Elevated temperature on leaching of arsenic and boron from excavated rocks

Abstract

This work evaluated the leaching behaviors of geogenic arsenic and boron of two excavated rocks under different temperatures. Excavated rocks with geogenic contamination are expected to be used in embankments with proper countermeasures. Their leaching behaviors might change because of seasonal and daily changes in ground temperature. However, the effect of temperature on leaching behaviors has not been well examined. Column tests at temperatures of 20 and 40°C were performed using rock samples. Elevated temperatures led to the release of greater amounts of arsenic and boron. The largest arsenic concentrations obtained from the column tests were 0.53 mg/L at 40°C, while at 20°C was 0.15 mg/L for one rock sample. The largest concentrations of arsenic and boron obtained at 40°C were at most 3.5 times larger than at 20°C. Boron concentrations decreased as electric conductivity decreased. Electric conductivity can be one index to predict the leaching behavior of boron.