土壤腐殖酸对毒死蜱水解的影响

土壤腐殖酸的VIS-UV光谱特征和E465/E665的测定结果表明,各种土壤腐殖酸的VIS-UV吸收曲线相似,但吸收峰强度和E465/E665差异较大,进而推得它们的腐殖化程度排序为:紫色潮土腐殖酸>中性紫色土腐殖酸>酸性紫色土腐殖酸>腐殖土腐殖酸,说明它们在组成上有共同的本性,但结构和性质差异较大。在此基础上,研究它们对毒死蜱水解的影响。结果表明,不同来源土壤腐殖酸均促进了毒死蜱的水解,但它们的影响程度有明显的差异。对于腐殖化程度最低的腐殖土腐殖酸,浓度为120mg L-1时,对毒死蜱水解的促进作用最大,而随着腐殖酸浓度的增大,促进作用却越来越弱;而对于其它三种样品,腐殖酸溶液对毒死蜱水解的促进作用随着腐殖酸浓度增大而加强,其中以腐殖化程度较低的酸性紫色土的促进作用较为明显。可见,毒死蜱的水解速率与土壤腐殖酸的浓度和腐殖化程度有关。其中,腐殖酸腐殖化程度的影响机理主要与腐殖酸的酸性和腐殖酸的吸附—催化作用有关,其具体作用机理有待于进一步从定性和定量方面去研究,以更好地指导毒死蜱农药的合理施用和污染土壤的修复。

The Influences of Humic Acids Isolated from Different Soils on Hydrolysis of Chlorpyrifos

The compositions of humic acids(HAs) in various soils were common in nature,but the aromatic structures,function groups,molecular weight, and the level of HAs from various soils were significantly different.On these base,the influences of HAs on hydrolysis of chlorpyrifos were studied.The results showed that the hydrolysis effect differed for soils that contained different level of HAs.For humus soil with the lowest level of HA,when the concentration was 120mg L-1,it boosted the hydrolysis of chlorpyrifos most significantly;However,the higher the concentration of HA,the smaller the hydrolysis effect.With the concentration of the other three types of HAs increasing,the hydrolysis of chlorpyrifos increased gradually,and the effect of acid purple soil with the lower level of HA was more distinct.Therefore,it may be conferred that the speed of hydrolysis of chlorpyrifos was related to the concentration of HAs and the level of HAs;and the later was concerned with the acid level of HAs and the role of adsorbed-catalysed by HAs,the mechanism of which must be tested further.