Development of heavy-metal deposition by precipitation in West Germany .1. Lead and cadmium

Between 1984 and 1993 and deposition of Pb and Cd with bulk precipitation was measured on 25 open field sites in 4 German federal states. The absolute amount of Pb and Cd deposition varies according to field sites and annual precipitation. In all studied areas, however, Pb deposition via bulk precipitation decreased significantly during the observation period. Considering all research areas under study, the average Pb deposition with bulk precipitation fell from 142 g ha(-1) in 1984 to 31 g ha(-1) in 1993 (r = -0.934***). This decrease in Pb deposition correlates with the prognosticated decline in Pb emissions that occurred in Germany during the same time period owing to the introduction of unleaded motor fuels in 1984. Average Cd deposition on all research stations fell from 3.4 g ha(-1) in 1984 to 2.0 g ha(-1) in 1993 (r = -0.900***). However, in contrast to Pb, the reduction of Cd deposition was significantly only at 11 of 25 research stations. The reduction in Cd deposition with precipitation is substantially lower than the reduction in Cd emissions prognosticated.