Abstract
A simple method for the detection and semi-quantitative determination of arsenic compounds purgeable by a sweep gas from soil was designed. The results were used to tentatively evaluate the flow of volatile arsenic compounds from the lower reducing to the upper oxidizing zone in arsenic rich soils. About 10 kg of soil, with a total arsenic content of 2980 ± 25 mg kg−1 was purged with nitrogen at a flow rate of 10 ml min−1. The gaseous compounds were trapped in concentrated nitric acid solution, preconcentrated by gentle evaporation at 80°C and the arsenic content was determined by the Hydride Generation Atomic Absorption (HG-AAS) technique. Nitrite interference during detection was overcome by treating the final solution with sulfamic acid for 24 h at the prereduction step. Based on these results it may be reasonably assumed that at 20 ± 1°C from a one hectare area of soil having 15 cm depth in the lower reducing zone an estimated maximum of 1500 mg of arsenic could stream up to the oxidizing zone in one week time due to likely microbial reduction of arsenic. Part of these arsenic coumpounds would enter the atmosphere and the remaining part may get oxidized upon reaching the oxic layer and accumulate there in. The part undergoing oxidation in the oxic layer is suggested to be a factor contributing to the local maximum of arsenic in the 20 cm depth from the surface.
ACKNOWLEDGMENT
Dejene A.Tessema thanks the Austrian Academic Exchange Service (ÖAD) for granting him a scholarship.