Effect Of Biochar On The Dibutyl Phthalate Bioavailability And Microbial Community Structure Diversity In DBP-contaminated Soil

Phthalic acid esters(PAEs), a class of environmental endocrine disruption compounds, are potentially to be carcinogenic, mutagenic and teratogenic to human. Dibutyl phthalate(DBP) is one of the most commonly used PAEs,and is often found in agricultural soils.Biochar has porous structure and large surface area. It can be used for remediation of contaminated soils. In our study, a 56-day incubation experiment was conducted to evaluate the effects of biochar types(bamboo biochar and straw biochar) and application rates(0%, 0.5% and 2%) on the bioavailbility of DBP and diversity of microbial community structure in two soils contaminated by DBP. The content of DBP residual in soil was analyzed with ultrasonic assisted extraction-gas chromatography(GC). Diversity of microbial community structure was analyzed with the phospholipid fatty acids(PLFA) method. The main results obtained from this study were as follows.(1) Compared to control, adding bamboo biochar significantly(P < 0.05) reduced the DBP concentration in the high and low organic matter soils. In the low organic matter soil, the content of DBP significantly(P < 0.05) increased by 77.81% in the 2% straw biochar treatment. The biochar amendments(0.5%、2%) had no significant influence on the content of DBP in the high organic matter soil.(2) The bacterial PLFA, fungal PLFA and microbial community’s total PLFA of the high organic matter content soil was significantly(P < 0.05) higher than those of the low organic matter soil. Bacterial PLFA, fungal PLFA and microbial community’s total PLFA of the high organic matter soil showed a significant(P < 0.05) increase in the 2% straw biochar treatment, whereas a significant(P < 0.05) reduction in the PLFA values of the low organic matter soil was observed in the bamboo biochar treatments. Adding biochar made the content of bacterial PLFA, fungal PLFA and microbial community’s total PLFA have the same tendency.(3) In the low organic matter soil, the ratio of Gram-negative bacteria/Gram-positive bacteria reached the highest level in the 2% straw biochar treatment, whereas the soil microbial community Shannon Index reached the lowest level in the 2% bamboo biochar treatment. The soil microbial stress level reached the lowest level in the 2% straw biochar treatment. The biochar type and application rate had no significant influence on the ratios of fungi/bacteria, Gram-negative bacteria/Gram-positive bacteria, and microbial community Shannon Index in the soil with high organic matter content.(4) Based on the principal component analysis, biochar type and application rate could influence soil microbial community structure, which was closely related to the soil organic matter content.In conclusion, bamboo biochar had greater potential for decreasing the bioavailability of DBP in soil than that of the straw biochar. Biochar type and application rate and soil organic matter content could influence diversity of soil microbial community structure, and the effect of soil organic matter appeared to be stronger than that of the biochar.