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We estimate that a cumulative total of 1540 (1060-2800) Gg (gigagrams, 109 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 round between SO2 emissions and OMl-observed SO2 burdens. Contrary to the decreasing trend ot 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. [ABSTRACT FROM AUTHOR]

Driven by rapid economic development and growing electricity demand, NOx emissions (E) from the power sector in India have increased dramatically since the mid-1990s. In this study, we present the NOx 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 NO2 tropospheric vertical column densities (TVCDs) from four spaceborne instruments: GOME, SCIAMACHY, OMI, and GOME-2. Results show that NOx emissions from Indian power plants increased by at least 70% during 1996-2010. Coal-fired power plants, NOx 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 NO2 hot spots are observed over the power plant areas, and good agreement between NO2 TVCDs and NOx emissions is found for areas dominated by power plant emissions. Average NO2 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 NOx chemistry occurred over the power plant areas, which may cause significant impact on the atmospheric environment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 towering 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 ~65% to ~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. [ABSTRACT FROM AUTHOR]

The Pearl River Delta is a major manufacturing region on the south coast of China that produces more than $100 billion of goods annually for export to North America, Europe, and other parts of Asia. Considerable air pollution is caused by the manufacturing industries themselves and by the power plants, trucks, and ships that support them. We estimate that 10-40% of emissions of primary SO2, NOx, RSP, and VOC in the region are caused by export-related activities. Using the STEM-2K1 atmospheric transport model, we estimate that these emissions contribute 5-30% of the ambient concentrations of SO2, NOx, NOz, and VOC in the region. One reason that the exported goods are cheap and therefore attractive to consumers in developed countries is that emission controls are lacking or of low performance. We estimate that state-of-the-art controls could be installed at an annualized cost of $0.3-3 billion, representing 0.3-3% of the value of the goods produced. We conclude that mitigation measures could be adopted without seriously affecting the prices of exported goods and would achieve considerable human health and other benefits in the form of reduced air pollutant concentrations in densely populated urban areas. [ABSTRACT FROM AUTHOR]

In the early 1990s, it was projected that annual SO[sub 2] emissions in Asia might grow to 80-110 Tg yr[sup -1] by 2020. Based on new high-resolution estimates from 1975 to 2000, we calculate that SO[sub 2] emissions in Asia might grow only to 40-45 Tg yr[sup -1] by 2020. The main reason for this lower estimate is a decline of SO[sub 2] emissions from 1995 to 2000 in China, which emits about two-thirds of Asian SO[sub 2]. The decline was due to a reduction in industrial coal use, a slowdown of the Chinese economy, and the closure of small and inefficient plants, among other reasons. One effect of the reduction in SO[sub 2] emissions in China has been a reduction in acid deposition not only in China but also in Japan. Reductions should also improve visibility and reduce health problems. SO[sub 2] emission reductions may increase global warming, but this warming effect could be partially offset by reductions in the emissions of black carbon. How SO[sub 2] emissions in the region change in the coming decades will depend on many competing factors (economic growth, pollution control laws, etc.). However a continuation of current trends would result in sulfur emissions lower than any IPCC forecasts. [ABSTRACT FROM AUTHOR]

The TROPOspheric Monitoring Instrument (TROPOMI) is used to derive top-down NO X emissions for two large power plants and three megacities in North America. We first re-process the vertical column NO 2 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 X emissions agree to within 10% of the emissions reported by the power plants. We then derive top-down NO X emissions rates for New York City, Chicago, and Toronto, and compare them to projected bottom-up emissions inventories. In this analysis of 2018 NO X 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 X 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 X 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 X emissions from relatively small sources and for sub-seasonal timeframes.

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.

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.

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).

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.

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.

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.

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.

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.

We propose a new link-based, bottom-up vehicle emission inventory method for Chinese cities using available on-road emission measurement data and activity survey data. This study uses Beijing as a case study and focuses on CO, HC, and NOx emissions from hot-stabilized activities of light-duty vehicles. The target year is 2004. The total quantity of emissions, emission intensity, temporal distribution of emissions by hour, and spatial distribution of emissions at 1 km x 1 km resolution are presented and compared with results from other inventory methods commonly used in China. The results show that the total emissions from light-duty vehicles in the Beijing urban area in 2004 were 1141 Mg of CO per day, 48 Mg of HC per day, and 32 Mg of NOx per day. Pollutant emissions from mobile sources show temporal and spatial variation trends that are consistent with the characteristics of people's activities. The inventory developed in this study reflects the influences of vehicle driving patterns in traffic on vehicle emissions on a road link basis, and it could be used to evaluate the impacts of traffic-related emission control measures in China.

We developed an air pollutant emission inventory for marine vessels in the Shanghai Port in 2003. We estimated emissions under cruising and maneuvering conditions based on two categories of vessels: (1) vessels in the Outer Port, which enter the area following notification of the Shanghai Maritime Safety Administration, a division of the Ministry of Communications of P.R. China; and (2) vessels in internal waterways, which enter those waters following notification of the local Port Administration Centers. Vessels in the Outer Port consist of three subcategories: (1) international vessels that are engaged in foreign commerce; (2) domestic vessels traveling along the downstream portion of the Huangpu River; and (3) domestic vessels traveling along the coast. We also estimate emissions from vessels over 1000 DWT operating under hotelling conditions in the Outer Port. In 2003, the total number of calls was approximately 1.3 million, of which 57% is attributed to vessels in internal waterways and 43% to vessels in the Outer Port. Total marine emissions for NOx, SO2, PM, HC, and CO2 in 2003 are estimated to be 58,160, 51,180, 6960, 4560, and 3,012,800 tons, respectively. Emissions are allocated to 1 km x 1 km grid cells for the 129 km x 102 km Shanghai Port study domain.

An intensive field study was conducted in Sumatra, Indonesia, during a peat fire episode to investigate the physical and chemical characteristics of particulate emissions in peat smoke and to provide necessary data for source-receptor analyses. Ambient air sampling was carried out at three different sites located at varying distances from the peatfires to determine changes in mass and number concentrations of PM2.5 and its chemical composition (carbonaceous and nitrogenous materials, polycyclic aromatic hydrocarbons, water-soluble inorganic and organic ions, and total and water-soluble metals). The three sites represent a rural site directly affected by the local peat combustion, a semirural site, and an urban site situated downwind of the peat fires. The mass concentration of PM2.5 and the number concentration of airborne particles were as high as 1600 microg/m3 and 1.7 x 10(5) cm(-3), respectively, in the vicinity of peat fires. The major components of PM2.5 in peat smoke haze were carbonaceous particles, particularly organic carbon, NO3-, and SO4(2-), while the less abundant constituents included ions such as NH4+, NO2-, Na+, K+, organic acids, and metals such as Al, Fe, and Ti. Source apportionment by chemical mass balance receptor modeling indicates that peat smoke can travel long distances and significantly affect the air quality at locations downwind.

We have developed multiple-year inventories of anthropogenic mercury emissions in China for 1995 through 2003. We estimate that total Hg emissions from all anthropogenic sources increased at an average annual rate of 2.9% during the period 1995-2003, reaching 696 (+/- 307) t in 2003, with a speciation split of 395 t of Hg0, 230 t of Hg2+, and 70 t of Hg(p). Nonferrous metals smelting and coal combustion continue to be the two leading mercury sources in China, as nonferrous metals production and coal consumption keep increasing. Nonferrous metals smelting and coal combustion together contributed approximately 80% of total Hg emissions during the past decade. Hg emissions from coal combustion increased from 202 t in 1995 to 257 t in 2003 at an average annual rate of 3.0%. Among all of the coal consumption sectors, the power sector is the leading one in Hg emissions growth, up by 5.9% annually. Hg emissions from nonferrous metals smelting increased from 230 t in 1995 to 321 t in 2003 at an average annual rate of 4.2%. Although Hg emissions related to gold smelting decreased since 1996, other nonferrous metals such as zinc, lead, and copper contributed significant Hg growth at annual rates of 8.5%, 13.0%, and 6.9%, respectively. At provincial level, the trends of Hg emissions show significant variation. The uncertainty level decreased from +/- 78% (95% confidence interval) in the estimate of total emissions in 1995, to +/- 44% in 2003. This is primarily attributed to the decreased emissions from those Hg sources with the largest uncertainty in both activity levels and emission factors, such as artisanal gold smelting, mercury mining, and battery/fluorescent lamp production.