Sanjit K. Deb

Coupled Liquid Water, Water Vapor, and Heat Transport Simulations in an Unsaturated Zone of a Sandy Loam Field

Information on the coupled liquid water, water vapor, and heat transport under arable field conditions is still limited, particularly for unsaturated soils of semi-arid and arid regions such as New Mexico. HYDRUS-1D model was applied to evaluate various transport mechanisms associated with temporal variations in water content and soil temperature in the unsaturated zone of a sandy loam furrow-irrigated field located at Leyendecker Plant Science Research Center, Las Cruces, New Mexico. The model was calibrated using measured soil water content and soil temperature at 5-, 10-, 20-, and 50-cm depths during a 19-day period (day of the year [DOY] 85 to DOY 103, 2009) and validated for a 31-day period (DOY 104 to DOY 134, 2009). Measured and optimized soil hydraulic and thermal properties and hourly meteorological data were used in model simulations. HYDRUS-1D simulated water contents and soil temperatures correlated well with the measured data at each depth. The total liquid water flux, composed of isothermal and thermal liquid water flux, dominated the soil water movement during early periods after irrigation, whereas the contribution of total water vapor flux, composed of primarily thermal and much smaller isothermal water vapor flux, increased with increasing soil drying. During the soil drying process, the total liquid flux within 15-cm depth eventually changed to water vapor flux near the surface. The upward total liquid and vapor fluxes decreased from 5 cm, indicating that vapor flux was much higher in the layer near the soil surface. The total vapor flux in this unsaturated soil layer was approximately 10.4% of the total liquid and vapor fluxes during the simulation period.

Evaluation of Spatial and Temporal Root Water Uptake Patterns of a Flood-Irrigated Pecan Tree Using the HYDRUS (2D/3D) Model

AbstractQuantitative information about the spatial and temporal patterns of compensatory root water uptake (RWU) in flood-irrigated pecan orchard is limited. We evaluated spatio-temporal compensated and uncompensated RWU patterns of mature pecan tree in a silty clay loam orchard using the HYDRUS (2D/3D) model. HYDRUS (2D/3D) simulations, which agreed well with measured water contents and temperatures at different soil depths and horizontal distances from the tree trunk, suggested that while both compensated and uncompensated RWU varied with soil depth they did not do so laterally because of similar spatial vertical distributions of root length density (RLD) for the under-canopy and the tree canopy dripline locations. Considering compensated RWU resulted in an increase in actual transpiration by 8%, and a decrease in evaporation and drainage by 5% and 50%, respectively, during a growing season. Simulated transpiration and relative transpiration (a ratio between actual and potential transpiration) values we...

Numerical Evaluation of Nitrate Distributions in the Onion Root Zone under Conventional Furrow Fertigation

AbstractHYDRUS (2D/3D) model was used to simulate spatial and temporal distributions of nitrate-nitrogen (NO3-N) within and below the onion root zone under conventional furrow fertigation with the urea-ammonium-nitrate (UAN) liquid fertilizer. The simulated water contents in the furrow irrigated onion field agreed well with the measurements. Simulations produced similar patterns of the measured NO3-N concentration profiles throughout the growing season. NO3-N concentrations remained higher and accumulation of NO3-N was observed within the root zone. Higher NO3-N within the root zone was dependent on the rate of the UAN fertilizer application, quantity of NO3-N removed by root uptake, and NO3-N drainage fluxes below the root zone. Simulations also suggested that NO3-N below the root zone during different growth stages remained much higher than a recommended (for drinking water) standard concentration level (10  mg L−1). This resulted in higher NO3-N drainage fluxes, particularly during the fertigation even...

Mapping of Airborne Particulate Matter Collected Using Two Sensors along US-Mexico Border

Particulate matter (PM) emissions from various sources can have significant effect on human health and environmental quality especially in the Chihuahuan Desert region along US-Mexico border. The objective of the study was to determine the effect of road dust texture and vehicular speed on airborne PM concentrations from different unpaved rural roads using two sampling techniques (DustTrak R , and Sticky-tape). The surface soil textures of unpaved roads varied from silty clay to loam with less than 4% soil moisture content at the time of PM measurement. Sticky tape method in seven experiment sites showed that PM ranged from 0.529 to 3.054 mg m -3 , and DustTrak R measurements showed that PM 2.5 concentration ranged from 1.11 to 37.1 mg m-3 at 1 m height. An exponential relationship was obtained between PM 2.5 by DustTrak R and vehicle speeds with an average slope of -1.619 mg m -3 s -1 . The concentration of PM measured with the Sticky-tape decreased with increasing height of measurement. Both PM measurement techniques provided a good approximation of PM emissions at different vehicles speeds, unpaved roads and position of the instrument above ground level for a variety of unpaved roads. The low cost sticky tape method has the potential to further determine and abiotic (elemental composition) and biotic (fungus) particles in airborne PM.