Effects of Dissolved Organic Matter on Uptake and Translocation of Lead in Brassica chinensis and Potential Health Risk of Pb

Dissolved organic matter (DOM) can affect the bioavailability of heavy metals in soil, especially in soils used for vegetable production, where intensive organic fertilization is applied. The present study examined the effects of DOM derived from commercial organic fertilizers (COF), cow manure (COM) and chicken manure (CHM), on uptake and translocation of lead (Pb) in Brassica chinensis in a pot experiment. The results indicate that DOM derived from CHM (DOM(CHM)) significantly increased Pb concentrations in roots of B. chinensis (p < 0.05). By contrast, there was no significant increase in shoot Pb concentration for all the DOM treatments except the high DOM(CHM) treatment in the soil with 800 mg·kg(−1) Pb. Consistent with the Pb concentrations in shoots, translocation factor of Pb from soil to shoot and specific lead uptake (SLU) by B. chinensis were significantly increased for the high DOM(CHM) treatment in the high Pb soil, but not for other DOM treatments. Based on the results of this study, the application of DOM to the soil with 800 mg·kg(−1) Pb could result in an increase in total Pb annually ingested by the inhabitants of Nanjing City in the range of 2018–9640 kg, with the highest estimates resulting from the high DOM(CHM) treatment. This study suggests the risk may rise under some conditions as indicated in the high DOM(CHM) treatment and high Pb pollution level.