Mapping airborne lead contamination near a metals smelter in Derbyshire, UK: spatial variation of Pb concentration and 'enrichment factor' for tree bark

Samples or tree bark. collected over an area of 4 km(2) near a small noti-ferrous metals smelter in Derbyshire, UK, were analysed for Pb and Al by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Analyte concentrations varied from 100 to over 25 000 mg kg(-1) and 5 to 1000 mg kg(-1), respectively. While an inverse relationship between the Pb content of bark and distance from the smelter was observed, concentrations fluctuated, indicating a variability in sample collection efficiency and problems in standardization. To overcome these effects, the Pb/Al ratio was calculated and subsequently normalized to the average Pb/Al ratio in continental crust (0.00015), Oil the assumption that the time-averaged concentration of airborne Al in this area is relatively constant and derived principally from wind-blown soil. the measurement represents an anthropogenic 'enrichment factor' ((EF)-E-Pb). (EF)-E-Pb varied from 10 000 to over 1000 000, and showed a consistent reduction with distance front the smelter. lsolines of equal (EF)-E-Pb were subsequently defined on a map of the sampled area. Pb containination was greatest in the Vicinity of the smelter, and preferential transport along the NW-SE axis of the valley (in which the smelter is situated) was observed. The use of enrichment factors thus proved valuable in defining the relative level of airborne-derived Pb pollution.