Evaluation of Urban Groundwater Quality at Ulaanbaatar, Mongolia Using Hydrochemical and Environmental Isotope Data
- 주제(키워드) Ulaanbaatar groundwater , Mongolia , Isotope , hydrogeochemistry
- 발행기관 고려대학교 대학원
- 지도교수 윤성택
- 발행년도 2017
- 학위수여년월 2017. 2
- 학위구분 박사
- 학과 대학원 지구환경과학과
- 원문페이지 134 p
- 실제URI http://www.dcollection.net/handler/korea/000000073164
- 본문언어 영어
- 제출원본 000045897590
초록/요약
In the Ulaanbaatar (UB) city, the capital of Mongolia, where nearly half of the nation’s population (currently, ~1.3 million in 2014) live with such particularly seriously environmental problems. Moreover the urbanization of this country has intensified the water scarcity for drinking and sanitation. The water supply in UB city has depended on groundwater bodies which accounts for about 80 % of total water consumption at a centralized public water system in alluvial aquifers of Tuul river basin. We reported the first time of the results of hydrochemical and isotopic assessment for the UB groundwater; our major objectives are to assess the status of groundwater quality in the relation with hydrogeological/geochemical processes and anthropogenic factors such as the urban land uses. Specifically, this study identified the nitrate sources and the recharge process for the UB groundwater by using the nitrate isotopes (δ15N and δ18O of NO3-) and the water isotopes (D and 18O of H2O). In this paper, we divided groundwater samples into two parts including anthropogenic and natural groups (Group I and Group II) based on the combination of NO3− concentrations and δ15N values of NO3−, which were significantly different by threshold levels of 10 mg/L NO3− and 10 ‰ δ15N. The other ions were also different between two groups; most concentrations in the anthropogenic groups were higher than those of natural group. There was also an inter-relationship between nitrate and water isotopes (D and 18O of H2O) of groundwater. This may suggest that the nitrate enrichment was influenced by high evaporation under semi-arid condition of this area during groundwater recharge. The nitrate in all samples, thus, can be mixtures among the remaining sources: soil organic matter, manures, and sewage effluents. The severe nitrate pollution in groundwater of UB city is mainly due to the leakage of sewage effluents including pit-latrine infiltration in ger areas, while the groundwater nitrate less impacted by the anthropogenic sources is originated from soil organic matter, and/or animal and livestock manures in grassland and forest areas. Additionally, we suggest a groundwater quality index (GWQI) specified in UB city for further monitoring and managing groundwater quality and delineating the current vulnerable zone to the significant nitrate pollution in groundwater. These findings have implications of current policies which promote latrine construction, especially in peri-urban areas (ger area) with high population density. And a new way is necessary to be searched to improve the environmental sanitation. Public enlightenment campaign on the effect of contaminated water and the danger of sitting groundwater wells closed to pit latrines were embarked upon the government.
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ABSTRACT i
CONTENTS iii
List of Tables vii
List of Figures viii
Part I
Assessment of groundwater nitrate pollution in Ulaanbaatar (UB) city of Mongolia using hydrochemical and environmental isotope data
ABSTRACT 2
1. Introduction 4
2. Materials and Methods 8
2.1. Study area 8
2.2. Sampling and analysis 12
2.3. Statistical methods 15
2.3.1. Compositional data analysis and log-ratio transformation 15
2.3.2. Principal component analysis (PCA) 18
3. Results and Discussion 21
3.1. The water isotopic values (δD and δ18O) 21
3.2. Groundwater hydrochemistry 33
3.3. The δ 15N and δ18O of NO3-: nitrate pollution sources 37
3.4. Principal component analysis: Integrating isotopic and hydrochemical data 45
4. Conclusions 50
References 52
Part II
Urban groundwater quality in Ulaanbaatar, Mongolia and other cities in the world: Assessment of land use controls using hydrochemical and sulfur isotope data
ABSTRACT 67
1. Introduction 69
2. Materials and Methods 72
2.1. Study area 72
2.2. Sampling and analysis 78
2.3. Data collection 81
3. Results and Discussion 82
3.1. Hydrochemistry The relationship between groundwater hydrochemistry and land use 82
3.2. Carbon isotopes: origins of dissolved inorganic carbon: 91
3.3. Sulfur isotopes: origins of dissolved sulfate as a potential indicator of urban GW pollution 95
3.4. Comparison of hydrochemistry with urban groundwaters in Eurasian megacities 101
4. Conclusions 108
References 109
Acknowledgements 118
