Analysis Of The Sources Of Heavy Metals In The Soil Of The Main Rice-producing Area (Duhu) In Jiangmen City And The Quality Evaluation

Duhu Town,located in the southeast of Jiangmen City,Guangdong Province,is a rice-producing town that serves as a national-level agricultural comprehensive project development zone and a demonstration base for high-yield and high-quality rice planting.In order to ensure the healthy and green development of local agriculture,it is essential to identify the current quality status of the soil in Duhu Town,including the sources,contents,and spatial distribution characteristics of heavy metal elements.To this end,the plum blossom sampling point method was employed to collect163 surface soil samples in the study area,and the contents of 20 analysis indicators were measured,including 9 heavy metal elements（Pb,Co,Cu,Fe,Zn,Cr,Ni,Cd,and As）and 11 other indicators（K₂O,Na₂O,Si O₂,P,Al₂O₃,Ti,Corg,p H,Se,Mg O,N）.Results showed that the soil environment in the study area was generally acidic,with rich total nitrogen and organic matter content.However,the available phosphorus and available potassium content were generally lacking,and the area lacking in these nutrients accounted for more than 75%of the study area.Additionally,while the contents of available copper,available zinc,and available iron were abundant,the overall soil fertility of the surface soil was still at a low level.The background values of the nine heavy metal elements in the surface soil of the study area were higher than the geochemical background values of Guangdong Province and the national geochemical background values,with the multiple of Cd element being the highest.However,the average contents of Pb,Zn,Cr,Co,and Fe were lower than the background values of the surface soil in the study area.Some of the samples exceeded the second-class standard limit of the national standard for As,Cu,Cd,and Ni,indicating human activities as a source of these four elements,mainly located in the east of the study area.The single-factor pollution index of the nine heavy metal elements in the surface soil of the study area showed that As,Cu,Cd,and Ni were slightly polluted,with Cd and Ni pollution areas being the largest.Overall,the surface soil of the entire study area was classified as Class II soil,with 93.5%of the area covered,and the rest as Class III soil.The PMF model and ACPS-MLR model were used in this source apportionment study.Comparing the two models in terms of identified source types,number of sources,contribution rates,and applicability,the PMF model was found to be more suitable for the study area.Overall,both models indicate that the main sources of heavy metal elements in the surface soil of the study area are geological background.The PMF model identified four sources related to heavy metal elements:1)acidic rock source,2)granitic source,3)agricultural activities source,and 4)a mixture of acidic rock and agricultural activities.Among these sources,Cr,Fe,Co,and Zn were exclusively attributed to the acidic rock source.Pb was solely associated with the granitic source.As,Cu,Ni,and Cd were attributed to a mixture of acidic rock and agricultural activities,with Cd predominantly originating from agricultural sources.