摘要:
通过多隔层根际箱培养试验研究疏水性有机污染物对二氯苯(1,4-DCB)和重金属Cd单一与复合污染对不同作物毫米级根际微域土壤脱氢酶和脲酶活性的毒性效应，并利用联合作用模型分析二者联合毒性效应的作用类型。结果表明：与对照组相比，1,4-DCB单一胁迫抑制大豆各毫米级根际微域土壤脱氢酶活性，但能促进脲酶活性；低浓度1,4-DCB抑制小麦根际微域土壤脱氢酶和脲酶活性，高浓度1,4-DCB则促进近根际区域脱氢酶和脲酶活性。低浓度Cd胁迫促进大豆根际微域土壤脱氢酶活性，高浓度Cd则起抑制作用；脲酶活性则随Cd浓度增加而显著增加，均高于对照组；Cd抑制小麦各毫米级根际微域土壤脱氢酶和脲酶活性。随根际距离增加，大豆近根际区域（1 mm）土壤脲酶活性受到诱导，而小麦中央区域和1、2 mm近根际区域土壤脱氢酶活性被显著抑制。二者复合污染对植物毫米级根际微域土壤酶活性的联合毒性效应与其浓度组合、植物种类、根际距离以及酶类型有关。
Abstract:
The single and joint toxic effects of hydrophobic organic compounds 1,4-dichlorobenzene(1,4-DCB) and heavy metal Cd on the activities of urease and dehydrogenase in the millimeter rhizosphere were investigated through rhizobox culture experiments. The interactions modes between 1,4-DCB and Cd were further analyzed and assessed based on the mathematical models. The results showed that the occurrence of 1,4-DCB inhibited dehydrogenase activities, but enhanced urease activities in the millimeter rhizosphere of soybean, compared with the control. Single stress of lower concentrations of 1,4-DCB reduced the activities of dehydrogenase and urease in the millimeter rhizosphere of wheat, while higher levels of 1,4-DCB promoted the activities of dehydrogenase and urease in the near-millimeter rhizosphere of wheat. The single stress of lower concentrations of Cd promoted the activities of dehydrogenase while the stress of higher concentrations of Cd inhibited the activities of dehydrogenase in the millimeter rhizosphere of soybean. The activities of urease in the millimeter rhizosphere of soybean increased with the increasing concentration of Cd. The single treatments of Cd inhibited the activities of dehydrogenase and urease in the millimeter rhizosphere of wheat, compared with the control. The changes of the activities of dehydrogenase and urease in the millimeter rhizosphere with distances were complicated under the pollution of 1,4-DCB and Cd. Generally, the stress of 1,4-DCB and Cd resulted in the increases of urease activities in near-rhizosphere (1 mm) of soybean and the decreases of dehydrogenase activities in root compartment and near-rhizosphere (1 and 2 mm) of wheat. The interactive modes of 1,4-DCB and Cd on enzymes activities in the millimeter rhizosphere depended on their concentration combinations, crop species, distances of millimeter rhizosphere and enzyme types.
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