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<p>Nitrous oxide (<span class="inline-formula">N₂O</span>) is the primary atmospheric constituent involved in stratospheric ozone depletion and contributes strongly to changes in the climate system through a positive radiative forcing mechanism. The atmospheric abundance of <span class="inline-formula">N₂O</span> has increased from 270&thinsp;ppb (parts per billion, 10<span class="inline-formula">⁻⁹</span>&thinsp;mole&thinsp;mole<span class="inline-formula">⁻¹</span>) during the pre-industrial era to approx. 330&thinsp;ppb in 2018. Even though it is well known that microbial processes in agricultural and natural soils are the major <span class="inline-formula">N₂O</span> source, the contribution of specific soil processes is still uncertain. The relative abundance of <span class="inline-formula">N₂O</span> isotopocules (<span class="inline-formula">¹⁴N¹⁴N¹⁶N</span>, <span class="inline-formula">¹⁴N¹⁵N¹⁶O</span>, <span class="inline-formula">¹⁵N¹⁴N¹⁶O</span>, and <span class="inline-formula">¹⁴N¹⁴N¹⁸O</span>) carries process-specific information and thus can be used to trace production and consumption pathways. While isotope ratio mass spectroscopy (IRMS) was traditionally used for high-precision measurement of the isotopic composition of <span class="inline-formula">N₂O</span>, quantum cascade laser absorption spectroscopy (QCLAS) has been put forward as a complementary technique with the potential for on-site analysis. In recent years, pre-concentration combined with QCLAS has been presented as a technique to resolve subtle changes in ambient <span class="inline-formula">N₂O</span> isotopic composition.</p> <p>From the end of May until the beginning of August 2016, we investigated <span class="inline-formula">N₂O</span> emissions from an intensively managed grassland at the study site Fendt in southern Germany. In total, 612 measurements of ambient <span class="inline-formula">N₂O</span> were taken by combining pre-concentration with QCLAS analyses, yielding <span class="inline-formula"><i>δ</i>¹⁵N^<i>α</i></span>, <span class="inline-formula"><i>δ</i>¹⁵N^<i>β</i></span>, <span class="inline-formula"><i>δ</i>¹⁸O</span>, and <span class="inline-formula">N₂O</span> concentration with a temporal resolution of approximately 1&thinsp;h and precisions of 0.46&thinsp;‰, 0.36&thinsp;‰, 0.59&thinsp;‰, and 1.24&thinsp;ppb, respectively. Soil <span class="inline-formula"><i>δ</i>¹⁵N</span>-<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M22" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="23164037a5a41a281ec2bd2a6e11aeb2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-16-3247-2019-ie00001.svg" width="25pt" height="16pt" src="bg-16-3247-2019-ie00001.png"/></svg:svg></span></span> values and concentrations of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M23" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NO</mi><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="9d4fcb6817fb360ca45e4c6c5f1d67f7"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-16-3247-2019-ie00002.svg" width="25pt" height="16pt" src="bg-16-3247-2019-ie00002.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M24" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msubsup><mi mathvariant="normal">NH</mi><mn mathvariant="normal">4</mn><mo>+</mo></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="ae42caf6f031f0c6641dd1d09f6cb28c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-16-3247-2019-ie00003.svg" width="24pt" height="15pt" src="bg-16-3247-2019-ie00003.png"/></svg:svg></span></span> were measured to further constrain possible <span class="inline-formula">N₂O</span>-emitting source processes. Furthermore, the concentration footprint area of measured <span class="inline-formula">N₂O</span> was determined with a Lagrangian particle dispersion model (FLEXPART-COSMO) using local wind and turbulence observations. These simulations indicated that night-time concentration observations were largely sensitive to local fluxes. While bacterial denitrification and nitrifier denitrification were identified as the primary <span class="inline-formula">N₂O</span>-emitting processes, <span class="inline-formula">N₂O</span> reduction to <span class="inline-formula">N₂</span> largely dictated the isotopic composition of measured <span class="inline-formula">N₂O</span>. Fungal denitrification and nitrification-derived <span class="inline-formula">N₂O</span> accounted for 34&thinsp;%–42&thinsp;% of total <span class="inline-formula">N₂O</span> emissions and had a clear effect on the measured isotopic source signatures. This study presents the suitability of on-site <span class="inline-formula">N₂O</span> isotopocule analysis for disentangling source and sink processes in situ and found that at the Fendt site bacterial denitrification or nitrifier denitrification is the major source for <span class="inline-formula">N₂O</span>, while <span class="inline-formula">N₂O</span> reduction acted as a major sink for soil-produced <span class="inline-formula">N₂O</span>.</p>