Characterization of ozone production in San Antonio, Texas, using measurements of total peroxy radicals

Abstract

Abstract. Observations of total peroxy radical concentrations ([XO2] ≡ [RO2] + [HO2]) made by the Ethane CHemical AMPlifier (ECHAMP) and concomitant observations of additional trace gases made on board the Aerodyne Mobile Laboratory (AML) during May 2017 were used to characterize ozone production at three sites in the San Antonio, Texas, region. Median daytime [O3] was 48 ppbv at the site downwind of central San Antonio. Higher concentrations of NO and XO2 at the downwind site also led to median daytime ozone production rates (P(O3)) of 4.2 ppbv h−1, a factor of 2 higher than at the two upwind sites. The 95th percentile of P(O3) at the upwind site was 15.1 ppbv h−1, significantly lower than values observed in Houston. In situ observations, as well as satellite retrievals of HCHO and NO2, suggest that the region was predominantly NOx-limited. Only approximately 20 % of observations were in the VOC-limited regime, predominantly before 11:00 EST, when ozone production was low. Biogenic volatile organic compounds (VOCs) comprised 55 % of total OH reactivity at the downwind site, with alkanes and non-biogenic alkenes responsible for less than 10 % of total OH reactivity in the afternoon, when ozone production was highest. To control ozone formation rates at the three study sites effectively, policy efforts should be directed at reducing NOx emissions. Observations in the urban center of San Antonio are needed to determine whether this policy is true for the entire region.

An in situ gas chromatograph with automatic detector switching between PTR- and EI-TOF-MS: isomer-resolved measurements of indoor air

“…Indoors, sources of PDMS are numerous: paints, coatings, sealants, textiles, and electronics (Andriot et al, 2007). Particularly relevant is their use in paints, where PDMS are used as the binder (30 % w/w-100 % w/w of the mixture) and as additives (0.1 % w/w-5 % w/w of the mixture), depending on the product and manufacturer (Andriot et al, 2007). Another significant component of paints are inorganic minerals, used as pigments and extenders, constituting 20 %-50 % of the paint mixture (Karakaş et al, 2010).…”

Ground-based Investigation of HO<sub>x</sub> and Ozone Chemistry in Biomass Burning Plumes in Rural Idaho

“…ECHAMP was stationed within the minAML and sampled on a 2-minute time base. The sampling and calibration methods have been described in detail elsewhere (Anderson et al, 2019;Wood et al, 2017) and only a brief summary including details specific to the McCall deployment is described here.…”

“…Dilution also dries the sampled air leading to lower and less variable relative humidity. This is beneficial as the amplification factor decreases with increasing RH (Anderson et al, 2019;Wood et al, 2017). The humidity-dependence of the amplification factor is due to humidity dependent reactions of HO2 and the HO2-H2O adduct reacting with NO to form HNO3 (Reichert et al, 2003;Butkovskaya et al, 2009) and HO2 wall losses (Mihele and Hastie, 1998;Reichert et al, 2003).…”

“…ECHAMP was calibrated to the methyl peroxy radical CH3O2 over a range of relative humidities (RH) using the CH3I photolysis method as described in Anderson et al (2019) six times at McCall. The calibrant was prepared by mixing humidified ZA with trace amounts of CH3I from a permeation source.…”

Airborne measurement of peroxy radicals using chemical amplification coupled with cavity ring-down spectroscopy: the PeRCEAS instrument

“…In the last decades, ground-based measurements of RO * 2 and HO 2 have been successfully made in a variety of environments (Monks et al, 1998(Monks et al, , 2009 and references herein; Burkert et al, 2001a, b;Carslaw et al, 2002;Fleming et al, 2006a, b;Emmerson et al, 2007;Qui et al, 2007;Kanaya et al, 2007Kanaya et al, , 2012Hofzumahaus et al, 2009;Andrés-Hernández et al, 2009Mao et al, 2010;Kukui et al, 2014;Lelieveld et al, 2018;Tan et al, 2017). The majority of measurements of RO * 2 or HO 2 were made in field campaigns which studied different aspects of the chemistry in the lower troposphere.…”