Behavior and Fate of PPCP/EDCs in Soil-Plant Systems

Reusing treated wastewater for agricultural irrigation and biosolids for soil amendment introduces pharmaceutical and personal care products (PPCPs) and endocrine disrupting chemicals (EDCs) into the soil environment, creating the potential for plant uptake and subsequent human exposure by ingestion. We first evaluated the persistence and transformation of bisphenol A, diclofenac, naproxen, and 4-nonylphenol in soils, using 14C-labeling. The half-lives of the parent compounds were short, ranging from only 1.4 to 5.4 d. Mineralization and formation of bound residue substantially contributed to dissipation. In addition, many transformation products were detected in soil extracts, suggesting the need to consider the behavior and biological activity of degradation intermediates in soils. In a subsequent study, we measured the accumulation of 14C-labeled bisphenol A, diclofenac, naproxen, and 4-nonylphenol in a hydroponic system growing lettuce and collards as model plants. In both plant species, accumulation followed the order of bisphenol A > nonylphenol > diclofenac > naproxen and accumulation in roots was much greater than in leaves or stems. However, over 99% of the accumulated compounds were non-extractable, suggesting that these chemicals or their transformation products were bound to the plant matrix. PPCP/EDCs were also extensively transformed in the nutrient solution. In the third study, we systematically evaluated the effect of transpiration on plant accumulation of 16 commonly detected PPCP/EDCs, by analyzing extractable parent compounds in plant tissue. Transpiration by lettuce, tomato, and carrot plants was shown to positively correlate with the removal of PPCP/EDCs from the nutrient solution and the bioconcentration and translocation of neutral PPCP/EDCs. The accumulation of anionic and cationic compounds into leaf tissue was positively correlated with transpiration. However, root accumulation of anionic compounds was attributed to ion trapping, while root accumulation of cationic compounds was likely related to electrical attraction to cell membranes. Our research findings suggest that PPCP/EDCs from treated wastewater or biosolids applications are unlikely to accumulate in food crops to biologically significant levels. Rapid degradation in soil and extensive metabolism in plant tissues, when coupled with generally low concentrations in the reuse materials, contribute to limited plant accumulation