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PM data analysis—a comparison of two urban areas: Fresno and Atlanta

机译：PM数据分析-弗雷斯诺和亚特兰大两个市区的比较

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Urban speciated fine particulate data from the Speciation Trends Network from January 2001 to February 2002 were studied in both eastern and western locations of the United States. The seasonal variability of PM_(2.5) mass, organic carbon, elemental carbon, sulfate ion, nitrate ion, and ammonium cation concentrations were analyzed. Their relationships with ozone and meteorology were also examined. The results reveal that differences in meteorology and emissions have a significant impact on the observed seasonality in species concentrations in Fresno and Atlanta. Based on a parallel analysis of regional PM_(2.5) episodic events, this influence appears to be general and may typify the difference between eastern and western cities in the United States. In Atlanta, ozone, sulfate, and ammonium were high in the summer when temperatures and humidities were high, whereas organic carbon concentrations were relatively flat year-round. In Fresno, however, ozone concentrations were high but sulfate concentrations were very low even in the summer, whereas PM_(2.5) concentrations were much higher in the winter and dominated by organics. Meteorologically, in Fresno, it was hot and dry in the summer but cool and humid in the winter. Organic carbon, nitrate, and ammonium ion concentrations were observed to be the highest in late fall and winter when the average relative humidity was the highest (above ～60%). Much lower mixing heights and frequent stagnations in the winter in Fresno were the major factors influencing the observed high concentrations of various species. The wintertime organic aerosols in Fresno were predominately primary in origin. However, on some very high organic concentration days, up to 30% of the observed organic aerosols could be attributed to secondary organic aerosols (SOAs). These very high organic aerosol concentration days in the winter typically had mild temperatures, high humidities, low dilution rates, and an abundance of nitrate particles. These conditions were favorable for additional SOA formation through the acid catalyzed heterogeneous reactions at night on top of the already high primary organic emissions.
机译：在2001年1月至2002年2月期间，在美国东部和西部地区研究了“物种形成趋势网络”中城市指定的细颗粒数据。分析了PM_（2.5）质量，有机碳，元素碳，硫酸根离子，硝酸根离子和铵阳离子浓度的季节性变化。还检查了它们与臭氧和气象学的关系。结果表明，气象和排放方面的差异对在弗雷斯诺和亚特兰大的物种浓度观测到的季节性具有重大影响。基于对区域PM_（2.5）突发事件的并行分析，这种影响似乎很普遍，可能代表了美国东西部城市之间的差异。在亚特兰大，夏季的温度，湿度较高，而臭氧，硫酸盐和铵的含量较高，而全年的有机碳浓度相对较低。然而，在弗雷斯诺，即使在夏季，臭氧浓度也很高，但硫酸盐浓度却很低，而冬季的PM_（2.5）浓度则高得多，并且以有机物为主。在气象上，在弗雷斯诺，夏季炎热干燥，而冬季凉爽潮湿。当平均相对湿度最高时（约60％以上），在秋末和冬季，有机碳，硝酸盐和铵离子的浓度最高。弗雷斯诺冬季的低得多的混合高度和频繁的停滞是影响观察到的各种物种高浓度的主要因素。弗雷斯诺的冬季有机气溶胶主要是起源。但是，在某些有机物浓度很高的日子，观察到的多达30％的有机气溶胶可归因于次生有机气溶胶（SOA）。在冬季，这些有机气溶胶浓度很高的日子通常具有温和的温度，高湿度，低稀释率和大量的硝酸盐颗粒。这些条件有利于在夜间已经发生的初级有机物排放量较高的情况下通过酸催化的异质反应进一步形成SOA。

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