Abstract
Measurements of the atmospheric mixing ratios of ozone, peroxyacetylnitrate (PAN), hydrocarbons, and alkyl nitrates were made in a boreal forest ecosystem in the interior of Alaska from March 15 to May 14, 1993. During this period the mixing ratios of PAN, alkyl nitrates, and nonmethane hydrocarbons (NMHCs) generally decreased due to the influence of both meteorology and OH removal. Mean mixing ratios of ozone, PAN, C2 ‐ C6 alkyl nitrates, and total C2 ‐ C5 NMHC during southerly flow periods were 24.4 parts per billion (ppbv), 132.1 parts per trillion (pptv ), 34 pptv, and 8.2 ppbCv, respectively. During a short period of northerly flow, mixing ratios of PAN and total NMHC were approximately 2 times the southerly flow mixing ratios. PAN is correlated with ozone, and alkyl nitrates are correlated with alkanes. PAN and ozone mixing ratios exhibit similar diurnal variations on a number of days with an early morning minimum and afternoon maximum. This is likely due to a diurnal cycle in the boundary layer ‐ free troposphere exchange and loss processes in the boundary layer for both O3 and PAN. Higher molecular weight (mw) hydrocarbons and alkyl nitrates are observed to decrease more quickly than the lower mw hydrocarbons, consistent with removal by OH as the primary loss process.
Highlights
Introduction the highArctic [Bottenheimet al., 1993;Muttmramu et aL, 1994]
Isopentaneis theretbrenot includedin the sum of NMHC
ThemaximumPAN mixingratioobserved at PokerFlat on day 83 (315 pptv) was significantlylmver
Summary
Elevatedlevelsot'bothgasesand aerosolsin colmectionwith airflow fi"omthe Arctic and possiblelong-rangetransportkolnEurasiansources(in winter and spring)havebeenreportedpreviously[e.g., Raatz and. West Territories,during the same season[dobsonet al., 1. The researchsite is locatedon a ridge,300 m abovethe 1994b],butPAN mixingratiosaresignificantllymver. A DasibiUV-analyzer(model1003- After day 125 until the endof the campaignh, ighermoPC) was usedto measureozonemixingratioscontinuously. Lecularweight alkaneand unsaturatedhydrocarbonmixing A multipointcalibratiown ascarriedout bytitrationofozone with a NIST traceableNO standard(Scott-Mamn). A gas 400 chromatograpwhith elecroncapturedetecto(rGC-ECD)was usedfor thePAN measurementsS. Amples(,1 mL) wereauto- 3oo maticallyinjectedevery 15 min ontoa 30-m, 0.53-mm ID - 200 capillarycolumnwitha stationarpyhaseofDB-210. ContainingPAN in tridecane.The standardwasreferenced 0 o against the NO standard,using a chemiluminescence 2O. By CO in a 300øCcatalyticgoldconverte[rBollrogeret al., 1983]. The precisionof the measurementdse, terminedby z propagatioonf error,was11%and2.5% tbrPAN andozone, respectivelyA.
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