| With the wide application of pig manure in agriculture,the application of pig manure to increase the harmful components such as heavy metals,antibiotics and antibiotic resistance genes in the soil has been paid more and more attention by the society.However,earthworm is widely used in the treatment of domestic garbage,municipal sludge,and livestock manure.In this experiment,the pig manure after the wet and dry separation produced by the large-scale pig farm in Hainan was used as the substrate,and the Eisenia foetida was inoculated and cultivated in the chamber for 4 weeks.The content of heavy metals(Cu,Zn,Cr,Pb,Cd,As)in pig manure and earthworms at different times were determined by inductively coupled plasma mass spectrometry(ICP-MS).A total of 40 antibiotics including sulfonamides,tetracyclines,chloramphenicols and quinolones in pig manure were determined by LC-MS/MS.Absolute quantification of 10 antibiotic resistance genes in pig manure was performed using real-time fluorescent quantitative PCR.At the same time,high-throughput sequencing technology was used to analyze the microbial diversity in pig manure.The morphological changes of heavy metals in pig manure and the enrichment characteristics of heavy metals in earthworms were systematically studied and the changes of antibiotics and antibiotic resistance genes in pig manure under effects of earthworms and the effects of earthworms on microbial communities in pig manure were studied which provided important basis for the safe application of waste in agricultural production.Experimental results show:(1)After earthworm treatment for 4 weeks,the pH value of pig manure increased from 6.51 to 6.86.Total phosphorus and potassium increased by 9.5%and 28.8%respectively,from 1.59%and 0.73%to 1.37%and 0,94%respectively.After treatment,the total amount of Cu,Zn,Cr,Pb,Cd and As in pig manure was significantly reduced,which was 13.69%,24.47%,30.70%,39,17%,21.91%and 9.36%,respectively.In addition to Cr,the concentrations of Cu,Zn,Cd and As in earthworms increased by 0.49mg/kg,3.86mg/kg,0.012mg/kg and 0.064mg/kg respectively compared with those before the experiment,and showed a certain aging relationship.The order of enrichment coefficient was Cr>Cd>Zn>Cu>As.The results showed that earthworms could enrich the heavy metals in pig manure and reduce the content of heavy metals in pig manure.(2)Tests for antibiotics showed seven antibiotics in the pig manure,which belonged to the two categories of tetracyclines and quinolones.After 4 weeks of treatment the contents of pefloxacin,enrofloxacin and oxytetracycline in the experimental group were reduced by 20.79%,24.03%and 17.98%,respectively.During the 4-week test period,earthworm treatment had no significant effect on the abundance of 10 antibiotic resistance genes in pig manure.The results showed that earthworm could reduce the concentration of pefloxacin,enrofloxacin and oxytetracycline in pig manure,but had no significant effect on the 10 antibiotic resistance genes detected in this experiment.(3)The analysis results of microbial diversity show that the proportions of Proteobacteria,Bacteroides,Firmicutes and Actinobacteria in the test pig manure accounted for the largest proportion,which were 41.0%,23.7%,13.1%and 10.9%respectively.At the 2nd and 4th week after the treatment of pig manure,the six a diversity indices of bacteria increased.After 4 weeks of treatment,the proportion of Firmicutes and Actinobacteria in pig manure increased,and the proportion of Proteobacteria,Bacteroidetes and so on decreased.There is a certain correlation between bacteria in different types of pig manure and different environmental factors.The results of this study show that the treatment of pig manure can reduce some harmful substances in pig manure and improve the manure fertility,which is conducive to the application of pig manure in agriculture.The research results can solve the problem of low waste utilization efficiency and serious pollution in the current stage of animal husbandry in Hainan,and provide a scientific basis for the rational application of waste such as pig manure in ecological cycle agriculture. |
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