A study on temporal trends and estimates of fate of Bisphenol A in agricultural soils after sewage sludge amendment

Abstract

Temporal concentration trends of BPA in soils were investigated following sewage sludge application to pasture (study 1: short term sludge application; study 2: long term multiple applications over 13years). The background levels of BPA in control soils were similar, ranging between 0.67–10.57ngg−1 (mean: 3.02ngg−1) and 0.51–6.58ngg−1 (mean: 3.22ngg−1) for studies 1 and 2, respectively. Concentrations in both treated and control plots increased over the earlier sampling times of the study to a maximum and then decreased over later sampling times, suggesting other sources of BPA to both the treated and control soils over the study period. In study 1 there was a significant treatment effect of sludge application in the autumn (p=0.002) although no significant difference was observed between treatment and control soils in the spring. In study 2 treated soils contained considerably higher BPA concentrations than controls ranging between 12.89–167.9ngg−1 (mean: 63.15ngg−1). This and earlier studies indicate the long-term accumulation of multiple contaminants by multiple sewage sludge applications over a prolonged period although the effects of the presence of such contaminant mixtures have not yet been elucidated. Fugacity modelling was undertaken to estimate partitioning of Bisphenol A (soil plus sewage: pore water: soil air partitioning) and potential uptake into a range of food crops. While Bisphenol A sorbs strongly to the sewage-amended soil, 4% by mass was predicted to enter soil pore water resulting in significant uptake by crops particularly leafy vegetables (3.12–75.5ngg−1), but also for root crops (1.28–31.0ngg−1) with much lower uptake into cereal grains (0.62–15.0ngg−1). This work forms part of a larger programme of research aimed at assessing the risks associated with the long-term application of sewage sludge to agricultural soils.