Cetkauskaité A, Grigonis U, Berzinskiené J
Department of Biochemistry and Biophysics, Faculty Nature Sciences, Vilnius University, Lithuania.
Ecotoxicol Environ Saf. 1998 May-Jun;40(1-2):19-28. doi: 10.1006/eesa.1998.1637.
Biodegradation of five herbicides, two acetanilides (propanil and propachlor), and three phenylureas (diuron, monuron, and fenuron) was analyzed in samples of river water during a period of 6-8 weeks. Concentrations of 0.2-5.0 mg/liter of the herbicides were used for biodegradation. Two types of river water samples with different numbers of microorganisms were collected from the Neris River: upstream and downstream of the city of Vilnius. The initial concentration of microorganisms varied from 4.7 x 10(5) to 2.7 x 10(6) cells/liter and from 1.4 x 10(8) to 5.3 x 10(8) cells/liter in water samples from the Neris River upstream and downstream of Vilnius, respectively. Chemical analysis was performed by the HPLC technique, using standards of herbicides and likely degradation products. Chemical parameters of different river water samples used in biodegradation experiments were analyzed. A second-order reaction rate model was used for the analysis of biodegradation data. Values of the first-order rate constants (Ka) revealed the following decrease in the biodegradation rate of herbicides: propanil >> diuron > or = monuron = propachlor > fenuron. This sequence was constant for all water samples analyzed. The set of decreasing value of second-order biodegradation rate constants (Kb) differed from the set of first-order constants (Ka) because the total number of bacteria in the water samples varied by up to two orders of magnitude, and this variation influenced the calculated values of Kb. Thus, different sets of Kb values were obtained for the water samples from the river upstream and downstream of the city. Schemes of a variety of biodegradation models are presented, and the suitability of the second-order reaction rate model for the description of biodegradation of xenobiotics is discussed.
在为期6至8周的时间里，对河流水样中五种除草剂、两种乙酰苯胺类（敌稗和毒草胺）以及三种苯基脲类（敌草隆、灭草隆和非草隆）的生物降解情况进行了分析。用于生物降解的除草剂浓度为0.2至5.0毫克/升。从涅里斯河采集了两种微生物数量不同的河流水样：维尔纽斯市上游和下游的水样。涅里斯河上游和下游水样中微生物的初始浓度分别为4.7×10⁵至2.7×10⁶个细胞/升以及1.4×10⁸至5.3×10⁸个细胞/升。采用高效液相色谱技术进行化学分析，使用除草剂及其可能的降解产物标准品。分析了生物降解实验中使用的不同河流水样的化学参数。采用二级反应速率模型分析生物降解数据。一级速率常数（Ka）的值显示出除草剂生物降解速率的如下降低顺序：敌稗>>敌草隆≥灭草隆 = 毒草胺 > 非草隆。对于所有分析的水样，该顺序都是恒定的。二级生物降解速率常数（Kb）的递减值集与一级常数（Ka）的集不同，因为水样中细菌总数最多相差两个数量级，这种变化影响了Kb的计算值。因此，从该市上游和下游河流采集的水样获得了不同的Kb值集。文中呈现了各种生物降解模型的方案，并讨论了二级反应速率模型用于描述异生物质生物降解的适用性。
