Variations of nanoparticle concentrations at the Fresno Supersite.
Variations of nanoparticle concentrations at the Fresno Supersite.
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DOI：
10.1016/j.scitotenv.2005.04.046
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发表时间：
2006-04
期刊：
影响因子：
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通讯作者：
J. Watson;J. Chow;D. Lowenthal;N. Kreisberg;S. Hering;M. Stolzenburg
中科院分区：
文献类型：
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作者：
J. Watson;J. Chow;D. Lowenthal;N. Kreisberg;S. Hering;M. Stolzenburg
2002年8月25日至2003年7月31日，在加利福尼亚州弗雷斯诺市的Supersite测量了3 nm至2 μm的粒径分布。在50 ~ 1000 μm2cm−3范围内，纳米颗粒（3 ~ 10 nm）浓度和纳米颗粒与总颗粒浓度之比与颗粒表面积呈负相关。纳米颗粒浓度升高与机动车排放和光化学颗粒产生有关。与亚特兰大相比，在乔治亚州，光化学衍生的纳米颗粒浓度超过105cm - 3，弗雷斯诺的5分钟平均纳米颗粒浓度从未超过24,400 cm - 3。虽然在弗雷斯诺发生了光化学颗粒的产生，但没有观察到新颗粒产生的证据（即，在10 nm以下，随着尺寸的减小，数量浓度增加）。这表明光化学颗粒的产生可能发生在更高的海拔，然后混合到地面，或者新鲜颗粒的产生速度相对于凝固的损失率比在亚特兰大要小。与亚特兰大相比，弗雷斯诺较低的产量与硫前体浓度较低和相对湿度较低更为一致。
Particle size distributions from 3 nm to 2 μm were measured at the Fresno, CA, Supersite from August 25, 2002 through July 31, 2003. Nanoparticle (3–10 nm) concentrations and the ratio of nanoparticle to total particle concentration were inversely related to particle surface areas from 50 to 1000 μm2cm−3. Elevated nanoparticle concentrations were associated with motor vehicle emissions and with photochemical particle production. In contrast with Atlanta, GA, where concentrations of photochemically derived nanoparticles exceeded 105cm−3, 5-min average nanoparticle concentrations in Fresno never exceeded 24,400 cm−3. While photochemical particle production occurs in Fresno, evidence of new particle production (i.e., an increase in number concentration with decreasing size below 10 nm) was not observed. This suggests that photochemical particle production may have occurred at a higher altitude followed by mixing to the surface, or that the fresh particle production rate was smaller with respect to the loss rate by coagulation than it was in Atlanta. Lower production rates in Fresno are more consistent with lower concentrations of sulfur precurors and low relative humidity in Fresno than they are in Atlanta.