The chemistries and environmental fates of trace metals and organochlorines in aquatic ecosystems

Abstract

Fundamental physico-chemical properties of trace metals and organochlorines are important in defining their toxicities, cycling and fates in aquatic ecosystems. A broad overview is presented of the chemistries and bioaccumulation of trace metals and organochlorines in aquatic environments, illustrating this concept. The importance of the free ion is emphasized in defining the accumulation and toxicological effects of certain trace metals. However, the uptake of some elements may depend on factors other than the presence of the free metal ion, including the existence of alkylated species or of other particular chemical forms. It is suggested that a variety of mechanisms have evolved to deal with the potential impacts of trace elements and that the organism itself is thus of great importance in defining metal uptake and excretion. By contrast, organochlorines are accumulated by biota in simple response to physico-chemical processes, and organism physiology is generally unimportant in this. The partitioning of organochlorines into lipids is considered to be the most important uptake mechanism, and to underlie most of the observed impacts of extraneous factors on the bioaccumulation of organochlorines. The importance of highly refractory organic contaminants is emphasized, particularly through reference to the non- ortho coplanar polychlorinated biphenyls (PCBs). The need is highlighted for further studies of environmental media to ascertain temporal fluctuations in the levels of non- ortho coplanar PCBs. Fundamental research into chemical analytical techniques is also noted to be required, such that the numbers and range of trace contaminants which are identified in aquatic monitoring programmes may be extended.