Spatial and seasonal variations ofwater and salt movement in the vadose zone at salt-impacted sites

Abstract

Oilfield-produced brine is a major source of salt contamination in soil and groundwater. Salt transport in the upper soil layers is controlled by the atmospheric interactions via infiltration of meteoritic water. In lower layers, it is controlled by fluctuations in the groundwater table, which are also linked to atmospheric interactions via groundwater recharge. Therefore, climate is an important factor in the movement of contaminants in the unsaturated zone. A one-dimensional variably saturated flow and transport model with soil atmospheric boundary conditions was used to estimate the effect of climate type and soil texture on soil water and salt dynamics in variably saturated soils. Numerical simulations were run with Hydrus-1D, using daily climate data. Simulations were run for nine-year climate datasets for different ecoclimatic locations in Alberta, Canada. Results indicated that coarse-grained materials are good evaporation barriers, resulting in water gain conditions at the ground surface, irrespective of the climate type. However, the quantity of water gain and associated advective fluxes are a function of climate. Results also indicated that flow and transport in fine-textured soils is more dependent on the climate type. For fine-grained soils in arid climatic conditions, net water loss at the ground surface and upward migration of salt can be expected. For wetter climates, the upward migration of salt is less probable.