Drilosphere Properties And Their Influence On PCP Dissipation In Soil

As a widely used pesticide and herbicide in 20 th Century, Pentachlorophenol(PCP) has caused serious soil pollution due to its persistent stability, high bioaccumulation and strong toxicity. Thus, the dissipation of soil PCP has been the focus of researchers. Microbial degradation is the main pathway of PCP dissipation in soil. Drilosphere is an important functional domains in soil. Based on our previous result that earthworm could accelerate the dissipation of PCP, we studied:(1) the PCP dissipation in drilosphere and non-drilosphere,(2) the physiochemical and biological properties of drilosphere,(3) and the relationship between PCP dissipation and drilosphere properties, to figure out the mechanism of acceleration of earthworm on PCP dissipation via a microcosm incubation.This study will provide theory support for new technologies of remediation of soil polluted by organic compounds.The main results and conclusions are as follows:(1) PCP dissipation in drilosphere and non-drilosphere was significantly different. At the 56 th day of the incubation, gut(G) had the highest extractable PCP, while the extractable PCP in cast(C) and burrow(B) were the lowest, both significantly lower than those in non-drilosphere.(2) There were obvious difference between drilosphere and non-drolosphre in soil physical, chemical and biological properties. ESEM showed that there were small aggregates and multi-level porosity in cast; results of specific surface area(BET), entrance pore size, Zeta potential demonstrated that burrow and cast had better physical properties; drilosphere had higher p H, CEC and organic matter content in drilosphere. Microbial physiological activity were higher in drilosphere as Biolog Eco micro-plate showing. However, diversity and richness of bacteria were lower than those in non-drilosphere. Under the stress of PCP, drilosphere exerted to enrich certain PCP-tolerant or PCP-degradation bacteria. In burrow and cast, the abundance of Burkholderia and Xanthomonadaceae unnamed increased along with the incubation, while in gut Citrobacter and Sporosarcina were enriched.(3) The PCA analysis showed the main factors driving PCP dissipation were HWTOC, WTOC, richness, and Zeta potential. Cast and burrow offered an appropriate interface environment for microbial growth, which could increase PCP degradation. The enrichment of Burkholderia and Xanthomonadaceae unnamed in cast and burrow may be the direct reasons of their lower extrable PCP at the end of the incubation.