Importance and Difficulties of Research on Metal Speciation in the Aquatic Ecosystem: an Ecologist's Viewpoint

Abstract

Post-war research on the role of heavy metals in the environment was stimulated by a new sensitivity towards nature, the increasing impact of human activities on the environment, continuous progress in analytical chemistry and the development of radioecology. Nowadays, very low concentrations of total metal can be quantified in the various compartments of the ecosystem (e.g. water, sediment, suspended particles, plants and animals), and the physical and chemical forms of the metal identified. A current difficulty is how to evaluate the role of the various metal forms in the natural ecosystem. The major issues to be tackled are: variations over time of metal species in relation to the influence of environmental variables; the fact that the availability of the metal varies with the plant and animal species; the ability of the organism to select the metals and their forms; the influence of suspended particles and chelating substances on metal uptake, detoxification strategies and synergic and antagonistic effects. The advantages and disadvantages of monitoring using bioaccumulator organisms are discussed.

The trend from 1934 to 2001 of metal concentrations in bivalve shells (Unio pictorum) from two small lakes: Lake Levico and Lake Caldonazzo (Trento Province, Northern Italy)

“…The probable causes influencing this relationship have been discussed in other papers (e.g. Ravera et al 2003;Ravera 2004).…”

“…In our opinion, a better relationship should result if the metal concentration in the mussel is related to the concentration of the available forms of the metal in the water, and not to the total metal concentration (e.g. Zamuda & Sunda 1982;Ravera 2004). Unfortunately this information is lacking.…”

Nanotechnologies in Food and Agriculture

“…For example, in freshwater, calcium, magnesium, and carbonate ions are the most abundant, but sodium, potassium, phosphorus, iron, sulfur, and silicon compounds are also present. There are also non-conserved components, which include dissolved O 2 , CO 2 , and N 2 gases; nutrients such as phosphate and nitrate; dissolved organic compounds such as amino acids and humic substances; trace elements such as copper, zinc, chromium, molybdenum, vanadium, manganese, tin, iron, nickel, cobalt, and selenium; and particulate materials such as sand, clay, colloid, nonliving tissues, and excreta (Rang et al 1995;Ravera 2004).…”

A toxicidade em ambientes aquáticos: discussão e métodos de avaliação

“…Além de componentes conservativos, as águas também são constituídas por componentes não conservativos, os quais incluem: gases dissolvidos como O 2 , CO 2 e N 2 ; nutrientes como fosfato e nitrato; compostos orgânicos dissolvidos como aminoácidos e substâncias húmicas; elementos traços como cobre, zinco, cromo, molibdênio, vanádio, manganês, estanho, ferro, níquel, cobalto e selênio e, materiais particulados como areia, argila, colóides, tecidos não vivos e excretos. 14,17 Oxigênio e dióxido de carbono são os dois gases mais abundantes nas águas doces e marinhas. O oxigênio é importante porque atua como regulador em processos metabólicos dos organismos e comunidades.…”