Impact of arsenic releaching from excavated rock after once-arsenic leaching on potential arsenic leaching

Massive quantities of naturally arsenic-containing rocks are excavated from urbanized and mountainous areas for construction. Treatments such as chemical immobilization are applied to such excavated rocks for reuse. To design such treatments, determining the potentially leachable arsenic amounts in excavated rocks is imperative. This study aims to understand whether the arsenic releached amount from the excavated rock after once-arsenic leaching should be included in the potentially leachable arsenic amount or estimated using the sequential extraction procedure (SEP). Arsenic was releached at exceeding 0.01 mg L^-1, even from the excavated rock that leached arsenic to less than 0.01 mg L^-1, and this amount corresponded to approximately 12% of that of arsenic leached from the arsenic non-leached rock. The arsenic (re)leached amount corresponded to 84-116% (102 ± 7%) of that of arsenic in the readily soluble fraction using SEP, regardless of whether the arsenic was leached or not. These results indicate that the source of arsenic (re)leached from the excavated rock is arsenic extracted as the readily soluble fraction through SEP, regardless of whether the rock was arsenic-leached or not. This study's findings suggest that the arsenic releached amount from the excavated rock should be considered in the potentially leachable arsenic amount. In addition, the potentially leachable arsenic amount can be relatively and readily estimated by performing SEP.