The controlling of paleo-riverbed migration on Arsenic mobilization in groundwater in the Red River Delta, Vietnam

Abstract

In the Red River Delta, the concentrations of Arsenic in groundwater of alluvial dominated systems are very high, exceeding the WHO’s permissible. The correlation between the Arsenic concentrations in groundwater and the age of Holocene sediment as a key controlling groundwater Arsenic concentration in the Red River delta has been investigated. The evolution of sediments in the Holocene is closely related to paleo-riverbed migration in the past. A combination of methods is implemented including remote sensing, multi-electrode profiling (MEP), gamma-logging, drilling, soil sample and groundwater modeling. The resul has identified the shape, sediment compositions and location of the six paleo-riverbed periods. The age of the paleo-riverbed is determined by drilling, soil sampling and optically stimulated luminescence (OSL) in the laboratory. The oldest sediments is 5.9±0.4 ka BP in Phung Thuong near the mountain, the youngest one is from 0.4÷0.6 ka BP in H-transect near the Red River and the rest of the other is around 3.5 ka BP. The modeling results by using MODFLOW and MT3D show that the dynamics of paleo-riverbeds controlling Arsenic mobilization in groundwater in the Red River Delta. When the river moved to another position, the current river position at that time was filled with younger sediments and became paleo-riverbed formation with reducing conditions, Arsenic content which was adsorbed in the previous stage then released into groundwater. Therefore, Arsenic concentration in groundwater of young Holocene sediments is higher than in older ones which elucidates that paleo-riverbed migration controls on Arsenic mobilization in groundwater in the study area.

Applying an Analytic Hierarchy Process and a Geographic Information System for Assessment of Land Subsidence Risk Due to Drought: A Case Study in Ca Mau Peninsula, Vietnam

“…The landslide risk level index was calculated on the GIS platform by synthesizing component factors and weighting those factors. Trung et al [20] used the method of integrating the GIS and the AHP hierarchical model to build a zoning map of the level of arsenic pollution in groundwater. Hao et al [21] applied AHP methods and a GIS to evaluate land suitability for paddy rice crops in Quang Xuong district, Thanh Hoa province.…”

“…An overview of domestic and foreign studies and research areas shows that the combination of the AHP method with GIS analysis and assessment technology has been very effective in identifying and assessing the risk of subsidence in some areas in Vietnam excluding the Ca Mau Peninsula [19,20]. There have been many studies using modeling combined with RS to evaluate the impact of subsidence due to lowering groundwater levels [22][23][24][25][26][27][28][29]32,33].…”

Predictive geospatial model for arsenic accumulation in Holocene aquifers based on interactions of oxbow-lake biogeochemistry and alluvial geomorphology

“…Studies with focus on the abundance of arsenic concentration in the Holocene lithostratigraphy and the drop of concentrations in underlying Pleistocene stratigraphy have yielded a generalized perspective of stratigraphic control on arsenic distribution in shallow aquifers of alluvial floodbasins (e.g., Bhattacharya et al, 2006;Berg et al, 2007;Aziz et al, 2008;Guo et al, 2008;Van Geen et al, 2008, 2013Weinman et al, 2008;Hoque et al, 2009Hoque et al, , 2014McArthur et al, 2011;Robinson et al, 2011;Postma et al, 2012Postma et al, , 2016Sahu and Saha, 2015;Stopelli et al, 2020;Wallis et al, 2020;Kazmierczak et al, 2022). Mukherjee et al (2010), Donselaar et al (2017), Cao et al (2018), Trung et al (2020), Das and Mondal (2021), Ghosh et al (2021), and Kumar et al (2021a) have taken the concept of lithostratigraphic control one step further by relating porosity and permeability anisotropy in genetically-related, juxtaposed (1) clayey floodplain and oxbow-lake, and…”