Degradation of atrazine and structurally related s-triazine herbicides in soils by ferrous-activated persulfate: Kinetics, mechanisms and soil-types effects

Abstract

The occurrence of s-triazine herbicides in soils and groundwaters has been reported globally and remediation of these contaminated sites are essentially imperative, especially at accidental spill sites. Present work investigated the feasibility of using Fe2+ catalyzed persulfate (PS) to effectively degrade s-triazine herbicides (e.g., atrazine (ATZ), terbuthylazine (TEA) and ametryn (AMT)) in soils. The degradation kinetics, mechanisms and soil-types effects were systematically investigated. For arable soil A1, extent of degradation reached 80% for 100 mg kg−1 ATZ contaminated soil after 600 min (PS/Fe2+ of 16.6 mM/16.6 mM) at 23 °C. Increasing PS and Fe2+ dosages could enhance ATZ degradation. Acidic condition was favorable for the degradation of ATZ with Fe2+/PS process and the contribution of SO4− to the overall degradation of ATZ decreased as initial pH increased. The ethyl group and chloride substituent on molecular structure of ATZ affected its degradation comparing to other two s-triazine herbicides. ATZ degradations in two arable soils and one paddy soil indicated that different soils with various physical-chemical properties, such as soil organic matter, available and total Fe contents, may influence the ATZ degradation. Moreover, a total of five degradation products of ATZ were identified in soil A1 by Fe2+/PS process. Three degradation pathways including alkyl chain oxidation, dealkylation and dechlorination-hydroxylation reactions with the underlying oxidation mechanisms were tentatively proposed.