| In the past few years,heavy metal pollution has become an increasingly prominent problem,posing a significant threat to the soil environment and human health.Therefore,research on the contamination level,spatial distribution,source analysis,and risk assessment of heavy metal pollution in soils in key areas is crucial.This study took the main grain production area in Niujing Town,Jiangmen City,Guangdong Province as the research object.In this study,we employed the radial sampling method to establish 232 sampling points across the study area.We then analyzed the concentrations of 14 elements,including As,Cu,Pb,Zn,Cd,Ni,Cr,N,P,K,Mg O,Co,Si O2 and SOM,in the surface soil samples collected from these points.Based on the results,we systematically assessed the enrichment status and pollution level of heavy metals using several methods,including the enrichment factor method（EF）,the pollution factor method（CF）,the index of geoaccumulation（Igeo）and new nemero index（INI）.Our findings provide novel insights into the environmental quality of the study area and can inform future policy decisions regarding its management.The source identification and analysis of soil heavy metal pollution were qualitatively and quantitatively determined through correlation analysis,absolute principal component analysis-multiple linear regression（APCS-MLR）,and positive matrix factorization（PMF）models.The advantages and disadvantages of different source identification models were discussed by comparing the results of the two models.Based on source identification,a health risk assessment model was used to quantitatively evaluate the contribution of different pollution sources to human health risk by referring to the behavioral patterns of different populations in the study area.The relevant results are as follows:（1）The average p H and SOM of the soil in the study area are 5.63 and 2.48%,respectively,indicating that the soil in the study area is generally acidic and rich in organic matter.This study used descriptive statistical analysis to analyze the content of 232surface soil elements.The local background value was calculated by the method of mean deviation,and the calculated local background value was compared with the average value of Guangdong Province and the national average value.The concentrations of Cd,Pb,and Zn in the local background were found to be higher than the average values reported for Guangdong Province.Moreover,the local background value of Pb was also observed to be higher than the national average value.The average measured content of most elements in the study area was higher than their local background values,and the distribution was uneven in the study area.The coefficients of variation for the elements As,Pb,Zn,Cd,and Co were all found to be greater than 50%,indicating a high degree of variability and suggesting significant anthropogenic interference.（2）This study used EF,CF,and Igeo to analyze the pollution levels of the eight main heavy metal elements in Niujiang Town.The results showed that there were significant enrichment of As,Pb,Zn,and Cd.For pollution factors,more than half of the sampling sites for As,Cu,Pb,Zn,Cd,Cr,and Co elements were at moderate pollution level or above.Through the geo-accumulation index analysis,it was found that the overall pollution level in the study area was low,but there were some individual sampling sites and elements with pollution.（3）This study used the APCS-MLR and PMF models for source analysis.The APCS-MLR model identified three sources:agricultural and traffic sources（37.93%）,mixed sources（40.60%）,and unknown sources（21.47%）.The PMF model results showed natural sources（32.58%）,atmospheric deposition sources（11.73%）,agricultural activity sources（23.75%）,and transportation sources（31.94%）.The comparison of the results of the two receptor models shows that the PMF model is more reliable for source analysis of the main pollutants in the surface soil in the study area.（4）The objective of this study was to assess the potential health risks to humans associated with soil in the study area.The results demonstrated that oral ingestion was identified as the most significant health risk pathway for both adults and children,among the three pathways evaluated.The non-carcinogenic risks linked to eight heavy metals were assessed,and it was concluded that the risks were within the safe range of exposure for both adults and children,with hazard quotients below 1.Overall,the findings suggest that exposure to soil in the study area does not pose a significant non-carcinogenic health risk to humans.The total carcinogenic risks for adults and children were 2.07E-05 and3.58E-05,respectively,which were within the acceptable range for human beings.Through comparative analysis,it was found that children were more susceptible to the impacts of non-carcinogenic and carcinogenic risks than adults,and we should strengthen health education and protection for children.（5）Based on source apportionment results,this study proposed the PMF-IRI and PMF-HHR models to quantitatively evaluate the potential ecological and human health risks under different sources.The proportion of different sources in the total potential ecological risk value was ranked as follows:agricultural activity source（33.52%）>transportation source（28.34%）>natural source（26.88%）>atmospheric deposition source（13.23%）,and Cd was the priority control element for potential ecological risk.In the PMF-HHR model,the level of non-carcinogenic risks contributed to by different sources for adults and children was ranked from high to low as follows:transportation source>atmospheric deposition source>natural source>agricultural activity source.Pb and As were the key elements for controlling non-carcinogenic risks in the study area.In contrast to non-carcinogenic risks,the ranking of the carcinogenic risks caused by heavy metal elements in the surface soil of the study area for adults and children was as follows:natural source>transportation source>agricultural activity source>atmospheric deposition source.Cu and Cr were the key elements for controlling carcinogenic risks in the study area. |
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