Study On Enhanced Control Of Glucocorticoid Infiltration In Complex Riverbed System

The existence of glucocorticoids in rivers and lakes has attracted more and more attention because glucocorticoids may cause harm to the ecological environment even at low concentrations.As the contaminated surface water seeps downward,the riverbed will act as a barrier to its longitudinal migration.But in order to guarantee flood discharge capacity and frequently to make natural rivers dredging river bed resistance control ability of this kind of refractory organic matter is destroyed,so urgent need to develop for glucocorticoid in surface water infiltration of groundwater in the process of strengthening control technology research,in order to solve because of natural rivers dredging river ecosystem and the influence of the section carrying capacity.In this study,a representative synthetic fluoroglucocorticoid-containing Triamcinolone acetonide?TA?was selected as the target pollutant,and biochar composite riverbed was constructed to enhance the retention and control effect of dredged riverbed on glucocorticoid infiltration.Iron and sulfur modified biochar were prepared,and the best composite bed material was selected by adsorption and attenuation fitting.At the same time,the mechanism of biodegradation TA in composite riverbed system was discussed from the aspects of microbial community structure and functional genes.Finally,a compound riverbed reinforcement control system is constructed to simulate the results of long-term operation in real environment.The characterization and adsorption experiment results of the materials showed that the zero-valent nano-iron modified biochar?nZVI@BC?had a core-shell structure and a higher specific surface area,and had a higher adsorption capacity and adsorption rate for TA,which were 5.94 times and 1.85 times higher than that of the natural riverbed.At the same time,the attenuation of TA in the composite riverbed system conforms to the two-compartment first-order dynamic model equation.The early attenuation process is dominated by adsorption,and the adsorption contribution rate reaches80%.After the gradual saturation of adsorption,the biodegradation contribution rate increased to 60%,which played a leading role in the TA removal process,among which the introduction of nZVI@BC increased the biodegradation rate of the natural riverbed by 12.18 times respectively.To compound bed to remove exploration results show that the mechanism of TA TA removal rely mainly on the reduction of microorganism in compound bed defluorization,iron oxide system provide electron donor to promote this process,at the same time the introduction of nZVI@BC to restore the microbial diversity,community structure improvement,increasing the dehalogenation gene copy number,etc,to promote the biodegradation of the TA;It is speculated that the biodegradation pathways of TA mainly include reduced defluorination,hydroxyl oxidation and ring-opening lysis.Simulation results of the composite riverbed reinforcement control system show that the modification of nZVI@BC enhances the control of TA retention by natural riverbed,and the TA concentration in the composite riverbed system decreases rapidly with the increase of depth and time extension,and the attenuation conforms to the first-order dynamic model.The space-time attenuation coefficient of TA in nZVI@BC composite riverbed system is 0.264 d^-1,which is 8.12 times higher than that of natural riverbed.The pollutant attenuation is mainly caused by the enrichment of the biodegradable pseudomonas and Mycobacteria.At the same time,different complex bed depth and infiltration time will cause the difference of ORP,DO,pollutant concentration and other environmental conditions in the system,thus affecting the microbial community structure.