Chromium and arsenic in contaminated soils (Review of publications)

In the last decades, the chromium clarke in the world’s soils has been revised and reduced; at present, it is equal to 70 mg/kg. No maximal permissible concentration is accepted for the total chromium content in the soils of Russia; it appears reasonable to use the Western European and North American standards in Russia and to take the average value of the maximal permissible concentration equal to 200 mg Cr/kg. Chromium toxicity depends on its oxidizing status. The hazardous effect decreases with the reduction of Cr(VI) to Cr(III). There are various chemical reducers of Cr(VI), including sulfides, dissolved organic substance, aqueous Fe(II) and minerals enriched in Fe(II), and Fe(0). As-containing ore tailings represent a powerful source of technogenic arsenic. Significant environment contamination with natural As is registered in a number of Asian countries. The maximal permissible concentration of total arsenic is equal to 2 mg/kg in Russian soils; it is probably underestimated, because it is lower than the As clarke in soil (5 mg/kg). The approximately permissible concentration (APC) values for As look more reasonable. Arsenic toxicity depends on its oxidation degree: As(III) is 2–3 times more toxic than As(V).