The Red River Delta in Vietnam is one of the regions whose quaternary aquifers are polluted by arsenic. Chronic toxification by arsenic can cause severe illnesses such as cancer, skin lesions, developmental defects, cardiovascular and neurological diseas-es, and diabetes. In this study, a food processing craft village in the Red River Delta was investigated regarding the potential risk faced by the population due to arsenic. The potential sources of arsenic are the groundwater, the crops grown in the sur-roundings, and animal products from local husbandry. However, the occurrence of arsenic in nature is variable, and its bioavailability and toxicity depend very much on its specification: trivalent compounds are more toxic and often more mobile than pen-tavalent compounds, while inorganic species are generally more toxic than organic ones. Local conditions, such as the redox potential, strongly influence its specification and thus potential bioavailability.
The introduction to this work elucidates the key factors which potentially cause human exposure to arsenic: the geological setting of the study area, land and water use pat-terns, and the current state of research regarding the mobilization, bioavailability and plant uptake of arsenic.
Although the study area is located in a region where the groundwater is known to be moderately contaminated by arsenic, the level of arsenic in the groundwater in the village had not previously been determined. In this study, water use in the village was examined by a survey among the farmers and by water analyses, which are present-ed in the following chapters. Four main water sources (rain, river, tube well and a pub-lic municipal waterworks) are used for the different daily activities; the highest risk to human health was found to be the bore well water, which is pumped from the shallow Holocene aquifer. The water from the bore wells is commonly used for cleaning and washing as well as to feed the animals and for food processing. Products like noodles and rice wine were examined as well as local pork and poultry. Vegetables from the gardens and rice plants from the surrounding paddy fields were sampled and ana-lyzed. All plants were found to have accumulated arsenic, leafy vegetables showing the highest arsenic concentrations.
The results are discussed and compared, and conclusions are drawn in the last part. The reducing conditions in the paddy fields are likely to have a strong influence on arsenic uptake in rice plants and on transport to the aquifer. The installation of a wastewater treatment plant under the research project INHAND, which was funded by the BMBF German Ministry of Education and Research, led to lower arsenic concen-trations in the groundwater.
Soaring industrialization, the growing population, and the consumers’ changing behav-ior will widely affect land and water use and hence the potential mobilization of arse-nic. In order to mitigate further human exposure to arsenic, wastewater needs to be treated and the reducing conditions in the rice fields need to be decreased by means of enhanced cultivation methods.:Abstract III
Zusammenfassung V
Acknowledgements VII
Contents IX
List of abbreviations XIII
List of tables XVII
1 Scope of this work 1
2 Introduction 2
2.1 Geographical and geological setting of the study area 2
2.2 Hydrological situation 5
2.2.1 Surface water 5
2.2.2 Impact of human activities on surface water quality and distribution 6
2.2.3 Hydrogeology 7
2.3 Arsenic occurrence 7
2.3.1 Arsenic toxicity 8
2.3.2 Risk potential of arsenic in diet 10
2.4 Arsenic contamination in the groundwater resources of the Red River Delta 11
2.4.1 Occurrence and origin of arsenic in the Red River Delta 12
2.4.2 Mobilization processes 13
2.4.3 As mobilization in paddy fields 15
2.5 Arsenic occurrence in daily rural activities 16
2.5.1 Arsenic in soil 17
2.5.2 Arsenic in drinking water 19
2.5.3 Phytoaccumulation: Current state of research 20
2.5.4 Bioavailablity 22
2.5.5 Arsenic uptake in rice plants 23
2.5.6 Arsenic in meat and animal products 26
2.5.7 Arsenic uptake in golden apple snails 27
2.5.8 Processing: Wine and noodles 28
2.5.9 Arsenic concentrations in wastewater, activated sludge and digestate 29
2.6 Iron and manganese in the nutrient chain 30
2.7 Land and water use in the Red River Delta 31
2.7.1 Historical and political aspects of rural development in Vietnam 33
2.7.2 Craft villages in the Red River Delta 34
3 Materials and methods 36
3.1 Soil sample analyses 36
3.2 Well sampling 37
3.3 Wastewater and sludge analyses 37
3.4 Food analyses 38
3.5 Site visit and field observations 39
3.6 Questionnaire 39
4 Results 40
4.1 Soil samples 40
4.1.1 Total arsenic and total heavy metal concentrations 40
4.1.2 Sequential fractionation procedure 41
4.2 Arsenic in the water cycle in Dai Lam 43
4.2.1 Groundwater analyses 43
4.2.2 Water use in Dai Lam 47
4.2.3 Wastewater in Dai Lam 50
4.3 Arsenic in sewage sludge 51
4.4 Arsenic in manure samples 52
4.5 Arsenic in food samples 52
4.5.1 Rice 52
4.5.2 Arsenic in leaf vegetables 53
4.5.3 Arsenic in poultry products 56
4.5.4 Arsenic in pork samples 57
4.5.5 Arsenic in snails 57
4.6 Economic and demographic development potential 58
5 Discussion 61
5.1 Soil samples 61
5.2 Groundwater samples 62
5.2.1 High arsenic concentrations 62
5.2.2 Strong temporal and spatial variation 63
5.2.3 Weak correlation between measured parameters 69
5.3 Wastewater and sewage sludge 70
5.4 Pig manure 71
5.5 Daily exposure to As from dietary intake 71
5.6 Effects of land and water use on water quality and public health 76
5.7 Against the background of the transition economy 77
6 Conclusion 80
7 Perspectives (further work) 85
8 References 86
9 Annex 110
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:29429 |
| Date | 21 April 2016 |
| Creators | Hahn, Celia |
| Contributors | Werner, Peter Walter, Dornack, Christina, Frimmel, Fritz H., Technische Universität Dresden |
| Publisher | Eigenverlag des Forums für Abfallwirtschaft und Altlasten e.V. |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | urn:nbn:de:bsz:14-qucosa2-352314, 2986529-3, qucosa:36226 |
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