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Quantifying Nitrate Formation Pathways in the Equatorial Pacific Atmosphere from the GEOTRACES Peru-Tahiti Transect
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2021-08-27 , DOI: 10.1021/acsearthspacechem.1c00072
Therese (Tess) S. Carter 1 , Emily E. Joyce 2 , Meredith G. Hastings 2
Affiliation  

This study aims to better our collective understanding of the oxidative capacity and atmospheric chemistry over the equatorial Pacific. Bulk and size-segregated filter samples were collected during the GEOTRACES Eastern Tropical Pacific transect (4.1° S, 81.9° W to 10.5° S, 152.0° W; October–December 2013) and measured for aerosol concentration and complete isotopic composition of nitrate (δ15N, δ18O, Δ17O where Δ17O = δ17O – 0.52 × δ18O). Combined size-segregated filters produced data similar to that found in bulk filter samples, and notably neither δ15N nor δ18O showed any trends based on aerosol size. Similar to other studies, NO3 is concentrated (>80%) in the coarse size fractions (>1.5 μm). Bulk aerosol concentrations ranged from 6.6 to 89.8 nmol/m3. The bulk δ15N-, δ18O-, and Δ17O-nitrate ranged from −13.1 to −3.2‰, 68.5 to 79.3‰, and 23.5 to 28.4‰, respectively. Higher δ15N values near the coast are best explained by the influence of continental sources; lower δ15N values far from the coast may be associated with chemical fractionation during long-range transport or an oceanic source. Both Δ17O and δ18O are interpreted using kinetic analysis and gas concentrations from a global atmospheric chemical transport model (GEOS-Chem), which showed that nitrate production in this environment is dominated by OH oxidation (60%) and RONO2 hydrolysis (15%). To best match the δ18O and Δ17O observations in this study, the terminal oxygen isotopic values for ozone must be higher than those suggested by available observations and/or halogen-mediated chemistry must be more important than the models currently suggest.

中文翻译:

从 GEOTRACES 秘鲁-塔希提横断面量化赤道太平洋大气中硝酸盐的形成途径

这项研究旨在更好地了解赤道太平洋上空的氧化能力和大气化学。在 GEOTRACES 东热带太平洋横断面(4.1° S,81.9° W 至 10.5° S,152.0° W;2013 年 10 月至 12 月)期间收集了大量和尺寸分离的过滤器样品,并测量了气溶胶浓度和硝酸盐的完整同位素组成( δ 15 N、δ 18 O、Δ 17 O,其中 Δ 17 O = δ 17 O – 0.52 × δ 18 O)。组合尺寸分离过滤器产生的数据与散装过滤器样品中发现的数据相似,特别是既不是 δ 15 N 也不是 δ 18O 显示出基于气溶胶大小的任何趋势。与其他研究类似,NO 3 在粗粒度部分 (>1.5 μm) 中浓缩 (>80%)。散装气溶胶浓度范围为 6.6 至 89.8 nmol/m 3。大块的 δ 15 N-、δ 18 O- 和 Δ 17 O-硝酸盐的范围分别为 -13.1 至 -3.2‰、68.5 至 79.3‰ 和 23.5 至 28.4‰。海岸附近较高的 δ 15 N 值最好用大陆源的影响来解释;远离海岸的较低的 δ 15 N 值可能与远距离运输或海洋源中的化学分馏有关。Δ 17 O 和 δ 18使用来自全球大气化学传输模型 (GEOS-Chem) 的动力学分析和气体浓度来解释 O,表明该环境中的硝酸盐生产主要由 OH 氧化 (60%) 和 RONO 2水解 (15%)主导。为了最好地匹配本研究中的 δ 18 O 和 Δ 17 O 观测值,臭氧的终端氧同位素值必须高于现有观测值所建议的值和/或卤素介导的化学必须比当前模型建议的更重要。
更新日期:2021-10-22
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