During the MILAGRO campaign, March 2006, eight-stage cut impactors were used to sample atmospheric particles at Tecámac (T1 supersite), towards the northeast edge of the Mexico City Metropolitan Area, collecting fresh local emissions and aged pollutants produced in Mexico City. Particle samples were analyzed to determine total mass concentrations of Ca2+, Mg2+, NH4+, K+, Cl−, SO42−, and NO3−. Average concentrations were 22.1 ± 7.2 μg m−3 for PM10 and 18.3 ± 6.2 μg m−3 for PM1.8. A good correlation between PM10 and PM1.8, without influence from wind patterns, indicates that local emissions are more important than the city’s pollution transported to the site, despite the fact that Tecámac is just 40 km away from Mexico City. A lack of diurnal patterns in the PM2.5/PM1.8 ratio supports this conclusion. The inorganic composition of particles suggests that vehicles, soil resuspension, and industries are the main pollutant sources. Finally, the particles were found to be neutralized, in agreement with observations in the Mexico City Metropolitan Area.

中文翻译：

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来自墨西哥城郊区的大小不同的大气颗粒的水溶性无机离子

在 MILAGRO 活动期间，2006 年 3 月，在墨西哥城大都市区东北边缘的 Tecámac（T1 超级站点）使用八级切割撞击器对大气颗粒进行采样，收集墨西哥城产生的新鲜当地排放物和老化污染物。分析颗粒样品以确定 Ca2+、Mg2+、NH4+、K+、Cl-、SO42- 和 NO3- 的总质量浓度。PM10 的平均浓度为 22.1 ± 7.2 μg m-3，PM1.8 的平均浓度为 18.3 ± 6.2 μg m-3。PM10 和 PM1.8 之间存在良好的相关性，不受风力模式的影响，这表明当地排放比运输到现场的城市污染更重要，尽管 Tecámac 距离墨西哥城仅 40 公里。PM2.5/PM1.8 比率缺乏昼夜模式支持这一结论。颗粒的无机成分表明车辆、土壤再悬浮和工业是主要的污染源。最后，发现这些粒子被中和了，这与墨西哥城大都市区的观察结果一致。