Chemical Forms of Arsenic and Selenium Leached from Mudstones

Batch leaching experiments were conducted to elucidate the leaching behaviors and chemical forms of arsenic (As) and selenium (Se) from excavated mudstones. The results showed that As and Se concentrations in the leachate were higher than the environmental standards (10 μg/L), and that the major chemical forms of As and Se were arsenate (As(V)) and selenate (Se(VI)), respectively. Consecutivebatch leaching experiments showed that the major chemical form of As was As(V) regardless of the number of extraction whereas that of Se changed from Se(VI) to selenite (Se(IV)) with the number of extraction. These results agreed with the calculated results by geochemical modeling. Understanding the major chemical species of hazardous elements leached from mudstones is valuable in the mitigation of these potential sources of contamination.