Photochemical Modeling of Emissions Trading of Highly Reactive Volatile Organic Compounds in Houston, Texas. 2. Incorporation of Chlorine Emissions

Abstract

As part of the State Implementation Plan for attaining the National Ambient Air Quality Standard for ozone, the Texas Commission of Environmental Quality has created a Highly Reactive Volatile Organic Compounds (HRVOC) Emissions Cap and Trade Program for industrial point sources in the Houston/Galveston/Brazoria area. This series of papers examines the potential air quality impacts of this new emission trading program through photochemical modeling of potential trading scenarios; this paper examines the air quality impact of allowing facilities to trade chlorine emission reductions for HRVOC allocations on a reactivity weighted basis. The simulations indicate that trading of anthropogenic chlorine emission reductions for HRVOC allowances at a single facility or between facilities, in general, resulted in improvements in air quality. Decreases in peak 1-h averaged and 8-h averaged ozone concentrations associated with trading chlorine emissions for HRVOC allocations on a Maximum Incremental Reactivity (MIR) basis were up to 0.74 ppb (0.63%) and 0.56 ppb (0.61%), respectively. Air quality metrics based on population exposure decreased by up to 3.3% and 4.1% for 1-h and 8-h averaged concentrations. These changes are small compared to the maximum changes in ozone concentrations due to the VOC emissions from these sources (5-10 ppb for 8-h averages; up to 30 ppb for 1-h averages) and the chlorine emissions from the sources (5-10 ppb for maximum concentrations over wide areas and up to 70 ppb in localized areas). The simulations indicate that the inclusion of chlorine emissions in the trading program is likely to be beneficial to air quality and is unlikely to cause localized increases in ozone concentrations ("hot spots").

Chlorine chemistry in urban atmospheres: a review

“…This same study also found a maximum increase during morning hours, at the times of maximum rates of Cl 2 and HOCl photolysis, of 45 ppbv. [96,97] Because some of the peak enhancements of ozone concentrations predicted in these models are highly localised near chlorine radical precursor sources, the maximum predictions of the models are very sensitive to the grid cell dimensions used in the work. Wang et al [96,97] used a nested grid with horizontal spatial resolutions as small as 4 km.…”

“…[96,97] Because some of the peak enhancements of ozone concentrations predicted in these models are highly localised near chlorine radical precursor sources, the maximum predictions of the models are very sensitive to the grid cell dimensions used in the work. Wang et al [96,97] used a nested grid with horizontal spatial resolutions as small as 4 km. In similar work, but with horizontal grid cell dimensions of 12-36 km, Sarwar and Bhave [98] modelled the effect of chlorine chemistry on ozone levels over the eastern half of the United States.…”

“…Previous regional modelling studies of this mechanism used limited, and typically fixed, parameter values. [91,92] One recent study [94] has implemented parameterisations [46,54,55] which account for influences from particulate species such as H 2 O and NO 3 À for continental-scale modelling [24] Houston, Texas Yes 36, 12, 4 16 CMBO 59 [71] Houston, Texas Yes 36, 12, 4 72 CMBO 100 [7] Houston, Texas Yes 36, 12, 4 48 -- [96,97] Eastern USA Yes 36, 12 12 -- [98] SOCAB …”

Inland Concentrations of Cl2 and ClNO2 in Southeast Texas Suggest Chlorine Chemistry Significantly Contributes to Atmospheric Reactivity

“…Research over the past several decades has shown that the presence of reactive gas phase chlorine species, particularly chlorine radicals (Cl • ), can contribute significantly to atmospheric reactivity [1][2][3][4][5][6][7]. High concentrations of Cl • can lead to increased rates of Volatile Organic Compound (VOC) oxidation [8][9][10][11][12][13] and enhanced rates of O3 production in the troposphere [1,3,7,[14][15][16].…”

Source Profiles and Chemical Reactivity of Volatile Organic Compounds from Solvent Use in Shanghai, China

“…These VOCs from solvent use result in heavy indoor air pollution (Celebi and Vardar, 2008;Dales et al, 2008;Kim et al, 2012), and especially, 18-40% of them are hazardous and harmful to human health (Wei et al, 2008(Wei et al, , 2009. Additionally, most VOC species emitted from solvent use are very chemically reactive, and hence play an important role in the formation of tropospheric ozone and fine particles (Derwent et al, 2007;Wang et al, 2007).…”