Study on the composition and distribution characteristics of As in As-containing agent contaminated soil

In recent years, China and Japan are cooperating in the destruction of the Japanese army abandoned chemical weapons in China (JACWs). During the long-term burial of JACWs, As-containing agents leaked into the environment due to the corrosion of the shell, resulting in soil As pollution. This paper studied the fraction, speciation, and composition of As in the soil polluted by the As-containing agent in Jilin, China. The results showed that As was mainly distributed in the forest soil in the study area, with the highest concentration of 110 mg/kg, and had the trend of migration to the downhill farmland soil. As mainly accumulated in the amorphous Fe/Al oxides bounded fraction and residual states, the proportion of potentially risky fractions in the soil of downhill farmland is higher than that of uphill farmland. The speciation of As in the soil is mainly As(V), with an average content of 25.02 mg/kg. The transformation behavior of As in the horizontal migration of topsoil is mainly the oxidation of As (III). The residual organic As in soil mainly includes 2-chlorovinylarsonic acid, triphenylarsine, phenylarsine oxide, and diphenylarsonic acid. Similar to the influence factors of As, both speciation and organic compounds of As are significantly affected by Fe/Al/Mn-oxides, and degradation and transformation reactions such as redox occur during migration. •As mainly existed in amorphous Fe/Al oxide bound fraction and residual fraction.•The organic-As in soil mainly includes CVAOA, TPA, PAO, and DPAA.•DPAA showed a significant negative correlation with TP, Ca and Mn.