Occurrence of Pharmaceutically Active Compounds, Parabens, and their Main Metabolites in Soils Amended with Sludge and Compost

Abstract

The presence of pharmaceuticals and personal care products (PPCPs) in the environment has aroused considerable interest in the last few years. However, the occurrence and fate of parent compounds and their metabolites and/or transformation products in soils have been scarcely evaluated to date. In this work, the dissipation kinetics of PPCPs, which are most frequently detected in the environment, and their main metabolites, is evaluated in soil amended with digested and composted sludge. The studied compounds were monitored for 60 days after digested or compost application to the soil. Several kinetic models were used to evaluate the dissipation kinetics of the processes. Parabens and their metabolites were the compounds with the fastest dissipation rates, while the antiepileptic carbamazepine and its metabolites were the poorest degraded compounds studied. Most of the compounds showed a single first-order dissipation kinetics. The application of biphasic kinetic models can improve the knowledge about the dissipation behavior of some of them. For instance, whereas compounds such as carbamazepine showed a high persistence showing a lag phase in its dissipation, resulting in an approximately constant concentration for the first days of batch experiments, others, such as sulfamethoxazole and diclofenac, followed a dissipation kinetics in two phases: a fast dissipation attributed to the amount of compound associated to the soil-water solution and a slow dissipation that could be due to the amount of the compound adsorbed onto the soil particle. For most of the compounds, the dissipation was faster in sludge-amended soil than in soil without organic amendment. This fact could be due to the influence of microbial activity and organic matter on their dissipation.