Controls on urban ozone production rate as indicated by formaldehyde oxidation rate and nitric oxide

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• 作者：Robert B. Chatfield ; Xinrong Ren ; William Brune ; James Schwab ; Queens College ; PMTACS Measurement Teams
• 关键词：Tropospheric ozone ; Smog ; Ozone abatement ; Atmospheric chemical mechanisms ; New York City
• 刊名：Atmospheric Environment
• 出版年：2010
• 出版时间：December 2010
• 年：2010
• 卷：44
• 期：40
• 页码：5395-5406
• 全文大小：3334 K

文摘

Several strong statistical relationships quantifying local ozone generation are found which use only easily measured variables: nitrogen oxides (NO_x), formaldehyde (HCHO), its photolysis (i.e., UV), and temperature (T). A parameterized regression developed for rural air was adapted to central Queens, New York City, i.e., considerable fresh emissions. Measurements of the radicals [HO₂] and [OH] were available. These provided explicit reference estimates of the predominant terms for chemical ozone production, P_o(O₃) = k[HO₂][NO], of the predominant chemical loss of nitrogen oxides, L(NO₂) = k[OH][NO₂], and also their ratio. (This is termed a production efficiency for O₃.) Chemical modeling supports a robust extension from P_o(O₃) to total chemical production, P(O₃). The two regression variables, [NO] and j_HCHOrads × [HCHO], which best explain P_o(O₃), have low correlation, R  0.2 (variable, interacting urban plumelets?). In our analysis, R² for P_o(O₃) (and an estimate for its rate-determining [HO₂]) was in the range 0.48–0.81.

Signally, the method suggests a quantitative and very local application of descriptions of “VOC limitation” or “NO_x limitation” to P(O₃) and L(NO₂), expressed as dimensionless sensitivity variables. Unexpected sources, transport, or chemistry may be highlighted using only HCHO, NO_x, and UV radiation. More complex relationships are needed in a focused analysis of intermediate polluted situations, where timescales or individual sources may give trouble. Here, we find that T is informative, and cooperates with j × [HCHO] in defining [HO₂]. Sensitivities for radicals and NO for P_o(O₃) are similar 0.4, but sensitivities for radicals and NO₂ for L(NO₂) emphasize NO₂. Remaining variability in the statistical estimates of P_o(O₃) and L(NO₂) is modulated by incompletely understood, slowly varying gain factors. Understanding of these gain factors promises a better empirical indicator for P_o(O₃)/L(NO₂). Complete 3-d simulations are not replaced, but this view helps separate sub-problems in the estimation of HO₂ and P(O₃).