This article analyzed the control progress and current status of air quality,identified the major air pollution issues and challenges in future,proposed the long-term air pollution control ...targets,and suggested the options for better air quality in China.With the continuing growth of economy in the next 10–15 years,China will face a more severe situation of energy consumption,electricity generation and vehicle population leading to increase in multiple pollutant emissions.Controlling regional air pollution especially fine particles and ozone,as well as lowering carbon emissions from fossil fuel consumption will be a big challenge for the country.To protect public health and the eco-system,the ambient air quality in all Chinese cities shall attain the national ambient air quality standards （NAAQS） and ambient air quality guideline values set by the World Health Organization （WHO）.To achieve the air quality targets,the emissions of SO 2,NOx,PM 10,and volatile organic compounds （VOC） should decrease by 60%,40%,50%,and 40%,respectively,on the basis of that in 2005.A comprehensive control policy focusing on multiple pollutants and emission sources at both the local and regional levels was proposed to mitigate the regional air pollution issue in China.The options include development of clean energy resources,promotion of clean and efficient coal use,enhancement of vehicle pollution control,implementation of synchronous control of multiple pollutants including SO 2,NOx,VOC,and PM emissions,joint prevention and control of regional air pollution,and application of climate friendly air pollution control measures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Exposure to fine particles ≤2.5μm in aerodynamic diameter (PM2.5) from incomplete combustion of solid fuels in household stoves, denoted household air pollution (HAP), is a major contributor to ill ...health in China and globally. Chinese households are, however, undergoing a massive transition to cleaner household fuels. The objective of the present study is to establish the importance of internal migration when it comes to the changing household fuel use pattern and the associated exposure to PM2.5 for the period 2000 to 2010. We also estimate health benefits of the fuel transition in terms of avoided premature deaths. Using China Census data on population, migration, and household fuel use for 2000 and 2010 we identify the size, place of residence, and main cooking fuel of sub-populations in 2000 and 2010, respectively. We combine these data with estimated exposure levels for the sub-populations and estimate changes in population exposure over the decade. We find that the population weighted exposure (PWE) for the Chinese population as a whole was reduced by 52 (36–70) μg/m3 PM2.5 over the decade, and that about 60% of the reduction can be linked to internal migration. During the same period the migrant population, in total 261million people, was subject to a reduced population weighted exposure (ΔPWE) of 123 (87–165) μg/m3 PM2.5. The corresponding figure for non-migrants is 34 (23–47) μg/m3. The largest ΔPWE was estimated for rural-to-urban migrants (138million people), 214 (154–283) μg/m3. The estimated annual health benefit associated with the reduced exposure in the total population is 31 (26–37) billion USD, corresponding to 0.4% of the Chinese GDP.
•We identify changes in household fuel use in China from 2000 to 2010.•We estimate how the population exposure to PM2.5 changed over the decade.•~60% of the total exposure reduction of about 50μg/m3 can be linked to migration.•Annual mean PM2.5 exposure of rural–urban migrants was reduced by about 215μg/m3.•The annual health benefit from the energy transition is about 30billion USD.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A series of TiO2/biochar composite catalysts were prepared by the hydrolysis method for the degradation of methyl orange, where biochar was obtained from the pyrolysis of waste walnut shells. The ...catalysts were examined by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), photoluminescence spectroscopy (PL) and X-ray photoelectron spectroscopy (XPS), elemental analysis and ultra violet-visible diffuse reflectance spectroscopy (UV–vis DRS). The photocatalytic activity results showed that the catalysts noted as CT0.1/1, CT0.2/2 and CT 0.5/1 exhibited higher catalytic activity than that of pure TiO2. Besides, catalyst CT0.2/1 exhibited the highest catalytic activity (the decolorization efficiency of 96.88% and the mineralization efficiency of 83.23% were obtained), attributed to the synergistic effect of biochar and TiO2, while CT1/1 possessed the lowest activity due to the shelter of light by the excess biochar. After 5 repeated use, the catalyst CT0.2/1 still exhibited rather high activity toward the degradation of MO, where the decolorization efficiency and mineralization efficiency of MO achieved 92.45% and 76.56%, and the loss of activity was negligible.
•Walnut shell biochar was firstly served as low-cost support for TiO2.•Appropriate amount of biochar can promote the activity of TiO2.•Compared with TiO2, the decolorization and mineralization efficiency of CT0.2/1 increased by 20.84% and 51.00%, respectively.•CT0.2/1 exhibited high stability during repeated use.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Background: In 2013, China released the Air Pollution Prevention and Control Action Plan (Action Plan), which set the roadmap for national air pollution control actions for the period of 2013 to ...2017. A decrease in the fine particulate matter with aerodynamic diameter ≤ 2.5μ m (PM 2.5 ) concentration may lead to a substantial benefit for human health. Objective: We aimed to quantify the relative contributions four factors: emission reductions, changed meteorology, population growth, and a change in baseline mortality rates to the reducedPM 2.5 -related mortality (PM 2.5 -mortality) during the 2013–2017 period and evaluate the importance of emission controls for human health protection in China. Methods: The integrated exposure–response function was adopted to estimate the chronic health effects ofPM 2.5 . The annualPM 2.5 concentrations were estimated from chemical transport model simulations combined with surface observations for 2013 and 2017. Relative contributions toPM 2.5 -mortality from emission reductions and the three factors were individually quantified through scenario analysis. Results: The estimated totalPM 2.5 -mortality in China was 1.389 million 95% confidence interval (CI): 1.005 million, 1.631 million in 2013 but was substantially reduced to 1.102 million (95% CI: 0.755 million, 1.337 million) in 2017. Emission controls contributed 88.7% to this reduction inPM 2.5 -mortality, while changed meteorology, the change in baseline mortality rates, and population growth during 2013–2017 contributed 9.6, 3.8, and − 2.2 % , respectively. Conclusions: The implementation of the Action Plan has significantly reduced thePM 2.5 concentration in regions of China where population density is high, dominating the decline inPM 2.5 -mortality during 2013–2017. However, the health burden ofPM 2.5 pollution in China is still extremely high compared with that in other developed countries. An aggressive air pollution control strategy should be implemented in densely populated areas to further reduce the health burden.
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CEKLJ, DOBA, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK, VSZLJ
In order to cope with heavy haze pollution in China, the Air Pollution Prevention and Control Action Plan including phased goals of the fine particulate matter (PM2.5) was issued in 2013. In this ...study, China's emission inventories in the baseline 2012 and the future scenarios of 2017 and 2020 have been developed based on this Action Plan. Beijing-Tianjin-Hebei (Jing-Jin-Ji) region, one of the most polluted regions in China, was taken as a case to assess the impact of phased emission control measures on PM2.5 concentration reduction using WRF-CMAQ model system. With the implementation of the Action Plan, the emissions of sulfur dioxide (SO2), nitrogen oxides (NOX), PM2.5, non-methane volatile organic compound (NMVOC), and ammonia (NH3) in 2017 will decrease by36%, 31%, 30%,12%, and −10% from the 2012 levels in Jing-Jin-Ji, respectively. In 2020, the emissions of SO2, NOX, PM2.5, NMVOC, and NH3 will decrease by 40%, 44%, 40%, 22%, and −3% from the 2012 levels in Jing-Jin-Ji, respectively. Consequently, the ambient annual PM2.5 concentration under the scenarios of 2017 and 2020 will be 28.3% and 37.8% lower than those in 2012, respectively. The Action Plan provided an effective approach to alleviate PM2.5 pollution level in Jing-Jin-Ji region. However, emission control of NMVOC and NH3 should be paid more attention and be strengthened in future. Meanwhile, emission control of NOx, SO2, NH3 and NMVOC synergistically are highly needed in the future because multiple pollutants impact on PM2.5 and O3 concentrations nonlinearly.
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•Multiple-pollutants emission inventory for 2012 and two scenarios for 2017 and 2020 are developed based on the Action Plan.•WRF-CMAQ model system is used to simulate PM2.5 concentrations in Jing-Jin-Ji region during 2012-2020.•PM2.5 concentrations under the scenarios of 2017 and 2020 will be 28.3% and 37.8% lower than those in 2012, respectively.•NMVOC and NH3 should be strictly controlled in the future.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Nitrous acid (HONO) is a major source of the hydroxyl radical (OH) and plays a key role in atmospheric photochemistry. The lack of spatially resolved HONO concentration information results in large ...knowledge gaps of HONO and its role in atmospheric chemistry and air pollution in China. In this work, an ensemble machine learning model comprising of random forest, gradient boosting, and back propagation neural network was proposed, for the first time, to estimate the long-term (2006–2017) daily HONO concentrations across China in 0.25° resolution. Further, the key factors controlling the space-time variablity of HONO concentrations were analyzed based on variable importance values. The ensemble model well characterized the spatiotemporal distribution of daily HONO concentrations with the sampled-based, site-based and by-year cross-validation (CV) R2 (RMSE) of 0.7 (0.36 ppbv), 0.67 (0.36 ppbv), and 0.62 (0.40 ppbv), respectively. HONO hotspots were mainly distributed in the Beijing-Tianjin-Hebei (BTH), Pearl River Delta (PRD), Yangtze River Delta (YRD), and several sites of Sichuan Basin, in line with the distribution patterns of the tropospheric NO2 columns and assimilated surface NO3− levels. The national HONO levels stagnated during 2006–2013, then declined after 2013 benefiting from the implementation of the Action Plan for Air Pollution Prevention and Control. The NO3− concentration, urban area, NO2 column density ranked as important variables for HONO prediction, while agricultral land, forest and grassland played minor roles in affecting HONO concentrations, suggesting the significant role of heterogeneous HONO production from anthropogenic precursor emissions. Leveraging the ground-level HONO observations, this study fills the gap of statistically modelling nationwide HONO in China, which provides essential data for atmospheric chemistry research.
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•The ensemble model well characterized the spatiotemporal distribution of daily HONO concentrations.•HONO hotspots were distributed in NCP, PRD, YRD, and Sichuan Basin.•The NO3− concentration, urban area, NO2 column density were important HONO predictors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Beijing, the capital of China, has experienced rapid industrialization, urbanization and motorization in recent decades. Consequently, air pollution in Beijing, especially fine particulate matter ...(PM2.5) pollution, has gradually become a severe environmental issue, due to the continuing growth in energy consumption and the resulting multiple pollutant emissions. In response to the increasingly serious PM2.5 pollution, Beijing's government implemented a series of policies, measures and regulations on air pollution prevention and control and took some concrete actions to improve air quality. In this paper, firstly, we summarize China's ambient air quality standards, China's policies and regulations on air pollution prevention and control. Secondly, we illustrate historical evolution and current status of air pollution in Beijing. Finally, we introduce control measures and actions in Beijing and its surrounding areas. The paper aims to help environmental scientists and policy makers around the world understand the past and current air pollution in Beijing and control strategies and actions taken by Beijing's government. Display omitted
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
As the key for haze control, atmospheric fine particulate matter with aerodynamic diameter <2.5μm (or PM2.5) is of great concern lately in China. It is closely linked to fast pace of urbanization, ...industrialization and economic development, especially in eastern China. A good understanding of its sources is required for effective pollution abatement. Receptor models are one of the major methods for source apportionment used in China. The major objective of this study is to understand sources that contribute to fine particulate matter in China and key challenges in this area. Spatial distribution of fine particulate matter concentration, chemical composition and dominant sources in North and South China are summarized. Based on chemical speciation results from 31 cities and source apportionment results from 21 cities, it is found that secondary sources and traffic emission have higher contribution in South China while the percentage of coal combustion, dust and biomass burning to total PM2.5 are higher in North China. Source profiles established in China from 44 cities and areas are also summarized as references for future source apportionment studies. Suggestions for future research are also provided including methods for evaluating source apportionment results, ways for integrating multiple source apportionment methods, the need for standardizing protocols and developing tools for high-time resolution source apportionment.
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•Spatial distribution of chemical speciation, sources and source profiles in China are summarized.•In the south, contributions of secondary and traffic sources are higher while coal and dust are lower.•Future research needs for source apportionment in China are proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Nitrate is an increasingly important component of fine particulate matter (PM2.5) during winter in northern China. Past emission control has been ineffective in reducing winter nitrate. Here, we use ...extensive observations and a model with state-of-the-art nitrogen chemistry to identify the key factors that control the nitrate formation in the heavily polluted North China Plain (NCP). In contrast to the previous view of weak winter photochemistry, we show that the O3 and OH productions are sufficiently high in winter to facilitate fast gas-phase and heterogeneous conversion of NOX to nitrate over the NCP. Increasing O3 and OH productions from higher precursor levels and fast ROX cycling accelerate the nitrate generation during heavy pollution. We find that the 31.8% reduction of NOX emissions from 2010 to 2017 in the NCP lowers surface nitrate by only 0.2% and even increases nitrate in some polluted areas. This is mainly due to the increase of O3 and OH (by ∼30%), which has subsequently increased the conversion efficiency of NOX to HNO3 (by 38.7%). Future control strategies for the winter haze should also aim to lower photochemical oxidants, via larger and synchronized NOX and VOCs emissions reduction, to overcome the effects of nonlinear photochemistry and aerosol chemical feedback.
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IJS, KILJ, NUK, PNG, UL, UM
We systematically identify sources of black carbon (BC) in the Arctic, including BC in the troposphere, at surface and in snow, using tagged tracer technique implemented in a 3D global chemical ...transport model GEOS-Chem. We validate modeled BC sources (fossil fuel combustion versus biomass burning) against carbon isotope measurements at Barrow (Alaska), Zeppelin (Norway), Abisko (Sweden), Alert (Canada) and Tiksi (Russia) in the Arctic. The model reproduces the observed annual mean fraction of biomass burning (fbb, %) at the five sites within 20% and the observed and modeled monthly fbb values agree within a factor of two. Model results suggest that fossil fuel combustion is the major source of BC in the troposphere (50–94%, vary with sub-regions), at surface (55–68%) and in snow (58–69%) in the Arctic as annual mean, but biomass burning dominates at certain altitudes (600–800 hPa) and during periods of time between April to September. The model shows that BC in the troposphere, in deposition and in snow in different Arctic sub-regions have distinctively different sources and source regions. We find that long-range transport of Asian emissions has a stronger influence on BC in the atmosphere than on BC deposition. In contrast, contributions from Russian and European emissions are larger for BC deposition than for BC in the atmosphere. Specifically, Asian fossil fuel combustion emissions dominate BC loading in all Arctic sub-regions in both winter (Oct.–Mar., 35–54%) and summer (Apr.–Sep., 34–56%). For BC deposition, Siberian fossil fuel emissions are the largest contributors in Russia both in winter (62%) and summer (44%), and European fossil fuel emissions dominate in Ny-Ålesund (44% in winter) and Tromsø (71% in winter and 46% in summer). For BC deposition in the North American sector, Asian fossil fuel emissions are the largest contributors in winter (25–38%) and North American biomass burning emissions (38–72%) dominate in summer.
Relative source contributions (%) of BC loading, deposition and BC in snow in the eight sub-regions in the Arctic. Solid bars are relative contributions of fossil fuel emissions in North America (orange), Europe (blue), Siberia (purple), Asia (green) and other regions (grey). Shaded bars are relative contributions of biomass burning emissions with the same colour code for different source regions. Display omitted
•Long-range transport of Asian emissions has a stronger influence on BC in air than on BC deposition in the Arctic.•Contributions from Russian and European emissions are larger for BC deposition than for atmospheric BC.•BC in different sub-regions in the Arctic have temporally and vertically varying sources and source regions.•Fossil fuel combustion is the major source of BC in the troposphere, at surface and in snow in the Arctic.•Asian sources are large contributors to BC in the troposphere and in snow in the Arctic.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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