tailieunhanh - NATURAL ARSENIC IN GROUNDWATER: OCCURRENCE, REMEDIATION AND MANAGEMENT - CHAPTER 20

Nghiên cứu này được dựa trên khái niệm thiếu oxy hòa tan (DO) bằng hoặc dưới mực nước ngầm và khai thác nước (Q) qua giếng thủy lợi nông tại một tỷ lệ lớn hơn tỷ lệ nạp tầng nước ngầm là nguyên nhân chính của việc phát hành asen trong nước ngầm của Bangladesh. Nghiên cứu này xác định các quá trình hydrogeochemical liên quan đến tình trạng thiếu DO mà cuối cùng tạo ra nồng độ asen cao và di chuyển của họ vào hệ thống nước ngầm. | Natural Arsenic in Groundwater Occurrence Remediation and Management -Bundschuh Bhattacharya and Chandrasekharam eds 2005 Taylor Francis Group London ISBN 04 1536 700 X The impact of low dissolved oxygen in recharge water on arsenic pollution in groundwater of Bangladesh Md. Nazrul Islam Department of Civil Engineering University ofToronto Toronto Canada . Von Bernuth Department of Biosystems Engineering Michigan State University East Lansing Michigan USA ABSTRACT This study is based on the concept that lack of dissolved oxygen DO at or below the water table and water extraction Q through shallow irrigation wells at a rate greater than the aquifer recharge rate are the main causes of arsenic release in the groundwater of Bangladesh. This study identified the hydrogeochemical processes related to shortage of DO that eventually produce high arsenic concentrations and their migration into the groundwater systems. The existing theories of arsenic release by oxidation and reduction in the context of dissolved oxygen shortage in recharging groundwater were studied. Both numerical and thermodynamic analyses were used to demonstrate how oxidation theory of arsenic release is inadequate to explain the release of arsenic into the groundwater of Bangladesh. This study quantified the amount of dissolved oxygen level in deeper layers of the aquifer and their relation to the variations in redox potential values and arsenic release processes. It also analyzed groundwater velocity and flow patterns to establish a link between dissolved oxygen shortage and arsenic release into the groundwater. On the basis of the findings it was concluded that shortage of dissolved oxygen in recharging water is the most likely the root cause of arsenic occurrence in Bangladesh groundwater. 1 INTRODUCTION The arsenic contamination problem in Bangladesh groundwater is most likely to be associated with shortage of dissolved oxygen in recharge water at or below the water table. The presence or .