Atmospheric dispersion and physicochemical behaviour of Cd and Pb in rainwater after emission by a lead works

Here we report the atmospheric dispersion and physicochemical behaviour of Cd and Pb after emission from the lead works at Stolberg-Binsfeldhammer, Germany. Measurements of wet deposition were made with rain samplers between Stolberg and the town of Jülich to the north-east during the period August 1991–May 1992. Analysis of rainwater after filtration in the rain sampler comprised heavy metal concentrations in the residue as well as heavy metal in the filtrate. Conclusions were drawn from the regional distribution of deposition data and statistical factor analysis. Experimental results on deposition show that in the case of Pb, wet deposition by particulate matter prevails for the emittent at Stolberg-Binsfeldhammer as far as the station at Stolberg-Werth. In the case of Cd, deposition of Cd dissolved in rainwater dominates. Cadmium and Pb compounds analyzed have total concentrations in the rain sampler which are smaller than their respective solubilities. It is concluded that in the stationary state, Cd and Pb must have an insoluble status on the particulate matter. In the case of Pb, elemental Pb could also be responsible for the relatively large amount of Pb adsorbed on solid particles. From the relative contribution of metal deposition on particulate matter and in filtered rainwater in the vicinity of the emitter, there were higher dispersion rates of the particulate matter studied in comparison with the heavy metal species in filtered rainwater. Statistical factor analysis of Cd and Pb wet deposition in the region investigated revealed the ranking of the influencing factors as: particulate matter dispersion and scavenging, rainfall conditions, dispersion of heavy metals dissolved in rainwater as well as emission of heavy metals. Factor analysis of metal concentrations in the residue and proton concentration in the filtrate showed the course of the metal dissolution process throughout dispersion.