Pharmaceutical compounds (PCs) are introduced to the agro-environment mainly via intensive irrigation with treated wastewater and application of organic fertilizers such as biosolids, manure and compost. PCs are of potential ecotoxicological concern because they are designed to induce specific biochemical effects and/or they are highly adsorbable, resulting in a tendency to accumulate in solid matter such as soil, sediment and plant tissues. Due to their increasing ubiquity, it is essential to understand the fate of PCs in soils and to evaluate the effects of organic amendment on their behavior in the environment. Highly mobile PCs have the potential to leach to the groundwater, whereas strongly sorbing PCs can accumulate in the top layer of soils. In addition, the influx of dissolved organic matter (DOM) originating from reclaimed wastewater and/or from sludge application into the soil can affect the behavior of the PCs.

The objective of this study was to evaluate the effect of biosolids application and different soil solution parameters on the transport behavior of selected PCs in loess soil. The studied PCs were sulfapyridine (SPD), sulfamethoxazole (SMX), carbamazepine (CBZ), naproxen (NAP), diclofenac (DCF) and gemfibrozil (GFB).

Our results show that the addition of biosolids to the soil reduces the mobility of the less polar PCs (i.e., CBZ, DCF and GFB). In addition, the application of secondary treated waste water (STWW) as background solution increased the mobility of PCs classified as weak acids (NAP, DCF and GFB) compared to DOM-free solution. The main factors identified as possible causes to this difference in behavior are solution pH, DOM content and concentration of mono- and divalent cations.