On the Limits to Manage Air-Quality in Glacier Bay

In Glacier Bay National Park, about 95% of the visitors come on board of cruise ships. The National Park Service has the mandate to manage park resources like air quality and visibility, while ensuring visitation. To understand the impact of cruise-ship emissions on the overall concentrations in Glacier Bay, emission-source contribution ratios (ESCR) and the interaction of pollutant from local and/or distant sources were determined using results from four WRF/Chem simulations of the 2008 tourist season (May 15 to September 15). These simulations only differed by the emissions considered: Biogenic emissions only (CLN), biogenic plus activity-based cruise-ship emissions (REF), biogenic plus all anthropogenic emissions except cruise-ship emissions (RETRO), and all aforementioned emissions (ALL). In general, ESCRs differed among pollutants. Interaction between pollutants from cruise-ship emissions and species from other sources including those advected into the bay decreased towards the top of the atmospheric boundary layer. Pollutants from different sources interacted strongest (lowest) in the west arm of the fjord where ships berthed for glacier viewing (in areas of the bay without cruise-ship travel). Pollutant interaction both enhanced/reduced NO2 concentrations by 10% (4 - 8 ppt absolute). Except for ozone, cruise-ship emissions on average governed air quality in the bay. On days with cruise-ship visits, they contributed between 60% and 80% of the bay-wide daily mean SO2 and NO2 concentrations below 1 km height. On days without visits, cruise-ship contributions still reached 40% due to previous visits. Highest cruise-ship ESCRs occurred during stagnant weather conditions. Despite the fact that all coarse particulate matter was due to anthropogenic sources, worst visibility conditions were due to meteorology. The results suggest limits as well as windows for managing air quality and visibility in Glacier Bay.

Climatology of Air Quality in Arctic Cities—Inventory and Assessment

Freely available data of sulfur dioxide (SO2), ammonia (NH3), nitrogen dioxide (NO2), ozone (O3), and particulate matter (PM) observed in Arctic cities (north of 59.99 N) between 1972 and 2016 were compiled into an air-quality inventory of samples taken for limited periods. For cities with multiple years of data, air-quality climatology was determined in terms of daily means in the annual course. Mean urban air-quality climatology was calculated for regions of similar insolation, emission standards, topography, K&#246ppen-Geiger classification, and city size. Urban concentrations of PM precursors (SO2, NH3, NO2), PM2.5 and PM10 (PM with diameter less than 2.5 and 10 μm) were assessed in the sense of climatology with evidence from current knowledge. Typically, annual SO2 and NO2 means were lower for small than large Arctic cities, but can vary more than an order of magnitude over short distance. Cities seeing seasonal sea-ice had W-shaped mean annual courses of daily O3, while other cities had a spring maximum. Typically, annual means of urban pollutants in North America exceeded those in Scandinavia except for O3, where the opposite was true. Annual mean urban PM2.5 and PM10 concentrations varied from 1.6 to 21.2 μg·m-3 and 2 to 18.2 μg·m-3, respectively. Since PM10 encompasses PM2.5, annual PM10 means must be at least 21.2 μg·m-3. According to rural-to-urban ratios of species, seasonal transport of pollutants from wildfires, shipping, and the Kola Peninsula mining area occurred at some sites in Interior Alaska, western and northern Norway, respectively. Concurrent SO2 and PM or NO2 and PM measurements revealed combustion or traffic as major contributors to urban concentrations. Recommendations for potential future measurements of Arctic urban air quality were given based on the assessments of climatology and inventory.

Model-Measurement Comparison of Ammonia Bi-Directional Air-Surface Exchange Fluxes over Agricultural Fields

Modeled and measured bi-directional fluxes (BDFs) of ammonia (NH3) were compared over fertilized soybean and corn canopies for three intensive sampling periods: the first, during the summer of 2002 in Warsaw, North Carolina (NC), USA;and the second and third during the summer of 2007 in Lillington, NC. For the first and the third experimental periods, the BDF model produced reasonable diurnal flux patterns. The model also produced correct flux directions (emission and dry deposition) and magnitudes under dry and wet canopy conditions and during day and nighttime for these two periods. However, the model fails to produce the observed very high upward fluxes from the second sampling period due to the fertilization application (and thus being much higher soil emission potentials in the field than the default model values), although this can be improved by adjusting model input of soil emission potentials. Model-measurement comparison results suggest that the model is likely capable for improving long-term or regional scale ammonia predictions if implemented in chemical transport models replace the traditional dry deposition models, although modifications are needed when applying to specific situations.

Particulate Matter Exposure of Rural Interior Communities as Observed by the First Tribal Air Quality Network in the Yukon Flat

A tribal-owned network of aerosol monitors and meteorological stations was installed at Ts’aahudaaneekk’onh Denh (Beaver), Gwichyaa Zheh (Fort Yukon), Jalgiitsik (Chalkyitsik), and Danzhit Khànlaii (Circle) in the Yukon Flats, Alaska. Surface inversions occurred under calm wind conditions due to radiative cooling. In May, local emissions governed air quality with worst conditions related to road and river dust. As the warm season progressed, worst air quality was due to transport of pollutants from upwind wildfires. During situations without smoke or when smoke existed at layers above the surface inversion, concentrations of particulate matter of less than 2.5 micrometer in diameter or less (PM2.5) were explainable by the local emissions;24-h means remained below 25 μg·m-3. Absorption of solar radiation in the smoke layer and upward scattering enhanced stability and fostered the persistence of the surface inversions. During smoke episodes without the presence of a surface inversion, daily mean concentrations exceeded 35 μg·m-3 often for several consecutive days, at all sites. Then concentrations temporally reached levels considered unhealthy.

Air quality monitoring using mobile microscopy and machine learning

Rapid,accurate and high-throughput sizing and quantification of particulate matter(PM)in air is crucial for monitoring and improving air quality.In fact,particles in air with a diameter of≤2.5μm have been classified as carcinogenic by the World Health Organization.Here we present a field-portable cost-effective platform for high-throughput quantification of particulate matter using computational lens-free microscopy and machine-learning.This platform,termed c-Air,is also integrated with a smartphone application for device control and display of results.This mobile device rapidly screens 6.5 L of air in 30 s and generates microscopic images of the aerosols in air.It provides statistics of the particle size and density distribution with a sizing accuracy of~93%.We tested this mobile platform by measuring the air quality at different indoor and outdoor environments and measurement times,and compared our results to those of an Environmental Protection Agency–approved device based on beta-attenuation monitoring,which showed strong correlation to c-Air measurements.Furthermore,we used c-Air to map the air quality around Los Angeles International Airport(LAX)over 24 h to confirm that the impact of LAX on increased PM concentration was present even at 47 km away from the airport,especially along the direction of landing flights.With its machinelearning-based computational microscopy interface,c-Air can be adaptively tailored to detect specific particles in air,for example,various types of pollen and mold and provide a cost-effective mobile solution for highly accurate and distributed sensing of air quality.

Climatology of the Meteorological Factors Associated with Haze Events over Northern China and Their Potential Response to the Quasi-Biannual Oscillation

An upswing in haze weather during autumn and winter has been observed over North and Northeast China in re- cent years, imposing adverse impacts upon local socioeconomic development and human health. However, such an increase in the occurrence of haze events and its association with natural climate variability and climate change are not well understood. To investigate the climatology of the meteorological factors associated with haze events and their natural variability, this study uses a meteorological pollution index called PLAM （Parameter Linking Air-qual- ity to Meteorological conditions） and ERA-Interim reanalysis data. The results suggest that high PLAM values tend to occur over southern parts of northem China, implying the weather conditions over this area are favorable for the occurrence of haze weather. For the period 1979-2014, the regional mean PLAM shows an overall increase across Beijing, Tianjin, and Hebei Province, and parts of Shanxi Province. Also, a periodicity of 28-34 months is found in the temporal variation of PLAM, which implies a potential association of PLAM with the stratospheric Quasi-Bian- nual Oscillation （QBO）. By using the QBO index during the autumn and winter seasons in the preceding year, an in- crease in PLAM is found for the westerly phases of the QBO, relative to the easterly phases. An upper-tropospheric warming is also found in the westerly phases, which can induce a stable stratification that favors the increase in PLAM across the midlatitudes. The modulations of large-scale environmental factors, including moist static stability, vertical velocity, and temperattu＇e advection, also act to enhance PLAM in the westerly phases. However, the baro- clinic term of moist potential vorticity at 700 hPa tends to decrease over the south, and an increase in low-level as- cent is found over the north. These factors can reduce PLAM and possibly limit the statistical significance of the in- creased PLAM in the westerly phases of the QBO.