arsenic contamination in soils, water and plants
Arsenic contamination in soils, water and plants surrounding gold mine in Thailand Thares Srisatit1, Wanpen Wirojanagud2, Thanes Weerasiri3 Faculty of Environmental Engineering, Chulalongkorn University, Thailand Faculty of Environmental Engineering, Khonkaen University, Thailand Faculty of Science and Technology, Thammasat University, Thailand ABSTRACT Arsenic contamination is of very high concern due to the activities of Gold Mine situated at Wangsaphung district, Loei province, far away approximately 550 km from Bangkok to the northeast of Thailand For the purpose of preventive measure and land use management in near future, the samples of top soils, water and plants were collected from the surrounding area of Gold Mine, within watershed covering gold mine and nearby watershed, to conduct the contamination testing Laboratory test results have shown that all of those samples were contaminated with arsenic and contaminant levels in average are of 1.34 – 497.94 mg/kg in soil, – 0.3 mg/kg in plants and 0.001-0.01 mg/l in surface water Contamination in soils and plants were found higher much larger than those in surface water flown from the tailing of gold mining disposal pond As of these results, It reasonably indicates that there naturally exists the arsenic contaminated throughout the area not only within watershed in which the gold mine situated but also in the outside area The remarkable contamination of arsenic in the environment that were founded in some specific positions were typically the cause of human activities such as gold mining, agricultural management or others in land use INTRODUCTION Exposure to arsenic can result in a variety of health problems in humans, including various forms of cancer (e.g skin, lung, and bladder), cardiovascular and peripheral vascular disease, and diabetes Human encounter arsenic from natural and anthropogenic sources (Henke, 2009) Environmental Protection Agency (U.S EPA) specified that the arsenic contamination in drinking water should be less than 10 μg/l In case of soils used for agriculture and for other usages, the Office of National Environment Board of Thailand set the maximum concentration limits (MCL) being of 3.9 mg/kg and 27 mg/kg, respectively Arsenic enters the environmental through herbicides, wood preservatives, and mining industry (Chopra, Parmar, 2007) It can distribute in either soil or water, transport to other places, pollute to water resources, and subsequently affect water for daily consumption Gold mining also contributes to the distribution of arsenic During gold extraction, arsenic, which is the composition of Arsenopyrite, is also separated and diffused into soil and water, and pollutes to the environment Gold mining at Wangsaphung district, Loei province of Thailand, is the one of mining industry that encountered this problem After starting its work in 2006, villagers from villages complained that the natural water they normally use become contaminated with arsenic resulting in affected human life, which has never been before Related government agencies and staffs from the gold mine have investigated the arsenic contamination in both surface water and groundwater; however, they revealed that the contamination levels were not more than MCL specified by U.S.EPA As of those results, there are still much more suspects that why villagers were threatened by arsenic or arsenic contaminated in other medias not only in the water To acquire the solution, this study was performed to investigate the contaminant of arsenics in soils and plants compared to those in water The study areas were located not only within the interesting sub-catchment area that covering gold mine and mostly risky villages but also in the outside area to verify that the arsenic contaminants have been formerly existed or really diffused from the gold mine The results would give the preliminary informations for planning to use in this area which will be advantageous for managing the agriculture and living area in near future GENERAL INFORMATION Loei, one of 76 provinces of Thailand, is situated in Northeastern part attached to the Maekong River and border of Lao People's Democratic Republic The study area, which is mountainous and plateau area, is in Wangsaphung district of Loei province (Fig.1) The altitude of gold mine is about 300 meters from mean sea level Within kilometers from the gold mine has 10 villages, and there are villages that have the most impact from arsenic, including, Ban Nam Huai, Ban Na Nong Bong, Ban Huai Phuk, Ban Kok Sathon, Ban Kaeng Hin, and Ban Tak Daed (Fig.2) The nearest village to the gold mine, 250 meters from the mine and at the altitude of 277 meters from the mean sea level, is Ban Na Nong Bong village In those villages, the farthest one is Ban Tak Daed, which is kilometer from the mine and at the altitude of 276 meters from the mean sea level Most of lands were engaged in farming and cropping plants such as corns, tapiocas, soybean, and rubber trees Within sub-catchment area covering the gold mine and villages, there are many small waterways, such as Huai Nam Chan, Huai Muno, Huai Haeng, Huai Khok Yai and Huai San, flowing from high elevation at the top of plateau directing to low elevation area and combining altogether to be one stream, called Nam Huai stream, before passing through villages and out of the sub-catchment area into Loei River The direction of surface water flow is shown in Fig.3 The burnt rice affected by arsenic (Fig.4), claimed by the villagers, was found at the Phulek creek (Fig.5) SAMPLING COLLECTION AND TESTING Plants, soils and water samples at six locations had been taken in order to quantify the leveling of arsenic contaminant Five sampling locations are within the interesting sub-catchment area whose boundary covers gold mine and affected villages; the other one location, location no.5, was determined to be control point or reference point at the area outside The locations of samplings were shown in Fig.6 Detailing of samplings are described as follows: • Plants sampling: Total amount of 125 plant samples were collected from those locations previously described At each location, both annual crops and perennial plants had been gathered to examine the level of arsenic contaminated in plants Oak ferns that are likely to grow up near water way as in location No.3, No.4 and No.6 were also collected for contamination testing Some plants such as common tobacco (Nicotiana tabacum), Lemon grass (cymbopogon citratus Stapf), etc, are skipped out in some locations because of having no cultivation in those areas • Soil sampling: At each location, one borehole was drilled into the ground to the depth of meter from the existing ground level and soil samples were collected at each 0.50 meter from surface through the bottom depth of borehole In order to identify soil types in accordance with Unified Soil Classification System, methods of drilling and collecting soil samples were performed following the guidance of American Society for Testing and Materials (ASTM, 2000) Each soil sample was measured pH value before wrapping with foil sheet and coated with paraffin to protect the moisture loss and oxidizing reaction that might be occurred during carry on for further tests in laboratory The positions of each borehole are at the corresponding location number such as BH1 at location No.1, BH2 at location No.2 and so on as depicted in Fig.6 As clearly seen, BH5 is at location No.5, that is Ban Kok Chumsaeng, at outside the interesting sub-catchment studied area • Water sampling: At the same location of soil and plants samplings, surface water were collected for arsenic contamination testing One sample was taken for each location except the location No.6 that four samples were intentionally collected around that area because there are small water ways pass through, one of which flows from the high elevation swamp that is not far from mine tailings All positions of water samplings are at the same locations as plants and soils sampling (Fig 6.) The samples are treated to remain acidic by nitric acid (5% concentration), poured in the light brown bottles for laboratory test • Testing: Inductively Coupled Plasma Mass Spectrometry (ICP-MS) method was utilized to quantify the arsenic contaminants in either soil or water This technique provides high precision determination of substance, even metallic or non-metallic, from relatively small amount of samples (Skoog et al., 2007) The procedure starts from grinding/homogenization, weighing, digestion, dilution, and final measurement Since this technique related to analytical chemistry and spectrometry, more details of this method can be found in Bailey et al, (2003) RESULTS AND DISCUSSION • Arsenic contamination in plants Annual crop: Laboratory results as shown in table1 reveal that there are arsenic contaminant in plants at all locations At each location Pumpkin leaves (Cucurbita moschata Duchesne) is the most arsenic contaminated annual crop Taro leaves (Colocasia esculenta (L.) Schott), Soy bean leaves (Glycine max (L.) Merr.) and Common tobacco leaves (Nicotiana tabacum L.) also have been contaminated in great values but somewhat less than Pumpkin leaves It was found very less contamination in Lemon grass (Cymbopogon citratus Stapf) Chilli pepper (Capsicum frutescens L.) and Sesbania flowers (Sesbania javanica Miq.) except at Location No.6 Lemon grass and Chilli pepper seem to be contaminated in significantly higher value To determine as overall perspective, arsenic contents of all plant samples were plot versus locations which being arranged in sequential manner from high elevation to lower elevation as shown in Fig.7 Determining the graph, among six locations the contamination levels in Pumpkin leaves (Cucurbita moschata Duchesne) and Taro leaves (Colocasia esculenta (L.) Schott) are of highest values at location No.2, the values are1.04 mg/kg and 0.70 mg/kg respectively for each plant; and contaminant levels in thus plants are consecutively lower at the location No.6, No.3 and No.1 Perennial plants: From table1, at each location Burmes grape (Baccaurea ramiflora Lour.) was the plant that having been contaminated the most; except for location No.4 that Tamarind fruit (Tamarindus indica L.) is insignificantly higher more than Burmes grape Contamination level of all samples from location No.1 and No.3 are significantly high as compared to all of those in the other locations Also as in annual crops, the contaminant level in Burmes grape (Baccaurea ramiflora Lour.), the most contaminated perennial plant, is highest at location No.2 and consecutively lower at location No.6, No3 and No.1 as shown in Fig.7 Fern: Oak fern (Dryopteris amboinensis Ktze.F) at location No.6 was contaminated at the amount of 0.67 mg/kg which is the greatest value At location No.3 and No.4, arsenic contamination in Oak fern (Dryopteris amboinensis Ktze.F) are of 0.23 mg/kg and 0.16 mg/kg, respectively As a result described above, it can be seen that there are arsenic contamination in plants at all locations and are of primarily high to lower quantities from location No.2, No.6, No.3 and No.1 respectively There are very most uptakes in Pumpkin leaves (Cucurbita moschata Duchesne) for annual crops, Burmes grape (Baccaurea ramiflora Lour.) for perennial plants and also Oak fern (Dryopteris amboinensis Ktze.F) at location No.6 Considering topographic map and location studied (Fig.6), it may be possible to give a reason that Location No.2 is very close to gold mine thus confronting directly to water contaminated with some unintended pollutants including arsenic More likely in location No.6, its position is at the mountain pass, called Phulek creek, through which it was passed by small waterways coming from the high elevation swamp that is not far from mine tailings; it would be a greater chance for this location to be contaminated with arsenic than the location No.3 and that are even beside waterway but farther away Initially, Arsenic contaminant in plants as foregoing delineated seem to be the cause of pollution from swamp closed to mine tailings; however, evidence from plant samples at location No.5 outside sub-catchment area, exhibit that there are also arsenic contamination in plants and content levels are not much less than of those within the interesting area So it can be stated that, in reality, there are arsenic naturally dispersed throughout the areas Arsenic contamination in soil Soil samples from locations, called in corresponding points as bore holes (BH) number, were classified using the Unified Soil Classification System Soil profiles and their altitudes were arranged in the orderly manner from high to lower existing ground elevation, those are BH5, BH2, BH6, BH3, BH1 and BH4, respectively, as shown in Fig.8 The soil profile of each borehole is relatively similar composed of alternating layers between clay, silty clay and sandy silty clay which are smaller grain sizes and higher cohesion than purely sandy soils Because of their small grain sizes and high cohesions, it causes leading to be low permeability medias Laboratory test results show that all soil samples of boreholes have arsenic contaminants (Table 2) The relationship between concentration of arsenic with depth for boreholes shown in Fig.9 displays that there are arsenic contaminated throughout the depth of root zone, meter from soil surface Content levels of arsenic contaminated in soil from low to high are BH2, BH5, BH4 and BH6, respectively, and contaminant levels in BH3 is in between BH2 and BH5 Soil samples of BH5, which its location is outside the interesting area, have higher arsenic concentration at the upper layer than lower depth Visible evidence from Fig.9 exhibits the most Arsenic contaminated soil is at BH6 The contamination levels in BH6 are substantially high at the top and steeply decrease at lower depth; the concentration levels are of 56.17 mg/kg soil to 8.00 mg/kg soil, from highest to lowest value, respectively, which are higher than the maximum concentration level (MCL) allowable level for soils used for living and agriculture specified by The Office of the National Environment board of Thailand By this specification, the arsenic contaminant for dwelling and agriculture area must be less than 3.90 mg/kg soil, and for other usages must be less than 27 mg/kg soil Contamination levels at BH are much less than those of BH6 but still exceed MCL Determining location of each Bore Hole in topographic map, the location of BH6, corresponding location No.6 in plant samplings, is at the mountain pass called Phulek creek as previously described It can possibly give a reason that the substantially high arsenic concentration at the top of soil profile in BH6 is the cause of arsenic pollutant exposed from the area near mine tailings and being carried by surface flow or seepage water downward and thus accumulating at this location At lower depth of BH6, arsenic concentration decreases to the minimum value close to the concentration of BH4 It can be noticed that the arsenic concentration values at the bottom depth of both BH6 and BH4, which is both nearby the waterway, come close together; this value might be the minimum contaminant concentration in soils seated beside along the water way BH5 at outside interesting area also has much high arsenic concentration more than MCL at nearly the top and gradually decrease with depth; it exhibits the natural existence of arsenic in the area around Overall perspective view, concentrations of arsenic in BH1, BH2 and BH3 are much less than of those in the other boreholes and somewhat near or less than the MCL • Arsenic contamination in water Laboratory results show that the amount of arsenic in surface water at location No.1, No.2, No.3, No.4 and location No.5, as shown in table 3, are less than 0.01 mg/l, which is an MCL for drinking water specified by U.S EPA In contrast, at location No.6 there are samples of water including sample No.6.1, No.6.2, No.6.3 and No.6.4; all of them have arsenic concentration much significantly higher over the MCL as shown in Fig.10 At location No.6, Phulek creek, which is the toe of mountainous pass as described before; the high level of arsenic concentrations in this location match up the results of contamination in plants and soils that are also so much high in this location Initially, it may be likely to conclude that the highly contaminated level of arsenic at the top surface of soil, water and plants in this location, No.6, tends to be the result of arsenic transportation from nearby swamp CONCLUSION This study reveals that the arsenic contaminant can be found in plants, soils and surface water at all locations The contaminations have been occurred not only in the studying sub-catchment area but also the area outside Therefore it would be possible that the arsenic naturally exists over there long time before At some locations, there has been much higher concentration than those in the other locations due to the accumulation of arsenic carried by water As we can see at soil borehole No.6 (BH6) and borehole No.4 (BH4), which are beside the waterway, there are much higher of arsenic concentrations and their values are more than 3.9 mg/kg, which is the specification of soil for dwelling and agriculture specified by the Office of the National Environment Board of Thailand The remarkable contaminants of arsenic in Surface water at location No.6 consistently agree with those in top soil at the same location This position is the toe of mountain pass, where the water flow from the upper area, which is the swamp closed to mine tailings The water might carry down the arsenic, that may pollute in the swamp, and take it settle at downstream Contamination in root zone of meter depth soils and in plants stated that arsenic already enters the food chain Consequently, increasing attention should be paid for preventing, managing and remediation Further studies of arsenic distribution trend and its transportation phenomena are of very much interest in this area especially in soil media because nowadays it contaminates into food chain which may pose serious health risk to human life The influence factors for studying the behavioral distribution of arsenic such as the geological characteristics, compositions of soil, porosity and permeability of soil, land use, and soil loss etc., may be needed to be determined These are important for analyzing the arsenic mobility, which would be beneficial for planning and management of area for dwelling and other usages in near future REFERENCE American Society for Testing and Materials (2000) Annual Book of ASTM Standards Vol.04.08, West Conshohocken, PA Bailey, R.M., Stokes, S and Bray, H (2003).Inductively-Coupled Plasma Mass Spectrometry (ICP-MS) for dose rate determination: some guidelines for sample preparation and analysis Oxford, UK: Oxford Luminescence Research Group, School of Geography and the Environment, University of Oxford Chopra, H.K and Parmar, A (2007) Engineering Chemistry - A Text Book India: Alpha Science International Ltd., 5-10 Henke, K.R (2009) Arsenic – Environmental Chemistry, Health Threats and Waste Treatment 1st ed John Wiley & Sons Ltd., 1-5, 238-243 Plant Genetic Conservation Project Under the Royal initiative of Her Royal Highness Princess Maha Chakri Sirindhorn Plant genetic resources Retrieved September 1, 2010 from http://www.rspg.or.th/plants_data/index.htm Skoog, D.A., Holler, F.J and Crouch, S.R (2007).Principles of Instrumental Analysis 6th ed Canada: Thomson Brooks/Cole, 291-299 United States Environmental Protection Agency Arsenic in Drinking Water Retrieved February 10, 2010 from http://www.epa.gov/safewater/arsenic/index.html Fig.1 Study Area Phulek Creek Fig.2 location of gold mine and villages that have the mostly potential impact from arsenic Fig.3 River System Fig.4 Burnt rice field cause of arsenic contamination in soil and water Gold mine Ban Na Nong Bong Ban Huai Phuk Fig.5 location of phulek creek Study area Gold mine Phulek Creek 10 Fig.6 locations of plants, soil and surface water sampling Table Arsenic contamination in plants Concentration (mg/kg) Plant Type scientific name* Loc.No.1 Loc.No.2 Loc.No.3 Loc.No.4 Loc.No.5 Loc.No.6 Elev.262 Elev.280 Elev.267 Elev.254 Elev.282 Elev.274 (Cymbopogon citratus Stapf) (Capsicum frutescens L.) (Curcuma amada Roxb.) (Oryza sativa L var indica) 0.01 0.03 0.27 0.16 0.02 0.04 0.42 0.18 0.02 0.03 0.29 0.08 0.02 0.04 0.05 0.03 0.02 0.27 0.09 0.15 0.12 0.62 0.24 (Cucurbita moschata Duchesne) (Colocasia esculenta (L.) Schott) (Solanum melongena L.) (Psophocarpus tetragonolobus (L.) D.C.) (Zea Mays L.) (Zea Mays L.) (Glycine max (L.) Merr.) (Glycine max (L.) Merr.) 0.60 0.50 0.20 1.04 0.70 0.40 0.60 0.55 0.24 0.21 0.32 0.15 0.45 0.11 0.08 0.89 0.66 0.34 0.08 0.13 0.15 0.48 0.24 0.14 0.26 0.22 0.64 0.24 0.12 0.22 0.17 0.56 0.35 0.08 0.03 0.12 0.28 0.04 0.02 0.13 0.07 0.25 0.05 0.26 0.13 0.18 0.84 0.37 (Nicotiana tabacum L.) (Gossypium herbaceum L.) (Sesbania javanica Miq.) (Sesbania javanica Miq.) 0.48 0.06 0.01 0.07 0.42 0.08 0.02 0.09 0.28 0.07 0.04 0.13 0.03 0.01 0.04 0.07 0.03 0.10 0.06 0.03 0.07 (Carica papyya L.) (Baccaurea ramiflora Lour.) (Musa spp.) (Musa spp.) (Tamarindus indica L.) 0.30 0.80 0.36 0.38 0.30 0.20 1.04 0.02 0.04 0.20 0.28 0.90 0.28 0.30 0.50 0.18 0.20 0.12 0.12 0.28 0.20 0.42 0.01 0.03 0.20 0.22 0.87 0.02 0.03 0.10 - - 0.23 0.16 - 0.67 Annual crops Lemon grass Chili pepper Mango ginger Rice stem Pumpkin leaves Taro leaves Eggplant Wing bean Corn leaf Ear corn Soybean leaves Soybean pods Common tobacco leaves Cotton leaves Sesbania flowers Sesbania Perennial Papaya fruit Burmes grape Banana fruit Banana blossom Tamarind fruit Fern Oak fern (Dryopteris amboinensis Ktze F) * Plant Genetic Conservation Project Under the Royal initiative of Her Royal Highness Princess Maha Chakri Sirindhorn 11 As in Plant Lemon grass C hili pepper Mango ginger R ice stem P umpkin leaves Taro leaves E ggplant W ing bean C orn leaf E ar corn S oybean leaves S oybean pods C ommon tobacco leaves C otton leaves S esbania flower S esbania P apaya fruit Burmes grape Banana fruit Banana blossom Tamarind fruit Oak fern 1.20 1.00 As (mg/ kg) 0.80 0.60 0.40 0.20 0.00 Loc.No.5 (Elev.282) Loc.No.2 (Elev.280) Loc.No.6 (Elev.274) Loc.No.3 (Elev.267) Loc.No.1 (Elev.262) Loc.No.4 (Elev.254) Location (Elev.) Fig.7 Arsenic contamination in plants as compared between locations 12 Table Arsenic contamination in soil Depth (m.) 0.50 1.00 1.50 3.00 BH5 Elev 282 BH5 (Elev.282) 6.47 6.79 4.72 2.44 BH2 Elev 280 BH2 (Elev.280) 3.12 4.39 1.21 - Concentration (mg/kg soil) BH6 BH3 BH1 (Elev.274) (Elev.267) (Elev.262) 56.17 2.97 3.84 39.59 3.91 3.68 39.29 5.71 4.21 8.00 4.66 4.29 BH4 (Elev.254) 9.52 8.42 10.94 7.19 BH6 Elev 274 BH3 Elev 267 BH1 Elev 262 BH-4 Elev 254 13 Fig.8 Soil profiles and arsenic contaminated in soil relative to depth As (mg/kg) 10 20 30 40 50 60 0.00 BH5 (Elev.282) BH2 (Elev.280) BH6 (Elev.274) BH3 (Elev.267) BH1 (Elev.262) Loc.No.6.3 Loc.No.6.4 BH1 BH5 0.50 1.00 Depth (m.) BH6 Loc.No.6.3 Gold Mine BH3 2.00 BH4 2.50 Phulek Creek 14 3.00 MCL = 3.9 mg/kg ; Fig.9 Arsenic contamination in soil versus depth of all locations Table Arsenic Contamination in Waters 15 Sampling Location Concentration (mg/L) Loc.No.1 Loc.No.2 Loc.No.3 Loc.No.4 Loc.No.5 Loc.No.6.1 Loc.No.6.2 Loc.No.6.3 Loc.No.6.4 0.0011 0.0030 0.0010 0.0016 0.0022 0.0110 0.0210 0.0150 0.0110 Gold Mine 0.0250 Phulek Creek As (mg/L) 0.0200 0.0150 Surface water MCL = 0.01 mg/L 0.0100 MCL = 0.01 mg/L ; US Environmental Protection Agency (US.EPA) 0.0050 0.0000 Location Loc.No.1 Loc.No.2 Loc.No.3 Loc.No.4 Loc.No.5 Loc.No.6.1 Loc.No.6.21.50 11 Fig.10 Arsenic contamination in surface water as compared between locations 16 17 ... threatened by arsenic or arsenic contaminated in other medias not only in the water To acquire the solution, this study was performed to investigate the contaminant of arsenics in soils and plants compared... outside the interesting sub-catchment studied area • Water sampling: At the same location of soil and plants samplings, surface water were collected for arsenic contamination testing One sample... Bailey et al, (2003) RESULTS AND DISCUSSION • Arsenic contamination in plants Annual crop: Laboratory results as shown in table1 reveal that there are arsenic contaminant in plants at all locations