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Collaud Coen M.,Federal Office of Meteorology and Climatology | Andrews E.,University of Colorado at Boulder | Andrews E.,National Oceanic and Atmospheric Administration | Asmi A.,University of Helsinki | And 23 more authors.
Atmospheric Chemistry and Physics | Year: 2013

Currently many ground-based atmospheric stations include in-situ measurements of aerosol physical and optical properties, resulting in more than 20 long-term (> 10 yr) aerosol measurement sites in the Northern Hemisphere and Antarctica. Most of these sites are located at remote locations and monitor the aerosol particle number concentration, wavelength-dependent light scattering, backscattering, and absorption coefficients. The existence of these multi-year datasets enables the analysis of long-term trends of these aerosol parameters, and of the derived light scattering Ångström exponent and backscatter fraction. Since the aerosol variables are not normally distributed, three different methods (the seasonal Mann-Kendall test associated with the Sen's slope, the generalized least squares fit associated with an autoregressive bootstrap algorithm for confidence intervals, and the least-mean square fit applied to logarithms of the data) were applied to detect the long-term trends and their magnitudes. To allow a comparison among measurement sites, trends on the most recent 10 and 15 yr periods were calculated. No significant trends were found for the three continental European sites. Statistically significant trends were found for the two European marine sites but the signs of the trends varied with aerosol property and location. Statistically significant decreasing trends for both scattering and absorption coefficients (mean slope of-2.0% yr-1) were found for most North American stations, although positive trends were found for a few desert and high-altitude sites. The difference in the timing of emission reduction policy for the Europe and US continents is a likely explanation for the decreasing trends in aerosol optical parameters found for most American sites compared to the lack of trends observed in Europe. No significant trends in scattering coefficient were found for the Arctic or Antarctic stations, whereas the Arctic station had a negative trend in absorption coefficient. The high altitude Pacific island station of Mauna Loa presents positive trends for both scattering and absorption coefficients. © 2013 Author(s).


Hand J.L.,Colorado State University | Schichtel B.A.,National Park Service | Malm W.C.,Colorado State University | Copeland S.,Colorado State University | And 3 more authors.
Atmospheric Environment | Year: 2014

Visibility has improved significantly at many remote areas across the United States since the early 1990s. Trends in visibility were calculated using ambient light extinction coefficients (bext) estimated from speciated particulate concentrations measured by the IMPROVE (Interagency Monitoring of Protected Visual Environments) network. The 20% haziest bext levels were computed for each year following Regional Haze Rule guidelines and aggregated over three major regions of the United States. Over the last two decades (1992-2011) the regional mean 20% haziest bext dropped by 52% (-2.6%yr-1, p<0.01) in the eastern United States, and by 20% (-1.0%yr-1, p=0.08) for sites along the West Coast. However, in the Intermountain/Southwest region, the trend was insignificant (-0.2%yr-1, p=0.36). Over the last decade (2002-2011) the haziest bext in the Intermountain/Southwest region decreased by 15% (-1.5%yr-1, p=0.09), compared to a decrease of 35% (-3.5%yr-1, p=0.06) in the West Coast region and 50% (-5.0%yr-1, p=0.02) in the East. A novel aspect to this study is the visualization of trends through the simulation of images of national parks and other remote areas for early and current haziest conditions. These images are an effective means for communicating trends and illustrate the dramatic improvement in visibility, especially in the East, where reductions in sulfate concentrations and sulfur dioxide emissions have had a positive impact on visibility degradation. However, while conditions are clearer for regions in the West, less improvement points to the need for understanding the influences on the trends in haziest conditions in those regions. © 2014 Elsevier Ltd.


Green M.C.,Desert Research Institute | Chen L.W.A.,Desert Research Institute | DuBois D.W.,New Mexico State University | Molenar J.V.,Air Resource Specialists Inc.
Journal of the Air and Waste Management Association | Year: 2012

Speciated PM2.5 (particulate matter with an aerodynamic diameter ≤2.5 μm) data has been collected for about 20 yr (1990-present) at a rural location in the Lake Tahoe Basin (Bliss State Park) and about 15 yr (1989-2004) at an urban site in South Lake Tahoe. The Bliss State Park site is representative of the Desolation Wilderness, a Class I air quality area with visibility protection under the Clean Air Act. Carbonaceous aerosol dominated reconstructed fine mass at both sites, with 58% at Bliss State Park (BLIS) and 68% at South Lake Tahoe (SOLA). Fine mass at SOLA is 2.5 times that at BLIS, mainly due to enhanced organic and elemental carbon (OC and EC). SOLA experiences a winter peak in PM2.5 mainly due to OC and EC from residential wood combustion, whereas BLIS experiences a summer peak in PM2.5 mainly due to OC and EC from wildfires. Carbonaceous aerosol dominates visibility impairment, causing about 1/2 the reconstructed aerosol light extinction at BLIS and 70% at SOLA. Trend analysis (1990-2009) showed statistically significant decreases in aerosol extinction at BLIS on 20% best and 60% middle visibility days and statistically insignificant upward trends on 20% worst days. SOLA (1990-2003) showed statistically significant decreases in aerosol extinction for all day categories, driven by decreasing OC and EC. From the regional haze rule baseline period of 2000-2004 until 2005-2009, BLIS saw 20% best days improving and 20% worst days getting worse due to increased wildfire effects. Receptor modeling was performed using positive matrix factorization (PMF) and chemical mass balance (CMB). It confirmed that (1) biomass burning dominanted PM2.5 sources at both sites with increasing importance over time; (2) low combustion efficiency burning accounts for most of the biomass burning contribution; (3) road dust and traffic contributions were much higher at SOLA than at BLIS; and (4) industrial combustion and salting were minor sources.Implications: Visibility on the 20% worst visibility days decreased at Bliss State Park, which represents the Desolation and Mokelumne Wilderness Class I areas. This decrease in visibility, contrary to Regional Haze Rule requirements, was mainly due to increased wildfire activity. Increased sulfate-caused light extinction on worst visibility days may be due to long-range transport from Asia. These factors may make it difficult to achieve reasonable progress toward the national visibility goal. Methods need to be developed to account for the effect of wildfires and intercontinental transport when evaluating progress toward the national goal.Supplemental Materials: Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of the Air & Waste Management Association for details of the receptor modeling, including the average and signal-to-noise ratio (SNR) of PM2.5 mass and chemical concentrations for the 3 PMF modeling groups, PMF factor profiles, and sensitivity test results for the EV-CMP modeling. © 2012 Copyright 2012 A&WMA.


Li Y.,Colorado State University | Schwandner F.M.,Colorado State University | Sewell H.J.,Royal Dutch Shell | Zivkovich A.,Royal Dutch Shell | And 8 more authors.
Atmospheric Environment | Year: 2014

Continuous measurements of the atmospheric trace gases ammonia (NH3) and nitric acid (HNO3) and of fine particle (PM2.5) ammonium (NH4 +), nitrate (NO3 -) and sulfate (SO4 2-) were conducted using a denuder/filter system from December 2006 to December 2011 at Boulder, Wyoming, a region of active gas production. The average five year concentrations of NH3, HNO3, NH4 +, NO3 - and SO4 2- were 0.17, 0.19, 0.26, 0.32, and 0.48μgm-3, respectively. Significant seasonal patterns were observed. The concentration of NH3 was higher in the summer than in other seasons, consistent with increased NH3 emissions and a shift in the ammonium nitrate (NH4NO3) equilibrium toward the gas phase at higher temperatures. High HNO3 concentrations were observed both in the summer and the winter. Elevated wintertime HNO3 production appeared to be due to active local photochemistry in a shallow boundary layer over a reflective, snow-covered surface. PM2.5 NH4 + and SO4 2- concentrations peaked in summer while NO3 - concentrations peaked in winter. Cold winter temperatures drive the NH3-HNO3-NH4NO3 equilibrium toward particulate NH4NO3. A lack of NH3, however, frequently results in substantial residual gas phase HNO3 even under cold winter conditions. © 2013 Elsevier Ltd.


Molenar J.V.,Air Resource Specialists Inc. | Malm W.C.,Colorado State University
Air and Waste Management Association - Aerosol and Atmospheric Optics: Visibility and Air Pollution Specialty Conference 2012 | Year: 2012

A new method of displaying visual air quality images for surveys has been developed and initial tests completed. The method allows survey participants to continuously control the visual air quality they observe on a monitor to make their judgments. Initial pilot tests of by a few observers viewing urban scenes with & without distant features and with & without cumulus clouds have been completed. Preliminary results indicate that 1. The Phoenix scene which has distant mountains, the addition of clouds appears to make the scene less sensitive to haze, since the scene with clouds was not rated unacceptable until the dv level was 2.6 higher (hazier) than the scene without clouds The St Louis scene which has the most distant building at 1.7 km away, clouds made the scene 5.5 dv more sensitive. Washington DC scene which has more distant features than St Louis but not as far away as Phoenix was in between Phoenix and St Louis in sensitivity to clouds. The results of a larger set of observers will be presented at the conference.


PubMed | BK Econometrics LLP, Industrial Economics Inc., Bedrock Statistics LLC, Virginia Polytechnic Institute and State University and 2 more.
Type: | Journal: Journal of environmental management | Year: 2016

Environmental regulations often have the objective of eliminating the lower tail of an index of environmental quality. That part of the distribution of environmental quality moves somewhere above a threshold and where in the original distribution it moves is a function of the control strategy chosen. This paper provides an approach for estimating the economic benefits of different distributional changes as the worst environmental conditions are removed. The proposed approach is illustrated by examining shifts in visibility at Class I visibility areas (National Parks and wilderness areas) that would occur with implementation of the U.S. Environmental Protection Agencys Regional Haze Program. In this application we show that people value shifts in the distribution of visibility and place a higher value on the removal of a low visibility day than on the addition of a high visibility day. We found that respondents would pay about $120 per year in the Southeast U.S. and about $80 per year in the Southwest U.S. for improvement programs that remove the 20% worst visibility days.


Gebhart H.,Air Resource Specialists Inc. | Branscum I.,POET LLC
Proceedings of the Air and Waste Management Association's Annual Conference and Exhibition, AWMA | Year: 2014

A discussion on the current air emission and air permitting topics in the renewable fuels industry covers the greenhouse gas regulation on biorefinery sources; Project LIBERTY, an advanced biofuels project aiming to make cellulosic bio-ethanol competitive with corn bio-ethanol, the primary renewable liquid transportation fuel on the US market today, including the unique permitting challenges associated with the project, and how the EPA rules governing biogenic carbon impacts the plant permitting requirements; ongoing efforts to develop advanced biofuel projects within the State Of California and the environmental/permitting challenges faced by the project developers; the California Low Carbon Fuel Standard (LCFS); fuel pathways already approved under the LCFS, and the procedures required for new fuel pathways to be approved; and how biofuels production is treated under the LCFS as opposed to other types of advanced transportation fuels. This is an abstract of a paper presented at the AWMA's 107th Annual Conference & Exhibition (Long Beach, CA 6/24-27/2014).


Bibeau B.C.,Air Resource Specialists Inc.
Air and Waste Management Association - Symposium on Air Quality Measurement Methods and Technology 2010 | Year: 2010

MODBUS TCP/IP digital data acquisition has proven to be a robust and reliable method for collecting data from monitoring instrumentation, including trace-level NCore instruments. Its many advantages over RS-232 include efficient integration, standard hardware, and low cost. Combining this method of data collection with high-speed internet access and manufacturer supplied software, remote maintenance and troubleshooting can help provide a fast response to problems, often without the need to physically visit the station.


Molenar J.V.,Air Resource Specialists Inc.
Air and Waste Management Association - Aerosol and Atmospheric Optics: Visibility and Air Pollution Specialty Conference 2012 | Year: 2012

A new LED transmitter for the Optec Transmissometer has been successfully developed, tested, and deployed in urban visibility monitoring programs (Denver, Fort Collins, Phoenix) and the solar energy industry (Ivanpah & Israel). The LED transmitter has reduced power requirements, removed the need to have multiple calibrated lamps for a year of operation, eliminated data loss due to chopper motor failures, and eliminated the lamp brightening issue.


Molenar J.V.,Air Resource Specialists Inc.
Air and Waste Management Association - Aerosol and Atmospheric Optics: Visibility and Air Pollution Specialty Conference 2012 | Year: 2012

Measurements and analyses have shown that the exceptionally high photochemical ozone production observed in the UGRB in winter is the result of NOx and VOC effluents released in the production of natural gas in the area. These effluents become contained within a relatively shallow stagnant, stable air layer near the surface. When there is extensive snow cover and clear skies, these emmisions are rapidly converted photochemically to ozone which is in turn also trapped in the shallow, stable boundary layer. We conclude by noting that similar cold temperature ozone formation is probably occurring in other regions of the western U.S., and in Canada, Russia, Kazakhstan, Mongolia and China where fossil fuel extraction occurs in similar terrain and under similar meteorological conditions. At present, ozone measurements in most of these regions in winter are limited to non-existent.

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