Geochemical behavior and potential health risk of heavy metals in basalt-derived agricultural soil and crops: A case study from Xuyi County, eastern China.

Basalt-derived agricultural soil is widely distributed around the world and is extensively used as a medium to plant many kinds of crops. Weathering of basalt can release heavy metals into the soils and may cause health risks via the food chain. However, the geochemical behavior and the potential human health risks of heavy metals remain poorly understood in these agro-systems. In this study, basalt bedrock, paired topsoil and crops (wheat and rice) samples were collected from a basaltic area located in Xuyi County, eastern China. Concentrations and bioavailability of heavy metals in the basalt-topsoil-crop system were measured to determine their geochemical behavior during the weathering and transfer processes as well as their potential risk to human health. Our results showed that basalt and topsoil were characterized by high levels of Ni, Cr and Zn. Topsoil and crop grains were highly polluted by Ni, and Ni accumulated more readily in rice grains than in wheat grains. Nickel, a high-risk metal in topsoil was mainly derived from the basalt bedrock, and its enrichment in topsoil was significantly related to the Fe oxide content of the soils. The accumulation of Ni in crop grains was mainly controlled by soil pH, and the 0.01 M CaCl2 extractable Ni was a good indicator in predicting Ni accumulation in crop grains. Risk analysis revealed that there are significant health risks to local inhabitants if rice grains contaminated with heavy metals are ingested. To our best knowledge, this is the first study to investigate the flow of heavy metals in a basalt-topsoil-crop-human system that focuses on geochemical behavior and human health risk. This study will aid the strategic design of evaluation and remediation protocols for basaltic soil.