Special Issue "Pharmaceutic Compounds, as Emerging Organic Contaminants, and Their Occurrence and Transport in Groundwater: Sources, Reactions and Fate"

Emerging Organic Contaminants (EOCs), also presently named Contaminants of Emerging Concern, constitute an issue of major interest from a management perspective as they have recently shown up on the environmental scene without warning. From a scientific point of view, their occurrence in groundwater has not yet been considered to the necessary detail to build up a conceptual body of knowledge that allows researchers and stakeholders make appropriate decisions about the risks they represent to human and environmental health. Among them, pharmaceutic compounds (PhCs), including antibiotics, are a hazard due to their occurrence in groundwater, as well as for their effects on the subsurface microbial resistome.

Despite wastewater treatment efforts to eliminate PhCs, they are increasingly common in surface water and, consequently, they reach the subsurface through recharge. Moreover, veterinary products also reach soils and aquifers through manure and slurry fertilization. Both processes are responsible for a broad input of these products to the subsurface, causing an immediate threat to groundwater resources quality status.

Nevertheless, PhC fate within the aquifers have seldom been traced at the field scale. However, measuring them at very low concentrations is presently feasible, understanding the mechanisms and processes that govern their transport is still a challenge. Laboratory experiments devoted to define their sorption and degradation parameters offer a wide range of values for the same compound under distinct environmental settings. Field hydrogeological heterogeneity, as usual, hinders the monitoring of their migration through the soil layer and, finally, within the aquifer. Up to the present, very little research has been published describing PhC fates in groundwater, so there is no broad range of study cases to be used as references. Moreover, additional work is needed to integrate the physico-chemical behaviors of PhCs complex molecular structure into transport models that can truly be used to model their migration in groundwater.

In this Special Issue, we look forward editing a group of significant papers that provide a rigorous insight to the stated problems: the regional occurrence of PhCs in groundwater, the characterization of the PhCs input sources and their effects, the details on the transport processes and, especially, on their physico-chemical behavior concerning sorption and degradation parameters and mechanisms that would eventually allow simulating their fate in the subsurface. Finally, papers dealing on how to efficiently characterize the groundwater chemical status associated to these emerging pollutants at a regional level will contribute to translate hydrogeological knowledge to stakeholders and managers. Contributions that provide a comprehensive, integrated perspective of many of the mentioned issues are especially welcome.

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