Insight into Distributions of Pharmaceuticals in Soil-Water-Radish Systems.

Pharmaceuticals present in soils originated from irrigation with recycled water or land application of biosolids can enter agricultural crop products. In this study, environmental fate, distributions and accumulation of fifteen commonly-used pharmaceuticals were investigated in soil-water-radish systems in greenhouse. The distribution of pharmaceuticals between soil and pore water as well as their degradation collectively governed the bioavailability of pharmaceuticals to plant uptake. Fourteen out of the 15 pharmaceuticals could accumulate in the radish tissues with varying concentrations ranging from 2.1-14080 ng/g. The comparison of bioconcentration factors (BCFs) of radish on the basis of bulk soil vs. the soil pore water suggests that the former type of BCFs (based on bulk soil concentration) are not appropriate to estimate the accumulation capacity in plants. Instead, the pharmaceuticals present in soil pore water are the major bioavailable fraction, and better to evaluate their accumulation in radish. The radish root-pore water BCF was found to exhibit a positive relationship with pH-adjusted log K_ow for the neutral pharmaceuticals, suggesting that hydrophobic partitioning could be a primary factor for accumulating neutral pharmaceuticals in roots. However, for ionic pharmaceuticals, electrostatic interactions and “ion-trap” effect could influence their accumulation and translocation process. The results from this study provide useful information to evaluate the potential risks on food safety relevant to using biosolids as soil amendment and/or reclaimed water in agricultural irrigation.