Some potential hazardous trace elements contamination and their ecological risk in sediments of western Chaohu Lake, China

Geochemical fractionation of trace metals and ecological risk assessment of surface sediments in Sepetiba Bay, Brazil

The Sepetiba Bay (Southeast Brazil) is a known Cd- and Zn-contaminated site that received spills of a large slag pile leachate from a Zn smelter. With important harbors, Sepetiba Bay demands periodic dredging operations which affect the mobility of the metals. The main goal of this work was to assess metal mobility in sediments and its associated toxicity in a fictive dredging area, to evaluate the risks of the operation. To achieve this goal, 18 superficial sediment samples were collected and characterized for pH and Eh. Sediments were analyzed for grain size, organic carbon, and total nitrogen, and metal mobility was evaluated with a sequential extraction procedure, proposed by the European Community Bureau of Reference (BCR). The results demonstrate that Cd and Zn are mainly associated with the exchangeable fraction (mean concentrations 1.4 mg kg-1 and 149.4 mg kg-1, respectively) and reducible fractions (mean concentrations 0.3 mg kg-1 and 65.5 mg kg-1, respectively), while Fe, Cr, Cu, Ni, and Al were associated with the residual fraction. Metals in the residual fraction are probably associated with the mineral lattice of the sediment and should not represent an environmental risk for the biota. The application of the enrichment factor and three risk assessment indexes (Risk Assessment Code, Risky Pollution Index, and Bioavailability Risk Assessment Index) show that the sediments are considerably enriched in metals that constitute a relevant risk for the sediment biota. In the case of dredging operations, Cd and Zn should be released to the overlying waters and be available to organisms, threatening the whole ecosystem. The proposed approach was shown to be much more precise than what is frequently presented in the Environmental Impact Assessments that only consider the threshold limits of the legislation.

Spatial-temporal distribution, occurrence, water quality, and risk assessment of trace elements in ten rivers surrounding Chaohu Lake in China

As one of the five great lakes in China, the Chaohu Lake Basin is the main water source for regional economic and ecological development in Hefei city and is considered a source of drinking water. The spatial-temporal distributions and occurrence of soluble trace elements were studied in the surrounding ten rivers in the Chaohu Lake Basin as well as water quality and risk assessment during the normal and wet seasons. Principal component analysis (PCA) showed that the main source of river pollution during the two seasons was the mining industry. High values of most elements were found in the northwestern rivers in the two seasons. The temporal changes in the elements showed that the distributions of As, Mn, Cd, and Cu in the two seasons were very different, but the trends of Ni, Co, and V were basically the same. The sodium adsorption ratio (SAR) showed that almost all river samples needed to be treated before irrigation, and the water quality index (WQI) showed that most samples were of excellent water quality for drinking. The ecological risk assessment results showed that the risks in the two seasons were all slight. The results of the health risk evaluation suggested that no noncarcinogenic risks were found in the normal season and that the carcinogenic risks from Cr and As reached their highest levels in the normal and wet seasons, respectively. This research can provide vital data for rational water control and water quality conservation, offer a scientific basis for ecological environment safety, and offer a reference for carcinogenic and noncarcinogenic health risks to regional residents.

Sedimentary record of silver in recent times from Chaohu Lake, East China, and its implications

High-resolution record of silver (Ag) in lakes is indispensable for examining human impact on its deposition, and for understanding its geochemical cycling in the environment. However, such studies are extremely insufficient. In this study, a piston core (CHY) collected from the Chaohu Lake, east China, was analyzed to examine sedimentary history of Ag. A record of this metal in recent times was further reconstructed. The record displays significant changes. Prior to the 1960s, Ag concentrations stabilized at a relatively low level (0.06 ppm), but they increased rapidly (0.26 ppm) afterward. The average concentration of Ag in the profile is 0.13 ppm, higher than its crustal abundance. Enrichment factor (EF) analysis further reveals that Chaohu Lake was not polluted with Ag until the 1960s, but the pollution level increases rapidly since then, and now shows a moderate pollution. Sedimentary record of Ag closely follows population changes within the watershed, suggesting that human activity is possibly the ultimate driving factor for its distribution. Intensified industrial activities associated with population expansion may release silver to inflow rivers and Chaohu Lake, resulting in its ultimate settling down to the sediments. Sedimentary flux of Ag varies significantly between 42.9 and 392.0 μg/(m²·year), with an average of 236.8 μg/(m²·year). This is so far as we know the first high-resolution record of Ag and its flux in east China, providing new perspective for better understanding the distribution and transport of Ag in lake environment.

Source tracing with cadmium isotope and risk assessment of heavy metals in sediment of an urban river, China

The Nanfei River was one of dominant inflowing rivers of the fifth largest freshwater Chaohu Lake in China, which had been subjected to increasing nutrients and contaminants from population expansion, rapid industrialization and agricultural intensification in recent decades. In present study, surface sediment from the Nanfei River was collected to investigate the anthropogenic impact on distribution and bioavailability of heavy metals. Possible Cd sources along the river were constrained by using Cd isotope signatures and labile concentrations of heavy metals in sediment were determined through the DGT technique for risk assessment. Results showed that Cd in river sediment showed greatest enrichment (EF 0.8-9.4), indicating massive pollution from anthropogenic activities. Among the various possible Cd source materials, urban road dust, industrial soil and chicken manure, displayed higher Cd abundance and enrichment that might contribute to Cd accumulation in river sediment. Cadmium isotopic composition in river sediment was ranged from -0.21 ± 0.01‰ to 0.13 ± 0.03‰, whereas yielded relative variation from -0.31 ± 0.02‰ to 0.23 ± 0.01‰ in source materials. Accordingly, Cd sources along the river were constrained, i.e. traffic and industrial activities in the upper and middle reaches whereas agricultural activities in the lower reaches. Furthermore, the evaluation on ecological risk of heavy metals in sediment on basis of SQGs and DGT-labile concentrations demonstrated that Pb and Zn might pose higher risk on aquatic species. The present study confirmed that Cd isotopes were promising source tracer in environmental studies.

A New Methodological Approach for the Assessment of the 238U Content in Drinking Water

The radiological quality of drinking water is directly associated with the health of the population. Indeed, it is well known that the presence of radionuclides in drinking water constitutes a health risk for humans because the consumption of such water increases the likelihood of incurring cancer. For this reason, all the studies aimed at developing new methodologies for the qualitative and quantitative analysis of the radioisotopic composition of drinking water are absolutely desired by the international scientific community, as well as by the institutes that deal with the protection of public health. In this paper, a new methodological approach was developed for the evaluation of the 238U content in drinking water. A sample coming from Paola, Calabria region, southern Italy, was taken as a case study. The assessment was performed by using High Purity Germanium (HPGe) gamma-ray spectrometry, with the aim of quantifying the specific activity of the 234mPa radioisotope after a preconcentration procedure, and thus to assess the activity concentration of 238U, in the hypothesis of the secular radioactive equilibrium between it and its daughter. The obtained results were validated through the comparison with the 238U (µg/L) concentration as measured with Inductively Coupled Plasma-Mass Spectrometry (ICP-MS).

Impact of Urbanisation Intensity on Bird Diversity in River Wetlands around Chaohu Lake, China

Urbanisation is known to result in 'urban stream syndrome', which poses a huge threat to the river health. Birds, which are an important part of the river ecosystem, are sensitive to environmental changes in the basin. The ratio of the impervious surface area is a macroscopic indicator of urbanisation intensity in river basins. In this study, we combined the results of a year-round field survey of seven river wetlands around Chaohu Lake (China) with satellite remote sensing image data from the same period. The species richness at sections of the lake entrance was higher than in the middle sections of the river, and the Shannon-Wiener index during autumn was higher than that during winter. The waterbird diversity index declined exponentially with increases in the intensity of urbanisation. The changes in the land use patterns around river wetlands associated with urbanisation resulted in the loss of food resources and habitats. Therefore, the intensity of urbanisation was an important driving factor that leads to changes in the bird community structure of river wetlands, so it had a significant impact on the diversity of river wetland birds in all four seasons combined with a variety of influencing factors. Our research could be a guide for urban landscape planning and bird diversity protection. For example, the results suggested that it is necessary to identify river wetlands as an important part of the urban ecosystem, reduced building area, increased vegetation coverage, and retained slope protection and river beach land.

Source, degree and potential health risk of metal(loid)s contamination on the water and soil in the Söke Basin, Western Anatolia, Turkey

Water and soil quality are the two most important parameters for sustainable agriculture and regional development in the basin. This study focused on the causes of soil and water contamination and the potential impact of drinking water on community health. Reasons for metal(loid)s enrichment in the water and soil in the Söke Basin were examined by considering anthropogenic and geogenic inputs. Four rock samples in the drainage network, 28 soil samples, and 29 water samples in the Söke Plain were collected. All samples were analyzed for metal(loid)s by inductively coupled plasma-mass spectrometry (ICP-MS). The carcinogenic and non-carcinogenic effects of water on human health were calculated mathematically. Potential ecological risk index (PERI), enrichment factor (EF), and ecological risk (ER) were calculated for the soil samples. In addition, principal component analysis (PCA) with Varimax rotation and Kaiser normalization was applied to the soil data set. Cr, Ni, and Cd contamination in soils was associated with anthropogenic inputs, while arsenic contamination was related to both anthropogenic and geogenic inputs. As, B, Ba, Pb, and Sb contamination was found in some drinking water. As contamination has been clearly found to be caused by natural geological processes in and around Lake Azap. It was determined that metal(loid)s enrichment occurred in drinking water due to the mixing of geothermal waters affected by seawater intrusion with surface and groundwater. Contamination inputs were geogenic, but their negative impacts appearing in surface water and drinking water occurred due to human influence.

Radioactivity, Metals Pollution and Mineralogy Assessment of a Beach Stretch from the Ionian Coast of Calabria (Southern Italy)

In the present article, a case study is reported regarding an investigation carried out in order to assess radioactivity concentration, heavy metals pollution and mineralogy of a beach stretch extending from Soverato to Squillace municipalities of the Ionian coast of Calabria, South of Italy, a popular tourist destination, especially in summer. The analysis of radionuclides contents was performed by using a High Purity Germanium (HPGe) gamma-ray detector, in order to quantify the average specific activity of ²²⁶Ra, ²³²Th and ⁴⁰K natural radionuclides and ¹³⁷Cs anthropogenic radioisotope. The absorbed dose rate and the annual effective dose equivalent radiological hazard indices were also estimated. Furthermore, X-ray Fluorescence (XRF) spectrometry measurements were carried out for the quantitative elemental analysis of the sand, in order to investigate any possible chemical pollution by heavy metals. For this aim, different indices such as Enrichment Factor (EF), Geoaccumulation Index (I_geo), Contamination Factor (CF) and Pollution Load Index (PLI) were applied to estimate the level of toxicity imposed on the ecosystem by the detected heavy metals. Finally, in order to identify the crystalline mineral components of the investigated sand samples, X-ray Diffraction (XRD) and Micro-Raman Scattering (MRS) measurements were carried out.

Trends and Sources of Heavy Metal Pollution in Global River and Lake Sediments from 1970 to 2018

Heavy metal pollution is a global problem although its sources and trends differ by region and time. To data, no published research has reported heavy metal pollution in global rivers and lakes. This study reviewed past sampling data across six continents from 1970 to 2018 and analyzed the trends and sources of 10 heavy metal species in sediments from 289 rivers and 133 lakes. Collectively, river sediments showed increasing trends in Cd, Cr, Ni, Mn, and Co and decreasing trends in Hg, indicating that rivers acted as a sink for the former and a source for the latter. Lake sediments showed increasing trends in Pb, Hg, Cr, and Mn, and decreasing trends in Cd, Zn, and As, indicating that lakes acted as a sink for the former and a source for the latter. Due to difference in natural backgrounds and development stage in continents, mean metal concentrations were generally higher in Europe and North America than in Africa, Asia, and South America. Principal component analysis showed that main metal source was mining and manufacturing from the 1970s to 1990s and domestic waste discharge from the 2000s to 2010s. Metal sources in sediments differed greatly by continent, with rock weathering dominant in Africa, mining and manufacturing dominant in North America, and domestic waste discharge dominant in Asia and Europe. Global trends in sediment metal loads and pollution-control measures suggest that the implementation of rigorous standards on metal emissions, limitations on metal concentrations in manufactured products, and the pretreatment of metal-contaminated waste have been effective at controlling heavy metal pollution in rivers and lakes. Thus, these efforts should be extended globally.

Evaluation of potential ecological risk, possible sources and controlling factors of heavy metals in surface sediment of Caohai Wetland, China

Caohai, a plateau wetland in Southwest China, is a national nature reserve providing protection for a variety of threatened and endangered species of migrant birds (e.g., the black-necked crane Grus nigricollis). It has been experiencing the increasing environmental problems with heavy metals due to anthropogenic activities. However, the contamination of heavy metals in different habitats is unclear. Surface sediment samples from these habitats were thus collected to analyze the distribution characteristics, potential risk and possible sources for heavy metals (Cd, Hg, Pb, Zn, Ni, Cr, Cu, Be, and V). The results showed that all of Cd, Hg, Pb, Zn, Cr, and Ni concentrations exceeded the background values, and these elements (except Cr and Ni) presented comparatively high levels in habitat adjacent to urban in comparison with the other habitats. Based on the regression analysis, we found that metals with higher EFs (Cd, Hg, Pb, and Zn) were mainly controlled by anthropogenic loadings, while metals with lower EFs (Cr, Ni, Be, and V) were mainly associated with sediment properties (pH or NOM). In addition, the results from geo-accumulation index, Hakanson potential ecological risk assessment, and risk assessment code showed that Cd and Hg posed a medium to high environmental risk to the ecosystem, and the other heavy metals posed no or low risk. Therefore, to protect this wetland ecosystem and to supply a well habitat for migratory birds, greater efforts aimed at reducing anthropogenic discharges and remediating sediment contaminated with heavy metals should be pursued.

Metal concentrations in fish from nine lakes of Anhui Province and the health risk assessment

In the present study, to comprehensively investigate the metal contamination in the fish of Anhui Province, four fish species, Ctenopharyngodon idella, Cyprinus carpio, Hypophthalmichthys molitrix, and Hypophthalmichthys nobilis, were collected from nine lakes, and the levels of Zn, Pb, Cr, Cu, Ni, As, Hg, and Cd in the fish muscle were determined. The results showed that the highest concentrations of Zn (7.791 mg/kg), Pb (0.522 mg/kg), Cr (0.030 mg/kg), and Cu (0.767 mg/kg) were found in Tiangang Lake, Xifei Lake, Tiangang Lake and Baidang Lake, respectively. However, metals Ni, As, Hg, and Cd were not detected in all fish samples. In the fish species, the metal bioaccumulation ability was decreased with the following order: C. idellus > H. molitrix > H. nobilis > C. carpio. Furthermore, the target hazard quotient (THQ) was used to assess the health risk via fish consumption. The results indicated for co-exposure; C. idellus would pose a health risk to children at high exposure level (95th) as THQ value was higher than 1. It should be pointed out that Pb contributes most to the total THQs (the ratio was 88%); thus, the contamination of Pb should be paid more attention. This field investigation combined with health risk assessment would provide useful information on the heavy metal pollution in Anhui Province.

Water pollution characteristics and analysis of Chaohu Lake basin by using different assessment methods

In the context of the water environmental protection and local economic sustainable growth, it is of great importance to conduct a comprehensive water quality assessment in Chaohu Lake basin. In this study, dissolved oxygen (DO), permanganate index (COD_Mn), 5-day biochemical oxygen demand (BOD₅), ammonia nitrogen (NH₃-N), total nitrogen (TN), and total phosphorus (TP) were investigated monthly at 24 sampling sites in Chaohu Lake basin during 2015 to 2017. Five methods were used to evaluate water quality and identify dominant pollutants. Results showed that the dominant pollutants in Chaohu Lake were TN (4.17~11.61 mg L^-1) and TP (0.27~0.75 mg L^-1). The upstream of Chaohu Lake was influenced by Nanfei River, Shiwuli River, and Paihe River, and water quality of the upstream (eutrophic) was worse than that of the downstream (mesotrophic) part of Chaohu Lake. Comprehensive Water Quality Identification Index Method (CWQII) can better assess the water quality compared with the other methods by providing qualitative and quantitative analysis. The index values assessed by CWQII method for Nanfei River, Shiwuli River, and Paihe River were 5.819, 5.986, and 5.141, respectively, and water quality were all assessed as grade V. Overall, water quality of Chaohu Lake has been slightly improved during 2015~2017, but water quality of western inflowing rivers was still heavily polluted. These findings provide valuable information and guidance for water pollution control and water resource management in Chaohu Lake basin. Several feasible measures are proposed.

Evaluation of oxidative stress biomarkers in the freshwater gammarid Gammarus dulensis exposed to trout farm outputs

The current study reports a combined seasonal monitoring of the Crnica River watercourse using physico-chemical parameters and biomarkers measured in Gammarus dulensis with the aim of correlating the effects of pollution with the level of oxidative stress biomarkers in this amphipod. The pollution source is identified as a trout farm in the upper part of the Crnica River (Eastern Serbia). Physico-chemical water parameters and sediment trace element concentrations were measured in the Crnica River during three seasons. Three localities downstream [CR2, CR3, and CR4 (20 m, 400 m, and 1.3 km from the trout farm discharge, respectively)] were assessed in comparison with a reference location (CR1), 250 m upstream from the trout aquaculture in the Crnica River. Antioxidant biomarkers including the enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), and glutathione-S-transferase (GST) were determined in pooled samples of G. dulensis. Our findings showed statistically different antioxidant enzyme levels in gammarids from the first downstream locality (CR2) compared to those from other three localities. The results indicate that oxidative stress occurred to some extent despite the assumed antioxidant induction as a result of exposure to elevated levels of some elements and changed water parameters, the effects seeming in part to be mediated by suppression of SOD and CAT (during summer and autumn); and by suppression of GPX and GR (during autumn) at the CR2 locality. The activity of GST in all seasons was higher at the CR2 locality than at the other localities, suggesting the presence of some permanent xenobiotic next to the aquaculture output. Seasonal difference in the physical and chemical water parameters and sediment trace element concentrations were observed. Overall, our results indicate a locality- and season-dependent antioxidant enzymes response in G. dulensis, pointing at progressively reduced deleterious effect of trout farm outputs with movement further downstream.

The Optimal Width and Mechanism of Riparian Buffers for Storm Water Nutrient Removal in the Chinese Eutrophic Lake Chaohu Watershed

Riparian buffers play an important role in intercepting nutrients entering lakes from non-point runoffs. In spite of its ecological significance, little is known regarding the underlying mechanisms of riparian buffers or their optimal width. In this study, we examined nutrient removal efficiency, including the quantity of nutrients and water quality, in the littoral zone of different types of riparian buffers in the watershed around eutrophic Lake Chaohu (China), and estimated the optimal width for different types of riparian buffers for effective nutrient removal. In general, a weak phosphorus (P) adsorption ability and nitrification-denitrification potential in soil resulted in a far greater riparian buffer demand than before in Lake Chaohu, which may be attributed to the soil degradation and simplification of cover vegetation. In detail, the width was at least 23 m (grass/forest) and 130 m (grass) for total P (TP) and total nitrogen (TN) to reach 50% removal efficiency, respectively, indicating a significantly greater demand for TN removal than that for TP. Additionally, wetland and grass/forest riparian buffers were more effective for TP removal, which was attributed to a high P sorption maximum (Qmax) and a low equilibrium P concentration (EPC0), respectively. The high potential nitrification rate (PNR) and potential denitrification rate (PDR) were responsible for the more effective TN removal efficiencies in grass riparian buffers. The nutrient removal efficiency of different types of riparian buffers was closely related with nutrient level in adjacent littoral zones around Lake Chaohu.

Agricultural management of an Oxisol affects accumulation of heavy metals

Soil contamination may result from the inadequate disposal of substances with polluting potential or prolonged agricultural use. Therefore, cadmium (Cd), chromium (Cr) and nickel (Ni) concentrations were assessed in a Eutroferric Red Oxisol under a no-tillage farming system with mineral fertilizer applications, a conventional tillage system with mineral fertilizer application and a conventional tillage system with sewage sludge application in an area used for agriculture for more than 80 years. We evaluated the spatial distributions of these elements in the experimental area and the effect of the different management practices on the soil retention of these metals. The concentrations of metals extracted from 422 soil samples by open-system digestion with HNO₃, H₂O₂ and HCl were assessed by flame atomic absorption spectroscopy. The pH and soil organic matter were also assessed, and spatial distribution maps were designed. The mean concentrations of Cd, Cr and Ni (1.0, 50 and 14 mg kg^-1, respectively) in the native forest were higher than the reference values (100, 25 and 8% greater, respectively) in Brazilian legislation, indicating that the source material was the determining factor of the high metal concentrations in the study soils. Soil management with sewage sludge was the major contributor to the accumulation of Cd and Ni, whereas Cr concentration did not vary with management type. Approximately 0.3, 12 and 16% of the experimental area is contaminated with Ni, Cd and Cr, respectively, because their concentrations exceeded the values for alertness or prevention in Brazilian legislation.

Heavy Metal Pollution, Fractionation, and Potential Ecological Risks in Sediments from Lake Chaohu (Eastern China) and the Surrounding Rivers

Heavy metal (Cr, Ni, Cu, Zn, Cd, and Pb) pollution, fractionation, and ecological risks in the sediments of Lake Chaohu (Eastern China), its eleven inflowing rivers and its only outflowing river were studied. An improved BCR (proposed by the European Community Bureau of Reference) sequential extraction procedure was applied to fractionate heavy metals within sediments, a geoaccumulation index was used to assess the extent of heavy metal pollution, and a risk assessment code was applied to evaluate potential ecological risks. Heavy metals in the Shuangqiao and Nanfei Rivers were generally higher than the other studied sites. Of the three Lake Chaohu sites, the highest concentrations were identified in western Chaohu. Heavy metal pollution and ecological risks in the lake’s only outflowing river were similar to those in the eastern region of the lake, to which the river is connected. Heavy metal concentrations occurred in the following order: Cd > Zn > Cu > Pb ≈ Ni ≈ Cr. Cr, Ni, and Cu made up the largest proportion of the residual fraction, while Cd was the most prominent metal in the exchangeable and carbonate-included fraction. Cd posed the greatest potential ecological risk; the heavy metals generally posed risks in the following order: Cd > Zn > Cu > Ni > Pb > Cr.

Spatial distribution of physico-chemical properties and function of heavy metals in soils of Yelagiri hills, Tamilnadu by energy dispersive X-ray florescence spectroscopy (EDXRF) with statistical approach

Soil physico-chemical properties were thought to be important factors in obscuring clear identification of pollutant sources. In the present study physicochemical properties such as, pH, electrical conductivity, bulk density, porosity density, soil texture and color were determined to identify the pollution status using different conventional analytical methods in soils of Yelagiri Hills, Tamilnadu. Soil pH ranges from 5.39 to 8.43 which indicate that the soils are acidic to alkaline in nature. The concentrations of selected heavy metals were determined using energy dispersive X-ray florescence spectroscopy (EDXRF) technique. In all the locations Al is the most abundant metal and Co is the least amount in soil. The relationship between the physico-chemical properties and heavy metals were studied by Pearson correlation. The statistical technique shows that strong significant correlation among the heavy metals. The Chemometric approaches namely: principal component analyses (PCA), hierarchical cluster analysis (HCA), were used for identify the soil pollutant. Spatial distribution of physico-chemical properties of soil such as pH, soil texture (sand, silt, clay) electrical conductivity was studied by geo-statistical methods such as kriging identified areas. The heavy metal mapping also attempted to know the distribution pattern in soils.

Multivariate statistical analysis of heavy metal concentration in soils of Yelagiri Hills, Tamilnadu, India--spectroscopical approach

Anthropogenic activities increase the accumulation of heavy metals in the soil environment. Soil pollution significantly reduces environmental quality and affects the human health. In the present study soil samples were collected at different locations of Yelagiri Hills, Tamilnadu, India for heavy metal analysis. The samples were analyzed for twelve selected heavy metals (Mg, Al, K, Ca, Ti, Fe, V, Cr, Mn, Co, Ni and Zn) using energy dispersive X-ray fluorescence (EDXRF) spectroscopy. Heavy metals concentration in soil were investigated using enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CF) and pollution load index (PLI) to determine metal accumulation, distribution and its pollution status. Heavy metal toxicity risk was assessed using soil quality guidelines (SQGs) given by target and intervention values of Dutch soil standards. The concentration of Ni, Co, Zn, Cr, Mn, Fe, Ti, K, Al, Mg were mainly controlled by natural sources. Multivariate statistical methods such as correlation matrix, principal component analysis and cluster analysis were applied for the identification of heavy metal sources (anthropogenic/natural origin). Geo-statistical methods such as kirging identified hot spots of metal contamination in road areas influenced mainly by presence of natural rocks.

Spatial and temporal variation of heavy metal risk and source in sediments of Dongting Lake wetland, mid-south China

Surface sediments of Dongting Lake wetland were collected from ten sites to investigate variation trend, risk and sources of heavy metal distribution in dry seasons of 2011∼2013. The three-year mean concentrations (mg/kg) of Cr, Cu, Pb, Cd, Hg and As were 91.33, 36.27, 54.82, 4.39, 0.19 and 25.67, respectively, which were all higher than the corresponding background values. Sediment quality guidelines (SQGs) and Geo-accumulation index (Igeo) were used for the assessment of pollution level of heavy metals. The pollution risk of Cd, Hg and As were great and that of Cr needed urgent attention because of its obvious increase. Pollution load index (PLI) and geographic information system (GIS) methods were conducted to assess spatial and temporal variation of heavy metal contamination. Results confirmed an increased contamination contribution inflow from Xiang River. Multivariate statistical analyses were applied to identify contribution sources of heavy metal, which showed anthropogenic origin mainly from mining, smelting, chemical industry and agricultural activity.

Sediment baseline study of levels and sources of polycyclic aromatic hydrocarbons and heavy metals in Lake Nicaragua

Selected metals and polycyclic aromatic hydrocarbons (PAHs) were analyzed in sediment samples from 24 sites in Lake Nicaragua sampled May 2010 to provide a baseline of pollution levels. Cu exceeded the Consensus-Based Sediment Quality Guideline (CBSQG) Threshold Effect Concentrations (TECs) at 21 sites while Ni exceeded the value at one site. Comparison of the sampling sites showed that the south-eastern shore and a central part of the lake contained the highest levels of As, Cd, Cr, and Ni, while the western part of the lake contained the highest levels of Cu, Pb, and Zn. Analysis of PAH levels showed that the CBSQG TECs were exceeded by naphthalene at five sites. The sum concentrations of the 16 US EPA priority PAHs (∑PAH16) ranged from 0.01 mg kg(-1) dw to 0.64 mg kg(-1) dw. The highest ∑PAH16 concentration was found upstream in River Mayales and the PAH composition revealed a heavy PAH fraction (e.g., creosote). The main sources of PAHs in Lake Nicaragua were determined as of diffuse petrogenic and pyrogenic origin as well as diagenetic produced perylene. The relative importance of these PAH sources was determined by interpretation of loading and score plots from a principal component analysis. This study concluded that areas of Lake Nicaragua represent an important pollution baseline for future studies in this lake and other tropical lakes.

Ecological risk assessment of heavy metals in surface sediments of six major chinese freshwater lakes

An overall and comparative ecological risk assessment of heavy metal pollution (including Cu, Zn, Pb, Cd, Hg, Cr, As, and Ni) in surface sediments was conducted for six major shallow freshwater lakes (Taihu Lake, Chaohu Lake, Nansihu Lake, Dongting Lake, Poyang Lake, and Hongze Lake) in China. A spatial database with 339 sediment samples was created through an extensive literature survey. Consensus-based sediment quality guidelines (SQGs) were used as the effect thresholds due to the lack of local eco-toxicological information about heavy metals in the six lakes. The results show that the ecological risk of heavy metal pollution in surface sediments is highest in Dongting Lake, followed by Taihu Lake. Lakes Chaohu, Nansihu, Poyang, and Hongze are at a similar risk level, which is a little lower than that of Lake Taihu. High-risk areas that should be given more attention were identified by spatial analysis. The estuaries of the inlets and outlets of Dongting Lake and the Meiliang Bay in Taihu Lake were found to be such areas. Ineffective environmental supervision and management during the recent years of rapid economic and industrial development in China have led to the pollution of lake sediments by heavy metals. Rigid control and effective management measures to prevent heavy metal pollution are urgently needed in China. In addition, it is necessary for China to develop basic research on the local eco-toxicity and SQGs of freshwater sediments to provide a scientific basis for the management of lake sediment pollution.

Determination of radionuclides and elemental composition of clay soils by gamma- and X-ray spectrometry

Radiochemical and elemental analysis of clay soils collected from different locations within Ekiti State have been performed in this study using gamma and XRF spectrometric measurements. The results of this study show that the mean concentrations of uranium ranged from 2.2 ± 1.0 mg/kg to 3.2 ± 1.1 mg/kg, that of thorium ranged from 4.0 ± 0.5 mg/kg to 5.7 ± 1.7 mg/kg, while potasium presented in % by weight ranged from 0.4 ± 0.2 to 1.3 ± 0.3 in all the locations. The overall mean concentrations of these radionuclides are comparable to values from other locations around the world. The XRF analysis revealed 4 major elements and 11 minor or trace elements present in the clay samples. The distribution of the various major and trace elements in all the sampling sites do not follow any systematic trend but vary from point to point. To assess the level of contamination and the possible anthropogenic impact in the clay soils, the enrichment factor (EF) and the geoaccumulation index (Igeo) were estimated for some potential hazardous elements. The results indicate that Cu, Zn, Ni and Mn have EF < 2 indicating minimal or no enrichment while Pb is moderately enriched in all the locations.

Assessment of spatial distribution and potential ecological risk of the heavy metals in relation to granulometric contents of Veeranam lake sediments, India

The contents and spatial distributions of heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) have been studied in surface sediments of Veeranam lake, Tamilnadu, India. Heavy metal contents are higher in open water area (limnetic zone) (OWA) than other two regions such as inflow river mouth (littoral zone) (IFR) and outflow river mouth region (OFR). Present metal contents are compared with both background and toxicological reference values. The comparative results suggest that the present metals except Cd and Pb create an adverse effect on the aquatic ecosystems associated with this lake. The Pollution Load Index (PLI) and Potential Ecological Risk (PER) are calculated and calculated PLI values (range: 1.18-4.09 with an average of 2.03) show that the present sediments are polluted significantly and these values are higher in OWA region. From the PER values, each single element has low potential ecological risk. However, Cd shows higher ecological risk. The comprehensive PER index of the sediments shows moderate degree. The magnetic susceptibility is higher in OWA region. Granulometric analysis confirms that the silt is major content. Multivariate Statistical analyses (Pearson Correlation, Cluster and Factor analysis) were carried out and obtained results suggested that the heavy metals in present lake have complicated contamination sources or controlling factors and the heavy metals such as Cr, Cu, Ni and Zn may be incorporated in magnetic minerals which are presented in silt grains. Also it shows that the role of silt is incorporating the cations on their surface and raising the level of magnetic susceptibility and heavy metal contents. The present study recommends that the heavy metal levels are unlikely to cause additional adverse health risks to the aquatic ecosystem associated with this lake.

Heavy metals and polycyclic aromatic hydrocarbons: pollution and ecological risk assessment in street dust of Tehran

50 street dust samples from four major streets in eastern and southern Tehran, the capital of Iran, were analyzed for metal pollution (Cu, Cr, Pb, Ni, Cd, Zn, Fe, Mn and Li). Hakanson's method was used to determine the Risk Index (RI) and ecological risks. Amongst these samples, 21 were also analyzed for polycyclic aromatic hydrocarbons (PAHs). Correlation, cluster and principal component analyses identified probable natural and anthropogenic sources of contaminants. The dust had elevated concentrations of Pb, Cd, Cu, Cr, Ni, Zn, Fe and PAHs. Enrichment factors of Cu, Pb, Cd and Zn showed that the dust is extremely enriched in these metals. Multivariate statistical analyses revealed that Cu, Pb, Zn, Fe and PAHs and, to a lesser extent, Cr and Ni have common anthropogenic sources. While Mn and Li were identified to have natural sources, Cd may have different anthropogenic origins. All samples demonstrated high ecological risk. Traffic and related activities, petrogenic and pyrogenic sources are likely to be the main anthropogenic sources of heavy metals and PAHs in Tehran dust.

Spatial distribution and multiple sources of heavy metals in the water of Chaohu Lake, Anhui, China

In this study, a survey for the spatial distribution of heavy metals in Chaohu Lake of China was conducted. Sixty-two surface water samples were collected from entire lake including three of its main river entrances. This is the first systematic report concerning the content, distribution, and origin of heavy metals (Cu, Cr, Cd, Hg, Zn, and Ni) in the Chaohu Lake water. The results showed that heavy metals (Cu, Cr, Zn, and Ni) concentrations in the estuary of Nanfei River were relatively higher than those in the other areas, while content of Hg is higher in the southeast lake than northwest lake. Moreover, Cd has locally concentration in the surface water from the entire Chaohu Lake. The heavy metal average concentrations, except Hg, were lower than the cutoff values for the first-grade water quality (China Environment Quality Standard) which was set as the highest standard to protect the social nature reserves. The Hg content is between the grades three and four water quality, and other heavy metals contents are higher than background values. The aquatic environment of Chaohu Lake has apparently been contaminated. Both the cluster analysis (CA) and correlation analysis provide information about the origin of heavy metals in the Lake. Our findings indicated that agricultural activities and adjacent plants chimneys may contribute the most to Cd and Hg contamination of Chaohu Lake, respectively.

Spatial distribution and human contamination quantification of trace metals and phosphorus in the sediments of Chaohu Lake, a eutrophic shallow lake, China

Distinguishing and quantifying anthropogenic trace metals and phosphorus accumulated in sediment is important for the protection of our aquatic ecosystems. Here, anthropogenic proportion and potential sources of trace metals and phosphorus in surface sediments of Chaohu Lake were evaluated based on the exhaustive geochemical data. The analysis shows that concentrations of major and trace metals, and phosphorus, displayed significant spatial diversity and almost all elements were over the pre-industrial background value, which should be related to the variations of sediment composition partially. Therefore, conservative element normalization was introduced and calculated enrichment factors (EFs) of the elements were referenced highlighting the human contamination. EFs of the major and trace metals, except Zn, Pb, and Cu, were all nearly 1.0, indicating the detrital origin. The EFs of Zn, Pb, Cu and phosphorus were 1.0-10.4, 1.0-3.8, 1.0-4.9, and 1.0-7.6, respectively, showing moderate to significant contamination. Higher EFs of Zn, Pb and Cu occurred in the mouth areas of Nanfei River and Zhegao River, and they decreased to the lake center in the northwest and northeast lake areas, respectively. We deduced that anthropogenic Zn, Pb, and Cu were mainly from urban and industrial point sources and the non-point sources of atmospheric deposition contributed little to their contamination. The EFs of phosphorus showed similar spatial degradation with that of Zn, Pb, and Cu. Moreover, higher EFs (>1) of phosphorus also occurred in other areas adjacent to the river mouths besides Nanfei River and Zhegao River. This indicated that the non-point agricultural source may also be responsible for the contamination of phosphorus in Chaohu Lake in addition to the urban sewage sources. Anthropogenic phosphorus was mainly concentrated in the speciation of NaOH-P, which had higher potential biological effects than the detrital proportion. Concentrations of Zn, Pb and Cu surpassed the threshold effect concentrations (TEC) of consensus-based sediment quality guidelines of freshwater ecosystems, especially in the contaminated northwest area of Chaohu Lake. This highlighted the contributions of anthropogenic contamination to the elevated potential biological effects of trace metals. Though there had been no obvious human contamination of Cr and Ni in Chaohu Lake, concentrations were all over the TECs, which may be due to higher background levels in the parent materials of soils and bedrocks in Chaohu Lake catchment.