| Soil aggregates can coordinate the proportion of water,fertilizer,gas and heat in the soil,cope with the impact of various environments,and provide an important environmental and material basis for the survival of various organisms.Organic pollutants can combine with soil clay to form organic complex,interfere with the process of soil agglomeration,lead to the change of micro bial species and community structure.Diethylhexyl phthalate(DEHP)is a common plasticizer and one of the main components of agricultural film,and it has the effect of "carcinogenic,teratogenic and mutagenic".The extensive use of plastic films in facility agriculture would accumulate higher concentrations of organic pollutants DEHP in the soil,affecting the physical and chemical and biological properties of the soil and even cause a series of agro-ecological problems.In-depth study of the effect of DEHP on the characteristics of soil aggregates has certain theoretical and practical significance for studying the environmental behavior of plasticizers in soil.In this study,black and cinnamon soil,two typical agricultural soils in Northeast China,were selected as the research objects,and the effects of DEHP concentration of 0,5,10,20,40,60 mg/kg on the composition and stability,the content of organic carbon and nitrogen in the aggregate were compared and analyzed.On this basis,the change of microbial community structure in 20 ?m-5mm granular black soil aggregate was further analyzed under DEHP treatment of 0,20,40 and 60 mg/kg.The main results and conclusions of the research were as follows:(1)DEHP changed the proportion composition of aggregates of black and cinnamon soil.The effect of DEHP on soil aggregate composition was studied by dry sieving,The results showed that DEHP increased the proportion of 250 ?m-5mm aggregates in black soil and brown soil,and changed the composition of dominant aggregates in black soil.Through the evaluation of the stability of aggregates,it was found that DEHP improved the average weight diameter(MWD)and the geometric average diameter(GMD)of the two kinds of soil aggregates,reduce d the fractal dimension(D),and "promoted" the stability of aggregates,and with the increase of DEHP treatment concentration,the "promotes" function was more obvious.(2)DEHP affected the agglomeration process through aggregate cement.Using the path analysis method,the relationship between DEHP and the aggregate cement were analyzed.The results showed that DEHP had a direct effect on the aggregate content of 250 ?m-2mm particle size of black soil,and it contributed to the cementation of organic carbon,alumina and iron oxide.DEHP promoted the content of 1-5mm grain aggregates in cinnamon soil significantly.The results of the characterization of the micro morphology of aggregates further explained that the "promoting" effect of DEHP on the stability of aggregates led to the too tight cementation of aggregates,the reduction of porosity on the surface of aggregates,and the "false sand" phenomenon,which was not conducive to the water and fertilizer conservation of soil.(3)DEHP interfered significantly with the transformation of carbon and nitrogen in soil aggregates.The results showed that DEHP could significantly affect the transformation of organic carbon and nitrogen components in the aggregate of 250 ?m-2mm black soil and 250 ?m-5mm brown soil,and reduce the soil quality.The content of soluble organic carbon and readily oxidized organic carbon decreased rapidly with the increase of DEHP concentration.The content of nitrate nitrogen in the agglomerates of black and cinnamon soil decreased significantly under the influence of higher concentration of DEHP.(4)DEHP changed the composition of microbial communities in aggregates.The effect of DEHP on the microbial community of black soil aggregates was studied by high-throughput sequencing.The results showed that DEHP mainly interfered with the microbial community structure of 250 ?m-2mm granular aggregates in black soil.When DEHP concentration was 40mg/kg,the diversity of fungal community was inhibited,and when DEHP concentration was 60mg/kg,the structure of fungal community changed.Through redundancy analysis,DEHP and total organic carbon were the key driving factors for the change of bacterial community structure in black soil aggregates,and DEHP played a leading role in the change of fungal community structure. |
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