Observations of nitrogen dioxide, total peroxy nitrates, total alkyl nitrates, and nitric acid in the mid-sierras and Sacramento plume using thermal dissociation - laser induced fluorescence.

摘要

Nitrogen oxide radicals (NO_x ≡ NO + NO₂) control the rate of tropospheric ozone production and affect particle formation through production of HNO₃ and organic nitrates. The chemistry affecting the fate of NO_x while extensively studied in the laboratory, remains poorly documented in the atmosphere because of the difficulty of making simultaneous observations of NO_x and NO_x reaction products. Furthermore, it has been difficult to obtain such observations under conditions where chemistry occurs in a well understood transport regime. In Chapter 2 of this dissertation, I describe development of a new experimental technique, thermal dissociation-laser induced fluorescence (TD-LIF), capable of observing NO₂, ΣPNs, ΣANs, and HNO₃, and its applications to field measurements. The instrument's capabilities to measure HNO₃ and ΣANs are unique. Also, as a result of progress that has been made at simplifying maintenance, it has a unique capacity to obtain long term records.; In Chapters 3 and 4, I describe nearly continuous measurements of NO₂, total peroxy nitrates (ΣPNs), total alkyl nitrates (ΣANs), and HNO₃ which were made from October 2000 to February 2002 at the University of California Research Station (UC-BFRS). ΣANs were observed to routinely comprise 10–20% of NO_y, a much larger fraction than previously reported (typically 1–3%). In contrast to prior observations that suggested ΣANs are negligible, I demonstrate here that large abundances of ΣANs are consistent with simple chemical models of tropospheric ozone production and with the few prior comprehensive model studies. ΣANs were strongly correlated with O₃ at the UC-BFRS. I illustrate how ΣANs production is directly linked to the HO_x/NO_x ozone production cycles. ΣANs were observed at similar concentrations (200–800 ppt), with a similar seasonal cycle (summer peak), and similar correlations with photochemical parameters (O ₃, peroxy nitrates) to previous reports of ‘missing NO_y’ at non-urban, mid-latitude continental sites. Comparison of the sum NO _y as measured by TD-LIF (ΣNO_yi) to observations of total NO_y as measured by the catalysis chemiluminesence method showed good agreement. Observations of ΣANs at Granite Bay, California and La Porte, Texas also provide consistent insights, leading to the conclusion that ΣANs are most, if not all, of the ‘missing NO_y’.; In Chapter 4, I describe and analyze the seasonal and diurnal cycles of ΣNO_yi, NO_x, ΣPNs, ΣANs, HNO ₃, CO, and O₃ observed at the UC-BFRS. The seasonal cycles (most peaked in summer) are attributed to a combination of changes in transport and chemical processing. (Abstract shortened by UMI.)