Trend and characteristics of atmospheric emissions of Hg, As, and Se from coal combustion in China, 1980–2007

摘要

Emissions of hazardous trace elements in China are of great concern because of their negative impacts on local air quality as well as on regional environmental health and ecosystem risks. In this paper, the atmospheric emissions of mercury (Hg), arsenic (As), and selenium (Se) from coal combustion in China for the period 1980–2007 are estimated on the basis of coal consumption data and emission factors, which are specified by different categories of combustion facilities, coal types, and the equipped air pollution control devices configuration (Dust collectors, FGD, etc.). Specifically, multi-year emission inventories of Hg, As, and Se from 30 provinces and 4 economic sectors (thermal power, industry, residential use, and others) are evaluated and analyzed in detail. Furthermore, the gridded distribution of provincial-based Hg, As, and Se emissions in 2005 at a resolution of 1° 1° is also plotted. It shows that the calculated national total atmospheric emissions of Hg, As, and Se from coal combustion have rapidly increased from 73.59 t, 635.57 t, and 639.69 t in 1980 to 305.95 t, 2205.50 t, and 2352.97 t in 2007, at an annually averaged growth rate of 5.4%, 4.7%, and 4.9%, respectively. The industrial sector is the largest source for Hg, As, and Se, accounting for about 50.8%, 61.2%, and 56.2% of the national totals, respectively. The share of power plants is 43.3% for mercury, 24.9% for arsenic, and 33.4% for selenium, respectively. Also, it shows remarkably different regional contribution characteristics of these 3 types of trace elements, the top 5 provinces with the heaviest mercury emissions in 2007 are Shandong (34.40 t), Henan (33.63 t), Shanxi (21.14 t), Guizhou (19.48 t), and Hebei (19.35 t); the top 5 provinces with the heaviest arsenic emissions in 2007 are Shandong (219.24 t), Hunan (213.20 t), Jilin (141.21 t), Hebei (138.54 t), and Inner Mongolia (127.49 t); while the top 5 provinces with the heaviest selenium emissions in 2007 are Shandong (289.11 t), Henan (241.45 t), Jiangsu (175.44 t), Anhui (168.89 t), and Hubei (163.96 t). Between 2000 and 2007, provinces always rank at the top five largest Hg, As, and Se emission sources are: Shandong, Hebei, Shanxi, Henan, and Jiangsu, most of which are located in the east and are traditional industry-based or economically energy intensive areas in China. Notably, Hg, As, and Se emissions from coal combustion in China begin to grow at a more moderate pace since 2005. Emissions from coal-fired power plants sector began to decrease though the coal use had been increasing steadily, which can be mainly attributed to the increasing use of wet flue gas desulfurization (WFGD) in power plants, thus the further research and control orientations of importance for these hazardous trace elements should be the industrial sector.