Atmospheric Mercury Outflow from China and Interprovincial Trade

Revealing transmissions of atmospheric heavy metals hidden in the Chinese supply chain

Heavy metals (HMs) pose significant risks to human health and the environment. Identifying the sectors that play a significant role in the transmission of HMs has rarely been considered and represents an efficient method to control and manage HMs. By combining atmospheric HM emission inventories, the multi-regional input-output approach, and a betweenness-based method, this study revealed the transmission of HMs (comprehensively evaluated by the Heavy Metal Pollution Load, HMPL) in 2017. In 2017, 119.86 million tons of HMPL were transmitted through China's supply chain, and Cr was the main contributor to HMPL transmission. The results suggest that metal smelting is the primary contributor to HMPL transmission, and metal smelting in Jiangsu, Hebei, Henan, Shandong, and Anhui are the top five critical nodes. These results suggest that the sector's role changes dramatically with respect to HM control under this perspective. The role of HM emission-intensive sectors changed the most, as their production-based HMPLs accounted for 84% of the total HMPL; however, the HMPL transmitted by these sectors accounted for only 45% of the total. The critical HMPL transmission sectors identified in this study provide a basis for policy-making from a transmission perspective.

Mismatched Social Welfare Allocation and PM2.5-Related Health Damage along Value Chains within China

Value chains have played a critical part in the growth. However, the fairness of the social welfare allocation along the value chain is largely underinvestigated, especially when considering the harmful environmental and health effects associated with the production processes. We used fine-scale profiling to analyze the social welfare allocation along China's domestic value chain within the context of environmental and health effects and investigated the underlying mechanisms. Our results suggested that the top 10% regions in the value chain obtained 2.9 times more social income and 2.1 times more job opportunities than the average, with much lower health damage. Further inspection showed a significant contribution of the "siphon effect"─major resource providers suffer the most in terms of localized health damage along with insufficient social welfare for compensation. We found that inter-region atmosphere transport results in redistribution for 53% health damages, which decreases the welfare-damage mismatch at "suffering" regions but also causes serious health damage to more than half of regions and populations in total. Specifically, around 10% of regions have lower social welfare and also experienced a significant increase in health damage caused by atmospheric transport. These results highlighted the necessity of a value chain-oriented, quantitative compensation-driven policy.

Theoretical insight into mercury species adsorption on graphene-based Pt single-atom catalysts

Mercury emission from coal-fired flue gases is environmentally crucial. Revealing the interaction between mercury (Hg) and functional materials is significant to controlling emission. We conducted an investigation into the adsorption mechanism of mercury species onto graphene-based Platinum (Pt) single-atom catalysts (SACs). Single-atom Pt is the active center for Hg species chemisorption, with an adsorption energy range of 0.555-3.792 eV. In addition, Hg species adsorbed preferentially at lower temperatures. Pt/3N-GN exhibits a higher adsorption ability than Pt/SV-GN. The strong interaction of Hg0 with Pt SACs contributed to atomic-orbital hybridization between them. Further analysis revealed that s, p orbitals of Hg contribute significantly to orbital hybridization with Pt SACs. Moreover, the charge decomposition analysis confirmed that s, p orbitals of Hg hybridized with d, s orbitals of Pt SACs. The net charge transfer from Hg0 to Pt/SV-GN and Pt/3N-GN are 0.059 and 0.097 e-, respectively. The higher the charge transfers, the more intense the electron and orbital interaction between Hg and the surface. Consequently, Pt/3N-GN is a highly effective catalyst for Hg adsorption.

Chinese environmentally extended input-output database for 2017 and 2018

Environmental footprint analyses for China have gained sustained attention in the literature, which rely on quality EEIO databases based on benchmark input-output (IO) tables. The Chinese environmentally extended input-output (CEEIO) database series provide publically available EEIO databases for China for 1992, 1997, 2002, 2007, and 2012 with consistent and transparent data sources and database structure. Based on the latest benchmark IO tables for China for 2017 and 2018, here we develop the corresponding 2017 and 2018 CEEIO databases following the same method used to develop previous CEEIO databases. The 2017 and 2018 CEEIO databases cover 44 and 28 types of environmental pressures, respectively, and consider multiple sector classifications including ones consistent with previous CEEIO databases and ones following the 2017 China's national economy industry classification standard. A notable improvement in the 2017 and 2018 CEEIO databases is the comprehensive inclusion of CO2 emissions from additional industrial processes. This work provides a consistent update of the CEEIO database and enables a wide range of timely environmental footprint analyses related to China.

Measurement of air-pollution inequality through a three-perspective accounting model

China is suffering from serious air pollution. Regional air quality varies significantly due to intensive inter-provincial trades, diversified resource endowments and complicated economic structures. This study breaks the limitations of measuring environmental inequality only from a single perspective and establishes a three-perspective atmospheric pollutant equivalents accounting model (or APE accounting model) for air-pollution inequality assessment under environmentally-extend multi-regional input-output framework. From three perspectives of local production (i.e. production-based), final demand (i.e. consumption-based) and primary supply (i.e. income-based), APE emissions, APE transfers and environmental Gini coefficient are investigated to exam emission responsibilities of various impact factors, evaluate the impacts of inter-provincial trades on pollutants transfers, and characterize regional emission inequalities at both provincial and sectoral levels. The results indicate that local emitters are merely parts of contributors to air pollution. Direct emitters like Hebei Province, primary suppliers like Inner Mongolia and final consumers like Shandong Province induce large amounts of air pollutants as embedded within various economic activities. Because of unequal supply-demand levels and complex exchange mechanisms, three-perspective APE emissions are significantly heterogeneous, especially in mining, construction, energy and material-transformation sectors. Particularly, inequality of the mining sector in embodied emissions has the highest environmental Gini coefficient (0.881). This model provides a framework to assess regional environmental inequality and its findings provide scientific bases for the formulation of desired regional air pollution control policies.

Eight-year dry deposition of atmospheric mercury to a tropical high mountain background site downwind of the East Asian continent

Atmospheric deposition, either dry or wet, has been identified as an important pathway of mercury (Hg) input to terrestrial and aquatic systems. Although East Asia is the major atmospheric Hg emission source region, very few studies have been conducted to quantify atmospheric Hg deposition in its downwind region. In this study, 8-year (2009-2016) atmospheric Hg dry deposition was reported at the Lulin Atmospheric Background Station (LABS), a high mountain forest site in central Taiwan. Dry deposition of speciated Hg was estimated using a bi-directional air-surface flux exchange model for gaseous elemental mercury (GEM) and dry deposition models for gaseous oxidized mercury (GOM) and particulate-bound mercury (PBM), making use of the monitored speciated atmospheric Hg concentrations. Annual total Hg dry deposition ranged from 51.9 to 84.9 μg m^-2 yr^-1, with a multi-year average of 66.1 μg m^-2 yr^-1. Among the three forms of atmospheric Hg, GEM was the main contributor to the total dry deposition, contributing about 77.8% to the total, due to the high density of forest canopy as well as the much higher concentration of GEM than GOM and PBM at LABS. Mercury dry deposition is higher in winter and spring than in summer and fall, partly due to the elevated Hg concentrations associated with air masses from East and Southeast Asia where with high atmospheric Hg emissions. The mean annual dry/wet deposition ratio of 2.8 at LABS indicated that Hg deposition to forest landscape was governed by dry rather than wet deposition.

Temporal changes in atmospheric mercury concentrations at a background mountain site downwind of the East Asia continent in 2006-2016

Atmospheric mercury (Hg) has been monitored at the Lulin Atmospheric Background Station (LABS) in Taiwan since April 2006 and is still continuing. Here we reported the trend in gaseous elemental Hg (GEM) concentrations at LABS between April 2006 and December 2016, before the Minamata Convention on Mercury entered into force in 2017. Previous research indicated nighttime (0-8 am) data collected at LABS are better representative of regional influence. Therefore, only nighttime GEM data were used for trend analysis. A significant decreasing trend in GEM at a rate of -1.5% yr^-1 (-0.022 ng m^-3 yr^-1, p < 0.01) was found, comparable to the decreasing trends observed in Europe, North America, South Africa, and over the North Atlantic Ocean. Five major GEM source regions to the LABS were identified, including northern Indochina Peninsula, China, Northeast Asia, the Pacific Ocean, and South China Sea. Significant decreasing trends in GEM were found for air masses coming from northern Indochina Peninsula (-0.042 ng m^-3 yr^-1, -2.6% yr^-1, p < 0.01), China (-0.041 ng m^-3 yr^-1, -2.4% yr^-1, p < 0.01), Northeast Asia (-0.031 ng m^-3 yr^-1, -2.0% yr^-1, p < 0.05), and the Pacific Ocean (-0.022 ng m^-3 yr^-1, -1.7% yr^-1, p < 0.05). Decreasing GEM trend (-0.020 ng m^-3 yr^-1, -1.5% yr^-1), but insignificant (p > 0.05), was also found for air masses coming from South China Sea. The decreasing trends observed with air from the Pacific Ocean and South China Sea indicated declining background GEM concentrations in Northern Hemisphere. Decrease in GEM concentrations at the LABS was in agreement with the reduction in atmospheric Hg export from the East Asia continent caused by changes in Hg emission quantity and speciation, and temporal and spatial distribution in emission sources that have been suggested by recent research. Additionally, changes in the frequency distribution of air mass origins and transport paths may also contribute to the changes in GEM concentrations at LABS.