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The society has high concerns on the inequality that people are disproportionately exposed to ambient air pollution, but with more time spent indoors, the disparity in the total exposure considering both indoor and outdoor exposure has not been explored; and with the socioeconomical development and efforts in fighting against air pollution, it is unknown how the exposure inequality changed over time. Based on the city-level panel data, this study revealed the Concentration Index (C) in ambient PM

The COVID-19 quarantine in China is thought to have been beneficial for reducing the population exposure to ambient air pollution. The overall exposure also depends, however, on indoor air quality and human mobility and activities, which also changed during the pandemic. Here we integrate real-time mobility data, questionnaire survey on during-pandemic human activity patterns, advanced air quality modeling techniques, and an indoor exposure model. We first show a decrease of 16.7 μg∙m-3 in the national average population-weighted ambient PM2.5 during the quarantine (i.e., the one month following the start of the Spring Festival holiday). The total population-weighted exposure (PWE) to PM2.5 considering both indoor and outdoor environments, however, increased by 5.7 μg∙m-3. The increase in PWE was mainly due to the nationwide population migration from urban to rural areas before the Spring Festival coupled with the freezing of the migration backward due to the quarantine (+10.8 μg∙m-3), which increased household energy consumption and the fraction of people exposed to rural household air pollution (HAP) indoors. The changes in PWE due to the quarantine were -14.0 and +19.2 ug∙m-3 among urban and rural populations, respectively, and ranged from -9.1 ug∙m-3 in the provinces with the highest per-capita income to 7.1 ug∙m-3 in the provinces with the lowest. HAP contributed 82% of PWE during this period, which was likely more severe than any period in recent years. Our analysis reveals an increased inequality of air pollution exposure during the COVID-19 quarantine and highlights the importance of HAP for population health in China.

Indoor air pollution has aroused increasing concerns due to its significant adverse health impacts. Indoor PM

Residential heating using solid fuels contributes significantly to air pollution and has subsequent health impacts in China. To mitigate emissions, a clean heating campaign (CHC-1) covering 28 municipalities has been implemented. Although only a single penetration rate was initially planned by CHC-1 for all municipalities, outcomes in the different municipalities varied considerably. Recently, a second phase (CHC-2) has been launched for the remaining 128 municipalities in northern China with once again a fixed penetration rate set. Here, we quantified factors that affected the penetration rates of CHC-1, developed an intervention scheme with differentiated targets for CHC-2, and compared the environmental and health benefits of the fixed- and differentiated-rate strategies. We found that the penetration rates of CHC-1 depended on per capita income, terrain slope, and population density and that such relationships could be quantified using a piecewise regression model. This model was applied to develop a differentiated-rate strategy for CHC-2. It clearly evidenced that a differentiated scheme would be more environmentally beneficial. Although the same number of rural households can achieve clean heating under both intervention scenarios, the proposed differentiated strategy can prevent 30 000 (23 000-34 000) premature deaths associated with residential heating annually compared to the 26 000 (21 000-31 000) premature deaths prevented under the fixed-rate scheme. Differences among gender and age groups and the effects of urbanization and aging are also discussed.

The presence of sulfur dioxide (SO2) in the air is a global concern because of its severe environmental and public health impacts. Recent evidence from satellite observations shows rapid changes in the spatial distribution of global SO2 emissions, but such features are generally missing in global emission inventories that use a bottom-up method due to the lack of up-to-date information, especially in developing countries. Here, we rely on the latest data available on emission activities, control measures, and emission factors to estimate global SO2 emissions for the period 1960-2014 on a 0.1° × 0.1° spatial resolution. We design two counterfactual scenarios to isolate the contributions of emission activity growth and control measure deployment on historical SO2 emission changes. We find that activity growth has been the major factor driving global SO2 emission changes overall, but control measure deployment is playing an increasingly important role. With effective control measures deployed in developed countries, the predominant emission contributor has shifted from developed countries in the early 1960s (61%) to developing countries at present (83%). Developing countries show divergency in mitigation strategies and thus in SO2 emission trends. Stringent controls in China are driving the recent decline in global emissions. A further reduction in SO2 emissions would come from a large number of developing nations that currently lack effective SO2 emission controls.

North China is among the most polluted regions in the country, and human exposure to PM

Ozone (O3) isopleths describe the nonlinear responses of O3 concentrations to changes in nitrogen oxides (NOX) and volatile organic compounds (VOCs) and thus are pivotal to the determination of O3 control requirements. In this study, we innovatively use the Community Multiscale Air Quality model with the high-order decoupled direct method (CMAQ-HDDM) to simulate O3 pollution of China in 2017 and derive O3 isopleths for individual cities. Our simulation covering the entire China Mainland suggests severe O3 pollution as 97% of the residents experienced at least 1 day, in 2017, in excess of Chinese Level-II Ambient Air Quality Standards for O3 as 160 μg·m-3 (81.5 ppbV equally). The O3 responses to emissions of precursors vary widely across individual cities. Densely populated metropolitan areas such as Jing-Jin-Ji, Yangtze River Delta, and Pearl River Delta are following NOX-saturated regimes, where a small amount of NOX reduction increases O3. Ambient O3 pollution in the eastern region generally is limited by VOCs, while in the west by NOX. The city-specific O3 isopleths generated in this study are instrumental in forming hybrid and differentiated strategies for O3 abatement in China.

Rural residential energy switching from solid fuels to electricity and natural gas has resulted in substantial health benefits in China. Here, we quantitatively estimated the environmental and health benefits of stove upgrading, energy switching, and the interaction of stove upgrading and energy switching in rural mainland China during the period of 1980-2014. Driven by government intervention, technical progress, and socioeconomic development, domestic stoves have been upgraded from a domination of open-fire and traditional stoves to energy-saving, clean stoves, and gas range/electric stoves. Furthermore, stove upgrading significantly contributed to the overall reductions in PM2.5 emissions (25%), ambient and indoor PM2.5 concentrations (49 and 28%), population exposure (31%), and premature deaths (37%) attributable to residential emissions. The interaction between stove upgrading and energy switching resulted in an additional 15% reduction in premature deaths. The influences of the residential sector and the beneficial effects of stove upgrading and energy switching are magnified along the causal path from emissions to health impacts. The overall benefit of the transition in residential energy would be substantially underestimated without considering stove upgrading.

Autonomy of language learners in technology-supported learning environments has attracted much scholarly attention. However, few studies, to date, have examined the issue in the emerging context of...

Historically, beehive coke ovens (BCOs) were extensively operated in China and emitted large quantities of pollutants, including primary PM2.5 and secondary PM2.5 precursors, and other climate forc...

Coal abatement actions for pollution reduction often target total coal consumption. The health impacts of coal uses, however, vary extensively among sectors. Here, we modeled the sectorial contributions of coal uses to emissions, outdoor and indoor PM2.5 (particulate matter with an aerodynamic diameter of less than 2.5 mm) concentrations, exposures, and health outcomes in China from 1970 to 2014. We show that in 2014, residential coal accounted for 2.9% of total energy use but 34% of premature deaths associated with PM2.5 exposure, showing that effects were magnified substantially along the causal path. The number of premature deaths attributed to unit coal consumption in the residential sector was 40 times higher than that in the power and industrial sectors. Emissions of primary PM2.5 were more important than secondary aerosol precursors in terms of health consequences, and indoor exposure accounted for 97% and 91% of total premature deaths attributable to PM2.5 from coal combustion in 1974 and 2014, respectively. Our assessment raises a critical challenge in the switching of residential coal uses to effectively mitigate PM2.5 exposure in the Chinese population.

The COVID-19 quarantine in China is thought to have reduced ambient air pollution. The overall exposure of the population also depends, however, on indoor air quality and human mobility and activities. Here, by integrating real-time mobility data and a questionnaire survey on time-activity patterns during the pandemic, we show that despite a decrease in ambient PM

The COVID-19 outbreak in China led to dramatic changes in human activities resulting from the sudden infection prevention and control measures. Here, we use ground-level observations and model simulations to examine the nationwide spatial–temporal variations of six air pollutants before and after the initiation of First-Level Public Health Emergency Response. The level of ambient NO2 declined significantly, and in most cities, the decline was dominated by reduced emissions. Meanwhile, the level of O3 increased significantly during this period, and the nonmeteorological factors explained the increase. For the other air pollutants (PM2.5, SO2, and CO), the observed declines on the national scale were obviously affected by the meteorological conditions. In Wuhan, significant declines were found for air pollutants except O3 and emissions dominated the changes, while in Beijing during the same period, only the level of NO2 significantly declined. This study clearly shows that the meteorological changes contributed substantially to the observed changes in most air pollutants, and this must be considered in evaluating the impacts of pollutant source changes on air quality during the specific event and in assessing source-oriented risks.

In addition to many recent actions taken to reduce emissions from energy production, industry, and transportation, a new campaign substituting residential solid fuels with electricity or natural gas has been launched in Beijing, Tianjin, and other 26 municipalities in northern China, aiming at solving severe ambient air pollution in the region. Quantitative analysis shows that the campaign can accelerate residential energy transition significantly, and if the planned target can be achieved, more than 60% of households are projected to remove solid fuels by 2021, compared with less than 20% without the campaign. Emissions of major air pollutants will be reduced substantially. With 60% substitution realized, emission of primary PM2.5 and contribution to ambient PM2.5 concentration in 2021 are projected to be 30% and 41% of those without the campaign. With 60% substitution, average indoor PM2.5 concentrations in living rooms in winter are projected to be reduced from 209 (190-230) μg/m3 to 125 (99-150) μg/m3. The population-weighted PM2.5 concentrations can be reduced from 140 μg/m3 in 2014 to 78 μg/m3 or 61 μg/m3 in 2021 given that 60% or 100% substitution can be accomplished. Although the original focus of the campaign was to address ambient air quality, exposure reduction comes more from improved indoor air quality because approximately 90% of daily exposure of the population is attributable to indoor air pollution. Women benefit more than men.

Residential contributions are substantially magnified from energy use, emissions, air pollution, to health impacts., Residential contribution to air pollution–associated health impacts is critical, but inadequately addressed because of data gaps. Here, we fully model the effects of residential energy use on emissions, outdoor and indoor PM2.5 concentrations, exposure, and premature deaths using updated energy data. We show that the residential sector contributed only 7.5% of total energy consumption but contributed 27% of primary PM2.5 emissions; 23 and 71% of the outdoor and indoor PM2.5 concentrations, respectively; 68% of PM2.5 exposure; and 67% of PM2.5-induced premature deaths in 2014 in China, with a progressive order of magnitude increase from sources to receptors. Biomass fuels and coal provided similar contributions to health impacts. These findings are particularly true for rural populations, which contribute more to emissions and face higher premature death risks than urban populations. The impacts of both residential and nonresidential emissions are interconnected, and efforts are necessary to simultaneously mitigate both emission types.

The global pollutant mercury (Hg), especially as methylmercury (MeHg), threatens human and ecosystem health. But major contributors of MeHg exposure to people in China remain highly debated. We developed the China Mercury Exposure Assessment (CMEA) model, which incorporates human exposure pathways for MeHg and total Hg (THg), the interregional, including international and interprovincial, food trading as well as human physiology to provide a comprehensive system that can evaluate the pathway of Hg forms to human consumers in China. Based on the CMEA model that employed the most comprehensive and recent data, we have found that the Probable Daily Intake (PDI) of MeHg for the Chinese population was 0.057 (range: 0.036–0.091 as 60% confidence interval) μg·kg−1·day−1, while that of THg was 0.35 (range: 0.22–0.55) μg·kg−1·day−1. MeHg exposure was dominated by fish intake, especially by farm-raised freshwater fish due to higher consumption of these fish. In 2011, fish intake contributed to 56% to the total MeHg exposure, followed by rice (26%). Consumption of farm-raised fish reduced human exposure to MeHg by 33%. On the other hand, interregional food trading increased MeHg exposure of the Chinese population, as a whole, by 7.6%. The international and interprovincial food trades contributed to 5.1% and 22% of MeHg intake, respectively. For the whole China, fish intake related exposure to MeHg was highest for the Eastern and Northeastern populations, while Tibetans were chronically exposed to the highest MeHg from other sources. Our findings highlight the importance of farmed fish and food trade for MeHg exposure. Keywords: Methylmercury exposure, Farmed fish, Freshwater fish, Marine fish, Interregional food trade, Physiologically Based Pharmacokinetic (PBPK) model

Rural household energy use for cooking and heating is an important source of air pollutants in China, as it affects both human health and climate change. However, the magnitude of rural household energy use, especially during the recent rapid socioeconomic transition period, has not been well quantified. Here, we present first-hand nationwide data from a 34,489-household energy-mix survey and a 1,670-household fuel-weighing campaign. We found that the consumption of wood and crop residues in rural China decreased by 63% and 51%, respectively, from 1992 to 2012, and these decreases were much greater than the 15% and 8%, respectively, reported by the International Energy Agency and Food and Agriculture Organization. The rapid residential energy transition over these two decades was primarily driven by the rapid socioeconomic development. One important implication of this transition is the significant reduction in the emissions of major air pollutants, especially incomplete combustion products leading to significant impacts on health and climate. Use of wood and crop residue for cooking and heating in rural China is a significant source of carbon emissions and air pollution. Using a survey of more than 34,000 households, researchers show that between 1992 and 2012 usage of these fuels decreased by much more than previous estimates, due primarily to rising incomes.

In China, rural migrant workers (RMWs) are employed in urban workplaces but receive minimal resources and welfare. Their residential energy use mix (REM) and pollutant emission profiles are different from those of traditional urban (URs) and rural residents (RRs). Their migration towards urban areas plays an important role in shaping the magnitudes and spatial patterns of pollutant emissions, ambient PM2.5 (fine particulate matter with a diameter smaller than 2.5 μm) concentrations, and associated health impacts in both urban and rural areas. Here we evaluate the impacts of RMW migration on REM pollutant emissions, ambient PM2.5, and subsequent premature deaths across China. At the national scale, RMW migration benefits ambient air quality because RMWs tend to transition to a cleaner REM upon arrival at urban areas—though not as clean as urban residents'. In 2010, RMW migration led to a decrease of 1.5 μg/m3 in ambient PM2.5 exposure concentrations (Cex) averaged across China and a subsequent decrease of 12,200 (5700 to 16,300, as 90% confidence interval) in premature deaths from exposure to ambient PM2.5. Despite the overall health benefit, large-scale cross-province migration increased megacities' PM2.5 levels by as much as 10 μg/m3 due to massive RMW inflows. Model simulations show that upgrading within-city RMWs' REMs can effectively offset the RMW-induced PM2.5 increase in megacities, and that policies that properly navigate migration directions may have potential for balancing the economic growth against ambient air quality deterioration. Our study indicates the urgency of considering air pollution impacts into migration-related policy formation in the context of rapid urbanization in China. Keywords: Rural migrant works, Urbanization in China, Ambient air pollution, Particulate matter, Human health

Significance At present, many environmental laws and regulations are enforced in China, but they are often not well evaluated for their performance. In this study, the health effects of beehive coke oven operations, the ban of the ovens, and the slow implementation of the ban were assessed quantitatively, showing the importance of not only the legislation but also the implementation of the law. This study provides a good example that shows how environmental legislation and implementation can be evaluated to scientifically support decision making., Environmental legislation and proper implementation are critical in environmental protection. In the past, beehive coke ovens (BCOs) were popular in China, resulting in enormous emissions of benzo[a]pyrene (BaP), a common indicator of carcinogenic polycyclic aromatic hydrocarbons. BCOs were banned by the Coal Law in 1996. Although BCO numbers have declined since the ban, they were not eliminated until 2011 due to poor implementation. Here, we present the results of a quantitative evaluation of the health effects of historical BCO operation, the health benefits of the ban, and the adverse impacts of the poor implementation of the ban. With only limited official statistics available, historical and geospatial data about BCOs were reconstructed based on satellite images. Emission inventories of BaP from BCOs were compiled and used to model atmospheric transport, nonoccupational population exposure, and induced lung cancer risk. We demonstrated that more than 20% of the BaP in ambient air was from BCOs in the peak year. The cumulative nonoccupational excess lung cancer cases associated with BaP from BCOs was 3,500 (±1,500) from 1982 to 2015. If there was no ban, the cases would be as high as 9,290 (±4,300), indicating the significant health benefits of the Coal Law. On the other hand, if the ban had been fully implemented immediately after the law was enforced in 1996, the cumulative cases would be 1,500 (±620), showing the importance of implementing the law.

Household air pollution is considered to be among the top environmental risks in China. To examine the performance of improved stoves for reduction of indoor particulate matter (PM) emission and exposure in rural households, individual inhalation exposure to size-resolved PM was investigated using personal portable samplers carried by residents using wood gasifier stoves or improved coal stoves in a rural county in Central China. Concentrations of PM with different sizes in stationary indoor and outdoor air were also monitored at paired sites. The stationary concentrations of size-resolved PM in indoor air were greater than those in outdoor air, especially finer particles PM0.25. The daily averaged exposure concentrations of PM0.25, PM1.0, PM2.5 and total suspended particle for all the surveyed residents were 74.4±41.1, 159.3±74.3, 176.7±78.1 and 217.9±78.1μg/m3, respectively. Even using the improved stoves, the individual exposure to indoor PM far exceeded the air quality guideline by WHO at 25μg/m3. Submicron particles PM1.0 were the dominant PM fraction for personal exposure and indoor and outdoor air. Personal exposure exhibited a closer correlation with indoor PM concentrations than that for outdoor concentrations. Both inhalation exposure and indoor air PM concentrations in the rural households with gasifier firewood stoves were evidently lower than the reported results using traditional firewood stoves. However, local governments in the studied rural areas should exercise caution when widely and hastily promoting gasifier firewood stoves in place of improved coal stoves, due to the higher PM levels in indoor and outdoor air and personal inhaled exposure.

Air pollution exposure depends not only on outdoor but also on indoor air quality and human activities. The outbreak of coronavirus in 2019 occurred close to the Spring Festival in China, when many rural-to-urban workers moved to their hometowns, resulting in increased household (HH) consumption of solid fuels for space heating in the rural north. In this study, field measurements of HH PM2.5 (particulate matter with an aerodynamic size ⩽2.5 μm) from a rural village were performed to evaluate changes in indoor, outdoor, and total exposure during the quarantine. Both indoor and outdoor PM2.5 were, as expected, higher during the heating period than during the non-heating period, resulting in much more exposure during the heating season. Indoor exposure accounted for up to 87% and 95% of the total PM2.5 exposure during the non-heating and heating periods, respectively. The contributions of indoor exposure associated with internal sources were 46% and 66%, respectively. Indoor coal combustion resulted in an increment of about 62 ± 12 μg m−3 in indoor PM2.5 exposure. Due to the quarantine, the indoor-originated PM2.5 exposure increased by 4 μg m−3 compared to that during the heating period before the lockdown. In comparison with the exposure before the quarantine during the heating period, the outdoor exposure decreased by 5 μg m−3 during the quarantine, which was mainly attributable to much less time spent outdoors, although the outdoor PM2.5 levels increased from 86 ± 49 μg m−3 to 104 ± 85 μg m−3. However, the overall exposure increased by 13 μg m−3 during the quarantine, resulting from the changes in outdoor exposure (−5 μg m−3), outdoor-originated indoor PM2.5 exposure (+9 μg m−3), PM2.5 from indoor sources before the quarantine (+5 μg m−3), and quarantine-induced indoor PM2.5 increments (+4 μg m−3). The increase in air pollution exposure during quarantine deepened concerns about the issue of HH air pollution and the clean HH energy transition actions required to eliminate traditional solid fuels.

Polycyclic aromatic hydrocarbons (PAHs) in agricultural soils, eastern China, were studied through a collection of surface samples at 109 sites. The study covered US EPA priority pollutants but also several non-priority isomers including some dibenzopyrenes which are expected to have higher toxic potentials. The total PAH concentrations varied extensively from 8.8 to 3880 μg/kg, with a geometric mean of 158 μg/kg. There were significant differences in both the concentrations and composition profiles between the south and the north regions. The overall geographical distribution pattern was strongly influenced by both the per capita gross domestic product and soil organic carbon (SOC) content. The former is an indicator of anthropogenic emissions while soil SOC content is associated with the accumulative capacities of the soils. The sequestration mechanism is an important process controlling fates of PAHs in agricultural soil.

Historically, beehive coke ovens (BCOs) were extensively operated in China and emitted large quantities of pollutants, including primary PM

In addition to many recent actions taken to reduce emissions from energy production, industry, and transportation, a new campaign substituting residential solid fuels with electricity or natural gas has been launched in Beijing, Tianjin, and 26 other municipalities in northern China, aiming at solving severe ambient air pollution in the region. Quantitative analysis shows that the campaign can accelerate residential energy transition significantly, and if the planned target can be achieved, more than 60% of households are projected to remove solid fuels by 2021, compared with fewer than 20% without the campaign. Emissions of major air pollutants will be reduced substantially. With 60% substitution realized, emission of primary PM(2.5) and contribution to ambient PM(2.5) concentration in 2021 are projected to be 30% and 41% of those without the campaign. With 60% substitution, average indoor PM(2.5) concentrations in living rooms in winter are projected to be reduced from 209 (190 to 230) μg/m(3) to 125 (99 to 150) μg/m(3). The population-weighted PM(2.5) concentrations can be reduced from 140 μg/m(3) in 2014 to 78 μg/m(3) or 61 μg/m(3) in 2021 given that 60% or 100% substitution can be accomplished. Although the original focus of the campaign was to address ambient air quality, exposure reduction comes more from improved indoor air quality because ∼90% of daily exposure of the rural population is attributable to indoor air pollution. Women benefit more than men.

Because of the severe air pollution in northern China, facemasks have gained popularity in this area in recent years. Although the results of previous studies have shown the effectiveness of wearing facemasks for intercepting particles, the individual differences and the overall health benefits of wearing facemasks have not been comprehensively documented. In this study, using both model and personal tests under various conditions, we test eight major brands of facemasks for their removal efficiencies (REs) of particulate matter (PM) in six size ranges (from 0.3 μm to >10 μm). The results are used to assess the overall exposure reduction at the individual and population levels in Beijing. We find significant differences in REs among PM sizes, facemask brands, pollution levels, and genders. Combining the information on the usage of various brands, facemask wearing rates, and PM2.5 concentrations in the ambient and indoor air in this area, we evaluate the overall effect of facemask wearing on PM2.5 exposure reduction. It is quantitatively demonstrated that because people spend most time indoors, facemask protection is limited. For facemask wearers, the overall exposure can be reduced by less than 20%, whereas the reduction rate is as low as 2.4 ± 1.6% for the entire adult populations even in the year with the highest level of pollution with an annual mean PM2.5 concentration of 102 ± 98 μg∙m−3. As a strategy of self-protection from long-term exposure to particulate matter, wearing facemasks outdoors is inferior to the installation of indoor air purifiers.

Exports from mainland China are a significant source of mercury (Hg) in the adjacent seas (Bohai Sea, Yellow Sea, East China Sea, and South China Sea) near China. A total of 240 ± 23 Mg was contributed in 2012 (30% from natural sources and 70% from anthropogenic sources), including Hg from rivers, industrial wastewater, domestic sewage, groundwater, nonpoint sources, and coastal erosion. Among the various sources, the Hg from rivers amounts to 160 ± 21 Mg and plays a dominant role. The Hg that is exported from mainland China increased from 1984 to 2013; the contributions from rivers, industrial wastewater, domestic sewage and groundwater increased, and the contributions from nonpoint sources and coastal erosion remained stable. A box model is constructed to simulate the mass balance of Hg in these seas and quantify the sources, sinks and Hg biogeochemical cycle in the seas. In total, 160 Mg of Hg was transported to the Pacific Ocean and other oceans from these seas through oceanic currents in 2012, which could have negative impacts on the marine ecosystem. A prediction of the changes in Hg exportation through 2030 shows that the impacts of terrestrial export might worsen without effective pollution reduction measures and that the Hg load in these seas will increase, especially in the seawater of the Bohai Sea, Yellow Sea, and East China Sea and in the sea margin sediments of the Bohai Sea and East China Sea.

The Three Gorges Dam (TGD) is the world's largest hydropower construction. It can significantly impact contaminant transport in the Yangtze River–East China Sea Continuum (YR–ECSC). In addition to evaluating the impact of the TGD on the deposition of contaminants in the reservoir, we also address their cycles in the river below the dam and in the coastal East China Sea. A comprehensive study of metal contaminant transport along the YR–ECSC has not been previously attempted. We quantified the fates of mercury (Hg), arsenic (As), lead (Pb), cadmium (Cd) and chromium (Cr) within the YR–ECSC, and the impacts of the TGD, by sampling water and suspended particles along the Yangtze River during spring, summer, fall, and winter and by modeling. We found that the Yangtze River transports substantial amounts of heavy metals into the coastal ocean. In 2016, riverine transport amounted to 48, 5900, 11,000, 230, and 15,000 megagrams (Mg) for Hg, As, Pb, Cd, and Cr, respectively, while other terrestrial contributions were negligible. Metal flux into the coastal ocean was primarily derived from the downstream portion of the river (84–97%), while metals transported from upstream were largely trapped in the Three Gorges Reservoir (TGR, 72%–96%). For example, 34 Mg of Hg accumulated in the TGR owing to river damming, large-scale soil erosion, and anthropogenic point source releases, while 21 Mg of Hg was depleted from the riverbed downstream owing to the altered river hydrology caused by the TGD. Overall the construction of TGD resulted in a 6.9% net decrease in the Hg burden of the East China Sea, compared to the pre-TGD period.

In the wake of rapid development of Language MOOCs (LMOOCs), numerous studies have proposed principles and guidelines to inform curriculum design. Very few of them have, however, reported on learners’ views. This study aims to contribute to this line of research by bringing in a learners’ perspective. It is based on a content analysis of 3,510 learner reviews on 41 English LMOOCs offered by a national MOOC provider in China. It focuses on Chinese EFL learners’ views of LMOOCs. The results indicate that their views pertain mainly to seven categories: (1) content design of course videos, (2) presentation design of course videos, (3) MOOC program instructors, (4) assessments and assignments, (5) course settings, (6) forum discussions, and (7) technological environment, of which the first three are of the most importance to the learners. It is argued that Chinese EFL learners’ perception of English LMOOCs might be rooted in their engagement pattern with the courses, their perceptions of the role of teachers, the design of existing English LMOOCs, and a preference for the traditional way of foreign language teaching and learning they are acquainted with before engaging with the LMOOCs. The context-specific evidence could be used as an empirical base to guide future design of LMOOCs for foreign language learning in China.

Survey data from a comprehensive national survey of ∼34 000 households were analyzed for the mix status and transition trajectory of energy for boiling water in rural Chinese households from 1992 to 2012. In 1992, ∼6% of households reported using electricity, biogas, or liquefied petroleum gas (LPG) to boil drinking water; in 2012, the proportion was ∼60%. Income per capita appeared most strongly associated with this transition toward electricity and other clean fuels. Median annual incomes for households using biomass fuels, electric kettles, and LPG were RMB 15 000, 28 000, and 30 000, respectively. Overall, the transition was most pronounced in eastern China, a region which experienced relatively higher rates of economic growth over the same 20-year period. Energy type preferences appear to be highly dependent on fuel accessibility such that coal and straw usage was higher in provinces with higher coal and grain production. These trends suggest that electric kettle use would likely increase from ∼29% (2012) to ∼60% by 2030, at which point5% of rural households would be expected to boil with solid fuels. Recent evidence suggests that this transition could contribute to reductions in water-related gastrointestinal illness as well as reductions in air pollutant emissions in rural China.

Exposure to and the related burden of diseases caused by pollution from solid fuel cooking, known as household air pollution (HAP), has been incorporated in the assessment of the Global Burden of Diseases (GBD) project. In contrast, HAP from space heating using solid fuels, prevalent in countries at middle or high altitudes, is less studied and missing from the GBD assessment. China is an ideal example to estimate the bias of exposure and burden of diseases assessment when space heating is neglected, considering its remarkably changing demands for heating from the north to the south and a large solid-fuel-dependent rural population. In this study, based on a meta-analysis of 27 field measurement studies in rural China, we derive the indoor PM2.5 (fine particulate matter with an aerodynamic diameter smaller than 2.5 μm) concentration for both the heating and non-heating seasons. Combining this dataset with time-activity patterns and percentage of households using solid fuels, we assess the population-weighted annual mean exposure to PM2.5 (PWE) and the health impacts associated with HAP in mainland rural China by county for the year 2010. We find that ignoring heating impacts leads to an underestimation in PWE estimates by 38 μg/m3 for the nationwide rural population (16 to 40 as interquartile range) with substantial negative bias in northern provinces. Correspondingly, premature deaths and disability-adjusted life years will be underestimated by approximately 30 × 103 and 60 × 104 in 2010, respectively. Our study poses the need for incorporating heating effects into HAP risk assessments in China as well as globally.

Hundreds of millions of rural residents have migrated to cities in China in recent years. Different lifestyles and living conditions lead to substantial changes in their household energy. Here, we present the result of a survey on direct household energy use of low-skilled rural-to-urban migrants in Beijing. The migrants moved up the energy ladder immediately after arriving in the city by replacing biomass fuels with coal, electricity, and liquefied petroleum gas. After the original shift, pattern of household energy use by the migrants has not changed much over decades, likely due to the long-existing household registration system (Hukou). As a result, the mix of energy types used by the rural-to-urban migrants were different from those by long-term urban residents, although total quantities were similar. Shifting from biomass fuels to coal, the migrants emitted 2.4 times more non-neutral CO2 than rural residents and 14% more than urban residents. The migration also resulted in significant increase in emissions of SO2 and mercury but dramatic decreases in some incomplete combustion products including particulate matter. All these changes have significant implication on air quality, health, and climate considering the scale of urbanization in China.

Residential solid fuel combustion is a major source of many pollutants, resulting in significant impacts on air quality and human health. Improved stoves, especially some modern gasifier biomass models, are being deployed to alleviate household and ambient air pollution. Pollutant emissions from coal burning in improved metal stoves (n = 11) and wood combustion in modern gasifier stoves (n = 8) were measured in field in Hubei, China. The emissions of CO, TSP, OC, EC, and PAHs from coal burning in the improved iron stoves were generally lower than previously reported results for coal in traditional stoves. For pollutants from wood combustion in the gasifier stoves, the emissions were less than literature-reported values for wood burned in traditional stoves, comparable to those in improved stoves, but appeared to be higher than those for pellets in gasifier stoves in laboratory tests. The limitations of scarce data and large variances result in statistical insignificance. Daily emissions of targeted pollutants per household were found to be higher for wood burners, compared with households relying on coal. The gasifier stove had relatively high thermal efficiencies, but emissions of most air pollutants per delivered energy were not significantly different from those from the coal burning in improved iron stoves. Moreover, higher emissions of OC, EC, and PAHs were observed, indicating that caution and additional testing will be needed while designing future clean cookstove intervention programs.

There is wide concern about polycyclic aromatic hydrocarbons (PAHs) because of their carcinogenic and mutagenic potential. The coking industry is an important source of PAHs. In this study, 36 arable soil samples, a sensitive medium from the perspective of food safety and health, were collected from one of the largest coke production bases in China. The concentration of total 21 PAHs ranged from 294 to 1665 ng g−1, with a mean of 822 ± 355 ng g−1. Approximately 60% of the soil samples were heavily polluted with the level higher than 600 ng g−1. Particularly high abundances of high molecular weight PAHs were found, and the calculated BaPeq was as high as 54.3 ng g−1. Soil PAH levels were positively correlated with soil organic matter content. The soil PAHs were from complex mixture sources, and high-temperature pyrogenic sources were most likely responsible for the heavy PAH contamination. Effective control strategies and probable remediation approaches should be proposed to improve soil quality.

Polycyclic aromatic hydrocarbons (PAHs) are a group of pollutants of widespread concerns. Gaseous and size-segregated particulate-phase PAHs were collected in indoor and outdoor air in rural households. Personal exposure was measured and compared to the ingestion exposure. The average concentrations of 28 parent PAHs and benzo(a)pyrene (BaP) were 9000 � 8390 and 131 � 236 ng/m 3 for kitchen, 2590 � 2270 and 43 � 95 ng/m 3 for living room, and 2800 � 3890 and 1.6 � 0.7 ng/m 3 for outdoor air, respectively. The mass percent of high molecular weight (HMW) compounds with 5-6 rings contributed 1.3% to total 28 parent PAHs. Relatively higher fractions of HMW PAHs were found in indoor air compared to outdoor air. Majorities of particle- bound PAHs were found in the finest PM0.25, and the highest levels of fine PM0.25-bound PAHs were in the kitchen using peat and wood as energy sources. The 24-h personal PAH exposure concentration was 2100 � 1300 ng/m 3 . Considering energies, exposures to those using wood were the highest. The PAH inhalation exposure comprised up to about 30% in total PAH exposure through food ingestion and inhalation, and the population attributable fraction (PAF) for lung cancer in the region was 0.85%. The risks for inhaled and ingested intakes of PAHs were 1.0 9 10 � 5 and 1.1 9 10 � 5 , respectively. Practical Implications Household air pollution, personal inhalation, and digestion exposure of PAHs were measured and studied for the influence of household energies. Much high PAH levels and more HMW fractions were observed in kitchens com- pared to other microenvironments such as living rooms and outdoors, due to household solid fuel consumption. The use of wood and peat produced the heaviest PAH pollution and personal exposure. The population attributable frac- tion (PAF) for lung cancer due to PAH inhalation exposure in the region was 0.85%, higher than the world and national average level, indicating more public concerns and protection actions to protect air quality and human health.

Personal exposure to size-segregated particles among rural residents in Shanxi, China in summer, 2011 were investigated using portable carried samplers (N = 84). Household air pollution was simultaneously studied using stationary samplers in nine homes. Information on household fuel types, cooking activity, smoking behavior, kitchen ventilation conditions etc., were also collected and discussed. The study found that even in the summer period, the daily average concentrations of PM

Emission quantification of primary particulate matter (PM) is essential for assessment of its related climate and health impacts. To reduce uncertainty associated with global emissions of PM2.5, PM10, and TSP, we compiled data with high spatial (0.1° × 0.1°) and sectorial (77 primary sources) resolutions for 2007 based on a newly released global fuel data product (PKU-FUEL-2007) and an emission factor database. Our estimates for developing countries are higher than those previously reported. Spatial bias associated with large countries could be reduced by using subnational fuel consumption data. Additionally, we looked at temporal trends from 1960 to 2009 at country-scale resolution. Although total emissions are still increasing in developing countries, their intensities in terms of gross domestic production or energy consumption have decreased. PM emitted in developed countries is finer owing to a larger contribution from nonindustrial sources and use of abatement technologies. In contrast, countries like China, with strong industry emissions and limited abatement facilities, emit coarser PM. The health impacts of PM are intensified in hotspots and cities owing to covariance of sources and receptors. Although urbanization reduces the per person emission, overall health impacts related to these emissions are heightened because of aggregation effects.

International audience; Black carbon (BC) plays an important role in both climate change and health impact. Still, BC emissions as well as the historical trends are associated with high uncertainties in existing inventories. In the present study, global BC emissions from 1960 to 2007 were estimated for 64 sources, by using recompiled fuel consumption and emission factor data sets. Annual BC emissions had increased from 5.3 (3.4-8.5 as an interquartile range) to 9.1 (5.6-14.4) teragrams during this period. Our estimations are 11-16% higher than those in previous inventories. Over the period, we found that the BC emission intensity, defined as the amount of BC emitted per unit of energy production, had decreased for all the regions, especially China and India. Improvements in combustion technology and changes in fuel composition had led to an increase in energy use efficiency, and subsequently a decline of BC emission intensities in power plants, the residential sector, and transportation. On the other hand, the BC emission intensities had increased in the industrial and agricultural sectors, mainly due to an expansion of low-efficiency industry (coke and brick production) in developing countries and to an increasing usage of diesel in agriculture in developed countries.

Emission characterization of polycyclic aromatic hydrocarbons (PAHs) from residential combustion of crop residues, woody material, coal, and biomass pellets in domestic stoves in rural China are compared in term of emission factors (EFs), influencing factors, composition profiles, isomer ratios and phase distributions. The EFs of PAHs vary by two orders of magnitude among fuel types suggesting that a detailed fuel categorization is useful in the development of an emission inventory and potential in emission abatement of PAHs by replacing dirty fuels with relatively cleaner ones. The influence of fuel moisture in biomass burning is non-linear. Biofuels with very low moisture display relatively high emissions as do fuels with very high moisture. Bituminous coals and brushwood yield relatively large fractions of high molecular PAHs. The emission factor of Benzo(a)pyrene equivalent quantity for raw bituminous coal is as high as 52 mg/kg, which is 1–2 orders of magnitude higher than the other fuels. For source diagnosis, high molecular weight isomers are more informative than low molecular weight ones and multiple ratios could be used together whenever possible.

Placenta and umbilical cord blood are important media for investigating maternal-fetal exposure to environmental pollutants. Historically hexachlorocyclohexanes (HCHs) were once widely-used in China. In this study, residues of HCHs were measured in placenta and umbilical cord blood samples for 40 women from Beijing. The measured median values of HCHs were 62.0 and 68.8 ng/g fat in placenta and umbilical cord blood, respectively. Concentrations of HCHs in placenta and umbilical cord blood of urban cohort were higher than those of rural group due to enhanced consumption of fish, meat, and milk. Residues of HCHs in placenta were significantly correlated with total food consumption, dietary intake, and maternal age, and could be predicted using the parameters dependent upon ingestion of meat and milk. The transplacental exposure of fetuses to HCHs was revealed by a close association between the residual levels in the paired placenta and the paired umbilical cord blood samples.

Air pollutants from residential solid fuel combustion are attracting growing public concern. Field measured emission factors (EFs) of various air pollutants for solid fuels are close to the reality and urgently needed for better emission estimations. In this study, emission factors of particulate matter (PM), organic carbon (OC), elemental carbon (EC), and various polycyclic aromatic hydrocarbons (PAHs) from residential combustions of coal briquette, coal cake, and wood were measured in rural Heshun County, China. The measured EFs of PM, OC, and EC were 8.1-8.5, 2.2-3.6, 0.91-1.6 g/kg for the wood burnt in a simple metal stove, 0.54-0.64, 0.13-0.14, 0.040-0.0041 g/kg for the briquette burned in an improved stove with a chimney, and 3.2-8.5, 0.38-0.58, 0.022-0.052 g/kg for the homemade coal cake combusted in a brick stove with a flue, respectively. EFs of 28 parent PAHs, 4 oxygenated PAHs, and 9 nitro-PAHs were 182-297, 7.8-10, 0.14-0.55 mg/kg for the wood, 14-16, 1.7-2.6, 0.64-0.83 mg/kg for the briquette, and 168-223, 4.7-9.5, 0.16-2.4 mg/kg for the coal cake, respectively. Emissions from the wood and coal cake combustions were much higher than those for the coal briquette, especially true for high molecular weight PAHs. Most EFs measured in the field were higher than those measured in stove combustions under laboratory conditions.

High levels of polybrominated diphenyl ethers (PBDEs) have been extensively reported in urban areas and at e-waste recycling sites in coastal China. However, data are scarce in northern China and are not available in rural areas at all. In addition, it is often believed that air concentrations in rural areas are lower than those in urban areas without distinguishing rural residential areas and open fields. In this study, air samples were collected at 17 sites covering urban and rural (residential and open field) areas in northern China using active samplers. With BDE-209 dominated in all congeners, the average concentrations of BDE-209 (41 +/- 72 pg/m(3)) and other 13 PBDEs (16 +/- 12 pg/m(3)) were significantly lower than those found in south China, such as in Guangzhou or Hong Kong. On average, the total PBDE concentrations at the urban sites were 2.2 and 2.9 times of those at the rural residential and field sites, respectively. (C) 2012 Elsevier Ltd. All rights reserved.

243 surface soil samples were collected from the Yangtze River Delta (YRD) region, and the concentration distributions and compositional profiles of 27 parent PAHs (PPAHs), nitro- and oxy-derivatives (NPAHs and OPAHs), respectively, and health risk of 16 PPAHs were determined. Atmospheric samples were collected at two sites with high topsoil concentrations of PAHs to assist in identifying the emission sources of PPAHs. The total concentrations of PPAHs, NPAHs and OPAHs fell in the ranges of 21.0-3563.2 ng/g, 0.4-4.6 ng/g and 2.1-834.1 ng/g, respectively. PPAHs in topsoil were dominated by low and medium molecular weight species. The main components of OPAHs were 9FO and ANQ. For NPAHs, only 1N-NAP was frequently detected. Overall, the northern parts of the YRD region were more heavily contaminated by PPAHs and their corresponding derivatives. The soil TOC fraction and GDP per capita were significantly correlated with the spatial distribution of PPAHs. Specific ratios of isomeric species and principal component analysis (PCA) designated combustion of industrial coal and biomass, and traffic exhaust as the main mixed emission sources of PPAHs in surface soils in this region. The detected NPAHs and OPAHs were significantly associated with the corresponding PPAHs. The estimated incremental lifetime cancer risk attributed to 16 PPAHs in surface soil was greater than 10-6, indicating a potential risk of contracting cancer by exposure to topsoil from the YRD region. The cumulative probability of cancer risk for both adults and children via three exposure pathways followed the sequence of dermal contact > ingestion > inhalation.

Based on an analysis of measured data and distribution factors, we developed the China Aquatic Mercury Release (CAMR) model, which we used to calculate an inventory of mercury (Hg) that was released to aquatic environments from primary anthropogenic sources in China. We estimated a total release of 98 tons of Hg in 2012, including coal-fired power plants (17%), nonferrous metal smelting (33%), coal mining and washing (25%), domestic sewage (17%), and other sectors (8.3%). The total primary anthropogenic Hg released to aquatic environments in China decreased at an annual average rate of 1.7% between 2001 and 2012, even though GDP grew at an annual average rate of 10% during this period. In addition to the Hg that was released to aquatic environments in China's provinces, we estimated the Hg release amounts and intensities (in g/km(2)·yr) for China's 58 secondary river basins. The highest aquatic Hg release intensities in China were associated with industrial wastewater on the North China Plain and domestic sewage in eastern China and southern China. We found that the overall uncertainty of our inventory ranges from -22% to 32%. We suggest that the inventory provided by this study can help establish a more accurate map of regional and global Hg cycling; it also has implications for water quality management in China.

Residential wood combustion is one of the important sources of air pollution in developing countries. Among the pollutants emitted, parent polycyclic aromatic hydrocarbons (pPAHs) and their derivatives, including nitrated and oxygenated PAHs (nPAHs and oPAHs), are of concern because of their mutagenic and carcinogenic effects. In order to evaluate their impacts on regional air quality and human health, emission inventories, based on realistic emission factors (EFs), are needed. In this study, the EFs of 28 pPAHs (EF(PAH28)), 9 nPAHs (EF(PAHn9)), and 4 oPAHs (EF(PAHo4)) were measured for residential combustion of 27 wood fuels in rural China. The measured EF(PAH28), EF(PAHn9), and EF(PAHo4) for brushwood were 86.7 ± 67.6, 3.22 ± 1.95 × 10(-2), and 5.56 ± 4.32 mg/kg, which were significantly higher than 12.7 ± 7.0, 8.27 ± 5.51 × 10(-3), and 1.19 ± 1.87 mg/kg for fuel wood combustion (p0.05). Sixteen U.S. EPA priority pPAHs contributed approximately 95% of the total of the 28 pPAHs measured. EFs of pPAHs, nPAHs, and oPAHs were positively correlated with one another. Measured EFs varied obviously depending on fuel properties and combustion conditions. The EFs of pPAHs, nPAHs, and oPAHs were significantly correlated with modified combustion efficiency and fuel moisture. Nitro-naphthalene and 9-fluorenone were the most abundant nPAHs and oPAHs identified. Both nPAHs and oPAHs showed relatively high tendencies to be present in the particulate phase than pPAHs due to their lower vapor pressures. The gas-particle partitioning of freshly emitted pPAHs, nPAHs, and oPAHs was primarily controlled by organic carbon absorption.

Indoor combustion of crop residues for cooking or heating is one of the most important emission sources of polycyclic aromatic hydrocarbons (PAHs) in developing countries. However, data on PAH emission factors (EFs) for burning crop residues indoor, particularly those measured in the field, were scarce, leading to large uncertainties in the emission inventories. In this study, EFs of PAHs for nine commonly used crop residues burned in a typical Chinese rural cooking stove were measured in a simulated kitchen. The measured EFs of total PAHs averaged at 63 ± 37 mg/kg, ranging from 27 to 142 mg/kg, which were higher than those measured in chamber experiments, implying that the laboratory experiment-based emission and risk assessment should be carefully reviewed. EFs of gaseous and particulate phase PAHs were 27 ± 13 and 35 ± 23 mg/kg, respectively. Composition profiles and isomer ratios of emitted PAHs were characterized. Stepwise regressions found that modified combustion efficiency and fuel moisture were the most important factors affecting the emissions. There was 80 ± 6% of PAHs associated with PM2.5, and the mass percentage of PAHs in fine particles increased as the molecular weight increased. For freshly emitted PAHs, absorption into organic carbon, rather than adsorption, dominated the gas-particle partitioning.

Bulk deposition samples were collected in remote, rural village and urban areas of Beijing–Tianjin region, North China in spring, summer, fall and winter from 2007 to 2008. The annually averaged PAHs concentration and deposition flux were 11.81 ± 4.61 μg/g and 5.2 ± 3.89 μg/m2/day respectively. PHE and FLA had the highest deposition flux, accounting for 35.3% and 20.7% of total deposition flux, respectively. More exposure risk from deposition existed in the fall for the local inhabitants. In addition, the PAHs deposition flux in rural villages (3.91 μg/m2/day) and urban areas (8.28 μg/m2/day) was 3.8 and 9.1 times higher than in background area (0.82 μg/m2/day), respectively. This spatial variation of deposition fluxes of PAHs was related to the PAHs emission sources, local population density and air concentration of PAHs, and the PAHs emission sources alone can explain 36%, 49%, 21% and 30% of the spatial variation in spring, summer, fall and winter, respectively.

Both particulate matter (PM) and black carbon (BC) impact climate change and human health. Uncertainties in emission inventories of PM and BC are partially due to large variation of measured emission factors (EFs) and lack of EFs from developing countries. Although there is a debate whether thermal-optically measured elemental carbon (EC) may be referred to as BC, EC is often treated as the same mass of BC. In this study, EFs of PM (EF(PM)) and EC (EF(EC)) for 9 crop residues and 5 coals were measured in actual rural cooking and coal stoves using the carbon mass balance method. The dependence of the EFs on fuel properties and combustion conditions was investigated. It was found that the mean EF(PM) were 8.19 ± 4.27 and 3.17 ± 4.67 g/kg and the mean EF(EC) were 1.38 ± 0.70 and 0.23 ± 0.36 g/kg for crop residues and coals, respectively. PM with size less than 10 μm (PM(10)) from crop residues were dominated by particles of aerodynamic size ranging from 0.7 to 2.1 μm, while the most abundant size ranges of PM(10) from coals were either from 0.7 to 2.1 μm or less than 0.7 μm. Of various fuel properties and combustion conditions tested, fuel moisture and modified combustion efficiency (MCE) were the most critical factors affecting EF(PM) and EF(EC) for crop residues. For coal combustion, EF(PM) were primarily affected by MCE and volatile matter, whereas EF(EC) were significantly influenced by ash content, volatile matter, heat value, and MCE. It was also found that EC emissions were significantly correlated with emissions of PM with size less than 0.4 μm.

Residential solid fuels are widely consumed in rural China, contributing to severe household air pollution for many products of incomplete combustion, such as polycyclic aromatic hydrocarbons (PAHs) and their polar derivatives. In this study, concentrations of nitrated and oxygenated PAH derivatives (nPAHs and oPAHs) for household and personal air were measured and analyzed for influencing factors like smoking and cooking energy type. Concentrations of nPAHs and oPAHs in kitchens were higher than those in living rooms and in outdoor air. Exposure levels measured by personal samplers were lower than levels in indoor air, but higher than outdoor air levels. With increasing molecular weight, individual compounds tended to be more commonly partitioned to particulate matter (PM); moreover, higher molecular weight nPAHs and oPAHs were preferentially found in finer particles, suggesting a potential for increased health risks. Smoking behavior raised the concentrations of nPAHs and oPAHs in personal air significantly. People who cooked food also had higher personal exposures. Cooking and smoking have a significant interaction effect on personal exposure. Concentrations in kitchens and personal exposure to nPAHs and oPAHs for households using wood and peat were significantly higher than for those using electricity and liquid petroleum gas (LPG).

Daily, size-segregated particulate matter (PM) samples were collected at Peking University from March 2012 to April 2013. Seventeen indoor air samples were also collected over this period. Winter PM concentrations decreased compared with those reported a decade ago, but summer PM concentrations increased over the same time period. Increasing summer PM concentrations likely resulted from a shift in the major source of PM from primary coal burning to vehicle-associated secondary particle formation. A multiple regression model explained 62% of daily PM concentration variations, and wind direction was the most important factor controlling PM concentrations. Severe pollution was often associated with southeasterly winds, while westerly and northwesterly winds brought relatively clean air. Temperature, precipitation and relative humidity also affected PM concentrations. PM concentrations indoors were generally lower than, but significantly correlated with ambient concentrations. Indoor PM concentrations were also affected by wind speed and temperature.