砷的發生對越南湄公三角洲之威脅

Threat of Arsenic Occurrence in the Vietnamese Mekong Delta

高溶解砷在地層孔隙水中移動已被世界廣泛報導，地下水中高濃度的砷對人類健康及地下水利用造成威脅。全球已有許多文獻針對含砷的地下水進行研究，但近年來，越南紅河及湄公河三角洲砷的發生才引起科學家的注意。本文主要目的在於回顧亞洲孟加拉及越南沖積扇平原砷的汙染，接著經由在越南湄公三角洲安江省安富縣的近期調查，於2014年乾濕季時收集36個地下水樣本及2個沉積物核心，說明湄公三角洲砷發生的證據。調查結果顯示，研究區域內砷的濃度介於208 到1,523μg/L之間，遠高於世界衛生組織（WHO）及越南飲用水的標準（10μg/L）。此外，乾季時地下水砷的濃度比濕季時更高，且砷的濃度隨著沉積物深度增加而增加，在25公尺深時高達201ppm。

The occurrence of high dissolved Arsenic (As) levels mobilized from geogene sources in pore water has been reported worldwide. High elevations of Arsenic concentration in groundwater have posed threats to human's health and implication for groundwater use. Previous studies on As-rich groundwater around the world have been in the literature. Particularly, Arsenic occurrence in the Red River and Mekong River deltas of Vietnam has recently drawn much attention from scientists. The purpose of this paper is to review Arsenic contamination in alluvial plains of Asian deltas of Bangladesh and Vietnam. Further, an additional evidence of Arsenic occurrence in the Mekong Delta region will be reported through our recent survey in An Phu district, An Giang province of the Vietnamese Mekong Delta. Thirty six (36) groundwater samples and two (02) cores of sediment were collected in the rainy and dry seasons of 2014. The investigated results show that Arsenic concentration in groundwater resources in the study area is much higher than the WHO and Vietnam drinking water standard (10μg/L), ranging from 208 to 1,523μg/L. In addition, the arsenic concentration in groundwater in the dry season tends to be higher than in the rainy season. Arsenic concentration in sediment cores increases with depths, reaching to 210 ppm at 25m depth.