Chemically-resolved aerosol eddy covariance flux measurements in urban Mexico City during MILAGRO 2006
Chemically-resolved aerosol eddy covariance flux measurements in urban Mexico City during MILAGRO 2006
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DOI：
10.5194/acp-12-7809-2012
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发表时间：
2012-08
影响因子：
6.3
通讯作者：
R. Zalakeviciute;M. Alexander;E. Allwine;J. Jimenez;B. Jobson;L. Molina;E. Nemitz;S. Pressley
中科院分区：
文献类型：
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作者：
R. Zalakeviciute;M. Alexander;E. Allwine;J. Jimenez;B. Jobson;L. Molina;E. Nemitz;S. Pressley
作为米拉格罗2006年实地活动的一部分，从墨西哥城人口稠密社区竖立的一座高塔上测量了大气气溶胶与城市景观的交换。2006年3月，在为期两周的时间里，用四极气溶胶质谱仪用涡流协方差法测量了城市亚微米级气溶胶通量。与其他城市站点的测量结果相比，靠近市中心的这个地点的硝酸盐和铵的气溶胶浓度较高。白天观测到的硝酸盐气溶胶向下通量显著，平均为0.2ugm2 S 1号。城市地表并不是硫酸盐气溶胶的重要来源。测量还表明，以类烃或有机气溶胶(HOA)近似的初级或有机气溶胶通量表现出与二氧化碳通量和人为城市活动相似的日模式。总体而言，47%的亚微米有机气溶胶排放是HOA，35%是氧气(OOA)，18%与生物质燃烧(BBOA)有关。有机气溶胶通量是双向的，但平均HOA通量为0.1ugm2 S 1，OOA通量为0.03µgm2 S 1，BBOA0.03µgm2 S 1。在考虑了尺寸差异(PM1和PM2.5)并使用黑碳成分的估计后，将通量测量结果与2006年墨西哥城网格排放清单进行比较，结果表明，排放清单和通量测量的日平均PM总排放率基本上相同。然而，排放清单包括粉尘和金属颗粒贡献，而这些贡献并未包括在通量计量中。结果，库存似乎低估了这个地区的PM排放总量。
As part of the MILAGRO 2006 field campaign, the exchange of atmospheric aerosols with the urban land- scape was measured from a tall tower erected in a heav- ily populated neighborhood of Mexico City. Urban submi- cron aerosol fluxes were measured using an eddy covari- ance method with a quadrupole aerosol mass spectrometer during a two week period in March, 2006. Nitrate and am- monium aerosol concentrations were elevated at this loca- tion near the city center compared to measurements at other urban sites. Significant downward fluxes of nitrate aerosol, averaging 0.2 µg m 2 s 1 , were measured during daytime. The urban surface was not a significant source of sulfate aerosols. The measurements also showed that primary or- ganic aerosol fluxes, approximated by hydrocarbon-like or- ganic aerosols (HOA), displayed diurnal patterns similar to CO2 fluxes and anthropogenic urban activities. Overall, 47 % of submicron organic aerosol emissions were HOA, 35 % were oxygenated (OOA) and 18 % were associated with biomass burning (BBOA). Organic aerosol fluxes were bi- directional, but on average HOA fluxes were 0.1 µg m 2 s 1 , OOA fluxes were 0.03 µg m 2 s 1 , and BBOA fluxes were 0.03 µg m 2 s 1 . After accounting for size differences (PM1 vs PM2.5) and using an estimate of the black carbon component, comparison of the flux measurements with the 2006 gridded emissions inventory of Mexico City, showed that the daily-averaged total PM emission rates were essen- tially identical for the emission inventory and the flux mea- surements. However, the emission inventory included dust and metal particulate contributions, which were not included in the flux measurements. As a result, it appears that the in- ventory underestimates overall PM emissions for this loca- tion.