首页|Arsenic mobilization and nitrous oxide emission modulation by different nitrogen management strategies in a flooded ammonia-enriched paddy soil
Arsenic mobilization and nitrous oxide emission modulation by different nitrogen management strategies in a flooded ammonia-enriched paddy soil
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Arsenic mobilization and nitrous oxide emission modulation by different nitrogen management strategies in a flooded ammonia-enriched paddy soil
Elevated arsenic(As)mobilization and increased nitrous oxide(N2O)emission are two primary environmental concerns existing in flooded paddy soils.In this study,dissolved As(Ⅲ),N isotope-labeled Na15NO3,and/or 14NH4C1 were incorporated into a microcosm incubation to determine the effects of N fertilization regimes on As mobilization and N2O emission in a flooded paddy soil.Because nitrate had a higher redox potential and comprised a higher proportion of N substrate,As(Ⅴ)was preferentially formed due to enhanced nitrate-dependent microbial As(Ⅲ)oxidation.Thus,As availability was correspondingly attenuated due to the improved production of less mobile and toxic As(Ⅴ).After 2-d incubation,more than 90％and 98％of soluble As(Ⅲ)were immobilized in the As+NH4+-N+NO3-N and As+NO3--N treatments,respectively.Following nitrate depletion(after 2 d),microbial As(Ⅴ)and Fe(Ⅲ)reductions were gradually enhanced,which was attributed to stimulation of anaerobic ammonium oxidation(anammox)coupled to Fe(Ⅲ)reduction,known as Feammox,by the abundance of NH4+.By the end of the incubation period(10 d),the As+NO3--N treatment led to higher As immobilization of originally added As(Ⅲ)(ca.61％)than the As+NH4+-N+NO3--N treatment(42％).The As+NH4+-N+NO3--N treatment prominently mitigated N2O emission compared to the As+NO3--N treatment,which was ascribed to anammox,inducing accumulation of byproducts from incomplete denitrification.High-throughput sequencing indicated that the relative abundances of denitrifiers(e.g.,Azoarcus,Ochrobactrum,and Thiobacillus denitrificans)increased in the As+NO3-treatment,whereas quantitative polymerase chain reaction results indicated higher 16S rRNA gene copy numbers for anammox and Feammox(Acidimicrobiaceae bacterium A6)bacteria in the As+NH4++NO3-treatment.Collectively,the experimental results demonstrated that N fertilization can be a feasible As remediation strategy while providing an effective strategy for mitigating N2O emission from paddy soils at the same time.
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