Publications

Abstract Evaporation from desert sand dunes is studied practically using laboratory columns and mathematically using both analytical and numerical modeling. On outcropping cliffs of the dunes of Buwshar (Oman), microstratification, with layers' thickness of 1–2 mm, was observed. Loose sand and consolidated core samples were collected for laboratory experiments. Imbibition into initially dry sand columns and ensuing steady state evaporation from a capillary fringe above a horizontal water table were studied. The evaporating, negative‐pressure topsoil of the columns was slanted mimicking the cliffs' tilt. In the columns plugged by a thin composite “cap” made by tooling the dune stratified clod, evaporation was impeded and reduced as compared with a homogeneous column. The same outlet evaporating boundaries were considered in HYDRUS‐2D simulations, which showed that 2‐D evaporation from a homogenous column was significantly higher than that from the column with a stratified “plug” at the top. Analytical solution for a 2‐D tension‐saturated homogeneous trapezium was obtained by conformal mappings of pentagon in the physical plane onto a rectangle in the Zhukovsky plain, via a reference plane. This solution combines the versatility of the Toth model, where topology of flow is controlled by an isobaric boundary of a flow tube, and of the Vedernikov model, which assumes a constant hydraulic conductivity in the negative pressure zone of a capillary fringe. Analytical formulae also manifest a decrease of the flow rate with the increase of the angle of tilt of an evaporating isobar.

The present study simulates a predictive alluvium-aquifer's response to a proposed remedial action in the Wadi Suq area, Oman.Contamination due to copper mining and smelting, which was incepted in 1982 and ceased in 1993, has severely impacted the groundwater quality down the gradient.The major concern is the increase of salinity as abundant seawater has been used in mining.Saline plume of an average 35000 mg/l TDS has formed down the gradient from the dam site and spread towards the coast that represents a hydrogeologic boundary.The contaminated aquifer, in which groundwater flows for a path of 34 km to the coast, is composed of unconsolidated alluvium, predominantly gravels and sands in its upper part and of weathered ophiolite in its lower part.The massive fresh ophiolite represents the lower hydrogeologic boundary.Though lithologically different, the aquifer units have been simulated as one unit since the hydraulic properties are more or less similar.Remedial efforts that had been carried out so far were deemed ineffective.The present study proposes a remediation measure by injecting freshwater via wells into the aquifers.Head and concentration values for the year 1993 were used as initial heads/concentrations for the steady flow simulation in which the computed heads/concentrations were matched with the observed ones, whereas transient flow runs were conducted to predict aquifer's response with time.Simulated aquifer response to the injection of freshwater indicates the reduction of TDS with time and the movement of the plume to eventually discharge into the Gulf of Oman.Consequently, the proposed remedial action, though financially challenging, is effectual.

The biogenic organization of widespread valley pine ecosystems on sandy alluvium leads to an increase in soil fertility, productivity, and biodiversity through autogenic successions. Using our own stationary observations and literary data on the productivity of pine forests in Russia, Belarus, and Ukraine, we quantified the mechanism of autogenic forest successions associated with carbon sequestration and the influence of organic matter dynamics on the fertility and water retention of sandy soils. The low rate of organic matter turnover in primary succession leads to the intensive accumulation of thick (6–8 cm) forest litter and the formation of small humus-eluvial horizons with total carbon storage up to 50 Mg/ha. This soil structure retains 2–6 times more water and biophilic elements than in the original sandy alluvium. It is suitable for the settlement of more demanding broadleaf species and nemoral herbs with higher rates of litterfall, its decomposition and humification. As a result, simple pine forests on Arenosols and primitive Sod-podzolic soils are replaced by complex, more productive linden–oak–pine ecosystems on developed Cambisols with thick (up to 30 cm) humus horizons, carbon storage of 80–100 Mg/ha and higher (2–7 times compared to the previous soils) fertility and water-holding capacity. This mechanism is adequately described by a nonlinear process model with a trigger reaction of plant productivity to the storage and quality of soil organic matter, suitable for predicting long-term carbon sequestration during the succession of valley pine forests and the effectiveness of artificial afforestation.