Influence of agricultural practices and environmental conditions on pharmaceuticals in recharge waters

In water-stressed regions, Managed Aquifer Recharge (MAR) is essential for water conservation, helping to sustain groundwater resources and increase resilience to drought. MAR typically involves using surface water, treated wastewater, stormwater, and runoff to address groundwater depletion. Since pharmaceuticals are commonly found in wastewater, stormwater, and treated effluent, it is crucial to understand their behavior in aquifers to prevent the unintended contamination of drinking water. This paper explores the transport dynamics of pharmaceutically active compounds (PhACs) under different environmental conditions commonly encountered in MAR systems using surface water and stormwater near agricultural fields, commonly known as Ag-MAR. The PhACs were chosen for their prevalence, toxicity, and ecological behavior, particularly in regions with varying agricultural parameters like pH, nitrate (NO₃^-) and zinc (Zn²⁺). Through laboratory experiments simulating typical Ag-MAR conditions, we examined how various parameters influence PhAC mobility, sorption, and degradation. Our results show that pH plays a significant role in PhAC transport, with acidic conditions (pH 4) generally enhancing retention, while neutral or alkaline soils (pH 6) increase mobility and the risk of groundwater contamination. Zn²⁺ and NO₃^- were found to further alter transport dynamics, with Zn²⁺ enhancing mobility through changes in soil adsorption and complexation, and NO₃^- influencing microbial degradation. Caffeine and ibuprofen exhibited higher mobility at neutral pH, while carbamazepine and diclofenac showed more complex behavior, depending on pH and the presence of Zn²⁺ and NO₃^-. The findings underscore the need for careful management of MAR systems in agricultural areas, taking into account the combined effects of pH fluctuations, heavy metal contamination, and nitrate presence to mitigate pharmaceutical pollution and ensure sustainable groundwater recharge.