| At present,the sediment of urban water has changed from the "sink" of pollutants to the "source",resulting in secondary pollution,so the organic matter and nitrogen pollution still affect the river water environment.Therefore,the remediation of polluted sediment is very necessary.Humic-reducing bacteria have attracted extensive attention because they can use the humus in the sediment to participate in the pollutants biodegradation.However,there are differences in physical and chemical properties and pollution degree of sediment,and humic-reducing bacteria lack in-depth research on the remediation effect of sediment with different pollution degree.Therefore,this paper explores the general feasibility and effect difference of humic-reducing bacteria and its strengthening measures in the remediation of river sediment with different pollution degree.According to the content of total organic matter(TOM),the river sediment is divided into high pollution(TOM >100 g/kg)and low pollution(TOM <100 g/kg).Seven typical rivers in Tianjin are selected to explore the effect of adding humicreducing bacteria to restore sediment.On this basis,two representative rivers with significant differences were further selected to explore the strengthening effect and mechanism of calcium nitrate combined with bacterial agent in the remediation of TOM in river sediment.In the high pollution group,TOM degradation rate of the group treated with 5‰bacterial agent was positively correlated with the TOM content.In the low pollution group,the TOM degradation was mainly light fraction organic matter(LFOM),the degradation rate of LFOM was about 37%,and the degradation rate of heavy fraction organic matter(HFOM)was about 16%;The degradation degree of HFOM and LFOM in high pollution group is similar,the degradation rate of HFOM is about 21%,and the degradation rate of LFOM is about 18%.In addition,polyphenol oxidase activity is related to the TOM degradation.The average reduction of polyphenol oxidase activity in the high pollution group(93.48 nmol diqc/min/g)is higher than that in the low pollution group(48.29 nmol diqc/min/g),indicating that the bacterial agent can improve the degradation of sediment HFOM by using the refractory substances transformed by polyphenol oxidase.To further explore the strengthening effect of calcium nitrate combined with bacterial agent in remediation of river sediment.At the end of the experiment,the TOM degradation rate of chemical + bacterial agent group in high and low polluted rivers was 16.78% and 11.43% higher than that of the blank group respectively,which was equivalent to that at the end of single bacteria remediation experiment,indicating that collaborative remediation can improve the TOM degradation rate by 1.8 times.The degradation rate of sulfide in the sediment of the chemical + bacterial group in the highly polluted river increased faster than that of TOM,indicating that for the sediment with high sulfide and TOM pollution,sulfur autotrophic denitrification preceded the dissimilatory reduction of nitrate;The analysis of flora structure also showed that the abundance of flora related to nitrogen and sulfur cycle increased by collaborative remediation accounted for more.The growth rate of AVS degradation rate in the chemical + bacterial group of low pollution river is similar to that of TOM degradation rate.The analysis of flora structure also shows that collaborative remediation improves the abundance of flora related to carbon,nitrogen and sulfur cycle.In conclusion,humic-reducing bacteria have remediation effects on river sediment with different pollution degrees,and calcium nitrate combined with bacteria remediation method improves the TOM degradation rate and shortens the remediation time.It provides a reference for the popularization and application of bacterial agents. |
