Abstract
Abstract. A better understanding of the discrepancies in multi-scale inventories could give an insight into their approaches and limitations as well as provide indications for further improvements; international, national, and plant-by-plant data are primarily obtained to compile those inventories. In this study we develop a high-resolution inventory of Hg emissions at 0.05° × 0.05° for Jiangsu, China, using a bottom-up approach and then compare the results with available global/national inventories. With detailed information on individual sources and the updated emission factors from field measurements applied, the annual Hg emissions of anthropogenic origin in Jiangsu in 2010 are estimated at 39 105 kg, of which 51, 47, and 2 % were Hg0, Hg2+, and Hgp, respectively. This provincial inventory is thoroughly compared to three downscaled national inventories (NJU, THU, and BNU) and two global ones (AMAP/UNEP and EDGARv4.tox2). Attributed to varied methods and data sources, clear information gaps exist in multi-scale inventories, leading to differences in the emission levels, speciation, and spatial distributions of atmospheric Hg. The total emissions in the provincial inventory are 28, 7, 19, 22, and 70 % larger than NJU, THU, BNU, AMAP/UNEP, and EDGARv4.tox2, respectively. For major sectors, including power generation, cement, iron and steel, and other coal combustion, the Hg contents (HgC) in coals/raw materials, abatement rates of air pollution control devices (APCDs) and activity levels are identified as the crucial parameters responsible for the differences in estimated emissions between inventories. Regarding speciated emissions, a larger fraction of Hg2+ is found in the provincial inventory than national and global inventories, resulting mainly from the results by the most recent domestic studies in which enhanced Hg2+ were measured for cement and iron and steel plants. Inconsistent information on large power and industrial plants is the main source of differences in spatial distribution of emissions between the provincial and other inventories, particularly in southern and northwestern Jiangsu, where intensive coal combustion and industry are located. Quantified with Monte Carlo simulation, uncertainties in the provincial inventory are smaller than those of the NJU national inventory, resulting mainly from the more accurate activity data of individual plants and the reduced uncertainties in HgC in coals/raw materials.
Highlights
Mercury (Hg), known as a global pollutant, has received increasing attention for its toxicity and long-range transport
Identified as the most significant release into the environment (Pirrone and Mason, 2009; AMAP/UNEP, 2013), atmospheric Hg is analytically defined as gaseous elemental Hg (GEM, Hg0), which has the longest lifetime and transport distance, and reactive gaseous mercury (RGM, Hg2+) and particle-bound mercury (PBM, Hgp), which are more affected by local sources
Based on the chemistry transport modeling using GEOS-Chem (Wang et al, 2014), or correlation slopes with certain tracers (CO, CO2, and CH4) from ground observation (Fu et al, 2015), underestimation was suggested for the regional Hg emissions of anthropogenic origin in China
Summary
Mercury (Hg), known as a global pollutant, has received increasing attention for its toxicity and long-range transport. Existing global and national inventories could hardly provide satisfying estimates in speciated Hg emissions or well capture the spatial distribution of emissions at regional/local scales, attributed mainly to relatively weak investigation of individual sources. When they are used in a chemistry transport model (CTM), downscaled inventories at global/national scales would possibly bias the simulation at smaller scales. The results provide an insight into the effects of varied approaches and data on development of the Hg emission inventory and indicate the limitations of current studies and the orientations for further improvement on emission estimation at regional/local scales
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