加速溶剂萃取法评价土壤中六氯苯和五氯苯对水稻根的生物有效性

采用温室盆栽实验,选择红壤性水稻土和乌栅土,分别设定对照及添加1%和2%有机肥的处理,评价水稻根系对土壤中六氯苯(HCB)及其主要降解产物五氯苯(PeCB)的吸收富集能力,并比较水稻根中富集的HCB或PeCB量与4种溶剂(体积比3/1的正己烷/丙酮、乙醇、正己烷、水)提取的土壤中HCB或PeCB量的相关性,以评价土壤中HCB和PeCB对水稻根的生物有效性.结果表明,红壤性水稻土和乌栅土中,水稻根富集的HCB浓度平均分别为364.1和306.0ng/g,水稻根中PeCB浓度平均分别为12.7和28.7ng/g,主要原因是HCB在红壤性水稻土中的降解效率低于乌栅土.2种土壤中添加1%和2%的有机肥抑制HCB降解,因此降低水稻根中PeCB的浓度.水稻根中HCB和PeCB与4种溶剂提取的土壤中HCB和PeCB量的相关系数大小次序均为:乙醇正己烷/丙酮正己烷水,表明采用乙醇提取的土壤中HCB和PeCB量对评价其对水稻根生物有效性的效果最佳.4种溶剂中,仅乙醇提取的土壤中HCB与水稻根中HCB量呈显著正相关,而除水以外的其它3种溶剂提取的土壤中PeCB与水稻根中PeCB量均显著正相关.本研究表明,采用加速溶剂萃取法,通过选择合适的提取溶剂,评价土壤中HCB和PeCB对水稻根的生物有效性具有可行性.

Evaluation of Bioavailability of Hexachlorobenzene and Pentachlorobenzene to Rice Roots in Soils by Accelerated Solvent Extraction

A pot experiment was conducted in greenhouse in two types of soils, Hydragric Acrisols(Ac) and Gleyi-Stagnic Anthrosols(An). Three treatments as control and the additions of 1% and 2% organic fertilizer were designed in each type of soil. The objective of this study was to evaluate the accumulation abilities of hexachlorobenzene(HCB)and its predominant metabolite of pentachlorobenzene(PeCB)by rice roots, and to compare the correlation between HCB or PeCB concentrations in rice roots and in soils extracted by four extraction solvents(hexane/acetone=3/1(V/V), ethanol, hexane, water)to evaluate the bioavailability of HCB and PeCB to rice roots. The results showed that the mean concentrations of HCB in rice roots for Ac and An were 364.1 and 306.0 ng/g, respectively, while PeCB were 12.7 and 28.7 ng/g, respectively, which was due to the higher degradation rates of HCB in An than in Ac. Both the applications of 1% and 2% organic fertilizer inhibited HCB degradation, so as to decrease PeCB concentrations in rice roots either in Ac or An. The orders of correlation coefficient of both HCB and PeCB concentrations in rice roots and in soils extracted by four extraction solvents were ethanol >hexane/acetone > hexane > water, which indicated that ethanol was the best extraction solvent of soils to evaluate the bioavailability of HCB and PeCB to rice roots. Only the HCB concentrations in soils extracted by ethanol were significantly positive correlated with the HCB concentrations in rice roots. And the PeCB concentrations in soils extracted by all solvents except for water were significantly positive correlated with the PeCB concentrations in rice roots. Our results suggested that it was feasible to evaluate the bioavailability of HCB and PeCB to rice roots using accelerated solvent extraction by choosing proper extraction solvent.