Abstract:

As a common environmental pollutant, accurate determination of the bioavailability of arsenic is essential for assessing potential health risks. In order to evaluate the environmental quality of agricultural soils more rationally, this paper explores a reliable and efficient method to extract bioavailable arsenic （the sum of the water-soluble, weakly acid-extractable, reducible, and oxidizable fractions of arsenic）  from soil. Based on the property that L-cysteine solution can effectively form chelates with arsenic, L-cysteine solution was selected as the extractant, and optimized around the parameters of mass fraction of extractant, extraction temperature, and ultrasonic time, etc. The mass concentration of arsenic in the soil in the effective state was determined under the conditions of different extraction temperatures and different mass concentrations of the extractant, respectively, and compared with the results of the sequential extraction to determine the optimal extraction conditions. The results showed that when the mass concentration of L-cysteine was 10 g/L, the ultrasonication temperature was 40 ℃, and the ultrasonication time was 30 min, the bioavailable  arsenic extracted of  DT-1 sample was 7.37 μg/g, closely matched the results of bioavailable arsenic obtained by sequential extraction （7.83 μg/g）.  Compared with the sequential extraction method, this method requires only one step of extraction and the extraction time is shortened by 65 h, which greatly improves the efficiency.

Key words: arsenic, bioavailability, L-cysteine, risk evaluation, soil, environmental quality； sequential extraction method