Air Pollution Processing by Radiation Fogs
Air Pollution Processing by Radiation Fogs
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DOI：
10.1007/s11270-006-9276-x
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发表时间：
2007-05
期刊：
影响因子：
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通讯作者：
P. Herckes;Hui-qing Chang;Taehyoung Lee;J. Collett
中科院分区：
文献类型：
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作者：
P. Herckes;Hui-qing Chang;Taehyoung Lee;J. Collett
2000/2001年冬季，加州圣华金河谷出现了几次雾。测量结果表明，雾一般不到50米深，但含有高液态水含量（经常超过200毫克/立方米）和大水滴。雾水的成分主要是铵（中位浓度= 608 μN），硝酸盐（304 μN）和有机碳（6.9 ppmC），亚硝酸盐（18 μN）和硫酸盐（56 μN）也有显着的贡献。主要有机物质包括甲酸盐（中位浓度= 32 μN）、乙酸盐（31 μN）和甲醛（21 μM）。高浓度的氨导致高雾的pH值，在核心测量站点范围在5.8和8.0之间。在这种高pH值的水相中，溶解的二氧化硫的氧化和S（IV）与甲醛反应形成羟基甲磺酸盐都是重要的过程。雾也可以有效地清除和去除空气中的颗粒物。雾中关键溶质的沉积速度通常为1- 2cm/s的量级，远高于前体累积模式气溶胶颗粒的沉积速度。观察到单个组分的沉积速度变化，顺序为NO2−>雾水> NH 4 +> TOC> SO 42 −> NO3−。亚硝酸盐，观察到富集在大雾滴，有一个沉积速度高于平均fogwater沉积速度，由于增加下降沉降速度与大小。在小雾滴中富集的物种（NH 4+、TOC、SO 42-和NO3-）的沉积速度都小于在雾水中观察到的沉积速度。据估计，主要雾溶质物种的典型边界层去除率约为0.5-1 μg m− 3 h −1，表明区域雾在降低空气污染物浓度方面可以发挥重要作用。
Several fog episodes occurred in California’s San Joaquin Valley during winter 2000/2001. Measurements revealed the fogs to generally be less than 50 m deep, but to contain high liquid water contents (frequently exceeding 200 mg/m3) and large droplets. The composition of the fog water was dominated by ammonium (median concentration = 608 μN), nitrate (304 μN), and organic carbon (6.9 ppmC), with significant contributions also from nitrite (18 μN) and sulfate (56 μN). Principal organic species included formate (median concentration = 32 μN), acetate (31 μN), and formaldehyde (21 μM). High concentrations of ammonia resulted in high fog pH values, ranging between 5.8 and 8.0 at the core measurement site. At this high pH aqueous phase oxidation of dissolved sulfur dioxide and reaction of S(IV) with formaldehyde to form hydroxymethanesulfonate are both important processes. The fogs are also effective at scavenging and removal of airborne particulate matter. Deposition velocities for key solutes in the fog are typically of the order of 1–2 cm/s, much higher than deposition velocities of precursor accumulation mode aerosol particles. Variations were observed in deposition velocities for individual constituents in the order NO2−> fogwater > NH4+> TOC ∼ SO42−> NO3−. Nitrite, observed to be enriched in large fog drops, had a deposition velocity higher than the average fogwater deposition velocity, due to the increase in drop settling velocity with size. Species enriched in small fog drops (NH4+, TOC, SO42−, and NO3−) all had deposition velocities smaller than observed for fogwater. Typical boundary layer removal rates for major fog solute species were estimated to be approximately 0.5–1 μg m−3h−1, indicating the important role regional fogs can play in reducing airborne pollutant concentrations.