caa a22 4500 605516715 CHVBK 20210128100715.0 cr unu---uuuuu 210128e20150501xx s 000 0 eng 10.1007/s10533-015-0095-2 doi (NATIONALLICENCE)springer-10.1007/s10533-015-0095-2 The effect of temperature on the rate, affinity, and 15N fractionation of NO3 − during biological denitrification in soils [Elektronische Daten] [Federico Maggi, William Riley] Nine independent experiments of NO3 − denitrification were analysed using the Arrhenius law and the Eyring's transition-state theory to highlight how temperature affects reaction rate constants, affinities, and kinetic isotopic effects. For temperatures between 20 and 35°C, the Arrhenius law and the transition-state theory described equally well observed temperature increases in 14NO3 − and 15NO3 −denitrification rates (R>0.99 and residuals NRMSE<3.39%, p<0.01). These increases were partly caused by an increase in frequency factor and a slight decrease in activation energy (enthalpy and entropy). Parametric analysis also showed that the affinity of 14NO3 − and 15NO3 − toward a microbial enzyme increased exponentially with temperature and a strong correlation with the rate constants was found (R=0.93, p<0.01). Experimental time- and temperature-averaged fractionation factor α P/S showed only a slight increase with increasing temperature (i.e. lower isotopic effects); however, a comprehensive sensitivity analysis in the concentration-temperature domain using average thermodynamic quantities estimated here showed a more complex response; α P/S was relatively constant for initial bulk concentrations [NO3 −]0≤0.01molkg−1, while substantial nonlinearities developed for [NO3 −]0≥0.01molkg−1 and appeared to be strongly correlated with microbial biomass, whose concentration and activity varied primarily as a function of temperature and available substrate. Values of α P/S ranging between 0.9 and 0.98 for the tested temperatures suggested that interpretations of environmental isotopic signatures should include a sensitivity analysis to the temperature as this affects directly the rate constants and affinities in biochemical reactions and may hide process- and source-related isotopic effects. Springer International Publishing Switzerland, 2015 Denitrification nationallicence 14N and 15N nationallicence Kinetic isotopic effects nationallicence Affinity nationallicence Temperature nationallicence Arrhenius nationallicence Transition-state theory nationallicence α : Fractionation factor (-) nationallicence δ : Isotopic composition (-) nationallicence x, y : Stoichiometric coefficients (-) nationallicence G : Gibbs free energy (Jmol−1) nationallicence h : Planck constant (Js) nationallicence H : Heat content (Jmol−1) nationallicence k : Reaction rate constant (Τ−1) nationallicence K b : Boltzmann constant (JK−1 mol−1) nationallicence K : Affinity (half-saturation concentration) (M) nationallicence S : Entropy content (JK−1 mol−1) nationallicence t : Time (T) nationallicence T : Absolute temperature (K) nationallicence NRMSE : Normalized root mean square error (-) nationallicence R : Correlation coefficient (-) nationallicence Maggi Federico Laboratory for Advanced Environmental Engineering Research, School of Civil Engineering, The University of Sydney, 2006, Sydney, NSW, Australia aut Riley William Earth Systems Division, Climate and Carbon Department, Lawrence Berkeley National Laboratory, 94720, Berkeley, CA, USA aut Biogeochemistry Springer International Publishing 124/1-3(2015-05-01), 235-253 0168-2563 124:1-3<235 2015 124 10533 https://doi.org/10.1007/s10533-015-0095-2 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s10533-015-0095-2 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Maggi Federico Laboratory for Advanced Environmental Engineering Research, School of Civil Engineering, The University of Sydney, 2006, Sydney, NSW, Australia aut NATIONALLICENCE 700 1- Riley William Earth Systems Division, Climate and Carbon Department, Lawrence Berkeley National Laboratory, 94720, Berkeley, CA, USA aut NATIONALLICENCE 773 0- Biogeochemistry Springer International Publishing 124/1-3(2015-05-01), 235-253 0168-2563 124:1-3<235 2015 124 10533