. It also shows the alleviating effects of dilution caused by the merger of river Rajera.

A Monte Carlo approach to the inverse problem of diffuse pollution risk in agricultural catchments

The hydrological and biogeochemical processes that operate in catchments influence the ecological quality of freshwater systems through delivery of fine sediment, nutrients and organic matter. Most models that seek to characterise the delivery of diffuse pollutants from land to water are reductionist. The multitude of processes that are parameterised in such models to ensure generic applicability make them complex and difficult to test on available data. Here, we outline an alternative--data-driven--inverse approach. We apply SCIMAP, a parsimonious risk based model that has an explicit treatment of hydrological connectivity. We take a bayesian approach to the inverse problem of determining the risk that must be assigned to different land uses in a catchment in order to explain the spatial patterns of measured in-stream nutrient concentrations. We apply the model to identify the key sources of nitrogen (N) and phosphorus (P) diffuse pollution risk in eleven UK catchments covering a range of landscapes. The model results show that: 1) some land use generates a consistently high or low risk of diffuse nutrient pollution; but 2) the risks associated with different land uses vary both between catchments and between nutrients; and 3) that the dominant sources of P and N risk in the catchment are often a function of the spatial configuration of land uses. Taken on a case-by-case basis, this type of inverse approach may be used to help prioritise the focus of interventions to reduce diffuse pollution risk for freshwater ecosystems.

Effects of land cover, topography, and built structure on seasonal water quality at multiple spatial scales

The relationship among land cover, topography, built structure and stream water quality in the Portland Metro region of Oregon and Clark County, Washington areas, USA, is analyzed using ordinary least squares (OLS) and geographically weighted (GWR) multiple regression models. Two scales of analysis, a sectional watershed and a buffer, offered a local and a global investigation of the sources of stream pollutants. Model accuracy, measured by R(2) values, fluctuated according to the scale, season, and regression method used. While most wet season water quality parameters are associated with urban land covers, most dry season water quality parameters are related topographic features such as elevation and slope. GWR models, which take into consideration local relations of spatial autocorrelation, had stronger results than OLS regression models. In the multiple regression models, sectioned watershed results were consistently better than the sectioned buffer results, except for dry season pH and stream temperature parameters. This suggests that while riparian land cover does have an effect on water quality, a wider contributing area needs to be included in order to account for distant sources of pollutants.

Long term change of nutrient concentrations of rivers discharging in European seas

Cases of severe eutrophication are still observed in European surface waters even though tough regulation has been in place since the beginning of the 1990s to control nutrient losses and inputs in the environment. The purpose of this paper is to evaluate the evolution since 1991 of the quality of the water entering European seas in terms of the concentration of major nutrients (nitrogen and phosphorus), and to analyze the effectiveness of implemented national/international measures and EU legislation in reducing water nutrient pollution. Despite the reduction in large portions of the European territory of agricultural nutrient applications and nutrient point source emissions, the impact on water quality is limited. It is shown using two large river basins that this lack of response for nitrogen, and nitrate in particular, between the reduction of the nitrogen surplus and the recovery of water quality is partly explained by the lag time due to transfer of nitrates in the unsaturated and saturated zones and storage in the soils and aquifers. In order to monitor efficiently the impact of policy implementation on water quality, the Nitrates Directive and the Urban Waste Water Treatment Directive in particular, it is recommended to use long term permanent monitoring stations to be able to separate the impact of climate variability from that of policy implementation. It is also recommended to investigate and develop harmonized methodologies for estimating the lag time in order to come up with realistic estimates of response time of water bodies due to the implementation of measures.

The Ribble/Wyre observatory: major, minor and trace elements in rivers draining from rural headwaters to the heartlands of the NW England historic industrial base

Information on a new observatory study of the water quality of two major river basins in northwestern England (the Ribble and Wyre) is presented. It covers upland, intermediate and lowland environments of contrasting pollution history with sufficient detail to examine transitional gradients. The upland rivers drain acidic soils subjected to long-term acidic deposition. Nonetheless, the acidic runoff from the soils is largely neutralised by high alkalinity groundwaters, although the rivers retain, perhaps as colloids, elements such as Al and Fe that are mobilised under acid conditions. The lowland rivers are contaminated and have variable water quality due to variable urban/industrial point and diffuse inputs reflecting local and regional differences in historic and contemporary sources. For most determinands, pollutant concentrations are not a major cause for concern although phosphate levels remain high. Set against earlier studies for other regions, there may be a general decline in pollutant levels and this is most clearly observed for boron where effluent inputs have declined significantly due to reductions in household products that are flushed down the drain. High concentrations of sodium and chloride occurred briefly after a severe cold spell due to flushing of road salts. A major inventory for water quality within rural, urban, industrial and agricultural typologies is provided within data summary attachments for over 50 water quality determinands. Within the next year, the full dataset will be made available from the CEH website. This, with ongoing monitoring, represents a platform for water quality studies across a wide range of catchment typologies pertinent to environmental management of clean and impacted systems within the UK. The study provides a base of research "from source to sea" including extensions to the estuary and open sea for a semi-confined basin, the Irish Sea, where there are many issues of pollution inputs and contamination.