Biogeochemical cycling, speciation and transformation pathways of arsenic in aquatic environments with the emphasis on algae

Abstract

Geogenic arsenic (As) contamination is an emerging issue worldwide as > 200 million people are at the stake of As toxicity. Arsenic exists in organic and inorganic forms while inorganic forms are more toxic and dominated in nature. Biogeochemical cycling of As in the aquatic environment depends on pH, redox potential, microbes and in particular algae, as well as its interaction with different elements (e.g. iron and sulphur). Dissolved organic carbon, oxides of iron and manganese and sulphur species play a significant role in As release and speciation in water systems. This chapter gives a brief overview of source and distribution of As, describes role of As species including the thiolated As forms in aqueous systems. We also address the key functions of microorganisms with a particular emphasis on algae and its effects on As speciation, as algae plays a vital role in the biogeochemical cycling of As in aquatic environments, albeit these aspects are partially studied and explored.