Presentation on theme: "Mercury in coal from the People’s Republic of China H.E. Belkin, S.J. Tewalt U.S. Geological Survey, Reston, VA USA R.B.Finkelman (USGS retired) University."— Presentation transcript:
Mercury in coal from the People’s Republic of China H.E. Belkin, S.J. Tewalt U.S. Geological Survey, Reston, VA USA R.B.Finkelman (USGS retired) University of Texas at Dallas, Richardson, Texas USA B. Zheng, D.Wu, S. Li, J. Zhu, B. Wang State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, P.R. China
Mercury in Chinese Coal - Outline Why study Hg in Chinese coal? Hg in Chinese coal as part of the USGS WoCQI Program. Strategy of sample collection - is our Hg ‘number’ representative of the average coal ‘in-ground’ in China? Hg analysis and data. Future work.
Facts about mercury: Highly toxic to the nervous system Persistent in the environment Bioaccumulates (higher concentrations in tissues of aquatic plants and animals than in water) Biomagnifies (higher concentrations at increasingly higher levels in the food chain) Numerous chemical forms in air, water, sediment, and biota Responsible for nearly 80 percent of U.S. fish-consumption advisories
In the last 60 years, a dramatic awareness of the presence and toxicity of methylmercury. Goodman’s and Gilman’s: The Pharmacological Basis of Therapeutics
Coal-fired power plants - a major world-wide Hg source
Where does the mercury come from? 2005 From Cain 2005
Worldwide Distribution of Mercury Emissions Recent estimates, which are highly uncertain, of annual total global mercury emissions from all sources, natural and anthropogenic, are about 4,400 to 7,500 metric tons emitted per year. (EPA, 2004)
Hg o Where does the Hg flux falling on the USA come from? Pacyna et al. 1995
China as a source of Hg emissions Streets et al Estimated that in 1999 China emitted 536 t Hg (all sources) and of that 38 % (204 t) was from coal combustion (all types)
China coal production: 2005 estimated 2.05 billion tons “The China Daily” People’s Republic of China Coal production and use in China will Continue to increase in the future.
Mercury Emission From China Exceed USA By J. Winston Porter (As published in The Virginian-Pilot, 8/10/98) Who is the chief culprit responsible for the elevated levels of mercury found in freshwater fish? Environmentalist dogma notwithstanding, it is China that loads the atmosphere with the largest share of the airborne mercury that is transported and deposited around the world; the United States is just a tiny player in the global pool. Mercury Emission - a Global Problem
Why study Hg in Chinese coal? China is the largest producer and consumer of coal in the world and -- Coal combustion in China will continue to emit an increasing mass of Hg into the environment -- and this Hg may fall on the United States.
WoCQI Information on global coal quality for national and international policymakers Cooperative project with about 50 countries (of 70 world-wide coal-producing countries) Unique collection of coal quality data
Hg data as part of the WoCQI program of coal analysis Proximate Ultimate Major and minor elements Se, Hg Engineering parameters WoCQI Program and Hg in Chinese coals Develop an accurate, internally consistent coal quality database to aid in research and modeling of the occurrence, combustion, and nature of Hg in Chinese coals.
Strategy of Sample Collection
Output of Raw Coal by Type of Coal Mines 1998 From China Coal Industry Yearbook 1999 National total State-controlled coal mines Local Coal Mines Of which: Provincial mines Prefectural mines County mines Collective and individual mines Output 10 3 tPercentage A National Policy to increase number of large-state controlled mines and reduce small local mines % 39%
From China Coal Industry Yearbook 1999 National Survey A partial inventory Number of mines The number of small mines is being reduced but is hard to control as the economy booms and coal increases in price.
Hg data Perkin-Elmer 3030B USGS Denver, CO laboratory cold vapor atomic absorption spectrometry Precision = ± 10% Reporting detection limit = 0.02 ppm Collected 327 total samples 305 channel or run-of-mine samples from ~200 large mines in 25 Provinces, municipalities, and autonomous regions. Coal sampling strategy
Censored data <0.02 ppm A small percentage = ~9% Replacement factor = 0.55 [ = ppm] Sanford, R.F., Pierson, C.T., and Crovelli, R.A., An objective replacement method for censored geochemical data., Mathematical Geology, vol. 25,
USGS Hg data by Province and Rank25 Provinces Sampled 327 total samples
Average Hg content (ppm) of Chinese coal USGS study (September 2004) 305 coals (all ranks) Basis: as-determined, whole coal mean = 0.15 (stdv.= 0.14) Min = <0.02 Max = 0.69 Basis: dry, whole coal mean = 0.16 (stdv.= 0.14) geometric mean = 0.13 USA Hg in coal-dry basis, mean = 0.17 ppm (COALQUAL database) Wang et al. n = 234 mean = 0.22 ppm Huang and Yang n = 1466 mean = 0.15 ppm Zhang et al. n = 990 mean = 0.16 ppm
General examination of the Hg data
Mode of Occurrence of Hg in Coals Why are we interested? (1) Understand origin of Hg in coals (2) Model pre-and post-combustion procedures to reduce Hg emissions (3) Predict Hg contents in seams during mining
All mercury data - all coals
All data - all coals
All data All coals
Total Fe 2+ (wt.%) Pyrite proxy Hg (ppm, dry basis) Longtan Formation coals Separating data into Formations suggests that Hg may increase with poor quality coals - And that cleaning may reduce the Hg content. Caveat: Formations may be Chronostratigraphic not Lithostratigraphic Detailed analysis of mode of Hg occurrence
Results from a comparison of Cleaned versus Uncleaned coal samples from the Longtan Formation. What can it tell us about the mode of occurrence of Hg in these coals?
CLEANING REDUCES ASH IN MOST SAMPLES
CLEANING REDUCES SULFUR IN MOST SAMPLES
CLEANING REDUCES MERCURY IN MOST SAMPLES
Summary of mode of Hg occurrence Hg in coals from the People’s Republic of China has a varied mode of occurrence - Both organic and inorganic affinities Pyrite Organically-bound Mercury phases Silicates and other sulfides Coal cleaning may reduce Hg from some coal sources.
Future USGS - China Collaboration on Problems Relating to Coal Geochemistry Detailed interpretation of the Hg data with respect to other parameters, for example, production, proximate and ultimate analysis, etc. More sampling in selected areas. Research in areas where Hg-rich coal may pose a human health problem.
Hg from mineralized coals from Guizhou Province
Summary Mercury in Chinese Coal Strategy of sample collection - is our Hg number representative of the average in-ground coal in China? Probably representative of coal used for electric power production and major industries but may underestimate Hg content in average coal burnt in China. Poorer quality coal used in domestic combustion.
Summary Mercury in Chinese Coal Strategy of sample collection - is our Hg number representative of the average in-ground coal in China? Probably representative of coal used for electric power production and major industries but may underestimate Hg content in average coal burnt in China. Poorer qualtiy coal used in domestic combustion. Hg analysis and data. = Hg content of coals is 0.16 ppm on a dry, whole-coal basis. Somewhat less or the same as the World average
Summary Mercury in Chinese Coal Strategy of sample collection - is our Hg number representative of the average in-ground coal in China? Probably representative of coal used for electric power production and major industries but may underestimate Hg content in average coal burnt in China. Hg analysis and data. = Hg content of coals is 0.16 ppm on a dry, whole-coal basis. Somewhat less or the same as the World average The challenge for the Chinese coal industry is to increase and develop effective pre- and post-combustion procedures to reduce Hg emission.