Convergent evidence for the pervasive but limited contribution of biomass burning to atmospheric ammonia in peninsular Southeast Asia

• Main Authors: Y. Chang, Y.-L. Zhang, S. Kawichai, Q. Wang, M. Van Damme, L. Clarisse, T. Prapamontol, M. F. Lehmann
• Format: Article
• Language: English
• Published: Copernicus Publications 2021-05-01
• Series: Atmospheric Chemistry and Physics
• Online Access: https://acp.copernicus.org/articles/21/7187/2021/acp-21-7187-2021.pdf

<p>Ammonia (<span class="inline-formula">NH₃</span>) is an important agent involved in atmospheric chemistry and nitrogen cycling. Current estimates of <span class="inline-formula">NH₃</span> emissions from biomass burning (BB) differ by more than a factor of 2, impeding a reliable assessment of their environmental consequences. Combining high-resolution satellite observations of <span class="inline-formula">NH₃</span> columns with network measurements of the concentration and stable nitrogen isotope composition (<span class="inline-formula"><i>δ</i>¹⁵N</span>) of <span class="inline-formula">NH₃</span>, we present coherent estimates of the amount of <span class="inline-formula">NH₃</span> derived from BB in the heartland of Southeast Asia, a tropical monsoon environment. Our results reveal a strong variability in atmospheric <span class="inline-formula">NH₃</span> levels in time and space across different landscapes. All of the evidence on hand suggests that anthropogenic activities are the most important modulating control with respect to the observed patterns of <span class="inline-formula">NH₃</span> distribution in the study area. N-isotope balance considerations revealed that during the intensive fire period, the atmospheric input from BB accounts for no more than <span class="inline-formula">21±5</span> % (<span class="inline-formula">1<i>σ</i></span>) of the ambient <span class="inline-formula">NH₃</span>, even at the rural sites and in the proximity of burning areas. Our N-isotope-based assessment of the variation in the relative contribution of BB-derived <span class="inline-formula">NH₃</span> is further validated independently through the measurements of particulate <span class="inline-formula">K⁺</span>, a chemical tracer of BB. Our findings underscore that BB-induced <span class="inline-formula">NH₃</span> emissions in tropical monsoon environments can be much lower than previously anticipated, with important implications for future modeling studies to better constrain the climate and air quality effects of wildfires.</p>