Sources Of Heavy Metal Pollution Research Articles

Essential and Heavy Metals Content in Wild and Cultivated Mentha Species from Bosnia and Herzegovina

Both essential and heavy metals play important roles in human health and diseases. The aim of the present study was to determinate concentrations of essential and heavy metals, such as Na, K, Ca, Mg, Cu, Cr, Mn, Ni, Fe, Pb, Zn, and Cd, in the leaves of Mentha longifolia L. and Mentha × piperita L. The plant material samples were collected from six different locations in Bosnia and Herzegovina (B&H), at selected distances from heavy metal pollution sources. Wet digestion was applied for the dissolution of samples and essential and heavy metals concentrations were analysed by flame atomic absorption spectrometry and (FAAS). Results of the analysis (expressed as mg g–1) were obtained as follows: Na 2.08–4.12; K 14.85–22.54; Ca 9.06–15.53; Mg 1.93–3.12; Cu 0.01–0.05; Cr 0.70–0.90; Mn 0.02–0.09; Ni 1.10–7.00; Fe 0.06–1.11; Pb 0.10–0.90; Zn 0.01–0.04. The cadmium concentration in all samples was below the detection limit by FAAS. Strong correlation between Ni and Pb, as well as Ni and Fe, confirmed mostly environmental and processing influence/impact. In conclusion, Mentha longifolia L. and Mentha × piperita L. can be used in daily consumption considering the high content of essential metals Fe, Cu, Mg, and Zn, and their beneficial effects on normal body function. In addition, there is no risk of heavy metals to human health after consuming these samples due to lower concentrations.

A Study on Heavy Metals in the Surface Soil of the Region around the Qinghai Lake in Tibet Plateau: Pollution Risk Evaluation and Pollution Source Analysis

In order to reveal the pollution characteristics and sources of heavy metals in surface soil of the region around the Qinghai Lake in Tibet Plateau, improve the prevention awareness and measures of local residents and urge the local government to implement necessary prevention and control measures, nine heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) in the surface soil samples of the region around the Qinghai Lake have been collected and analyzed. The methods such as statistic method, geo-accumulation index method, Nemerow index method, potential ecological risk index method, human health risk evaluation method and positive matrix factor analysis model (PMF) have been used to evaluate pollution characteristics and potential risks and analyze the sources of heavy metals. The results are shown below. First, the average contents of heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) in soil are 11.73 ± 3.78, 0.62 ± 1.40, 12.38 ± 3.68, 41.35 ± 13.01, 19.33 ± 8.92, 546.96 ± 159.28, 21.18 ± 7.04, 21.86 ± 6.61 and 63.51 ± 19.71 mg·kg−1, respectively. Compared with the background values of the soil environment in Qinghai Province, it can be seen that there is an accumulation of these heavy metals to varying degrees, which is the most serious in Cd, Co and Pb. Second, the analysis of the geo-accumulation index and Nemerow index indicates that the heavy metals in the surface soil of the region around the Qinghai Lake have reached the level of heavy pollution, mainly polluted by Cd, and the accumulation of heavy metal pollution in the north, south, southwest and southeast of the study area is more serious. Third, the results of potential ecological risk evaluation show that the study area as a whole is classified as an area with high ecological risk, and Cd contributes the most to the overall risk. In fact, the heavy metals in the soil of the study area produce no noncarcinogenic and carcinogenic health risks to human health, and children and adults may be exposed to these risks by the mouth. Finally, the PMF results reveal that the sources of heavy metals in the study area include the sources of agricultural production, the nature, coal burning and transportation, with a contribution rate of 43.10%, 25.34%, 19.67% and 11.89%, respectively.

Heavy metal pollution and mobility of sediment in Tajum River caused by artisanal gold mining in Banyumas, Central Java, Indonesia.

The heavy metals Cu, Pb, Zn, and Cd in the stream sediment of the Tajum River were studied based on 12 sediment samples obtained from upstream to downstream. The artisanal mining activities in the study area generated mining processing waste (tailing) and are the primary source of heavy metal pollution. The samples were analyzed for metal concentration as well as metal mobility based on sequential extraction analysis. Heavy metal analysis for the concentration of the metals showed that the value of Cu, Pb, Zn, and Cd in sediment samples transcends the mean crust. The change of the heavy metal concentrations in stream sediment between the upstream and downstream areas showed that higher levels were located near mining activities in upstream and that these decreased with distance to downstream. The result of the sequential extraction study revealed that Cu and Pb were more found in the exchangeable and carbonate fraction of about 26% and 24%. Meanwhile, Zn and Cd were present in the Fe-Mn oxide, an organic and residual fraction of about 90% and 85%, respectively. The mobility factor assessment revealed that the heavy metals investigated had an average mobility factor of 25.89%, 23.9%, 14.4 %, and 9.24% for Cu, Pb, Zn, and Cd, respectively. Overall, Zn and Cd in sediment in the study area were less mobile compared with Cu and Pb.

Pollution and Ecological Risk Evaluation of Heavy Metals in the Soil and Sediment around the HTM Tailings Pond, Northeastern China.

Tailings ponds are a main heavy metal pollution source in mining areas. In this study, the geo-accumulation index () and the potential ecological risk index (RI) are used to evaluate the environmental impact of Hongtou Mountain (HTM) tailings pond on the surrounding area. Farmland soil, surface water, and sediment samples in the Hun River around the HTM tailings pond were collected. Heavy metal contents in the samples were analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Results show that Cu, Zn, and Cd content in the farmland soil and sediment around the lower reaches of the Hun River (HTM tailings pond section) are obviously higher than the upper reaches. The values show that the farmland soil near the outlet of the tailings pond is the most polluted area. Cu was classified as moderate–strongly pollution, Zn was moderately pollution, and Cd was strongly pollution. Cd is the major pollutant in farmland soil, the monomial ecological risk () for Cd is a very high potential ecological risk. The potential ecological risk of sediment in the dry season is more serious than in the raining season. In the dry season, the index shows strong pollution for Cu and Cd at the confluence of the Hun River and the tributary from the HTM tailings pond, and a moderate–strongly pollution for Zn. Whereas, the index shows that the monomial ecological risk for Zn at H3 is low, and Cu is moderate. The potential ecological risk at H3 is high, and Cd is the main source of the ecological risk around the HTM tailings pond.

Heavy Metals Assessment in the Medjerda River Basin (Northeastern Algeria): A Preliminary Water Analysis and Toad Skin Biopsy

Our study attempted to monitor the quality of water in Medjarda basin (Northeastern Algeria) and to provide baseline information of heavy metals in the water as well as in a potential amphibian biosentinel, the spiny toad, Bufo spinosus. We measured pH, temperature, dissolved oxygen and biological oxygen demand of water and levels of heavy metals in toad skin using an atomic absorption flame spectrophotometer. Lead (Pb) concentration in water and in toad skin at all sites exceeded respectively 60 and 96 times the standard reference values. The heavy metal concentrations, in descending order, in water and in male toad skin were as follows: Pb > Fe > Cu > Zn and Fe > Pb > Zn > Cu respectively. This study highlights the ecological status of the surrounding areas upstream of the Medjarda basin as being a point source of heavy metal pollution. It is further stated that a non-invasive skin removal is an ethically sound technique to evaluate heavy metal accumulation in aquatic animals like toad, without euthanizing the specimens and making any loss to biodiversity of the species.

Source apportionment of cadmium pollution in agricultural soil based on cadmium isotope ratio analysis

Anthropogenic activities, especially industrial production and agricultural practices have led to Cd accumulation in the agricultural soil locating near to the industrial areas of China threatening soil environmental quality and food security. In this study, the sources of Cd pollution were accurately analyzed, which may lead to efficiently control the Cd content in the soil. The samples of agricultural topsoil, four possible pollution sources such as smelter dust, automobile exhaust, cement factory dust and agricultural fertilizer were collected, and the Cd concentrations and Cd isotope ratios were analyzed using the instrument of Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Multi-collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS). The results indicated that the Cd concentration of agricultural topsoil (11.72 ± 0.30 mg kg−1) was much higher than the recommended value (0.6 mg kg−1). The highest δ114/110CdNIST3108 value (−0.15 ± 0.14‰) was observed for smelter dust and the lowest δ114/110CdNIST3108 value (−0.64‰) was found in cement factory dust. Similarly, the highest Cd concentration was found in smelter dust and it was clearly distinguishable from the other samples based on δ114/110CdNIST108 values. Cd isotope analysis suggested that smelter along with agricultural fertilizer were the major sources of Cd accumulation in agricultural topsoil. In addition, based on the IsoSource software, the relative Cd contribution rates due to automobile exhaust, cement factory, agricultural fertilizer, and smelter dust were 14%, 7%, 20%, and 59%, respectively, demonstrating that smelter dust is the main pollution source of Cd in the study area. Cd isotope analysis is a promising tool to accurately identify the heavy metal pollution sources.

Spatial distribution, source identification, and risk assessment of heavy metals in the soils from a mining region: a case study of Bayan Obo in northwestern China

Bayan Obo deposit is the largest light rare earth ore deposit in the world, which releases a lot of heavy metals to the surrounding environment during the long-term mining process. To make efficient protection plan, it is necessary to investigate the concentration, spatial distribution, contamination sources, and environmental-health risks of heavy metals surrounding the Bayan Obo deposit. A total of 46 soil samples were collected from mining areas. Mn, Cu, Zn, Pb, Cd, As, Hg and Cr concentrations in each soil sample were determined. The spatial distribution characteristics of heavy metals in soils were studied by using ArcGIS spatial interpolation analysis. Multivariate statistical analyses were applied to identify the pollution sources of heavy metals. The environmental-health risks of heavy metals were evaluated by calculating geo-accumulation index (I geo), potential ecological risk index (RI), risk assessment code (RAC), modified risk assessment code (mRAC), potential non-carcinogenic risk (HI) and carcinogenic risks (CR). The results showed that the average values of other heavy metals except Cr and As were considerably higher than the background values of Inner Mongolia and control area, which indicated the accumulation of these metals in this area, especially Cd. Cu, Zn, Mn, Cd and Pb showed similar spatial distributions, exhibiting a high level near the metal ore. Hg was mainly distributed in areas with intense industrial activities. Four origins were identified by multivariate analysis: industrial activities and fuel combustion for Hg, mining activities for Cu, traffic source for Mn and Pb, the combination of mining and traffic activities for Cd and Zn, and Cr and As was mainly controlled by natural sources. The results of the environment risk assessment showed Bayan Obo mining region was a region seriously polluted by high amount of heavy metals and low bioavailability. There is no potential carcinogenic and non-carcinogenic risk. The research results provide a scientific basis and technical support for monitoring and early warning of soil pollution in mining areas.

Heavy metal contamination and ecological risk in sediment from typical suburban rivers

AbstractThe environmental pollution and ecological risk of riverine systems are of growing concern in China and worldwide. Previous studies have mainly focused on urban and rural rivers. However, suburban rivers differ from urban and rural rivers as they are subject to complex pollution sources, random discharge of domestic garbage, improper handling of agricultural means of production and imperfect municipal engineering facilities; thus, identifying the complex pollution sources and ecological risk in suburban rivers might help improve environmental quality and inform management decisions. The occurrence and spatial distribution of six heavy metals were investigated and analysed. The average concentrations of target heavy metals in surface sediments were in the order of Zn (1,198.7) > Cr (84.6) > Pb (40.0) > Cu (25.6) > Ni (11.8) > Cd (0.5) (mg/kg, dry weight). The concentrations of all heavy metals in the study area except Ni and Pb were significantly higher (p < .05) than the environmental background values. The pollution load index (PLI) indicated that the sediments were “moderately polluted”, which was mainly caused by Zn and Cd. The potential ecological risk index (RI) showed that there was a “high” ecological risk of heavy metals in sediments, of which Cd accounted for 83% of the RI. A principal component analysis coupled with Pearson's correlations indicated that Pb and Zn were mainly associated with domestic, traffic and agricultural sources; Cr, Cu and Ni were mainly derived from traffic and natural sources, and Cd was likely from coal combustion and agricultural sources. The results from this study will provide the scientific knowledge needed to control and manage the emissions or discharge from multiple heavy metal pollution sources and identify their potential ecological risk in the sediment of suburban rivers.

Unsupervised Monitoring Vegetation after the Closure of an Ore Processing Site with Multi-Temporal Optical Remote Sensing.

Ore processing is a source of soil heavy metal pollution. Vegetation traits (structural characteristics such as spatial cover and repartition; biochemical parameters—pigment and water contents, growth rate, phenological cycle…) and plant species identity are indirect and powerful indicators of residual contamination detection in soil. Multi-temporal multispectral satellite imagery, such as the Sentinel-2 time series, is an operational environment monitoring system widely used to access vegetation traits and ensure vegetation surveillance across large areas. For this purpose, methodology based on a multi-temporal fusion method at the feature level is applied to vegetation monitoring for several years from the closure and revegetation of an ore processing site. Features are defined by 26 spectral indices from the literature and seasonal and annual change detection maps are inferred. Three indices—CIred-edge (CIREDEDGE), IRECI (Inverted Red-Edge Chlorophyll Index) and PSRI (Plant Senescence Reflectance Index)—are particularly suitable for detecting changes spatially and temporally across the study area. The analysis is conducted separately for phyto-stabilized vegetation zones and natural vegetation zones. Global and specific changes are emphasized and explained by information provided by the site operator or meteorological conditions.

Heavy metal contamination assessment and source apportionment analysis using multivariate methods in surface sediments of mining-impacted rivers in Benguet

ABSTRACT This study provides a comprehensive assessment of Hg, As and Pb contamination in surface sediments of two rivers in Benguet, Philippines where mining is a primary industry and a potential source of heavy metals pollution in the rivers. Concentrations of Hg, As and Pb in river sediment samples were measured and assessed using single-element and multi-element indicators. Two points in each river were identified as highly contaminated while the other sites have low to moderate contamination and ecological risk. Multivariate analyses revealed the affinity of Hg and As to fine particles and the co-existential nature of Hg and As in the rivers, which suggests common anthropogenic source.

Contamination assessment and source apportionment of heavy metals in agricultural soil through the synthesis of PMF and GeogDetector models

Heavy metal pollution in soils has attracted great attention worldwide in recent decades. Selecting Hangzhou as a case study location, this research proposed the synthesis application of positive matrix factorization (PMF) and GeogDetector models for quantitative analysis of pollution sources, which is the basis for subsequent soil pollution prevention and remediation. In total, 2150 surface soil samples were collected across the study area. Although the mean concentrations of As, Cd, Cr, Hg, and Pb in the soils were lower than the National Environmental Quality Standards for Soils in China, the mean contents of As and Cd were higher than their corresponding local background values by approximately 1.31 and 1.59 times, respectively, indicating that heavy metals have been enriched in topsoil. Agricultural activities, industrial activities, and soil parent materials were the main sources of heavy metal pollution in the soils, accounting for 63.4%, 19.8%, and 16.8% of the total heavy metal accumulation, respectively. Cr was derived mainly from soil parent materials (80.72%). Cd was closely associated with agricultural activities (73.68%), such as sewage irrigation and application of fertilizer. Mercury was mainly attributed to industrial activities (92.38%), such as coal mining and smelting. As was related to agricultural (57.83%) and natural (35.56%) sources, and Pb was associated with industrial (42.42%) and natural (41.83%) sources. The new synthesis models are useful for estimating the source apportionment of heavy metals in soils.

Quantitative source identification and apportionment of heavy metals under two different land use types: comparison of two receptor models APCS-MLR and PMF.

At present, many researchers are increasingly aware of the importance of using models to identify heavy metal (HM) pollution sources. However, on the performance and application of different source identification models to HMs under different land use types had been studied little. In this study, comparison of absolute principal component scores-multiple linear regression (APCS-MLR) and positive matrix factorization (PMF) models and their application characteristics in identifying pollution sources were carried out by using 11 HMs in Zhongwei City farmland and Shizuishan industrial park, Ningxia. The results indicated that HM pollution in farmland mainly came from pesticides, fertilizers, and deposition of the Yellow River, while the pollution in industrial park mainly originated from atmospheric deposition and various industrial productions. The APCS-MLR model had the problem of less identification sources and the difficulty to explain the complex pollution, while the PMF model not only identified more pollution sources, but also distinguished heavy metal-related sources for two different land use types and different industrial production conditions. It is of great significance the formulation of agricultural-related pesticides' and chemical fertilizers' rational use and various industrial production-related raw materials put in and emission control strategies.

Characteristics and sources of heavy metal pollution in desert steppe soil related to transportation and industrial activities.

A study area was selected from the industrial region of Gaoshawo Town, Yanchi County, Ningxia, to explore the level of heavy metal pollution in desert grasslands due to industrial activities. A total of 82 surface soils were collected, and the concentration of heavy metals, namely, Cu, Cd, Cr, Pb, Zn, Mn, and Co, was determined by ICP-AES (atomic emission spectrometer) (HK-8100); the average values were 21.64 ± 3.26, 0.18 ± 0.02, 44.99 ± 21.23, 87.18 ± 25.84, 86.63 ± 24.98, 570.49 ± 171.57, and 17.96 ± 9.96mgkg-1. The single-factor, Nemerow pollution, and potential ecological risk index methods were used to evaluate the status of soil heavy metal pollution and the contribution from the major sources identified by the receptor model. The results showed that 9.09% of the samples were slightly polluted, 32.47% of the samples were moderately polluted, and 58.41% of the samples were heavily polluted. The comprehensive potential ecological risk index indicated that 90.79% of the samples had moderate ecological risk. It was verified from the models and spatial distribution maps that Cr, Co, Zn, and Mn are mainly contributed by the industrial sources that account for 55.04%, 92.13%, 50.05%, and 48.77% of these heavy metals, respectively. The heavily contaminated areas are distributed around the industrial park. A total of 70.63% and 77.83% of Cu and Pb are contributed by transportation sources, respectively, with the concentrations decreasing from southwest to northeast. The contribution from agricultural activities to Cd is 77.02%, with concentrations largely distributed in the north of the highway. This study showed that the existence of the Gaoshawo Industrial Zone and the corresponding industrial and transportation activities have a significant impact on the grassland soil environment.

Characteristics and health risk assessments of heavy metals in PM2.5 in Taiyuan and Yuci college town, China

To clarify the pollution sources of heavy metals in PM2.5 and the health risks posed by them in heating and non-heating seasons, 42 samples were collected in 2017 and 2018 in Taiyuan and Yuci college town, China. Elemental analysis of the PM2.5 samples through acid-dissolved plasma mass spectrometry was performed to determine the concentrations of 10 elements (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn). We determined the types of pollution sources by enrichment factor (EF) and principal component analysis (PCA). We performed a health risk assessment based on the US Environmental Protection Agency (EPA) guidelines and the database of the International Agency for Research on Cancer (IARC) to assess both carcinogenic and non-carcinogenic risks of the heavy metals to adults and children. The results indicate that the EF values of all 10 elements were greater than 1, suggesting anthropogenic sources in both heating and non-heating seasons. PCA revealed that the three main components were soot dust, metal smelting emission, and industrial dust. Regarding the health risks caused by the heavy metals, children were more susceptible to non-carcinogenic risks than adults, and people faced higher non-carcinogenic risks during the heating season. For carcinogenic risk, Cr has the highest risk coefficient (1.68 × 10−4), higher than the US EPA’s threshold (1.00 × 10−6). People were exposed to carcinogenic risk. The study explored specific pollution sources and explained their effect on health to assist with the development of prevention and control measures.

Acute toxicity of heavy metal, nickel and chromium on fresh water edible fishes

Industrial effluent are the major sources of heavy metal pollution and it is released into fresh waterbodies. Catla catla and Clarias batrachus were exposed to Nickel and Chromium for 24, 48, 72 and 96 hrs. The median lethal concentration (LC50) of nickel to Catla catla and Clarias batrachus for 96 h of exposure were 5.77 mg/l and 7.595mg/l, respectively. The median lethal concentration (LC50) of chromium to Catla catla and Clarias batrachus for 96 h of exposure were 16.468 mg/l and 34.476 mg/l, respectively. The result also revealed that mortality rate depends upon concentrations of heavy metals and duration of exposure. The acute toxicity levels were derived from LC50 concentrations of the heavy metals. Both the heavy metals produced lethality at smaller doses. Physiological responses like rapid opercular movement and frequent gulping of air was observed during the initial stages of exposure after which it became occasional. All these observations can be considered to monitor the quality of aquatic eco system and severity of pollution.

Evaluating heavy metal contamination of riverine sediment cores in different land-use areas

Anthropogenic activities are regarded as the main sources of heavy metal pollution, yet few studies have investigated the effects of land-use setting on heavy metal accumulation in riverine sediments. Based on both total contents and geochemical fractions, heavy metal pollution, risk and toxicity were determined in riverine sediment cores from different land-use areas (mountain area- MA, farm area- FA, city area- CA, and industrial area- IA) of the Yang River Basin in North China. The results showed that FA had higher contents of riverine sedimentary Cu; CA had higher contents of Cd; IA had higher contents of both Cd and Zn. Most riverine sediments from FA and IA were contaminated with the investigated metals, although these concentrations were evaluated to have low potential ecological risk and no toxicity to benthic organisms. However, a high proportion of Cd in the B1 fraction of riverine sediments in IA indicating high risk should receive more attention. The B1 fraction largely determined the contamination, risk and toxicity levels associated with heavy metals in the riverine sediments of the Yang River Basin.

Impact of Syrian refugee camp on water, air and soil quality at Zaatari refugee camp/Jordan

Evaluation of the environmental situation inside Zaatarirefugee camp in terms of water, soil and air was done through classic monitoring as well as by the use of new technique (biofilm) to monitor heavy metal pollution in sewage system at Zaatari camp was done. Major ionic composition was determined for surface runoff, groundwater and wastewater whereas six heavy metals Zn, Mn, Cd, Cr, Cu and Pbwere evaluated for all samples. It was found that salinity of surface runoff decreased with rain events that the highest concentration was found at the beginning of the rainy season where the lowest was found at the end of the season.The salinity of wastewater was related to population density within the camp as it was highest in the oldest part of the camp where high population density exist and the lowest was in the new part of the camp with low population density. Heavy metal concentration in groundwater was low indicating that pollution from the refugee camp did not reach the groundwater resources of the area. All biofilm sampling of the same of wastewater samplingsites was done and it was found to be more efficient in wastewater monitoring as it represent longer period of monitoring than traditional method.For heavy metals concentration in the upper soil showed much higher concentration than lower soil indicating that the source of heavy metals are from the activities within the camp. For air concentration of all heavy metals were very low indicating that there is no source of heavy metals pollution in the area as the camp is located in a desert area and relatively far from major cities.

Source identification, spatial distribution pattern, risk assessment and influencing factors for soil heavy metal pollution in a high-tech industrial development zone in Central China

We determined the spatial distribution pattern, source, risk level and influencing factor of heavy metal pollution in a typical high-tech industrial development zone of Changsha, China. A total of 123 topsoil samples were excavated from 11 different land-uses. Quite strong pollution (Nemerow) occurred in the whole zone. The Igeo pollution levels were from slight to strong for these elements. Four primary components were extracted from PCA with 79.36% of total variance explained. It could be deduced from the primary components that Cu, Co, Ni normally resulted from electronic industry; As and Cr were affected by both industrial and natural source; Pb and Zn were originated from traffic activities; and Cd was correlated with the activities of General equipment manufacturing industry and pharmaceutical manufacturing industry. The concentrations of Pb and Zn decreased from densely populated areas to suburbs, while the high concentrations of the other six elements were mainly found in the industrial lands. Heavy metal concentration was in weak relationship with green cover ratio (GCR) and built time, inferring that increase of GCR might not be contributed to improvement of the heavy metal pollution. While a reasonable spatial planning of land use had positive effects on controlling heavy metal pollution.

Heavy metal pollution status in surface sediments of the Khajeh Kory River, north Iran.

This study aimed at exploring the extent of likely sources of heavy metal pollution in sediments of the Khajeh Kory riverbed in the north of Iran. In order to assess the heavy metal contamination, samples from surface sediments in 10 stations covering the river were collected and analysed to determine heavy metal contents including Cd, Cu, Ni, Pb, Zn, Mn, Co, Al, and Fe. Three guidelines were applied to assess the heavy metal contamination. Compared with the global average values, the calculated enrichment factors indicated high values for Fe, Mn, Cd, Co, and Cu, and very high values for Pb and Zn. The results obtained from principal component analysis revealed that the geogenic and anthropogenic sources were the main causes of the widespread enrichment of heavy metals in the riverbed sediments. The results suggested that the riverbed sediments were contaminated with heavy metals, which contribute to the freshwater toxicity in the ecosystem of the Khajeh Kory River.

Identification of the heavy metal pollution sources in the rhizosphere soil of farmland irrigated by the Yellow River using PMF analysis combined with multiple analysis methods-using Zhongwei city, Ningxia, as an example.

In recent years, with the frequent occurrences of heavy metal (HM) pollution in agriculture, the problem of HM pollution in farmland soil, especially in the areas irrigation by the Yellow River, has been attracted increasing attention because of the complex sources of pollution. Qualitative identification of pollution sources and quantification of their contributions to HMs in soil are the key links in the prevention and control of HM pollution. The contents of 11 heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sn, V, and Zn) in the rhizosphere soil of the Ningxia irrigation area were determined by inductively coupled plasma mass spectrometry (ICP-MS). Multiple methods were used for source identification, including positive matrix factorization (PMF) analysis combined with multiple other analyses (single factor index method (Pi), coefficient of variation(CV), correlation analysis(CA), enrichment factor(EF), and principal component analysis(PCA)). The results showed that (1) the over-standard rates of As, Cd, Cr, Mn, Pb, Sn, and Zn in the study area were 100%, of which Cd was seriously polluted, while As, Zn, and Sn were moderately polluted. (2) The HM contributions from irrigation and silt soil formed by the Yellow River sediment were the highest (42.45%), followed by the smelting industry and traffic pollution (16.06%). (3) The contribution of agricultural pollution to HMs in the region was 15.54%, in which As was mainly from pesticides and Cd was mainly from fertilizers.