环境有机质对FeS—水体系中林丹脱氯转化的影响

Effects of environmental organic matters on dechlorination of lindane by ferrous sulfide

采用批处理方法,评价几种典型的环境有机质对缺氧或无氧FeS—水体系中,林丹非生物脱氯转化动力学的影响。测定了不同反应介质条件下,林丹的非生物脱氯转化速率和产物的分布。结果表明,反应体系中高浓度的表面活性剂对林丹的转化有明显的抑制作用,转化速率为对照体系的18%;萘醌对林丹转化的速率及其产物分布均没有明显的影响;加入25mg/L胡敏酸可使林丹的转化速率提高1.29倍;加入2mmol/L2,2′-联吡啶明使林丹的转化速率提高2.2倍。研究表明,水生态环境中与FeS共存的有机物可能对有机氯污染物的自然衰减产生较大影响。

The present paper is aimed at reporting the effects of the environmental organic matters on the dechlorination of lindane by ferrous sulfide through a series of batch experiments. As is known, natural organic matters coexistent in the aqueous environments are generally thought of to be an important factor that is likely to affect the transformation of the organic pollutants. To fulfill the batch experiments, we performed necessary assessment of the effects of such matters on the rates and products of the transformation by ferrous sulfide （FeS） so as to able to find out the rates and products as well as the distribution ratios of FeS-mediated transformation of lindane with the different solution organic matters. The pseudo-first-order rate constants （kobs） of the transformation of lindane in the presence and absence of FeS are 0.012 8 d^-1 and 0.005 1 d^-1, respectively on the condition of no more additional organic matter in the reaction systems. At the same time, the high concentration surfactant in the reaction system would significantly slow the rate of lindane transformation. Then, it can be found that kob, of transformations of lindane in the 20 mL/L Triton X-100 mediated reaction system with and with no FeS are respectively 0.002 3 d^-1 and 0.004 6 d^-1, which indicates that the high concentrated surfactant would significantly help to slow down the rate of the transformation. However, in the homogeneous system, the added 25 mg/L humic acid, 2 mmol/L 2,2＇-bipyridine, and 2 mmol/L 1,4-naphthoquinone, the values of kobs, of transformation prove to be quite similar to those of the systems with no added organic matter. Such results indicate that the coexistent matters with lindane in water would not bring any remarkable influence on the lindane dehydrochlorination. While in the FcS mediated reaction buffer, the coexistent 25 mg/L humic acid and 2 mmol/L 2,2＇-bipyridine help to increase the rates of dechlorination of lindane by 1.29 time and 2.2 times, respectively, and 2 mmol/L 1,4-naphthoquinonc would not bring noticeable the transformation rates obviously. Thus, the results of our study naturally suggest that the organic matters coexistent with FeS in the environment may have strong effects on the natural attenuation of organochlorine contaminants in the aqueous ecosystem.