Influence of background particulate matter (PM) on urban air quality in the Pacific Northwest

Very high-resolution remote sensing-based mapping of urban residential districts to help combat COVID-19

Urban residential districts (URDs) are a major element in the formation of cities that are essential for urban planning. Regarding the COVID-19 virus, which remains variable in aerosols for several hours, airborne transmission tends to occur in areas of poor ventilation and high occupant density. Thus, ventilation capacity is an important factor influencing airborne transmission in URDs, which should be evaluated as part of efforts to fight COVID-19 and guide healthy city planning and implementation. Here, we develop and test systematic methods to map URDs in a typical city in northern China and quantify their ventilation capacity using very high-resolution remote sensing images. Four fundamental spatial forms of URD are identified in the research area: the point-group form, parallel form, enclosed form, and hybrid form. Our analyses indicate that the integrated ventilation capacities for well-designed URDs are nearly twice those of poorly designed URDs. Large variations in ventilation capacity are also observed within URDs, with up to 13.42 times difference between the buildings. Therefore, very high-resolution remote sensing data are fundamental for extracting building height and generating precise spatial forms, which can improve the micro-scale URD ventilation planning for the prevention of COVID-19.

Machine Learning-Based Integration of High-Resolution Wildfire Smoke Simulations and Observations for Regional Health Impact Assessment

Large wildfires are an increasing threat to the western U.S. In the 2017 fire season, extensive wildfires occurred across the Pacific Northwest (PNW). To evaluate public health impacts of wildfire smoke, we integrated numerical simulations and observations for regional fire events during August-September of 2017. A one-way coupled Weather Research and Forecasting and Community Multiscale Air Quality modeling system was used to simulate fire smoke transport and dispersion. To reduce modeling bias in fine particulate matter (PM2.5) and to optimize smoke exposure estimates, we integrated modeling results with the high-resolution Multi-Angle Implementation of Atmospheric Correction satellite aerosol optical depth and the U.S. Environmental Protection Agency AirNow ground-level monitoring PM2.5 concentrations. Three machine learning-based data fusion algorithms were applied: An ordinary multi-linear regression method, a generalized boosting method, and a random forest (RF) method. 10-Fold cross-validation found improved surface PM2.5 estimation after data integration and bias correction, especially with the RF method. Lastly, to assess transient health effects of fire smoke, we applied the optimized high-resolution PM2.5 exposure estimate in a short-term exposure-response function. Total estimated regional mortality attributable to PM2.5 exposure during the smoke episode was 183 (95% confidence interval: 0, 432), with 85% of the PM2.5 pollution and 95% of the consequent multiple-cause mortality contributed by fire emissions. This application demonstrates both the profound health impacts of fire smoke over the PNW and the need for a high-performance fire smoke forecasting and reanalysis system to reduce public health risks of smoke hazards in fire-prone regions.

Local pollutants go global: The impacts of intercontinental air pollution from China on air quality and morbidity in California

China is among the greatest emitters of air pollution in the world and one concern is the effects of intercontinental air pollution traveling across the Pacific Ocean from China to the U.S. We exploit a natural experiment by observing the effects of changes in intercontinental air pollution associated with Chinese New Year, a 7-day national holiday, and sandstorms from China on air quality and morbidity in California. The timing of these events are unlikely correlated to other factors affecting air quality and health in California. Chinese New Year follows the Lunar New Year which varies each traditional calendar year while sandstorms are a naturally occurring phenomenon. We examine effects on morbidity using restricted emergency department and inpatient hospitalization data for the universe of patients with respiratory and heart disease between 2005 and 2012 in California. This is the first study to use patient-level data to examine the effects of trans-Pacific air pollution from China on morbidity in the U.S. We show that heavy sandstorms are associated with a modest increase in acute respiratory disease per capita, representing 0.5-4.6% of average weekly hospitalizations. However, we find no significant effect on morbidity in California from Chinese New Year. Results suggest that policymakers could prepare for changes in air quality following major sandstorms in China.

Particulate and gaseous pollutants in a petrochemical industrialized valley city, Western China during 2013-2016

Airborne pollutant characteristics, potential sources, and variation trends of cause are investigated based on the hourly air concentrations of gaseous pollutants and particulate matter from 2013 to 2016 in Lanzhou. The mean concentration of SO₂, NO₂, CO, 8-hO₃, PM_2.5, and PM₁₀ was 25.2 ± 16.0 μg m^-3, 46.5 ± 21.1 μg m^-3, 1.3 ± 0.7 mg m^-3, 77.8 ± 45.5 μg m^-3, 58.7 ± 32.9 μg m^-3, and 131.1 ± 86.2 μg m^-3, respectively. The concentrations of SO₂, PM₁₀, and PM_2.5 present decreasing trends while NO₂, CO, and O₃ present increasing trends. PM is the most frequent major pollutants with much higher value than standard limit. However, NO₂ pollution had obvious trends to reach the limit and was more serious in Lanzhou compared with other Chinese cities. Relationship between air pollutants and meteorological parameters suggested that lower primary pollutants were associated with higher wind speed from north and west. Modeled back trajectory demonstrated that the transport of air masses from the Hexi Corridor and Inner Mongolia was responsible for the high concentrations of the air pollutants in wintertime, and high PM₁₀ level in springtime was related to long-range transport of dust from desert areas of the Sinkiang and the Central Asia. Effects of local pollutant emissions and meteorological condition were preliminary analyzed. Improvement of air quality might be related to the decreasing of pollutant emissions due to strict emissions controls, and the contribution of meteorological condition was not explicit and should be further investigated.

Relative Influence of Trans-Pacific and Regional Atmospheric Transport of PAHs in the Pacific Northwest, U.S

The relative influences of trans-Pacific and regional atmospheric transport on measured concentrations of polycyclic aromatic hydrocarbons (PAHs), PAH derivatives (nitro- (NPAH) and oxy-(OPAH)), organic carbon (OC), and particulate matter (PM) less than 2.5 μm in diameter (PM2.5) were investigated in the Pacific Northwest, U.S. in 2010-2011. Ambient high volume PM2.5 air samples were collected at two sites in the Pacific Northwest: (1.) Mount Bachelor Observatory (MBO) in the Oregon Cascade Range (2763 m above sea level (asl)) and 2.) Confederated Tribes of the Umatilla Indian Reservation (CTUIR) in the Columbia River Gorge (CRG) (954 m asl). At MBO, the 1,8-dinitropyrene concentration was significantly positively correlated with the time a sampled air mass spent over Asia, suggesting that this NPAH may be a good marker for trans-Pacific atmospheric transport. At CTUIR, NOx, CO2, and SO2 emissions from a 585 MW coal fired power plant, in Boardman OR, were found to be significantly positively correlated with PAH, OPAH, NPAH, OC, and PM2.5 concentrations. By comparing the Boardman Plant operational time frames when the plant was operating to when it was shut down, the plant was found to contribute a large percentage of the measured PAH (67%), NPAH (91%), OPAH (54%), PM2.5 (39%), and OC (38%) concentrations at CTUIR and the CRG prior to Spring 2011 and likely masked trans-Pacific atmospheric transport events to the CRG. Upgrades installed to the Boardman Plant in the spring of 2011 dramatically reduced the plant's contribution to PAH and OPAH concentrations (by ∼72% and ∼40%, respectively) at CTUIR and the CRG, but not NPAH, PM2.5 or OC concentrations.

Outdoor PM₁₀ source apportionment in metropolitan cities--a case study

This study was carried out to specify contribution of different sources in PM10 emission in Tehran City using chemical mass balance method. This is the first time that this method is used in Iran. To this end, the metallic elements including V, Ni, As, Pb, Cd, Hg, Mn, Al, Ca, K, Na, Fe, Zn, Sc, and S were sampled on the filters of high-volume sampler installed at four stations in Tehran. Afterward, highly sensitive inductively coupled plasma (ICP-M90; model aurora-Elit) was used to determine concentration of the elements precipitated on the filters. The obtained results were then compared with standard values. According to the results, the concentration of Cd (16.8 ng/m(3)) was higher than the standard level of 5 ng/m(3) at District 16 on November 14th 2012 which is almost three times the permissible limit. None of the elements Pb, Mn, V, and Hg exceeded the permissible limits except for Ni at District 16. Subsequently, the enrichment factor of the elements was calculated to indicate that elements of anthropogenic origins (Zn, S, Ni, and Hg) are highly enriched with respect to crustal composition (Na, Fe, and Ca). Exceedance factor were calculated for elements of each site to show that all study sites were in low-pollution category. Afterward, the contribution of different pollution sources of road dust, vehicles, and industries in emission of outdoor PM10 was investigated through chemical mass balance (CMB) method. According to which, the highest contribution comes from road dust with a share of 95.4 % of the total outdoor PM10 emission in Tehran mainly originated from the wear and friction of car tires with asphalt pavement. High calcium concentration in all districts of the city confirms the claim. Furthermore, transportation, with a significant difference, has a contribution of 4.05 % of total outdoor PM10 released while industries share very little about 0.4 %. In overall, the quality of road pavement could be a determining factor in releasing considerable amount of outdoor PM10 in urban areas.