Overview of the Alaskan Layered Pollution and Chemical Analysis (ALPACA) Field Experiment

Abstract

The Alaskan Layered Pollution And Chemical Analysis (ALPACA) field experiment was a collaborative study designed to improve understanding of pollution sources and chemical processes during winter (cold climate and low-photochemical activity), to investigate indoor pollution, and to study dispersion of pollution as affected by frequent temperature inversions. A number of the research goals were motivated by questions raised by residents of Fairbanks, Alaska, where the study was held. This paper describes the measurement strategies and the conditions encountered during the January and February 2022 field experiment, and reports early examples of how the measurements addressed research goals, particularly those of interest to the residents. Outdoor air measurements showed high concentrations of particulate matter and pollutant gases including volatile organic carbon species. During pollution events, low winds and extremely stable atmospheric conditions trapped pollution below 73 m, an extremely shallow vertical scale. Tethered-balloonbased measurements intercepted plumes aloft, which were associated with power plant point sources through transport modeling. Because cold climate residents spend much of their time indoors, the study included an indoor air quality component, where measurements were made inside and outside a house to study infiltration and indoor sources. In the absence of indoor activities such as cooking and/or heating with a pellet stove, indoor particulate matter concentrations were lower than outdoors; however, cooking and pellet stove burns often caused higher indoor particulate matter concentrations than outdoors. The mass-normalized particulate matter oxidative potential, a health-relevant property measured here by the reactivity with dithiothreiol, of indoor particles varied by continued...

Indoor–Outdoor Oxidative Potential of PM2.5 in Wintertime Fairbanks, Alaska: Impact of Air Infiltration and Indoor Activities

“…Residential areas of Fairbanks generally have higher concentrations of PM 2.5 species emitted from residential heating, such as organic species from wood burning . The house was in a residential area and similar to other types of housing in Fairbanks . It was a single-level (ranch style) structure covering approximately 1549 square feet (excluding the garage).…”

“… 55 The house was in a residential area and similar to other types of housing in Fairbanks. 56 It was a single-level (ranch style) structure covering approximately 1549 square feet (excluding the garage). Prior to the intensive study, a house pressurization test and energy audit were conducted.…”

Hydroxymethanesulfonate and Sulfur(IV) in Fairbanks Winter During the ALPACA Study

“…Pollution events in Fairbanks are characterized by large increases in PM 2.5 mass concentration and primary species, such as carbon monoxide (CO), nitrogen oxides (NOx) and SO 2, but low concentrations of ozone (O 3 ) due to limited sunlight and titration by NOx. These events occur during periods of very low temperatures, stable atmospheric conditions with calm winds and strong shallow temperature inversions that limit dispersion of the urban emissions. , …”

Investigating processes influencing simulation of local Arctic wintertime anthropogenic pollution in Fairbanks, Alaska during ALPACA-2022

“…Further details about measurement techniques, sites and the observations are given in Simpson et al (2024). Hourly averaged surface observations of CO, SO 2 at CTC and NC, NO x at CTC, as well as wind speed and direction and temperatures at 3, 11 and 23 m at CTC and 3 and 11 m at NC are used to evaluate FLEXPART-WRF tracer concentrations and EPA-WRF meteorology, respectively, in urban Fairbanks (Downtown in Fig.…”

“…To study these issues, the international ALPACA field campaign took place in Fairbanks in January and February 2022 (ALPACA-2022). The campaign design, measurements, and first results are described in Simpson et al (2024). Vertical profiles of trace gases and particles collected on a tethered balloon (Helikite) on the western edge of the city showed the regular presence of pollution layers close to the surface and aloft which emission tracer forecasts during the campaign attributed to power plant emissions (Simpson et al, 2024).…”