Introduction on environmental chemistry and global cycles of chromium, nickel, cobalt beryllium, arsenic, cadmium and selenium, and their derivatives†

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Abstract
Crude estimations are a basis for further discussion. Even a trial—which has to be verified—may be sufficiently exact to get a better feeling for sources of risk and for understanding pathways of redistribution, especially in industrial countries. Studies of global cycles may not be too relevant, but give valuable background information and stimuli to recognize more significant local changes and possible effects. It is extrapolated that the emissions of the heavier elements chromium, nickel and cobalt with their short atmospheric life cycle play a more dominant role in waters and soils. On the other side in the cases beryllium, arsenic, antimony, cadmium and selenium atmospheric transports are relatively more important. Biological cycles— extraction by plants from soil—correspond in general to about one‐third of the total emissions, but are relatively more important in the cases of cobalt and cadmium, and less in the case of chromium. Natural weathering of rocks and soils is in the order of one‐sixth of the total emissions for chomium, nickel, cobalt and arsenic, but is relatively smaller for beryllium, cadmium and selenium. Volcanic emissions are globally of very low significance. Regarding anthropogenic sources, emissions of coal burning and of other combustion processes are quite important. They are relatively highest for beryllium (probably more than half of the total emissions). In the cases of nickel, aresenic and selenium these sources may account for about 20%, in the cases of chromium, cobalt and cadmium for about 10%, getting into global cycles. In industry, during ore and metal processing (also of other metals) arsenic, cadmium and selenium enter with about 20% of their input overproportionately into the environment. From the use, the disposal and the incineration an important share of chromium and nickel are emitted into waters. In the cases of arsenic and cadmium air and water emissions are relevant. In the cases of cobalt, beryllium and selenium the emissions from use are globally probably still below 10% of the total input, but careful local monitoring is needed in growth areas of application. Mobilization and transport rates have been heavily accelerated in the last 40 years. Especially consumer goods (batteries, electronics, semi‐conductors, etc.) from critical metals may—through disposal and incineration— contribute to higher regional and local uptake by living organisms.

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