Degradation of seven pesticides and two metabolites before and during aquifer storage transfer and recovery operation

• Published in: Journal of contaminant hydrology 2022-12, Vol.251, p.104094, Article 104094
• Main Authors: Kruisdijk, Emiel, Stuyfzand, Pieter J., van Breukelen, Boris M.
• Format: Article
• Language: English
• Subjects: Biodegradation; Fresh Water; Groundwater; Herbicides; Managed aquifer recharge; Natural attenuation; Pesticides; Pesticides - analysis; Water; Water Pollutants, Chemical - analysis
• ISSN: 0169-7722; 1873-6009
• DOI: 10.1016/j.jconhyd.2022.104094

Degradation of 7 common pesticides (bentazon, boscalid, chloridazon, fluopyram, flutolanil, imidacloprid, and methoxyfenozide) and 2 metabolites of chloridazon (desphenyl-chloridazon, and methyl-desphenyl-chloridazon) was studied in an anoxic and brackish sandy aquifer before and during Aquifer Storage Transfer and Recovery (ASTR) operation. Fresh tile drainage water was injected and stored for later re-use as irrigation water. We hypothesized that electron acceptors (O2, NO3), dissolved organic carbon (∼24.7 mg/L), nutrients (NO3: ∼14.1 mg/L, NH4: ∼0.13 mg/L, PO4: ∼5.2 mg/L), and biodegrading bacteria in tile drainage water could stimulate degradation of the pesticides and metabolites (ranging between 0.013 and 10.8 μg/L) introduced in the aquifer. Pesticide degradation was studied at 6 depths in the aquifer using push-pull tests lasting ±18 days before the onset of ASTR operation. Degradation was too limited to quantify and/or could not be assessed because of the potential occurrence of pesticide retardation. Utilizing push-pull tests to obtain degradation constants should only be considered in future studies for non-retarding pesticides with relative low half-lives (here