Atmospheric decay distances and times for sulphur and nitrogen oxides estimated from air and precipitation monitoring in eastern Canada

Abstract

Previous estimates of residence times for sulphur species have been made mainly from the overall box budget approach by considering the various deposition and conversion terms in a "static" reservoir. This paper will use a "dynamic" approach by considering daily filter-pack and precipitation observations taken at several eastern Canadian monitoring sites over a period of several years. Some of these sites are lined up from southwest to northeast along the most frequent wind direction for pollutant transport episodes. Concentrations can thus be examined in the Lagrangian sense starting at the edge of the major North American emission region and ending at a remote site in Newfoundland over 2000 km away. Plots of concentration of the monitored species in air and precipitation against distance from the emissions region, show a good fit to an exponential curve. The decay distances, defined as the distances for the initial concentration to fall to I/e of its original value, can thus be determined. These are in air: 480 km for SO,, 1280 km for SO;, 720 km for total sulphur (SO,

Regional Transport and Urban Contributions to Fine Particle Concentrations in Southeastern Canada

“…Given the spatial resolution of the data, this estimated loss rate is reasonably consistent with results reported by Summers and Fricke 25 for decay distances of ambient SO x and NO x in eastern Canada. The expected decrease in PM 2.5 concentration from Simcoe to the southern edge of the GTA can be estimated using our typical loss rate, assuming that the GTA is three-quarters of the total distance between Simcoe and Egbert.…”

Valuing Air Quality Using the Life Satisfaction Approach

“…The new difference-in-difference term thus is P j E j 1ðscrubber Þ jt g ðD cj Þf ðR cj Þ. The distance decay is modelled as an exponential curve with an implied characteristic decay distance of 480 km, g(D cj ) ¼ exp(À2.1E À 6AED cj ), as suggested by field studies (Schwartz, 1989;Summers and Fricke, 1989). The decrease in concentration with distance captures both removal of material by deposition and dilution or dispersion caused by lateral or vertical mixing of air.…”

Rates of Wintertime Atmospheric SO2 Oxidation based on Aircraft Observations during Clear‐Sky Conditions over the Eastern United States

“…In comparison, previous studies estimated SO 2 lifetimes of 4-12 hr from point sources under summertime conditions (C. Lee et al, 2011) to as long as 14 hr (Summers & Fricke, 1989). Our measurements occur over 9 hr of transport in clear-sky conditions, during which 2.0-6.4% conversion of SO 2 to SO 4 -2 is expected, based on our rate.…”