Use of lead-210 as a novel tracer for lead (Pb) sources in plants

Lead (Pb) released from anthropogenic sources and stored in environmental repositories can be a potential source for secondary pollution. Here we develop a novel approach for tracking Pb from atmospheric deposition and other sources in the environment using fallout Pb-210 as a tracer, and apply the method to samples collected from Richmond Park, London, the UK. The mean ratio of Pb-210 to total Pb in atmospheric depositions collected from a site adjacent to the park during August-October 2012 was 96 Bq mg(-1), while the ratio in surface soils from the park was typically an order of magnitude lower. The difference between these values made it possible to trace the source of Pb in the plants. The Pb-210/Pb ratios in plants varied from 0 to 34 Bq mg(-1) indicating different levels of Pb absorption from the atmosphere. The ratio in mosses had an average value of 22 Bq mg(-1). This suggests that only around 20% of the Pb they contain was from direct atmospheric deposition, revealing possible limitations in the use of terrestrial mosses for monitoring atmospheric pollution. As well as tracking sources, variations in the Pb-210/Pb ratio can also reveal ways in which Pb is transferred within plants.