We quantified the contributions of long-range and regionally transported aerosols to ambient primary PM_2.5 and PM₁₀ in a representative United States industrialized/urban atmosphere via detailed elemental analysis and chemical mass balance (CMB) modeling after identifying their presence using satellite data and synoptic-scale aerosol models. A year-long study in Houston, Texas identified North African dust as the principal long-range global source of primary particulate matter (PM). CMB estimated transatlantic dust from the Sahara-Sahel region to be dominant during the active Saharan dust season. Biomass burning was the chief source of regionally transported PM impacting air quality on different occasions throughout the year depending on the fire location. Four major biomass combustion events affecting air quality were identified whose origins were tracked to Canada, southeastern states of USA, and Central America using fire maps, HYSPLIT back trajectories, and the Navy Aerosol Analysis and Prediction System global aerosol model. Elemental concentrations and signature ratios revealed significant mixing of potassium, rare earth metals, and vanadium from proximal and distal crustal (natural) sources with anthropogenically emitted PM. This demonstrates the need to isolate the non-mineral components of these metals to employ them as tracers for primary PM emitted by biomass burning, petroleum refineries, and oil combustion. Transboundary contributions to primary PM_2.5 added 16% to annual average mass concentrations of both PM size fractions, i.e., local sources dominated ambient air quality. Rigorously identifying and quantifying aerosol sources assists in improving air quality management policies designed to protect public health and comply with ever-decreasing federal PM standards.

Future energy transitions in the U.S. will cause changes in air pollutant emissions, which in turn affect future air quality and mortality caused by surface ozone (O₃) and fine particulate matter (PM_2.5). In this work, the Environmental Benefits Mapping and Analysis Program-Community Edition is applied to assess the health and economic impacts of five future energy transition scenarios in the U.S. including a reference scenario without the clean power plan (refnocpp), a scenario with abundant natural gas (highNG), a scenario with high electric vehicle market share (highEV), a scenario with port electrification (port), and a scenario with intensive building energy efficiency (highEE). Changes in the concentration of O₃ and PM_2.5 are simulated using an online-coupled meteorology and air quality model (WRF-Chem) and an offline model (CMAQ). Future energy transitions may avoid 998-1,932 deaths annually for O₃ and 28,541-36675 for PM_2.5, saving $9-19.8 and $257-330 billion U.S. dollar annually, respectively. Large reduction in mortalities occur for populated urban areas where the changes in emissions are large. Among these scenarios, the highEE scenario has the maximum co-benefit to both air quality and public health. While the projected changes in air quality and mortality by both models under all scenarios are overall similar, CMAQ tends to give larger reduction in O₃ but smaller reduction in PM_2.5, leading to more avoided death and saved costs by O₃ but less avoided death and saved costs by PM_2.5. These results can inform the relative co-benefit and priority of the implementation of these future energy transitions.

Recent decades saw increasing wildfire activities in the western US. Climate change is expected to increase the frequency of fire-prone weather conditions. The annual burned area has increased by more than a factor of three over California since 1985. While the impacts of wildfires on particulate matter air quality are well known, the extent to which biomass burning emissions affect gaseous air pollutants, such as ozone and its precursors, is less clear. In California, the national standard for ozone has been broadly violated. Wildfires emit substantial amounts of ozone precursors, nitrogen oxides (NO_x) and volatile organic compounds (VOCs), which react in the presence of sunlight to produce ozone. Here we present an observational approach that integrates smoke products, satellite retrievals of ozone precursors, and in-situ measurements to explore how wildfire emissions, when mixed with anthropogenic emissions, affect the ozone-NO_x-VOC chemistry from source to downwind urban areas in California in the past two decades. Satellite observations show that fires cause widespread increase of ozone precursors across California, which could partially offset the reduction of NO_x and VOCs from decades of anthropogenic emission control programs. The impacts of wildfire NOx emissions are concentrated near-field over NOx-limited region, and impacts of VOC emissions are more widespread, which extend to the VOC-limited urban areas, both leading to higher ozone production efficiency. The effects of precursor emissions outweigh the competing effects of smoke aerosols, which is evidenced from observed ozone enhancement under wildfire smoke.

In response to COVID-19, attention has been drawn to indoor air quality and developing interventions to mitigate COVID-19 transmission. Among air filtration interventions, Corsi-Rosenthal (CR) boxes may have the co-benefit of removing indoor air contaminants. This study employed non-targeted and suspect screening analysis (NTA and SSA) to detect and identify airborne volatile and semi-volatile organic contaminants (VOCs and SVOCs) that changed after installation of CR boxes. Using a quasi-experimental design, we sampled indoor air before (October–November 2021) and during (February–March 2022) installation of CR boxes in 17 rooms inside an occupied Providence, Rhode Island office building (the Brown University School of Public Health). We measured VOCs and SVOCs using three high resolution mass spectrometry (HRMS) NTA workflows and quantified area count changes during vs. before installation using linear mixed models. Gas phase log2-transformed area counts of 54 features significantly decreased by 75 to 100% after CR boxes were installed (FDR p-value<0.2). These included disinfectants (n=2), food preservatives (n=1), fragrance and flavorants (n=5), nitrogen-containing heterocyclic compounds (n=12), organophosphate esters (n=2), pesticides/herbicides/insecticides (n=11), pharmaceuticals (n=4), and volatile fatty acids (n=3). Principal Component Analysis of compound area counts in one HRMS NTA almost perfectly distinguished samples collected before versus during the intervention. Using NTA, we demonstrated that CR boxes can be an effective means for improving indoor air quality by reducing concentrations of a wide range of VOCs and SVOCs.

The Boston MBTA serves over 1.2 million trips daily, of which 55% are on the subway, making it one of the top five busiest subways in the United States. Monitoring studies conducted in past decades (e.g., Seoul, New York City, and Cairo) have examined the rider experience by characterizing environmental conditions across different dimensions, including air quality, vibration, and noise levels; however, to date a similar comprehensive mapping of the T had not been conducted. This study aimed to collect a multi-modal dataset (temperature, humidity, noise, vibration, and particulate matter) characterizing the overall environmental conditions experienced by riders of the rail-based rapid transit components of the T to better understand heterogeneous conditions in the system (e.g., potentially identify hotspots where remediation would be beneficial) and facilitate analysis on whether there might be disparities in exposure between serviced Boston-area communities. A low-cost, integrated sensing system was developed to enable logging of data at intervals down to less than one minute for certain parameters, relevant to timescales of moving vehicles. This talk will present the details of the methodological approach, collected data sets, and a snapshot of the pre-pandemic conditions in the system as well as identify key determining factors that explain differences in conditions between track segments/lines and suggest opportunities for systematic improvement. Learnings from this work will be explored in the context of an unfolding project doing high-resolution air quality monitoring across several communities in metro-Boston. Acknowledgements to coordination support from MA DOT and the MBTA for the T study.