University of Duisburg-Essen , Instrumental Analytical Chemistry, Universitätsstr. 5, D-45141 Essen, Germany.
Environ Sci Technol. 2015 Feb 3;49(3):1673-80. doi: 10.1021/es503496u. Epub 2015 Jan 13.
Atrazine, propazine, and terbuthylazine are chlorotriazine herbicides that have been frequently used in agriculture and thus are potential drinking water contaminants. Hydroxyl radicals produced by advanced oxidation processes can degrade these persistent compounds. These herbicides are also very reactive with sulfate radicals (2.2-3.5 × 10(9) M(-1) s(-1)). However, the dealkylated products of chlorotriazine pesticides are less reactive toward sulfate radicals (e.g., desethyl-desisopropyl-atrazine (DEDIA; 1.5 × 10(8) M(-1) s(-1))). The high reactivity of the herbicides is largely due to the ethyl or isopropyl group. For example, desisopropyl-atrazine (DIA) reacts quickly (k = 2 × 10(9) M(-1) s(-1)), whereas desethyl-atrazine (DEA) reacts more slowly (k = 9.6 × 10(8) M(-1) s(-1)). The tert-butyl group does not have a strong effect on reaction rate, as shown by the similar second order reaction rates between desethyl-terbuthylazine (DET; k = 3.6 × 10(8) M(-1) s(-1)) and DEDIA. Sulfate radicals degrade a significant proportion of atrazine (63%) via dealkylation, in which deethylation significantly dominates over deisopropylation (10:1). Sulfate and hydroxyl radicals react at an equally fast rate with atrazine (k (hydroxyl radical + atrazine) = 3 × 10(9) M(-1) s(-1)). However, sulfate and hydroxyl radicals differ considerably in their reaction rates with humic acids (k (sulfate radical + humic acids) = 6.8 × 10(3) L mgC(-1) s(-1) (mgC = mg carbon); k (hydroxyl radical + humic acids) = 1.4 × 10(4) L mgC(-1) s(-1)). Thus, in the presence of humic acids, atrazine is degraded more efficiently by sulfate radicals than by hydroxyl radicals.
莠去津、扑灭津和特丁津是氯三嗪类除草剂，曾广泛用于农业，因此可能是饮用水的污染物。高级氧化过程中产生的羟基自由基可以降解这些持久性化合物。这些除草剂还与硫酸根自由基（2.2-3.5×10(9)M(-1)s(-1)）非常反应。然而，氯三嗪类农药的脱烷基化产物对硫酸根自由基的反应性较低（例如，去乙基-去异丙基莠去津（DEDIA；1.5×10(8)M(-1)s(-1)））。除草剂的高反应性主要归因于乙基或异丙基。例如，去异丙基莠去津（DIA）反应迅速（k=2×10(9)M(-1)s(-1)），而去乙基莠去津（DEA）反应较慢（k=9.6×10(8)M(-1)s(-1)）。叔丁基对反应速率没有强烈影响，如去乙基特丁津（DET；k=3.6×10(8)M(-1)s(-1)）和 DEDIA 之间相似的二级反应速率所示。硫酸根自由基通过脱烷基化降解莠去津的很大一部分（63%），其中去乙基化明显占主导地位，而去异丙基化则占次要地位（10:1）。硫酸根和羟基自由基与莠去津的反应速率相同快（k（羟基自由基+莠去津）=3×10(9)M(-1)s(-1））。然而，硫酸根和羟基自由基在与腐殖酸的反应速率上有很大的不同（k（硫酸根自由基+腐殖酸）=6.8×10(3)LmgC(-1)s(-1)（mgC=mg 碳）；k（羟基自由基+腐殖酸）=1.4×10(4)LmgC(-1)s(-1））。因此，在腐殖酸存在下，莠去津更有效地被硫酸根自由基降解，而不是被羟基自由基降解。
