Quaternary alkylammonium disinfectant concentrations in soils rise exponentially after long-term wastewater irrigation
Benjamin Justus Heyde, Anja Anders, Christina Siebe, Jan Siemens, Ines Mulder
Abstract
Abstract Quaternary alkylammonium compounds (QAACs) are used as disinfectants and surfactants worldwide, with their usage currently increasing as a result of the COVID-19 pandemic. QAACs are released into the environment with manure, sewage sludge and wastewater. The fate of QAACs in soils is poorly understood, although QAACs are inflicted in the selection of antibiotic-resistant bacteria. We studied the temporal accumulation of QAACs in soils of the Mezquital Valley that have been irrigated with Mexico City wastewater from 0 to 88 years. Concentrations of 16 QAACs, including alkyltrimethylammonium compounds (ATMACs), dialkyldimethylammonium compounds (DADMACs) and benzylalkyldimethylethylammonium compounds (BACs), were determined using HPLC-MS/MS after ultrasonic extraction. The most abundant QAAC-homologues in the soils were BACs > ATMACs > DADMACs. The concentrations of QAACs increased linearly and slowly during the first years of irrigation (∑QAAC: 2–23 µ g kg −1 ), but after 40 years of wastewater irrigation we observed an exponential increase in QAAC concentrations (up to 155 µ g kg −1 ). QAACs accumulate in soils of the Mezquital Valley during long-term wastewater irrigation. In contrast to pharmaceuticals, no apparent ‘steady state’ concentration is reached after decades of wastewater irrigation.