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首页> 外文期刊>Journal of Geophysical Research, D. Atmospheres: JGR >Sources and atmospheric processes impacting oxalate at a suburban coastal site in Hong Kong: Insights inferred from 1year hourly measurements
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Sources and atmospheric processes impacting oxalate at a suburban coastal site in Hong Kong: Insights inferred from 1year hourly measurements

机译：影响香港郊区沿海地区草酸盐的来源和大气过程：根据1年每小时测量得出的见解

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Oxalic acid is one of the most abundant dicarboxylic acids in the atmosphere, receiving a great deal of attention due to its potential influence on cloud condensation nucleus activities. In this work, we report 10 months of hourly oxalate measurements in particulate matter of less than 2.5 μm in aerodynamic diameter (PM_(2.5)) by a Monitor for Aerosols and Gases in ambient Air at a suburban coastal site in Hong Kong from April 2012 to February 2013. A total of more than 6000 sets of oxalate and inorganic ion data were obtained. The mean (±SD) oxalate concentration was 0.34 (±0.18) μgM~(-3), accounting for 2.8% of the total ion mass and 1.5% of the PM_(2.5) mass. Seasonal variation showed higher concentrations in fall and winter (0.54 and 0.36 μgM~(-3), respectively) and lower concentrations in spring and summer (~0.26 μgM~(-3)). Different from the inorganic ions, a shallow dip in the oxalate concentration consistently occurred in the morning after sunrise (around 9:00 A.M.) throughout all seasons. Our analysis suggests that this was likely due to photolysis of oxalate-Fe (III) complex under sunlight. In summer, a small daytime peak was discernable for oxalate and nitrate. This characteristic, together with a more evident diurnal variation of O_3, indicates comparatively more active photochemical oxidation in summer than other seasons. High correlations were observed between oxalate and non-sea-salt SO_4~(2-) (NSS) (R~2 = 0.63) and O_x (O_3+NO_2) (R~2 = 0.48), indicating significant commonality in their secondary formation. Positive matrix factorization analysis of oxalate and other real-time gas and particle-phase component data estimates that secondary formation processes, including secondary gas or aqueous oxidation processes (49%), oxidation processes of biomass burning emissions (37%), accounted for the majority of PM_(2.5) oxalate. A backward trajectories cluster analysis found that higher oxalate/NSS ratios were associated with low pollution samples under the influence of marine air masses while the ratios were lower in high pollution samples that were typically associated with continental airmasses passing through areas of high anthropogenic emissions. Isolating the "low pollution marine" aerosols across the entire data set indicates that oxalate production increased in the summer compared to other seasons, suggesting either more active marine emissions of oxalate precursors or stronger photochemical processes in the summer.
机译：草酸是大气中最丰富的二元羧酸之一，由于其对云凝结核活动的潜在影响而备受关注。在这项工作中，我们报告了从2012年4月起，香港郊区沿海地区的空气中气溶胶和气体监测仪对空气动力学直径（PM_（2.5））小于2.5μm的颗粒物进行了10个月的每小时草酸盐测量。至2013年2月，共获得了6000余套草酸盐和无机离子数据。草酸的平均浓度（±SD）为0.34（±0.18）μgM〜（-3），分别占总离子质量的2.8％和PM_（2.5）质量的1.5％。季节变化显示秋季和冬季的浓度较高（分别为0.54和0.36μgM〜（-3）），而春季和夏季的浓度较低（〜0.26μgM〜（-3））。与无机离子不同，在整个季节中，日出后的早晨（上午9:00左右）始终会出现草酸盐浓度的轻微下降。我们的分析表明，这可能是由于草酸盐-铁（III）配合物在阳光下的光解作用。在夏季，草酸盐和硝酸盐的白天峰值很小。这一特征，加上O_3日变化更为明显，表明夏季的光化学氧化活性高于其他季节。草酸盐与非海盐SO_4〜（2-）（NSS）（R〜2 = 0.63）和O_x（O_3 + NO_2）（R〜2 = 0.48）之间具有高度相关性，表明它们的次级形成具有显着共性。草酸盐和其他实时气相及颗粒相组分数据的正矩阵分解分析估计，次级形成过程（包括次级气体或水相氧化过程（49％），生物质燃烧排放物的氧化过程（37％））占了大部分PM_（2.5）草酸盐。向后轨迹聚类分析发现，在海洋空气质量的影响下，草酸盐/ NSS比值较高与低污染样品有关，而高污染样品中的草酸盐/ NSS比值较低，通常与穿过高人为排放区域的大陆气团有关。在整个数据集中隔离“低污染的海洋”气溶胶表明，与其他季节相比，夏季的草酸盐产量增加，这表明夏季草酸盐前体的海洋排放量增加或夏季的光化学过程更强。

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