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Browsing Faculty of Science by Author "62cd714662ddaefaa836cf01b296267e"
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Item Open Access Insufficient evidence for the existence of natural trifluoroacetic acid(Environmental Science: Processes & Impacts, 2021-10-01) Joudan, Shira; De Silva, Amila O.; Young, CoraTrifluoroacetic acid (TFA) is a persistent and mobile pollutant that is present ubiquitously in the environment. As a result of a few studies reporting its presence in pre-industrial samples and a purported unaccounted source, TFA is often claimed to exist naturally. Here, we examine the evidence for natural TFA by: (i) critically evaluating measurements of TFA in pre-industrial samples; (ii) examining the likelihood of TFA formation by hypothesized mechanisms; (iii) exploring other potential TFA sources to the deep ocean; and (iv) examining global budgets of TFA. We conclude that the presence of TFA in the deep ocean and lack of closed TFA budget is not sufficient evidence that TFA occurs naturally, especially without a reasonable mechanism of formation. We argue the paradigm of natural TFA should no longer be carried forward.Item Restricted Understanding sources of atmospheric hydrogen chloride in coastal spring and continental winter(ACS Publications, 2021-08-18) Angelucci, Angela A.; Furlani, Teles; Wang, Xuan; Jacob, Daniel J.; VandenBoer, Trevor; Young, CoraAmbient 0.5 Hz hydrogen chloride (HCl) measurements were made in Canadian cities to 17 investigate chlorine activation and constrain the tropospheric chlorine budget. Springtime HCl mixing ratios in a coastal city (St. John’s, NL) were up to 1200 parts per trillion by volume (pptv) with median of 63 pptv and were consistently elevated during daytime. High-time resolution measurements allowed attribution of events to general sources, including direct emissions. Most coastal HCl was related to sea salt aerosol acid displacement (R1) and chlorine activation. Continental urban (Toronto, ON) wintertime HCl mixing ratios reached up to 541 and 172 pptv, with medians of 67 and 11 pptv during two sampling periods characterized by different wind directions. The absence of consistent relationships with NOx, temperature, and wind direction, as well as a lack of diurnal patterns, suggested uncharacterized direct sources of HCl. One period with road salting occurred during sampling, but no relationship to changes in HCl observations was found. The contribution of road salt to the measured HCl may have been masked by larger contributors (such as direct sources of HCl) or perhaps the relationship between HCl and road salt application is not immediate and thus additional measurements over multiple salting events or between seasons would be required. GEOS-Chem modelled HCl temporal variations in mixing ratio agreed well with coastal measurements only. Measured mixing ratios were underestimated by the model in both locations, but to a greater degree (up to 3 orders of magnitude) in the continental city. The discrepancy between the model and measurements for the continental wintertime city emphasizes the need for greater understanding of direct sources of HCl and the impact of road salt.