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A preliminary study of coal mining drainage and environmental health in the SantaCatarina region, BrazilLuis F. O. Silva Marcus Wollenschlager Marcos L. S. OliveiraReceived: 22 September 2009 Accepted: 3 May 2010 Published online: 18 May 2010Springer Science+Business Media B.V. 2010Abstract :The concentrations and loadings of major and trace elements in coal mine drainage (CMD) from 49 abandoned mines located in the coal fields of the Brazilian state of Santa Catarina were determined.The CMD sites typically displayed a wide spatial and temporal variability in physical and geochemical conditions. The results of our CMD analyses in Santa Catarina State were used to illustrate that the geochemicalprocesses in the rock piles can be deduced from multiple data sets. The observed relationship between the pH and constituent concentrations were attributed to (1) dilution of acidic water by nearneutral or alkaline groundwater and (2) solubility control of Al, Fe, Mn, Ba and Sr by hydroxide, sulfate, and/or carbonate minerals. The preliminary results of the CMD analyses and environmental health in the Santa Catarina region, Brazil, are discussed.Keywords :Brazilian coal mining Coal mine drainage Drainage management Environmental impactsIntroduction A coal mining project can be seen to be a valuable resource in terms of its contribution to the local and national economy and its associated impact on society (Sekine et al. 2008). However, the cost associated with reclamation, mitigation, and monitoring of improperly controlled and abandoned mines can be staggering. In addition, one of the major environmental concerns related to coal mining is the contamination of surface and ground waters as a result of surface disposal of waste rock. These waste materials typically contain variable amounts of sulfide minerals. After disposal, exposure to atmospheric oxygen and water results in sulfide oxidation and the formation of mine drainage with variable pH, SO4 2-, and heavy metal content. When coal is mined, pyrite is exposed to oxygen and water, setting off a series of reactions that can result in lowered pH (unless there are sufficient carbonates to neutralize acids produced by oxidation and hydrolysis) and the release of high concentrations of metals, such as iron (Fe), aluminum (Al), and manganese (Mn). Potentially toxic trace elements, such as arsenic (As), mercury (Hg), lead (Pb), and selenium (Se), may also be released. In addition to causing poor water quality, mine drainage can affect the substrate of a stream. Ferrous iron (Fe2?) is oxidized to ferric iron (Fe3?) to form a precipitate on the substrate (commonly referred to as yellow boy) in the presence of water when the pH is greater than about 3.5 (Rose and Cravotta 1998). In many minedrainage streams with a relatively high pH, precipitated iron and aluminum may coat the stream substrate and cause an unstable habitat for macroinvertebrates (Schmidt et al. 2002; Simmons et al. 2005). The pH of a solution is an important measure for evaluating aquatic toxicity and corrosiveness (Cravotta 2008). The severity of toxicity, or corrosion, tends to be greater under low-pH or high-pH conditions than at near-neutral pH because the solubility of many metals can be described as amphoteric, with a greater tendency to dissolve as cations at low pH or anionic species at high pH (Langmuir 1997). For example, Al hydroxide and aluminosilicate minerals have their minimum solubility at pH 67 (Nordstrom and Ball 1986; Bigham and Nordstrom 2000), and brief exposure to relatively low concentrations of dissolved Al can be toxic to fish and other aquatic organisms (Baker and Schofield 1982). Anions, including SO4 2-, HCO3 - and, less commonly, Cl-, can be elevated above background concentrations in coal mine drainage (CMD) (Cravotta 2008), and polyvalent cations such as Al3? and Fe3? tend to associate with such ions of opposite charge (Nordstrom 2004). Ion-pair formation, or aqueouscomplexation reactions, between dissolved cations and anions can increase the total concentration of metals in a solution at equilibrium with minerals and can affect the bioavailability and toxicity of metal ions in aquatic ecosystems (e.g., Sparks 2005). Eventually, the solutions can become saturated, or reach equilibrium, depending on the various sulfate, carbonate, or hydroxide minerals that establish upper limits for the dissolved metal concentrations. In this study, we analyzed 49 samples of abandoned CMD at mine dumps in Santa Catarina State, Brazil, identifying the geochemical processes which give rise to its acidic character and evaluating the effects of the selective spoil management on its characteristics. The variation in the water chemistry is also discussed within the framework of the results. This preliminary study of the existing CMD in Santa Catarina State relates to minerals exposed during coal mining (coal cleaning residues, CCR) and the relevant geochemical processes that explain the origin of the main elements present. Coal zones of Santa Catarina State The rivers of Santa Catarina State (Tubarao, Urussanga, and Ararangua) receive the effluents generated at the coalmines. Contamination of the water resources is due to coal drainage from 134 strip mine sites covering a total area of 2,964 ha, 115 waste deposit areas on a total of 2,734 hectares, 77 sites on 58 hectares with acidic pools, and hundreds of underground mines (ABMC 2008). However, the production and circulation of acidic streams in dump areas create a problem for land reclamation as it impedes the establishment of vegetation and even causes the disappearance of already wellestablished vegetation (SIECESC 2008). The contact between spoils of different permeabilities allows the frequent outflow of sub-superficial water from the banks that are interconnected with the general circulation. Soil restoration work includes the use of correctors, such as lime or ashes from lignite combustion, inorganic and organic fertilizers and, on some occasions, the spreading of a layer of topsoil. The different types of spoils dumped and the procedures used have given rise to a wide variety of physicochemical conditions at the dump surfaces. Fig. 1 Location of the Santa Catarina coal basinThe environmental problems are the result of 120 years of mining activity and other pollution sources. In 1980, the Santa Catarina Coal Region (Fig. 1) was designated a Critical National Area for Pollution Control and Environmental Conservation. Due to this grave situation, the Federal Attorney General filed suit in 1993 against the federal and state governments and coal companies, seeking environmental recovery of the areas affected by coal mining in addition to termination of the environmental degradation by the active mines. In 2000, a federal judge in Criciuma, Santa Catarina, ordered the government-run companies to establish a recovery project within 6 months that would be implemented over 3 years and encompass the damage caused by coal mining activities in the entire coal region in the southern part of the state (SIECESC 2008). Methods and analytical procedures Water In this study, we characterized the physico-chemical properties of waste effluent at selected acid-producing mine sites. The field work was performed during several weather seasons in 2005 (January, March, May, July, September, November) and 2006 (February, April, October, December) and included a comprehensive and detailed exploration of the study area. Forty-nine water quality control samples, the locations of which were determined by GPS, were collected from the different restoration areas, categorized as four coal mine groups (Table 2): Lauro Muller, Criciuma, Treviso and Urussanga cities. These exact locations were chosen for the study because (1) the location showed a comparatively lower resistance than surrounding areas (i.e., an indication of CMD source material); (2) nearby wetlands showed evidence of acid mine drainage (AMD); (3) the location was readily accessible and contained existing monitoring wells; (4) nearby seeps could be used to identify the hydraulic gradient for monitoring purposes. Water samples were collected in 1-L Teflon bottles that was then split into rinsed polythene bottles; preservation was done by standard methods (Clescerial et al. 1998). Water quality Various trace elements, such as As, Co, Cu, Pb, Ni, Se, uranium (U), and Zn, are concentrated in coal (Table 1) and are harmful to the health of aquatic and Table 1 Average values for the trace elements in the Santa Catarina CCR (ppm) Table 1 Average values for the trace elements in the Santa Catarina CCR (ppm)Element Santa Catarina (CCR)aBraziliancoalbWorldcoalcAs6.0-43.724.40.5-80Ba300N/A0.5-150Be2.2-5.12.20.5-5Co1.2-13.16.00.5-30Cu CrHgMo Ni PbSb Se Sr SnTh U V Zn14.3-39.739-570.192.7-6.64-2326.8-139.80.4-2.14.3-9.43.8-5.710.3-616.113.8-22.84.9-1676.8-105.516.5-297.416.015.00.173.314.011.01.22.8N/AN/AN/A2.122.053.00.1-500.5-600.0120.1-100.1-502-800.05-100.2-100.1-50.5-2500.1-50.1-52-1005-300Environmental health and dynamics of surfaces waters The toxicity in the waste was mainly due to the presence of different metals, namely, Pd, cadmium (Cd), As, Cr, among others, with Al also being toxic to fish. The residue released during the process could be either recycled for further processing or sent for safe disposal without affecting human health. At surface coal mines, where the overburden chemical processes are dominated by either calcareous or highly pyritic strata, the prediction of postreclamation water quality is relatively straightforward. However, at sites where neither of the two abovementioned processes clearly predominates, predicting post-reclamation water quality can be complex. Ten years ago, researchers and scientists (Silva 2006; SIECESC 2008) found that at these more difficult-topredict sites, overburden analysis procedures generally used to predict post-reclamation water quality at surface coal mines were no more reliable than flipping a coin. Since this time, a great deal of effort has gone into improving the procedures (ABMC 2008). It should be noted that this study reports only on those components relevant to the prediction of water quality at surface mines where coal is being mined. Although the general approach is similar, the issues and interpretation of results can be quite different for hard rock operations and underground coal mining. Statistical analysis of surface water quality data in coal mining areas from unmined, abandoned mine, and reclaimed sites in Santa Catarina showed that there were significant differences in stream flow pH, specific conductance, alkalinity, and concentrations of metals between abandoned mine, and unmined sites (SIECESC 2008). Streams at reclaimed sites had average pH values and Al concentrations similar to those in unmined sites. The average specific conductance and sulfate concentrations of stream water were about the same at reclaimed and abandoned-mine sites, but they were significantly lower at unmined sites; specific conductance and sulfate concentration actually proved to be reliable indicators of basins that had been disturbed by mining (Oliveira and Silva 2006). Conclusions Regional water quality data were collected in 2005 2006 at 49 CMD sites in Santa Catarina State, Brazil. The variability in the CMD hydro-geochemistry enables different conditions of pH, Eh, DO, oxidation rate of Fe(II), and metal contents to be determined among the studied effluents. These different conditions have strong implications as they introduce additional difficulties into the design of corrective measures at the mine sites. Our results demonstrate that selective management of spoil sites is the restoration practice that offers the best protection against contamination of surface and subsurface waters, providing a suitable procedure to apply in the future construction of dump surfaces. Improvement in the quality of drainage systems using this practice can significantly reduce the cost of treatment in the purification plant prior to effluents being discharged to the receiving catchment zone. Future work should investigate the relationships between the stability of surface precipitates. AcknowledgmentsThis work was conducted by FEHIDRO and Environmental Foundation of Santa Catarina State (FATMA). We are grateful to Mr. Frans Waanders, R.B. Finkelman, Cidnei Galvani, Rui, Fernando A.R. Guedes, and Marcio Pink and for invaluable collaboration in the structural work. BASF, S.A. (Brazilian) conducted most of the chemical analyses (in special management, Bruno Sina). The authors acknowledge logistical support from the coal mining companies (access to samples).References 1ABMC. (2008). Available at: .br. Accessed 12 May 2008. 2Baker, R., & Schofield, C. L. (1982). Aluminum toxicity to fish in acidic waters. Water, Air, and Soil pollution, 18, 289309. 3Bigham, J. M., & Nordstrom, D. K. (2000). Iron and aluminum hydroxysulfate minerals from acid sulfate waters. Reviews in Mineralogy and Geochemistry, 40, 351403.4Borda, M., Elsetinow, A., Schoonen, M., & Strongin, D. (2001). Pyrite-induced hydrogen peroxide formation as a driving force in the evolution of photosynthetic organisms on an early Earth. Astrobiology, 1, 283288. 5Carlson, L., Bigham, J. M., Schwertmann, U., Kyek, A., & Wagner, F. (2002). Scavenging of As from acid mine drainage by schwertmannite and ferrihydrite: A comparison with synthetic analogues. Environmental Science and Technology, 36, 17121719. 6Clescerial, L. S., Greenberg, A. E., & Eatan, A. D. (1998). Standard methods for examination of water and waste water (pp.3.373.38), 20th edn. Washington, DC: APHA, AWWA. 7Cohn, C. A., Borda, M. J., & Schoonen, M. A. (2004). RNA decomposition by pyrite-induced radicals and possible role of lipids during the emergence of life. Earth and Planetary Science Letters, 225, 271278. 8Cravotta, A. C. (2008). Dissolved metals and associated constituents in abandoned coal-mine discharges, Pennsylvania, USA. Part 1: Constituent quantities and correlations. Applied Geochemistry, 23, 166202. 9Earle, J., & Callaghan, T. (1998). Effects of mine drainage on aquatic life, water uses, and manmade structures. In K. B. C. Brady, & M. W. J. Smith (Eds.), Coal mine drainage prediction and pollution prevention in Pennsylvania, 5600-BK-DEP2256, 4.14.10. 10Harrisburg, PA: Pennsylvania Department of Environmental Protection. Herr, C., & Gray, N. F. (1995). Sampling riverine sediments impacted by acid mine drainage: Problems and solutions. Environmental Geology, 29, 3745. 11Kalkreuth, W., Holz, M., Kern, M., Machado, G., Mexias, A., Silva, M. B., et al. (2006). Petrology and chemistry of Permian coals from the Parana Basin: 1. Santa Terezinha, Leao-Butia and Candiota coal fields, Rio Grande do Sul, Brazil. International Journal of Coal Geology, 68, 79116. 12Pires, M., & Querol, X. (2004). Characterization of Candiota (South Brazil) coal and combustion by-product. International Journal of Coal Geology, 60, 5772. 13Querol, X., Izquierdo, M., Monfort, E., Alvarez, E., Font, O., Moreno, T., et al. (2008). Environmental characterization of burnt coal gangue banks at Yangquan, Shanxi Province, China. International Journal of Coal Geology, 75, 93104.14Silva, L. F. O., Oliveira, M. L. S., da Boit, K. M., & Finkelman, R. B. (2009b). Characterization of Santa Catarina (Brazil) coal with respect to Human Health and Environmental Concerns. Environmental Geochemistry and Health, 31, 475485. 15Smith, K. S., & Huyck, H. L. O. (1999). An overview of the abundance, relative mobility, bioavailability, and human toxicity of metals. Reviews in Economic Geology, 6A, 2970. 巴西圣卡塔琳娜地区煤炭开采污水排放和环境健康的初步研究路易斯 F O 席尔瓦， 马库斯 伍仑斯拉格，马科斯 L S 欧雷维拉收到日期：2009年9月22日采纳日期：2010年5月3日在线出版日期：2010年5月18日摘 要：本文对坐落在巴西圣卡塔琳娜地区的49座废弃矿井排弃废水中的主要和微量元素进行了测定。这些进行CMD测试的地点在物理和地球化学方面存在很大时间和空间上的差异性。我们在圣卡塔琳娜地区进行的CMD测试分析可以说明岩层中的物理化学变化可以通过一套模型数据的确定来推导演绎出来。已经观测到的PH值和浓度之间的关系如下（1）酸性水被附近的中性或碱性水所稀释（2）铝、铁、锰、钡和锶元素与含氢、硫酸盐和碳酸盐的矿物质反应从而可溶于水。巴西圣卡塔琳娜地区CMD的分析和环境健康的评估在本篇文章作为主要讨论内容。关键词：巴西煤炭开采，矿井排水，排水措施，环境影响。正文由于一个煤矿工程可以为当地的经济发展做出贡献并且会对社会上相关行业产生好的影响，所以煤炭被看做是一种有价值的资源。然而采空区的充填以及对不当开采和废弃矿山监测的成本却令人咋舌。除此之外，煤炭开采带来的主要环境问题之一是因为地表塌陷和废弃矸石所造成的地表水和地下水污染。这些废弃物主要包含了大量的硫酸盐矿物。在塌陷之后挥发到大气层中或者溶于水中导致酸雨，形成多种PH值的含SO4-2和重金属的煤矿废水。当一个煤矿进行开采时，其中混杂的铁矿石与氧气和水接触，发生一系列的化学反应产生一定的酸性（除非有足够的碳酸盐和硫酸盐来中和 由于接触空去和水所产生的酸根离子）并且释放高浓度的金属离子，比如说铁、铝和锰。一些具有潜在毒性的微量元素例如砷、汞、铅和锶也可能会释放出来。除了会导致水质量恶化，煤矿污水也会污染溪水或河流的水源。当ph值大于3.5时水中的+2价铁离子会被氧化成+3价铁离子，在水中形成一种沉淀物。在很多PH值相对较高的受煤矿污水污染的河流中，沉淀的铁和铝会覆盖在河底,造成大型无脊椎动物栖息地的不稳定和恶化。 一个地方水体的PH值对于评估毒性和腐蚀性是非常重要的。在酸性或者碱性水体中上述毒性或腐蚀性的严重程度要比接近中性的水体中高的多，这是因为许多金属更容易在酸性和碱性环境中充分的溶解。例如，铝及其化合物在PH=6-7时在液体中的溶解度最小，但是和相对较低浓度的铝离子溶液短暂的接触就会对鱼类和其他水中的有机物造成毒性。阴离子包括SO4-2，HCO3-和少量常见的Cl-，这些离子的浓度都会在煤矿污水中升高。通过溶解在水中的金属和阴离子的反应生成物还会使金属离子的浓度增加直至与矿物质达到平衡，这也会影响水下生态系统中金属离子的生物利用和自我恢复能力。最终这种过程根据不同的硫酸根、碳酸根或者离子型态的金属元素所建立起的水体溶解上限达到一种平衡。在这项研究中，我们分析了圣卡塔琳娜地区49个废弃的CMD矿井污水样本，证明了这种化学变化使得其酸性加强，评估了有选择性的根据水体的酸碱性使之变质的影响。水中的化学反应也在结果中加以探讨。这项对于圣卡塔琳娜地区现存的CMD初步研究与在煤炭开采时暴露在空气或水中的矿物质有关，同时也与地球物理化学变化过程有关，这种变化可以解释现在这些主要物质元素的起源。圣卡塔琳娜地区煤田分布圣卡塔琳娜地区的河流汇集了由于煤炭开采产生的污水。这些水资源受到污染是由于在方圆2964公顷范围内存在的134个矿井的污水排放点以及在方圆2734公顷的范围内115个废弃物沉淀聚集地区，占地58公顷的77处酸性污水池和上百个井工开采的煤矿。然而在采空区上方的一些呈酸性的河流的流动也会造成一些关于地表恢复的问题，因为这些酸性河流会阻碍地表植被的形成甚至会导致已经形成的植被的消失。不同渗透性的腐蚀性水体之间的接触会导致与正常水体相联系的表层河流水频繁的外流。地表土壤的恢复工作包括使用正确的措施，比如喷洒植物燃烧留下的灰烬，使用有机和无机肥料，在某些特殊情况下还可以重新铺盖一层表土。由于不同的污染物会排放出来，因此在污染物污染的地表，上述方法会产生不同的物理、生物化学变化。现在的环境问题是在过去120中的采矿活动和其他污染源共同导致的结果。在1980年，圣卡塔琳娜矿区被认为是一个“亟待需要控制污染保护环境的地区”。因为这样严峻的现实，在1993年联邦检察部门起诉各州的政府和煤炭企业以期达到恢复被煤炭开采污染的环境，并且终止被仍在进行的煤炭开采活动造成的环境恶化。2000年圣卡塔琳娜地区Criciuma的法官下令政府开办的企业要在六个月内开始一项环境恢复工程，这项工程为期不少于三年，工程的任务要围绕并解决在州南部地区所有的煤田造成的环境污染问题。表1.圣卡塔琳娜地地区煤田位置方法和分析步骤水资源 在这项研究中，我们详细描述了在已选择的酸性污水产生地产生的酸性污水的物理和化学性质。现场的测试工作在2005年（1月，3月，5月，7月，9月，11月）和2006年（2月，4月，10月，12月）的不同季节与气候条件下进行，包含了对该地区广泛而细致的探索。49种水质样本是在不同的被GPS定位的恢复地区收集的，被分为4种矿井种类（表2）：Lauro Muller, Criciuma, Treviso and Urussanga cities。这些精确的位置被本研究所采用是因为：（1）这些地区比周边地区更倾向于不反对本研究（2）附近的湿地有证据表明被酸性矿井污水污染（3）这些地区交通方便且有现成的监测矿井（4）周围的渗透层可以用来验证监测地区的水力梯度变化。取出的水样被装在编号为1-L的聚四氟乙烯瓶中然后被装入漂洗过的聚乙烯瓶中，所有的保护措施都是按照标准方法完成的。水质多种不同的微量元素，例如砷，钴，铜，铅，铌，锶，铀和锌都会浓缩在煤中并且对水生生物健康造成危害。表1圣卡塔琳娜地区微量元素的平均值CCR(ppm) 元素名称圣卡塔琳娜巴西世界范围内砷6.0-43.724.40.5-80钡300N/A0.5-150铍2.2-5.12.20.5-5钴1.2-13.16.00.5-30铜铬汞钼镍铅锑硒锡锶钍铀钒锌14.3-39.739-570.192.7-6.64-2326.8-139.80.4-2.14.3-9.43.8-5.710.3-616.113.8-22.84.9-1676.8-105.516.5-297.416.015.00.173.314.011.01.22.8N/AN/AN/A2.122.053.00.1-500.5-600.0120.1-100.1-502-800.05-100.2-100.1-50.5-2500.1-50.1-52-1005-300环境健康和地表水的运动污水中的毒性主要是来自里面不用的金属