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Anthropogenic NO_xemissions have observable impacts on naturally occurring chemical processes in remote areas hundreds of kilometers downwind. 

Near-surface tropospheric ozone depletion events (ODEs) occur in the polar regions during springtime when ozone reacts with bromine radicals, driving tropospheric ozone mole ratios below 15 ppb (part-per-billion; nmol mol−1). ODEs alter atmospheric oxidative capacity by influencing halogen radical recycling mechanisms and the photochemical production of hydroxyl radicals (˙OH). Herein, we examined five years of continuous ozone measurements at two coastal Arctic sites: Utqiaġvik, Alaska and ∼260 km southeast at Oliktok Point, within the North Slope of Alaska oil fields. These data informed seasonal ozone trends, springtime ozone depletion, and the influence of oil field combustion emissions. Ozone depletion occurred frequently during spring: 35% of the time at Utqiaġvik and 40% at Oliktok Point. ODEs often occurred concurrently at both sites (40–92% of observed ODEs per year), supporting spatially widespread ozone depletion. Observed ozone depletion timescales are consistent with transport of ozone-depleted air masses, suggesting regional active bromine chemistry. Local-scale ozone depletion affecting individual sites occurred less frequently. Ozone depletion typically coincided with calm winds and had no clear dependence on temperature. Consistently lower ozone mole ratios year-round at Oliktok Point, compared to Utqiaġvik, indicate local-scale ozone titration within the stable boundary layer by nitric oxide (NO˙) combustion emissions in the Arctic oil fields. Oxidation of combustion-derived volatile organic compounds in the presence of NOx also likely contributes to ozone formation downwind, for example at Utqiaġvik, pointing to complex local and regional impacts of combustion emissions as Arctic anthropogenic activity increases. 

The rapidly warming Arctic has transitioned to thinner sea ice which fractures, producing leads. Few studies have investigated Arctic sea spray aerosol (SSA) produced from open ocean, leads, and melt ponds, which vary in salinity and organic and microbial community composition. A marine aerosol reference tank was deployed aboard an icebreaker to the Arctic Ocean during August–September 2018 to study SSA generated from locally collected surface waters. Aerosol generation experiments were carried out using water collected from the marginal ice zone, a human-made hole in sea ice near the North Pole, and both lead and melt pond water during an ice floe drift period. Salinity, chlorophyll a, organic carbon, nitrogen, and microbial community composition were measured. Eukaryotic plankton and bacterial abundance were elevated in experimental water from the marginal ice zone, but the relative contributions from major eukaryotic taxonomic groups varied little across the experiments. The chemical composition of individual SSA particles was analyzed using Raman microspectroscopy and computer-controlled scanning electron microscopy with energy-dispersive X-ray spectroscopy. Individual sea salt aerosol, primary organic aerosol, and mineral dust particles were observed. Sea salt aerosol constituted 44–95% of individual submicrometer and 68–100% of supermicrometer particles, by number, generated during each experiment. Carbon was detected in 85%, by number, of the individual sea salt particles, with visible organic coatings. Carbohydrates were detected in 72% of particles, by number, with smaller contributions from long-chain fatty acids (13%) and siliceous material (15%). SSA generated from melt pond water contained only long-chain fatty acids and siliceous material. Quantification of the ice-nucleating activity showed that locally produced SSA may define the High Arctic background ice-nucleating particle population, but cannot account for the peak atmospheric concentrations observed. As the Arctic warms, the increasing SSA emissions have a complex dependence on changing biological and physical processes. 

The prevailing view for aqueous secondary aerosol formation is that it occurs in clouds and fogs, owing to the large liquid water content compared to minute levels in fine particles. Our research indicates that this view may need reevaluation due to enhancements in aqueous reactions in highly concentrated small particles. Here, we show that low temperature can play a role through a unique effect on particle pH that can substantially modulate secondary aerosol formation. Marked increases in hydroxymethanesulfonate observed under extreme cold in Fairbanks, Alaska, demonstrate the effect. These findings provide insight on aqueous chemistry in fine particles under cold conditions expanding possible regions of secondary aerosol formation that are pH dependent beyond conditions of high liquid water. 

Abstract. Reactive halogen chemistry in the springtime Arctic causes ozone depletion events and alters the rate of pollution processing. There are still many uncertainties regarding this chemistry, including the multiphase recycling of halogens and how sea ice impacts the source strength of reactive bromine. Adding to these uncertainties are the impacts of a rapidly warming Arctic. We present observations from the CHACHA (CHemistry in the Arctic: Clouds, Halogens, and Aerosols) field campaign based out of Utqiaġvik, Alaska, from mid-February to mid-April of 2022 to provide information on the vertical distribution of bromine monoxide (BrO), which is a tracer for reactive bromine chemistry. Data were gathered using the Heidelberg Airborne Imaging DOAS (differential optical absorption spectroscopy) Instrument (HAIDI) on the Purdue University Airborne Laboratory for Atmospheric Research (ALAR) and employing a unique sampling technique of vertically profiling the lower atmosphere with the aircraft via “porpoising” maneuvers. Observations from HAIDI were coupled to radiative transfer model calculations to retrieve mixing ratio profiles throughout the lower atmosphere (below 1000 m), with unprecedented vertical resolution (50 m) and total information gathered (average of 17.5 degrees of freedom) for this region. A cluster analysis was used to categorize 245 retrieved BrO mixing ratio vertical profiles into four common profile shapes. We often found the highest BrO mixing ratios at the Earth's surface with a mean of nearly 30 pmol mol−1 in the lowest 50 m, indicating an important role for multiphase chemistry on the snowpack in reactive bromine production. Most lofted-BrO profiles corresponded with an aerosol profile that peaked at the same altitude (225 m above the ground), suggesting that BrO was maintained due to heterogeneous reactions on particle surfaces aloft during these profiles. A majority (11 of 15) of the identified lofted-BrO profiles occurred on a single day, 19 March 2022, over an area covering more than 24 000 km2, indicating that this was a large-scale lofted-BrO event. The clustered BrO mixing ratio profiles should be particularly useful for some MAX-DOAS (multi-axis DOAS) studies, where a priori BrO profiles and their uncertainties, used in optimal estimation inversion algorithms, are not often based on previous observations. Future MAX-DOAS studies (and past reanalyses) could rely on the profiles provided in this work to improve BrO retrievals. 

Reading and understanding scientific literature is an essential skill for any scientist to learn. While students’ scientific literacy can be improved by reading research articles, an article’s technical language and structure can hinder students’ understanding of the scientific material. Furthermore, many students struggle with interpreting graphs and other models of data commonly found in scientific literature. To introduce students to scientific literature and promote improved understanding of data and graphs, we developed a guided-inquiry activity adapted from a research article on snow chemistry and implemented it in a general chemistry laboratory course. Here, we describe how we adapted figures from the primary literature source and developed questions to scaffold the guided-inquiry activity. Results from semi-structured qualitative interviews suggest that students learn about snow chemistry processes and engage in scientific practices, including data analysis and interpretation, through this activity. This activity is applicable in other introductory science courses as educators can adapt most scientific articles into a guided-inquiry activity.