Sunday, 22 January 2017
4E (Washington State Convention Center )
Air quality models are used to predict the formation of atmospheric pollutants such as tropospheric ozone, which is deleterious to human health. Globally, forest canopies contribute the majority of non-methane volatile organic compounds (VOC), many of lead to the formation of ozone through reactions with nitrous oxide (NOx) emissions from automobiles. Isoprene and its reaction products methyl-vinyl-ketone (MVK) and methacrolein (MACR) comprise the majority of hydrocarbon mass in deciduous forest canopies and are thus important in accurately predicting ozone formation. However, because a myriad of organic compounds and chemical reactions occur in the atmosphere, air quality models are innately simplified and BVOC emissions are estimated from measurements made at the foliage level, ignoring inter-canopy chemistry. How potentially different are these rough estimations of isoprene from actual fluxes for varying vertical profiles of ozone and NOx concentrations and foliage density? To answer this question various simulations were ran on the 1-D column forest canopy model ACCESS. Atmospheric vertical profiles were created for five levels of ozone and NOx based on field measurements at varying heights in the canopy. Foliage vertical profiles were based on the typical range of leaf area index in deciduous forests. Flux outputs for isoprene, MVK, and MACR were divided by the isoprene fluxes for the medium ozone and NOx simulations, forming correction factors that can be eventually applied to increase the the accuracy of ozone forecasts. We observed that these correction factors were dependent on the foliage and atmospheric vertical profiles and differed between simulations.
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