Abstract
Fractures and fracture networks are key conduits for migration of hydrothermal fluids, water and contaminants in groundwater systems Modeling is widely used to understand the environmental risk associated with migration of pollutant for different hydrogeological conditions. In this paper, we proposed a conceptual and mathematical model of flow and transport phenomena in fractured rock systems, and applied in a arsenic contaminate site as a case study. The groundwater flow model and arsenic migration model in fissure-matrix dual system were established. The results show that the velocity of groundwater is positively correlated with inlet pressure, but not with the porosity of the fracture. When the velocity of groundwater is relatively high, arsenic is transported along with the current in a finger-like manner. The distribution of arsenic concentration on the fracture surface is heterogeneous and the phenomenon of diffusion from the fracture to the matrix is not obvious. Indeed, when the velocity of groundwater is relatively small, the arsenic moves forward slowly, the concentration distribution on the crack surface is relatively uniform, and the diffusion phenomenon from the crack to the matrix is more significant.
Highlights
Fractured carbonate aquifers, which are subjected to different degrees of karstification, underlie a land area covering ~ 15% of the earth’s surface and supply ~ 25% of the world’s population with drinking water [1]
In the 1930s, native high-arsenic groundwater and its health risks were discovered in Canada [4], New Zealand [5] and Taiwan [6]
As for the migration rule of arsenic in groundwater, some studies considered that iron/manganese oxides, organic matter, and REDOX conditions are the main factors affecting the migration and transformation of arsenic in water bodies [10,11,12,13]
Summary
Fractured carbonate aquifers, which are subjected to different degrees of karstification, underlie a land area covering ~ 15% of the earth’s surface and supply ~ 25% of the world’s population with drinking water [1]. Arsenic pollution in groundwater is one of the hot environmental issues around the world [2, 3]. In the 1930s, native high-arsenic groundwater and its health risks were discovered in Canada [4], New Zealand [5] and Taiwan [6]. More than 70 countries around the world have discovered native high-arsenic groundwater. About 137 million people in the world drink groundwater within arsenic concentration exceeding 10 μgL-1, including 15 million in China [7]. Some researchers have established different risk assessment models to evaluate the health risks of arsenic pollution in groundwater [8, 9].
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