Pollution Control Policies Research Articles

Slower than expected reduction in annual PM2.5 in Xi'an revealed by machine learning-based meteorological normalization

To evaluate the effectiveness of air pollution control policies, trend analysis of the air pollutants is often performed. However, trend analysis of air pollutants over multiple years is complicated by the fact that changes in meteorology over time can also affect the levels of air pollutants in addition to changes in emissions or atmospheric chemistry. To decouple the meteorological effect, this study performed a trend analysis of the hourly fine particulate matter (PM2.5) observed at an urban background site in Xi'an city over 5 years from 2015 to 2019 using the machine learning algorithm. As a novel way of meteorological normalization, the meteorological parameters were used as constant input for 5 consecutive years. In this way, the impact of meteorological parameters was excluded, providing insights into the “real” changes in PM2.5 due to changes in emission strength or atmospheric chemistry. After meteorological normalization, a decreasing trend of −3.3 % year−1 (−1.9 μg m−3 year−1) in PM2.5 was seen, instead of −4.4 % year−1 from direct PM2.5 observation. Assuming the rate of −1.9 μg m−3 year−1 were kept constant for the next few decades in Xi'an, it would take approximately 25 years (in the year 2045) to reduce the annual PM2.5 level to 5 μg m−3, the new guideline value from World Health Organization. We also show that PM2.5 is primarily associated with anthropogenic emissions, which, underwent aqueous phase chemistry in winter and photochemical oxidation in summer as suggested by partial dependence of RH and Ox in different seasons. Therefore, reducing the anthropogenic secondary aerosol precursors at a higher rate, such as NOx and VOCs is expected to reduce the particulate pollution in this region more effectively than the current −3.3 % year−1 found in this study.

Confronting our Agricultural Nonpoint Source Control Policy Problem

AbstractFederal and state agricultural and environmental agencies have spent enormous sums since the 1990s to reduce nonpoint source (NPS) water pollution from agriculture. Yet, water quality problems are pervasive, and agriculture is a major cause. The lack of progress is often attributed to insufficient funding for pollution control practices relative to the scale of the problem. However, we attribute the lack of progress to shortcomings in agricultural NPS pollution control policy. We illustrate our argument after considering nearly four decades of federal, state, and local efforts to reduce agricultural NPS pollution to the Chesapeake Bay. Additional funding for current programs, absent fundamental program reform, is unlikely to produce reductions from agriculture needed to achieve desired water quality outcomes.

Deposition of trace metals associated with atmospheric particulate matter: Environmental fate and health risk assessment

Anthropogenic and natural sources influence trace metals (TMs) bound to different sized particulate matter (PM) in dry and wet atmospheric deposition, which can create ecosystem and human health issues in the long run. Limited reviews are available summarizing worldwide concentrations in TMs in atmospheric PMs, their sources and pathways. Simultaneously, quantitative assessment of the potential human and ecosystem health risks imposed by the atmospheric particulate matter has not been adequately reviewed. Addressing this gap, here we review, the concentration of TMs in dry deposition mainly varies with the responsible sources, whereas, in wet deposition, it depends on the solubility of TMs. Other than deposition on impervious surfaces, the TMs incorporated PM can be deposited on biological agents. Health risk assessments show that ingestion and dermal contact pathways are more likely to cause health issues, however, the probability of occurring ingestion and dermal contact pathways is limited. Attention must be paid to the contribution from non-exhaust and exhaust vehicular emissions for TMs in atmospheric deposition, understanding their impact on stormwater management and urban agriculture. Behaviors of TMs in the atmosphere depends on many complex factors including origin, wind patterns, and weather conditions. Therefore, future research needs to be carried to model and predict the fate and transfer of TMs once they are generated through natural and anthropogenic sources. We believe that such research would allow establishing pollution control policies and measures in urban environments which will be critical to reduce the levels of TMs associated with atmospheric deposition in the environment.

Can the joint regional air pollution control policy achieve a win-win outcome for the environment and economy? Evidence from China

We explore the effect of the Joint Prevention and Control System of Regional Air Pollution (JPCSRAP) in China from a composite environmental-economic perspective, based on Chinese urban data, using the PSM-DID method. We find that JPCSRAP can achieve a win-win outcome for the environment and economy, namely by reducing air pollution while achieving economic growth, with these effects increasing over time. However, the implementation effects differ by region. The effects of JPCSRAP are due to the strengthening of collaborative governance between cities, the upgrading of the industrial structure, and the encouragement of technological innovation. Our research provides an important reference for developing countries to achieve effective air pollution control and economic growth. • We study China’s Joint Prevention and Control System of Regional Air Pollution. • The JPCSRAP can achieve a win-win outcome for both the environment and the economy. • There is spatial and temporal heterogeneity in the policy effects of JPCSRA. • JPCSRAP strengthens the collaborative governance between cities. • JPCSRAP upgrades industrial structure and encourages technological innovation.

Co-benefits of renewable energy development: A brighter sky brings greater renewable power

Air pollution reduction is one of the most straightforward co-benefits of PV development, but its mechanism is complex. In a recent <i>One Earth</i> paper, Chen et al. analyzed the respective effects of different factors on solar power performance and show that the co-benefits of air pollution control policies for PV over the past decade would be grossly underestimated.

Short-Term and Long-Term Impacts of Air Pollution Control on China's Economy.

To deal with severe air pollution arising from rapid development, a series of air pollution control policies have been implemented in China. Previous literature has explored the short-term economic impacts of air pollution control, but the long-term economic impacts, which can better reflect the effectiveness of air pollution control, have received less attention. This paper has constructed an integrated assessment framework combining a multi-sectoral computable general equilibrium (CGE) model, air quality estimation module, and health impact module, to explore the short-term (2016) and long-term (2030) impacts of air pollution control on China's economy, by setting 2015 as the base year. The possible future air pollution reduction scenarios were set based on the Thirteenth Five-Year Plan (FYP13) proposed by the Chinese government. Our results have shown that air pollution control would harm China's economy and such adverse effects would be increased by stricter pollution reduction targets. Taking the health benefits of air pollution control into account can effectively alleviate the GDP losses, and even reverse them into economic benefits in the long term. Compared with business-as-usual (BAU) scenario (no policy constraints on SO2 and NOx emissions), the impact of air pollution control on GDP in the TAC_VIII scenario (emission reduction targets of 20% for SO2 and NOx are set every five years after 2015) would change from a loss of 1.20% in 2016 to an increase of 0.28% in 2030. Our results can provide policy implications for the optimization of China's air emissions control in the future.

Interprovincial Differences in Air Pollution in the Background of China’s Carbon Neutrality Target

Increasing air pollution, particularly in terms of fine particulate matter (PM2.5) and ozone (O3), caused by large-scale fossil fuel combustion, affects human health and economic activities in China. In this study, we analyzed the spatiotemporal trends of carbon emissions, carbon emission intensity, and concentrations of PM2.5 and O3 in 30 provincial-level administrative regions of China during 2010–2019. Overall, an increasing trend was observed in carbon emissions, with high emissions occurring in Shandong, Hebei, and Jiangsu in particular. The highest growth rates of carbon emissions were 169% and 117% in Xinjiang and Ningxia, respectively. Conversely, the carbon emission intensities and concentrations of PM2.5 and O3 decreased across the study regions at different rates. The western and central regions experienced the greatest decrease in carbon emissions in 2019 compared with that of 2010, followed by those in the northeastern and eastern regions. Spatiotemporal variations suggest that pollution control is essential for improving air quality and offsetting the negative impact of increased energy consumption. Overall, this study shows that pollution control policies lead to short-term improvements in air quality, and hence that the implementation of stringent environmental protection policies is essential.

Lithologic controls on the mobility of Cd in mining-impacted watersheds revealed by stable Cd isotopes

Cd-rich wastes from open-pit mining can be transported into rivers, which are often followed by deposition in river sediments and/or further transfer into agricultural soils. The lithology of bedrock exerts a huge effect on physicochemical properties (e.g., buffering capacities, metal species, mineral phases, etc.) of the river system, thereby potentially impacting the Cd mobility in watersheds. However, to date, little is known about the microscopic processes (e.g., dissolution, adsorption, and precipitation) controlling the migration of Cd from mines to varied watersheds. This study, therefore, aims to determine the controlling factors on Cd mobilization in two mining-impacted watersheds with contrasting bedrock lithology using both Cd and Pb isotopes. The Pb isotope ratios of sediments and soils in both watersheds fall into a binary mixing model with two isotopically distinct sources, i.e., mining wastes and bedrock. These results indicate that mining activities are the main sources of Cd in sediments and soils. However, the Cd isotope ratios reveal different Cd migration processes between the two watersheds. In the siliceous watershed, the δ114/110Cd values of sediments decrease from -0.116‰ in the upper reach to -0.712‰ in the lower reach, with a concomitant increase in Cd concentration, which may result from Cd adsorption by goethite due to the increased pH. In contrast, in the calcareous watershed, the Cd isotope compositions of sediments (-0.345 to -0.276‰) and the pH of river water are nearly invariable, suggesting that the adsorption and release of Cd in sediments are limited. This may result from the strong pH buffering effect due to the presence of carbonate rocks. This study highlights the different fates of Cd in siliceous and calcareous watersheds and suggests that the development of Cd pollution control policies must consider regional lithology.

Investigating Spatial Heterogeneity of the Environmental Kuznets Curve for Haze Pollution in China

This study investigates the environmental Kuznets curve (EKC) for haze in 31 cities and provinces across China using the spatial data for a period of 15 years, from 2000 to 2014. We utilized the geographically weighted regression (GWR) model to consider the spatial non-stationary characteristics of the air quality in a vast territory. This approach allowed us to verify the region-specific characteristics, while the global model estimated the average relationship across the entire nation. Although the EKC for haze was statistically significant in the global models, the results only confirmed the existence of an EKC between the overall air quality and economic performance. Thus, it was difficult to determine the regional differences in an EKC. The results of the GWR model found the spatial variability of each variable and showed significant spatial heterogeneity in the EKC across regions. Although six regions—Beijing, Gansu, Heilongjiang, Jiangxi, Jilin, Liaoning, Shanghai, Tianjin, Xinjiang, and Zhejiang—showed inverted U-shaped EKCs, these were only statistically significant in three big cities—Beijing, Tianjin, and Shanghai. The results demonstrated no EKCs in the other 25 provinces and cities. These results provide strong empirical evidence that there is significant spatial heterogeneity in the EKC of China. Thus, a more regionally specialized air pollution control policy is required to create an effective policy for balanced economic growth in China.

A New Coupling Method for PM2.5 Concentration Estimation by the Satellite-Based Semiempirical Model and Numerical Model

Aerosol optical and chemical properties play a major role in the retrieval of PM2.5 concentrations based on aerosol optical depth (AOD) data from satellites in the conventional semiempirical model (SEM). However, limited observation information hinders the high-resolution estimation of PM2.5. Therefore, a new method for evaluating near-surface PM2.5 at high spatial resolution is developed by coupling the SEM and the chemical transport model (CTM)-based numerical (CSEN) model. The numerical model can provide large-scale information for aerosol properties with high spatial resolution at a large scale based on emissions and meteorology, though it can still be biased in simulating absolute PM2.5 concentrations. Therefore, the two crucial aerosol characteristic parameters, including the coefficient integrated humidity effect (γ′) and the comprehensive reference value of aerosol properties (K) in SEM, have been redefined using the WRF-Chem numerical model. Improved model performance was observed for these results compared with the original SEM results. The monthly averaged correlation coefficients (R) by CSEN were 0.92, 0.82, 0.84, and 0.83 in January, April, July, and October, respectively, whereas those of the SEM were 0.80, 0.77, 0.72, and 0.72, respectively. All the statistical metrics of the model validation showed significant improvements in all seasons. The reduced biases of estimated PM2.5 by CSEN indicated the effect of hygroscopic growth and aerosol properties affected by the meteorology on the relationship between AOD and estimated PM2.5 concentrations, especially in winter and summer. The better performance of the CSEN model provides insight for air quality monitoring at different scales, which supplies important information for air pollution control policies and health impact analysis.

Chemical composition, oxidative potential and identifying the sources of outdoor PM2.5 after the improvement of air quality in Beijing.

Air pollution poses a serious threat to human health. The implementation of air pollution prevention and control policies has gradually reduced the level of atmospheric fine particles in Beijing. Exploring the latest characteristics of PM2.5 has become the key to further improving pollution reduction measures. In the current study, outdoor PM2.5 samples were collected in the spring and summer of Beijing, and the chemical species, oxidative potential (OP), and sources of PM2.5 were characterized. The mean PM2.5 concentration during the entire study period was 41.6 ± 30.9μgm-3. Although the PM2.5 level in summer was lower, its OP level was significantly higher than that in spring. SO42-, NH4+, EC, NO3-, and OC correlated well with volume-normalized OP (OPv). Strong positive correlations were found between OPv and the following elements: Cu, Pb, Zn, Ni, As, Cr, Sn, Cd, Al, and Mn. Seven sources of PM2.5 were identified, including traffic, soil dust, secondary sulfate, coal and biomass burning, oil combustion, secondary nitrate, and industry. Multiple regression analysis indicated that coal and biomass combustion, industry, and traffic were the main contributors to the OPv in spring, while secondary sulfate, oil combustion, and industry played a leading role in summer. The source region analysis revealed that different pollution sources were related to specific geographic distributions. In addition to local emission reduction policies, multi-provincial cooperation is necessary to further improve Beijing's air quality and reduce the adverse health effects of PM2.5.

4D-Var Inversion of European NH3 Emissions Using CrIS NH3 Measurements and GEOS-Chem Adjoint With Bi-Directional and Uni-Directional Flux Schemes.

We conduct the first 4D‐Var inversion of NH3 accounting for NH3 bi‐directional flux, using CrIS satellite NH3 observations over Europe in 2016. We find posterior NH3 emissions peak more in springtime than prior emissions at continental to national scales, and annually they are generally smaller than the prior emissions over central Europe, but larger over most of the rest of Europe. Annual posterior anthropogenic NH3 emissions for 25 European Union members (EU25) are 25% higher than the prior emissions and very close (<2% difference) to other inventories. Our posterior annual anthropogenic emissions for EU25, the UK, the Netherlands, and Switzerland are generally 10%–20% smaller than when treating NH3 fluxes as uni‐directional emissions, while the monthly regional difference can be up to 34% (Switzerland in July). Compared to monthly mean in‐situ observations, our posterior NH3 emissions from both schemes generally improve the magnitude and seasonality of simulated surface NH3 and bulk NH x wet deposition throughout most of Europe, whereas evaluation against hourly measurements at a background site shows the bi‐directional scheme better captures observed diurnal variability of surface NH3. This contrast highlights the need for accurately simulating diurnal variability of NH3 in assimilation of sun‐synchronous observations and also the potential value of future geostationary satellite observations. Overall, our top‐down ammonia emissions can help to examine the effectiveness of air pollution control policies to facilitate future air pollution management, as well as helping us understand the uncertainty in top‐down NH3 emissions estimates associated with treatment of NH3 surface exchange.

Spatiotemporal variations of PM2.5 pollution and its dynamic relationships with meteorological conditions in Beijing-Tianjin-Hebei region

Identifying the effects of meteorological conditions on PM2.5 pollution is of great significance to explore methods to reduce atmospheric pollution. This study attempts to analyze the spatiotemporal variations of PM2.5 pollution and its dynamic nexus with meteorological factors in the Beijing-Tianjin-Hebei (BTH) region from 2015 to 2020 using standard deviation ellipse (SDE) and panel vector autoregressive (PVAR) model. The results indicate that: (1) In 2015–2020, PM2.5 pollution decreased significantly, indicating air pollution control policies in China have taken effect; Also, it showed a cumulative effect, or there was the path dependence of air pollution. (2) PM2.5 pollution presented a distribution pattern from northeast to southwest, while the directionality of air pollution has weakened. Based on SDE, PM2.5 pollution in Cangzhou can reflect the average level in the BTH; (3) Meteorological conditions exhibited a lagged and sustained effect on PM2.5 pollution. Specifically, the effects of meteorological factors on PM2.5 presented disequilibrium over time. In the long run, precipitation and temperature mainly showed negative impacts on PM2.5 pollution, while wind speed, relative humidity and sunshine duration aggravated PM2.5 pollution in the BTH. This study contributes to extending the study on the spatiotemporal evolution of PM2.5 pollution and its links with meteorological conditions.

Water Pollution Control Policies and Laws in China and Suggestions for Vietnam

Water is an indispensable part of our environment. China is facing a serious water pollution situation. In order to reduce water pollution, China has implemented a wide range of policies to reduce and control water pollution. Vietnam is a country with remarkable similarities with China in terms of political institutions as well as economic development. Notably, two major river systems of Vietnam, the Red River and the Mekong River both originate from China and directly affect the water environment in Vietnam. Thus, the evaluation of China's water pollution control policies will provide helpful experiences and lessons to improve Vietnam’s policies and law on water pollution control.

Pollution Characteristics and Health Risk Assessment of VOCs in Jinghong

In order to investigate the seasonal variation in chemical characteristics of VOCs in the urban and suburban areas of southwest China, we used SUMMA canister sampling in Jinghong city from October 2016 to June 2017. Forty-eight VOC species concentrations were analyzed using atmospheric preconcentration gas chromatography–mass spectrometry (GC–MS), Then, regional VOC pollution characteristics, ozone formation potentials (OFP), source identity, and health risk assessments were studied. The results showed that the average concentration of total mass was 144.34 μg·m−3 in the urban area and 47.81 μg·m−3 in the suburban area. Alkanes accounted for the highest proportion of VOC groups at 38.11%, followed by olefins (36.60%) and aromatic hydrocarbons (25.28%). Propane and isoprene were the species with the highest mass concentrations in urban and suburban sampling sites. The calculation of OFP showed that the contributions of olefins and aromatic hydrocarbons were higher than those of alkanes. Through the ratio of specific species, the VOCs were mainly affected by motor vehicle exhaust emissions, fuel volatilization, vegetation emissions, and biomass combustion. Combined with the analysis of the backward trajectory model, biomass burning activities in Myanmar influenced the concentration of VOCs in Jinghong. Health risk assessments have shown that the noncarcinogenic risk and hazard index of atmospheric VOCs in Jinghong were low (less than 1). However, the value of the benzene cancer risk to the human body was higher than the safety threshold of 1 × 10−6, showing that benzene has carcinogenic risk. This study provides effective support for local governments formulating air pollution control policies.

Identification and monitoring of coal dust pollution in Wucaiwan mining area, Xinjiang (China) using Landsat derived enhanced coal dust index.

Coal dust is the main pollutant in coal mining areas. Such pollutants easily diffuse and are difficult to monitor, which increases the cost of environmental pollution control. Remote sensing technology can be used to dynamically monitor mining areas at a low cost, and thus, this is a common means of mining area management. According to the spectral characteristics of various ground objects in remote sensing images, a variety of remote sensing indexes can be constructed to extract the required information. In this study, the Wucaiwan open-pit coal mine was selected as the study area, and the Enhanced Coal Dust Index (ECDI) was established to extract the coal dust pollution information for the mining area. A new mining area pollution monitoring method was developed, which can provide technical support for environmental treatment and mining planning in Zhundong. The results of this study revealed the following: (1) Compared with the normalized difference coal index, the ECDI can expand the difference between the spectral information about the coal dust and the surrounding features, so it has a significant recognition ability for coal dust information. (2) From 2010 to 2021, the coal dust pollution in the study area initially increased and then decreased. With the continued exploitation of the coal mines in the study area, the coal dust pollution area increased from 14.77 km2 in 2010 to 69.49 km2 in 2014. After 2014, the local government issued various environmental pollution control policies, which had remarkable results. The coal dust pollution area decreased to 36.85 km2 and 17.85 km2 in 2018 and 2021, respectively. (3) There was a great deal of pollution around mines and roads, around which the pollution was more serious. Various factors, such as wind, coal type, and the mining, processing, and transportation modes, affect the distribution of the coal dust pollution.

The effects of the Promoting the Big and Quashing the Small Policy on pollutants from a coal power supply chain perspective

China implemented the Promoting the Big and Quashing the Small Policy (PBQSP) in 2007 to alleviate air pollution due to coal-fired power plants (CFPPs). However, how the policy affected the air pollutant emissions remains poorly understood. We compared the air pollutant emissions between decommissioned and newly-built CFPPs under the PBQSP by developing a plant-level supply chain emission inventory model, taking Shandong, China's top provincial-level coal power producer, as the case area. The results indicated that compared to a 27.4% increase in electricity produced in Shandong from 2010 to 2014, the NOx, particulate matter (PM), Hg, and SO2 emissions disproportionately increased by 10.3%, 11.7%, 11.8% and 0.5%, respectively. It was found that the PBQSP policy has made great contribution to air pollution mitigation, as the supply chain emission intensities (emissions per kilowatt-hour) of NOX, PM, Hg and SO2 of the newly-built CFPPs are three-quarters, two-fifths, three-fifths, and four-fifths lower, respectively, than those of the decommissioned CFPPs. However, coal transport route changes caused an increase in NOX, PM, and SO2 emissions by 44.0%, 45.5%, and 55.6%, respectively, during the transportation stage, which offset the PBQSP overall mitigation effect. By building a comprehensive assessment framework for air pollutant control policies, our study provides insights for formulating coordinated mitigation measures for the pollutant-intensive industries, such as promoting efficient air pollutant control technologies including the spray dust suppression devices.

Interpretative Structural Modeling Dalam Analisis Kelembagaan Pengendalian Kualitas Air Waduk Sutami

The Sutami Reservoir, located in Malang Regency, East Java, has moderate to severe levels of pollution. This pollution problem can reduce the water quality of the Sutami Reservoir, so it requires coordination from the agencies concerned to formulate water pollution control policies. The management agency for the Sutami Reservoir is the ‘Perum Jasa Tirta 1’ (PJT 1). The institutional analysis applied is the Interpretative Structural Modeling (ISM) method, to find out which agencies are key elements/factors. There are eleven agencies analyzed. Agencies that are included in the ‘Dependent’ sector are the Water Resources Public Works Office, the Tourism and Culture Office, the Livestock and Animal Health Office, the Population Control and Family Planning Office, and the rice farmer groups. Institutions in the ‘Linkage’ sector are the Food Crops, Horticulture, and Plantations Office and the Industry and Trade Office. Institutions in the ‘Independent’ sector that play a key role are the Environment Office, the Fisheries Office, Balai Besar Wilayah Sungai Brantas, and the floating net cage fish farmer group. These four agencies are the key elements that have a big driving power so that more in-depth coordination needs to be carried out for the formulation of policies and regulations for water quality control.

The coupling coordination degree between urbanization and air environment in the Beijing(Jing)-Tianjin(Jin)-Hebei(Ji) urban agglomeration

Urban agglomeration is an important geospatial unit for achieving SDGs. At the same time, air environment is the key to ensure the healthy life and safe production of mankind. Despite growing concern over the sustainable development in urban agglomeration, there is still little discussion on the coordination between air environment and urbanization within urban agglomeration. Here, the coupling evaluation index system was constructed from four urbanization aspects and three air environment aspects. Based on the real nonlinear internal relationship, the CG-GSO model was used to quantify the urbanization development level in the Beijing(Jing)-Tianjin(Jin)-Hebei(Ji) urban agglomeration from 2003 to 2017. It showed that social urbanization and economic urbanization were mainly the driving factors in single regions, and the urbanization development levels were rising steadily in single regions and urban agglomeration. In the air environment subsystem, the driving factors mainly existed in the air environment pressure and control, while the dynamic trends were fluctuating upward. On urbanization, urban agglomeration was conductive to the realization of regional sustainable development; but on air environment, the result was the opposite. In addition, the dynamic trend of the coupling coordination degree was far worse in urban agglomeration than in single regions. The scenarios were predicted and analyzed on barely and superiorly balanced development during different periods, and strong national pollution control policy was the key to promote the coordinated development between urbanization and air environment in the Beijing(Jing)-Tianjin(Jin)-Hebei(Ji) urban agglomeration. This study provides reference for sustainable development in urban agglomerations.

Air pollutant emissions induced by rural-to-urban migration during China's urbanization (2005–2015)

As the world's most populous country, China has witnessed rapid urbanization in recent decades, with population migration from rural to urban (RU) regions as the major driving force. Due to the large gap between rural and urban consumption and investment level, large-scale RU migration impacts air pollutant emissions and creates extra uncertainties for air quality improvement. Here, we integrated population migration assessment, an environmentally extended input–output model and structural decomposition analysis to evaluate the NOx, SO2 and primary PM2.5 emissions induced by RU migration during China's urbanization from 2005 to 2015. The results show that RU migration increased air pollutant emissions, while the increases in NOx and SO2 emissions peaked in approximately 2010 at 2.4 Mt and 2.2 Mt, accounting for 9.2% and 8.7% of the national emissions, respectively. The primary PM2.5 emissions induced by RU migration also peaked in approximately 2012 at 0.3 Mt, accounting for 2.8% of the national emissions. The indirect emissions embodied in consumption and investment increased, while household direct emissions decreased. The widening gap between urban and rural investment and consumption exerted a major increasing effect on migration-induced emissions; in contrast, the falling emission intensity contributed the most to the decreasing effect benefitting from end-of-pipe control technology applications as well as improving energy efficiency. The peak of air pollutant emissions induced by RU migration indicates that although urbanization currently creates extra environmental pressure in China, it is possible to reconcile urbanization and air quality improvement in the future with updating urbanization and air pollution control policies.