Preliminary Water Quality Results for the Erdenet - Khangal River near Erdenet Copper Molybdenum Mine in North Central Mongolia

* Charles Jason Tinant, Oglala Lakota College, USA Bruce Berdanier, South Dakota State University, USA

Don Belile, Oglala Lakota College, USA Devon Wilford, Oglala Lakota College, USA Helene Gaddie, Oglala Lakota College, USA

M.R. Hansen, South Dakota School of Mines and Technology, USA * Corresponding Author, 490 Piya Wiconi Road – Kyle, South Dakota

605-721-1435 (USA) charlesjasontinant@gmail.com

Abstract Water quality was sampled in 2008 at six locations in north central Mongolia along the Erdenet- Khangal River. Water samples were taken at the outfall of the Erdenet mine tailings pond, in the Erdenet mine filtration pond, in the wetlands below the Erdenet mine filtration pond, and in two shallow alluvial wells located topographically above the Khangal River. The water samples were tested for metals using an atomic absorption (AA) graphite furnace. Arsenic was identified as a parameter of concern with sample values ranging from 6.0 to 13.8 ug/L in ground water and 3.7 to 24.6 ug/L in surface water. The World Health Organization standard for arsenic in drinking water is 10 ug/L. The flow rate of the Khangal River during sampling ranged from 0.06 to 0.37 m3/sec. Multiplying flow rate and concentration at each site yielded arsenic loading rates ranging from 40 to 470 g/day. The results suggest that naturally high levels of arsenic occur in ground water, however, arsenic levels in the stream are elevated by an industrial point source. Therefore, focused water quality testing should be conducted to identify specific arsenic sources.

Introduction As global water resources become increasingly scarce, heavy metals contamination of drinking water is becoming an issue of global concern. Some important research areas in the coming decades are characterization of the airborne deposition of heavy metals, bio-indicators of heavy metal contamination, inexpensive and efficient methods to encapsulate heavy metals, and contaminated water treatment. Because water quality and water quantity issues are globally important, developing and developed nations need to cooperate within a globally engaged science and engineering research environment. In June 2008, students and professors from the United States, Jordan, and Mongolia collected water and sediment samples above and below the Erdenet copper-molybdenum mine. The project had two main goals: 1) characterize the impact of contaminant sources on water quality in the Erdenet area, and 2) develop an international multi-tiered network of scientists, engineers, and undergraduate and graduate students to cooperatively solve environmental problems through research collaboration (Berdanier and Tinant, 2008). This paper discusses the water quality results of our study.

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Study Area The Erdenet copper-molybdenum mine is located in the Bulgan Aimag of northern Mongolia, about 350 kilometers northwest of the capital of Ulaanbaatar. The open pit began in 1978 as a joint venture between the former USSR and Mongolia. The ore body of the mine is a porphyry copper-molybdenum intrusion that annually produces about 20 Mt of ore (Munkhtsengel, 2007). The Erdenet copper-molybdenum mine is located in the Erdenet-Khangal River valley. The valley consists of Quaternary aged alluvium overlying a complex geology consisting of the Permian aged Selenge complex granodorite-granite and gabro-diorite suites, Permian-aged gneiss and volcanics, Triassic-aged volcanic and subvolcanic intrusives, and early-Mesozoic porphyry association intrusive rocks (Koval et al., 1985; Watanabe and Stein, 2000 from Munkhtsengal, 2007). Surface water flow in the Erdenet-Khangal River valley consists of the Erdenet, Gavelin, Goril, Zaluu, and Zun rivers, which form the Khangal River. The Khangal River then flows into the Orhan River (Batsukh, 2008; Oyuntungalag, 2008). The Erdenet-Khangal river water and sediment were sampled at six locations in June 2008. The “white sands” mine tailings, filter treatment pond, and the wetlands below the filter treatment pond were sampled for water and sediment. The mine tailings dam, filter treatment pond, and wetlands are located within the Zun River valley (Batsukh, 2008), which flows into the Erdenet-Khangal River. Grab samples of ground water from a well and a spring from the adjacent watershed and Erdenet tap water also were collected. Sampling locations shown below (figure 1) were located near bridges for ease of access. The first sampling location along the river (SS-1.0) was located at the first access point (bridge) with perennial stream flow. The second sampling location along the river (SS-2.0) was located immediately downgradient of the Erdenet Coal-Electric Plant detention ponds. The third sampling location (SS-2.3) along the river was located upgradient of the municipal waste facility and the Erdenet mine processing facility. The fourth sampling location along the river was located immediately downgradient of the municipal waste facility and the Erdenet Mine processing facility. The fifth sampling location along the river was located immediately downgradient of the Erdenet wastewater treatment plant and the pipeline carrying “white sands” tailings to the tailings dam. The final site along the river was located below the confluence of the Zun and Erdenet-Khangal rivers.

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Figure 1. Google Maps image showing the project study area Methods Standard methods for water sampling and analysis were applied following the methods in Standard Methods for Water and Wastewater Analysis and United States Environmental Agency Standard Methods. The stream was assessed for physical parameters following Bevingder (1995) and Rosgen (1996). Stream flow, total dissolved solids (TDS) and pH were measured at each of the sampling locations. Water samples were fixed with nitric acid. Water samples were analyzed for chromium (Cr), copper (Cu), lead (Pb), cadmium (Cd), silver (Ag), and arsenic (As) using atomic absorption (AA) graphite furnace. Leachable metals from sediment samples were digested following EPA method 3050 and were analyzed for arsenic. The mass-loading rate for arsenic was calculated by multiplying flow rate by the concentration.

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Results and Discussion Table 1. Table showing results of water quality sampling.

Tap

WaterSS1.0

SS2.0

SS2.3

SS2.6

SS3.0

WhiteSands

FilterPonds

ZunRiverWetlands

SS5.0

GW1.0

GW2.0

pHnodata 8.4 8.4 8.45 8.25 8.15

nodata 10.5 8.3 8.2

nodata

nodata

TDS(mg/L)

nodata 391 449 617 550

nodata

nodata 1018 780

nodata

nodata

nodata

FlowRate(m3/s) N/A 0.06 0.21 0.21 0.22 0.23

nodata

nodata nodata 0.37 N/A N/A

*Bolditemsarelinearlyinterpolated

Concentration(ug/L) Cr <LOD <LOD <LOD <LOD 3.81 <LOD <LOD <LOD <LOD 1.12 1.41 0.5Cu 29.56 1.54 4.61 6.12 7.08 10.78 38.48 0.19 4.33 12.06 3.27 11Pb <LOD <LOD <LOD <LOD 3.81 <LOD <LOD <LOD <LOD 1.12 1.41 0.75Cd 5.79 0.04 0.02 0.01 0.00 1.69 0.01 0.003 0.017 <LOD 0.51 0.3

Ag <LOD <LOD <LOD <LOD <LOD <LOD <LOD <LOD <LOD <LOD<LOD <LOD

As <LOD 7.29 4.14 3.73 24.46 12.93 60.62 5 8.58 8.95 6 13.88*BolditemsareaboveWorldHeathOrganization(WHO)DrinkingWaterQualityStandards

Asinsediment(mg/kg) N/A 2.2 2.3 5.1 2.3 2.2 10.9 15 2.2 3.1 N/A N/A*Bolditemistheupperdetectionlimitformethod MassFlow(g/day)

As N/A 39.57 73.65 69 465 253nodata

nodata nodata 286 N/A N/A

Drinking water quality standards for Mongolia follow World Health Organization (WHO) Drinking Water Quality Standards (Oyuntungalag, 2008). Heavy metals (Cr, Cu, Pb, Cd, As) for stream and ground water samples were not detected in levels exceeding WHO Drinking Water Quality Standards. Cadmium (Cd) in the tap water sample slightly exceeded the WHO Drinking Water Quality standard of 5.0 ug/L. The most likely source for the Cd exceedance is from metal pipes transporting water from the Selenge River source to the tap at the Erdenet Inn where the water sample was taken.

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Arsenic concentrations in one of the ground water samples exceeded WHO Standards for Drinking Water Quality (figures 2 and 4; table 1). The WHO Drinking Water Standard for arsenic is 10 ug/L. The arsenic concentration of the upgradient ground water sample was 6.0 ug/L. The arsenic concentration at the lower spring was 13.0 ug/L. This result suggests naturally high levels of arsenic in ground water. Upwelling ground water through arsenopyrite rich rocks may be the source for arsenic in ground water (Oyuntungalag, 2009).

Figure 2. Map showing arsenic concentrations and loadings in Khangal River and ground water.

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Arsenic concentrations in stream water samples exceeded WHO Standards for Drinking Water Quality (figures 2 – 4; table 1). The arsenic concentration at the sampling location below the municipal waste facility and the Erdenet Mine processing facility is 24.46 ug/L, which is over twice the drinking water standard. Arsenic concentration below SS – 2.6 declines by almost 50% at SS 3.0 which had an arsenic concentration of 12.93 ug/L. The arsenic concentration in the stream (8.95 ug/L) was below the water quality standard at the furthest downstream sampling location (SS-5.0). River sediments constitute the most important sink for metals and other pollutants (Adams, et. al., 1992, referenced by Munkhtsengal, 2007). The mass loading of the Erdenet- Khangal River suggests that a point source loading of arsenic is responsible for the arsenic exceedances downstream of the municipal waste facility and the Erdenet mine processing facility. Furthermore, a non-point source loading from the wetlands slightly elevates arsenic levels in the Khangal River below the tailings complex (figures 2 and 3). The arsenic loading rate at sampling location SS-2.6 (465 g/day), located below the municipal waste facility and the Erdenet Mine processing facility, was two orders of magnitude greater than the arsenic loading for sampling station SS-2.3 (69 g/day) located above these possible pollution sources. The mass loading of sampling location SS-3.0 (253 g/day), located below the municipal waste facility and the Erdenet Mine processing facility, declines by almost 50%. The arsenic loading for the downstream sampling location SS-5.0 265 )g/day) is only slightly greater than the loading rate for the sampling location SS-3.0. The mine tailings complex (White Sands, Filter Ponds, Wetlands) is likely loading arsenic into the stream at roughly the same rate as arsenic is being adsorbed onto stream sediments between sampling locations SS-3.0 and SS-5.0. Figure 3. Graph showing arsenic concentrations and loadings in Erdenet area

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Figure 4 – Close-up Google Maps image showing Khangal point source loading for arsenic Conclusions The results of the project suggest the following conclusions: 1) high pH of surface water limits the vulnerability of the Erdenet-Khangal River to heavy metals contamination, 2) arsenic is naturally occurring in ground water in the Erdenet region, 3) arsenic concentrations in the Erdenet-Khangal River exceeding the WHO water quality standard are likely caused by an anthropogenic source, 4) the anthropogenic source is likely either the Erdenet municipal waste facility or the Erdenet Mine processing facility, and 5) future water quality testing should be conducted to identify the specific arsenic source.

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