Sources Of Heavy Metal Pollution Research Articles

Assessment of Heavy Metal Pollution in the Surface Water of the Doi Canal, the Cho Dem and Ben Luc Rivers, Vietnam

The Doi Canal and the Cho Dem and Ben Luc Rivers play the key roles in irrigation, navigation and ecological restoration. It is important to clearly identify the pollution, influencing factors, ecological risks and possible sources of heavy metals in the surface water of this river system. The surface water of 7 sampling sites was collected over 7 consecutive periods from April 2019 to October 2021. Each surface water sample was analyzed for 9 heavy metals including Fe, Mn, Cr, Zn, Cu, Pb, Cd, Ni, As. Sampling and sample handling techniques were performed based on the Standard Methods for the Examination of Water and Wastewater. Among all nine heavy metals examined in the study area, the concentrations of Fe (1.00 ¸ 5.06 mg/L) and Mn (0.14 ¸ 0.28 mg/L) were the highest and the concentrations of Cr, Cd and As were below the lower limit of detection. The results showed that the average Fe and Mn contents both exceeded the permissible thresholds of the National technical regulation on surface water quality (QCVN 08-MT: 2015/BTNMT). Additionally, the content of Fe, Mn, Zn, Cu, Pb, Ni did not meet the water quality standards for aquatic life (United State Environmental Protection Agency). Keywords: Distribution; Heavy metal pollution; River; Surface water; Water quality protection.

Heavy metals in coral reef sediments of Kavaratti Island, India: An integrated quality assessment using GIS and pollution indicators

The present study aims to document the contamination levels and ecological risks of heavy metals in the sediments of Kavaratti lagoon, India. A total of 15 sediment samples were collected for the analysis of Al, Pb, Cd, Cu, Cr, Mn, Ni and Zn. The decreasing trend of heavy metals was observed in the lagoon sediment as Pb > Zn > Al > Mn > Ni > Cr > Cd > Cu. The Geo-accumulation index (Igeo) results indicate that Cu, Cr, Mn, Ni and Zn were uncontaminated, while Cd was strong to extremely contaminated and Al and Pb were moderately contaminated. The enrichment factors (EF) of Cd and Pb range from moderate to extremely high (EF > 1) indicating that they have anthropogenic origin on Kavaratti Island. The Contamination factor (Cf) indicated that Cd, Pb and Al belong to a high risk of contamination (Cf > 6). The pollution load index (PLI) value near one suggested that a moderate level of pollution occurs in the study area. The modified degree of contamination (mCd) shows that Al, Cd and Pb have an ultra- higher degree of contamination (mCd ≤ 32). The potential ecological risk (RI) index confirmed that Pb and Cd have considerable to the serious thread of ecological risk (RI > 600). Additionally, multivariate statistical analysis and pollution indexes showed that the Kavaratti lagoon is moderate to considerably polluted by heavy metals. Diesel-based power generation, activities related to shipping, untreated sewage, fishing and tourism activities are the main anthropogenic sources of heavy metal pollution on Kavaratti Island.

Short−Term Assessment of Heavy Metals in Surface Water from Xiaohe River Irrigation Area, China: Levels, Sources and Distribution

The aims of this study were to determine the pollution characteristics of heavy metals and their potential harm to human health in the surface water of agricultural irrigation areas, China, over a short term. In this study, Cu, Zn, Pb, Hg, Ni, Cr, Cd, and As in surface water of the Xiaohe River irrigation area were detected and analyzed. The results showed that the concentrations of Pb, Hg, Ni, Cr, Cd, and As exceeded the national environmental quality standard for surface water in varying degrees. The concentrations of heavy metals in surface water in October were significantly lower than that in November and December due to the impact of extreme precipitation events. Point source pollution (industrial sewage, etc.) was the main factor affecting the spatial distribution of heavy metals. The main source of heavy metals in October was domestic sewage. Domestic sewage and industrial sewage were the main sources of heavy metals in November. The sources of heavy metals in surface water in December were relatively diverse, and industrial sewage was the main source. The temporal variation of heavy metal pollution sources changed significantly. Industrial sewage was the main pollution source of heavy metals in surface water in the study area. The impact of urban domestic sewage and agricultural activities cannot be ignored. The health risk of heavy metals in surface water mainly depends on Cr, Cd, and As. Policy recommendations were also proposed for better control of heavy metal pollution in the surface water of river ecosystems involving agricultural irrigation areas.

Pollution characteristics and risk assessment of heavy metals in the water and surface sediments of Wulungu Lake, Xinjiang China

ABSTRACT Wulungu Lake is the second largest lake and the second largest fishery base in Xinjiang, but there are few studies on heavy metal pollution in water environment. In order to explore the characteristics and sources of heavy metal pollution in the water environment of Wulungu Lake, the distribution characteristics, ecological risks and pollution sources of 8 heavy metals (Cr, Cu, Cd, Zn, Ni, Pb, Hg and As) in water and sediments of 13 sampling points of Wulungu Lake were analyzed. Geological accumulation index method and potential ecological hazard index method show that Hg has a strong potential ecological risk, which leads to a high potential ecological risk in Wulungu Lake. The water quality of Wulungu Lake is good, but we need to pay attention to the health risk of as. Multivariate statistical analysis shows that Cu, Cd, Zn, Ni and Pb in the water body of Wulungu Lake are affected by the discharge of mining or enterprise wastewater. Hg and Cr may come from the use of fertilizer in farmland. Cr, Cu, Zn, Ni and As in surface sediments are mainly affected by regional geochemical characteristics, while Cd, Pb and Hg are also affected by human activities. The distribution of heavy metals in sediments is different from that in water, which should also be affected by the hydrological conditions of lakes.

Concentration Characteristics of Heavy Metals in Farmland-Sphagnum System and Ecological Risk Assessment

In order to study the current status of heavy metal pollution, the accumulation capacity of farmland Sphagnum for heavy metals and the source of heavy metal pollution in the soil near Gaozhai Reservoir in Maojian Tea Town, Duyun City, Guizhou Province were assessed. Sphagnum and topsoil near this area were selected as the research object to measure the content of heavy metals. Spatial analysis and multivariate statistical analysis methods were used to conduct pollution evaluation and source analysis of heavy metals. The results showed that the heavy metal content in topsoil and farmland Sphagnum were V>Zn>Cr>Pb>Cu>Ni>As>Cd>Hg and Zn>Cr>Ni>Cu>Pb>V>As>Cd>Hg, respectively. The dominant species of Sphagnum in the study area were Sphagnum palustre L. ssp. palustre and Sphagnum ovatum Hamp.C.Muell, both of which had a strong ability to accumulate soil Cd, Ni, Cu, and Zn; however, the S. ovatum enrichment capacity of soil heavy metals was generally higher than that of the latter. Both the single pollution index (Cf) and the geo-accumulation index (Igeo) indicated that the Cd and Hg content in soil were at the highest levels, and the average comprehensive pollution index RI was 87.75, which indicates a slight ecological risk. The sources of heavy metals in soil and Sphagnum included transportation, domestic sewage, agricultural activities, and natural soil-forming processes.

Pollution Characterization, Source Identification, and Health Risks of Atmospheric Particle-Bound Heavy Metals in PM2.5 in Zhengzhou City: Based on High-resolution Data

In order to study the pollution characteristics and sources of heavy metals in urban atmospheric PM2.5, 21 elements in atmospheric PM2.5 in Zhengzhou City were detected using an online metal analyzer during July and October 2017 and January and April 2018, and the changes in heavy metal concentrations were analyzed. Heavy metals were traced by enrichment factors, principal component analysis, and potential source function. The US EPA risk assessment model was used to assess their health risks. The results showed that:the concentrations of K, Zn, Mn, Pb, Cu, As, Cr, and Se increased with the increase in pollution level. The results of enrichment factors and principal component analysis showed that the main sources of heavy metals were crust, mixed combustion, industry, and motor vehicles. The characteristic radar charts showed that the pollution dominated by crustal sources mainly occurred in spring and winter, whereas the pollution dominated by mixed combustion sources mainly occurred in winter. Pb, As, and Ni were greatly affected by the transport of a fen nutrient-laden plain, Beijing-Tianjin-Hebei, and southern Henan, whereas Cd was greatly affected by the northwest region of the sampling site. As presented a significant carcinogenic risk in both adults and children, whereas Pb and Sb presented a significant non-carcinogenic risk in children.

Record of heavy metals in Huguangyan Maar Lake sediments: Response to anthropogenic atmospheric pollution in Southern China

The historical atmospheric heavy metal pollution of southern China over the past 200 years was explored by analyzing radiometric dating, heavy metals, and Pb isotopes from a sediment core in Huguangyan Maar Lake. Zn, Cd, Sb, Tl, and Pb in the lake are closely related to anthropogenic activities, while Cr and Ni are mainly derived from the weathering of basalt surrounding the lake. Atmospheric Zn, Cd, Sb, and Tl increased rapidly after 1980, consistent with the local industrial development. The increase of atmospheric Pb in southern China occurred earlier than in other regions of China, with the increase after 1850. War and the use of leaded gasoline were the main causes for the rapid increase in atmospheric Pb during 1910–1950. From 1950 to 2000, the input of Pb from anthropogenic activities decreased gradually due to the stable social environment. After 2000, atmospheric Pb continued to rise due to continued industrial development. The three-end-member model of Pb isotopes indicates that coal combustion is the main source of current atmospheric Pb. The proportion of Pb derived from vehicle exhaust emissions reached a peak in the 1960s, then gradually decreased and further reduced with the ban on leaded gasoline after 2000. These results are important in identifying the sources of atmospheric heavy metal pollution and in formulating pollution control strategies.

Heavy metal pollution and ecological risk assessment in the surface water from a marine protected area, Swatch of No Ground, north-western part of the Bay of Bengal

The primary intends of the study was to ascertain the degree of pollution, spatial distribution, and prime sources of heavy metals in a marine protected area, Swatch of No Ground, north-western part of the Bay of Bengal. Six heavy metals were considered, and their concentrations were found in the decreasing order of Fe > Pb > Cu > Zn > Ni > Cd. Several indices namely Heavy metal pollution index (HPI), Heavy metal evaluation index (HEI) and Nemerow pollution index (NPI), Potential ecological risk index (PER), Hazard quotient (HQ), and Hazard index (HI) were measured to portray the degree of pollution and risk assessment, respectively. HPI, HEI, and NPI suggested that the surface water of North-western Bay of Bengal is under moderate to high degree of pollution due to the higher concentration of Pb, Cu, and Cd. In addition, heavy metal pollution is moderate according to PER, and human health hazards are comparatively low according to HQ and HI. Principal component analysis, hierarchical cluster analysis, and correlation analysis result further reveal that anthropogenic activities are primly influencing the heavy metal accumulation in the study area. Moreover, all of the heavy metals had surpassed the background value of natural surface water in their concentrations. Three of the six heavy metals exceed the lowest biological chronic safety limit, except for Zn, Cd, and Ni recommended by the National Oceanographic and Atmospheric Administration. Hence, to conserve the balance of marine ecology, the local authorities must implement proper treatment of domestic and industrial waste management policies before causing excessive risk.

The Impact of Pb from Ammunition on the Vegetation of a Bird Shooting Range

Hunting with lead ammunition represents a source of heavy metal pollution to the environment that can be potentially high at the local scale. Intensive hunting of small game species can concentrate high levels of ammunition discharging in small areas. This type of hunting is a relevant economic resource for private landowners in some regions of Spain, and current legislation allows the use of lead ammunition in these scenarios. It becomes, therefore, highly relevant to study whether this activity may pose concerns to the conservation of the environment in the areas where it takes place. Using a red-legged partridge (Alectoris rufa) shooting range as a study area, we examined the effect of intensive hunting on this species on the vegetation present. We found significantly higher lead levels in the sprouts of plants of shooting areas related to control sites of the same property where partridge shooting does not occur. We found differences in the presence of lead between sprouts of different plant species. In addition, old sprouts of existing vegetation in shooting areas also showed higher lead levels than newly emerged sprouts of the same plants. These results demonstrate the impact of lead ammunition on vegetation in terms of persistence over time and differences between species. Further analyses using chemical and ecotoxicological data are necessary to evaluate the extent of environmental pollution risks. Our results provide new support in favor of the use of alternative ammunition, with particular emphasis on scenarios where hunting activity is intensive.

Spatial distribution of lead (Pb) in soil: a case study in a contaminated area of the Czech Republic

For decades, the Příbram district in the Czech Republic has been affected by industrial and mining activities, which are the main sources of heavy metal pollutants and negatively affect soil quality. A recent study examined visible–near-infrared (VNIR), shortwave-infrared (SWIR), and X-ray fluorescence (XRF) spectroscopy to model soil lead (Pb) content in a selected area located in Příbram. Following that study, and using the data, we examined the spatial distribution of Pb content in the soil, with a combination of traditional techniques (Moran’s I, hotspot analysis, and Kriging). One of the novel points of this work is the use of the Getis–Ord hotspot analysis before the execution of Kriging interpolation to better emphasize clustering patterns. The results indicated that Pb was a spatially dependent soil property and through extensive in-situ sampling, it was possible to generate an accurate interpolation model. The high-Pb hotspots coincided with topographic obstacles that were modeled using topographic profiles extracted from Google Earth, indicating that Pb content does not always exhibit a direct relationship with topographic height as a result of runoff, due to the contribution of topographic steps. This observation provides a new perspective on the relationship between Pb content and topographic patterns. Highlights Different spatial analyses were executed to examine the spatial distribution of Pb Extensive in-situ sampling provided an accurate Kriging interpolation model of Pb Pb hotspots with field soil data were mapped with a high degree of certainty The Pb hotspots coincided with topographic obstacles modeled using Google Earth

Effects of land use on the heavy metal pollution in mangrove sediments: Study on a whole island scale in Hainan, China

In recent decades, mangrove ecosystems at coastal zone are experiencing rapid land-use conversion, however effects of land use on the heavy metal pollution in mangrove sediments still are not clear. This study investigated the concentration and distribution of heavy metals (including chromium (Cr), zinc (Zn), lead (Pb), copper (Cu), arsenic (As) and cadmium (Cd)) in different mangrove sediments with different land-use patterns along seashore of the whole Hainan island (with the third largest mangrove area of China). The effects of land use on the accumulation of heavy metals in these mangrove sediments are also analyzed. The results showed contaminations of ∑6Metals in this study following the order of arable lands (ARAB) > aquaculture ponds (AQUA) > riverine area (RIVER) > ecological area (ECOL) > construction area (CONS). Accumulation degree of As and Cd were high in the AQUA, ARAB, and RIVER area. As metal hotspots, ARAB, RIVER and AQUA area showed the deteriorated sediment quality with high pollution load index (>1). Redundancy discriminate analysis revealed that mangrove, paddy lands and aquaculture ponds related activities correlated well with the metal pollution. The results clearly revealed that different land uses would not only change the accumulation capacity of mangrove soil for heavy metals, but also contribute different sources of heavy metal pollution. These findings do help to facilitate land-use planning and contribute to guide a better mangrove wetland management at coastal zone.

Source analysis and source-oriented risk assessment of heavy metal pollution in agricultural soils of different cultivated land qualities

Heavy metal pollution in soil has received much attention in recent decades. Many studies have analyzed the contamination status, spatial distribution, and pollution sources of heavy metals. Little information is available on the interaction between cultivated land quality and soil heavy metal pollution. Combining soil quality information and intensive heavy metal sampling surveys, this study analyzed heavy metal contamination and the ecological and health risks of various soils with different quality levels. Additionally, through the PMF model and risk assessment techniques, the ecological and health risks of specific pollution sources and their interaction with soil quality were investigated. The results showed that the mean content of the studied elements followed the increasing order of Hg (0.12 mg/kg) < Cd (0.19 mg/kg) < As (6.98 mg/kg) < Pb (25.57 mg/kg) < Cr (72.02 mg/kg). In addition, with increasing soil quality, the concentrations of Pb, Cr and Hg as well as the overall ecological risk increased significantly. Regarding health risks, heavy metal pollution posed a higher risk to children than adults, and ingestion was the main exposure pathway. The total hazard index and carcinogenic risk also increased with increasing soil quality. The PMF analysis showed that Pb and Cr mainly came from industrial activities, As could be attributed to natural sources, Cd was mainly derived from agricultural activities, and Hg pollution was determined by coal combustion. Considering the risks of specific pollution sources, agricultural activities and coal combustion were the major reasons for high ecological risks, whereas industrial activities and coal combustion posed significantly higher risks in suburban high-quality soil. Industrial activities mainly determined the health risk, which contributed more than 50% to the total risk. There was an upward health risk trend with increasing soil quality. Industrial activities in high-quality suburban soil posed the highest health risk to both adults and children. Reasonable and effective policies should be formulated to control industrial pollution and improve the ecological environment in this area.

Pollution and Potential Ecological Risk Assessment of Heavy Metals in Surface Sediments of Tangxun Lake

In order to understand the pollution characteristics, spatial distribution, potential sources, and ecological risk of heavy metals in the sediments of Tangxun Lake, the contents of heavy metals (As, Hg, Cd, Cr, Cu, Pb, Zn, and Ni) in the surface sediments of Tangxun Lake were analyzed, and the pollution status and potential ecological risk degree of heavy metals in the sediments were evaluated using the geo-accumulation index and potential ecological risk index. The potential sources of heavy metal pollutants were analyzed by correlation and principal component analysis. The results showed that except for Cr, the contents of other heavy metals were higher than their background values. The contents of Hg, Cd, Zn, and Cu were higher in the southwest and northeast corners of the lake, which may come from the combined pollution of sewage discharge, fisheries, and surrounding industrial and agricultural activities. The geo-accumulation index and potential ecological risk showed that Hg and Cd were in moderate pollution; Cu, Pb, and Zn were in non-light pollution; and As, Cr, and Ni were in non-pollution. Except for Hg and Cd, there were serious and serious potential ecological risks, and the other elements were at a low risk level. The heavy metals in the surface sediments of Tangxun Lake showed a high ecological risk level.

Overview of heavy metal pollution and health risk assessment of urban soils in Yangtze River Economic Belt, China.

Using national multi-purposeregional geochemical survey (NMPRGS) data, this overview systematically summarizes the pollution levels and health risks posed by 8 heavy metals (As, Cd, Pb, Zn, Hg, Cu, Cr and Ni) in urban soils of 86 cities above the prefecture level in Yangtze River Economic Belt (YREB). Meanwhile, the spatial distribution and main sources of heavy metal pollutants in urban soils of key cities are described in detail. On a regional scale, Hg and Cd contamination in urban soils of YREB is most prominent, and As, Cu, Pb and Zn contamination exists in several cities, while Cr and Ni contamination is almost not shown. The type of industrialization and the history of urbanization affect the soil heavy metal pollution in majority cities, and the influence of geological background on the content of heavy metals in urban soils cannot be ignored. Specifically, the urban pollution of Cd, As, Pb and Zn is mainly concentrated in Hunan and Hubei Provinces, which are highly developed in mining industry, especially in Zhuzhou, Chenzhou, Huangshi and Xiangtan cities, while the major soil Hg pollution occurs in Zhejiang and Jiangsu Provinces with rapid economic development, where Shaoxing, Ningbo, Suzhou and Wuxi are the key polluted cities. Heavy metals in the urban soils investigated generally posed low non-carcinogenic and carcinogenic risks to the adults. However, the non-carcinogenic risk to minors in some cities (e.g., Chenzhou and Huangshi) should be given cautious attention.

Heavy metal toxicity, ecological risk assessment, and pollution sources in a hydropower reservoir.

Heavy metal (HM) toxicity, ecological risk, and pollution sources were analyzed using the pollution indexing and statistical methods in the Three Gorges Reservoir (TGR). The average concentration of HM increased in the order of Cr < Ni < As < Cd < Cu < Mn < Pb < Zn < Al < Fe during the recharge period and Cd < Cr < Ni < As < Cu < Pb < Mn < Zn < Al < Fe during the discharge period. Significant spatial variations of Pb, Zn, Cd, As, Mn, Ni, Cr, and Cu were observed at the upstream and downstream sampling sites. Pb sharply increased during the recharge period, ranges (6.93-148.62μg/L) and exceeded WHO and USPEA standards limit. HPI, HEI, Cd, WPI indicated low pollution and moderate pollution with the strong influence of Pb and Cd in the discharge and recharging period, respectively. HTML values are below the permissible toxicity load except for Pb. The Pb toxicity removal percentage is 56.47%, suggesting that the lead's toxicity level is high in TGR and requires the removal process. Ecological risk index values indicated that pollution is low in TGR. The potential ecological risk indexes (RI) of 9.07 and 31.60 were obtained for the discharge and recharge period, respectively, indicating low potential ecological risk from heavy metals in TGR. However, RI values revealed that (Pb, Cd, As Cr Ni, Cu Zn, and Mn) were the most ecological risk HMs in TGR. A significant ecological risk of Pb and Cd distribution was observed across the TGR. Multivariate statistical results found that Pb, Cd, Zn, Mn, Ni, As, Cr, Cu mainly originate from industrial wastewater, mining, metals processing, and agricultural runoff. Fe and Al were mainly from bedrock weathering. Pb, Cd, Zn HMs are a threat to the reservoir ecosystem. This study delivered a current status of HM pollution, toxicity, ecological risk, and pollution sources, indicating a vital insight into HM pollution and water security management inthe Three Gorges Reservoir.

Assessment of the Transfer of Trace Metals to Spontaneous Plants on Abandoned Pyrrhotite Mine: Potential Application for Phytostabilization of Phosphate Wastes.

The abandoned Kettara pyrrhotite mine (Marrakech region, Morocco) is a real source of acid mine drainage (AMD) and heavy metal pollution from previous mining operations—which has spread, particularly because of wind erosion. A store-and-release cover system made of phosphate wastes was built on the site for preventing AMD. To ensure the integrity of this cover and its durability, it is desirable to revegetate it (phytostabilization) with plants adapted to the edaphoclimatic conditions of the region. In this paper, a study was carried out on the spontaneous vegetation around the phosphate cover in order to consider the selection of plants to promote the stabilization of the Kettara mine tailings pond. Nine species of native plants with their rhizospheric soils growing in agricultural soils and tailings from the Kettara mine were collected, and metals (As, Cd, Co, Cu, Pb, Zn, Ni, Cr) were analyzed. The soil analysis showed that the tailings contained high concentrations of Cu (177.64 mg/kg) and Pb (116.80 mg/kg) and that the agricultural soil contained high concentrations of As (25.07 mg/kg) and Cu (251.96 mg/kg) exceeding the toxicity level (Cu > 100 mg/kg, Pb > 100 mg/kg, As > 20 mg/kg). The plant analysis showed low trace metal accumulation in Scolymus hispanicus, Festuca ovina, Cleome brachycarpa, Carlina involucrata and Peganum harmala. These species had a bioconcentration factor (BCF) greater than 1 and a translocation factor (TF) less than 1, demonstrating a high tolerance to trace metals. Therefore, they are good candidates for use in the phytoremediation of the Kettara mine tailings. These species could also potentially be used for the phytostabilization of the phosphate waste cover of the Kettara mine, thus completing the rehabilitation process of this area.

Spatial Distribution and Source Analysis of Soil Heavy Metals in a Small Watershed in the Mountainous Area of Southern Ningxia Based on PMF Model

In order to ascertain the distribution characteristics of soil heavy metal pollution and main pollution sources in a small watershed in the southern mountainous area of Ningxia and to ensure the quality of the soil environment, the contents of heavy metals Pb, Ni, Zn, Mn, Cu, Cr, and Cd in 260 surface soil samples (0-20 cm) were collected and determined. Based on the soil background value in Ningxia, the soil heavy metal pollution status and potential ecological risk were evaluated through the single factor index, Nemera composite index, and potential ecological risk index, and the method of combining positive definite matrix factor analysis (PMF) and Kriging interpolation was used to analyze the soil heavy metal spatial distribution and source. The results showed that the average contents of ω(Pb), ω(Ni), ω(Zn), ω(Mn), ω(Cu), ω(Cr), and ω(Cd) were 31.42, 36.22, 62.89, 546.18, 22.26, 61.90, and 0.18 mg·kg-1, respectively. Except for Ni, the other elements were higher than the background value of Ningxia but lower than the background value of agricultural soil pollution risk selection criteria and green food environmental quality standards. The Nemera composite index showed that the proportions of mild, moderate, and severe heavy metal pollution were 71.92%, 19.23%, and 1.54%, respectively. The potential ecological risks were mainly minor risks, accounting for 98.85%. In addition, there were a very small number of samples with medium potential ecological risk levels, accounting for 1.15% of the total number of samples. Source analysis showed that the main sources of soil heavy metals in the small watershed in the mountainous area of southern Ningxia were mixed sources of fertilization and industrial emissions (12.6%), agricultural activity sources (23.5%), natural parent material sources (27.6%), mixed sources of pesticide use and mining development emissions (17.7%), and atmospheric deposition sources (18.6%).

Effect of urbanization on heavy metal contamination: a study on major townships of Kannur District in Kerala, India

BackgroundIn the last few decades, the air, water, and soil are contaminated due to different anthropogenic activities and severely affect the environmental quality. Pollution is the harmful effect and creates undesirable changes in the land use and land cover pattern. The growth of urbanization leads to the degradation of the ecosystem and ultimately affects the living and non-living organisms. In view of these, the present investigation is carried out to assess the heavy metal pollution in major towns due to the impact of urbanization in Kannur district and desirable conclusions were drawn.ResultsThe results shows that higher level of heavy metal pollution is observed in major towns of Kannur district.ConclusionThe heavy metal contamination in the major towns of Kannur district is mainly due the anthropogenic activities. The discharge of domestic effluents and industrial waste is the major source of heavy metal pollution. In-depth studies and proper waste management plans are needed to decrease the level of heavy metal contamination prevailing in the study area.

The potential ecological risks and bioavailability of heavy metals in the sediments of Lake Baiyangdian

沉积物是湖泊水体重金属的主要汇集场所，也是湖泊重金属污染研究及整治的重点.本文分析了白洋淀多个淀区沉积物中16种重金属含量水平及垂向分布特征，解析了其中典型有害重金属潜在生态风险，并基于酸可挥发性硫（AVS）及同步可提取金属（SEM）、间隙水溶解态金属、可转化态金属形态分级等研究，对重金属生物可利用性进行了分析.结果表明：沉积物重金属含量均值高低依次为Fe （29630.50 mg/kg）>Ti （3213.07 mg/kg）>Mn （539.44 mg/kg）>Zn （104.01 mg/kg）>V （76.63 mg/kg）>Cr （52.60 mg/kg）>Cu （43.49 mg/kg）>Ni （35.83 mg/kg）>Pb （26.75 mg/kg）>Co （10.32 mg/kg）>As （8.96 mg/kg）>Mo （2.06 mg/kg）>Sb （1.57 mg/kg）>Tl （0.43 mg/kg）>Cd （0.31 mg/kg）>Hg （0.16 mg/kg）；其中，10种重金属在各淀区沉积物中呈现出自北往南逐渐降低的趋势，各金属在不同淀区分布差异性主要由污染输入所致.除北部烧车淀区域外，其余区域重金属潜在生态风险总体处于较低水平.重金属污染主要来源于该区域周边河道，但近10年来污染输入及在沉积物中的富集总体趋于稳定并呈逐渐降低的趋势.入淀污染不仅增加了该区域沉积物中重金属总量，也使得其中可转化态重金属比例较高，大多在30%~90%之间，提升了重金属生物可利用潜力.水生植物等内生性有机质的大量富集导致沉积物还原性较强，AVS含量较高，沉积物中AVS和ΣSEM均值分别为（10.59±6.37）和（2.23±1.53）μmol/g （dw）.Cd、Cu、Ni、Pb、Zn等金属由于高含量还原态硫的固定而生物可利用性较低.然而，As和Hg在这样的高有机质和强还原环境下更容易溶解和释放，是潜在生物可利用性相对较高的金属，在间隙水中的浓度分别达到（17.07±0.23）和（2.39±0.94）μg/L，未来研究及整治中应给予更多关注.;Being the primary sink for heavy metals in lakes, the sediment is the hotspot for the research and remediation of heavy metals in lakes. In the current study, the horizontal and vertical distributions of 16 kinds of heavy metals in the sediment of multiple areas in Lake Baiyangdian were analyzed and based on the concentrations of several typical harmful heavy metals in the sediment, the potential ecological risk was assessed. The bioavailability of heavy metals was further analyzed according to the acid volatile sulfide (AVS), simultaneously extracted metals (SEM), dissolved metals in the pore water, and fractionation of mobile metals. The results showed that the concentrations of heavy metals in the sediment followed the descending order of:Fe (29630.50 mg/kg)>Ti (3213.07 mg/kg)>Mn (539.44 mg/kg)>Zn (104.01 mg/kg)>V (76.63 mg/kg)>Cr (52.60 mg/kg)>Cu (43.49 mg/kg)>Ni (35.83 mg/kg)>Pb (26.75 mg/kg)>Co (10.32 mg/kg)>As (8.96 mg/kg)>Mo (2.06 mg/kg)>Sb (1.57 mg/kg) >Tl (0.43 mg/kg)>Cd (0.31 mg/kg)>Hg (0.16 mg/kg). Among all the heavy metals studied, 10 kinds of the metals in the sediment of the studied areas showed a gradually decreasing trend from north to south of the lake. The variations in the horizontal distribution of metals between different areas were most likely caused by the external pollution input from the north part of the lake. The potential ecological risks of heavy metals in most parts of the lake were generally at low levels except for the Shaochedian area in the north. The inflowing rivers around this area were the main sources of heavy metal pollution. While the pollution input and the accumulation of heavy metals in the sediment have generally stabilized and gradually decreased during the past 10 years, the pollution input not only increased the total amount of heavy metals in the sediment of this area but also led to the high proportion of mobile heavy metals (mostly between 30% and 90%), which increased the bioavailable potential of metals. The massive enrichment of endogenous organic matter from the wither of aquatic plants led to the strong reductive status of the sediment, which thereby resulted in high concentrations of AVS. The average concentrations of AVS and ΣSEM in the sediment of the whole lake were (10.59±6.37) μmol/g(dw) and (2.23±1.53) μmol/g(dw), respectively. Due to the immobilization with a high concentration of sulfides, the bioavailability of Cd, Cu, Ni, Pb, and Zn were generally low. However, As and Hg are much easier to dissolve and release from the sediment under such high organic matter content and strong reducing environment. These two metals had relatively high potential bioavailability with the concentration in the pore water reaching (17.07±0.23)μg/L and (2.39±0.94)μg/L, respectively, which should be given more attention during future research and remediation works.

Effects of lead contaminants on engineering properties of Iranian marl soil from the microstructural perspective

Most of the industries in the south of Iran and north of the Persian Gulf are built on marl bedrocks and these industries are major sources of heavy metal pollutants. Therefore, the engineering properties of marl soils contaminated with heavy metals (particularly lead ions) are worthy of thorough investigation. This was accomplished by artificial contamination of marl soil with varying lead concentrations and measurment of some geotechnical (granularity, Atterberg limits, compressive strength, and permeability) and geo-environmental (CEC, pH, and contaminant retention) characteristics. In addition, with the aid of X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images the changes in mineralogy and microstructural behavior of lead-contaminated soil were investigated. According to the findings of the present study, marl soil can hold about 200 cmol/kg-soil of lead concentration. As seen by SEM images, the lead precipitation changed the soil's geotechnical properties by altering the structure and texture of soil (notably flocculation). At 100 cmol/kg-soil lead concentration, the compressive strength was reduced by about 85%, while the hydraulic conductivity increased up to 170 times. Adding lead to the marl soil decreased the intensity of X-ray diffraction peaks for the main clay minerals and created new peaks associated with precipitated cerussite, shannonite, and leadhillite.