Lead isotope ratios in a soil from a coal carbonization plant

Abstract

In the present work, lead isotope ratios were used to ascertain the enhancement of lead concentration in a soil derived from an experimental coking plant that processed 30 tons of coal per day over a period of 30 years. Isotope ratios were also used in this work to evaluate whether lead originated by this industrial activity may be leached and transported deep into the soil. It was found that variation in Pb concentrations in soil samples from the A Horizon, at various distances (7–35 m) from the coking battery, ranged between 17 and 349 μg g −1, whereas in samples taken 50 m away, the concentration was less than 34 μg g −1. This implies that all the operations involved in coal carbonization are responsible for the increase in the total amount of Pb in the thin top layer of the soil, although the concentration of lead was lower than the intervention limit values established for contaminated soils by Dutch Standards (530 μg g −1). To establish the origin of pollution in this soil, lead isotope ratios of samples taken at different points were determined. The relationships between 206Pb/ 204Pb and 207Pb/ 204Pb indicated a mixture of natural and anthropogenic Pb. Although lead from industrial activity is present in the thin top layer, its presence decreased drastically between 0 and 30 cm depth.