摘要
Thisstudy demonstrates that dual N-O isotopes andkinetic modeling could be tools for distinguishing biological fromchemical processes during microbially mediated NRFO. @@@ Microbially mediated nitrate reduction coupled with Fe(II)oxidation(NRFO) plays an important role in the Fe/N interactions in pH-neutralanoxic environments. However, the relative contributions of the chemicaland microbial processes to NRFO are still unclear. In this study,N-O isotope fractionation during NRFO was investigated. Theratios of O and N isotope enrichment factors ((18)& epsilon;:(15)& epsilon;)-NO3 (-) indicated thatthe main nitrate reductase functioning in Acidovorax sp. strain BoFeN1 was membrane-bound dissimilatory nitrate reductase(Nar). N-O isotope fractionation during chemodenitrification[Fe(II) + NO2 (-)], microbial nitrite reduction(cells + NO2 (-)), and the coupled process[cells + NO2 (-) + Fe(II)] was explored.The ratios of ((18)& epsilon;:(15)& epsilon;)-NO2 (-) were 0.58 & PLUSMN; 0.05 during chemodenitrificationand -0.41 & PLUSMN; 0.11 during microbial nitrite reduction, indicatingthat N-O isotopes can be used to distinguish chemical frombiological reactions. The ((18)& epsilon;:(15)& epsilon;)-NO2 (-) of 0.70 & PLUSMN; 0.05 during the coupledprocess was close to that obtained for chemodenitrification, indicatingthat chemodenitrification played a more important role than biologicalreactions during the coupled process. The results of kinetic modelingshowed that the relative contribution of chemodenitrification was99.3% during the coupled process, which was consistent with that ofisotope fractionation. This study provides a better understandingof chemical and biological mechanisms of NRFO using N-O isotopesand kinetic modeling.
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单位福建农林大学; 天津大学