Physicochemical Water Parameters Affecting Cadmium, Lead and Mercury Speciation, Bioavailability and Toxicity in the Aquatic Environment

Physicochemical water parameters like pH, salinity, dissolved oxygen, temperature, and dissolved organic carbon, significantly influence the dynamics of toxic elements, such as cadmium (Cd), lead (Pb), and mercury (Hg) in the aquatic environment. Such factors can direct element speciation, favoring or not the formation of more or less toxic species. In addition, bioavailability may also be affected. Environmental conditions favor the release of elements from the sediment or reduce their complexation with ligands, contributing to higher bioavailability. After being absorbed by aquatic biota, Cd, Hg and Pb cause serious health damage to both animals and humans who consume them. Affected systems include the nervous, respiratory, reproductive, and immune systems. In this context, this chapter will address the main abiotic variables responsible for affecting the behavior of Cd, Hg, and Pb, exploring their chemical forms in different aquatic environments, contaminating sources, the main physicochemical parameters that influence speciation, toxicity, and bioavailability, as well as toxic effects on aquatic biota and human health.