Global budget of trace metal sources

Global emission inventories, being the key information for the global budgets of trace metals, have become available only recently. The latest information on emissions and sources of trace metals on a global scale is presented in this paper. As the global assessments are prepared on the basis of estimates of regional emissions, these latter data are also reviewed here. A comparison of the worldwide atmospheric emissions from natural and anthropogenic sources suggests that various human activities are the dominant source of many trace metals, including As, Cd, Pb, and Zn. A comparison of the atmospheric and aquatic emissions indicates that, for most of the trace metals, the annual anthropogenic inputs into water exceed the quantities emitted to the atmosphere. However, the largest quantities of trace metals are discharged to the terrestrial environment. So far, the Pb budget seems to be the most accurate owing to a large body of information available on this element. The largest emissions of Pb were estimated for gasoline combustion, contributing about two thirds of the total emissions to the atmosphere. Emissions from nonferrous metal production contributed about one quarter. Emissions from the European and Asian sources contributed each about one third of the global emissions, followed by emissions from sources in North America. A spatial distribution of the global Pb emissions is presented within a 1 × 1° grid system.