广州某地质高背景地块土壤砷污染特征及成因分析OA

Arsenic(As)is widely present in soils of geogenic high-background areas,and its elevated concentrations and diverse chemical forms may pose potential ecological and human health risks.This study aims to elucidate the spatial distribution characteristics and enrichment mechanisms of As in a representative geogenic high-background area.A total of 2 336 soil samples were systematically collected from depths of 0-12 m in a high-background site located in Guangzhou,China.Stratified statistical analysis was applied to examine the vertical variation trends of As concentrations.Based on regional geological survey data,the study area was classified into three lithological units.From lithologies representing high,medium,and low As concentrations,nine representative samples were selected to conduct sequential extraction experiments for As speciation analysis.Meanwhile,Spearman correlation analysis was performed to explore the relationship between As and Fe,and mineralogical characterization techniques including X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and scanning electron microscopy coupled with energy-dispersive spectroscopy(SEM-EDS)were employed to identify the mineral associations and binding states of As.The results show that As concentrations in soils systematically increase with depth,indicating a pronounced enrichment in deeper horizons.Arsenic primarily occurs in the residual and Fe oxide-bound fractions,while the proportion of labile or bioavailable forms remains low,reflecting a contamination pattern characterized by"high total content-low mobility".A significant positive correlation was observed between As and Fe concentrations(r=0.733,p<0.001).Mineralogical analyses further confirm that As mainly resides in mineral aggregates dominated by Fe and Al oxides.Overall,this study reveals the vertical distribution patterns and geochemical mechanisms of As in soils from geogenic high-background regions,providing a scientific basis for environmental risk assessment and pollution prevention in naturally As-enriched areas.