Publications by authors named "David G Streets"

43 Publications

Analyzing the spatio-temporal variation of the CO emissions from district heating systems with "Coal-to-Gas" transition: Evidence from GTWR model and satellite data in China.

Sci Total Environ 2021 Sep 3;803:150083. Epub 2021 Sep 3.

Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439, United States.

Understanding the spatio-temporal heterogeneous effects of socioeconomic and meteorological factors on CO emissions from combinations of different district heating systems with "Coal-to-Gas" transition can contribute to the development of future low-carbon energy systems that are efficient and effective. This work downscales city-level CO emissions to a 3 × 3 km gridded level in northern China during 2012 to 2018. By employing the Geographically and Temporally Weighted Regression (GTWR) model, nighttime light (NTL) data are adopted as a proxy of the level of urbanization, and the Temperature-Humidity-Wind (THW) Index is used as a proxy of meteorological factors in the downscaling model. The results show that, for more than 85% of the cities, urbanization significantly enhances the CO emissions of district heating systems, while the THW Index shows negative impacts on CO emissions. Significant spatial and temporal heterogeneity exists. The grids with the highest CO emissions from coal-fired boilers (grids with annual variation >0.59 Gg CO/year) are mainly located in nonurban areas of the two megacities Beijing and Tianjin and also in the capital cities of each province. Urbanization has larger effects on the CO emissions of natural gas-fired boilers than of coal-fired boilers and combined heat and power (CHP). The average growth rate of CO emissions of gas-fired boilers in the urban areas of the study regions was approximately 4.7 times that of nonurban areas. The spatio-temporal heterogeneous impacts of urbanization on CO emissions should therefore be considered in future discussions of clean heating policies and climate response strategies.
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http://dx.doi.org/10.1016/j.scitotenv.2021.150083DOI Listing
September 2021

TROPOMI NO in the United States: A Detailed Look at the Annual Averages, Weekly Cycles, Effects of Temperature, and Correlation With Surface NO Concentrations.

Earths Future 2021 Apr 2;9(4):e2020EF001665. Epub 2021 Apr 2.

Energy Systems Division Argonne National Laboratory Argonne IL USA.

Observing the spatial heterogeneities of NO air pollution is an important first step in quantifying NO emissions and exposures. This study investigates the capabilities of the Tropospheric Monitoring Instrument (TROPOMI) in observing the spatial and temporal patterns of NO pollution in the continental United States. The unprecedented sensitivity of the sensor can differentiate the fine-scale spatial heterogeneities in urban areas, such as emissions related to airport/shipping operations and high traffic, and the relatively small emission sources in rural areas, such as power plants and mining operations. We then examine NO columns by day-of-the-week and find that Saturday and Sunday concentrations are 16% and 24% lower respectively, than during weekdays. We also analyze the correlation of daily maximum 2-m temperatures and NO column amounts and find that NO is larger on the hottest days (>32°C) as compared to warm days (26°C-32°C), which is in contrast to a general decrease in NO with increasing temperature at moderate temperatures. Finally, we demonstrate that a linear regression fit of 2019 annual TROPOMI NO data to annual surface-level concentrations yields relatively strong correlation (  = 0.66). These new developments make TROPOMI NO satellite data advantageous for policymakers and public health officials, who request information at high spatial resolution and short timescales, in order to assess, devise, and evaluate regulations.
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http://dx.doi.org/10.1029/2020EF001665DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8047911PMC
April 2021

Natural gas shortages during the "coal-to-gas" transition in China have caused a large redistribution of air pollution in winter 2017.

Proc Natl Acad Sci U S A 2020 12 23;117(49):31018-31025. Epub 2020 Nov 23.

Minerva Research Group, Max Planck Institute for Chemistry, 55128 Mainz, Germany;

The Chinese "coal-to-gas" and "coal-to-electricity" strategies aim at reducing dispersed coal consumption and related air pollution by promoting the use of clean and low-carbon fuels in northern China. Here, we show that on top of meteorological influences, the effective emission mitigation measures achieved an average decrease of fine particulate matter (PM) concentrations of ∼14% in Beijing and surrounding areas (the "2+26" pilot cities) in winter 2017 compared to the same period of 2016, where the dispersed coal control measures contributed ∼60% of the total PM reductions. However, the localized air quality improvement was accompanied by a contemporaneous ∼15% upsurge of PM concentrations over large areas in southern China. We find that the pollution transfer that resulted from a shift in emissions was of a high likelihood caused by a natural gas shortage in the south due to the coal-to-gas transition in the north. The overall shortage of natural gas greatly jeopardized the air quality benefits of the coal-to-gas strategy in winter 2017 and reflects structural challenges and potential threats in China's clean-energy transition.
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http://dx.doi.org/10.1073/pnas.2007513117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7733853PMC
December 2020

Disentangling the impact of the COVID-19 lockdowns on urban NO from natural variability.

Geophys Res Lett 2020 Aug 17:e2020GL089269. Epub 2020 Aug 17.

Energy Systems Division Argonne National Laboratory Lemont IL U.S.

TROPOMI satellite data show substantial drops in nitrogen dioxide (NO) during COVID-19 physical distancing. To attribute NO changes to NO emissions changes over short timescales, one must account for meteorology. We find that meteorological patterns were especially favorable for low NO in much of the U.S. in spring 2020, complicating comparisons with spring 2019. Meteorological variations between years can cause column NO differences of ~15% over monthly timescales. After accounting for sun angle and meteorological considerations, we calculate that NO drops ranged between 9.2 - 43.4% among twenty cities in North America, with a median of 21.6%. Of the studied cities, largest NO drops (>30%) were in San Jose, Los Angeles, and Toronto, and smallest drops (<12%) were in Miami, Minneapolis, and Dallas. These normalized NO changes can be used to highlight locations with greater activity changes and better understand the sources contributing to adverse air quality in each city.
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http://dx.doi.org/10.1029/2020GL089269DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7461033PMC
August 2020

Enhanced Capabilities of TROPOMI NO: Estimating NO from North American Cities and Power Plants.

Environ Sci Technol 2019 Nov 25;53(21):12594-12601. Epub 2019 Oct 25.

Royal Netherlands Meteorological Institute (KNMI) , De Bilt 3730 AE , The Netherlands.

The TROPOspheric Monitoring Instrument (TROPOMI) is used to derive top-down NO emissions for two large power plants and three megacities in North America. We first re-process the vertical column NO with an improved air mass factor to correct for a known systematic low bias in the operational retrieval near urban centers. For the two power plants, top-down NO emissions agree to within 10% of the emissions reported by the power plants. We then derive top-down NO emissions rates for New York City, Chicago, and Toronto, and compare them to projected bottom-up emissions inventories. In this analysis of 2018 NO emissions, we find a +22% overestimate for New York City, a -21% underestimate in Toronto, and good agreement in Chicago in the projected bottom-up inventories when compared to the top-down emissions. Top-down NO emissions also capture intraseasonal variability, such as the weekday versus weekend effect (emissions are +45% larger on weekdays versus weekends in Chicago). Finally, we demonstrate the enhanced capabilities of TROPOMI, which allow us to derive a NO emissions rate for Chicago using a single overpass on July 7, 2018. The large signal-to-noise ratio of TROPOMI is well-suited for estimating NO emissions from relatively small sources and for sub-seasonal timeframes.
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http://dx.doi.org/10.1021/acs.est.9b04488DOI Listing
November 2019

Exploiting OMI NO satellite observations to infer fossil-fuel CO emissions from U.S. megacities.

Sci Total Environ 2019 Dec 8;695:133805. Epub 2019 Aug 8.

Energy Systems Division, Argonne National Laboratory, Lemont, IL, USA; Consortium for Advanced Science and Engineering, University of Chicago, Chicago, IL, USA.

Fossil-fuel CO emissions and their trends in eight U.S. megacities during 2006-2017 are inferred by combining satellite-derived NO emissions with bottom-up city-specific NO-to-CO emission ratios. A statistical model is fit to a collection NO plumes observed from the Ozone Monitoring Instrument (OMI), and is used to calculate top-down NO emissions. Decreases in OMI-derived NO emissions are observed across the eight cities from 2006 to 2017 (-17% in Miami to -58% in Los Angeles), and are generally consistent with long-term trends of bottom-up inventories (-25% in Miami to -49% in Los Angeles), but there are some interannual discrepancies. City-specific NO-to-CO emission ratios, used to calculate inferred CO, are estimated through annual bottom-up inventories of NO and CO emissions disaggregated to 1 × 1 km resolution. Over the study period, NO-to-CO emission ratios have decreased by ~40% nationwide (-24% to -51% for our studied cities), which is attributed to a faster reduction in NO when compared to CO due to policy regulations and fuel type shifts. Combining top-down NO emissions and bottom-up NO-to-CO emission ratios, annual fossil-fuel CO emissions are derived. Inferred OMI-based top-down CO emissions trends vary between +7% in Dallas to -31% in Phoenix. For 2017, we report annual fossil-fuel CO emissions to be: Los Angeles 113 ± 49 Tg/yr; New York City 144 ± 62 Tg/yr; and Chicago 55 ± 24 Tg/yr. A study in the Los Angeles area, using independent methods, reported a 2013-2016 average CO emissions rate of 104 Tg/yr and 120 Tg/yr, which suggests that the CO emissions from our method are in good agreement with other studies' top-down estimates. We anticipate future remote sensing instruments - with better spatial and temporal resolution - will better constrain the NO-to-CO ratio and reduce the uncertainty in our method.
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http://dx.doi.org/10.1016/j.scitotenv.2019.133805DOI Listing
December 2019

Evaluation of China's Environmental Pressures Based on Satellite NO Observation and the Extended STIRPAT Model.

Int J Environ Res Public Health 2019 04 26;16(9). Epub 2019 Apr 26.

Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439, USA.

China's rapid urbanization and industrialization have affected the spatiotemporal patterns of nitrogen dioxide (NO) pollution, which has led to greater environmental pressures. In order to mitigate the environmental pressures caused by NO pollution, it is of vital importance to investigate the influencing factors. We first obtained data for NO pollution at the city level using satellite observation techniques and analyzed its spatial distribution. Next, we introduced a theoretical framework, an extended stochastic impacts by regression on population, affluence, and technology (STIRPAT) model, to quantify the relationship between NO pollution and its contributing natural and socio-economic factors. The results are as follows. Cities with high NO pollution are mainly concentrated in the North China Plain. On the contrary, southwestern cities are characterized by low NO pollution. In addition, we find that population, per capita gross domestic product, the share of the secondary industry, ambient air pressures, total nighttime light data, and urban road area have a positive impact on NO pollution. In contrast, increases in the normalized difference vegetation index (NDVI), relative humidity, temperature, and wind speed may reduce NO pollution. These empirical results should help the government to effectively and efficiently implement further emission reductions and energy saving policies in Chinese cities in a bid to mitigate the environmental pressures.
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http://dx.doi.org/10.3390/ijerph16091487DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6539091PMC
April 2019

Analysis of the origins of black carbon and carbon monoxide transported to Beijing, Tianjin, and Hebei in China.

Sci Total Environ 2019 Feb 21;653:1364-1376. Epub 2018 Sep 21.

Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439, USA.

A novel back-trajectory approach was adopted to determine the origins of black carbon (BC) and carbon monoxide (CO) transported to Beijing, Tianjin and Hebei. Results showed that the transport efficiency was controlled mainly by mid-latitude westerlies in winter, the South Asian monsoon in summer and prevailing westerly and northwesterly winds in spring and autumn. Hebei was identified as the most important source region of both BC (respectively accounting for 55% and 49%) and CO (39% and 38%) transported to Beijing and Tianjin. Inner Mongolia contributed more to the effective emission intensity (EEI) in winter than in summer for both BC and CO transported to Beijing and Tianjin. Shandong was responsible for higher EEI in summer than in winter. The six provinces making the greatest contributions to BC transported to Hebei were Shandong (19%), Shanxi (19%), Inner Mongolia (17%), Beijing (11%), Henan (11%), and Tianjin (10%), whereas those making the greatest contributions to CO transported to Hebei were Shandong (20%), Inner Mongolia (10%), Tianjin (9%), Henan (9%), Shanxi (9%), and Beijing (8%). In summary, Hebei, Inner Mongolia, Shandong, Tianjin and Shanxi were determined as the dominant source regions of not only BC but also CO transported to Beijing. Hebei, Shandong, Beijing, Inner Mongolia, Henan, Liaoning and Shanxi were relatively important source regions for Tianjin. Shandong, Shanxi, Inner Mongolia, Beijing, Henan, Tianjin, Liaoning, Jiangsu and Anhui were the main source regions for Hebei. Residential and industrial sectors were the dominant sectors for BC and CO transported to the receptors, respectively. These results are consistent with the results of previous studies. Finally, comparing the observed ΔBC/ΔCO ratio with the enhancement ratio of the EEI of BC with that of CO (ΔEEI/ΔEEI) at Miyun site, we further confirmed that the EEI can be used to represent the amounts of BC and CO reaching receptors.
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http://dx.doi.org/10.1016/j.scitotenv.2018.09.274DOI Listing
February 2019

Historical releases of mercury to air, land, and water from coal combustion.

Sci Total Environ 2018 Feb 28;615:131-140. Epub 2017 Sep 28.

Harvard John A. Paulson School of Engineering and Applied Sciences, Cambridge, MA 02138, United States; Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA 02115, United States.

Coal combustion is one of the largest contemporary sources of anthropogenic mercury (Hg). It releases geologically sequestered Hg to the atmosphere, and fly ash can contaminate terrestrial and aquatic systems. We estimate that coal combustion has released a cumulative total of 38.0 (14.8-98.9, 80% C.I.) Gg (gigagrams, 10g or thousand tonnes) of Hg to air, land, and water up to the year 2010, most of which (97%) has occurred since 1850. The rate of release has grown by two orders of magnitude from 0.01Ggyr in 1850 to 1Ggyr in 2010. Geographically, Asia and Europe each account for 32% of cumulative releases and an additional 18% is from North America. About 26.3 (10.2-68.3) Gg, 71% of the total, were directly emitted to the atmosphere, mostly from the industrial (45%) and power generation (36%) sectors, while the remainder was disposed of to land and water bodies. While Europe and North America were the major contributing regions until 1950, Asia has surpassed both in recent decades. By 2010, Asia was responsible for 69% of the total releases of Hg from coal combustion to the environment. Control technologies installed on major emitting sources capture mainly particulate and divalent Hg, and therefore the fraction of elemental Hg in emissions from coal combustion has increased over time from 0.46 in 1850 to 0.61 in 2010. About 11.8 (4.6-30.6) Gg of Hg, 31% of the total, have been transferred to land and water bodies through the disposal or utilization of Hg-containing combustion waste and collected fly ash/FGD waste; approximately 8.8Gg of this Hg have simply been discarded to waste piles or ash ponds or rivers.
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http://dx.doi.org/10.1016/j.scitotenv.2017.09.207DOI Listing
February 2018

Total Mercury Released to the Environment by Human Activities.

Environ Sci Technol 2017 Jun 9;51(11):5969-5977. Epub 2017 May 9.

School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States.

We estimate that a cumulative total of 1540 (1060-2800) Gg (gigagrams, 10 grams or thousand tonnes) of mercury (Hg) have been released by human activities up to 2010, 73% of which was released after 1850. Of this liberated Hg, 470 Gg were emitted directly into the atmosphere, and 74% of the air emissions were elemental Hg. Cumulatively, about 1070 Gg were released to land and water bodies. Though annual releases of Hg have been relatively stable since 1880 at 8 ± 2 Gg, except for wartime, the distributions of those releases among source types, world regions, and environmental media have changed dramatically. Production of Hg accounts for 27% of cumulative Hg releases to the environment, followed by silver production (24%) and chemicals manufacturing (12%). North America (30%), Europe (27%), and Asia (16%) have experienced the largest releases. Biogeochemical modeling shows a 3.2-fold increase in the atmospheric burden relative to 1850 and a contemporary atmospheric reservoir of 4.57 Gg, both of which agree well with observational constraints. We find that approximately 40% (390 Gg) of the Hg discarded to land and water must be sequestered at contaminated sites to maintain consistency with recent declines in atmospheric Hg concentrations.
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http://dx.doi.org/10.1021/acs.est.7b00451DOI Listing
June 2017

Transboundary health impacts of transported global air pollution and international trade.

Nature 2017 03;543(7647):705-709

Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, Beijing 100084, China.

Millions of people die every year from diseases caused by exposure to outdoor air pollution. Some studies have estimated premature mortality related to local sources of air pollution, but local air quality can also be affected by atmospheric transport of pollution from distant sources. International trade is contributing to the globalization of emission and pollution as a result of the production of goods (and their associated emissions) in one region for consumption in another region. The effects of international trade on air pollutant emissions, air quality and health have been investigated regionally, but a combined, global assessment of the health impacts related to international trade and the transport of atmospheric air pollution is lacking. Here we combine four global models to estimate premature mortality caused by fine particulate matter (PM) pollution as a result of atmospheric transport and the production and consumption of goods and services in different world regions. We find that, of the 3.45 million premature deaths related to PM pollution in 2007 worldwide, about 12 per cent (411,100 deaths) were related to air pollutants emitted in a region of the world other than that in which the death occurred, and about 22 per cent (762,400 deaths) were associated with goods and services produced in one region for consumption in another. For example, PM pollution produced in China in 2007 is linked to more than 64,800 premature deaths in regions other than China, including more than 3,100 premature deaths in western Europe and the USA; on the other hand, consumption in western Europe and the USA is linked to more than 108,600 premature deaths in China. Our results reveal that the transboundary health impacts of PM pollution associated with international trade are greater than those associated with long-distance atmospheric pollutant transport.
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http://dx.doi.org/10.1038/nature21712DOI Listing
March 2017

Satellite NO retrievals suggest China has exceeded its NO reduction goals from the twelfth Five-Year Plan.

Sci Rep 2016 10 27;6:35912. Epub 2016 Oct 27.

Argonne National Laboratory, Energy Systems Division, Argonne, IL 60439, USA.

China's twelfth Five-Year Plan included pollution control measures with a goal of reducing national emissions of nitrogen oxides (NO) by 10% by 2015 compared with 2010. Multiple linear regression analysis was used on 11-year time series of all nitrogen dioxide (NO) pixels from the Ozone Monitoring Instrument (OMI) over 18 NO hotspots in China. The regression analysis accounted for variations in meteorology, pixel resolution, seasonal effects, weekday variability and year-to-year variability. The NO trends suggested that there was an increase in NO columns in most areas from 2005 to around 2011 which was followed by a strong decrease continuing through 2015. The satellite results were in good agreement with the annual official NO emission inventories which were available up until 2014. This shows the value of evaluating trends in emission inventories using satellite retrievals. It further shows that recent control strategies were effective in reducing emissions and that recent economic transformations in China may be having an effect on NO columns. Satellite information for 2015 suggests that emissions have continued to decrease since the latest inventories available and have surpassed the goals of the twelfth Five-Year Plan.
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http://dx.doi.org/10.1038/srep35912DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5082360PMC
October 2016

Impacts of the Minamata convention on mercury emissions and global deposition from coal-fired power generation in Asia.

Environ Sci Technol 2015 May 16;49(9):5326-35. Epub 2015 Apr 16.

†Engineering Systems Division, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.

We explore implications of the United Nations Minamata Convention on Mercury for emissions from Asian coal-fired power generation, and resulting changes to deposition worldwide by 2050. We use engineering analysis, document analysis, and interviews to construct plausible technology scenarios consistent with the Convention. We translate these scenarios into emissions projections for 2050, and use the GEOS-Chem model to calculate global mercury deposition. Where technology requirements in the Convention are flexibly defined, under a global energy and development scenario that relies heavily on coal, we project ∼90 and 150 Mg·y(-1) of avoided power sector emissions for China and India, respectively, in 2050, compared to a scenario in which only current technologies are used. Benefits of this avoided emissions growth are primarily captured regionally, with projected changes in annual average gross deposition over China and India ∼2 and 13 μg·m(-2) lower, respectively, than the current technology case. Stricter, but technologically feasible, mercury control requirements in both countries could lead to a combined additional 170 Mg·y(-1) avoided emissions. Assuming only current technologies but a global transition away from coal avoids 6% and 36% more emissions than this strict technology scenario under heavy coal use for China and India, respectively.
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http://dx.doi.org/10.1021/acs.est.5b00074DOI Listing
May 2015

Light absorption properties and radiative effects of primary organic aerosol emissions.

Environ Sci Technol 2015 Apr 9;49(8):4868-77. Epub 2015 Apr 9.

#Department of Chemical and Biochemical Engineering, The University of Iowa, 4133 Seamans Center, Iowa City, Iowa 52242, United States.

Organic aerosols (OAs) in the atmosphere affect Earth's energy budget by not only scattering but also absorbing solar radiation due to the presence of the so-called "brown carbon" (BrC) component. However, the absorptivities of OAs are not represented or are poorly represented in current climate and chemical transport models. In this study, we provide a method to constrain the BrC absorptivity at the emission inventory level using recent laboratory and field observations. We review available measurements of the light-absorbing primary OA (POA), and quantify the wavelength-dependent imaginary refractive indices (kOA, the fundamental optical parameter determining the particle's absorptivity) and their uncertainties for the bulk POA emitted from biomass/biofuel, lignite, propane, and oil combustion sources. In particular, we parametrize the kOA of biomass/biofuel combustion sources as a function of the black carbon (BC)-to-OA ratio, indicating that the absorptive properties of POA depend strongly on burning conditions. The derived fuel-type-based kOA profiles are incorporated into a global carbonaceous aerosol emission inventory, and the integrated kOA values of sectoral and total POA emissions are presented. Results of a simple radiative transfer model show that the POA absorptivity warms the atmosphere significantly and leads to ∼27% reduction in the amount of the net global average POA cooling compared to results from the nonabsorbing assumption.
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http://dx.doi.org/10.1021/acs.est.5b00211DOI Listing
April 2015

Effectiveness of mitigation measures in reducing future primary particulate matter emissions from on-road vehicle exhaust.

Environ Sci Technol 2014 Dec 1;48(24):14455-63. Epub 2014 Dec 1.

Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.

This work evaluates the effectiveness of on-road primary particulate matter emission reductions that can be achieved by long-term vehicle scrappage and retrofit measures on regional and global levels. Scenario analysis shows that scrappage can provide significant emission reductions as soon as the measures begin, whereas retrofit provides greater emission reductions in later years, when more advanced technologies become available in most regions. Reductions are compared with a baseline that already accounts for implementation of clean vehicle standards. The greatest global emission reductions from a scrappage program occur 5 to 10 years after its introduction and can reach as much as 70%. The greatest reductions with retrofit occur around 2030 and range from 16-31%. Monte Carlo simulations are used to evaluate how uncertainties in the composition of the vehicle fleet affect predicted reductions. Scrappage and retrofit reduce global emissions by 22-60% and 15-31%, respectively, within 95% confidence intervals, under a midrange scenario in the year 2030. The simulations provide guidance about which strategies are most effective for specific regions. Retrofit is preferable for high-income regions. For regions where early emission standards are in place, scrappage is suggested, followed by retrofit after more advanced emission standards are introduced. The early implementation of advanced emission standards is recommended for Western and Eastern Africa.
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http://dx.doi.org/10.1021/es503197fDOI Listing
December 2014

Global chemical composition of ambient fine particulate matter for exposure assessment.

Environ Sci Technol 2014 Nov 6;48(22):13060-8. Epub 2014 Nov 6.

Department of Physics and Atmospheric Science, Dalhousie University , Halifax, Nova Scotia B3H 4R2, Canada.

Epidemiologic and health impact studies are inhibited by the paucity of global, long-term measurements of the chemical composition of fine particulate matter. We inferred PM2.5 chemical composition at 0.1° × 0.1° spatial resolution for 2004-2008 by combining aerosol optical depth retrieved from the MODIS and MISR satellite instruments, with coincident profile and composition information from the GEOS-Chem global chemical transport model. Evaluation of the satellite-model PM2.5 composition data set with North American in situ measurements indicated significant spatial agreement for secondary inorganic aerosol, particulate organic mass, black carbon, mineral dust, and sea salt. We found that global population-weighted PM2.5 concentrations were dominated by particulate organic mass (11.9 ± 7.3 μg/m(3)), secondary inorganic aerosol (11.1 ± 5.0 μg/m(3)), and mineral dust (11.1 ± 7.9 μg/m(3)). Secondary inorganic PM2.5 concentrations exceeded 30 μg/m(3) over East China. Sensitivity simulations suggested that population-weighted ambient PM2.5 from biofuel burning (11 μg/m(3)) could be almost as large as from fossil fuel combustion sources (17 μg/m(3)). These estimates offer information about global population exposure to the chemical components and sources of PM2.5.
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http://dx.doi.org/10.1021/es502965bDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4238642PMC
November 2014

Historical Mercury releases from commercial products: global environmental implications.

Environ Sci Technol 2014 Sep 22;48(17):10242-50. Epub 2014 Aug 22.

Department of Earth and Planetary Sciences, Harvard University , Cambridge, Massachusetts 02138, United States.

The intentional use of mercury (Hg) in products and processes ("commercial Hg") has contributed a large and previously unquantified anthropogenic source of Hg to the global environment over the industrial era, with major implications for Hg accumulation in environmental reservoirs. We present a global inventory of commercial Hg uses and releases to the atmosphere, water, soil, and landfills from 1850 to 2010. Previous inventories of anthropogenic Hg releases have focused almost exclusively on atmospheric emissions from "byproduct" sectors (e.g., fossil fuel combustion). Cumulative anthropogenic atmospheric Hg emissions since 1850 have recently been estimated at 215 Gg (only including commercial Hg releases from chlor-alkali production, waste incineration, and mining). We find that other commercial Hg uses and nonatmospheric releases from chlor-alkali and mining result in an additional 540 Gg of Hg released to the global environment since 1850 (air: 20%; water: 30%; soil: 30%; landfills: 20%). Some of this release has been sequestered in landfills and benthic sediments, but 310 Gg actively cycles among geochemical reservoirs and contributes to elevated present-day environmental Hg concentrations. Commercial Hg use peaked in 1970 and has declined sharply since. We use our inventory of historical environmental releases to force a global biogeochemical model that includes new estimates of the global burial in ocean margin sediments. Accounting for commercial Hg releases improves model consistency with observed atmospheric concentrations and associated historical trends.
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http://dx.doi.org/10.1021/es501337jDOI Listing
September 2014

Mercury stable isotope signatures of world coal deposits and historical coal combustion emissions.

Environ Sci Technol 2014 Jul 13;48(13):7660-8. Epub 2014 Jun 13.

Observatoire Midi-Pyrénées, Laboratoire Géosciences Environnement Toulouse, CNRS/IRD/Université de Toulouse , 14 avenue Edouard Belin, Toulouse, 31400 France.

Mercury (Hg) emissions from coal combustion contribute approximately half of anthropogenic Hg emissions to the atmosphere. With the implementation of the first legally binding UNEP treaty aimed at reducing anthropogenic Hg emissions, the identification and traceability of Hg emissions from different countries/regions are critically important. Here, we present a comprehensive world coal Hg stable isotope database including 108 new coal samples from major coal-producing deposits in South Africa, China, Europe, India, Indonesia, Mongolia, former USSR, and the U.S. A 4.7‰ range in δ(202)Hg (-3.9 to 0.8‰) and a 1‰ range in Δ(199)Hg (-0.6 to 0.4‰) are observed. Fourteen (p < 0.05) to 17 (p < 0.1) of the 28 pairwise comparisons between eight global regions are statistically distinguishable on the basis of δ(202)Hg, Δ(199)Hg or both, highlighting the potential application of Hg isotope signatures to coal Hg emissions tracing. A revised coal combustion Hg isotope fractionation model is presented, and suggests that gaseous elemental coal Hg emissions are enriched in the heavier Hg isotopes relative to oxidized forms of emitted Hg. The model explains to first order the published δ(202)Hg observations on near-field Hg deposition from a power plant and global scale atmospheric gaseous Hg. Yet, model uncertainties appear too large at present to permit straightforward Hg isotope source identification of atmospheric forms of Hg. Finally, global historical (1850-2008) coal Hg isotope emission curves were modeled and indicate modern-day mean δ(202)Hg and Δ(199)Hg values for bulk coal emissions of -1.2 ± 0.5‰ (1SD) and 0.05 ± 0.06‰ (1SD).
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http://dx.doi.org/10.1021/es501208aDOI Listing
July 2014

China's international trade and air pollution in the United States.

Proc Natl Acad Sci U S A 2014 Feb 21;111(5):1736-41. Epub 2014 Jan 21.

Laboratory for Climate and Ocean-Atmosphere Studies, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China.

China is the world's largest emitter of anthropogenic air pollutants, and measurable amounts of Chinese pollution are transported via the atmosphere to other countries, including the United States. However, a large fraction of Chinese emissions is due to manufacture of goods for foreign consumption. Here, we analyze the impacts of trade-related Chinese air pollutant emissions on the global atmospheric environment, linking an economic-emission analysis and atmospheric chemical transport modeling. We find that in 2006, 36% of anthropogenic sulfur dioxide, 27% of nitrogen oxides, 22% of carbon monoxide, and 17% of black carbon emitted in China were associated with production of goods for export. For each of these pollutants, about 21% of export-related Chinese emissions were attributed to China-to-US export. Atmospheric modeling shows that transport of the export-related Chinese pollution contributed 3-10% of annual mean surface sulfate concentrations and 0.5-1.5% of ozone over the western United States in 2006. This Chinese pollution also resulted in one extra day or more of noncompliance with the US ozone standard in 2006 over the Los Angeles area and many regions in the eastern United States. On a daily basis, the export-related Chinese pollution contributed, at a maximum, 12-24% of sulfate concentrations over the western United States. As the United States outsourced manufacturing to China, sulfate pollution in 2006 increased in the western United States but decreased in the eastern United States, reflecting the competing effect between enhanced transport of Chinese pollution and reduced US emissions. Our findings are relevant to international efforts to reduce transboundary air pollution.
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http://dx.doi.org/10.1073/pnas.1312860111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3918792PMC
February 2014

Ozone monitoring instrument observations of interannual increases in SO2 emissions from Indian coal-fired power plants during 2005-2012.

Environ Sci Technol 2013 Dec 4;47(24):13993-4000. Epub 2013 Dec 4.

Decision and Information Sciences Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.

Due to the rapid growth of electricity demand and the absence of regulations, sulfur dioxide (SO2) emissions from coal-fired power plants in India have increased notably in the past decade. In this study, we present the first interannual comparison of SO2 emissions and the satellite SO2 observations from the Ozone Monitoring Instrument (OMI) for Indian coal-fired power plants during the OMI era of 2005-2012. A detailed unit-based inventory is developed for the Indian coal-fired power sector, and results show that its SO2 emissions increased dramatically by 71% during 2005-2012. Using the oversampling technique, yearly high-resolution OMI maps for the whole domain of India are created, and they reveal a continuous increase in SO2 columns over India. Power plant regions with annual SO2 emissions greater than 50 Gg year(-1) produce statistically significant OMI signals, and a high correlation (R = 0.93) is found between SO2 emissions and OMI-observed SO2 burdens. Contrary to the decreasing trend of national mean SO2 concentrations reported by the Indian Government, both the total OMI-observed SO2 and annual average SO2 concentrations in coal-fired power plant regions increased by >60% during 2005-2012, implying the air quality monitoring network needs to be optimized to reflect the true SO2 situation in India.
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http://dx.doi.org/10.1021/es4039648DOI Listing
December 2013

Source forensics of black carbon aerosols from China.

Environ Sci Technol 2013 Aug 8;47(16):9102-8. Epub 2013 Aug 8.

Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.

The limited understanding of black carbon (BC) aerosol emissions from incomplete combustion causes a poorly constrained anthropogenic climate warming that globally may be second only to CO2 and regionally, such as over East Asia, the dominant driver of climate change. The relative contribution to atmospheric BC from fossil fuel versus biomass combustion is important to constrain as fossil BC is a stronger climate forcer. The source apportionment is the underpinning for targeted mitigation actions. However, technology-based "bottom-up" emission inventories are inconclusive, largely due to uncertain BC emission factors from small-scale/household combustion and open burning. We use "top-down" radiocarbon measurements of atmospheric BC from five sites including three city sites and two regional sites to determine that fossil fuel combustion produces 80 ± 6% of the BC emitted from China. This source-diagnostic radiocarbon signal in the ambient aerosol over East Asia establishes a much larger role for fossil fuel combustion than suggested by all 15 BC emission inventory models, including one with monthly resolution. Our results suggest that current climate modeling should refine both BC emission strength and consider the stronger radiative absorption associated with fossil-fuel-derived BC. To mitigate near-term climate effects and improve air quality in East Asia, activities such as residential coal combustion and city traffic should be targeted.
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http://dx.doi.org/10.1021/es401599rDOI Listing
August 2013

Increase in NOx emissions from Indian thermal power plants during 1996-2010: unit-based inventories and multisatellite observations.

Environ Sci Technol 2012 Jul 6;46(14):7463-70. Epub 2012 Jul 6.

Decision and Information Sciences Division, Argonne National Laboratory, Argonne, Illinois, United States.

Driven by rapid economic development and growing electricity demand, NO(x) emissions (E) from the power sector in India have increased dramatically since the mid-1990s. In this study, we present the NO(x) emissions from Indian public thermal power plants for the period 1996-2010 using a unit-based methodology and compare the emission estimates with the satellite observations of NO(2) tropospheric vertical column densities (TVCDs) from four spaceborne instruments: GOME, SCIAMACHY, OMI, and GOME-2. Results show that NO(x) emissions from Indian power plants increased by at least 70% during 1996-2010. Coal-fired power plants, NO(x) emissions from which are not regulated in India, contribute ∼96% to the total power sector emissions, followed by gas-fired (∼4%) and oil-fired (<1%) ones. A number of isolated NO(2) hot spots are observed over the power plant areas, and good agreement between NO(2) TVCDs and NO(x) emissions is found for areas dominated by power plant emissions. Average NO(2) TVCDs over power plant areas were continuously increasing during the study period. We find that the ratio of ΔE/E to ΔTVCD/TVCD changed from greater than one to less than one around 2005-2008, implying that a transition of the overall NO(x) chemistry occurred over the power plant areas, which may cause significant impact on the atmospheric environment.
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http://dx.doi.org/10.1021/es300831wDOI Listing
July 2012

All-time releases of mercury to the atmosphere from human activities.

Environ Sci Technol 2011 Dec 17;45(24):10485-91. Epub 2011 Nov 17.

Decision and Information Sciences Division, Argonne National Laboratory, Argonne, Illinois, United States.

Understanding the biogeochemical cycling of mercury is critical for explaining the presence of mercury in remote regions of the world, such as the Arctic and the Himalayas, as well as local concentrations. While we have good knowledge of present-day fluxes of mercury to the atmosphere, we have little knowledge of what emission levels were like in the past. Here we develop a trend of anthropogenic emissions of mercury to the atmosphere from 1850 to 2008-for which relatively complete data are available-and supplement that trend with an estimate of anthropogenic emissions prior to 1850. Global mercury emissions peaked in 1890 at 2600 Mg yr(-1), fell to 700-800 Mg yr(-1) in the interwar years, then rose steadily after 1950 to present-day levels of 2000 Mg yr(-1). Our estimate for total mercury emissions from human activities over all time is 350 Gg, of which 39% was emitted before 1850 and 61% after 1850. Using an eight-compartment global box-model of mercury biogeochemical cycling, we show that these emission trends successfully reproduce present-day atmospheric enrichment in mercury.
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http://dx.doi.org/10.1021/es202765mDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3246392PMC
December 2011

Global source-receptor relationships for mercury deposition under present-day and 2050 emissions scenarios.

Environ Sci Technol 2011 Dec 18;45(24):10477-84. Epub 2011 Nov 18.

Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, United States.

Global policies regulating anthropogenic mercury require an understanding of the relationship between emitted and deposited mercury on intercontinental scales. Here, we examine source-receptor relationships for present-day conditions and four 2050 IPCC scenarios encompassing a range of economic development and environmental regulation projections. We use the GEOS-Chem global model to track mercury from its point of emission through rapid cycling in surface ocean and land reservoirs to its accumulation in longer lived ocean and soil pools. Deposited mercury has a local component (emitted Hg(II), lifetime of 3.7 days against deposition) and a global component (emitted Hg(0), lifetime of 6 months against deposition). Fast recycling of deposited mercury through photoreduction of Hg(II) and re-emission of Hg(0) from surface reservoirs (ice, land, surface ocean) increases the effective lifetime of anthropogenic mercury to 9 months against loss to legacy reservoirs (soil pools and the subsurface ocean). This lifetime is still sufficiently short that source-receptor relationships have a strong hemispheric signature. Asian emissions are the largest source of anthropogenic deposition to all ocean basins, though there is also regional source influence from upwind continents. Current anthropogenic emissions account for only about one-third of mercury deposition to the global ocean with the remainder from natural and legacy sources. However, controls on anthropogenic emissions would have the added benefit of reducing the legacy mercury re-emitted to the atmosphere. Better understanding is needed of the time scales for transfer of mercury from active pools to stable geochemical reservoirs.
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http://dx.doi.org/10.1021/es202496yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3246401PMC
December 2011

Modeling vehicle emissions in different types of Chinese cities: importance of vehicle fleet and local features.

Environ Pollut 2011 Oct 23;159(10):2954-60. Epub 2011 May 23.

Institute of Energy, Environment and Economy, Tsinghua University, Beijing 100084, China.

We propose a method to simulate vehicle emissions in Chinese cities of different sizes and development stages. Twenty two cities are examined in this study. The target year is 2007. Among the cities, the vehicle emission factors were remarkably different (the highest is 50-90% higher than the lowest) owing to their distinct local features and vehicle technology levels, and the major contributors to total vehicle emissions were also different. A substantial increase in vehicle emissions is foreseeable unless stronger measures are implemented because the benefit of current policies can be quickly offset by the vehicle growth. Major efforts should be focused on all cities, especially developing cities where the requirements are lenient. This work aims a better understanding of vehicle emissions in all types of Chinese cities. The proposed method could benefit national emission inventory studies in improving accuracy and help in designing national and local policies for vehicle emission control.
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http://dx.doi.org/10.1016/j.envpol.2011.04.025DOI Listing
October 2011

Biomass burning contributions to ambient VOCs species at a receptor site in the Pearl River Delta (PRD), China.

Environ Sci Technol 2010 Jun;44(12):4577-82

State Joint Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China.

Ambient VOCs were measured by a proton transfer reaction-mass spectrometer (PTR-MS) at a receptor site in the Pearl River Delta (PRD) during October 19-November 18, 2008. Biomass burning plumes are identified by using acetonitrile as tracer, and enhancement ratios (ERs) of nine VOCs species relative to acetonitrile are obtained from linear regression analysis and the source-tracer-ratio method. Enhancement ratios determined by the two different methods show good agreement for most VOCs species. Biomass burning contributions are investigated by using the source-tracer-ratio method. Biomass burning contributed 9.5%-17.7% to mixing ratios of the nine VOCs. The estimated biomass burning contributions are compared with local emission inventories. Large discrepancies are observed between our results and the estimates in two emission inventories. Though biomass burning emissions in TRACE-P inventory agree well with our results, the VOCs speciation for aromatic compounds may be not appropriate for Guangdong.
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http://dx.doi.org/10.1021/es1003389DOI Listing
June 2010

Environmental implication of electric vehicles in China.

Environ Sci Technol 2010 Jul;44(13):4856-61

Institute of Energy, Environment and Economy, Tsinghua University, Beijing 100084, China.

Today, electric vehicles (EVs) are being proposed in China as one of the potential options to address the dramatically increasing energy demand from on-road transport. However, the mass use of EVs could involve multiple environmental issues, because EVs use electricity that is generated primarily from coal in China. We examined the fuel-cycle CO(2), SO(2), and NO(x) emissions of EVs in China in both current (2008) and future (2030) periods and compared them with those of conventional gasoline vehicles and gasoline hybrids. EVs do not promise much benefit in reducing CO(2) emissions currently, but greater CO(2) reduction could be expected in future if coal combustion technologies improve and the share of nonfossil electricity increases significantly. EVs could increase SO(2) emissions by 3-10 times and also double NO(x) emissions compared to gasoline vehicles if charged using the current electricity grid. In the future, EVs would be able to reach the NO(x) emission level of gasoline vehicles with advanced emission control devices equipped in thermal power plants but still increase SO(2). EVs do represent an effective solution to issues in China such as oil shortage, but critical policy support is urgently needed to address the environmental issues caused by the use of EVs to make EVs competitive with other vehicle alternatives.
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http://dx.doi.org/10.1021/es100520cDOI Listing
July 2010

Study of atmospheric mercury budget in East Asia using STEM-Hg modeling system.

Sci Total Environ 2010 Jul 21;408(16):3277-91. Epub 2010 May 21.

Department of Civil Engineering, Lamar University, Beaumont, TX 77710, USA.

East Asia is the largest source region of global anthropogenic mercury emissions, and contributes to atmospheric mercury concentration and deposition in other regions. Similarly, mercury from the global pool also plays a role in the chemical transport of mercury in East Asia. Annual simulations of atmospheric mercury in East Asia were performed using the STEM-Hg modeling system to study the mass budgets of mercury in the region. The model results showed strong seasonal variation in mercury concentration and deposition, with signals from large point sources. The annual mean concentrations for gaseous elemental mercury, reactive gaseous mercury and particulate mercury in central China and eastern coastal areas were 1.8 ng m(-3), 100 pg m(-3) and 150 pg m(-3), respectively. Boundary conditions had a strong influence on the simulated mercury concentration and deposition, contributing to 80% of the concentration and 70% of the deposition predicted by the model. The rest was caused by the regional emissions before they were transported out of the model domain. Using different oxidation rates reported for the Hg(0)-O(3) reaction (i.e., by Hall, 1995 vs. by Pal and Ariya, 2004) led to a 9% difference in the predicted mean concentration and a 40% difference in the predicted mean deposition. The estimated annual dry and wet deposition for East Asia in 2001 was in the range of 590-735 Mg and 482-696 Mg, respectively. The mercury mass outflow caused by the emissions in the domain was estimated to be 681-714 Mg yr(-1). This constituted 70% of the total mercury emission in the domain. The greatest outflow occurred in spring and early summer.
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http://dx.doi.org/10.1016/j.scitotenv.2010.04.039DOI Listing
July 2010

Projections of global mercury emissions in 2050.

Environ Sci Technol 2009 Apr;43(8):2983-8

Decision and Information Sciences Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.

Global Hg emissions are presented for the year 2050 under a variety of assumptions about socioeconomic and technology development. We find it likely that Hg emissions will increase in the future. The range of 2050 global Hg emissions is projected to be 2390-4860 Mg, compared to 2006 levels of 2480 Mg, reflecting a change of -4% to +96%. The main driving force for increased emissions is the expansion of coal-fired electricity generation in the developing world, particularly Asia. Our ability to arrest the growth in Hg emissions is limited by the relatively low Hg removal efficiency of the current generation of emission control technologies for coal-fired power plants (flue-gas desulfurization). Large-scale deployment of advanced Hg sorbent technologies, such as Activated Carbon Injection, offers the promise of lowering the 2050 emissions range to 1670-3480 Mg, but these technologies are not yet in commercial use. The share of elemental Hg in total emissions will decline from today's levels of approximately 65% to approximately 50-55% by 2050, while the share of divalent Hg will increase. This signals a shift from long-range transport of elemental Hg to local deposition of Hg compounds-though emissions of both species could increase under the worst case.
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http://dx.doi.org/10.1021/es802474jDOI Listing
April 2009
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