Distribution and enrichment evaluation of heavy metals in Mejillones Bay (23 degrees S), Northern Chile: geochemical and statistical approach

Vertical migration behavior simulation and prediction of Pb and Cd in co-contaminated soil around Pb-Zn smelting slag site

Heavy metal migration in soil poses a serious threat to the soil and groundwater. Understanding the migration pattern of heavy metals (HMs) under different factors could provide a more reasonable position for pollution evaluation and targetoriented treatment of soil heavy metal. In this study, the migration behavior of Pb and Cd in co-contaminated soil under different pH and ionic strength (NaCl concentration) was simulated using convective dispersion equation (CDE). We predicted the migration trends of Pb and Cd in soils after 5, 10, and 20 years via PHREEQC. The results showed that the migration time of Cd in the soil column experiment was about 60 days faster than that of Pb, and the migration trend was much steeper. The CDE was proved to describe the migration behavior of Pb and Cd (R2 > 0.75) in soil. The predicted results showed that Cd migrated to 15-20 cm of soil within 7 years and Pb stayed mainly in the top 0-6 cm of soil within 5 years as the duration of irrigation increased. Overall, our study is expected to provide new insight into the migration of heavy metal in soil ecosystems and guidance for reducing risk of heavy metal in the environment.

Benthic Foraminifera as Pollution Biomarkers: a Morphological Approach

Coastal areas are often intervened by anthropic activities, which increase the contamination of toxic agents such as heavy metals. This causes adverse morphological effects on benthic microorganisms, such as foraminifera. This group is one of the most susceptible to environmental deterioration, so they can be used as pollution biomarkers by identifying shell abnormalities. Therefore, 28 sediment samples from northern Chile were analyzed, calculating the Abnormality Index-FAI and its spatio-temporal distributions in benthic foraminifera, as well as the minimum and maximum abnormality percentages and their relationship with heavy metal concentrations, using a generalized non-linear model and a principal component analysis. The results indicated a proportion of abnormal shells within the ranges described for polluted areas conditions, revealing environmental stress conditions. This reflected a change in the environmental conditions in the most recent sediments of the bay. The highest FAI values were observed to the southwest of the bay, caused by the local current system. The species Bolivina seminuda, Buliminella elegantissima, and Epistominella exigua presented a greater number of deformities, allowing them to be used as contamination biomarkers. A significant correlation was found between Ti, Mn, Ni, Va, and Ba with decreased chamber sizes, wrong coiling, scars, and number of abnormality types. This suggests the effect of the particular geochemical conditions of the area on the heavy metals that cause toxic effects on foraminifera. These analyses are an efficient tool for identifying the effects of environmental stress before they occur in higher organisms, mitigating the environmental impact on marine biodiversity.

Multiple stable isotopes (C, N & S) provide evidence for fin whale (Balaenoptera physalus) trophic ecology and movements in the Humboldt Current System of northern Chile

Reflecting the intense coastal upwelling and high primary productivity characteristic of the Humboldt Current System (HCS), the northern coast of Chile supports a diverse and productive community of marine consumers, including worldwide important pelagic fisheries resources. Although marine mammals are relatively understudied in the region, recent studies have demonstrated that fin whale (Balaenoptera physalus) is the most frequently encountered whale species, and forages in these waters year-round. However, a current lack of information limits our understanding of whether fin whales actively feed and/or remain resident in these waters or whether whales are observed feeding as they migrate along this part of the Pacific. Here, we use stable isotope ratios of carbon, nitrogen and sulphur of fin whale skin samples collected in early summer 2020 (n = 18) and in late winter 2021 (n = 22) to examine evidence of temporal isotopic shifts that could provide information on potential migratory movements and to estimate likely consumption patterns of putative prey (i.e. zooplankton, krill, pelagic fishes and Pleuroncodes sp.). We also analysed prey items in fin whale faecal plumes (n = 8) collected during the study period. Stable isotope data showed significant differences in the isotopic values of fin whales from summer and winter. On average, summer individuals were depleted in 15N and 34S relative to those sampled during winter. Whales sampled in summer showed greater isotopic variance than winter individuals, with several showing values that were atypical for consumers from the HCS. During winter, fin whales showed far less inter-individual variation in stable isotope values, and all individuals had values indicative of prey consumption in the region. Analysis of both stable isotopes and faeces indicated that fin whales sighted off the Mejillones Peninsula fed primarily on krill (SIA median contribution = 32%; IRI = 65%) and, to a lesser extent, zooplankton (SIA zooplankton = 29%; IRI copepod = 33%). These are the first isotopic-based data regarding the trophic ecology of fin whales in the north of Chile. They provide evidence that fin whales are seasonally resident in the area, including individuals with values that likely originated outside the study area. The information presented here serves as a baseline for future work. It highlights that many aspects of the ecology of fin whales in the Humboldt Current and wider SE Pacific still need to be clarified.

Benthic foraminifera as bio-indicator of marine pollution in the southwestern Bay of Bengal, India

The benthic foraminiferal community is an excellent bio-indicator of pollution in coastal and marginal marine settings. Their abundance, diversity and its relationship with environmental parameters, viz. grain size, organic carbon (Corg) and trace metals concentration, from the surface sediment layer of the southwestern shelf of the Bay of Bengal, have been used to understand the marine pollution in this study. A total of 32 surface sediment samples were collected at various water depths.The samples were analysed for grain size distribution, organic matter (OM), foraminiferal and trace metals studies. Statistical analyses such as correlation matrix, PCA (Principal Component Analysis) and cluster analysis show that the foraminiferal species composition is significantly influenced by the organic carbon (Corg), Co, Pb, Zn, Cr, and Ni concentrations. The dominance of stress-tolerant species, viz. Ammonia beccarii, Ammonia tepida, Nonion faba, Bulimina marginata, Bolivina robusta, Elphidium craticulatum and Elphidium advenum, as well as less species diversity, demonstrates the elevated Corg and trace metal pollution in the marine environment.

Human-induced metals accumulation in sediments of an industrialized bay of northern Chile. An enrichment and ecological risk assessment based on preindustrial values

Environmental assessment in marine systems is difficult because most of the time their preindustrial characteristics are not available. Four sediment cores taken in Mejillones bay (northern Chile) were used to establish preindustrial metals concentrations, and to assess the environmental status of this industrialized zone. According to historical documents, the beginning of the industrial era start in 1850 CE. Considering this, the preindustrial concentration of some metals was established, by mean of a statistical approach. Most of the metals increase their concentration from the preindustrial to the industrial period. Environmental assessment showed an enrichment of Zr and Cr, a moderately polluted condition, and a low probability of toxic effect on the biological communities. The preindustrial values derived from sediment cores are a good tool to evaluate the environmental condition of Mejillones bay. However new information (backgrounds with a higher spatial representativity, toxicological threshold, and others) it is necessary to improve the environmental assessment of this environment.

Effects of sedimentary heavy metals on meiobenthic community in tropical estuaries along eastern Arabian Sea

The central west coast of India comprises the 720 km long coastline of Maharashtra state and houses widespread industrial zones along the eastern Arabian Sea. Sediments from seven industrial-dominated estuaries along the central west coast were studied for metal enrichment and benthic assemblages to determine sediment quality status and ecological effects in these areas. The suit of geochemical indices highlighted the contamination of sediment in the estuaries concerning heavy metals. Positive correlations of Hg with Co, Zn, Ni, Cr, and Pb indicated the source similarity and effect of anthropogenic activity. non-Metric Multidimensional Scaling (n-MDS) based on meiofaunal abundance showed a cleared separation of clusters through the gradient of heavy metal concentrations. The Canonical Correspondence Analysis (CCA) results with the Monte Carlo test signified those heavy metals influenced the meiobenthic community. Heavy metals (Cr, Ni, Zn, Cd, Pb, and Hg) were the main drivers shaping the meiofaunal community with a significant (p < 0.05) reduction in taxa richness, diversity, and evenness. Dominant meiofaunal assemblages evidence the tolerance of foraminiferans and nematodes. However, these taxa were affected by decreased abundance at impacted sites compared to other fauna. In conclusion, results demonstrated that impairment occurred in the meiofaunal community in most estuaries (except AB and KK).

Assessment of heavy metal pollution in marine sediments from southwest of Mallorca island, Spain

Anthropogenic activities in urban, agrarian, or industrial areas are the main cause of heavy metals in sediments worldwide. Since the 1960s, there have been submarine discharges through outfalls of poorly treated or untreated wastewater on the south coast of Mallorca island (Mediterranean Sea). In this study, the pollution of marine sediments is analyzed at a great number of points on the south of the seacoast. Heavy metal concentrations of As, Ba, Cd, Cr, Cu, Hg, Ni, Pb, Se, V, and Zn, total inorganic carbon (TIC), sulfur, mineralogy, and grain size were analyzed. The objective is to evaluate the concentrations of toxic substances and their spatial distribution and ranges that can negatively affect marine ecosystems and human health. In addition, the results obtained have been compared with standardized indices for marine sediments, and a regional index has been developed with the background values of heavy metals obtained in the sediments of the study area. To obtain consistent conclusions, concentrations of heavy metals were classified with the Igeo Index. The concentrations of heavy metals obtained show that a great number of samples exceeded the limits considered for uncontaminated sediments according to the index applied. Elements such as Hg, Ba, Pb, and Cu showed high concentrations close to the outfalls and lower concentrations in zones far from these points. To support the assessment, chemical processes such as dissolution or chemical precipitation have been studied. The results also show that marine sediments can be a good trap for chemical elements and a good proxy to analyze the impact of anthropogenic activities in areas heavily pressured by humans, and the risk to the environment and human health.

Hydrodynamically-driven distribution and remobilization of heavy metals in surface sediments around the coastal area of Shandong Peninsula, China

Heavy metals (HMs) are considered a major pollutant of the surface sediments of the continental shelf. However, there remains little in-depth research on their fate in the ocean, and particularly on their abundance in sediments and the water column and the underlying drivers. This study examined the concentrations of HMs (Cu, Zn, Cr, Pb, Cd, and As) in surface sediments and suspended particulate matter (SPM) around the coastal area of Shandong Peninsula, China. The division of the sedimentary environment and influencing factors were also analyzed using multivariate statistical analysis Fuzzy c-means (FCM) cluster and Non-Linear Mapping (NLM). The study attempted to understand the distribution and remobilization of HMs in the shallow marginal sea using multi-disciplinary approaches, including satellite remote sensing and numerical simulation. The results showed higher HMs in the surface sediments in Weihai Bay (Zone I) than in the junction of the Chengshantou Cap (Zone III) and north of Wei Bay (Zone II). In addition, the results suggested that Cu, Zn, Cr and Pb originated from natural weathering, with their spatial distributions in the three zones highly regulated by sediment grain size, total nitrogen (TN), and total carbon (TC). In contrast, Cd and As originated from anthropogenic contamination (e.g., industrial discharges and aquaculture) in Zone I. HMs (except As) were influenced by terrigenous total organic carbon (TOC) in Zone III. The results of this study suggest that the difference in sediment re-suspension intensity has an important influence on the distribution of HM concentrations in the north Yellow Sea. This study can act as a reference for understanding the fates and source-sink processes of HMs in offshore sediments. The coupling behaviors and microscopic suspension properties of HMs in surface sediments and SPM require further investigation.

Spatial co-occurrence patterns of benthic microbial assemblage in response to trace metals in the Atacama Desert Coastline

Taxonomic and functional microbial communities may respond differently to anthropogenic coastal impacts, but ecological quality monitoring assessments using environmental DNA and RNA (eDNA/eRNA) in response to pollution are poorly understood. In the present study, we investigated the utility of the co-occurrence network approach's to comprehensively explore both structure and potential functions of benthic marine microbial communities and their responses to Cu and Fe fractioning from two sediment deposition coastal zones of northern Chile via 16S rRNA gene metabarcoding. The results revealed substantial differences in the microbial communities, with the predominance of two distinct module hubs based on study zone. This indicates that habitat influences microbial co-occurrence networks. Indeed, the discriminant analysis allowed us to identify keystone taxa with significant differences in eDNA and eRNA comparison between sampled zones, revealing that Beggiatoaceae, Carnobacteriaceae, and Nitrosococcaceae were the primary representatives from Off Loa, whereas Enterobacteriaceae, Corynebacteriaceae, Latescibacteraceae, and Clostridiaceae were the families responsible for the observed changes in Mejillones Bay. The quantitative evidence from the multivariate analyses supports that the benthic microbial assemblages' features were linked to specific environments associated with Cu and Fe fractions, mainly in the Bay. Furthermore, the predicted functional microbial structure suggested that transporters and DNA repair allow the communities to respond to metals and endure the interacting variable environmental factors like dissolved oxygen, temperature, and salinity. Moreover, some active taxa recovered are associated with anthropogenic impact, potentially harboring antibiotic resistance and other threats in the coastal zone. Overall, the method of scoping eRNA in parallel with eDNA applied here has the capacity to significantly enhance the spatial and functional understanding of real-time microbial assemblages and, in turn, would have the potential to increase the acuity of biomonitoring programs key to responding to immediate management needs for the marine environment.

Trace element contamination status of surface marine sediments of Greece: an assessment based on two decades (2001-2021) of data

This study is a first attempt to assess the trace element contamination status in the surface sediments of the Hellenic Seas since the first environmental studies in the country commenced in the mid-1970s. All available trace element data from the last 20 years have been collected and assessed using sediment quality guidelines and application of single- and multielement pollution indices. Although Hellenic marine sediments initially appear as anthropogenically enriched in Cr and As, this enrichment is attributed to the natural background. Central Greece appears more polluted, followed by Northern Greece and lastly Southern Greece. The element pollution indices featured the influence of industrial activities such as mining, steel industry and chemical factories, shipyards, and secondarily the influence of port activities.

Benthic microbial diversity trends in response to heavy metals in an oxygen-deficient eutrophic bay of the Humboldt current system offshore the Atacama Desert

Mejillones Bay is a coastal ecosystem situated in an oxygen-deficient upwelling area impacted by mining activities in the coastal desert region of northern Chile, where conspicuous microbial life develops in the sediments. Herein, heavy metal (loid)s (HMs) such as Cu, Pb, As, Zn, Al, Fe, Cd, Mo, Ni and V as well as benthic microbial communities were studied using spectrometry and iTag-16 S rRNA sequencing. Samples were taken from two contrasting sedimentary localities in the Bay named Punta Rieles (PR) and Punta Chacaya (PC) within 10-50 m water-depth gradient. PR sediments were organic matter rich (21.1% of TOM at 50 m) and overlaid with low-oxygen waters (<0.06 ml O2/L bottom layer) compared with PC. In general, HMs like Al, Ni, Cd, As and Pb tended to increase in concentration with depth in PR, while the opposite pattern was observed in PC. In addition, PR presented a higher number of unique families (72) compared to PC (35). Among the top ten microbial families, Desulfobulbaceae (4.6% vs. 3.2%), Flavobacteriaceae (2.8% vs. 2.3%) and Anaerolineaceae (3.3% vs. 2.3%) dominated in PR, meanwhile Actinomarinales_Unclassified (8.1% vs. 4.2%) and Sandaracinaceae (4.4% vs. 2.0%) were more abundant in PC. Multivariate analyses confirmed that water depth-related variation was a good proxy for oxygen conditions and metal concentrations, explaining the structure of benthic microbial assemblages. Cd, Ni, As and Pb showed uniformly positive associations with communities that represented the keystone taxa in the co-occurrence network, including Anaerolineaceae, Thiotrichaceae, Desulfobulbaceae, Desulfarculaceae and Bacteroidales_unclassified communities. Collectively, these findings provide new insights for establishing the ecological interconnections of benthic microorganisms in response to metal contamination in a coastal upwelling environment.

Characteristics of Heavy Metals in Seawater and Sediments from Daya Bay (South China): Environmental Fates, Source Apportionment and Ecological Risks

In this study, the spatiotemporal distributions, potential sources, and ecological risks of Hg, Cr, and As in seawater, and Hg, As, Zn, Cd, Pb, and Cu in sediments from Daya Bay were investigated. The five-year average concentrations of Hg, Cr, and As in seawater were 0.020 μg/L, 0.79 μg/L, and 2.08 μg/L, respectively. The five-year average concentrations of Hg, As, Zn, Cd, Pb, and Cu in surface sediments were 0.04 mg/kg, 7.34 mg/kg, 63.81 mg/kg, 0.23 mg/kg, 25.60 mg/kg, and 11.78 mg/kg, respectively. Annual variations in Hg, Cr, and As in seawater exhibited different trends. HMs in sediments, such as As, Zn, Pb, and Cu, exhibited similar annual variations, whereas Hg and Cd exhibited different annual variations. The spatial distribution of metal species in seawater and sediments showed significant variability, and the concentrations decreased gradually from the coast to the open sea. The comprehensive potential ecological hazard index (RI) of HMs in sediments indicated a relatively high risk, especially for Hg and Cd contamination. The geoaccumulation indices (Igeo) of As, Zn, Pb, and Cu suggested that these metals did not pollute Daya Bay, whereas those of Cd and Hg indicated mild and moderate pollution. The environmental fates of HMs were discussed based on Pearson correlation analysis, revealing that concentrations of HMs were greatly affected by parameters, such as pH, salinity, dissolved oxygen (DO), and total organic carbon (TOC). Principal component and factor analyses indicated that Hg, Cr, As, and dissolved inorganic nitrogen (DIN) in water originated from similar sources, including domestic sewage and wastewater from fishing ports, runoffs, and outlets. For sediments, it was proposed that Cu, Zn, As, Pb, and TOC exhibited similar sources, including cage culture and waste discharge from outlets. Meanwhile, Hg and Cd originated from other point sources, such as a harbor. The study suggests that sustainable management and economic development be integrated to control pollutant emissions in Daya Bay.

Spatial distribution and potential ecological risk assessment of some trace elements in sediments and grey mangrove (Avicennia marina) along the Arabian Gulf coast, Saudi Arabia

To assess trace element concentrations (Zn, Cu, Pb, Cr, Cd and Ni) in the mangrove swamps along the Saudi coast of the Arabian Gulf, thirteen samples of surface sediment and leaves of grey mangrove, Avicennia marina were collected and analyzed. The detected trace element contents (μg g-1) in surface sediments were in the following descending order according to their mean values; Cr (49.18) > Zn (48.48) > Cu (43.06) > Pb (26.61) > Ni (22.88) > Cd (3.21). The results showed that the average concentrations of Cd and Pb exceeded their world average concentration of shale. The geo-accumulation, potential ecological risk and toxicity response indices demonstrated that trace elements have posed a considerable ecological risk, especially Cd. The inter-relationships between physico-chemical characters and trace elements suggests that grained particles of mud represent a noteworthy character in the distribution of trace elements compared to organic materials. Moreover, the results revealed that Zn was clearly bioaccumulated in leaf tissues A. marina. Dredging, landfilling, sewage effluents and oil pollution can be the paramount sources of pollution in the area under investigation.

210Pb dating to investigate the historical variations and identification of different sources of heavy metal pollution in sediments of the Pearl River Estuary, Southern China

In this study, we investigated the historical variation, source identification, and distribution of heavy metal pollution in sediments of the Pearl River Estuary (PRE) using ²¹⁰Pb dating. Our results suggest that the heavy metal concentrations were higher in the western part of the estuary. For all heavy metals, Cd was significantly enriched in the sediments. The Pearl River Delta (PRD) has experienced rapid economic development in the past 40 years, a decreasing trend in heavy metal fluxes after 2004 was identified, which suggests a reduction in heavy metal concentrations due to the removal of heavy polluting industries and the effective control of sewage discharge. A binary mixing model reveals that the contributions of anthropogenic Pb ranged from 45.4 to 64%. Based on lead isotopic ratios (^206/207Pb and ^208/206Pb), it was found that geologic materials and industrial pollution were the main sources of heavy metals in the PRE sediments.

Spatial monitoring of metals and As in coastal sediments of northern Chile: An evaluation of background values for the analysis of local environmental conditions

To assess environmental conditions along the coast of northern Chile, 457 sediment samples were collected between 22° S and 28° S in order to evaluate the Cu, Zn, Pb, Ni, V, Cd, As and Al content as well as its corresponding relationship to nearby anthropogenic activities. In general, the results of most metals showed that bays without industrial activity accumulate lower concentrations of contaminant elements in the sediments and thus mostly represent natural conditions. The highest Cu, Pb and V levels were measured in coastal zones were different industrial mining activities have been developed during the last decades. Results of different indices of environmental evaluation and ecological impact suggest that, metal content of sediments from pollution-free zones characterized by similar oceanographic and geological conditions to those under study, would be the most appropriate background level for assessing the anthropogenic impact on coastal areas of northern Chile.

Assessment of trace metal contamination of wetland sediments from eastern and western coastal region of India dominated with mangrove forest

Ecosystem and biodiversity of India's coastal areas dominated with mangrove forest have been threatened by growing anthropogenic activities. The present work aims to investigate the contamination of wetland sediments with trace elements and assess the sediment quality at different sampling locations in eastern and western costal region dominated with mangrove forest. The longitudinal profile of trace elements in sediments from different sampling locations analyzed by employing Energy Dispersive X-ray Fluorescence (EDXRF) spectrometer shows variations in distribution of elements like Al, Si, K, Ca, V, Cr, Mn, Fe, Ni, Cu, Zn and Pb. The enrichment factor (EF) and Geo-accumulation index (I_geo) values suggested depletion of clay minerals and enrichment of heavy metals like Cr, Cu Fe and Mn. Depending on the variations in Igeo values, the elements are put into I_geo Class 0 to 3 levels of contamination. Contamination factor (Cf) and pollution load index (PLI) suggested deterioration of sediments analyzed in the present study. Assessment of ecological risk potential of elements suggests that few elements (Cr and Cu) are moderately contaminated and may cause environmental stress on the exposed flora and fauna.

Bioavailability, mobility, and origination of metals in sediments from Anzali Wetland, Caspian Sea

We investigated the bioavailability, mobility, and origin of heavy metals present in sediments from the Anzali Wetland. Chemical speciation of the metals was performed according to the Tessier method. Results indicated that Cd and As showed the highest level of bioavailability, whereas Cr showed the lowest level. Cr, Co, and V were shown to have a terrestrial origin. The metal As was mostly found in the reducible fraction (F3), whereas other metals were highest in the residual phase. The levels of Co present in the oxidizable fraction (F4); Pb and Cd present in the carbonate fraction (F2); and the other metals present in the exchangeable fraction (F1) were found to be the lowest. On the basis of the Risk Assessment Code of metals, Cd at most stations, As and Ni at some stations, and Zn at one station revealed to have a moderate risk. Co and Pb were found to have a low risk at all stations. Considering Pollution Load Index, stations 2 and 3 were classified as moderately polluted and the remaining stations were unpolluted. As suggested by enrichment factor analysis, As was moderately enriched and other metals had a deficiency to minimal enrichment at all the stations.

Heavy metal assessment in surface sediments off Coromandel Coast of India: Implication on marine pollution

The present study investigates the distribution of heavy metals (Fe, Cd, Co, Cr, Cu, Ni, Zn and Pb) in the surface sediments along the Coromandel Coast of Bay of Bengal as an indicator of marine pollution. Pollution indices such as Contamination factor (CF), Enrichment factor (EF) and Geo-accumulation index (I) were performed to assess the spatial distribution and pollution status of the study area. The heavy metal concentration in the study area is closely associated with grain size and organic matter. Both geoaccumulation index and metal contamination factor indicate that the sediments are free from contamination with regards to the metals Cr and Ni, followed by uncontamination to moderate contamination of Co, Cu and Zn. However, sediments are found to be extremely polluted with respect to Cd and Pb. Factor analysis reveals that the accumulation of these heavy metals in the shelf sediments are due to anthropogenic inputs from the adjacent land area.

Heavy metal distribution and contamination status in the sedimentary environment of Cochin estuary

Heavy metals (Fe, Mn, Cr, Zn, Ni, Pb, Cu, Co and Cd) in the surface sediments of Cochin estuary, Southwest coast of India were analyzed to understand the spatio-temporal variation and contamination status via six sampling campaigns. Pollution indices like enrichment factor, geoaccumulation index and pollution load index inferred that the sediments of the northern arm of the estuary exhibited severe trace metal accumulation. Numerical sediment quality guidelines were applied to assess adverse biological effects of the trace metals, suggesting that occasional biological effect may occur due to Cr, Cu, Ni and Pb. Correlations between metals, organic carbon, silt and clay suggested that both fine grained sediment and organic matter were important carriers for these metals. Multivariate statistics indicated that the sources of Cu and Ni resulted primarily from natural weathering processes, whereas enriched levels of Cd, Cr, Zn and Pb were mainly attributed to anthropogenic activities.

Assessment of nutrient and heavy metal contamination in the seawater and sediment of Yalujiang Estuary

Yalujiang River is a famous border river between China and North Korea. In this study, 22 sample sites (seawater and sediments) were investigated to determine the concentrations of nutrients (dissolved inorganic nitrogen and soluble reactive phosphorus) and trace elements (Hg, As, Pb, Cu, Cd, Cr, and Zn) during the flood season (August). Generally, the concentration of nutrients were higher in the entrance of the estuary than that in the downstream region and the trophic index ranged from moderate to high production, indicating a potential eutrophication risk. With the exception of Cd, the mean concentrations of most metals attained the first level of seawater quality. Sediment pollution assessment was undertaken using contamination factor (CF) and geoaccumulation index (I_geo). The CF values of the seven trace elements were in the following order: Cd>Hg>Pb>As>Cu>Zn>Cr. Both CF and I_geo values indicated the elevated Cd and Hg concentrations in the region. Cluster analysis indicated that the sources of Cu, Cd, Cr, and Zn were mainly derived from copper mine and coastal industrial effluents, whereas Pb, Hg, and As were mainly from vehicle emissions and oil combustion. This study could provide a basis for the sustainable management of the marine ecosystem in this region.

Preliminary assessment of metal distribution in the surface sediments along the coastline of the southern Caspian Sea

In the present study, the concentrations of metals in sediments along the coastline of the southern Caspian Sea were investigated. For this purpose, sediments were collected from 13 sampling sites in the southern Caspian Sea. The samples were then analyzed by inductively coupled plasma-optical emission spectrometry. Results showed that compound oxides may be responsible for the distribution of metals in the sediments of the southern Caspian Sea. According to mean effects range-median quotient, 61.5% of the studied sites from the southern Caspian Sea had a 21% probability of metal toxicity. On the basis of the enrichment factor, all metals were in the category of deficiency to minimal enrichment. Pollution load index showed that the other sampling sites had no pollution.

Environmental and ecological risk of heavy metals in the marine sediment from Dakhla Bay, Morocco

Heavy metal assessment in Dakhla Bay (Atlantic coast) was carried out using different environmental and ecological indices. Heavy metal concentrations were measured using ICP-AES and were compared with consensus-based sediment quality guidelines. The distribution of heavy metal concentrations varies for the three groups: (i) lead distribution is dominated by its associations with copper and chromium. These elements have the same source, most probably related to anthropogenic activities. (ii) Nickel, zinc and cobalt are associated with aluminium and iron indicating their terrigenous origin (natural content), and (iii) cadmium concentration is related to upwelling currents. This paper systematically studied the distributions and pollution levels of heavy metals in sediment in the coastal areas in Dakhla Bay, which is of scientific significance, to discuss the changing rules and the affecting factors of the harmful heavy metals and can be adopted for reference to other coastal areas.

Geochemical speciation, bioavailability and source identification of selected metals in surface sediments of the Southern Caspian Sea

Geochemical speciation of As, Cd, Co, Cr, Cu, Ni, Pb, V and Zn were determined in the surface sediments of the southern Caspian Sea. A five-step sequential extraction technique was used to determine the chemical forms of metals. Mean concentrations (ppm) of heavy metals were (mean±S.D.) As: 9.94±1.71, Cd: 0.87±0.23, Co: 14.85±2.80, Cr: 72.29±19.48, Cu: 18.91±4.48, Ni: 32.87±5.25, Pb: 12.48±3.22, V: 86.07±20.71 and Zn: 66.85±10.11. Among the metals, Cu, As, Pb and Zn exhibited relatively higher mobility, while Cd, Co, Cr, Ni and V were found mainly in the residual fractions. Cu and As showed the highest percentages in the exchangeable phase while Co and Cr had the lowest percentages in the phase. The Risk Assessment Code (RAC) values indicated that As, Cu and V had medium risk at some sampling sites. According to pollution load index (PLI), sediments from some sampling sites were polluted.

Spatial distribution of soil cadmium and its influencing factors in peri-urban farmland: a case study in the Jingyang District, Sichuan, China

Semi-agricultural ecosystems in peri-urban areas are susceptible to contamination. The spatial distribution and influencing factors of such pollution are unclear and poorly constrained in many areas worldwide. Therefore, studying the problems of soil pollution in peri-urban areas is critical for environmental management and agricultural production. In this paper, with cadmium (Cd) as the target pollutant, the spatiotemporal variations of soil cadmium pollution and the relative importance of the affecting factors were analyzed at a peri-urban area from the Jingyang District, Sichuan, China. Statistical results showed that the farmland in the study area could be considered moderately soil Cd-polluted, under the dual influence of natural factors and human activity. In particular, the soil Cd concentration in Tianyuan and Bajiaojing exceeded 0.5 mg kg^-1, for intensive industrial enterprises are distributed in these areas. Correspondingly, the geoaccumulation index also showed that the contamination of Cd in this area was moderately polluted. Moreover, the ecological risk index was 80% in the study area, indicating that the soil Cd pollution potential risk was moderate to high. High geological background values (soil Cd = 0.29 mg kg^-1), river migration, industrial enterprises, and traffic significantly influenced soil Cd pollution, with natural geological factors playing greater roles. The significant horizontal-spatial effective distances away from Shiting River, Deyang-Aba Highway, and chemical plants were 200, 400, and 100 m, respectively. These results will be useful in guiding farmland cultivation and pollution remediation effectively in the peri-urban areas.

Metal contamination and its ecological risk assessment in the surface sediments of Anzali wetland, Caspian Sea

In this study, the accumulation of metals, including Al, Fe, Zn, V, Ni, Cu, Cr, Cd, Co, As, and Pb, in sediments of Anzali wetland in the southwest region of the Caspian Sea was investigated. For this purpose, the sediments were collected from 17 sampling sites in Anzali wetland, Caspian Sea. The samples were then analyzed using inductively coupled plasma-optical emission spectrometry (ICP-OES). Pearson correlation coefficient showed significant and positive correlation between concentration of all metals (except As and Cd). Furthermore, the results implied that Al and Fe are probably responsible for the transportation of heavy metals into the sediments of Anzali wetland. According to mean effects range-median quotient (mean ERM quotient), the sediments from Anzali wetland had a 21% probability of toxicity.

Geochemical speciation and ecological risk assessment of selected metals in the surface sediments of the northern Persian Gulf

The present study aimed to geochemical speciation of metals in the surface sediments of the northern Persian Gulf. Metal contents in the sediment were observed in the order: Al>Fe>Cr>Ni>V>Zn>Cu>Co>As>Pb>Cd. The results of sequential extraction procedure revealed that all metals were predominantly associated with the residual fraction. Among the metals, Cu and As exhibited higher bioavailability. The risk assessment code (RAC) indicated that Cu, As and Cd had medium environmental risk at some sampling sites. Based on enrichment factor (EF), Cd and As had moderate to significant enrichment.

Vertical and horizontal variation of elemental contamination in sediments of Hooghly Estuary, India

Hooghly Estuary along with the Sunderban mangroves forms one of the most diverse ecosystems in the world. We investigated the vertical and horizontal distribution of elements at nine sampling locations in this estuary for assessing the degree of elemental contamination. The elemental concentrations were analyzed by an Energy Dispersive X-ray Flurosence spectrometer (EDXRF). A higher enrichment factor (EF) value of trace elements (V, Cr, Mn, Fe, Ni, Cu and Zn) is evident considering all the sampling locations. Geo-accumulation index (Igeo) values of all the sampling locations and core depth reveals Cr and Cu are under Igeo Class I level of contamination. The value of the pollution load index (PLI) varies between 0.94-1.65 with maximum at Chemaguri and minimum at Haldi Estuary and Petuaghat. The overall variation in elemental concentration may be due to differential discharge pattern of storm water and agricultural run-off, industrial effluent and domestic sewage.

Distribution and contamination assessment of heavy metals in surface sediments of the Luanhe River Estuary, northwest of the Bohai Sea

33 surface sediment samples from the Luanhe River Estuary have been analyzed for heavy metals to evaluate the spatial distribution pattern and their potential ecological risk. Higher metal concentrations were found in the river mouth and southern areas where being covered by fine particulate matters. In comparison with the threshold effect level and the probable effect level, Cu, Pb, Cr, Ni, and As had occasionally adverse biological effects on the aquatic ecosystems. Both the enrichment factor and geoaccumulation index values show that all the regions have been weakly polluted by Pb, Hg, As, and Cd with an exception of being moderately to strongly polluted by Hg in the river mouth and southern areas. The sources of Zn, Ni, Cd, Hg, and Cr were mainly from the river input and coastal discharge, whereas Cu, Pb, and As were mainly derived from vehicle emissions, coal and oil combustion.

Ecological risk, source and preliminary assessment of metals in the surface sediments of Chabahar Bay, Oman Sea

In this study, concentrations of Aluminum (Al), Iron (Fe), Chromium (Cr), Copper (Cu), Nickel (Ni), Vanadium (V), Zinc (Zn), Arsenic (As), Cobalt (Co) and lead (Pb) in the surface sediments from Chabahar Bay were studied to assess the degree of heavy metal pollution as a consequence of natural and anthropogenic sources. Metal contents in the sediments were observed in the order of: Al>Fe>Cr>V>Ni>Zn>Cu>>As>Pb>Co. According to enrichment factor (EF), Arsenic was higher than 1.5 at some sites, indicating anthropogenic inputs. Contents of Ni, As and Cr in the some sampling sites were higher than sediment quality guideline implying adverse impacts of these metals. Based on potential ecological risk (PER), the Chabahar Bay had low ecological risk.

Mercury Enrichment in Sediments of the Coastal Area of Northern Latium, Italy

The purpose of this study was to evaluate the extent of the Hg geochemical anomaly arising in the Amiata and Tolfa complex to the coastal area of northern Latium and to examine the possible influence on this area by the Mignone River, and by the small coastal basins, which are characterized by both previous mining activities and decades of past industrial impact. The results confirm the extension of the anomaly of concentrations of Hg in the coastal area of northern Latium, with the northern sector influenced by the contributions of the Fiora and Mignone Rivers and the southern sector influenced by the contributions of minor basins. The results show high values of the Adverse Effect Index throughout the considered area and highlight the need for further investigation in order to assess the impact of human activities on the present and past values of Hg in marine sediments.

Assessment of bed sediment metal contamination in the Shadegan and Hawr Al Azim wetlands, Iran

The Shadegan and Hawr Al Azim wetlands are important natural resources in southwestern Iran, yet relatively little work has been done to assess ecosystem health of the wetlands. Bed sediment from both wetlands was sampled in individual months between October, 2011 and December, 2012 and analyzed for As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Pb, and Zn using inductively coupled plasma optical emission spectrometry (ICP-OES). The metals data were evaluated using a combination of sediment quality guidelines from the Ontario Ministry of Energy and Environment (MOEE, Canada), enrichment factors (EFs), and a geo-accumulation index (Igeo) approach. The sediments exceeded MOEE Lowest Effect Levels (LELs) consistently for Cr and Cu and a small proportion of samples (5%) for Hg. Levels of As, Cd, Fe, Pb, and Zn did not exceed LELs and none of the samples exceeded the Severe Effect Levels (SELs). In addition to the sediment guidelines, both the EF and Igeo calculations suggested levels of Mn and Fe were severely enriched, while the EF indicated Cd was slightly enriched. Metal levels in the Shadegan wetland exhibited both spatial and seasonal trends. Metal levels were greater near input areas from agricultural, urban, and industrial discharges and runoff as compared to the more remote and quiescent central part of the wetland. Except for Fe, the metal levels were greater in the wet season as compared to the dry season, perhaps due to greater stormwater runoff and sediment loads. This study provides baseline data which can be used to support development of appropriate contaminant source management strategies to help ensure conservation of these valuable wetland resources.

The spatial distribution, accumulation and potential source of seldom monitored trace elements in sediments of Three Gorges Reservoir, China

The alteration of hydrologic condition of Three Gorges Reservoir (TGR) after impoundment has caused numerous environmental changes. This study investigated the distribution, accumulation and potential sources of the seldom monitored trace elements (SMTEs) in sediments from three tributaries (ZY, MX and CT) and one mainstream (CJ) in TGR during different seasons. The average contents of most SMTEs excluding Sb in the winter were similar to that in the summer. For Sb, its average concentrations in the summer and winter were roughly six and three times higher than its background value, respectively. Contamination factor (CF) and geoaccumulation index (Igeo) demonstrated that most of the sediments were obviously contaminated by Sb. The enrichment factors (EF) of Ga and Sb were higher than 2.0, revealing the possible anthropogenic inputs; However, the EFs of other SMTEs were lower than 1.5, indicating the natural inputs. Correlation and principal component analysis suggested the most SMTEs were positively correlated with major elements (Cr, Mn, Cu, Zn, As, Cd and Pb) and clay contents, which implies that SMTEs had the same sources with these major metals, and the fine particles might be a major carrier for transporting SMTEs from the rivers to the TGR.

Trace-Metal Enrichment and Pollution in Coastal Sediments in the Northern Tyrrhenian Sea, Italy

This study evaluated the distribution pattern and pollution of chromium, arsenic (As), manganese (Mn), nickel, lead, and copper in surface sediments along the northern Latium coast of the Tyrrhenian Sea in Italy. The enrichment factor, geoaccumulation index, and potential toxicity response index were used to evaluate the degree of contamination. These results show As and Mn contamination. The high enrichment and contamination levels of As and Mn are located in two hot spots. These elevations are due to naturally high levels of As and Mn in the Mignone River and the Marangone Stream as well as the intense human activity in the area including the largest energy production site in Europe (Torrevaldaliga Nord coal-fired power plant) and of one of the most important ports for cruise traffic in the Mediterranean Sea.

Spatial distribution and source analysis of heavy metals in the marine sediments of Hong Kong

A data matrix, obtained during a 3-year monitoring period (2010-2012) from 45 sampling locations in the marine of Hong Kong, was subjected to pollution indicator and multivariate statistical technique analysis to investigate the spatial distribution and origin of the selected 12 heavy metals. Results suggested that V, Ni, and Ba were at safe levels, and there was a significant anthropogenic effect on Zn, Pb, Cu, Cd, and Cr, which were moderate to severe enrichment at some locations. Sampling locations 1, 2, 7, 9, 12, 13, 14, 30, 31, and 32 were identified as pollution hot spots. Principal component analysis and cluster analysis showed that Zn, Pb, Cu, Cd, and Cr were primarily controlled by anthropogenic sources and Ni, Ba, and V by natural sources. Whereas, Al, Fe, Mn, and As were controlled by both anthropogenic and natural sources. Cluster analysis classified 45 sampling sites into five groups and analysis of variance indicated there were significant differences between different groups. The pollution hot spots were classified into moderate or high polluted groups, and the influential factor of the heavy metal distribution was analyzed.

Spatial Distribution of Selected Heavy Metals in Surface Sediments of the EEZ of the East Coast of Peninsular Malaysia

Spatial distribution of selected metals (Al, Fe, Mn, Zn, Cu, and Co) in surface sediments in the EEZ of the east coast of Peninsular Malaysia was investigated. The aim of this paper is to determine the distribution pattern and pollution status of heavy metals in tropical shelf sediments since limited information is available. Heavy metal concentrations ranged between 207.58 and 491.33 µg·g−1 for Mn, 36.13 and 125.93 µg·g−1 for Zn, 14.49 and 22.33 µg·g−1 for Cu, 2.00 and 11.12 µg·g−1 for Co, 6.20 and 8.95% for Fe, and 0.94 and 6.62% for Al. The mean concentrations of heavy metals are in decreasing order as follows: Fe > Al > Mn > Zn > Cu > Co. Most metals registered low concentrations at the nearshore areas. Pearson correlation indicates that most of the metals are derived from the miscellaneous sources. Based on the EFs and Igeo, it is implied that the surface sediment trace metal levels in the study area might be enriched by anthropogenic sources. However, the PLI suggests that this area is not contaminated from the measured heavy metals. This work is important to register the current levels of metals so that any change in concentration can be monitored and managed.

Heavy metal pollution assessment in relation to sediment properties in the coastal sediments of the southern Caspian Sea

This study aimed to evaluate major elements and heavy metal concentrations of Arsenic (As), Copper (Cu), Chromium (Cr), Cobalt (Co), Vanadium (V), Nickel (Ni), lead (Pb) and Zinc (Zn) in surface sediments of the southern Caspian Sea. Metal contents in the sediment were observed in the order of: V>Cr>Zn>Ni>Co>Cu>Pb>As. Correlations between elements showed that sediment TOM, grain size and chemical composition are the main factors that influence the distribution of heavy metals. According to the pollution load index (PLI), sediments from some sampling sites were polluted. Concentrations of Ni, As, Cr and Cu were higher than sediment quality guidelines at some sampling sites, implying potential adverse impacts of these metals.

Seaweeds as bioindicators of heavy metals off a hot spot area on the Egyptian Mediterranean Coast during 2008-2010

Concentrations of Cu, Zn, Cd, Pb, Ni, Co, Fe, Mn, and Hg were measured successively in water, sediments, and six macroalgal species belonging to three algal classes during 3 years (2008-2010) from Abu Qir Bay, Alexandria, Egypt: Chlorophyceae (Enteromorpha compressa, Ulva fasciata), Phaeophyceae (Padina boryana), and Rhodophyceae (Jania rubens, Hypnea musciformis, Pterocladia capillacea). The study aimed to assess the bioaccumulation potential of the seaweeds, as well as to evaluate the extent of heavy metal contamination in the selected study site. Metals were analyzed using atomic absorption spectrophotometry coupled with MH-10 hydride system. The obtained data showed that the highest mean concentrations of Cu, Zn, Fe, and Mn were recorded in E. compressa; Cd, Ni, and Hg exhibited their highest mean concentrations in P. boryana, while Pb and Co were found in J. rubens. Abundance of the heavy metals in the algal species was as follow: Fe > Mn > Zn > Pb > Ni > Co > Cu > Cd > Hg. E. compressa showed the maximum metal pollution index (MPI) which was 11.55. Bioconcentration factor (BCF) for the metals in algae was relatively high with a maximum value for Mn. The Tomlinson pollution load index (PLI) values for the recorded algal species were low, which ranged between 1.00 in P. boryana and 2.72 in E. compressa. Enrichment factors for sediments were low fluctuating between 0.43 for Hg to 2.33 for Mn. Accordingly, the green alga E. compressa, brown alga P. boryana, and red alga J. rubens can be nominated as bioindicators. Based on MPI and PLI indices, Abu Qir Bay in the present study is considered as low-contaminated area.

Assessment of potential risks associated with heavy metal contamination in sediment in Aobaopao Lake, China, determined from sediment cores

Lianhuan Lake is found in the lowest point of the Songnen Plain in Eastern China and is a typical hardwater lake. Lianhuan Lake is constituted by eighteen lakes and Aobaopao Lake is located in the eastern portion. Geochemical features and pollution history of heavy metals in Aobaopao Lake were investigated. Total metal contents and chemical fractionations of Cu, Fe, Mn, Ni, Pb, Cd, Cr and Zn were analyzed for core sediment samples taken from north sampling site for Core AB1 and south sampling site for Core AB2 of the lake using the speciation extraction procedure proposed by the Commission of the European Communities Bureau of Reference (BCR) together with grain size and TOC measurements. Heavy metal analyses showed that sediments have similar geochemical features. In order to quantify the anthropogenic contamination of the metals according to their speciation composition, the RSP approach was applied. In Core AB1, Cd is moderate and significant contaminate while Mn is minor, moderate and significant contamination. In Core AB2, Cd is more significant contaminate from 3.75 cm to the surface. The risk assessment code (RAC) established by Perin et al. (Heavy Metals in the Environment, CEP Consultants, Edinburgh, 1985) was used to evaluate the risk of heavy metals in sediments of Aobaopao Lake. The results for both cores suggest that Mn and Cd posed a high risk to local environment.

Distribution and ecological risk assessment of heavy metals in surface sediments along southeast coast of the Caspian Sea

The present study aimed to evaluate heavy metal concentrations of Arsenic (As), Copper (Cu), Nickel (Ni), Lead (Pb) and Zinc (Zn), their spatial distribution, enrichment factor index (EF), the pollution load index (PLI) and potential ecological risk (PER) in two different seasons of the year (winter and summer) in surface sediments along southeast coast of the Caspian Sea. The results indicated that there were significant differences between concentrations of As, Ni and Pb in two different seasons. Considering PER, sediments from southeast Caspian coast had low ecological risk. According to PLI, sediment from the southeast coast had no pollution. Risk assessment showed that As threshold concentrations to occasionally be exceeded in the study area.

Trace element contamination in the estuarine sediments along Tuticorin coast--Gulf of Mannar, southeast coast of India

Sediment samples were collected from Kallar, Korampallam creek and Punnakayal estuaries of Tuticorin coast for assessing the level of contamination by trace elements in these estuarine sediments. The trace element concentration, calcium carbonate, organic carbon and mercury level were analyzed by Inductively Coupled Plasma Atomic Emission Spectrophotometer, Titrimetric method and SnCl2 reduction method. The results reveals that the enrichment factor, metal pollution index and geo-accumulation index of these estuarine sediments were predominantly polluted by Cd, As, Zn, Hg and Pb. The factor analysis revealed the source of trace element accumulation in the estuarine sediments particularly Mn and Fe are from riverine inputs and As and Hg from untreated industrial effluents. Among the selected estuaries, Korampallam creek was found to be highly contaminated by trace elements due to the discharge of effluents from thermal power plant, Tuticorin alkali chemicals, copper smelting, Petrochemical industries and shipping activities.

Application of sequential leaching, risk indices and multivariate statistics to evaluate heavy metal contamination of estuarine sediments: Dhamara Estuary, East Coast of India

In the present study, concentration of some selected trace metals (Fe, Mn, Ni, Co, Pb, Zn, Cu, Cr and Cd) are measured in Brahmani, Baitarani river complex along with Dhamara estuary and its near shore. Chemical partitioning has been made to establish association of metals into different geochemical phases. The exchangeable fraction is having high environmental risk among non-lithogeneous phases due to greater potential for mobility into pore water. The metals with highest bio-availability being Cd, Zn and Cr. The metals like Mn, Zn, Cd and Cu represent an appreciable portion in carbonate phase. Fe-Mn oxides act as efficient scavenger for most of the metals playing a prime role in controlling their fate and transport. Among non-lithogeneous phases apart from reducible, Cr showed a significant enrichment in organic phase. Risk assessment code values indicate that all metals except Fe fall under medium-risk zone. In estuarine zone Cd, Zn, Pb and Cr are released to 32.43, 26.10, 21.81 and 20 %, respectively, indicating their significant bio-availability pose high ecological risk. A quantitative approach has been made through the use of different risk indices like enrichment factor, geo-accumulation index and pollution load index. Factor analysis indicates that in riverine zone, Fe-Mn oxides/hydroxides seem to play an important role in scavenging metals, in estuarine zone, organic precipitation and adsorption to the fine silt and clay particles while in coastal zone, co-precipitation with Fe could be the mechanism for the same. Canonical discriminant function indicates that it is highly successful in discriminating the groups as predicted.

An ecotoxicological analysis of the sediment quality in a European Atlantic harbor emphasizes the current limitations of the Water Framework Directive

The "PortoNovo" project was developed to standardize the methodologies for water quality management in the port areas of coastal Atlantic regions to improve the Water Frame Directive (WFD) for these specific water bodies. Under this scope, water and sediment samples were collected from five sites within the Port of Aveiro, Portugal. According to the physical and chemical parameters that were analyzed (i.e., metals, total organic carbon, polychlorinated biphenyls and polycyclic aromatic hydrocarbons), the sediments were not considered at risk based on European sediment quality laws. However, the bioassays that were performed on the sediment samples (Microtox®) and the standardized acute toxicity test using the marine rotifer, Brachionus plicatilis, on sediment elutriates revealed higher toxicity levels. The use of bioassays to assess sediment quality clearly complements more conservative approaches and highlights current gaps within the WFD. The approach presented here can be easily transferred to other port areas for more reliable water quality management.

Spatial distribution and source identification of persistent pollutants in marine sediments of Hong Kong

A data matrix, obtained during a 3-year monitoring period (2007-2009) from 45 sampling sites in Hong Kong marine, was subjected to determine the spatial characterization and identify the sources of main pollutants. Indicator analyses indicated that polycyclic aromatic hydrocarbons (PAHs), nickel, manganese, and arsenic (As) were at safe levels. Five heavy metals (zinc, lead, cupper, cadmium, chromium (Cr)) were moderate to severe enrichment at some sites. Inner Deep Bay and Victoria Harbor were considered as hot spots for PAHs and the heavy metals, while Tolo Harbor was highly polluted by the heavy metals. Cluster analysis classified the 45 sampling sites into three groups, representing different pollution levels. Principal component analysis/factor analysis identified four principal components (PCs) and explained 84.9 % of the total variances, standing for persistent pollution, N factor, P and Cr factor, and As factor, respectively. Group A was highly polluted by persistent pollution, group B was the less polluted group, and subgroup B1 was less affected by PC3 and PC4 than subgroup B2. Group C, considered as the moderately polluted group, was greatly affected by N factor or persistent pollution, while subgroup C2 received more N pollution than subgroup C1.

Application of DET (diffusive equilibrium in thin films) and DGT (diffusive gradients in thin films) techniques in the study of the mobility of sediment-bound metals in the outer section of Songkhla Lake, Southern Thailand

The techniques of diffusive equilibrium in thin films (DET) and diffusive gradients in thin films (DGT) were used in the outer section of Songkhla Lake, Thailand in order to obtain high-resolution profiles of total dissolved and labile trace metals in the sediment pore water and investigate benthic fluxes. Six DET probes and six DGT probes were deployed at the mouths of the Phawong, Samrong and U-Taphao canals. A close correspondence could be observed between the high-resolution profiles of Fe and As, revealing a close link between the reductive remobilization of Fe oxides and the reduction of As(V). Co and Ni DGT profiles showed a close correspondence with Mn, but a narrow mobilization zone. Reductive mobilization of Mn oxides and associated metals and sulfide precipitation control the behaviour of these metals. The DGT profiles of Cu, Zn, Cd and Pb show surface maximum, probably linked to organic matter degradation. Important benthic fluxes, especially for As, were found at the mouths of the U-Taphao and Phawong canals.

Statistical apportionment and risk assessment of selected metals in sediments from Rawal Lake (Pakistan)

The present study was carried out in order to evaluate the statistical apportionment and risk assessment of selected metals (Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Pb, Sr, and Zn) in freshly deposited sediments in Rawal Lake, Pakistan. Composite sediment samples were collected, oven-dried, grounded, homogenized, and processed to assess the water-soluble and acid extractable concentrations of the metals in the water extract and acid extract of the sediments using flame atomic absorption spectrophotometer. Statistical methods were used to identify the possible sources of the metals. Sediment quality guidelines and potential acute toxicity were used to evaluate the ecotoxicological sense of selected metals. Non-carcinogenic health risk assessment was also carried out to determine the potential adverse health risks to the inhabitants. Relatively higher concentration was noted for Ca, Fe, Mg, Na, K, Mn, and Sr in the sediment samples. Principal component analysis and cluster analysis revealed anthropogenic contributions of Cd, Pb, Cr, Mn, Fe, and Li in the sediments. Enrichment factors of the metals in sediments showed severe to moderate enrichment of Cd, Pb, Ca, Fe, Li, Mn, and Sr. Geoaccumulation indices and contamination factors evidenced significant contamination by Cd and Pb, although, on the whole, low degree of contamination was noted. The levels of some metals exceeded the sediment quality guidelines, which revealed frequently adverse biological effects to the dwelling biota in the aquatic ecosystem. The sediments were found to be significantly contaminated by Cd, Pb, Cr, Mn, Fe, and Li.

Distribution of trace metals in marine sediments of the Bay of Palma de Mallorca (Mallorca Island, Spain)

Metals were determined in surface bottom marine sediments of the Bay of Palma de Mallorca (Spain) by microwave-assisted acid-oxidant digestion and inductively coupled plasma-optical emission spectrometry in order to assess the level and distribution of potentially metallic pollutants. Average concentrations found were 1.2 ± 0.3 Al and 1.9 ± 0.9 Fe (in milligrams per gram), and 8 ± 2 Cr, 2 ± 1 Cu, 60 ± 10 Mn, 4 ± 1 Ni, 6 ± 4 Pb, 50 ± 7 Sn and 10 ± 3 Zn (in micrograms per gram). Enrichment factors using normalized values to Al were also calculated which indicated that sediments were Sn and Pb enriched. Sediments were fractionated by grain size: <63, 63-250, 250-500 and >500 (in micrometres), and the metals' affinity towards the different fractions was studied. The metals' affinity to the finer fraction was evidenced, excluding Sn and Mn that showed practically no affinity for fine grains. Latent variables were extracted from the data using principal components analysis. It allowed samples to be grouped in two clusters, and most of the metals (Al, Cr, Cu, Fe, Ni, Pb and Zn) showed a similar distribution pattern. Sn and Mn showed a distinct pattern.