Concentrations Of Most Heavy Metals Research Articles

Predictions of heavy metal concentrations by physiochemical water quality parameters in coastal areas of Yangtze river estuary

Due to the degradation-resistant and strong toxicity, heavy metals pose a serious threat to the safety of water environment and aquatic ecology. Rapid acquisition and prediction of heavy metal concentrations are of paramount importance for water resource management and environmental preservation. In this study, heavy metal concentrations (Cr, Ni, Cu, Pb, Zn, Cd) and physicochemical parameters of water quality including Temperature (Temp), pH, Oxygen redox potential (ORP), Dissolved oxygen (DO), Electrical conductivity (EC), Electrical resistivity (RES), Total dissolved solids (TDS), Salinity (SAL), Cyanobacteria (BGA-PE), and turbidity (NTU) were measured at seven stations in the Yangtze river estuary. Principal Component Analysis (PCA) and Spearman correlation analysis were employed to analyze the main factors and sources of heavy metals. Results of PCA revealed that the main sources of Cr, Ni, Zn, and Cd were steel industry wastewater, domestic and industrial sewage, whereas shipping and vessel emissions were typically considered sources of Pb and Cu. Spearman correlation analysis identified Temp, pH, ORP, EC, RES, TDS, and SAL as the key physicochemical parameters of water quality, exhibiting the strongest correlation with heavy metal concentrations in sediment and water samples. Based on these results, multiple linear regression as well as non-linear models (SVM and RF) were constructed for predicting heavy metal concentrations. The results showed that the results of the nonlinear model were more suitable for predicting the concentrations of most heavy metals than the linear model, with average R values of the SVM test set and RF test set being 0.83 and 0.90. The RF model showed better applicability for simulating the concentration of heavy metals along the Yangtze river estuary. It was demonstrated that non-linear research methods provided efficient and accurate predictions of heavy metal concentrations in a simple and rapid manner, thereby offering decision-making support for watershed managers.

Ecological Responses of Soil Bacterial Communities to Heavy Metal Contamination Surrounding a Typical Coal-based Industrial Region

Microbial communities in the soil might be affected by heavy metal contamination caused by anthropogenic activities associated with the coal-based industry. This study analyzed the differences in soil physicochemical properties, heavy metal concentrations, and enzyme activities surrounding different coal-based industrial fields(coal mining industry, coal preparation industry, coal-based chemical industry, and coal-fired power industry) in Shanxi Province, North China. Moreover, soil samples from farmland and parks away from all the industrial plants were collected as references. Based on the 16S rRNA high-throughput sequencing, we identified the composition of soil bacterial communities. Spearman correlation and redundancy analyses were used to explore the relationships between soil bacterial communities and environmental factors. The results showed that the concentrations of most heavy metals were greater than the local background values, particularly for As, Pb, and Cd, but they did not exceed the risk screening values of Soil Environment Quality:Risk Control Standard for Soil Contamination of Agriculture Land(GB 15618-2018). There were significant differences in soil cellulase and alkaline phosphatase activities among sampling fields. Actinobacteria was the predominant bacterial phyla, with the highest relative abundance surrounding the coal-based chemical plants, followed by Proteobacteria. The soil bacterial communities were significantly affected by Cd, total carbon, total nitrogen, and alkaline phosphatase activity. This study could provide a foundation for the ecological remediation of the coal-based industrial region in the future.

Extreme rainstorm reshuffles the spatial distribution of heavy metals and pollution risk in sediments along the mangrove tidal flat

Mangroves as typical blue carbon ecosystems exhibit a high level of heavy metal accumulation capability. In this study, we investigated how extreme rainstorm effects the spatial variability and pollution risk of sediment heavy metals (i.e., Fe, Mn, Cr, Cu, Zn, Cd, Pb, As and Hg) at different compartments of a typical tidal flat, including the bare mudflat, mangrove zone, and tidal creek in Shenzhen Bay, China. The results showed that the extreme rainstorm can change the sediment particle size, which further regulated the spatial distribution, and source-sink pattern of heavy metals. Due to the strong rainstorm flushing, the concentrations of most heavy metals increased toward the sea and the comprehensive pollution level increased by 8.3 % after the extreme rainstorm. This study contributes to better understanding of how extreme rainstorm regulates heavy metal behavior in mangrove sediments to achieve sustainable development of mangroves under the pressures of extreme weather events.

Ecological Responses of Soil Microbial Communities to Heavy Metal Stress in a Coal-Based Industrial Region in China.

Soil microorganisms play vital roles in ecosystem functions, and soil microbial communities might be affected by heavy metal contamination caused by the anthropogenic activities associated with the coal-based industry. This study explored the effects of heavy metal contamination on soil bacterial and fungal communities surrounding different coal-based industrial fields (the coal mining industry, coal preparation industry, coal-based chemical industry, and coal-fired power industry) in Shanxi province, North China. Moreover, soil samples from farmland and parks away from all the industrial plants were collected as references. The results showed that the concentrations of most heavy metals were greater than the local background values, particularly for arsenic (As), lead (Pb), cadmium (Cd), and mercury (Hg). There were significant differences in soil cellulase and alkaline phosphatase activities among sampling fields. The composition, diversity, and abundance of soil microbial communities among all sampling fields were significantly different, particularly for the fungal community. Actinobacteria, Proteobacteria, Chloroflexi, and Acidobacteria were the predominant bacterial phyla, while Ascomycota, Mortierellomycota, and Basidiomycota dominated the studied fungal community in this coal-based industrially intensive region. A redundancy analysis, variance partitioning analysis, and Spearman correlation analysis revealed that the soil microbial community structure was significantly affected by Cd, total carbon, total nitrogen, and alkaline phosphatase activity. This study profiles the basic features of the soil physicochemical properties, the multiple heavy metal concentrations, and the microbial communities in a coal-based industrial region in North China.

Mineral phase transition characteristics and its effects on the stabilization of heavy metals in industrial hazardous wastes incineration (IHWI) fly ash via microwave-assisted hydrothermal treatment

Toxic heavy metals in industrial hazardous waste incineration (IHWI) fly ash can be effectively stabilized by using microwave-assisted hydrothermal technology. However, few works have focused on the relationship between mineralogical conversion and stability of heavy metals of fly ash during hydrothermal process. This study investigated the effect of mineral phase transition process on the stabilization and migration behavior of heavy metals in IHWI fly ash using coal fly ash as silicon‑aluminum additive. Mineral composition analysis reveals that after microwave-assisted hydrothermal treatment (MAHT) of IHWI fly ash, zeolite-like minerals (e.g., tobermorite, katoite and sodalite), secondary aluminosilicate minerals (e.g., prehnite and anorthite) and other newly-formed minerals (e.g., wollastonite, pectolite and larnite) were found. The leaching concentrations of heavy metals (Cr, Ni, Cu, Zn, Cd and Pb) in IHWI fly ash decrease sharply after MAHT with the most obvious decreases in Cu, Pb and Zn. Spearman correlation analysis show significantly negative correlation between the content of zeolite-like minerals and the leaching concentrations of most heavy metals (e.g., Ni, Cu, Zn, Cd and Pb). These results suggest that the immobilization effects of heavy metals in IHWI fly ash can be effectively enhanced by promoting the formation of zeolite-like minerals during the MAHT. This study is expected to further promote the development of IHWI fly ash harmless treatment technology.

Improving the efficiency of machine learning in simulating sedimentary heavy metal contamination by coupling preposing feature selection methods

Sediment cores were collected from Taihu Lake in China. The chronology was determined by radionuclide. Heavy metals and magnetic properties of each core slice were assessed, respectively. The concentrations of most heavy metals in sediments surged at 20 cm from the surface, accompanying the increase in the concentrations of single-domain magnetic particles. This may be resulted from the influence of anthropic activities on the lake's environment after the 1970s. Two feature selection methods, random forest (RF) and maximal information coefficient (MIC), were combined with support vector machine (SVM) model to simulate heavy metals, with the inclusion of selected magnetic and physicochemical parameters. Compared with the modeling results obtained with the full set of parameters, a reasonable simulation performance was obtained with RF and MIC. RF performed better than MIC by increasing the R2 of simulation models for Cd, Cr, Cu, Pb, and Sb. For heavy metals with high ecological risks (As, Cd, Cr, Hg, Pb, Sb), the correlation coefficients for observed and predicted data ranged from 0.73 to 0.97 with only 14–27% of the parameters selected by RF as input variables. The RF-RBF-SVM enabled heavy metal predictions based on the magnetic properties of the lake sediments.

Geochemical accumulation and source tracing of heavy metals in arable soils from a black shale catchment, southwestern China.

Heavy metal enrichment in soils has been linked to the weathering of lithologies with high geochemical backgrounds, such as black shale. Therefore, this study conducted a typical sampling of surface soils in a black shale catchment in southwestern China to characterize the accumulation and sources of the heavy metals As, Cd, Co, Cr, Cu, Ni, Pb, Zn, Mo and Tl. Elevated concentrations of most heavy metals in the soils underlain by black shale are determined to exceed the regional soil background values, even the risk screening values, especially for Mo, As and Cd. Sequential extraction analysis, together with previous results, reveals that most heavy metals in soils are mainly bound in the residual fraction (> 65 %) as a result of the fixation of stable aluminosilicates (e.g., clay minerals). In contrast, Cd mainly occurs in relatively labile proportions as exchangeable (24.42 %), carbonate (24.48 %) and Fe/Mn oxide fractions (26.60 %) due to the non-specific adsorption of soil colloids and the precipitation of carbonates and Fe/Mn oxides. Pb isotopic tracing and APCS/MLR receptor model suggest that heavy metals in the urban surface soils (SG1) have a mixed source of black shale weathering, vehicle exhaust and agricultural input, while heavy metals in the rural surface soils (SG2) are a geogenic source of black shale weathering. Overall, this study provides new insights into contamination management, land use planning and health risk assessment in regions with high geochemical backgrounds.

High nitrogen addition after the application of sewage sludge compost decreased the bioavailability of heavy metals in soil

Nitrogen (N) fertilizer is highly significant in agricultural production, but long-term N addition causes changes in quality indicators, such as soil organic matter (SOM), thus affecting the absorption and accumulation of organic pollutants. Therefore, paying more attention to organic fertilizers in the development of green agriculture is necessary. However, the accumulation of heavy metals (HMs) contained in organic fertilizers (especially sewage sludge compost (SSC)) in the soil can cause environmental contamination, but how this cumulative reaction changes with the long-term N addition remains unclear. Here the SSC impact on the bioavailability of five typical HMs (cadmium–Cd, chromium–Cr, copper–Cu, lead–Pb and arsenic–As) in the soil-plant system before and after SSC application was demonstrated through a field study in soils with different application rates of 0, 100 and 300 kg N ha−1yr−1, respectively. Our results showed that SSC application increased the concentration of most HMs in soil profiles and plant systems (wheat roots and grains), but the accumulation rate of HMs and most bioaccumulation values (BAC–bioaccumulation coefficient and BCF–bioconcentration factor) in plant systems were both lower in high-N addition soil than that in the low-N group. Moreover, speciation distribution results further indicated that SSC application increased the LB (liable available form, including F1–water soluble, F2–ion exchangeable, and F3–bound to carbonates) form of HMs and decreased the PB (potentially available form, including F4–humic acids and F6–fraction bound to organic matter) form of HMs in high-N addition soil, respectively. Those results suggested that HM bioavailability in high-N addition soil was lower than that in low-N addition soil when applied with SSC. Overall, this study found that increasing soil N content can inhibit the bioavailability of HMs when applying SSC, providing suggestions for optimizing the trialability and risk assessment of SSC application.

Assessing the Impact of a Hydropower Plant on Changes in the Properties of the Sediment of the Bystrzyca River in Poland

This study aimed to assess the impact of a hydropower plant (HP) on the Bystrzyca River (left tributary of the Odra River, Poland) on selected parameters of the bottom sediment within this hydrotechnical structure. The following parameters were examined as part of the analyses: particle size distribution, pH, electrical conductivity (EC), and concentrations of Cd, Cu, Cr, Ni, Pb and Zn. Field studies were carried out upstream and downstream of the HP and at reference points. In addition, the risk of heavy metals in aquatic organisms was assessed using an ecotoxicological method. Based on the Wilcoxon signed-rank test, it was found that the HP influenced all of the parameters tested, except pH. Comparing the points closest to and downstream of the HP, an increase in the average grain diameter of D50(on average by 750%), and a decrease in the concentrations of most heavy metals: Ni (271%), Zn (216%), Cu (163%), Cr (83.0%), and Cd (74.2%), was observed. The ecotoxicological classification of heavy metal concentrations in sediments indicates, in most cases, little or no impact on aquatic organisms; the values of Ni and Zn in some samples upstream of the HP are exceptions, where remediation using synthetic zeolites, metal accumulation plants, or by electrokinetic methods, is necessary. Fine-grained fractions dominate the clays and sandy clays upstream of the hydropower plants, while sands, sandy clay loams, or sandy clays are dominated downstream. Frequent occurrence of skeletal fractions (>2.0 mm) was observed downstream, i.e., an average of 23.30% in each sample compared to 1.82% upstream of the HP, which is mainly due to greater anthropogenic pressure, especially tourism. The dominance of fine-grained fractions upstream of the HPs favors the accumulation of metals due to the high sorption capacity of these fractions. When comparing the analyzed groups of points, the average pH values are arranged in the following sequence: upstream HP (U) > downstream HP (D) > reference points (R), while EC has opposite values (i.e., U < D < R). This study may support sustainable sediment management and may allow for the development of recommendations related to the rational management of HPs.

Prediction of heavy metals in airborne fine particulate matter using magnetic parameters by machine learning from a metropolitan city in China

This study explored a new statistical method for predicting airborne heavy metals using environmental magnetism. Samples of fine particulate matter (PM2.5) were collected for 1 year in a typical Chinese megacity. The annual average PM2.5 concentration was 60.17 μg/m3 and approximately 32.02% of daily PM2.5 concentrations exceeded the Chinese National Ambient Air Quality Standard guideline value. Concentrations of most heavy metals were higher in winter and lower in summer. The hazard index value, which reflects the health risk associated with exposure to potentially toxic metals via inhalation, was 0.506 and below the safe limit. The integrated carcinogenic risk was 1.64 × 10−5 for adults and 4.10 × 10−6 for children. Magnetic analysis indicated that soft low-coercivity ferrimagnetic minerals were the main magnetic material which pseudo single domain, or a mixture of single domain and multidomain magnetite dominated in PM2.5. Metal concentrations were simulated by using atmospheric pollutants, meteorological variables or magnetic parameters by support vector machine or backpropagation artificial neural network models; the former model outperformed the latter. Predictions for As, Cd, Pb, and Mn were better than for other metals with training and validation R values both >0.8, whereas relatively poor for Al, Co, and Cr. When magnetic parameters were included in the models, the prediction performance for all metals was improved; however, greater improvement was obtained for Cu, Cr, Fe, Ti, and V. Environmental magnetism analyses combined with machine learning have potential for efficient evaluation of airborne heavy metals.

Spatial distribution and ecological risk assessment of heavy metals in karst soils from the Yinjiang County, Southwest China.

BackgroundSoil heavy metals (HMs) under different land-use types have diverse effects, which may trigger the ecological risk. To explore the potential sources of HMs in karst soils, the spatial distribution and geochemical behavior of HMs based on different land-use types are employed in this study.MethodsSoil samples (n = 47) were collected in three suites of karst soil profiles from the secondary forest, abandoned cropland and shrubland in Yinjiang, Southwest China. The concentrations of Ni, Mn, Cr, Pb, Cd and Mo were determined to give a comprehensive understanding of the possible sources of these HMs and evaluate the potential ecological risk in Yinjiang County.ResultsThe mean concentrations of HMs in all profiles followed the same order: Mn > Cr > Ni > Pb > Mo > Cd. Meanwhile, the concentrations of most HMs roughly increased with the depth. Additionally, the concentrations of HMs were mostly correlated with soil pH and SOC, rather than with clay and silt proportions. By contrast, with the enrichment factors (EF), geo-accumulation (Igeo) and potential ecological risk index (PERI) of HMs in soil under different land-use types, the results indicated that these HMs exhibited non-pollution (Igeo < 0) and no ecological risk (PERI < 30) to human health in soils of Yinjiang County.ConclusionsThe distribution of HMs is dominated by weathering in the karst area, and the effects of agricultural inputs on the enrichment of soil HMs in Yinjiang County are limited. This further state that the arrangement of the local agricultural structure is reasonable.

A comprehensive exploration on distribution, risk assessment, and source quantification of heavy metals in the multi-media environment from Shaying River Basin, China

Comprehensively understand the distribution of pollutants in the multi-media environment at basin scale is of major importance to the ecological risk assessment and pollution control. In this study, multi-media contamination characteristics of eight heavy metals in the water, soil, and sediment from the Shaying River Basin of China have been analyzed to probe their ecological risks and potential sources. Results revealed that heavy metal concentrations in pore water were higher than those in surface water. While the mean concentrations of most heavy metals increased follow the order of bankside soil (BS)<water-level-fluctuating zone soil (WLFZS)<sediment. The WLFZ was an important transition zone between the BS and sediment for pollutant exchange. The mean heavy metal concentrations in surface water were all below their corresponding water quality standards except Hg. Whereas the mean concentrations of Cr, Ni, Zn, Cd, and Hg in BS, WLFZS, and sediment exceeded their corresponding background values. The assessment results of pollution and risks indicated that Hg and Cd posed the highest potential risks in each medium. Furthermore, according to the factor analysis and PMF model, six potential sources were identified, in which agricultural, fuel combustion, and industrial sources were the dominant anthropogenic sources, accounting for 23.84%, 17.43%, and 14.25% of the total contribution.

Seasonality of surface water contamination by heavy metals in the lower Enyong creek, s.e. Nigeria)

Surface water samples from three locations in the Lower Enyong Creek, S.E. Nigeria were sampled over six months i.e June to October (wet season) and November in dry season for heavy metals such as Cd, Mn, Fe, Cu, Ni, Pb, Zn, Cr) using Atomic absorption spectroscopic method. Some specific physicochemical characteristics, such as temperature, hardness, alkalinity, salinity, TDS, TSS, pH and conductivity which are known to influence the interactions and dynamics of trace metal loads in water bodies were also determined. The result of the analysis indicated significant monthly variation of these parameters for the six months. Monthly summary statistics revealed a few seasonal patterns that echoed the hydrologic regime. During the short dry season in August–September period, all the sampled stream channels had lower levels of Cd, Ni, Zn, Cu Cr, Pb and Fe. Salinity, for instance, correlated strongly (p&lt;0.05) with Cu (0.70); Cr (0.56); Ni (0.72); nitrate (0.61) and Na (0.49). However, the concentrations of most heavy metals were low, while Zn content was higher than the WHO standard for surface water which indicated significant contamination by Zn in the water body.

Earthworm Eisenia fetida potential for sewage sludge amended soil valorization by heavy metal remediation and soil quality improvement

Sewage sludge reuse in agriculture is increasing, however it can be an important route for contaminants to enter the environment. The aim of this study was to evaluate earthworm Eisenia fetida capability to reduce heavy metal content in the sewage sludge (SS) amended soil and increase soil fertility in terms of soil nutrients content. Adult earthworms were introduced into aged SS amended soil (0–200 Mg ha-1) and left for 65 days. Earthworms have stabilized soil pH and accelerated organic matter mineralization. The concentrations of most heavy metals during the vermiremediation sharply decreased, K and Mg decreased to a moderate extent, whereas Ca content has increased. The highest removal efficiency was detected for Ni, Co and Mn (> 80%), bioconcentration factors were as follows Zn > Co > Cu > Ni > Mn > Cr. The content of major nutrients (S, P) was substantially higher compared to the initial values. The most efficient remediation and soil quality improvement was achieved under the doses of 25–50 Mg ha-1. Higher (≥ 100 Mg ha-1) doses might restrict this technique application because of earthworm mortality and retarded growth. Overall, the study shows that vermiremediation might be a sustainable technique for ecological stabilization of SS amended soil and converting to usable for agricultural needs.

Geochemistry of Dissolved Heavy Metals in Upper Reaches of the Three Gorges Reservoir of Yangtze River Watershed during the Flood Season

Dissolved heavy metals (HMs), derived from natural and anthropogenic sources, are an important part of aquatic environment research and gain more international concern due to their acute toxicity. In this study, the geochemistry of dissolved HMs was analyzed in the upper Three Gorges Reservoir (TGR) of the Yangtze River (YZR) watershed to explore their distribution, status, and sources and further evaluate the water quality and HM-related risks. In total, 57 water samples were collected from the main channel and tributaries of the upper TGR. The concentrations of eight HMs, namely V, Ni, Cu, Zn, As, Mo, Cd, and Pb, were measured by ICP-MS. The mean concentrations (in μg/L) of eight HMs decreased in the order: As (1.46), V (1.44), Ni (1.40), Mo (0.94), Cu (0.86), Zn (0.63), Pb (0.03), and Cd (0.01). The concentrations of most HMs were 1.4~8.1 times higher than that in the source area of the YZR, indicating a potential anthropogenic intervention in the upper TGR. Spatially, the concentrations of V, Cu, As, and Pb along the main channel gradually decreased, while the others were relatively stable (except for Cd). The different degrees of variations in HM concentrations were also found in tributaries. According to the correlation analysis and principal component (PC) analysis, three PCs were identified and explained 75.1% of the total variances. combined with the concentrations of each metal, PC1 with high loadings of V, Ni, As, and Mo was considered as the main contribution of human inputs, PC2 (Cu and Pb) was primarily attributed to the contribution of mixed sources of human emissions and natural processes, and Zn and Cd in PC3 were controlled by natural sources. Water quality assessment suggested the good water quality (meeting the requirements for drinking purposes) with WQI values of 14.1 ± 3.4 and 11.6 ± 3.6 in the main channel and tributaries, respectively. Exposure risk assessment denoted that the health effects of selected HMs on the human body were limited (hazard index, HI &lt; 1), but the potential risks of V and As with HI &gt; 0.1 were non-negligible, especially for children. These findings provide scientific support for the environmental management of the upper TGR region and the metal cycle in aquatic systems.

Are heavy metals in urban garden soils linked to vulnerable populations? A case study from Guelph, Canada

With increasing population, there is growing concern for food security in urban areas. Though, urban gardening has gained popularity, several studies have found higher concentrations of contaminants in urban soils, especially heavy metals, often at toxic levels, which pose a potential risk for human health. Moreover, heavy metal polluted sites have been strongly associated with areas populated by low-income families, newcomers and racial minorities. In this study, heavy metals in the soils of community gardens in the city of Guelph, ON were examined as a case study and their relationship with vulnerable populations. We analyzed soil samples at two depths for a range of heavy metals and characterized their spatial patterns to see if they were related to disadvantaged communities. We estimated the pollution levels using two index-based approaches and assessed their potential risk for human health, although concentrations of most heavy metals were below the limits established by Canadian regulations, metals like Cd, Pb, Se and Zn exhibited a mild degree of pollution, whereas As exhibited a severe degree. Their association with vulnerable populations were weak, but hotspots were mainly located in low-income areas. This case study provides scientific evidence that could help to expand our understanding around the interconnection between pollution and poverty/racial inequality. Also the importance of generating strategies for the protection of human health and sustainable soil management practices in urban areas where food for human consumption is grown.

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

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

Sediment record of heavy metals over the last 150 years in Northeast China: implications for regional anthropogenic activities.

Evidence from terrestrial sedimentary heavy metals record is a robust indicator of anthropogenic activity changes. Heavy metals and particle sizes in 210Pb-dated sediment cores extracted from Hulun and Chagan lakes were measured to reconstruct the sediment record and evaluated health risk of heavy metals in the last 150 years in Northeast China. In general, the particle size of Hulun Lake was finer with more contents of clay than Chagan Lake, while the concentrations of most heavy metals in Hulun Lake was lower. Prior to the 1970s, significant positive correlations between most heavy metals and clay, indicating that that they were likely co-transported and both lakes were dominated by natural inputs. The two records showed significant increases in concentrations of heavy metals between 1970s and 1990s, which were associated with recent anthropogenic activities derived from principal component analysis of clay and heavy metals. Specifically, the exploitation of mineral resources and traffic source in the Hulun Lake, and the emissions of pesticides and fertilizers from agricultural activity, and the combustions of coal and fossil fuels from industrial activity in the Chagan Lake. Since 1990s, natural processes was the main source of heavy metals in Hulun Lake due to the environmental protection policy, while emissions of industrial, agricultural and domestic sewage were still the main source in Chagan Lake. Overall carcinogenic risks caused by single heavy metal elements determined for the two lakes were considered to be acceptable. However, Cr was associated with a risk for children across since 1970s which should be paid more attention.

The spatial distribution of soil heavy metals and ecological restoration of Datong Abandoned Coal Mine in Huainan City

Based on laboratory analysis of soil samples collected from abandoned coal mine in Datong area, content of heavy metals in the soils was monitored and the soils were evaluated for heavy metal pollution. The spatial distribution of heavy metals was study with means of Kriging method by under ArcGIS environment in the abandoned coal mine in Huainan area. The results show: (1) the content of 5 types of heavy metals( Hg, Cd, Cr, Pb, Cu) were all higher than Huainan area background value of soil elements, among of these heavy metals, the enrichment of Cd was higher and polluted quite seriously; the enrichment of Hg, Cr, Pb and Cu was lower, and polluted lightly comparatively. (2) The coal mine waste rock pile and abandoned chemical plant were the main pollution sources. (3) The heavy metal concentrations and space distribution were mainly affected coal mine waste rock pile, and abandoned chemical plant. (4) Positive correlation between concentrations of most heavy metals was significant, and there is a certain relationship between concentrations of heavy metals and organic matter, nitrogen, available phosphorus. On the basis of the above research, some countermeasures were put forward for ecological restoration in Datong abandoned coal mine.

IMPACTS OF URBAN DEVELOPMENT ON AN OXBOW LAKE IN THE AMAZON REGION: LANDSCAPE AND GEOCHEMICAL EVIDENCE

Amapá Lake is an abandoned meander of the Acre River, the margins of which are occupied by agricultural settlements, smallholdings, fish farms and dirt roads. This paper discusses the impact of this occupation on the lake area based on field data and physical-chemical and elementary chemical analyses of the lake and river waters. The strong physical changes in the lake landscape have impacted the quality of its water. During the dry season (low water), when the temperature of the water reaches 30-34ºC, there is a proliferation of green algae and in the area affected by fish farms and smallholdings there is an increase in total dissolved solids, electrical conductivity, and transparency, while turbidity and total suspended solids become more concentrated during the flood season. The anthropogenic impact is also indicated by the higher levels of ammonia, chlorides, bromides, and phosphates in the water. However, the concentrations of dissolved metal ions are all consistent with those found in the Acre River, and other muddy water lakes and rivers in the Amazon basin, reflecting the mineralogy of the suspended material. The concentrations of most heavy metals (Pb, Cu, (Zn), Cd and Hg) are below 0.01 mg L-1, while that of Hg (0.006 mg L-1) is above the recommended limits for human consumption. Overall, the results of the study indicate that Amapá Lake is suffering ongoing impacts (physical and chemical) from urban development, which are mitigated by the periodic flooding of the river. Key words: Urban expansion, Environmental impacts, Waters, Heavy metals.