Bioaccessibility of Arsenic in Mining-Impacted Circumneutral River Floodplain Soils

详细信息    查看全文

• 作者：Christian Mikutta ; Petar N. Mandaliev ; Nina Mahler ; Tsvetan Kotsev ; Ruben Kretzschmar
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：November 18, 2014
• 年：2014
• 卷：48
• 期：22
• 页码：13468-13477
• 全文大小：477K
• ISSN：1520-5851

文摘

Floodplain soils are frequently contaminated with metal(loid)s due to present or historic mining, but data on the bioaccessibility (BA) of contaminants in these periodically flooded soils are scarce. Therefore, we studied the speciation of As and Fe in eight As-contaminated circumneutral floodplain soils (鈮?1600 mg As/kg) and their size fractions using X-ray absorption spectroscopy (XAS) and examined the BA of As in the solids by in-vitro gastrointestinal (IVG) extractions. Arsenopyrite and As(V)-adsorbed ferrihydrite were identified by XAS as the predominant As species. The latter was the major source for bioaccessible As, which accounted for 5鈥?5% of the total As. The amount of bioaccessible As increased with decreasing particle size and was controlled by the slow dissolution kinetics of ferrihydrite in the gastric environment (pH 1.8). The relative BA of As (% of total) decreased with decreasing particle size only in a highly As-contaminated soil 鈭?which supported by Fe XAS 鈭?suggests the formation of As-rich hydrous ferric oxides in the gastric extracts. Multiple linear regression analyses identified Al, total As, C_org, and P as main predictors for the absolute BA of As (adjusted R² 鈮?0.977). Health risk assessments for residential adults showed that (i) nearly half of the bulk soils may cause adverse health effects and (ii) particles <5 渭m pose the highest absolute health threat upon incidental soil ingestion. Owing to their low abundance, however, health risks were primarily associated with particles in the 5鈥?0 and 100鈥?00 渭m size ranges. These particles are easily mobilized from riverbanks during flooding events and dispersed within the floodplain or transported downstream.