Effects of Heavy Metals and Metalloids on Soil Organisms

Abstract

At the molecular level metals and metalloids cause organisms to produce chemicals such as metallothioneins to bind metals and reduce their toxicity and/or chemicals such as heat shock proteins that repair any damage done. On a cellular scale metal-rich P and S " granules " are often produced, particularly in cells that line the digestive organs, which concentrate and detoxify the contaminants. Granules either accumulate or are excreted. If metals accumulate, the location of accumula-tion varies between species though is often either in an organ analogous to the liver or at sites which are shed during moulting. Countless studies document effects on weight, reproduction and mortality of organisms. Variation in results are due to a complex combination of contaminant bioavailability, uptake pathways, exposure duration and soil properties. At the field scale metal and metalloid contaminants usually result in either population decline due to toxic effects/loss of prey or population growth due to the removal of predators or competition. Populations of different species are affected in different ways, modifying community structure and ecosystems. Organisms found in contaminated soils in which nave introduced individuals of the same species can not survive exhibit either acclimation/tolerance (reversible changes in physiology) or adaptation/resistance (a change in genetic structure). A large number of toxicity tests exist to investigate and demonstrate the impact of metals and metalloids on organisms. Omic technologies offer great potential to help develop our level of understanding of these effects but are not yet a mature technology. Pollutants may affect organisms at a number of levels. In this chapter effects are discussed at the molecular, physiological, population and ecosystem level. The impact that metals have on evolution of organisms together with methods to determine effects of contaminants in the field, i.e. toxicity tests, are also reviewed. The chapter focuses on soil invertebrates, but soil microbiota are also covered. To have an effect on an organism, a metal must first be available to it. Metal availability is discussed in Chap. 6. Details of specific metal chemistry and behaviour are given in Chap. 3 and Part II of this volume.