THE TRANSPORT OF AIRBORNE TRACE-ELEMENTS COPPER, LEAD, CADMIUM, ZINC AND MANGANESE FROM A CITY INTO RURAL-AREAS

The fluxes of the elements lead, zinc, copper, cadmium and manganese have been measured in the insoluble component of bulk deposition derived from Christchurch city, New Zealand. Lead, zinc, copper and cadmium fluxes follow approximately exponential decay curves away from the city whereas manganese deposition showed little spatial variation. A similar composite source originating in the city is indicated for the lead, zinc, copper and cadmium and a different major source occurs for manganese. In the city and nearby rural areas soil is not a major source of atmospheric lead, zinc, copper and cadmium, whereas at remote sites atmospheric levels of these elements are mostly soil derived. Seasonal variations in the bulk deposition are large within the city, and at upwind rural sites. The variations are controlled by meteorological conditions, in particular wind speed and the height of the mixing layer. Compared with overseas studies, the proportion of the metals occurring in the soluble fraction of the bulk deposition is low. This may be due to the relatively dry climate of the area.