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)

Hgo

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. 2005

Estimated that in 1999China 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 willContinue to increase in the future.

Mercury Emission From China Exceed USABy J. Winston Porter(As published in The Virginian-Pilot, 8/10/98)

Who is the chief culprit responsible for the elevated levels of mercuryfound in freshwater fish? Environmentalist dogma notwithstanding,it is China that loads the atmosphere with the largest share ofthe 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 theUnited 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 analysisProximateUltimateMajor and minor elements

Se, HgEngineering parameters

WoCQI Program and Hg in Chinese coalsDevelop an accurate, internally consistent coal quality databaseto 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 1232510State-controlled coal mines 503490 40.9Local Coal Mines 729020 59.1

Of which: Provincial mines 48080 3.9 Prefectural mines 62920 5.1 County mines 101850 8.3 Collective and individual mines 553110 44.9

Output 103t Percentage

A National Policy to increase number of large-statecontrolled mines and reduce small local mines.

2004

196000061%39%

From China Coal Industry Yearbook 1999

National SurveyA partial inventory

37713 394 252 387 963

35803

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 dataPerkin-Elmer 3030B USGS Denver, CO laboratorycold vapor atomic absorption spectrometryPrecision = ± 10%Reporting detection limit = 0.02 ppm

Collected 327 total samples305 channel or run-of-mine samples

from ~200 large mines in 25 Provinces,municipalities, and autonomous regions.

Coal sampling strategy

Censored data

<0.02 ppmA small percentage = ~9%Replacement factor = 0.55 [ = 0.011 ppm]

Sanford, R.F., Pierson, C.T., and Crovelli, R.A., 1993. An objective replacement methodfor censored geochemical data., Mathematical Geology, vol. 25, 59-80.

USGS Hg data by Province and Ranksub-bituminous- cleaned coals

Province anthracite bituminous lignite any rank totalAnhui 1 10 11Beijing 1 1Fujian 3 3Gansu 5 5Guangdong 2 2Guangxi 1 2 2 5Guizhou 6 17 6 23Heibei 1 14 15Heilongjiang 10 10Henan 6 21 27Hubei 2 1 3Hunan 6 4 10Jiangsu 6 6Jiangxi 2 5 7Jilin 4 1 5Liaoning 8 1 9Neimenggu (Inner Mong.) 8 8 16Ningxia 1 3 4Qinghai 1 1Shaanxi 11 11Shangdong 16 3 19Shanxi 15 73 88Sichuan 5 23 1 12 29Xinjiang 6 6Yunnan 10 2 4 12

327

305 coal samples (not-cleaned)

25 Provinces Sampled

327 total samples

data in ppmProvince n = Minimum Maximum Mean std dev censored dataBeijing 1 0.54Qinghai 1 0.04Guangdong 2 <0.02 0.09 0.05 0.05 1Hubei 3 0.12 0.24 0.16 0.07Fujian 3 <0.02 0.14 0.07 0.07 1Ningxia 4 <0.02 0.49 0.20 0.22 1Jilin 5 0.05 0.07 0.07 0.01Guangxi 5 0.09 0.65 0.33 0.27Gansu 5 0.04 0.06 0.05 0.01Jiangsu 6 0.11 0.60 0.34 0.21Xinjiang 6 <0.02 0.04 0.02 0.01 4Jiangxi 7 0.09 0.52 0.27 0.16Yunnan 7 0.03 0.42 0.14 0.14Liaoning 9 0.04 0.66 0.18 0.19Hunan 10 <0.02 0.32 0.14 0.10 1Heilongjiang 10 0.03 0.12 0.06 0.03Anhui 11 0.06 0.66 0.19 0.18Shaanxi 11 <0.02 0.55 0.13 0.18 4Hebei 15 <0.02 0.40 0.14 0.12 1Guizhou 16 <0.02 0.41 0.20 0.12 1Neimenggu 16 <0.02 0.33 0.15 0.10 1Sichuan 18 <0.02 0.27 0.11 0.08 3Shandong 19 0.03 0.34 0.13 0.09Henan 27 0.02 0.48 0.21 0.12Shanxi 88 <0.02 0.69 0.15 0.15 11

Total number 305 <0.02 0.69 0.15

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 ppmHuang and Yang n = 1466 mean = 0.15 ppmZhang 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 dataAll coals

0

0.1

0.2

0.3

0.4

0.5

0 0.5 1 1.5 2 2.5 3 3.5 4

Hg

Fe3+Total Fe2+ (wt.%)Pyrite proxy

Hg

(ppm

, dry

bas

is)

Longtan Formation coals

Separating data intoFormations suggeststhat Hg may increasewith poor quality coals -

And that cleaning mayreduce the Hg content.

Caveat:Formations may beChronostratigraphicnot Lithostratigraphic

Detailed analysis of mode of Hg occurrence

Results from a comparison ofCleaned versus Uncleaned coal

samples from the Longtan Formation.

What can it tell us about themode of occurrenceof 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 thePeople’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 ProblemsRelating 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.

Gold ore-deposits

Metal-rich coals

Hg from mineralized coals from Guizhou Province

Coal affected by Carlin-type deposit ore-forming solutions. Mineralized coal enriched in As, Tl, U, Hg, Sb, Au Pathways of mineralizing solutions follow structurally controlled fractures, joints, and faults. Mode of occurrence of Hg: cinnabar, sulfides, and perhaps an organic-Hg compound.

Hg in mineralized coal inGuizhou Province.

Further Study on Guizhou Province Coals

SummaryMercury 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.

SummaryMercury 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

SummaryMercury 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.

Thank you for your attention!