Microbial responses to the use of NaClO in sediment treatment

Chlorine is often used in algal removal and deodorization of landscape waters,and occasionally used as an emergency treatment of heavily polluted sediments.However,the ecological impact of this practice has not been fully studied and recognized.In this study,NaClO at 0.1 mmol/g based on dry weight sediment was evenly mixed into the polluted sediment,and then the sediment was incubated for 150 days to evaluate its microbial effect.Results showed that NaClO addition enhanced the release of TOC,TN,Cr and Cu from the sediment.The microbial richness in the examined sediment decreased continuously,and the Chao1 index declined from 4241 to 2731,in 150 days.The microbial community composition was also changed.The abundance of Proteobacteria and Bacteroidetes increased to 54.8%and 4.2%within 7 days compared to the control,and linear discriminant analysis(LDA)showed gram-negative bacteria and aerobic bacteria enriched after chlorination.The functional prediction with PICRUSt2 showed the functions of the microbial community underwent major adjustments,and the metabolic-related functions such as carbon metabolism,including pyruvate and methane metabolisms were significantly inhibited;besides,15 out of 22 analyzed key enzymes involved in C cycling and 6 out of 12 key enzymes or genes involved in N cycling were strongly impacted,and the enzymes and genes involved in carbon degradation and denitrification showed remarkable downregulation.It can be concluded that chlorination posed a seriously adverse effect on microbial community structure and function.This study deepens the understanding of the ecological effects of applying chlorine for environmental remediation.

Microbial response to designer biochar and compost treatments for mining impacted soils

The Oronogo-Duenweg mining belt is a designated United States Environmental Protection Agency Superfund site due to lead-contaminated soil and groundwater by former mining and smelting operations.Sites that have undergone remediation-in which the O,A,and B horizons have been removed alongside the lead contamination-have an exposed C horizon and are incalcitrant to revegetation efforts.Soils also continue to contain quantifiable Cd and Zn concentrations.To improve soil conditions and encourage successful site revegetation,our study employed three biochars,sourced from different feedstocks(poultry litter,beef cattle manure,and lodgepole pine),at two rates of application(2.5%,and 5%),coupled with compost(0%,2.5%and 5%application rates).Two plant species-switchgrass(Panicum virgatum)and buffalograss(Bouteloua dactyloides)-were grown in the amended soils.Amendment of soils with poultry litter biochar applied at 5%resulted in the greatest reduction of soil bioavailable Cd and Zn.Above-ground biomass yields were greatest with beef cattle manure biochar applied at 2.5%with 5%compost,or with 5%biochar at 2.5%and 5%compost rates.Maximal microbial biomass was achieved with 5%poultry litter biochar and 5%compost,and microbial communities in soils amended with poultry litter biochar distinctly clustered away from all other soil treatments.Additionally,poultry litter biochar amended soils had the highest enzyme activity rates forβ-glucosidase,N-acetyl-β-D-glucosaminidase,and esterase.These results suggest that soil reclamation using biochar and compost can improve mine-impacted soil biogeophysical characteristics,and potentially improve future remediation efforts.