Material Flow for the Intentional Use of Mercury in China

Intentional use of mercury (Hg) is an important contributor to the release of Hg into the environment. This study presents the first inventory of material flow for intentional use of Hg in China. The total amount of Hg used in China increased from 803 ± 95 tons in 2005 to its peak level of 1272 ± 110 tons in 2011. Vinyl chloride monomer (VCM) production is the largest user of Hg, accounting for over 60% of the total demand. As regulations on Hg content in products are tightening globally against the background of the Minamata Convention, the total demand will decrease. Medical devices will likely still use a significant amount of Hg and become the second largest user of Hg if no proactive measures are taken. Significant knowledge gaps exist in China for catalyst recycling sector. Although more than half of the Hg used is recycled, this sector has not drawn enough attention. There are also more than 200 tons of Hg that had unknown fates in 2011; very little information exists related to this issue. Among the final environmental fates, landfill is the largest receiver of Hg, followed by air, water, and soil

Influence of Mercury and Chlorine Content of Coal on Mercury Emissions from Coal-Fired Power Plants in China

China is the largest mercury emitter in the world and coal combustion is the most important mercury source in China. This paper updates the coal quality database of China and evaluates the mercury removal efficiency of air pollution control devices (APCDs) based on 112 on-site measurements. A submodel was developed to address the relationship of mercury emission factor to the chlorine content of coal. The mercury emissions from coal-fired power plants (CFPPs) in China were estimated using deterministic mercury emission factor model, nonchlorine-based and chlorine-based probabilistic emission factor models, respectively. The national mercury emission from CFPPs in 2008 was calculated to be 113.3 t using the deterministic model. The nonchlorine-based probabilistic emission factor model, which addresses the log-normal distribution of the mercury content of coal, estimates that the mercury emission from CFPPs is 96.5 t (P50), with a confidence interval of 57.3 t (P10) to 183.0 t (P90). The best estimate by the chlorine-based probabilistic emission factor model is 102.5 t, with a confidence interval of 71.7 to 162.1 t. The chlorine-based model addresses the influence of chlorine and reduces the uncertainties of mercury emission estimates

Deriving High-Resolution Emission Inventory of Open Biomass Burning in China based on Satellite Observations

Open biomass burning plays an important role in atmospheric pollution and in climate change. However, the current emission inventory of open biomass burning is generally of highly uncertainty because of missing small fire data and limited resolution because of the lack of localized vegetation data. In this study, the MODIS (MODerate Resolution Imaging Spectroradiometer) burned area product MCD64Al combined with the active fire product MCD14 ML, as well as a high-resolution land cover data set, were applied to develop a high-resolution emission inventory of open biomass burning in China in 2013. Total CO, CH₄, NO_<i>x</i>, NMVOC (nonmethane volatile organic compounds), SO₂, NH₃, PM_2.5, PM₁₀, OC (organic carbon), BC (black carbon), and CO₂ emissions were estimated to be 1.03 × 10⁴, 666, 536, 1.91 × 10³, 87, 138, 1.45 × 10³, 2.09 × 10³, 741, 137, and 2.45 × 10⁵ Gg, respectively. The provinces that contributed the most emissions included Heilongjiang, Henan, Shandong, and Jilin. The major source for all pollutants was cropland burning, whereas Xizang, Xinjiang, and Heilongjiang had greater emissions from natural vegetation. The temporal distribution of average provincial emissions showed that the peaks were in June and October. This study updated the emission information that may support future research and policy-making on air pollution control and GHG emission abatement

Anthropogenic Emissions of Hydrogen Chloride and Fine Particulate Chloride in China

Particulate chloride (Cl^–) can be transformed to nitryl chloride (ClNO₂) via heterogeneous reaction with nitrogen pentoxide (N₂O₅) at night. Photolysis of ClNO₂ and subsequent reactions of chlorine radical with other gases can significantly affect the atmospheric photochemistry. In China, the only available integrated anthropogenic chloride emission inventory was compiled in the 1990s with low spatial resolution, which hinders assessment of impact of ClNO₂ on current air quality. In this study, we developed an up-to-date and high-resolution anthropogenic inventory of hydrogen chloride (HCl) and fine particulate Cl^– emissions in China for 2014 with 0.1° × 0.1° resolution. Detailed local data and county-level activity data were collected and complied. The anthropogenic emissions of HCl and fine particulate Cl^– in 2014 were estimated to be 458 and 486 Gg, respectively. Biomass burning was the largest contributor, accounting for 75% of fine particulate Cl^– emission and 32% of HCl emission. Northeast China and North China Plain were the largest chloride emitters. The monthly distribution varied in different regions, due to different agricultural activities and climate conditions. This work updates the chloride emission information and improves its spatial and temporal resolution, which enables better quantification of the ClNO₂ production and its impact over China

New Insight into Atmospheric Mercury Emissions from Zinc Smelters Using Mass Flow Analysis

The mercury (Hg) flow paths from three zinc (Zn) smelters indicated that a large quantity of Hg, approximately 38.0–57.0% of the total Hg input, was stored as acid slag in the landfill sites. Approximately 15.0–27.1% of the Hg input was emitted into water or stored as open-dumped slags, and 3.3–14.5% of the Hg input ended in sulfuric acid. Atmospheric Hg emissions, accounting for 1.4–9.6% of the total Hg input, were from both the Zn production and waste disposal processes. Atmospheric Hg emissions from the waste disposal processes accounted for 40.6, 89.6, and 94.6% of the total atmospheric Hg emissions of the three studied smelters, respectively. The Zn production process mainly contributed to oxidized Hg (Hg²⁺) emissions, whereas the waste disposal process generated mostly elemental Hg (Hg⁰) emissions. When the emissions from these two processes are considered together, the emission proportion of the Hg²⁺ mass was 51, 46, and 29% in smelters A, B, and C, respectively. These results indicated that approximately 10.8 ± 5.8 t of atmospheric Hg emissions from the waste disposal process were ignored in recent inventories. Therefore, the total atmospheric Hg emissions from the Zn industry of China should be approximately 50 t

Impact Assessment of Ammonia Emissions on Inorganic Aerosols in East China Using Response Surface Modeling Technique

Ammonia (NH₃) is one important precursor of inorganic fine particles; however, knowledge of the impacts of NH₃ emissions on aerosol formation in China is very limited. In this study, we have developed China’s NH₃ emission inventory for 2005 and applied the Response Surface Modeling (RSM) technique upon a widely used regional air quality model, the Community Multi-Scale Air Quality Model (CMAQ). The purpose was to analyze the impacts of NH₃ emissions on fine particles for January, April, July, and October over east China, especially those most developed regions including the North China Plain (NCP), Yangtze River delta (YRD), and the Pearl River delta (PRD). The results indicate that NH₃ emissions contribute to 8–11% of PM_2.5 concentrations in these three regions, comparable with the contributions of SO₂ (9–11%) and NO_<i>x</i> (5–11%) emissions. However, NH₃, SO₂, and NO_<i>x</i> emissions present significant nonlinear impacts; the PM_2.5 responses to their emissions increase when more control efforts are taken mainly because of the transition between NH₃-rich and NH₃-poor conditions. Nitrate aerosol (NO₃^–) concentration is more sensitive to NO_<i>x</i> emissions in NCP and YRD because of the abundant NH₃ emissions in the two regions, but it is equally or even more sensitive to NH₃ emissions in the PRD. In high NO₃^– pollution areas such as NCP and YRD, NH₃ is sufficiently abundant to neutralize extra nitric acid produced by an additional 25% of NO_<i>x</i> emissions. The 90% increase of NH₃ emissions during 1990–2005 resulted in about 50–60% increases of NO₃^– and SO₄^2‑ aerosol concentrations. If no control measures are taken for NH₃ emissions, NO₃^– will be further enhanced in the future. Control of NH₃ emissions in winter, spring, and fall will benefit PM_2.5 reduction for most regions. However, to improve regional air quality and avoid exacerbating the acidity of aerosols, a more effective pathway is to adopt a multipollutant strategy to control NH₃ emissions in parallel with current SO₂ and NO_<i>x</i> controls in China

Gaseous Ammonia Emissions from Coal and Biomass Combustion in Household Stoves with Different Combustion Efficiencies

This study reports on the emission characteristics of NH₃ from coal and biomass combustion in the household stoves. The average NH₃ emission factors (EFs) for burning 13 coal and four biomass briquette samples in a traditional heating stove were 1.01 and 0.95 mg/g, respectively, whereas the biomass EF in a traditional cooking stove was 0.96 mg/g. These NH₃ EFs did not present significant differences and were not well-correlated with the tested fuel properties. However, the modified combustion efficiency (MCE) appeared to be well-correlated with the NH₃ EFs measured from various fuel–stove combinations. For the same fuel samples, the advanced heating stove with a high MCE had a much lower average NH₃ EF of 0.13 mg/g. Our findings indicate that household combustion may be a significant NH₃ emission source in developing countries such as China, and demonstrate that utilizing improved combustion technologies is an effective method for reducing these emissions

Mortality Burden of Cardiovascular Disease Attributable to Ozone in China: 2019 vs 2050

Due to a combination of lifestyle risk factors, the burden of cardiovascular disease (CVD) has been increasing in China, affecting an estimated 330 million people. Environmental risk factors can exacerbate these risks or independently contribute to CVD. Ozone is an overlooked and invisible risk factor, and it plays a significant role in the development of CVD. Our study provides a novel quantification of the ozone-attributable CVD mortality burden based on daily maximum 8-h average ozone concentration during May to October (6mDMA8) in Chinese adults in 2050, projected under Shared Socioeconomic Pathways 585 and 126, and using the updated WHO air quality guideline level. The study also considers the contributions made by changes in ozone exposure, population aging, population size, and baseline death rates of CVD between 2019 and 2050. While adopting a sustainable and green pathway (SSP 126) can reduce the projected magnitude of premature CVD deaths to 359,200 in 2050, it may not be sufficient to reduce the CVD mortality burden significantly. Therefore, it is crucial to implement strategies for stricter ozone control and reducing the baseline death rate of CVD to mitigate the impacts of ozone on Chinese adults

Premature Mortality Attributable to Particulate Matter in China: Source Contributions and Responses to Reductions

Excess mortality (ΔMort) in China due to exposure to ambient fine particulate matter with aerodynamic diameter ≤2.5 μm (PM_2.5) was determined using an ensemble prediction of annual average PM_2.5 in 2013 by the community multiscale air quality (CMAQ) model with four emission inventories and observation data fusing. Estimated ΔMort values due to adult ischemic heart disease, cerebrovascular disease, chronic obstructive pulmonary disease, and lung cancer are 0.30, 0.73, 0.14, and 0.13 million in 2013, respectively, leading to a total ΔMort of 1.3 million. Source-oriented CMAQ modeling determined that industrial and residential sources were the two leading sources of ΔMort, contributing to 0.40 (30.5%) and 0.28 (21.7%) million deaths, respectively. Additionally, secondary ammonium ion from agriculture, secondary organic aerosol, and aerosols from power generation were responsible for 0.16, 0.14, and 0.13 million deaths, respectively. A 30% ΔMort reduction in China requires an average of 50% reduction of PM_2.5 throughout the country and a reduction by 62%, 50%, and 38% for the Beijing–Tianjin–Hebei, Jiangsu–Zhejiang–Shanghai, and Pearl River Delta regions, respectively. Reducing PM_2.5 to the CAAQS grade II standard of 35 μg m^–3 would only lead to a small reduction in mortality, and a more stringent standard of <15 μg m^–3 would be needed for more remarkable reduction of ΔMort

Insights on Chemistry of Mercury Species in Clouds over Northern China: Complexation and Adsorption

Cloud effects on heterogeneous reactions of atmospheric mercury (Hg) are poorly understood due to limited knowledge of cloudwater Hg chemistry. Here we quantified Hg species in cloudwater at the summit of Mt. Tai in northern China. Total mercury (THg) and methylmercury (MeHg) in cloudwater were on average 70.5 and 0.15 ng L^–1, respectively, and particulate Hg (PHg) contributed two-thirds of THg. Chemical equilibrium modeling simulations suggested that Hg complexes by dissolved organic matter (DOM) dominated dissolved Hg (DHg) speciation, which was highly pH dependent. Hg concentrations and speciation were altered by cloud processing, during which significant positive correlations of PHg and MeHg with cloud droplet number concentration (<i>N</i>_d) were observed. Unlike direct contribution to PHg from cloud scavenging of aerosol particles, abiotic DHg methylation was the most likely source of MeHg. Hg adsorption coefficients <i>K</i>_ad (5.9–362.7 L g^–1) exhibited an inverse-power relationship with cloud residues content. Morphology analyses indicated that compared to mineral particles, fly ash particles could enhance Hg adsorption due to more abundant carbon binding sites on the surface. Severe particulate air pollution in northern China may bring substantial Hg into cloud droplets and impact atmospheric Hg geochemical cycling by aerosol–cloud interactions