Transformation of diphenylarsinic acid and related compounds in groundwater: production of thiol-containing arsenicals

Abstract

Environmental context Contamination of groundwater by arsenic compounds used in chemical warfare research is a recently discovered environmental problem in Japan. We report evidence that the arsenic compounds originally present in the groundwater are transforming to thio-arsenic compounds of currently unknown environmental fate. Abstract During routine analyses of groundwater samples contaminated with diphenylarsinic acid (DPAA) at Kamisu, Ibaraki Prefecture, Japan, we obtained data indicating that unknown arsenic compounds accounted for up to 75% of the total arsenic in some of the samples. Results from using liquid chromatography in combination with elemental mass spectrometry and tandem molecular mass spectrometry suggested that two of the main unknown peaks were diphenyldithioarsinic acid and methylphenyldithioarsinic acid. These assignments were later confirmed by comparison with chemically synthesised compounds. A potential transformation scheme for DPAA in the environment is proposed based on the derivatives identified in the environmental samples.