Sulfur

Abstract

Sulfur is an essential element for plants, animals, and bacteria because it is a component of certain amino acids. Sulfur is present in the environment in various forms to include sulfur in organic matter, mineral deposits of sulfate and elemental sulfur, dissolved sulfate in water, atmospheric sulfur, and sulfur in living organisms. Sulfate minerals tend to be soluble and ocean waters have high sulfate concentrations. Sulfate is the form of sulfur used most commonly by plants, although some plants can fix atmospheric sulfur by a method analogous to nitrogen fixation. Bacteria can oxidize and reduce sulfur compounds in the same manner as they do nitrogenous compounds, and oxidations and reductions of sulfur may occur by chemical reactions not involving biological activity. There is a sulfur cycle in nature, and most of the aspects of this cycle operate in an aquatic ecosystem. Sulfate influences biological activity by acting as a nutrient, but sulfide can be toxic to aquatic organisms. The purpose of this chapter is to discuss sulfur chemistry and its influence on water quality.