Introduction

This chapter focuses on the role excess water and soil oxidation–reduction processes play in elemental cycling, heavy metal transformation, wetland plant response, and toxic organic transformation. Wetlands are unique ecosystems located in areas with comparatively low elevation and a high water table. Wetlands can include marshes, swamps, bogs, and similar areas that are poorly drained and retain water during rainy periods. Globally, wetlands can be found in all climates, from tropical to tundra, with the exception of Antarctica. The value and function of wetlands are well recognized, as evidenced by national and international policies to preserve wetland ecosystems. In landscapes, wetlands typically occur between upland and aquatic ecosystems. In the 1990s and through today, we have seen the emergence of wetland and aquatic systems biogeochemistry as a proper scientific discipline complete with dedicated journals, textbooks, and scientists willing to label themselves as biogeochemists.