铅-苯并[a]芘复合污染在土壤-植物体系的归宿规律研究

Fate of Complex Pollutants of Lead and Benzo[a]pyrene in Soil-Plant System

通过室内盆栽试验研究了中、低浓度铅（Pb）和苯并[a]芘（B[a]p）复合污染在土壤-植物系统中的归宿规律和相互影响,以考查Pb-B[a]p复合污染的相互作用.采用4因素6水平均匀设计试验方案,w（Pb）范围为0～1 120 mg·kg^-1,w（B[a]p）范围为0～6.4 mg·kg^-1.结果表明,在非根际环境中,Pb的不同结合态未受到B[a]p的影响,而土壤中B[a]p的自然降解过程也未受到Pb的影响;在黑麦草根际环境中,Pb的可交换态和碳酸盐结合态以及Fe/Mn氧化物结合态含量与非根际土壤相比明显降低,有机物和硫化物结合态含量明显升高,这与黑麦草根际分泌物和植物根际的吸收作用有关;玉米和黑麦草地上部和根部Pb含量均与土壤中Pb总量之间呈显著正相关关系,与B[a]p含量间不存在显著相关性;在玉米和黑麦草根际环境中,B[a]p的降解速率比非根际土壤有明显提高,其中黑麦草的促降解作用强于玉米;Pb对玉米和黑麦草根际土壤中B[a]p的降解过程具有一定的抑制作用,这与根际环境对Pb的活化作用进而增加Pb对微生物有效性有关;Pb对植物根部吸附B[a]p的过程也有一定影响.总体而言,在根际和非根际条件下B[a]p与Pb的共存均未影响Pb的归宿,在非根际环境中Pb也未影响B[a]p的归宿,但在根际环境中Pb抑制了B[a]p在土壤中的降解及植物根部对B[a]p的吸收.

An indoor pot experiment was conducted to study fate of complex pollutants of Lead （Pb） and benzo[a] pyrene （B[a] p）,low and moderate in concentration,in the soil-plant system and interaction between the two pollutants.The experiment was designed to 4 factors and 6 levels with Pb concentration varying in the range of 0-1 120 mg· kg-1 and B [a]p concentrations in the range of 0-6.4 mg · kg 1 in the soil.Results show that in bulk soil,Pb,regardless of forms,was not affected by the coexisting B[a] p and the natural degradation of B[a] p was also not either by the coexisting Pb.In the rhizosphere soil of ryegrass,the contents of exchangeable and carbonate bound Pb and Fe-Mn bound Pb were obviously lower than in the non-rhizosphere soils,while the contents of organic and sulfide bound Pb significantly higher,which may be attributed to exudation and Pb absorption of the ryegrass roots.Pb concentrations in shoots and roots of corn and ryegrass were found significantly and positively related to the total content of Pb in the soil,but not to content of the coexisting B[a]p.The degradation rates of B[a]p were increased significantly in the corn and ryegrass rhizopheres compared to that in non-rhizosphere soil.The effect of ryegrass is much higher than that of corn.The coexisting Pb in the rhizosphere soils had some inhibiting effect on B[a] p degradation,which may be related to the effect of the rhizosphere environment activating Pb and hence increasing microbial availability of Pb in the rhizosphere soil.Pb also had some effect on absorption of B [a] p by roots.In short,it can be concluded that the coexistence of Pb and B [a] p does not have any effects on the fate of Pb in both rhizosphere and non-rhizosphere environment and Pb has no effect either on the fate of B [a] p in non-rhizosphere environment.However,in rhizosphere environment,Pb affects the degradation of B [a] p as well as the absorption of B [a] p by roots.