Abiotic transformation of atrazine in aqueous suspension of four synthetic manganese oxides

Most of the world water systems are contaminated with the herbicide atrazine, and thus its reactivity with soil minerals is an important issue. We have studied the degradation of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) on cryptomelane types I and II, pyrolusite and birnessite in the aqueous phase, using a batch reactor, chromatography, and spectroscopy. The reaction was studied at ambient temperature in the dark and from pH 2.3 to 8.3. The order of reactivity of atrazine on the minerals used was found to be birnessite > cryptomelane II > cryptomelane I ⪢ pyrolusite. Hydroxylatrazine (HA), deethylatrazine (DEA), and deisopropylatrazine (DIA) were found as the primary byproducts under every condition. Five new other minor degradation products (DDA, DEHA, DIHA, ammeline, and cyanuric acid) were also detected. Mn(II) evolution is a minor product. The proposed abiotic pathway for the transformation of atrazine on Mn oxides is identical with the reported biotic pathway. Thus, Mn oxides, common soil components, facilitated the efficient N-dealkylation and hydrolysis of the herbicide atrazine, possibly via a non-oxidative mechanism. N-dealkylation has been attributed strictly to a biological process in soils.