Impact of coal gangue on the level of main trace elements in the shallow groundwater of a mine recla

Mining Science and Technology( China)21(2011)715-719Contents lists available at SciVerse Science DirectMining Science and Technology( ChinaELSEVIERjournalhomepagewww.elseviercom/locate/mstcImpact of coal gangue on the level of main trace elements in the shallowgroundwater of a mine reclamation areaLi Wei, Chen Longqian Zhou Tianjian, Tang Qibao, Zhang TingKey Laboratory of Resources and Environment Information Engineering China University of Mining S Technology, Xuzhou 221116, ChinaSchool of Environment and Spatal Informatics, China University of Mining 6 Technology, Xuzhou 221116, ChinARTICLE INF OA BSTRACTCoal gangue is the most used filling material during reclamation of areas suffering subsidence from m13 Febru011in revised2 March 2011ng. Main trace element levels(F, As, Hg and pb) in shallow groundwater in the reclamation area may be27 March 2011affected by leaching from the gangue. this can has an impact on the application of the water for agricul-online 2 November 2011tural irrigation or use as drinking water. Therefore, it is of great significance to understand the effect coalgangue has on the shallow groundwater of a reclaimed area. we studied the effect of coal gangue on nluo-rine, arsenic, mercury, and lead levels in the shallow groundwater of a reclamation area by testing thewater and the coal gangue. One well near the reclamation area was used as a control well and elementMain trace elementslevels in water from this well and from the soil next to the well were also measured the results shotwaterthat the levels of these elements are increasing in the reclamation area over time the increase in fluorineReclamation areaarsenic, mercury, and lead in monitor wells varies from 7. 42% to 8.26% from 7. 13% to 7.90%, from 4.85% toNemerow index6.48%, and from 4.69% to 6.42%, respectively. fluorine and arsenic levels are lower in monitor wells thanin the control water. The other elements are found in greater concentration than in the control. TheNemerow index also indicates that the shallow groundwater in the reclamation area I is moderatelyaffected by the back-filling coal gangue, while the shallow groundwater in the reclamation area ll andIll are slightly affected by the back-filling coal gangue. this shallow groundwater could be used for agricultural irrigation or for drinking.o 2011 Published by Elsevier B V on behalf of China University of Mining Technology1 Introductionappropriate for subsidence land [12-16]. Others are absorbed inthe study of mining water pollution from subsidence pools or theLand reclamation after mine subsidence began during the late treatment of heavy metals found in mining waste [17, 18 Carbon1970s in China and has been practiced more extensively since pools and sequestration rates in reclaimed mine soils have beenhe promulgation of the Regulations of Land Relation in 1988[1]. examined recently by Lal et al. [19-21lGreat progress in land reclamation has recently been made in Chi-However few scholars considered the impact of coal gangue onna. It has been reported that the land reclamation rate is rising rap- the shallow groundwater of the reclamation area. Aquifers are andly from less than 1% initially to 12% till 2005 [21important source of irrigation and drinking water in China, andSince large scale land reclamations have been carried out, elsewhere and these sources are vulnerable to contamination bynumerous studies have been conducted to improve the under- trace elements in the reclamation area. Hence, the safety of agristanding of the results of these efforts. the majority of these stud- cultural irrigation and drinking water depend on the concentraies focus on soil quality of the reclaimed coal mining subsidence tions these trace elements havearea. points of interest include: changes in the organic matter.The Zhangji mine is one of the most seriously affected innitrogen, phosphorus, and potassium content of soils after recla- Huainan city. Considerable arable land has been subject to subsi-mation: the spatio-temporal effects of physical and chemical prop- dence since the beginning of coal exploitation in 1998. Reclama-erties on reclamation soil; heavy metal pollution in the reclaimed tion of this subsided land for agriculture purposes was carriedsoil from the use of filling materials; and the activity of microor- out at the Zhangji Mine in 2004, possibly leading to some traceganisms in the reclaimed soil [3-11]. Some workers focus on the element contamination of the shallow groundwater from coal gan-damage to the land from coal exploitation and restoration methods gue back-filling in the reclaimed areaThe most commonly used method of obtaining the impact ofCorresponding author Tel +86 51683885869coal gangue on shallow groundwater is to compare theelement contents of中国煤化工ndnearby.1674-5264/s-see front matter e 2011 Published by Elsevier B V on behalf of China University of Mining Tecdoi:10.016/mstc201103CNMHGwLiet aL/ Mining Science and Technology( China)21(2011)715-719unaffected, well. the trace element content in the coal gangue andMonitor wellsoil next to the monitor well are also tested therefore the objectives of this study are to identify and document the trends in traceelement levels in the shallow groundwater of the reclamation area.The impact of coal gangue on the trace element concentration willbe deduced from the quality of the groundwater and the suitabilityof the water for use as agricultural irrigation and drinking water辅Finwill be determined-2=-=-ELE::::: :2. Materials and methods2.1. A description of the study areaThe Zhangji Mine is located at Huainan city in Anhui provinceThe reclamation of subsided land was begun in June 2004 andcompleted in June 2006. The reclaimed area consists of Part L, PartIl, and Part Ill. Monitor wells were drilled in the center of each part,经经了+经经到iigsee Fig. 1. An existing independent well near the reclaimed areawas used as a control. the vertical section of a monitor well isgangueshown in Fig. 2. The first layer of the reclaimed area is soil back-filland coal gangue is the second layer the water table is about 2-3 mbelow the ground surface at the monitor wells. the total reclaimedarea is 46 ha. The annual temperature in the Zhangji mine is15.3C and the annual precipitation is 954.8 mm. the annual evap-oration is 1613. 2 mm. About 50% of the precipitation occurs duringJune, July and august.Shallow groundwater2. 2. Sample collection and analysisFig. 2 A vertical cross-section structure of a monitor wellA total of 19 water samples, consisting of 18 monitor well sam- passed through a 0.15 mm nylon sieve. The solid samples wereples and one independent well sample, were collected from the then digested in a HCIOa-HNOj-HF mixturewells. Samples were taken semiannually from December 2006The fluorine content was determined by ion chromatographyuntil June 2009. The water samples were returned to the laboraAn inductively coupled plasma atomic mass spectrometer(ICPory in plastic bottles and examined immediately.MS)was used to analyze for arsenic, mercury and lead levels inThe back-fill coal gangue next to the three monitor wells and all samplesthe soil near the independent well were collected in Decembera water quality index was adopted to assess the contamination2006. The three coal gangue samples and the soil sample were level as a way of evaluating the effect of trace elements from thesealed in plastic bags and transported to the laboratory. They were coal gangue. The water quality index was calculated using theair dried at room temperature, ground with a porcelain mortar, and Nemerow index[22:P1=C1/S1(1)PI2+G∑h1p)2where Ci is the level of element i: S; the background value in theindependent well of element i: Pi contamination index of elementMonitor wellⅢPartⅢi: n the element number; pi the average contamination index of ele-ment i: and pi the nemerow index.Similar terms are used to describe the integrated effect index,i.e.: Pl<1 is no effect; 1well ll >well lll. This has an accu-mulation effect on the fluorine content in the shallow groundwater. The indication is that the fluorine may come from coalgangue. Note that the fluorine level in all the monitor wells is lower than that(981. 1 ug/L)in the groundwater from the control well.In addition, fluorine levels in the coal gangue fall in the sameorder as for the shallow groundwater, showing that the fluorine0.515in the water is related to the coal gangue. The quality standardfor groundwater considers this shallow groundwater not to beTime after reclaimation (year)ontaminated by the coal gangue.Fig. 4. Arsenic levels in shalow groundwater from December 2006 until June 2009.3.3. Arsenic content in shallow groundwaterFig- 4 shows the arsenic levels in the shallow groundwater of 34. Mercury content in shallow groundwaterthe reclaimed land. Compared to water from the control wellMercury measurements on the water samples showed an in-(5.81 Hg/L Table 2)these concentrations are all at a low level that crease in the mercury level in the ground waters of the reclaimdoes not exceed the Class I quality standard for groundwater(5 Hg/ area, see Fig. 5. The concentration of mercury in monitor well ILy). From December 2006 to June 2009 arsenic levels increased raised by 6.48% over the sampling period Increases of 4.85% andslightly. Arsenic in monitor well I increased as much as 7.54% in 6.45% were seen in wells ll and Ill, respectively These levels aremonitor well ll 7.90%, and in monitor well lll 7. 13%. The increase higher compared to the control water(0.090 ug/L Table 2).in arsenic level falls in the order well ll >well I wellA comparison of mercury levels in the soil and in coal gangue.Furthermore, the arsenic content in the undisturbed soil is high- (Table 1)indicates that coal gangue contains more than the controler than that in the coal gangue (Table 1). This may contribute to the soil. This illustrates that coal gangue is effecting the mercury levellow arsenic content in the shallow groundwater.in the shallow groundwater. Base on the quality standard forthe shallow groundwater in the reclaimed area isnotnated but there is some accumulation of mercury inElement concentrations in the water from the control well and the quality standard thegroundwater.for groundwater(GBT14848-93)(ug/L).F3.5. Lead content in shallow groundwaterwater5.81≤00The lead content of the shallow groundwater in the reclaimedClass ll criterion≤0.5rea is shown in Fig. 6. Lead levels at the three wells are goingote: Class i criteria were used to assess the low background value of undisturbeup slightly over time中国煤化工 s seen at welnatural groundwater: Class ll criteria were used to assess the background value of over 3 years. Increasundisturbed, natural groundwaterlI and Ill over the sarCNMH Gnitor wells are718Monitor well I3.6. Assessing the impact on shallow groundwater in the reclamation0.24Monitor well llarea from coal gangueMonitor well IImThe Nemerow index for the three monitor wells is presented inTable 3. The Pi values for fluorine and arsenic range from 0.780 to0220.801 and from 0.802 to 0.835, respectively. This indicates that thewater is not contaminated by these elements. However, high val-ues of Pi are found for the heavy metals. these vary from 2.200to 2.556 for mercury, from 1.337 to 1. 529 for lead. These resultssuggest the more pollution is from mercury, and the slightly pollu-tion is from lead0.19The Nemerow index values are 2.070 for monitor well 1, 1.959for well Il, and 1801 for well lll. this means that the shallow0.18groundwater in the reclamation area I is moderately affected bythe back-filling coal gangue, while the shallow groundwater inTime after reclamation(year)the reclamation area ll and Ill are slightly affected by the backfilling coal gangue.Ftg 5. Mercury levels in the shallow groundwater from December 2006 until June20094. ConclusionsLevels of main trace elements in the shallow groundwater of theZhangji reclamation area were studied the results reveal that thecoal gangue back-filling in the reclaimed area affects certain traceelement concentrations. The main conclusions are(1)Fluorine, arsenic, mercury, and lead levels in the shallowoundwater increase to a different extent. mercury and leadMonitlevels exceed the background values seen in water from anMonitor well IIindependent control well. The contents of fluorine andMonitor well IIIarsenic in the shallow groundwater are lower than seenhe control well(2)The P values for fluorine and arsenic range from 0.780to0801and from 0.802 to 0.835, respectively. this means that thewater is not contaminated by these elements. But the valuesof P: vary from 2.200 to 2.556 for mercury, and from 1.337 to0.51.529 for lead. These results suggest much more pollutionTime after reclamation (year)comes from mercury, and slightly pollution comes from lead(3)The Nemerow index values are 2.070 for monitor wellFlg. G Lead levels in the shallow groundwater from December 2006 until June.959 for well Il, and 1. 801 for well Ill. this means that theshallow groundwater in the reclaimed area i is moderatelyaffected by the coal gangue, while the shallow groundwaterin the reclamation area ll and Ill are slightly affected by theback-filling coal gangue(4)The quality standard for groundwater(GBT14848-93)classiNemerow index of the three monitor wells.fies the groundwater as"not contaminated"and it could beSiteof use for agricultural imigation or drinking 3 years afterAs(5)The discharge of these trace elements from the coalmonitor well I08012.06may cause future accumulation of them in theMonitor well ll0823Monitor wellⅢ080222001.337groundwater. So it is still necessary to monitor theof coal gangue on the trace element levels to maintain thesafe use of the water for agriculture and drinking.higher than at the control well (6.18 ug/L Table 2). Still, these levels are lower than the Class ll criteria for quality groundwater AcknowledgmentsstandardsThere is a little enrichment in the level compared to the controlThe project was funded by the Priority Academic prograyater, but no contamination defined by the quality standard for Development of Jiangsu Higher Education Institutions(PAPD).groundwater. The lead content of the coal gangue is somewhat We are grateful to Jiangsu Key Laboratory of Resources and Envi-higher than that of the control soil and higher levels in the coal ronment Information Engineering( China University of mininggangue are connected with increased levels in the shallow ground- Technology). We wish to express our most sincere appreciationwater. These may contribute to the higher lead levels in the mon- to Miss Shen jianpingitor wells. In other words, the increased lead content in the shallow drawing figures.And中国煤化工 d environmentgroundwater is probably due to discharge of lead from the coal Management Branchgangueso much. which offerH. Group) C, LtLi et aL/ Mining Science and Technology (China)21(2011)715-719719References[12] Li YF, Liu YH, Du ZP, Chen J. Effect of coal resources development ato cultivated landmining areas, MiningUniv Mining Technol 2004: 33(2): 213-8[2] Cao X. Regulating mine land reclamation in developing countries, Case China[14] Bi YL Wu WY, Liu YP. Application of arbuscular mycorrhizas in landLand Use Policy 2007: 24(2): 472-8claymation of coal spoil heaps. Acta Ecol Sin 2007: 27(9):3738-43[3]Li SZ, Gao R]. Variability of reclaimed soil properties in subsided land[151 Juwarkar AA, Jambhulkar HP. Phytoremediation of coal mine spoil dumg Tech Univ2006:25(5)792-4.[4] Yu JB. Wang JD, Liu JS. 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