Transformation Of Pyrene And Tetracycline In The Soil-Vegetable System

Due to the non-standard production and operation of coking plants,steel mills,wastewater treatment plants,and livestock farms,both polar and non-polar organic pollutants(i.e.,polycyclic aromatic hydrocarbons and antibiotics).have been released into the adjacent soils correspondingly.Therefore,it has made the suburban farmland soil the new hotspot of PAH and antibiotic compound pollution.Considering the serious threat these organic pollutants to human health and environmental safety caused by their transfer function of the food chain in soil-vegetables system,it has also become an urgent soil environment problem that needs to be solved.In the present work,microbial enhanced(PAH-degrading bacterium Sphingobium sp.PHE3)pyrene(Pyr)degradation was studied with or without tetracycline existence in the soil.Moreover,the ecological environmental risk of Pyr/TC migration and enrichment in soil-vegetable system was assessed as well.The main results have been listed as follows:(1)The results obtained here indicated that PHE3 inoculation significantly increased the degradation rate of Pyr(p<0.05).At the end of the 90 days of incubation,the removal rate of pyrene for the treatment with sole PHE3 inocuIation(B)and combined inoculation of PHE3 with TC addition(BTC)is 40.1%and 25.7%,respectively,and 23.0 and 14.1 times higher than that of the control(CK).Therefore,TC existence obviously inhibited microbial enhanced degradation of pyrene in soil.(2)A significant increase in soil microbial diversity and function structure were also detected after transient adaptation by PHE3 inoculation to the soil,suggesting a negative correlation between soil microbial activity and pyrene content in the soil.More specifically,exogenous pollutants had a significant effect on soil bacterial community structure diversity and function stability(p<0.05),while it had no significant impact on soil fungal community.In addition,soil catalase activity,FDA enzyme activity and soil microbial biomass carbon and nitrogen(MBC/N)in the treatments B and BTC were also significantly higher than that of P,TC treatment.However,no significant difference could be observed in the soil enzyme activity and MBC/N between P and TC(p>0.05),suggesting that exogenous pollutants had a significant inhibition on soil microbial activity(p>0.05),and weakened the inhibition.(3)Pot experiment with two kinds of vegetable(amaranth(Amaranthustricolor L.)and bean(Phaseolusvulgaris Linn.))(X,D)cultivation in Pyr/TC mixed contaminated soil was carried out.Vegetable cultivation had a significant role in promoting the TC dissipation(p<0.05),with the highest TC dissipation observed in the treatment of X and D.The total disspitation rate of TC is about 77.8%in the treatment of X and D.In addition,the enrichment capability of pyrene in two vegetables(X,D)was low.(4)Two plants were separated into different parts(root,leaf,and seed)for separation and identification of antibiotic resistant endophytic bacteria(AREB).Bacillus genera were found to be the main resistant bacteria,followed by Cohnella genera and Staphylococcus genera.Meanwhile,Pyr addition could significantly reduce the number and variety of vegetable endophytes.Totally eight antibiotic resistance genes were detected:Tetracyclin resistant genes(tetM,tetW),Cmr chloramphenicol resistant genes(cmlA,floR),Sulfa antibiotics resistance genes(sul1 sul2),Macrolides antibiotics resistance gene(ermB),(Class ? integron)intI1.Among these genes,the abundance of three ARGs(tetW,cmlA,floR)and 16srRNA was measured quantitatively as representative.The results showed that the copy number of three ARGs increased after cow manure application.Therefore,as the reservoir of ARGs,the manure application might bring the ARG dissemination risk in the soil-vegetables system.