Abstract. As criteria pollutants from anthropogenic emissions have declined in the US in the last two decades, biomass burning (BB) emissions are becoming more important for urban air quality. Tracking the transported BB emissions and their impacts is challenging, especially in areas that are also burdened by anthropogenic sources like the Texas Gulf coast. During the Corpus Christi and San Antonio (CCSA) field campaign in Spring 2021, two long-range transport BB events (BB1 and BB2) were identified. The observed patterns of absorption Ångström Exponent (AAE), high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) BB tracer (f60), equivalent black carbon (eBC), acetonitrile and carbon monoxide (CO) during BB1 and BB2 indicated differences in the mixing of transported BB plumes with local anthropogenic sources. The combined information from HYSPLIT backward trajectory (BTs) and satellite observations revealed that BB1 had mixed influence of transported smoke plumes from fires in Central Mexico, the Yucatan peninsula, and the Central US, whereas BB2 was influenced majorly by fires in the Central US. The estimated transport time of smoke from the Mexican fires and the Central US fires to our study site were not too different (48–54 hours and 24–36 hours, respectively) and both events appeared to have undergone similar levels of atmospheric processing, as evident in the elemental ratios of bulk organic aerosol (OA). We observed a progression of f44 vs. f60 as a function of time elapsed during BB2. Positive matrix factorization (PMF) analysis of OA showed that BB1 had a mixture of organics from aged BB emission with an anthropogenic marine signal while the oxidized organic compounds from aged BB emissions dominated the aerosols during BB2. While aerosol measurements exhibited good agreement with respect to the BB designation, the CO and acetonitrile trends revealed more complicated source contributions. Our analysis from mobile and stationary measurements highlights that both CO and acetonitrile are likely impacted by local sources even during the BB events and specifically that acetonitrile cannot be used as a unique BB tracer for dilute BB plumes in an industrially influenced location. Finally, we provide evidence of the potential regional impacts of these transported BB events on urban O3 levels using measurements from the surface air quality monitoring network in Texas.
<p>As the Arctic continues to change and warm rapidly, it is increasingly important to understand the contribution of biogenic sources to Arctic aerosol. Biogenic sources of primary and secondary aerosol in the arctic will be impacted by climate change, including warming and earlier snow and ice melt, while local emissions and long-range transport can drive changes in anthropogenic aerosol. This study focuses on identifying the contribution of biogenic aerosol to organic carbon (OC) and its seasonal trends through the analysis of aerosol chemical and isotopic composition. Aerosol samples were collected at two sites on the North Slope of Alaska (Utqia&#289;vik and Oliktok Point) over the summer of 2015 and from June 2016 through August 2017. Organic carbon concentrations correlated well between the sites with high contribution from contemporary sources. Backwards air mass trajectory analysis indicates that source regions are primarily marine in the summertime. Methanesulfonic acid (MSA) was utilized to confirm this marine influence. Secondary organic aerosol confirmed the contribution of terrestrial biogenic sources to organic aerosol at both sites. Strong correlations between ambient temperature and MSA and OC were found during the summer. This study provides a multiyear characterization of organic carbon highlighting the high biogenic influence and indicating areas of interest for future research.</p>
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