[en] An inventory of biofuel combustion is used to develop estimates of the emissions of carbon-containing greenhouses gases (CO₂, CO, CH₄, and NMHC) in Asian countries. It is estimated that biofuels contributed 573 Tg-C (teragrams of carbon; 1 Tg = 10¹² g) in 1990, about 28% of the total carbon emissions from energy use in Asia. China (259 Tg-C) and India (187 Tg-C) were the largest emitting countries. The majority of the emissions, 504 Tg-C, were in the form of CO₂; however, emissions of non-CO₂ greenhouse gases were significant: 57 Tg-C as CO, 6.4 Tg-C as CH₄, and 5.9 Tg-C as NMHC. Because of the high rates of incomplete combustion in typical biofuel stoves and cookers and the high global warming potentials (GWP) of the products of incomplete combustion (PICs), biofuels comprise an even larger share of energy-related emissions when measured in terms of total GWP (in CO₂ equivalents): 38% over a 20-year time horizon and 31% over a 100-year time horizon. Even when the biofuel is assumed to be harvested on a completely sustainable basis (all CO₂ emissions reabsorbed in the following growing season), PIC emissions from biofuel combustion account for 4.5% of the total carbon emissions and 23% of CO₂ equivalents on a short-term (20-year) GWP basis. (Author)

[en] This paper presents the first comprehensive estimates of particulate emissions in China by size distribution and major components. Using a technology-based emission inventory approach, we are able to classify particulate emissions into three size ranges, TSP, PM₁₀ and PM_2.5, and identify the contributions of black carbon (BC), organic carbon (OC), Ca and Mg. Total particulate emissions are estimated to be 27.4 Tg for the year 2001, of which 17.8 Tg are PM₁₀ and 12.7 Tg are PM_2.5. Industrial processes are the major sources of particles over all three size ranges, but residential biofuel use and transportation sources become increasingly important for PM₁₀ and PM_2.5. The industrialized coastal provinces, such as Shandong, Jiangsu and Hebei, are the major sources of particulate emissions. The industrialized and developing regions show different characteristic emission ratios of PM_2.5/TSP, (BC+OC)/PM_2.5 and (Ca+Mg)/TSP. In the future, we can expect significant reductions in primary particulate emissions and major changes in the patterns of size and species

[en] To better understand the reductions in local air pollution that will result from the implementation of current Chinese energy policy, as well as the co-benefit for greenhouse-gas emission reductions, a Shanghai case study was conducted. The MARKAL model was used to forecast energy consumption and emissions of local air pollutants under different energy policy scenarios and also to analyze the associated reductions in CO₂ emissions. The results show that energy policies in Shanghai will significantly reduce SO₂ and PM₁ emissions and will also achieve the co-benefit of mitigating the increase of CO₂ emissions. In energy policy scenarios, SO₂ emissions during the period 2000-2020 will maintain the same level as in 2000; and the annual rate of increase of CO₂ emissions will be reduced to 1.1-1.2%, compared with 2.7% under a business-as-usual scenario. The problem for the future will be NO _x emissions, which are projected to increase by 60-70% by 2020, due to expansion of the transportation system

[en] Highlights: • Total Hg released to the environment from coal combustion is estimated to be 38 Gg. • 71% of this Hg was released into the atmosphere, while 31% went to land and water. • Most of the Hg from coal combustion was released in Asia and Europe (32% each). • The fraction of Hg released to the air as elemental Hg has steadily increased. • In the year 2010 about 1 Gg of Hg was released worldwide to all media. 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, 10⁹ g 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 0.01 Gg yr⁻¹ in 1850 to 1 Gg yr⁻¹ 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 8.8 Gg of this Hg have simply been discarded to waste piles or ash ponds or rivers.

[en] When released to the biosphere, mercury (Hg) is very mobile and can take millennia to be returned to a secure, long-term repository. Understanding where and when Hg was released as a result of human activities allows better quantification of present-day reemissions and future trajectories of environmental concentrations. In this work, we estimate the time-varying releases of Hg in seven world regions over the 500 year period, 1510–2010. By our estimation, this comprises 95% of all-time anthropogenic releases. Globally, 1.47 Tg of Hg were released in this period, 23% directly to the atmosphere and 77% to land and water bodies. Cumulative releases have been largest in Europe (427 Gg) and North America (413 Gg). In some world regions (Africa/Middle East and Oceania), almost all (>99%) of the Hg is relatively recent (emitted since 1850), whereas in South America it is mostly of older vintage (63% emitted before 1850). Asia was the greatest-emitting region in 2010, while releases in Europe and North America have declined since the 1970s, as recognition of the risks posed by Hg have led to its phase-out in commercial usage. The continued use of Hg in artisanal and small-scale gold mining means that the Africa/Middle East region is now a major contributor. We estimate that 72% of cumulative Hg emissions to air has been in the form of elemental mercury (Hg⁰), which has a long lifetime in the atmosphere and can therefore be transported long distances. Our results show that 83% of the total Hg has been released to local water bodies, onto land, or quickly deposited from the air in divalent (Hg^II) form. Regionally, this value ranges from 77% in Africa/Middle East and Oceania to 89% in South America. Results from global biogeochemical modeling indicate improved agreement of the refined emission estimates in this study with archival records of Hg accumulation in estuarine and deep ocean sediment. (letter)

[en] We evaluate the recently increasing tropospheric NO₂ columns in Northern China measured by the Ozone Monitoring Instrument (OMI) with an advanced power-plant NO_x emission inventory and the NASA INTEX-B emission inventory, using a global chemical transport model (GEOS-Chem). In areas with newly built power plants the modeled and OMI-retrieved summertime average tropospheric NO₂ columns increased by 55% and 47%, respectively, between 2005 and 2007. A monthly average increase of 1.79 Gg NO_x emissions is calculated to lead to an increase of 1.0 x 10¹⁵ molecules cm^-2 in the modeled NO₂ columns in the study areas. Good consistency (R² = 0.61, slope = 1.18, n = 14) between the increased modeled and OMI-retrieved summertime average NO₂ columns is found. These results suggest that NO_x emissions from large power plants in Northern China can be identified and quantified using OMI retrievals with confidence. The NASA INTEX-B emission inventory appears to underestimate the NO_x emissions from the industry and transportation sectors, making it more difficult to quantify power-plant emissions when they are co-located with large cities.

[en] 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. - Highlights: → We examine vehicle emissions in 22 Chinese cities of different types and locations. → Vehicle emission factors of the cities differ by 50-90% due to distinct local features. → Each vehicle type contributes differently to total emissions among the cities. → A substantial increase in vehicle emissions in most Chinese cities is foreseeable. → City-specific fleet and local features are important in research and policy making. - Vehicle emission characteristics of Chinese cities are remarkably different, and local features need to be taken into account in vehicle emission studies and control strategy.

[en] Highlights: • Spatiotemporal changes of central heating CO₂ emissions at city level are shown. • A high-resolution gridded inventory of heating-related CO₂ emissions is built. • The satellite nighttime light data is used to downscale the city level emissions. • Differences in CO₂ emissions between urban and non-urban areas are discussed. -- Abstract: Energy consumption from central heating has rapidly increased in the cities of the North China Plain (NCP). The increasing use of natural gas in the central heating supply system may have altered the spatial and temporal patterns of CO₂ emissions from central heating, yet the quantitative impacts are poorly understood. Here we detect the spatio-temporal dynamics of CO₂ emissions of central heating from 2012 to 2016 at the prefectural-city level in the NCP region, by using the satellite NPP-VIIRS nighttime light data and a panel regression model to estimate CO₂ emissions on a 5 × 5 km² grid. We find that despite a slight decrease (2%) in 2014 under the “Natural Gas Utilization Policy”, CO₂ emissions continued to grow. Between 2012 and 2016, CO₂ emissions from central heating in the NCP increased from 106 to 121 Tg, although CO₂ emissions declined by 12% in Beijing due to the increasing contribution of natural gas boilers. The gridded CO₂ emissions map shows that over 2012–2016 coal burning is the main driving force of CO₂ emissions in both urban and non-urban regions, despite the increasing fraction of gas-based heating. Our results contribute to city-level policymaking on carbon reduction and climate change mitigation. The high-resolution gridded CO₂ emissions can also be applied in physical models to facilitate carbon cycle studies.