玄武岩风化土壤中砷的地球化学行为及其影响因素
摘要
<p indent="0mm"> The toxicity of arsenic (As) and its hazards to humans and other organisms have long been a concern, recognized as a global health issue. Understanding the geochemical behavior of arsenic in natural weathering environments is crucial for assessing its potential ecological risks. In this study, an 8-meter-deep basalt profile formed by Quaternary volcanic eruptions in northeastern Leizhou Peninsula, Guangdong Province was sampled and analyzed for arsenic content, major/trace elements, and soil physicochemical properties. Results show that soil arsenic concentrations gradually decrease with depth, averaging at <sc>3.18 μg/g,</sc> which is higher than the crustal average but significantly lower than national and Guangdong provincial soil background values. External precipitation and litterfall constitute the primary arsenic input sources in surface soils. Organic matter in upper soils demonstrates significant arsenic adsorption capacity, while pH variations influence arsenic release and migration processes. In deeper layers, adsorption by iron (manganese) oxides and pH-dependent adsorption capabilities of aluminum oxides collectively control arsenic migration and distribution. Comprehensive analysis reveals that organic matter, secondary mineral adsorption, and formation of easily reducible Fe/Mn (oxy) hydroxides jointly regulate vertical arsenic migration in soils. Furthermore, the feasibility of using antimony isotopes to study arsenic migration factors was explored. The coordinated distribution patterns and migration controls of arsenic and antimony in soil profiles suggest the potential application of stable antimony isotopes for tracing arsenic sources and migration processes. This research fills critical knowledge gaps in arsenic migration studies of natural background areas and provides significant insights into understanding arsenic cycling processes in Earth′s surface systems.