Single Pollution Index Research Articles

Impaired Soil Health in Agricultural Areas Close to Fe-Ni Mines on Euboea Island, Greece, Caused by Increased Concentrations of Potentially Toxic Elements, and the Associated Impacts on Human Health

Agricultural soils close to mining establishments may suffer from airborne pollution, due to excavation and transportation activities. To assess the impact of soil pollution from potentially toxic elements (PTEs) on soil and human health in agricultural areas close to Fe-Ni mines, 36 composite topsoil samples were collected from central Euboea Island, Greece. The soils were analyzed for their physicochemical properties and for total and bioavailable Ni, Cr, Co, Mn, Fe, Pb, Cu, and Zn concentrations; the BCR sequential extraction protocol was additionally applied to all samples. Soil enrichment caused by the metals and the implications of soil degradation on the ecosystem were evaluated using the calculation of single pollution indices (PI) and the potential ecological risk index (RI), respectively. The hazard index (HI) for non-carcinogenic metals and life cancer risk (LCR) for carcinogenic metals were used to appraise the human health risks. Extremely high, very high, and considerably high total concentrations of Ni, Cr, and Mn, respectively, were determined. Though most of the total amounts of metals in soil samples were found to be related to the residual fraction, the considerable portion extracted in the first two steps of the BCR process can be regarded as able to introduce toxicity issues in the local biota. High PI values of Cr, Co, and especially Ni point to severely polluted soils, and the mean RI values indicate a considerable risk for biota. HI values > 1 show increased possibilities for non-carcinogenic health issues in children, whereas the LCR values of Ni were above the critical limit, 1 × 10−4, for both children and adults.

Eco-Engineering Technologies and Achievements of Projects for Reconstructing Landscape Water from Aquaculture Ponds in Shanghai

The post-evaluation of ecological redevelopment is a good way of describing its achievements. In this paper, eco-engineering techniques, including hydrodynamic circulation reconstruction, water purification treatment, and aquatic ecosystem restoration, along with plant harvesting management, have been applied to reconstruct landscape water from aquaculture ponds. Both sediments and water quality were sampled and tested for basic physicochemical parameters and heavy metals. The ecological redevelopment of landscape water reconstructed from aquaculture ponds was evaluated using the single and Nemero comprehensive pollution index methods. The results demonstrate that nutrients, including organic matter and organic nitrogen and their ratio to sediments, were confirmed to be in a state of moderate pollution, while the ecological risk of heavy metal pollution was relatively low. Although the concentrations of total nitrogen and total phosphorus were significantly higher than those of other indexes, ammonia nitrogen, total nitrogen and total phosphorus, all presented obvious downward trends over time, and a majority of the water samples exhibited mild-to-moderate pollution levels. In general, this study provides a set of reference values for redeveloping water ecosystems from aquaculture ponds using eco-engineering technologies.

The Impact of Molybdenum Mining on Cd Pollution along Wenyu Stream in Qinling Mountains, Northwest China

Mining has brought many environmental problems to the surrounding soil, water, and air, with toxic elements contaminating surface water, threatening ecological balance and human health. This study selected the Wenyu watershed downstream from a large molybdenum mine in the Qinling Mountains as the study area, aiming to explore the impact of molybdenum mining on surface water quality. The content characteristics of Cd, Pb, Cu, Cr and Hg in surface water, sediment, and rock samples were analyzed by field sampling and chemical testing. The results showed only obvious Cd pollution. The pollution status and ecological risk level of surface water and sediment samples in the Wenyu Stream watershed were evaluated using the single pollution index method, geo-accumulation index method, and Hakanson potential ecological risk assessment method. Finally, the sources of Cd pollution and the impact of mining on Cd distribution in the Wenyu Stream were comprehensively discussed. The research results showed that Cd content in the Wenyu Stream was significantly affected by mining activity and the coefficient of variation of Cd content reached 99.44%. Among 22 surface water samples, 21 samples met the Class II water standard, indicating a clean overall water quality of the Wenyu Stream, and only one sample exceeded the Class II water standard with a mild pollution level. All 15 sediment samples were polluted to varying degrees and the most severely polluted sample had reached a moderate to strong pollution level. Most of the samples were at a moderate pollution level. The potential ecological hazard indexes of Cd content were at medium to very strong risk level, indicating that the overall sediment in the main ditch of the Wenyu Stream was under a strong ecological risk level. The main sources of Cd pollution, including acid mine drainage, regional geological background, sediment release, and atmospheric dry and wet deposition, were discussed.

Impact of Air Pollution on Respiratory Diseases in Typical Industrial City in the North China Plain

Air pollution can lead to the elevated incidence of various respiratory diseases, seriously endangering the health of urban residents. To better comprehend the association between urban air pollution and respiratory disease incidence, this study focused on Xinxiang City, a typical industrial city in the North China Plain, as the research object. By analyzing monthly air pollution index concentrations from 2018 to 2021 and confirmed cases of respiratory diseases, and incorporating meteorological factors as reference points, we conducted a correlation analysis between disease data and pollutant concentrations. We then constructed a Poisson regression model to obtain maximum likelihood estimates, which were used to predict the quantitative relationship between the incidence of respiratory diseases and air pollution indicators. The results showed that an increase of 1 μg/m³ in the average mass concentration of PM2.5, PM10, NO2, and SO2 in ambient air was associated with an elevated incidence of respiratory diseases by 0.2–1.4%, 0.7–1.6%, 3.7–8.2%, and 0.5–2.3%, respectively; meanwhile, a monthly mean mass concentration of CO increased by 1 mg/m³ led to a rise in pulmonary tuberculosis incidence by 2.9%. Additionally, based on health risk data following exposure to air pollution in Xinxiang City, it was confirmed that the impact of respiratory diseases as measured by the air quality composite index was more applicable than the single pollution index. Furthermore, there was a significant association between air pollution and the incidence of respiratory diseases.

Evaluation of water quality pollution and analysis of vertical distribution characteristics of typical Rivers in the Pearl River Delta, South China

Water quality comprehensive evaluation is an essential technical measure for water environment management and treatment. The previous research methods were often insufficient for studying black-sticking water bodies' formation and transformation mechanisms. In view of this, the single pollution index method and the comprehensive water quality identification index method (Iwq) were used to evaluate the pollution characteristics of rivers; the main pollution factors and sources of the watershed were determined by principal component analysis (PCA), and the vertical stratification characteristics of the water bodies were analyzed. The results showed that the total nitrogen (TN) values of pollutants in typical rivers in the Pearl River Delta were higher than the class V water quality standard, and the ammonia nitrogen (NH3−N) pollution level was the second-highest. TN concentration ranges from 4.27 to 19.83 mg/g, and NH3-N concentration ranges from 2.44 to 15.37 mg/g. In addition, in the monitoring of 15 rivers, 11 of them were the inferior V surface water, including five rivers' comprehensive water quality categories for black-stinking water bodies. This may be related to the process of water self-purification and pollutant transport, and rivers in densely populated areas are often subject to discharge from domestic sewage and industrial sewage. The results of the PCA extracted three principal components (PC), accounting for 88.825% of the total variance, with the first and third PCs controlled by human activities and the second PC influenced by natural sources. There is a more apparent vertical stratification of water bodies here in the typical rivers of the Pearl River Delta, and DO was an important factor affecting the vertical distribution of chemical oxygen demand (COD), NH3-N, TN, total phosphorus (TP), sulfide, Ferrum (Fe), and manganese (Mn). The severe lack of DO in deep water bodies led to elevated levels of NH3-N, Fe, and Mn, and gases such as hydrogen sulfide was released under anaerobic conditions, resulting in eutrophication and black-sticking levels in water bodies.

Ecological and human health hazards; integrated risk assessment of organochlorine pesticides (OCPs) from the Chenab River, Pakistan

Carcinogenic hazards to human health were investigated through oral and dermal exposure to organochlorine pesticides (OCPs) from water samples (n = 120) of River Chenab, Pakistan. The Pioneering study aimed to employ an integrated geographic information system (GIS) based geostatistical method for the determination of pollution load by GC-ECD from water of River Chenab. The residual levels of OCPs detected from water samples ranged from 0.54 to 122 ng L−1 with significant prevalence of DDE and α-HCH. Results of the Nemerrow pollution index (NeI), single pollution index (SPI), and comprehensive pollution index (CPI) reflected the downstream zone a stern pollution risk zone. The spatial distribution pattern through geostatistical approaches also revealed significantly higher (p < 0.05) OCP levels in the downstream zone. Risk quotient (RQCCC) of surface water quality with respect to heptachlor epitomized a high level of risk (RQCCC > 1). Non-carcinogenic human health risk (Σ HQ) assessment ranged from 8.39 × 10−9 to 1.7 × 10−3, which represented a marginal risk through oral and dermal exposure. However, carcinogenic risks by oral exposure route were ranged from 3.57 × 10−11 to 4.46 × 10−6. Estimated cancer risk (ΣCR) exhibited a considerable carcinogenic risk posed by heptachlor, α-HCH and dieldrin. It is suggested to employ an immediate mitigation strategy for the constant discharge of OCPs in the studied area.

Heavy Metal Pollution and Risk Assessment of Vegetables and Soil in Jinhua City of China

To understand the heavy metal (Cd, Cr and Pb) pollution situation and exposure risk of the vegetables and soil in Jinhua City, soil–vegetable samples collected from three districts of Jinhua City were analyzed in detail, and the risks of heavy metal concentration in vegetable and soil were evaluated using the single pollution index, Nemerow pollution index, Hakanson potential ecological index and a health risk assessment. The results indicate that: (1) The soil in Jinhua City is mainly polluted by Cd, and the BCF of heavy metals in vegetables was leafy vegetables &gt; rootstalk vegetables &gt; solanaceous vegetables. (2) Heavy metals had slight pollution in the surrounding environment, and the ecological risk of soil heavy metals in the sampling area was generally at a low risk level. (3) Children are more likely to suffer from non-carcinogenic risks; Cr is the main source of this risk (HQCr = 0.74). More than 90% of vegetables in the sampling had cancer risk, adults are more likely to suffer from carcinogenic risks, and Cd is the main source of potential cancer risk (TCR = 4.34 × 10−4). Therefore, in our study area, Cd is the main factor of soil pollution that can cause potential cancer risk through vegetable enrichment, and Cr is the main factor causing the non-carcinogenic risk of leafy vegetables.

Risk Assessment of Heavy Metals in Soils from Four Different Industrial Plants in a Medium-Sized City in North China.

Laboratory experiments were carried out to analyze 39 soil samples collected from four industrial areas in Xuzhou City using inductively coupled plasma mass spectrometry and atomic fluorescence spectrometry. The descriptive statistics of heavy metals (HMs) in the soil profiles showed that the HM content at three depths was highly variable, and most coefficients of variation (CVs) showed moderate variability. The enrichment of Cd at all depths exceeded the risk screening value, and Cd pollution occurred in four plants. The enrichment of the other HMs at three depths was mainly concentrated in the pharmaceutical plant A and chemical plant C. It was found that the different HMs had different vertical distribution characteristics. For the different industrial plants, the raw materials and products not only made the spatial distribution characteristics of the HMs different, but also caused the HM types and contents to differ. The average single pollution indices of Cd in plant A, iron-steel plant B, and plant C indicated a slight pollution level. The other seven HMs in A, B, and C and all HMs in chemical plant D belonged to the safe category. The mean values of the Nemerow pollution index in the four industrial plants belonged to the warning category. The analysis showed that none of the HMs posed potential noncarcinogenic health risks, and only the carcinogenic health risks of Cr in plants A and C were unacceptable. The carcinogenic effect of Cr through the inhalation intake of resuspended soil particulates and that of Cd, Ni, and As via direct oral ingestion were the main exposure pathways.

Comprehensive GIS based risk surveillance of organochlorine pesticides (OCPs) in edible fish species of River Chenab, Pakistan

The present study was conducted to evaluate Carcinogenic (TR) and non-carcinogenic (THQ) human health risk of organochlorine pesticides (OCPs) in three edible fish species (Labeo boga, Channa marulius and Wallago attu) of River Chenab, Pakistan using USEPA human health risk assessment model. Holistic GIS (Geographic information system) based Geo-Statistical approach has been employed for the first time in River Chenab, Pakistan to categorize contaminated risk zones of OCPs based on single pollution index. The ∑OCPs concentrations in fish species were ranged from 5.09 to 414 ng/g with the prevalence of dieldrin. Results of single pollution index of DDE, aldrin, dieldrin and ∑endosulfan revealed River Chenab as polluted and risk zone area. Distribution pattern assessed significantly higher (p < 0.05) concentrations of OCPs in downstream area suggesting substantial pollution of surrounded industrial region. The human health risk assessment depicted no harmful non-carcinogenic (THQ) risk except for ΣOCPs concentration of C. marulius. Significant carcinogenic (TR) health risk exhibited by all examined OCPs from maximum of the studied sites. Therefore, the high carcinogenic human health risk had highlighted an immediate removal of continuous disposal of OCPs in the River Chenab.

Seasonal variation and risks of potentially toxic elements in agricultural lowlands of central Cameroon

Intensive urban agriculture is expanding in Cameroon, which increases the risks of environmental pollution, particularly in the lowlands. This study assessed the seasonal characteristics of some potentially toxic elements and their ecological risks during the dry and wet seasons in urban agricultural soils in four lowlands in Yaoundé. The area and seasonal variation of some potentially toxic elements (Cu, Pb, Zn, Cd, Cr, and Ni) were evaluated using mixed-effects modeling. The pollution status of these elements in the soil was evaluated and interpreted using parameters such as the single pollution (SPI) and Nemerow composite pollution (NCPI) indices. In addition, the effect of these metals in the environment was assessed using the potential ecological risk index (PERI). The distribution of all the studied elements showed an area effect, while a seasonal effect was only noticeable for Cu. The concentration of Cu, Pb, and Zn was higher than the recommended threshold values in one of the areas sampled, while Cr exceeded these threshold values in all areas during both seasons. Cr exhibited the highest SPI among all studied elements during the dry and wet seasons in all areas. Except for the NCPI in one area, where grade V (strong) soil pollution was recorded during the wet season, the soil from all the study areas exhibited a slight pollution level (grade III) with a mean NCPI between 1 and 2. The PERI value of all areas was below the reference values during both seasons, suggesting an overall low potential contamination risk of the soil biota. The results indicate that preventive action to limit the heavy metal contamination in the lowlands of Yaoundé needs to be taken, for instance, through the promotion of more sustainable use of agrochemicals like pesticides and mineral fertilizers.

Assessment of Potentially Toxic Element Contamination in the Philippi Peatland, Eastern Macedonia, Greece

The Philippi peatland is considered the biggest peat deposit in the Balkan Peninsula and one of the deepest in the world. The purpose of this study was to access the impact of eight potentially toxic elements (PTEs), i.e., As, Se, Pb, Cr, Ni, Zn, Mn and Cu, on the local environment. PTE content was determined in corn grains and surface soil samples collected from 16 sites in the peatland, and pollution indices were calculated to evaluate the environmental risks. Soil organic matter ranged between 93 and 557 g kg−1 soil, whereas the soil pH was &gt;7, classifying the soils as neutral to slightly alkaline. Mean PTE contents in soil samples were 24.6 mg kg−1 soil for As, 1.68 mg kg−1 soil for Se, 113 mg kg−1 soil for Pb, 32 mg kg−1 soil for Cr, 36.3 mg kg−1 soil for Ni, 141.4 mg kg−1 soil for Zn, 35.5 mg kg−1 soil for Cu and 845 mg kg−1 soil for Mn. In corn grain samples, 0.06 mg kg−1 grain for As, 0.14 mg kg−1 grain for Se, 1.34 mg kg−1 grain for Cr, 0.69 mg kg−1 grain for Ni, 27 for Zn, 8.4 mg kg−1 grain for Cu and 3.2 mg kg−1 grain for Mn were recorded. No Pb was detected in the corn grains. The bioaccumulation factor (BF) was high for Cu, Zn and Se, indicating increased mobility of these elements in the soils and preferential plant uptake. For most soil samples, the geoaccumulation index (Igeo) and single pollution index (PI) showed low to moderate contamination. However, Igeo and PI values of Se in many sampling sites and of Pb and Zn in few were substantially increased, pointing to heavily contaminated soils. According to potential ecological risk (RI), the PTE content in the peat soils of Philippi imposes low to moderate risk on the environment.

Risk Assessment of Heavy Metal Pollution in Farmland Soils at the Northern Foot of the Qinling Mountains, China.

To provide scientific basis for the prevention and control of heavy metal pollution, a field investigation, sample collection and analysis of the heavy metal content in farmland soils at the northern foot of the Qinling Mountains were conducted. Based on the comparative analysis of the single pollution index method, the Nemerow comprehensive pollution index method, the geological accumulation index method, the potential ecological hazard index method, and the geological accumulation index method were used to comprehensively analyze and evaluate the risk of soil heavy metal pollution. The results showed that the heavy metal pollution of farmland soil at the northern foot of the Qinling Mountains was severe, among which Hg and Cr pollution was relatively obvious. Taking the soil screening values of agricultural land as the standard, the quantity of element Hg in agricultural soils at the northern foot of the Qinling Mountains was higher than the relevant screening value. In the two sample sites investigated, the intensity of the heavy metal accumulation index in Baoqizhai Village was Hg > Cr > Cu > As > Pb, and in Dayangyu Village it was Cr > Cu > As > Pb. Among them, in Baoqizhai Village it shows the heavy pollution caused by Hg (Igeo= 3.42) and the light pollution caused by Cr (Igeo < 1) in the two areas. Hg is mostly affected by mining activities and its atmospheric subsidence. At the same time, Cr is mainly derived from the weathering of rock parent material and is also affected by anthropogenic factors to a certain extent. The accumulation of heavy metals in the farmland soil around the northern foot of the Qinling Mountains was relatively high, posing a threat to the surrounding soil environment. Therefore, it is urgent to control farmland soil environmental pollution.

Application of individual and integrated pollution indices of trace elements to evaluate the noise barrier impact on the soil environment in Wrocław (Poland)

Trace elements emitted by road transport cause long-term contamination of road soils. This study showed the effect of the noise barrier on the spatial distribution of metals in soils at the City Centre Ring Road in Wrocław (Poland). Samples were taken along the barrier every 150 m and across the screen at distances of 0.5, 2.5, 5 (only on the left side), 10, 20, and 50 m from the noise screen on both sides of road no. 5. The contamination of soils was assessed with the use of commonly used individual pollution indices, integrated pollution indices based on the PI index or metal concentrations, and a potential ecological risk index (RI). The geoaccumulation index (Igeo) and the single pollution index (PI) indicate moderate contamination of soils by Cu, Pb, and Zn at most measuring points. The significant risk was reported from Cd in all samples. Integrated pollution indices, especially the PI_Nemerow, PI_avg, and RI confirm the poor quality of studied soils. The presence of elements in soil is related to anthropogenic factors. The spatial distribution of pollution indices and results of statistical analysis (HCA) indicate that Cr and Ni are of natural origin. Remaining elements (Cd, Pb, Cu, Zn) are of mixed origin with a large share from car transport (the significant Spearman’s correlation coefficients). In the case of cadmium, dendograms suggest the existence of an additional anthropogenic source, which is also confirmed by moderately strong correlations of this element with other metals.

Evaluation of sediment and water quality of Ismailia Canal for heavy metal contamination, Eastern Nile Delta, Egypt

Several environmental indicators were used to evaluate the water and sediment quality of Ismailia Canal for heavy metal contamination. The average concentrations of heavy metals in water and sediments (μg/L and μg/g) were Pb (1.36–31.78), Fe (0.95–5124), Ni (0.45–32.14), Cu (0.34–32.64), Zn (0.28–117.77), Co (0.078–29.40), and Mn (0.044–194.83), respectively. Based on heavy metal pollution index values, 75% of the sediment samples fell within low pollution, while water pollution index and water contamination degree revealed excellent and low contamination for all water samples, respectively. Single pollution indices of sediment indicated high contamination with Pb and considerable risk with Cd. The higher levels of metals in some samples might be originated mostly from anthropogenic sources related to industrial, agricultural, and urbanization activities along the investigated canal. However, Ismailia Canal sediments were unpolluted with metals, or no metal pollution and all average concentrations of the investigated heavy metals were less than the maximum admissible concentration of the world health organization.

Spatial Distribution Characteristics of Heavy Metals and Pollution Analysis Methods

With the rapid development of urban economy and the continuous increase of urban population, the discharge and improper disposal of a large number of industrial wastes, urban domestic garbage, sludge and other pollutants have led to the continuous accumulation of heavy metals in the soil, which has increased the pollution load of heavy metals in the soil, leading to the increasingly serious heavy metal pollution of urban topsoil in China. Heavy metal pollution of urban soil is one of the important indicators that can effectively reflect the status of urban environmental pollution. Therefore, the verification of urban soil environment anomalies and the application of verification data to urban environmental quality assessment, as well as the study of the evolution model of human activities affecting urban soil environment, have increasingly become the focus of attention. Based on the analysis of a large number of relevant documents and previous work, the sources, hazards and pollution status of soil heavy metal pollution in some regions of China are briefly summarized, and the characteristics of five commonly used assessment methods of soil heavy metal pollution (single pollution index method, comprehensive pollution index method, geo accumulation index method, potential ecological risk index method, principal component analysis method) are briefly analyzed and summarized, It is expected to provide some reference for the investigation and treatment of soil pollution.

Soil Heavy Metal Content and Enzyme Activity in Uncaria rhynchophylla-Producing Areas under Different Land Use Patterns.

In this study, we investigated the content of soil heavy metals, the level of heavy metal pollution and the characteristics of soil enzyme activity under three different land use patterns of Uncaria rhynchophylla base, forestland and wasteland in Jianhe County, Qiandongnan Prefecture, Guizhou Province, revealing the intrinsic correlation between heavy metal content and soil enzyme activity to reveal the relationship between soil enzyme activity and heavy metal content under different land use patterns in the Uncaria rhynchophylla production area. The results showed that soil Cd and Hg contents in Uncaria rhynchophylla base both exceeded the national soil background value. The single pollution index indicated that Cd had the greatest contribution to Pn, and the comprehensive pollution index (Pn) demonstrated no heavy metal pollution in the soil of Uncaria rhynchophylla-producing areas. Under different land use patterns, the enzyme activity was forestland > wasteland > Uncaria rhynchophylla base, and catalase and acid phosphatase activities presented significant spatial differences (p < 0.05). The correlation between soil enzyme activity and heavy metal content was uncertain due to the changes in land use patterns and heavy metal species. The proportions of positive correlation and negative correlation between soil enzyme activity and heavy metals in Uncaria rhynchophylla base were 50%, respectively. In the forestland, soil enzyme activity was positively correlated with heavy metals, while in the wasteland, soil enzyme activity was negatively correlated with heavy metals. This study revealed that the changes in heavy metal content should be focused on for the soil quality in Uncaria rhynchophylla-producing areas under different land use patterns. The results of the study provide some basic theoretical references for the improvement of soil quality in the production area of Uncaria rhynchophylla under different land use practices.

Pollution Levels and Risk Assessment of Heavy Metals in the Soil of a Landfill Site: A Case Study in Lhasa, Tibet.

As an important ecological security barrier in China, the ecological environment of Tibet has aroused widespread concern domestically and overseas. Landfills are a major solid waste treatment approach in Tibet but also cause severe environmental pollution. To date, there are no studies related to the pollution risk of landfills in Tibetan areas. This study investigated the pollution levels, ecological risk, health risk, and possible pollution sources of eight heavy metals in the soils around a landfill site in Lhasa, Tibet. The results indicated that the concentrations of heavy metals in soil were relatively low, only cadmium (Cd), arsenic (As), copper (Cu), chromium (Cr), zinc (Zn), nickel (Ni), and lead (Pb) were 1–2 times higher than the corresponding background value. The values of the single pollution index and geo-accumulation index show that the study area is most seriously polluted by Cd and As. Based on the Nemerow pollution index and the pollution load index, over 83.3% and 8.33% of soil sampling sites had light and moderate contamination levels. According to the results of potential ecological risk evaluation, the potential ecological risk of heavy metals in soil was very low, and only one out of the 72 sampling sites exhibited considerable ecological risk. Cd, As, and mercury (Hg) served as the dominant ecological risk contributors and contributed over 45.0%, 14.1%, and 18% of the ecological risk. The results of the health risk evaluation showed that adults have a higher risk of cancer (1.73 × 10−5), while the non-carcinogenic risk for adults was low. Waste disposal activities and construction activities have a significant influence on soil heavy metal concentrations, causing a higher pollution level in the southeast part of the landfill site in Lhasa.

Heavy Metal Contamination and Ecological Risk Assessment in Soils of the Pawara Gold Mining Area, Eastern Cameroon

Pawara area is a mining district in the eastern region of Cameroon. Mining in the area is generally artisanal and semi-mechanized, practiced by the local miners and immigrants from neighboring African countries and China. The lack of strict regulations and control of mining activities permits the miners to use illegal substances, especially Hg in gold separation. These expose the area to toxic and heavy metals pollution. This study highlights the source of heavy metals concentration in the Pawara soils and the potential adverse effects of Hg on gold separation to the environment and health. Three mining sites and one control site were investigated, namely Site A, Site B and Site C. The control Site 0 (background) is an area where no mining and agricultural activities have taken place. Soil samples were collected at depth of 20 cm, with six from each site (24 samples). Samples were analyzed for Al, Cd, Cr, Cu, Fe, Hg, Pb, Cd and Zn content using atomic absorption spectrophotometry in a graphite furnace. The metals, except for Fe, show high values for all three sites exceeding the background levels in the soils. Hg shows the highest concentration on Site A with a value of 1590 mg kg−1. Pb is highest on Site B with a concentration of 12,274 mg kg−1. The contamination degree was assessed with the help of contamination indices (Igeo—index of geo-accumulation; PLI—pollution load index; RI—potential ecological risk; Eri—ecological risk; Pi—single pollution index; CF—contamination factor) and all parameters show a high degree of contamination on all three sites compared to the control site. Hg, Pb, Cd, Cr and Cu as single pollutants show the highest ecological risk on Site A and Site B where intense mining is taking place. The absence of industrial and large-scale agricultural activities in the Pawara area, the nonexistence of contaminants on the control site and the presence of contaminants on Site C where farming is high and mining is low jointly show that the discharge of mine wastes onto the soils and stream channels are the main source of contaminants and potential pollutants of the Pawara ecological environment.

Characterization and Risk Assessment of Heavy Metals in Surface Sediments From Jian and Moyang Rivers in Western Guangdong

The river environment is complex and receives a variety of contaminants from numerous sources that are persistent, bioaccumulative, and toxic. The distribution, source, contamination, and ecological risk status of Zn, Pb, Cu, Ni, Cr, and Cd were evaluated in the surface sediments at 45 sites on the Moyang and Jian rivers in Western Guangdong, China. Single pollution indices, including contamination factor (CF) and enrichment factor (EF), revealed that Zn, Pb, Ni, Cu, and Cd showed moderate to significant enrichment. To overcome the limitation of the single element indices, a range of sediment quality indices, including modified contamination index (mCd), pollution index (PI), and modified pollution index (MPI), were utilized to ascertain the sediment quality. The sediment in the study area is deemed to be slightly to extremely polluted. The sediment quality guidelines (SQGs), potential ecological risk index (RI), and modified ecological risk index (MRI) were used to assess possible ecological risks. According to the SQGs, Pb, Ni, and Cu have the potential to induce biological effects. The RI indicated that the sediment poses a low ecological risk. However, the MRI indicated that the ecological risk of the sediment was moderate to very high. The accuracy of the single and multi-element indices and ecological risk assessment were evaluated in the river using the principal component analysis (PCA) and cluster analysis (CA), showing an anthropogenic impact. Results demonstrate the need to pay attention to the ecological environment of small rivers, which are sensitive to their surroundings.

Combination of enrichment factor and positive matrix factorization in the estimation of potentially toxic element source distribution in agricultural soil.

The study intended to assess the level of pollution of potential toxic elements (PTEs) at different soil depths and to evaluate the source contribution in agricultural soil. One hundred and two soil samples were collected for both topsoil (51), and the subsoil (51) and the content of PTEs (Cr, Cu, Cd, Mn, Ni, Pb, As and Zn) were determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The concentrations of Zn and Cd in both soil horizons indicated that the current study levels were higher than the upper continental crust (UCC), world average value (WAV), and European average values (EAV). Nonetheless, the concentration values of PTEs such as Mn and Cu for EAV, As, Cu, Mn, and Pb for UCC, and Pb for WAV were lower than the average values of the corresponding PTEs in this study. The single pollution index, enrichment factor, and ecological risk revealed that the pollution level ranged from low to high. The pollution load index, Nemerow pollution index, and risk index all revealed that pollution levels ranged from low to high. The spatial distribution confirmed that pollution levels varied between the horizons; that is, the subsoil was considered slightly more enriched than the topsoil. Principal component analysis identified the PTE source as geogenic (i.e. for Mn, Cu, Ni, Cr) and anthropogenic (i.e. for Pb, Zn, Cd, and As). PTEs were attributed to various sources using enrichment factor-positive matrix factorization (EF-PMF) and positive matrix factorization (PMF), including geogenic (e.g. rock weathering), fertilizer application, steel industry, industrial sewage irrigation, agrochemicals, and metal works. Both receptor models allotted consistent sources for the PTEs. Multiple linear regression analysis was applied to the receptor models (EF-PMF and PMF), and their efficiency was tested and assessed using root-mean-square error (RMSE), mean absolute error (MAE), and R2 accuracy indicators. The validation and accuracy assessment of the receptor models revealed that the EF-PMF receptor model output significantly reduces errors compared with the parent model PMF. Based on the marginal error levels in RMSE and MAE, 7 of the 8 PTEs (As, Cd, Cr, Cu, Ni, Mn, Pb, and Zn) analysed performed better under the EF-PMF receptor model. The EF-PMF receptor model optimizes the efficiency level in source apportionment, reducing errors in determining the proportion contribution of PTEs in each factor. The purpose of building a model is to maximize efficiency while minimizing inaccuracy. The marginal error limitation encountered in the parent model PMF was circumvented by EF-PMF. As a result, EF-PMF is feasible and useful for apparently polluted environments, whether farmland, urban land, or peri-urban land.