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Aghaei Y, Aldekheel M, Tohidi R, Badami MM, Farahani VJ, Sioutas C. Development and performance evaluation of online monitors for near real-time measurement of total and water-soluble organic carbon in fine and coarse ambient PM. ATMOSPHERIC ENVIRONMENT (OXFORD, ENGLAND : 1994) 2024; 319:120316. [PMID: 38250566 PMCID: PMC10795521 DOI: 10.1016/j.atmosenv.2023.120316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2024]
Abstract
In this study, we developed two online monitors for total organic carbon (TOC) and water-soluble organic carbon (WSOC) measurements in fine (dp < 2.5μm) and coarse (2.5μm < dp < 10μm) particulate matter (PM), respectively. Their performance has been evaluated in laboratory and field tests to demonstrate the feasibility of using these monitors to measure near real-time concentrations, with consideration of their potential for being employed in long-term measurements. The fine PM collection setup was equipped with a versatile aerosol concentration enrichment system (VACES) connected to an aerosol-into-liquid-sampler (AILS), whereas two virtual impactors (VIs) in tandem with a modified BioSampler were used to collect coarse PM. These particle collection setups were in tandem with a Sievers M9 TOC analyzer to read TOC and WSOC concentrations in aqueous samples hourly. The average hourly TOC concentration measured by our developed monitors in fine and coarse PM were 5.17 ± 2.41 and 0.92 ± 0.29 μg/m3, respectively. In addition, our TOC readings showed good agreement and were comparable with those quantified using Sunset Lab EC/OC analyzer operating in parallel as a reference. Furthermore, we conducted field tests to produce diurnal profiles of fine PM-bound WSOC, which can show the effects of ambient temperature on maximum values in the nighttime chemistry of the winter, as well as on increased photochemical activities in afternoon peaks during the summer. According to our experimental campaign, WSOC mean values during the study period (3.07 μg/m3 for the winter and 2.7 μg/m3 for the summer) were in a comparable range with those of earlier studies in Los Angeles. Overall, our results corroborate the performance of our developed monitors in near real-time measurements of TOC and WSOC, which can be employed for future source apportionment studies in Los Angeles and other areas, aiding in understanding the health impacts of different pollution sources.
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Affiliation(s)
- Yashar Aghaei
- University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, California, USA
| | - Mohammad Aldekheel
- University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, California, USA
- Kuwait University, Department of Civil Engineering, P.O Box 5969, Safat 13060, Kuwait
| | - Ramin Tohidi
- University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, California, USA
| | - Mohammad Mahdi Badami
- University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, California, USA
| | - Vahid Jalali Farahani
- University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, California, USA
| | - Constantinos Sioutas
- University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, California, USA
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2
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Stanimirova I, Rich DQ, Russell AG, Hopke PK. Common and distinct pollution sources identified from ambient PM 2.5 concentrations in two sites of Los Angeles Basin from 2005 to 2019. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 340:122817. [PMID: 37913979 DOI: 10.1016/j.envpol.2023.122817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Revised: 10/23/2023] [Accepted: 10/26/2023] [Indexed: 11/03/2023]
Abstract
The effects of air quality control policies implemented in California from 2005 to 2019 targeting sources contributing to ambient PM2.5 concentrations, were assessed at two sampling sites in the Los Angeles Basin (N. Main Street and Rubidoux). The spatial and temporal variations of pollution source contributions obtained from dispersion-normalized positive matrix factorization, (DN-PMF) were interpreted with respect to site specific locations. Secondary nitrate and secondary sulfate were the major contributors to the ambient PM2.5 mass concentrations at both sites with substantial concentration decreases after 2008 that were likely due to the implementation of California specific programs including stricter NOx emissions control on motor vehicles. Biomass burning emissions also decreased over the study period at both sampling sites except for one event in December 2005 when strong winter storms and multiple floods led to unusually low atmospheric temperatures and likely increased residential wood burning. The large number of wildfires, trans-Pacific transport of mineral dust and regional dust transported by strong Santa Ana winds and agriculturally generated dust in Rubidoux contributed to poor air quality. Severe storms and devastating wildfires were also linked to the elevated pyrolyzed organic carbon (OP-rich) concentrations. The two distinct region-specific sources, describing fuel combustion in LA, were "residual oil" and "traffic", while separate "gasoline" and "diesel" vehicles sources were identified in Rubidoux. California emissions standards program which required replacement of conventional cars with electric or hybrid vehicles and standards for gasoline and diesel fuels, led to lower "traffic" contributions. Gasoline vehicle emissions after 2017 in Rubidoux also decreased. "Diesel" concentrations declined between 2007 and 2011 because of the recession from late 2007 to early 2009 and the Federal Heavy-Duty Diesel Rule.
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Affiliation(s)
- I Stanimirova
- Institute of Chemistry, University of Silesia in Katowice, Katowice, 40-006, Poland; Department of Public Health Sciences, University of Rochester Medical Center, Rochester, NY, USA.
| | - David Q Rich
- Department of Public Health Sciences, University of Rochester Medical Center, Rochester, NY, USA
| | - Armistead G Russell
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - P K Hopke
- Department of Public Health Sciences, University of Rochester Medical Center, Rochester, NY, USA; Institute for Sustainable Environment, Clarkson University, Potsdam, NY, 13699, USA
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3
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Perdigones BC, Lee S, Cohen RC, Park JH, Min KE. Two Decades of Changes in Summertime Ozone Production in California's South Coast Air Basin. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:10586-10595. [PMID: 35855520 DOI: 10.1021/acs.est.2c01026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Tropospheric ozone (O3) continues to be a threat to human health and agricultural productivity. While O3 control is challenging, tracking underlying formation mechanisms provides insights for regulatory directions. Here, we describe a comprehensive analysis of the effects of changing emissions on O3 formation mechanisms with observational evidence. We present a new approach that provides a quantitative metric for the ozone production rate (OPR) and its sensitivity to precursor levels by interpreting two decades of in situ observations of the six criteria air pollutants(2001-2018). Applying to the South Coast Air Basin (SoCAB), California, we show that by 2016-2018, the basin was at the transition region between nitrogen oxide (NOx)-limited and volatile organic compound (VOC)-limited chemical regimes. Assuming future weather conditions are similar to 2016-2018, we predict that NOx-focused reduction is required to reduce the number of summer days the SoCAB is in violation of the National Ambient Air Quality Standard (70 ppbv) for O3. Roughly, ∼40% (∼60%) NOx reductions are required to reduce the OPR by ∼1.8 ppb/h (∼3.3 ppb/h). This change would reduce the number of violation days from 28 to 20% (10%) in a year, mostly in summertime. Concurrent VOC reductions which reduce the production rate of HOx radicals would also be beneficial.
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Affiliation(s)
- Begie C Perdigones
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
| | - Soojin Lee
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
| | - Ronald C Cohen
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Department of Earth and Planetary Science, University of California, Berkeley, California 94720, United States
| | - Jeong-Hoo Park
- Climate and Air Quality Research Department, National Institute of Environmental Research, Incheon 22689, Korea
| | - Kyung-Eun Min
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
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4
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Soleimanian E, Mousavi A, Taghvaee S, Shafer MM, Sioutas C. Impact of secondary and primary particulate matter (PM) sources on the enhanced light absorption by brown carbon (BrC) particles in central Los Angeles. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 705:135902. [PMID: 31837867 DOI: 10.1016/j.scitotenv.2019.135902] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 11/15/2019] [Accepted: 12/01/2019] [Indexed: 05/23/2023]
Abstract
In this study, we investigated aerosol chemical composition, spectral properties of aerosol extracts, and source contributions to the aerosol light-absorbing brown carbon (BrC) in central Los Angeles from July 2018 to March 2019, during warm and cold seasons. Spectrophotometric measurements (water and methanol extracts; 200 < λ < 1100) and chemical analyses were performed on collected particulate matter (PM), and relationships of BrC light absorption (Abs365) to source tracer chemical species were evaluated. Mass absorption efficiency (MAE) of both water and methanol extracted solutions exhibited an increasing trend from warm period to cold season, with an annual average value of 0.61 ± 0.22 m2.g-1 and 1.38 ± 0.89 m2.g-1, respectively. Principal component analysis (PCA) were coupled with multiple linear regression (MLR) to identify and quantify sources of BrC light absorption in each of the seasons. Our finding documented fossil fuel combustion as the dominant source of BrC light absorption during warm season, with relative contribution of 38% to total BrC light absorption, followed by (secondary organic aerosol) SOA (30%) and biomass burning (12%). In contrast, biomass burning was the major source of BrC during the cold season (53%), while fossil fuel combustion and SOA contributed to 18% and 12% of BrC, respectively. Significantly higher contribution of biomass burning to BrC during the cold season suggested that residential heating activities (wood burning) play a major role in increased BrC concentrations. Previously collected Aethalometer model data documented fossil fuel combustion as the dominant contributing source to >90% of BC throughout the year. Finally, the solar radiation absorption ratio of BrC to elemental carbon (EC) in the ultraviolet range (300-400 nm) was maximum during the cold season with the annual corresponding values of 13-25% and 17-29% for water- and methanol-soluble BrC, respectively; which provides further evidence of the important effect of BrC light absorption on atmospheric radiative balance.
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Affiliation(s)
- Ehsan Soleimanian
- University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
| | - Amirhosein Mousavi
- University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
| | - Sina Taghvaee
- University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
| | - Martin M Shafer
- University of Wisconsin-Madison, Wisconsin State Laboratory of Hygiene, Madison, WI, USA.
| | - Constantinos Sioutas
- University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
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Lopez-Coto I, Hicks M, Karion A, Sakai RK, Demoz B, Prasad K, Whetstone J. Assessment of Planetary Boundary Layer parametrizations and urban heat island comparison: Impacts and implications for tracer transport. JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY 2020; 59:10.1175/jamc-d-19-0168.1. [PMID: 33488312 PMCID: PMC7818892 DOI: 10.1175/jamc-d-19-0168.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Accurate simulation of planetary boundary layer height (PBLH) is key to greenhouse gas emission estimation, air quality prediction and weather forecasting. This manuscript describes an extensive performance assessment of several Weather Research and Forecasting (WRF) model configurations where novel observations from ceilometers, surface stations and a flux tower were used to study their ability to reproduce planetary boundary layer heights (PBLH) and the impact that the urban heat island (UHI) has on the modeled PBLHs in the greater Washington, D.C. area. In addition, CO2 measurements at two urban towers were compared to tracer transport simulations. The ensemble of models used 4 PBL parameterizations, 2 sources of initial and boundary conditions and 1 configuration including the building energy parameterization (BEP) urban canopy model. Results have shown low biases over the whole domain and period for wind speed, wind direction and temperature with no drastic differences between meteorological drivers. We find that PBLH errors are mostly positively correlated with sensible heat flux errors, and that modeled positive UHI intensities are associated with deeper modeled PBLs over the urban areas. In addition, we find that modeled PBLHs are typically biased low during nighttime for most of the configurations with the exception of those using the MYNN parametrization and that these biases directly translate to tracer biases. Overall, the configurations using MYNN scheme performed the best, reproducing the PBLH and CO2 molar fractions reasonably well during all hours, thus opening the door to future nighttime inverse modeling.
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Affiliation(s)
- Israel Lopez-Coto
- Corresponding author address: National Institute of Standards and Technology, Gaithersburg, MD,
| | | | - Anna Karion
- National Institute of Standards and Technology, Gaithersburg, MD
| | | | - Belay Demoz
- Department of Physics, University of Maryland, Baltimore County, Baltimore, MD
| | - Kuldeep Prasad
- National Institute of Standards and Technology, Gaithersburg, MD
| | - James Whetstone
- National Institute of Standards and Technology, Gaithersburg, MD
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6
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Cui YY, Vijayan A, Falk M, Hsu YK, Yin D, Chen XM, Zhao Z, Avise J, Chen Y, Verhulst K, Duren R, Yadav V, Miller C, Weiss R, Keeling R, Kim J, Iraci LT, Tanaka T, Johnson MS, Kort EA, Bianco L, Fischer ML, Stroud K, Herner J, Croes B. A Multiplatform Inversion Estimation of Statewide and Regional Methane Emissions in California during 2014-2016. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:9636-9645. [PMID: 31347357 DOI: 10.1021/acs.est.9b01769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
California methane (CH4) emissions are quantified for three years from two tower networks and one aircraft campaign. We used backward trajectory simulations and a mesoscale Bayesian inverse model, initialized by three inventories, to achieve the emission quantification. Results show total statewide CH4 emissions of 2.05 ± 0.26 (at 95% confidence) Tg/yr, which is 1.14 to 1.47 times greater than the anthropogenic emission estimates by California Air Resource Board (CARB). Some of differences could be biogenic emissions, superemitter point sources, and other episodic emissions which may not be completely included in the CARB inventory. San Joaquin Valley (SJV) has the largest CH4 emissions (0.94 ± 0.18 Tg/yr), followed by the South Coast Air Basin, the Sacramento Valley, and the San Francisco Bay Area at 0.39 ± 0.18, 0.21 ± 0.04, and 0.16 ± 0.05 Tg/yr, respectively. The dairy and oil/gas production sources in the SJV contribute 0.44 ± 0.36 and 0.22 ± 0.23 Tg CH4/yr, respectively. This study has important policy implications for regulatory programs, as it provides a thorough multiyear evaluation of the emissions inventory using independent atmospheric measurements and investigates the utility of a complementary multiplatform approach in understanding the spatial and temporal patterns of CH4 emissions in the state and identifies opportunities for the expansion and applications of the monitoring network.
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Affiliation(s)
- Yu Yan Cui
- California Air Resources Board , 1001 I Street , Sacramento , California 95814 , United States
| | - Abhilash Vijayan
- California Air Resources Board , 1001 I Street , Sacramento , California 95814 , United States
| | - Matthias Falk
- California Air Resources Board , 1001 I Street , Sacramento , California 95814 , United States
| | - Ying-Kuang Hsu
- California Air Resources Board , 1001 I Street , Sacramento , California 95814 , United States
| | - Dazhong Yin
- California Air Resources Board , 1001 I Street , Sacramento , California 95814 , United States
| | - Xue Meng Chen
- California Air Resources Board , 1001 I Street , Sacramento , California 95814 , United States
| | - Zhan Zhao
- California Air Resources Board , 1001 I Street , Sacramento , California 95814 , United States
| | - Jeremy Avise
- California Air Resources Board , 1001 I Street , Sacramento , California 95814 , United States
- Department of Civil and Environmental Engineering , Washington State University , Pullman , Washington 99163 , United States
| | - Yanju Chen
- California Air Resources Board , 1001 I Street , Sacramento , California 95814 , United States
| | - Kristal Verhulst
- NASA Jet Propulsion Laboratory , California Institute of Technology , Pasadena , California 91109 , United States
| | - Riley Duren
- NASA Jet Propulsion Laboratory , California Institute of Technology , Pasadena , California 91109 , United States
| | - Vineet Yadav
- NASA Jet Propulsion Laboratory , California Institute of Technology , Pasadena , California 91109 , United States
| | - Charles Miller
- NASA Jet Propulsion Laboratory , California Institute of Technology , Pasadena , California 91109 , United States
| | - Ray Weiss
- Scripps Institution of Oceanography , University of California , San Diego , La Jolla , California 92037 , United States
| | - Ralph Keeling
- Scripps Institution of Oceanography , University of California , San Diego , La Jolla , California 92037 , United States
| | - Jooil Kim
- Scripps Institution of Oceanography , University of California , San Diego , La Jolla , California 92037 , United States
| | - Laura T Iraci
- Earth Science Division , NASA Ames Research Center , Moffett Field , California 94035 , United States
| | - Tomoaki Tanaka
- Earth Science Division , NASA Ames Research Center , Moffett Field , California 94035 , United States
- Japan Weather Association , Tokyo , Japan
| | - Matthew S Johnson
- Earth Science Division , NASA Ames Research Center , Moffett Field , California 94035 , United States
| | - Eric A Kort
- Department of Physics , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Laura Bianco
- Physical Sciences Division , NOAA Earth System Research Laboratory , Boulder , Colorado 80305 , United States
- The Cooperative Institute for Research in Environmental Sciences , University of Colorado Boulder , Boulder , Colorado 80305 , United States
| | - Marc L Fischer
- Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Kenneth Stroud
- California Air Resources Board , 1001 I Street , Sacramento , California 95814 , United States
| | - Jorn Herner
- California Air Resources Board , 1001 I Street , Sacramento , California 95814 , United States
| | - Bart Croes
- California Air Resources Board , 1001 I Street , Sacramento , California 95814 , United States
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7
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Barrera YD, Nehrkorn T, Hegarty J, Sargent M, Benmergui J, Gottlieb E, Wofsy SC, DeCola P, Hutyra L, Jones T. Using Lidar Technology To Assess Urban Air Pollution and Improve Estimates of Greenhouse Gas Emissions in Boston. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:8957-8966. [PMID: 31265266 DOI: 10.1021/acs.est.9b00650] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Simulation of the planetary boundary layer (PBL) is key for forecasting air quality and estimating greenhouse gas (GHG) emissions in cities. Here we conducted the first long-term and continuous study of PBL heights (PBLHs) in Boston, MA, using a compact lidar instrument. We developed an image recognition algorithm to estimate PBLHs from the lidar measurements and evaluated simulations of the PBL from seven numerical weather prediction (NWP) model versions, which showed different systematic errors and variability in simulating the PBLHs (discrepancies from -2.5 to 4.0 km). The NWP model with the best overall agreement for the fully developed PBL had R2 = 0.72 and a bias of only 0.128 km. However, this model predicted a notable number of anomalously high carbon dioxide concentrations at ground stations, because it occasionally significantly underestimated the PBLH. We also developed a novel method that combines lidar data with footprints from a Lagrangian particle dispersion model to identify long-range transport of air pollution in the nocturnal residual layer. Our framework was powerful in evaluating the performance of models used to estimate air pollution and GHG emissions in cities, which is critical to track progress on emission reduction targets and guide effective policies.
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Affiliation(s)
- Yanina D Barrera
- School of Engineering and Applied Sciences and Department of Earth and Planetary Sciences , Harvard University , Cambridge , Massachusetts 02138 , United States
| | - Thomas Nehrkorn
- Atmospheric and Environmental Research, Inc. , Lexington , Massachusetts 02421 , United States
| | - Jennifer Hegarty
- Atmospheric and Environmental Research, Inc. , Lexington , Massachusetts 02421 , United States
| | - Maryann Sargent
- School of Engineering and Applied Sciences and Department of Earth and Planetary Sciences , Harvard University , Cambridge , Massachusetts 02138 , United States
| | - Joshua Benmergui
- School of Engineering and Applied Sciences and Department of Earth and Planetary Sciences , Harvard University , Cambridge , Massachusetts 02138 , United States
| | - Elaine Gottlieb
- School of Engineering and Applied Sciences and Department of Earth and Planetary Sciences , Harvard University , Cambridge , Massachusetts 02138 , United States
| | - Steven C Wofsy
- School of Engineering and Applied Sciences and Department of Earth and Planetary Sciences , Harvard University , Cambridge , Massachusetts 02138 , United States
| | - Phil DeCola
- Sigma Space Corporation , Lanham , Maryland 20706 , United States
- Department of Atmospheric and Oceanic Sciences , University of Maryland , College Park , Maryland 20742 , United States
| | - Lucy Hutyra
- Department of Earth and Environment , Boston University , Boston , Massachusetts 02215 , United States
| | - Taylor Jones
- School of Engineering and Applied Sciences and Department of Earth and Planetary Sciences , Harvard University , Cambridge , Massachusetts 02138 , United States
- Sigma Space Corporation , Lanham , Maryland 20706 , United States
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8
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Mousavi A, Sowlat MH, Hasheminassab S, Polidori A, Sioutas C. Spatio-temporal trends and source apportionment of fossil fuel and biomass burning black carbon (BC) in the Los Angeles Basin. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 640-641:1231-1240. [PMID: 30021288 DOI: 10.1016/j.scitotenv.2018.06.022] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 05/31/2018] [Accepted: 06/02/2018] [Indexed: 06/08/2023]
Abstract
In this study, we evaluated the spatial and temporal trends of black carbon (BC) in the Los Angeles Basin between 2012-2013 and 2016-2017. BC concentrations were measured in seven wavelengths using Aethalometers (AE33) at four sites, including central Los Angeles (CELA), Anaheim, Fontana, and Riverside. Sources of BC were quantified using the equivalent black carbon (EBC) model. Results indicate that total BC concentrations nearly doubled in colder period compared to the warm period. Source apportionment results revealed that fossil fuel combustion has higher annual contributions (ranging from 82% in Riverside to 91% in CELA) than biomass burning (ranging from 9.3% in CELA to 18.7% in Riverside) to the total BC concentrations at all sites. This trend was more clearly observed at the sites closer to major freeways, such as CELA and Anaheim. The relative contribution of fossil fuel to total BC concentrations was higher in the warm period, whereas biomass burning had higher contributions in the colder period. The diurnal variation of fossil-fuel-originated BC (BCff) to the total BC concentrations revealed major rises during the traffic rush hours, especially in the warm period. In contrast, the fraction of BC originating from biomass burning (BCbb) peaked at nighttime, particularly in the cold period, reaching values as high as 25-30% of total BC concentration. Moreover, we observed a clear decrease in both absolute BC concentrations as well as relative contributions of BCff to total BC concentrations from 2012-2013 to 2016-2017, which can be attributed to the implementation of strict regulations in California to reduce transportation-related PM emissions. Results from the present study suggest that as these regulations become increasingly stricter, the relative contributions of traffic sources to BC also decrease, thereby making the impact of non-fossil fuel combustion sources, such as biomass burning, to the overall BC levels more significant.
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Affiliation(s)
- Amirhosein Mousavi
- University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
| | - Mohammad H Sowlat
- University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
| | | | - Andrea Polidori
- South Coast Air Quality Management District, Diamond Bar, CA, USA.
| | - Constantinos Sioutas
- University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
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9
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The Effect of Aerosol Radiative Heating on Turbulence Statistics and Spectra in the Atmospheric Convective Boundary Layer: A Large-Eddy Simulation Study. ATMOSPHERE 2018. [DOI: 10.3390/atmos9090347] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Turbulence statistics and spectra in a radiatively heated convective boundary layer (CBL) under aerosol pollution conditions are less investigated than their counterparts in the clear CBL. In this study, a large-eddy simulation (LES) coupled with an aerosol radiative transfer model is employed to determine the impact of aerosol radiative heating on CBL turbulence statistics. One-dimensional velocity spectra and velocity–temperature cospectra are invoked to characterize the turbulence flow in the CBL with varying aerosol pollution conditions. The results show that aerosol heating makes the profiles of turbulent heat flux curvilinear, while the total (turbulent plus radiative) heat flux profile retains the linear relationship with height throughout the CBL. The horizontal and vertical velocity variances are reduced significantly throughout the radiatively heated CBL with increased aerosol optical depth (AOD). The potential temperature variance is also reduced, especially in the entrainment zone and near the surface. The velocity spectral density tends to be smaller overall, and the peak of the velocity spectra is shifted toward larger wavenumbers as AOD increases. This shift reveals that the energy-containing turbulent eddies become smaller, which is also supported by visual inspection of the vertical velocity pattern over horizontal planes. The modified CBL turbulence scales for velocity and temperature are found to be applicable for normalizing the corresponding profiles, indicating that a correction factor for aerosol radiative heating is needed for capturing the general features of the CBL structure in the presence of aerosol radiative heating.
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10
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Verhulst KR, Karion A, Kim J, Salameh PK, Keeling RF, Newman S, Miller J, Sloop C, Pongetti T, Rao P, Wong C, Hopkins FM, Yadav V, Weiss RF, Duren RM, Miller CE. Carbon dioxide and methane measurements from the Los Angeles Megacity Carbon Project - Part 1: calibration, urban enhancements, and uncertainty estimates. ATMOSPHERIC CHEMISTRY AND PHYSICS 2017. [PMID: 30984251 DOI: 10.5194/acp-2016-850] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
We report continuous surface observations of carbon dioxide (CO2) and methane (CH4) from the Los Angeles (LA) Megacity Carbon Project during 2015. We devised a calibration strategy, methods for selection of background air masses, calculation of urban enhancements, and a detailed algorithm for estimating uncertainties in urban-scale CO2 and CH4 measurements. These methods are essential for understanding carbon fluxes from the LA megacity and other complex urban environments globally. We estimate background mole fractions entering LA using observations from four "extra-urban" sites including two "marine" sites located south of LA in La Jolla (LJO) and offshore on San Clemente Island (SCI), one "continental" site located in Victorville (VIC), in the high desert northeast of LA, and one "continental/mid-troposphere" site located on Mount Wilson (MWO) in the San Gabriel Mountains. We find that a local marine background can be established to within ~1 ppm CO2 and ~10 ppb CH4 using these local measurement sites. Overall, atmospheric carbon dioxide and methane levels are highly variable across Los Angeles. "Urban" and "suburban" sites show moderate to large CO2 and CH4 enhancements relative to a marine background estimate. The USC (University of Southern California) site near downtown LA exhibits median hourly enhancements of ~20 ppm CO2 and ~150 ppb CH4 during 2015 as well as ~15 ppm CO2 and ~80 ppb CH4 during mid-afternoon hours (12:00-16:00 LT, local time), which is the typical period of focus for flux inversions. The estimated measurement uncertainty is typically better than 0.1 ppm CO2 and 1 ppb CH4 based on the repeated standard gas measurements from the LA sites during the last 2 years, similar to Andrews et al. (2014). The largest component of the measurement uncertainty is due to the single-point calibration method; however, the uncertainty in the background mole fraction is much larger than the measurement uncertainty. The background uncertainty for the marine background estimate is ~10 and ~15 % of the median mid-afternoon enhancement near downtown LA for CO2 and CH4, respectively. Overall, analytical and background uncertainties are small relative to the local CO2 and CH4 enhancements; however, our results suggest that reducing the uncertainty to less than 5 % of the median mid-afternoon enhancement will require detailed assessment of the impact of meteorology on background conditions.
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Affiliation(s)
- Kristal R Verhulst
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- University of California, Los Angeles, Joint Institute for Regional Earth System Science and Engineering, Los Angeles, CA, USA
| | - Anna Karion
- National Institute of Standards and Technology (NIST), Gaithersburg, MD, USA
| | - Jooil Kim
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Peter K Salameh
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Ralph F Keeling
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Sally Newman
- California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, USA
| | - John Miller
- NOAA/ESRL/GMD, Boulder, CO, USA
- CIRES, University of Colorado, Boulder, Boulder, CO, USA
| | | | - Thomas Pongetti
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Preeti Rao
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Clare Wong
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, USA
| | - Francesca M Hopkins
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Vineet Yadav
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Ray F Weiss
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Riley M Duren
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Charles E Miller
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
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Verhulst KR, Karion A, Kim J, Salameh PK, Keeling RF, Newman S, Miller J, Sloop C, Pongetti T, Rao P, Wong C, Hopkins FM, Yadav V, Weiss RF, Duren RM, Miller CE. Carbon dioxide and methane measurements from the Los Angeles Megacity Carbon Project - Part 1: calibration, urban enhancements, and uncertainty estimates. ATMOSPHERIC CHEMISTRY AND PHYSICS 2017; 17:10.5194/acp-17-8313-2017. [PMID: 30984251 PMCID: PMC6459414 DOI: 10.5194/acp-17-8313-2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
We report continuous surface observations of carbon dioxide (CO2) and methane (CH4) from the Los Angeles (LA) Megacity Carbon Project during 2015. We devised a calibration strategy, methods for selection of background air masses, calculation of urban enhancements, and a detailed algorithm for estimating uncertainties in urban-scale CO2 and CH4 measurements. These methods are essential for understanding carbon fluxes from the LA megacity and other complex urban environments globally. We estimate background mole fractions entering LA using observations from four "extra-urban" sites including two "marine" sites located south of LA in La Jolla (LJO) and offshore on San Clemente Island (SCI), one "continental" site located in Victorville (VIC), in the high desert northeast of LA, and one "continental/mid-troposphere" site located on Mount Wilson (MWO) in the San Gabriel Mountains. We find that a local marine background can be established to within ~1 ppm CO2 and ~10 ppb CH4 using these local measurement sites. Overall, atmospheric carbon dioxide and methane levels are highly variable across Los Angeles. "Urban" and "suburban" sites show moderate to large CO2 and CH4 enhancements relative to a marine background estimate. The USC (University of Southern California) site near downtown LA exhibits median hourly enhancements of ~20 ppm CO2 and ~150 ppb CH4 during 2015 as well as ~15 ppm CO2 and ~80 ppb CH4 during mid-afternoon hours (12:00-16:00 LT, local time), which is the typical period of focus for flux inversions. The estimated measurement uncertainty is typically better than 0.1 ppm CO2 and 1 ppb CH4 based on the repeated standard gas measurements from the LA sites during the last 2 years, similar to Andrews et al. (2014). The largest component of the measurement uncertainty is due to the single-point calibration method; however, the uncertainty in the background mole fraction is much larger than the measurement uncertainty. The background uncertainty for the marine background estimate is ~10 and ~15 % of the median mid-afternoon enhancement near downtown LA for CO2 and CH4, respectively. Overall, analytical and background uncertainties are small relative to the local CO2 and CH4 enhancements; however, our results suggest that reducing the uncertainty to less than 5 % of the median mid-afternoon enhancement will require detailed assessment of the impact of meteorology on background conditions.
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Affiliation(s)
- Kristal R. Verhulst
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- University of California, Los Angeles, Joint Institute for Regional Earth System Science and Engineering, Los Angeles, CA, USA
| | - Anna Karion
- National Institute of Standards and Technology (NIST), Gaithersburg, MD, USA
| | - Jooil Kim
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Peter K. Salameh
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Ralph F. Keeling
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Sally Newman
- California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, USA
| | - John Miller
- NOAA/ESRL/GMD, Boulder, CO, USA
- CIRES, University of Colorado, Boulder, Boulder, CO, USA
| | | | - Thomas Pongetti
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Preeti Rao
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Clare Wong
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, USA
| | - Francesca M. Hopkins
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Vineet Yadav
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Ray F. Weiss
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Riley M. Duren
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Charles E. Miller
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
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