Environment International 35 (2009) 455–460 Contents lists available at ScienceDirect Environment International j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / e n v i n t Arsenic and other trace elements contamination in groundwater and a risk assessment study for the residents in the Kandal Province of Cambodia Thi Thu Giang Luu a,b, Suthipong Sthiannopkao a,⁎, Kyoung-Woong Kim a a b International Environmental Research Center, Gwangju Institute of Science and Technology, 261 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712, South Korea Hanoi University of Science, 334 Nguyen Trai Street, Hanoi, Vietnam a r t i c l e i n f o Available online September 2008 Keywords: Arsenic Manganese Lead Barium Groundwater Kandal Province a b s t r a c t Concentrations of arsenic and other trace elements in groundwater were examined at three villages (PT, POT and CHL) in the Kandal Province of Cambodia Concentrations of arsenic in the groundwater ranged from 6.64 (in POT village) to 1543 μg/L (in PT village), with average and median concentrations of 552 and 353 μg/L, respectively About 86% out of fifteen samples contained arsenic concentrations exceeding the WHO drinking water guidelines of 10 μg/L Concentrations of arsenic (III) varied from (in POT village) to 1334 μg/L (in PT village), with an average concentration of 470 μg/L In addition, about 67%, 80% and 86% of the groundwater samples had higher concentrations for, respectively, barium, manganese and lead than the WHO drinking water guidelines These results reveal that groundwater in Kandal Province is not only considerably contaminated with arsenic but also with barium, manganese and lead A risk assessment study found that one sample (PT25) had a cumulative arsenic concentration (6758 mg) slightly higher than the threshold level (6750 mg) that could cause internal cancer in smelter workers with chronic exposure to arsenic from groundwater High cumulative arsenic ingestion poses a health threat to the residents of Kandal Province © 2008 Elsevier Ltd All rights reserved Introduction The occurrence of high concentrations of arsenic (As), one of the most hazardous chemical elements in drinking water has been recognized, over the past two or three decades, as a great public health concern in several parts of the world (Mukherjee et al., 2006) As exists in varying concentrations within the shallow zones of groundwater in many countries, among them Argentina, Bangladesh, India, Pakistan, Mexico, Mongolia, Germany, Thailand, China, Chile, the USA, Canada, Hungary, Romania, Vietnam, Nepal, Myanmar and Cambodia (Mondal et al., 2006; Stanger et al., 2005) In particular, elevated As concentrations in groundwater have been identified and reported for many regions in Cambodia, such as Kratie, Kandal, and areas south and southeast of Phnom Penh (Berg et al., 2007; Buschmann et al., 2007; Buschmann et al., 2006; Kubota et al., 2003) The As in Cambodia may originate in a natural enrichment process by geothermal activities in the upper Mekong basin (Kouras et al., 2007; Mukherjee et al., 2006) Although surface water is still used as drinking water in some areas, groundwater from tube-wells, which is considered relatively free of pathogens, is one of the main sources of drinking water in Cambodia, especially in rural areas (Berg et al., 2007; Polya et al., 2005; Buschmann et al., 2007) However, in the year 2000, one small- ⁎ Corresponding author E-mail address: suthi@gist.ac.kr (S Sthiannopkao) 0160-4120/$ – see front matter © 2008 Elsevier Ltd All rights reserved doi:10.1016/j.envint.2008.07.013 scale drinking water quality survey of hand-pumped tube-wells in Cambodia identified As concentrations above 100 μg L− for the first time, much higher than the maximum contaminant level guidelines of the World Health Organization (10 μg L− 1) The As levels were particularly high in Kandal Province, with an average concentration of 233 μg L− (Berg et al., 2007; Buschmann et al., 2007; Kris, 2007; WHO, 2006) Recently in this province, about million people have stopped using surface water or water from shallowly dug wells due to bacterial diseases Instead, it has become popular to pump groundwater using individual, private tube-wells (Buschmann et al., 2007) For this reason, it is necessary to evaluate current As contamination levels in consumed groundwater in Kandal Province As can enter the human body in several ways, including through air, food and water; of these water is generally the most common medium of entry In water, As can be present in various oxidation states (+5, +3, 0, −3) (California Public Health Goal, 2004; Zhang et al., 2002) From contaminated water, As can be converted into insoluble compounds and can be co-precipitated with the hydroxides of Fe and Mn in an aqueous medium under certain conditions (Smedley and Kinniburgh, 2002) Different forms of As have significant impacts on the toxicity and treatment efficiency of water purifying systems If the less common compounds of As are excluded from our consideration, the most toxic As compound likely to be encountered is arsine (AsH3), which is more toxic than arsenite (AsO33−); the compound arsenate (AsO43−) is less toxic than arsenite (Mondal et al., 2006; http://www soton.ac.uk/~agh/arsenic.htm) Therefore, the determination of total As in a sample is in itself insufficient to assess its actual environmental 456 T.T.G Luu et al / Environment International 35 (2009) 455–460 risk (Zhang et al., 2002); distinguishing between arsenite and arsenate also assumes importance In addition to its chemical forms, As toxicity depends on the exposure route and dosage to the human recipient Long-term As exposure can cause skin diseases, including hyperkeratosis, blackfoot disease, and epithelioma, as well as myocardial ischemia, liver dysfunction, and several cancers (http://dnrec.state.de.us/dnrec2000/ Divisions/AWM/SIRB/…/New/rms05038.pdf) In general, in order to assess exposure, it is needed to determine how long people are exposed to a chemical; how much of the chemical they are exposed to; whether the exposure is continuous or intermittent; and how people are exposed—through eating, drinking, breathing or skin contact (California Environmental Protection Agency, 2001) The presence of trace elements in groundwater is also an important issue because it affects possible uses of water (Kouras et al., 2007) The accumulation of trace elements in environmental samples (soil, sediment, water, biota, etc.) can cause a potential risk to human health due to the transfer of these elements in aquatic media, their uptake by plants and subsequent introduction into the food chain (Al Rmalli et al., 2005) In recent times, some studies have pointed out the high concentrations of such trace elements as Mn, Pb, Ba, Ni, Co, Sr, Fe, Se, Zn, Cu and Cr in groundwater, which constitute a threat to humans, plants and animals in contact with them (Agusa et al., 2006; Buschmann et al., 2007; Farías et al., 2003; Frisbie et al., 2002) Hence, it is necessary to conduct research on the contaminated situation of groundwater by trace elements The objectives of this study are: (1) to study the magnitude of As and other trace element contamination in groundwater in Kandal Province, Cambodia, (2) to reveal the As species present in the As contaminated groundwater and (3) to assess the risk of cumulative exposure to As in Kandal Province, by application of a formula Materials and methods 2.1 Water samples collection Fifteen tube-well water samples were taken in February, 2007 (a dry season) from Kandal Province (Prek Thom village: Kbal Kaoh commune (PT), Phoum Thom village: Phoum Thom commune (POT), and Chounlork village: Korkifrom commune (CHL)) Samples were collected from tube-wells following this sequence: (1) pumping the tube-well for several minutes; (2) washing out a clean polyethylene bottle with the well water; (3) taking water without filtering, for total As (including total soluble As and particulate As); (4) filtering the water through a 0.45 μm filter, for total soluble As, other trace elements and dissolved organic carbon (DOC); (5) filtering the water through both a 0.45 μm filter and an As speciation cartridge packed with 2.5 g of selective aluminosilicate adsorbent for separating arsenate and arsenite in groundwater samples; (6) immediately storing the samples taken in an ice box During sample collections, a series of in-situ measurements was conducted: pH, electrical conductivity, total dissolved solids (TDS), temperature, redox potential, turbidity, alkalinity, hardness, Fe2+, NH4+, NO2−, NO3−, PO43−, Si, SO42−, and dissolved oxygen (DO) The on-site measurements of both cations and anions were conducted by using a portable spectrophotometer All of the samples except the DOC analysis were on-site acidified with ml concentrated HNO3 (70%) As measured by Meng and Wang, (1998), the average recovery of As (III) in the filtrates by using a cartridge was 98% The cartridge can be used for As speciation in a pH range of 4–9 Another four samples used as controls (PNP) were from the Phnom Penh water supply, taken from water taps in the city using the same sampling procedure sequence as for groundwater 2.2 Water samples analysis As concentrations in the groundwater and water supply samples were determined by Graphite Furnace-Atomic Absorption Spectrometry (GF-AAS; Perkin Elmer 5100 PC, USA) Arsenic standard solutions prepared in 0.2% HNO3 were used to determine the calibration curve The blank solution was the Milli-Q water acidified with HNO3 Interference with the measurement method was prevented by using recommended matrix modifiers for Pd and Mg Standard Reference Material, SRM1640 (NIST) 26.67 ± 0.41 µg/kg of As concentration, was used to check the quality control of the analytical procedures Concentrations of 20 elements (Ag, Al, B, Ba, Cd, Co, Cr, Cu, total iron, Ga, Mn, Mo, Ni, Pb, Rb, Se, Sr, Tl, U and Zn) were determined by inductively coupled plasma mass spectrometry (ICP-MS; Agilent 7500ce, USA) DOC was analyzed using a total organic carbon analyzer Sievers 820 Results and discussion 3.1 General characteristics of groundwater The results of total 17 parameters measured on-site are shown in Table In general, most of the groundwater samples were in a reductive condition with the low redox potential, high ammonium, DOC, PO43− and ferrous concentrations and low nitrate concentrations Most of the parameters which are indicated in the table below measured in the water supply were within the allowed limits for drinking water set by the WHO 3.2 Arsenic contamination in groundwater 3.2.1 Total arsenic concentrations in groundwater Fig 1(a) shows that very high total As concentrations are present in the groundwater in Kandal Province Concentrations of As in the groundwater ranged from 6.64 (in POT village) to 1543 μg/L (in PT village), with average and median concentrations of 552 and 353 μg/L, respectively The total As concentrations in the water supply (PNP) taken from Phnom Penh City ranged from 0.8–2.5 μg/L About 86% of the groundwater samples contained As concentrations exceeding the WHO drinking water guidelines of 10 μg/L In particular, elevated As concentrations were observed in PT village, with four out of five samples having As concentrations higher than 1000 μg/L, while in CHL and POT villages, the average As concentrations were 376 and 213 μg/L, respectively These high concentrations of As may occur because the groundwater has its source in the Upper Mekong Floodplain, an area where As accumulates in the sediments (Mukherjee et al., 2006, Buschmann et al., 2007) These sediments are abundant in hydrated ferric oxides, on whose surface arsenic is sorbed Under reductive conditions, the sorbed arsenic may dissolve because of the activity of micro-organisms Our results are in accordance with the research conducted by Buschmann et al (2007), who reported that elevated arsenic is extremely limited to the Mekong River bank and the alluvium braided by this river PT, POT and CHL villages in our study are located near the Mekong River banks, with average distances from these villages to the Mekong River bank of 2330 m, 2130 m and 4510 m, respectively (Fig 1b) Therefore, a huge Table Average, median and range parameters for the groundwater in the villages of PT, POT, CHL in the Kandal Province and of the water supply (PNP) in Phnom Penh PT village Parameter pH Conductivity TDS Redox Turbidity Alkalinity Hardness Ferrous NH4+ NO2− NO3− PO43− Si SO42− DO DOC POT village CHL village PNP Unit Average Median Range Average Median Range Average Median Range Average Median Range mS/cm g/L mV NTU mg/L as CaCO3 mg/L as CaCO3 mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L 7.2 0.666 0.325 −140.1 13.011 273.6 319.4 0.07 8.945 0.0115 2.16 3.561 30.07 175.9 3.17 4.998 7.2 0.5 0.24 −77.5 7.52 297 232 0.06 10.55 0.008 1.65 3.105 20.85 10.5 2.7 4.86 6.8–7.5 0.48–1.29 0.23–0.64 −449–18 1.355–32.75 182–313 191–662 b 0.02–0.115 b0.025–15.55 0.005–0.026 1–4.45 2.36–5.19 6.15–83.3 1–850 2.1–6.1 4.25–5.76 7.37 0.824 0.406 37.9 11.23 402.8 242.8 0.182 12.31 0.01 1.91 1.302 273 19.9 2.48 5.71 7.25 0.79 0.39 62 6.575 371 188 0.06 12.55 0.0105 1.7 0.75 34.05 6.5 2.3 5.91 7.2–7.6 0.65–1.21 0.32–0.6 − 73–122 1.225–32.8 225–580 123–405 b 0.02–0.475 4.85–23.75 0.004–0.0155 0.25–3.15 b 0.75–2.89 3.35–1260 0.5–71.5 1.1–4.05 3.75–7.96 7.22 0.704 0.345 45.42 10.151 399.4 353.4 0.762 14.82 0.0085 2.79 3.475 53.03 13.4 2.45 5.348 7.2 0.74 0.36 38 4.005 428 358 0.61 16 0.0065 2.6 3.565 70.6 12 5.88 7.05–7.4 0.57–0.835 0.28–0.41 25–89 1.745–27.5 301–497 273–445 0.35–1.43 9–20.6 0.0045–0.018 2.25–3.9 2.95–3.845 7.8–77.75 5.5–22 1.75–4.05 3.54–6.52 7.62 0.176 0.084 312 1.5 55.2 55.8 0.035 0.031 0.0164 0.89 0.138 60.31 16.4 8.28 2.722 7.6 0.2 0.1 325.5 2.035 65 63 0.04 0.025 0.008 0.8 0.125 60.6 16.5 8.75 1.81 7.45–7.75 0.12–0.21 0.06–0.1 203–391 0.26–2.645 32–74 35–72 b 0.02–0.06 b 0.025–0.05 0.0065–0.044 0.7–1.3 Under range 22.1–93.8 14.5–17.5 7–9.1 1.59–4.58 T.T.G Luu et al / Environment International 35 (2009) 455–460 457 Fig Total As concentrations (a) in the groundwater (PT, POT, CHL) and in the water supply (PNP) and (b) the sampling locations of groundwater (PT, POT, CHL) amount of As may be loaded into the groundwater from this river basin, especially under the reductive condition demonstrated by low redox potential, and high concentrations of ammonium, DOC, PO43− and ferrous In addition, the pH ≥ found in most groundwater samples might possibly enhance the mobilization of arsenic at some locations 3.2.2 Arsenic speciation in groundwater Fig shows that the most striking feature of the data was the predominance of As (III) in all of the groundwater samples, with the concentrations of As (III) about to 115 times higher than the concentrations of As (V) (Table 2) The concentrations of As (III) in groundwater varied from (in POT village) to 1334 μg/L (in PT village) with an average concentration of 470 μg/L The predominance of As (III) in groundwater has both geochemical and toxicological implications As geochemical implications, the reasons for very high As (III) may be related to factors including the very low redox potential, the neutral to alkaline pH, high amounts of ammonium, DOC, PO43− and ferrous and low nitrate concentrations These reducing conditions can favor As release by microbial reductive dissolution of metal oxides (Berg et al., 2007, Buschmann et al., 2007) As (III) is more toxic than As (V) in some effects, with respect to chromosome breakage, or to toxicological carcinogenesis In addition, As (III) is more difficult to remove from a drinking water supply than is As (V) (Stephen and Danial, 1999), and this could pose an additional health threat to people living in this area The range of As (III) in the water supply was 0.125–0.2 μg/L and the dominant forms were As (V) and particulate As These results may be related to the high value of redox potential, with the range of 203– 391 mV, associated with an alkaline pH 3.3 Trace elements contamination in groundwater A series of various trace elements including Ag, Al, B, Ba, Cd, Se, Co, Cr, Cu, Fe, Ga, Mn, Mo, Ni, Pb, Rb, Sr, Tl, U and Zn were also measured in the groundwater and in the water supply Among these, concentrations over the WHO drinking water guidelines (here given) were found for Ba (700 μg/L), Mn (400 μg/L), Pb (10 μg/L) (WHO, 2006) in most groundwater samples from three villages in Kandal Province The concentrations in water supply samples taken from Phnom Penh were lower than those in the groundwater for most of the elements Our study reveals that 67% of the groundwater samples have Ba concentrations higher than the WHO drinking water guidelines (700 μg/L) The average and median concentrations of Ba in the groundwater were 1271 and 1281 μg/L, respectively (Fig 3a) Ba exerts toxic effects associated with hypokalemia and electrocardiographic changes (Agusa et al., 2006) In contrast, Ba concentrations in the water supply samples were very low, ranging from 22–28 μg/L Our study also indicates that Mn concentrations in 80% of the groundwater samples were higher than the WHO drinking water guidelines (400 μg/L) The highest Mn concentration (10,930 μg/L ) in the groundwater was found in PT22 The median and average concentrations were 908.3 and 1788 μg/L, respectively, (Fig 3b) The concentrations of Mn in the water supply samples ranged from to 11 μg/L Although Mn is known as an essential element for human survival, high doses of Mn may cause lung embolisms, bronchitis, impotency, hallucinations, forgetfulness and nerve damage, even to the point of parkinsonism (Buschmann et al., 2006; www.lenntech.com/ Periodic-chart-elements/Mn-en.htm) 458 T.T.G Luu et al / Environment International 35 (2009) 455–460 Fig As speciation (As (III), As (V) and particulate As) of the groundwater in the villages of PT (a), POT (b), CHL (c) in the Kandal Province and of the water supply (PNP) in Phnom Penh (d) Concentrations of lead (Pb) in the groundwater ranged from 7.1 to 58.4 μg/L with a median Pb concentration of 18.7 μg/L (Fig 3c) About 86% of these samples contained lead concentrations exceeding WHO drinking water guidelines of 10 μg/L Conversely, the concentrations of Pb in the water supply samples were very low, in the range of 0.1 to 0.3 μg/L There is still no evidence for an essential function of Pb in the human body; it seems it can merely harm after uptake from water and food, such as disruption of or damage to organ systems (www.lenntech.com/Periodic-chartelements/Pb-en.htm) These findings indicate that people in Kandal Province may be overexposed not only to As but also to Ba, Mn and Pb from groundwater Adverse health effects that may manifest in coming years are a serious concern for the local population increase in cumulative As in the human body via the pathway of drinking water The cumulative As ingestion of Kandal Province residents ranged from to 6758 mg (Fig 4) In order to determine the danger to the residents of Kandal Province exposed to As contaminated groundwater, our calculated results were compared with the threshold level for internal cancer caused by chronic As exposure to groundwater for smelter workers, a figure of 6750 mg (Agusa et al., 2006) In this case, there was one sample (PT25) with a cumulative As ingestion of 6758 mg, that is, slightly higher than the threshold level linked to internal cancer There were as well some samples (PT21: 4400 mg, PT23: 5461 mg, PT24: 5554 mg, POT29: 6173 mg) with a cumulative As ingestion close to this threshold for internal cancer by As exposure This poses a potentially serious threat to those living in this area 3.4 Risk assessment of cumulative exposure to arsenic Conclusions Four parameters were used to calculate cumulative As exposure: As level in the groundwater; age of the tube-well (where groundwater was sampled, the period of using groundwater of each household was used for the calculation); annual ingestion rate of groundwater; and daily water consumption These are related by the equation: Cumulative As intake mgị ẳ ẵAs level in groundwater g=Lị ẵAge of well yearsị ẵIngestion rate of groundwater 365days=yearị ẵWater consumption 2L=dayị (Agusa et al., 2006) According to the formula, there is a direct proportion between the As level in the groundwater and cumulative As An increase in the As level in groundwater leads to an The present study revealed groundwater contamination by As, Ba, Mn and Pb in Kandal Province, Cambodia About 86% of groundwater samples contained As concentrations above the WHO drinking water guidelines In addition, As (III) was found as a dominant species Furthermore, 67%, 80% and 86% of the groundwater samples exceeded the WHO drinking water guidelines for Ba, Mn and Pb, respectively One sample (PT25) had a calculated cumulative As ingestion (6758 mg) slightly higher than the threshold level (6750 mg) for internal cancer caused by chronic As exposure from groundwater for Table Ratios of As (III) and As (V) concentrations in the groundwater of the villages of PT, POT, CHL in the Kandal Province and of the water supply (PNP) in Phnom Penh Sample As (III) concentration (μg/L) As (V) concentration (μg/L) As (III) concentration/ As (V) concentration PT21 PT22 PT23 PT24 PT25 POT26 POT27 POT28 POT29 POT30 CHL31 CHL32 CHL33 CHL34 CHL35 PNP2 PNP3 PNP4 PNP5 928.84 4.61 1216.94 991.02 1334.13 61.02 54.19 3.92 719.37 64.64 319.57 192.32 303.88 317.87 533.62 0.13 0.20 0.13 0.13 136.57 1.50 130.20 42.14 41.55 2.61 1.40 0.63 69.85 13.56 2.77 18.09 34.74 21.19 6.19 0.49 0.17 1.25 0.53 6.80 3.06 9.35 23.52 32.11 23.35 38.63 6.27 10.30 4.77 115.38 10.63 8.75 15.00 86.26 0.26 1.19 0.10 0.24 T.T.G Luu et al / Environment International 35 (2009) 455–460 459 Fig Barium (a), manganese (b) and lead (c) concentrations in the groundwater (PT, POT, CHL) and in the 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the groundwater and cumulative As An increase in the As level in groundwater leads to an The present study revealed groundwater contamination by As, Ba, Mn and Pb in Kandal Province, ... manifest in coming years are a serious concern for the local population increase in cumulative As in the human body via the pathway of drinking water The cumulative As ingestion of Kandal Province residents