ABSTRACT
Soils and sediments represent the major sink for heavy metal(loid)s that are released into the biosphere through both geogenic (i.e., weathering or pedogenic) and anthropogenic (i.e., human activities) processes. The mobility and bioavailability of heavy metal(loid)s in soils and sediments are affected by both physicochemical and redox reactions (Figure 3.1) (Alexander 2000; Adriano 2001). Redox reactions play a key role in the behavior and fate of toxic heavy metal(loid)s, especially arsenic (As), chromium (Cr), mercury (Hg), and selenium (Se), in soils and sediments by influencing their speciation (Gadd 2010). For example, As contamination of surface- and groundwater, mediated through redox reactions of geogenic As, became a major human health issue at several points around the globe (Mahimairaja et al. 2005). Thus, a greater understanding of redox reactions will help in monitoring the environmental fate of the heavy metal(loid)s, and will also aid in developing in situ bioremediation technologies that are environmentally compatible. It is unlikely that the natural phenomena (e.g., natural attenuation) are optimal for the removal of toxic heavy metal(loid)s from contaminated sites. Redox reactions can readily be managed and enhanced for the efficient removal of contaminants, provided the biochemistry of these processes is understood. Dynamics of heavy metal(loid) redox transformation in soils and sediments. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315372952/55acbd01-4a7c-4b6c-99dc-d931a043bf8c/content/fig3_1_B.jpg" xmlns:xlink="https://www.w3.org/1999/xlink"/>
