Chemical Speciation of Chromium and Arsenic and Biogeochemical Cycle in the Aquatic System

The rapid growth of industrialization and urbanization has increased the risk of water pollution worldwide. In the current scenario the water pollution due to the heavy metals reached to the alarming stage. The non-biodegradable nature of heavy metals and their easy bioaccumulation on the body of the living organism causes chronic health issues in human beings as well as animals. Arsenic (As) and chromium (Cr) are the most toxic heavy metal ions, which are readily present in the aquatic system. The toxicity of the arsenic and chromium depends upon the speciation of these metal ions in the aquatic system. Chromium mainly exists in aqueous system as Cr(III) and Cr(VI), among which Cr(VI) is in highly noxious oxidation state and Cr(III) is required in trace amount for the biological function. Arsenic exists in four oxidation states, i.e. −3, 0, 3, and 5, while As(III) and As(V) are in the common oxidation state in aqueous system. As(III) is in a highly dangerous oxidation state of arsenic than As(V). In this chapter discussion has been carried out on the speciation of chromium and arsenic in aqueous system. In addition to this, the overview of the biogeochemical cycle of these metals ions is also provided.