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首页> 外文期刊>Atmospheric Chemistry and Physics Discussions >Contributions of biomass-burning, urban, and biogenic emissions to the concentrations and light-absorbing properties of particulate matter in central Amazonia during the dry season
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Contributions of biomass-burning, urban, and biogenic emissions to the concentrations and light-absorbing properties of particulate matter in central Amazonia during the dry season

机译：干旱季节中亚马孙地区中部生物质燃烧，城市和生物源排放物对颗粒物浓度和光吸收特性的贡献

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Urbanization and deforestation have important impacts on atmospheric particulate matter (PM) over Amazonia. This study presents observations and analysis of PM sub1/sub concentration, composition, and optical properties in central Amazonia during the dry season, focusing on the anthropogenic impacts. The primary study site was located 70?km downwind of Manaus, a city of over 2?million people in Brazil, as part of the GoAmazon2014/5 experiment. A high-resolution time-of-flight aerosol mass spectrometer (AMS) provided data on PM sub1/sub composition, and aethalometer measurements were used to derive the absorption coefficient bsubabs,BrC/sub of brown carbon (BrC) at 370?nm. Non-refractory PM sub1/sub mass concentrations averaged 12.2 μ g?m sup?3/sup at the primary study site, dominated by organics (83?%), followed by sulfate (11?%). A decrease in bsubabs,BrC/sub was observed as the mass concentration of nitrogen-containing organic compounds decreased and the organic PM sub1/sub O:C ratio increased, suggesting atmospheric bleaching of the BrC components. The organic PM sub1/sub was separated into six different classes by positive-matrix factorization (PMF), and the mass absorption efficiency Esubabs/sub associated with each factor was estimated through multivariate linear regression of bsubabs,BrC/sub on the factor loadings. The largest Esubabs/sub values were associated with urban ( 2.04±0.14 m sup2/sup g sup?1/sup ) and biomass-burning ( 0.82±0.04 to 1.50±0.07 m sup2/sup g sup?1/sup ) sources. Together, these sources contributed at least 80?% of bsubabs,BrC/sub while accounting for 30?% to 40?% of the organic PM sub1/sub mass concentration. In addition, a comparison of organic PM sub1/sub composition between wet and dry seasons revealed that only part of the 9-fold increase in mass concentration between the seasons can be attributed to biomass burning. Biomass-burning factor loadings increased by 30-fold, elevating its relative contribution to organic PM sub1/sub from about 10?% in the wet season to 30?% in the dry season. However, most of the PM sub1/sub mass ( 60 %) in both seasons was accounted for by biogenic secondary organic sources, which in turn showed an 8-fold seasonal increase in factor loadings. A combination of decreased wet deposition and increased emissions and oxidant concentrations, as well as a positive feedback on larger mass concentrations are thought to play a role in the observed increases. Furthermore, fuzzy c -means clustering identified three clusters, namely “baseline”, “event”, and “urban” to represent different pollution influences during the dry season. The baseline cluster, representing the dry season background, was associated with a mean mass concentration of 9±3 μ g?m sup?3/sup . This concentration increased on average by 3 μ g?m sup?3/sup for both the urban and the event clusters. The event cluster, representing an increased influence of biomass burning and long-range transport of African volcanic emissions, was characterized by remarkably high sulfate concentrations. The urban cluster, representing the influence of Manaus emissions on top of the baseline, was characterized by an organic PM sub1/sub composition that differed from the other two clusters. The differences discussed suggest a shift in oxidation pathways as well as an accelerated oxidation cycle due to urban emissions, in agreement with findings for the wet season.
机译：城市化和森林砍伐对亚马逊地区的大气颗粒物（PM）具有重要影响。这项研究提供了观察和分析干旱季节中亚马逊地区中部PM 1 的浓度，组成和光学性质，重点是人为影响。作为GoAmazon2014 / 5实验的一部分，主要研究地点位于马瑙斯（Manaus）顺风70公里处，该城市是巴西人口超过200万的城市。高分辨率飞行时间气溶胶质谱仪（AMS）提供了有关PM 1 成分的数据，并使用酒精度计测量得出了吸收系数b abs，BrC 在370？nm的棕色碳（BrC）。主要研究地点的非难治性PM 1 质量浓度平均为12.2μg？m ？3 ，有机物占83％，硫酸盐占11％。 ％）。随着含氮有机化合物质量浓度的降低和有机PM 1 O：C比例的增加，b abs，BrC 的减少被观察到，这表明大气中的漂白。 BrC组件。通过正矩阵分解（PMF）将有机PM 1 分为六个不同的类别，并通过多元线性回归估算与每个因子相关的质量吸收效率E abs b abs，BrC 对因子负荷的影响。最大E abs 值与城市（2.04±0.14 m 2 g ？1 ）和生物质燃烧（0.82±0.04至1.50）有关±0.07 m 2 g ？1 ）源。这些来源加在一起至少占b abs，BrC 的80％，而占有机PM 1 质量浓度的30％至40％。此外，比较湿季和干季的有机PM 1 组成发现，在各季之间，质量浓度增加9倍的部分原因只能归因于生物质燃烧。生物质燃烧因子负荷增加了30倍，将其对有机PM 1 的相对贡献从湿季的约10％提高到了旱季的30％。然而，两个季节中大部分的PM 1 物质（> 60％）都是由生物成因的有机有机物造成的，这反过来又表明因子负荷的季节性增加了8倍。湿沉降的减少和排放物和氧化剂浓度的增加，以及较大质量浓度的正反馈相结合，在观察到的增加中起了作用。此外，模糊c均值聚类确定了三个集群，即“基线”，“事件”和“城市”，以代表干旱季节的不同污染影响。代表干旱季节背景的基线簇与平均质量浓度为9±3μg？m ？3 相关。无论是城市群还是事件群，该浓度平均增加3μg？m ？3 。事件群代表着生物量燃烧和非洲火山排放物的远距离运输影响的增加，其特征是硫酸盐浓度非常高。城市群代表了马瑙斯排放量在基线之上的影响，其特征在于有机的PM 1 组成与其他两个群不同。所讨论的差异表明，由于城市排放，氧化途径发生了转变，并加速了氧化周期，与雨季的发现一致。

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