Recent decrease trend of atmospheric mercury concentrations in East China: the influence of anthropogenic emissions

Measurements of gaseous elemental Hg (GEM), other air pollutants including SO₂, NO_x, O₃, PM_2.5, CO, and meteorological conditions were carried out at Chongming Island in East China from March 1 in 2014 to December 31 in 2016. During the sampling period, GEM concentrations significantly decreased from 2.68&amp;thinsp;&amp;plusmn;&amp;thinsp;1.07&amp;thinsp;ng&amp;thinsp;m^&amp;minus;3 in 2014 to 1.60&amp;thinsp;&amp;plusmn;&amp;thinsp;0.56&amp;thinsp;ng&amp;thinsp;m^&amp;minus;3 in 2016. Monthly mean GEM concentrations showed a significant decrease with a rate of &amp;minus;0.60&amp;thinsp;ng&amp;thinsp;m^&amp;minus;3&amp;thinsp;yr^&amp;minus;1 (R²&amp;thinsp;=&amp;thinsp;0.6389, p&amp;thinsp;<&amp;thinsp;0.01 significance level). Combining the analysis of potential source contribution function (PSCF), principle component analysis (PCA), and emission inventory, we found that Yangtze River Delta (YRD) region was the dominant source region of atmospheric mercury in Chongming Island and the main source industries included coal-fired power plants, coal-fired industrial boilers, and cement clinker production. We further quantified the effect of emission change on the air Hg concentration variations at Chongming Island through a coupled method of trajectory clusters and air Hg concentrations. It was find that the reduction of domestic emissions was the main driver of GEM decline in Chongming Island, accounting for 66&amp;thinsp;% of the total decline. The results indicated that air pollution control policies targeting SO₂, NO_x and particulate matter reductions had significant co-benefits on atmospheric mercury.

A Holistic Perspective Is Needed To Ensure Success of Minamata Convention on Mercury

Updated atmospheric mercury emissions from iron and steel production in China during 2000&ndash;2015

Iron and steel production (ISP) is one of the significant atmospheric Hg emission sources in China. Atmospheric mercury (Hg) emissions from ISP during 2000&amp;ndash;2015 were estimated by using a technology-based emission factor method. To support the application of this method, databases of Hg concentrations in raw materials, technology development trends, and Hg removal efficiencies of air pollution control devices (APCDs) were constructed through national sampling and literature review. Hg input to ISP increased from 21.6&amp;thinsp;t in 2000 to 94.5&amp;thinsp;t in 2015. In the various types of raw materials, coking coal and iron concentrates contributed 41&amp;thinsp;%&amp;ndash;55&amp;thinsp;% and 22&amp;thinsp;%&amp;ndash;30&amp;thinsp;% of the total Hg input. Atmospheric Hg emissions from ISP increased from 11.5&amp;thinsp;t in 2000 to 32.7&amp;thinsp;t in 2015 with the peak of 35.6&amp;thinsp;t in 2013. During the study period, although sinter/pellet plant and blast furnace were the largest two emission processes, emissions from roasting plant and coke oven accounted for 22&amp;thinsp;%&amp;ndash;34&amp;thinsp;% of ISP’s emissions, which indicated that attention should also be paid on the emissions from these processes when estimating ISP’s emissions. Overall Hg speciation shifted from 50/44/6 (gaseous elemental Hg (Hg⁰)/gaseous oxidized Hg (Hg^II)/particulate-bound Hg (Hg_p)) in 2000 to 40/59/1 in 2015, which indicated higher proportion of Hg deposition around the emission points. In the coming years, emissions from ISP are expected to decrease due to the projection of decreasing steel productions, increasing energy consumption efficiency, and improvement of APCDs. With the coming of high-yield-period of steel scrap production, the increasing application proportion of short process steel making method will not only reduce Hg emissions, but also increase the emission proportion of Hg⁰.

Updated atmospheric speciated mercury emissions from iron and steel production in China during 2000–2015

Iron and steel production (ISP) is one of the significant atmospheric Hg emission sources in China. Atmospheric mercury (Hg) emissions from ISP during 2000–2015 were estimated by using a technology-based emission factor method. To support the application of this method, databases of Hg concentrations in raw materials, technology development trends, and Hg removal efficiencies of air pollution control devices (APCDs) were constructed through national sampling and literature review. Hg input to ISP increased from 21.6 t in 2000 to 94.5 t in 2015. In the various types of raw materials, coking coal and iron concentrates contributed 35–46 and 25–32 % of the total Hg input. Atmospheric Hg emissions from ISP increased from 11.5 t in 2000 to 32.7 t in 2015 with a peak of 35.6 t in 2013. Pollution control promoted the increase in average Hg removal efficiency, from 47 % in 2000 to 65 % in 2015. During the study period, sinter/pellet plants and blast furnaces were the largest two emission processes. However, emissions from roasting plants and coke ovens cannot be ignored, which accounted for 22–34 % of ISP's emissions. Overall, Hg speciation shifted from 50/44/6 (gaseous elemental Hg (Hg⁰)/gaseous oxidized Hg (Hg^II)/particulate-bound Hg (Hg_p)) in 2000 to 40/59/1 in 2015, which indicated a higher proportion of Hg deposition around the emission points. Future emissions of ISP were expected to decrease based on the comprehensive consideration crude-steel production, steel scrap utilization, energy saving, and pollution control measures.

Minamata Convention on Mercury: Chinese progress and perspectives

Role of inherent active constituents on mercury adsorption capacity of chars from four solid wastes

Mechanism identification of temperature influence on mercury adsorption capacity of different halides modified bio-chars

Mercury flows in large-scale gold production and implications for Hg pollution control

The influence of flue gas components and activated carbon injection on mercury capture of municipal solid waste incineration in China

Mercury sorption study of halides modified bio-chars derived from cotton straw

Mercury emission and speciation from industrial gold production using roasting process

Mercury transformation and speciation in flue gases from anthropogenic emission sources: a critical review

Mercury transformation mechanisms and speciation profiles are reviewed for mercury formed in and released from flue gases of coal-fired boilers, non-ferrous metal smelters, cement plants, iron and steel plants, waste incinerators, biomass burning and so on. Mercury in coal, ores, and other raw materials is released to flue gases in the form of Hg⁰ during combustion or smelting in boilers, kilns or furnaces. Decreasing temperature from over 800 °C to below 300 °C in flue gases leaving boilers, kilns or furnaces promotes homogeneous and heterogeneous oxidation of Hg⁰ to gaseous divalent mercury (Hg²⁺), with a portion of Hg²⁺ adsorbed onto fly ash to form particulate-bound mercury (Hg_p). Halogen is the primary oxidizer for Hg⁰ in flue gases, and active components (e.g., TiO₂, Fe₂O₃, etc.) on fly ash promote heterogeneous oxidation and adsorption processes. In addition to mercury removal, mercury transformation also occurs when passing through air pollution control devices (APCDs), affecting the mercury speciation in flue gases. In coal-fired power plants, selective catalytic reduction (SCR) system promotes mercury oxidation by 34–85 %, electrostatic precipitator (ESP) and fabric filter (FF) remove over 99 % of Hg_p, and wet flue gas desulfurization system (WFGD) captures 60–95 % of Hg²⁺. In non-ferrous metal smelters, most Hg⁰ is converted to Hg²⁺ and removed in acid plants (APs). For cement clinker production, mercury cycling and operational conditions promote heterogeneous mercury oxidation and adsorption. The mercury speciation profiles in flue gases emitted to the atmosphere are determined by transformation mechanisms and mercury removal efficiencies by various APCDs. For all the sectors reviewed in this study, Hg_p accounts for less than 5 % in flue gases. In China, mercury emission has a higher Hg⁰ fraction (66–82 % of total mercury) in flue gases from coal combustion, in contrast to a greater Hg²⁺ fraction (29–90 %) from non-ferrous metal smelting, cement and iron and/or steel production. The higher Hg²⁺ fractions shown here than previous estimates may imply stronger local environmental impacts than previously thought, caused by mercury emissions in East Asia. Future research should focus on determining mercury speciation in flue gases from iron and steel plants, waste incineration and biomass burning, and on elucidating the mechanisms of mercury oxidation and adsorption in flue gases.

Mercury mass flow in iron and steel production process and its implications for mercury emission control

Flow Analysis of the Mercury Associated with Nonferrous Ore Concentrates: Implications on Mercury Emissions and Recovery in China

Material Flow for the Intentional Use of Mercury in China

Mercury Flows in China and Global Drivers

Characteristics of mercury cycling in the cement production process

Temporal Trend and Spatial Distribution of Speciated Atmospheric Mercury Emissions in China During 1978–2014

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

Updated Emission Inventories for Speciated Atmospheric Mercury from Anthropogenic Sources in China

Mercury enrichment and its effects on atmospheric emissions in cement plants of China

A review of atmospheric mercury emissions, pollution and control in China

Were mercury emission factors for Chinese non-ferrous metal smelters overestimated? Evidence from onsite measurements in six smelters