Summertime distribution of PAN and other reactive nitrogen species in the northern high‐latitude atmosphere of eastern Canada

Abstract

Aircraft measurements of key reactive nitrogen species (NO, NO2, HNO3, PAN, PPN, NO3‐, NOy), C1 to C6 hydrocarbons, acetone, O3, chemical tracers (C2Cl4 CO), and important meteorological parameters were performed over eastern Canada during July to August 1990 at altitudes between 0 and 6 km as part of an Arctic Boundary Layer Expedition (ABLE3B). In the free troposphere, PAN was found to be the single most abundant reactive nitrogen species constituting a major fraction of NOy and was significantly more abundant than NOx and HNO3. PAN and O3 were well correlated both in their fine and gross structures. Compared to data previously collected in the Arctic/subarctic atmosphere over Alaska (ABLE3A), the lower troposphere (0–4 km) over eastern Canada was found to contain larger reactive nitrogen and anthropogenic tracer concentrations. At higher altitudes (4–6 km) the atmospheric composition was in many ways similar to what was seen over Alaska and supports the view that a large‐scale reservoir of PAN (and NOy) is present in the upper troposphere over the entire Arctic/subarctic region. The reactive nitrogen budget based on missions conducted from the North Bay site (missions 2–10) showed a small shortfall, whereas the budget for data collected from the Goose Bay operation (missions 11–19) showed essential balance. It is calculated that 15–20 ppt of the observed NOx may find its source from the available PAN reservoir. Meteorological considerations as well as relationships between reactive nitrogen and tracer species suggest that the atmosphere over eastern Canada during summer is greatly influenced by forest fires and transported industrial pollution.

Studies of Peroxyacetyl nitrate (PAN) and its interaction with the snowpack at Summit, Greenland

“…The sum of PAN and NO x frequently accounted for all the NO y , within the measurement uncertainty, as shown in Figure 4a. The 1999 PAN/NO y ratios were comparable to those observed by Singh et al [1992, 1994].…”

Interactive chemistry in the Laboratoire de Météorologie Dynamique general circulation model: model description and impact analysis of biogenic hydrocarbons on tropospheric chemistry

“…It generally also reproduces the acetone mixing ratios observed in the Asian outflow during PEM-WEST B, but significantly overestimates acetone at the near continental sites measured during the SONEX campaign. However, acetone profiles calculated by LMDz-INCA do agree quite well with observations obtained during the ABLE-3B (Singh et al, 1994a) experiments. The observations gathered during PEM-Tropics B indicate surprisingly large abundances of acetone over the tropical Pacific (Singh et al, 2001), a region where most models previously predicted quite low concentrations (cf., e.g.…”

Interaction of HNO3 with water‐ice surfaces at temperatures of the free troposphere

“…Nitric acid is an important reservoir molecule for NO x species, and its abundance thus affects the overall ability of the troposphere to photochemically generate ozone. In addition, these studies are also related to the ability of snow particles in the lower atmosphere to scavenge nitric acid and to deposit it to the ground as This HNO3 uptake is equivalent to a scavenging capacity of between 5 and 5000 pptv HNO3, at an altitude of 10 km at 230 K. By comparison, a value of 100 pptv of gas phase HNO3 in the free troposphere is not uncommon [Singh et al, 1994]. Thus, this implies that gas-phase HNO 3 could be entirely scavenged by high surface-area cirrus but not by low surface-area clouds, such as the subvisible cirrus.…”