Gan Qiu, Singh Raphael M, Jans Urs
Chemistry Department, the City College of New York, 138th Street and Convent Avenue, New York, New York 10031, USA.
Environ Sci Technol. 2006 Feb 1;40(3):778-83. doi: 10.1021/es051482n.
This work examines the reaction of reduced sulfur species (e.g., bisulfide, thiosulfate, thiophenolate) with naled, a registered insecticide, in well-defined anoxic aqueous solutions at 5 degrees C. High concentrations of reduced sulfur species can occur in the porewater of sediments and in anoxic subregions of estuaries. The dominanttransformation product from the reaction of naled with reduced sulfur species is dichlorvos, which indicates that debromination is the major reaction pathway. Dichlorvos is also a registered insecticide which is more toxic than naled. The second-order rate constants for reaction of naled with bisulfide and thiophenolate at 5 degrees C are 10.2 +/- 0.4 M(-1) s(-1) and 27.3 +/- 0.9 M(-1) s(-1), respectively, while the second-order rate constant for the reaction of naled with hydrogen sulfide and thiophenol are not significantly different from zero. The second-order rate constant of the reaction of naled with thiosulfate at 5 degrees C is 5.0 +/- 0.3 M(-1) s(-1). In contrast, the second-order rate constant of the reaction of dichlorvos with bisulfide at 25 degrees C is (3.3 +/- 0.1) x 10(-3) M(-1) s(-1). The activation parameters of the reaction of naled with bisulfide were also determined from the measured second-order rate constants over a temperature range. The results indicate that reduced sulfur species can play a very important role in the transformation of naled and dichlorvos in the coastal marine environment. It can be expected that in the presence of reduced sulfur species, naled is almost immediately transformed into the more toxic dichlorvos, which has an expected half-life of 4 days to weeks.
本研究考察了在5℃下，在明确的缺氧水溶液中，还原态硫物种（如硫氢根、硫代硫酸根、苯硫酚盐）与已注册杀虫剂二溴磷的反应。沉积物孔隙水和河口缺氧亚区域中可能存在高浓度的还原态硫物种。二溴磷与还原态硫物种反应的主要转化产物是敌敌畏，这表明脱溴是主要反应途径。敌敌畏也是一种已注册的杀虫剂，其毒性比二溴磷更大。在5℃下，二溴磷与硫氢根和苯硫酚盐反应的二级反应速率常数分别为10.2±0.4 M⁻¹ s⁻¹和27.3±0.9 M⁻¹ s⁻¹，而二溴磷与硫化氢和苯硫酚反应的二级反应速率常数与零无显著差异。在5℃下，二溴磷与硫代硫酸根反应的二级反应速率常数为5.0±0.3 M⁻¹ s⁻¹。相比之下，在25℃下，敌敌畏与硫氢根反应的二级反应速率常数为(3.3±0.1)×10⁻³ M⁻¹ s⁻¹。还通过在一定温度范围内测量的二级反应速率常数确定了二溴磷与硫氢根反应的活化参数。结果表明，还原态硫物种在沿海海洋环境中二溴磷和敌敌畏的转化过程中可能起着非常重要的作用。可以预期，在存在还原态硫物种的情况下，二溴磷几乎会立即转化为毒性更强的敌敌畏，其预期半衰期为4天至数周。
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