Fate of pharmaceuticals in soil after application of STPs products: Influence of physicochemical properties and modelling approach

- Effluent and biosolids are reused in agriculture for irrigation and fertilisation.
- Pharmaceuticals are present in different concentrations in effluents and biosolids.
- The fate of seven pharmaceuticals is evaluated in these scenarios by two models.
- The hazard index obtained differed one order of magnitude depending on the model.

Depurated effluents can be employed as reclaimed water for irrigation in regions with low precipitations, while nutrients-rich biosolids are usually applied as fertilizer for agricultural purposes. However, both practices may result in the accumulation of micropollutants in the soil compartment, the contamination of groundwater, and/or their biotransfer to different living organisms until they finally may reach human receptors. The fate and transport of seven pharmaceutical and personal care products (PPCPs) with different physicochemical properties was analysed for these scenarios employing two different models: the buckets model and the HYDRUS-1D software package. The results indicated that these compounds have a low potential to contaminate groundwater in the type of soil under study (silty loam), although triclosan tended to accumulate in the top layers of the soil. Similar conclusions were reached through both models, although they predicted different solute plant uptake and accumulation patterns of the evaluated compounds. Therefore, the buckets model can be considered as an adequate option to perform a screening level assessment of these compounds. However, HYDRUS-1D could provide more information on the fate of pharmaceuticals in soil, thus contributing to reduce the uncertainty already associated to PPCPs. Additionally, the significant difference of the Hazard Index (HI) obtained from a human health risk assessment performed using the estimated soil concentrations from both models also contributed to recommend the use of a model that considers all the relevant mechanisms of mass transfer to reduce overestimation of risk.