Data-driven Insights into the Global Distribution and Determinants of Soil Arsenic Bioaccessibility

The bioaccessibility of arsenic (As) in soils is governed by soil physiochemical properties, contamination sources, and testing parameters. In this study, As bioaccessibility was evaluated in 1 457 soil samples collected worldwide. The bioaccessible fractions of As ranged from 0.05% to 89.0% in the gastric phase and from 0.15% to 83.2% in the intestinal phase. The mean gastric-phase As bioaccessibility decreased in the order of: industrial (31.3%)>urban (24.3%)>agricultural (23.5%)>mining/smelting (19.9%)>tailings (13.8%), whereas in the intestinal-phase values followed the order of: industrial (24.6%)>agricultural (22.7%)>mining/smelting (18.5%)>tailings (10.5%)>urban (10.1%). Bioaccessible As concentrations were significantly and positively correlated with total As and organic matter contents (P<0.001), but significantly and negatively correlated with Fe, Mn, and Al contents (P<0.001). Among the methodological parameters, pH and gastric pepsin concentration exerted significant effects on As bioaccessibility, while extraction duration had a negligible influence. The 95th percentile As bioaccessibility values-56.9%, 59.3%, 69.7%, 30.2%, and 65.4% for soils derived from tailings, mining/smelting, industrial, urban, and agricultural sources, respectively are recommended as reference values for refined human health risk assessment.