Arie Nadler

Chemical reactions of sea water with rocks and freshwater: Experimental and field observations on brackish waters in Israel

Abstract Four major processes are observed to take place in the coastal aquifer of Israel, detectable even in the short times of water contact with the carbonate-containing host rocks. Three are chemical reactions, Ca2+-Mg2+ exchange, Na+-Ca2+ or Na+-Mg2+ base exchange, SO2−4 reduction and the fourth is dilution by freshwater. These reactions and their effects on the chemical composition of the waters were demonstrated experimentally. The range of chemical changes observed in the laboratory experiments overlap the range of the studied natural waters. This indicates that simulation of geologically long-term rock-water interaction could be achieved in laboratory experiments even at low temperatures.

Effect of soil structure on bulk soil electrical conductivity (ECa) using the TDR and 4P techniques

Bulk soil electrical conductivity (ECa) was measured in one weak-structured and three naturally well-structured soils under undisturbed conditions and after structure disruption. Two structure-disruption procedures of increasing severity were used. Bulk soil electrical conductivity was measured by two independent techniques, electromagnetic induction and four-electrode probe, and showed a close similarity between undisturbed and disturbed samples as long as soils were repacked to the original field density. The minimal effect of structure disruption on bulk soil electrical conductivity as determined by electromagnetic induction was expected because measurement by this technique is based on an electromagnetic pulse signal interacting with the electric field of the ions in the soil solution and not on direct contact. These findings may reduce time, inconvenience, and expense in obtaining calibration curves for bulk soil–soil solution electrical conductivity needed for determining soil salinity.

Trends In Structure, Plant Growth, And Microorganism Interrelations In The Soil

Increased demand for food production, extensive agricultural cultivation, and destructive processes occurring naturally in soil (erosion, weathering) will necessitate use of lower quality soils, thus promoting the use of soil conditioners. In order to draw attention to the unforseen and possibly hazardous effects of soil conditioners along with their positive effects, a laboratory experiment with two anionic polyacrilamide (PAM) polymers was conducted at three application levels and on three soil types. It was found that these PAMs harmed, improved, or barely affected sandy, loamy, and clay soils, respectively. The applied PAMs drastically affected soil physical properties, e.g., aggregates size distribution and water retention, thus affecting plant production above and below the soil surface. Only a semi-systematic response of the nematodes, bacteria, fungi, and actynomicetes population to the above treatments was found.

A Scanning Electron Microscopy Study of Water in Soil

Cold stage Scanning Electron Microscopy (SEM) with a rapid cooling technique makes it possible to investigate the water phase within unsaturated porous media. It is thought that this technique preserves the main features of the micromorphology of the water menisci as it exists in the liquid phase in soils. Saddle-shaped elements, as well as pendular rings of water, were observed with concave and convex curvatures of the water-air interface. The hydraulic conductivity of an unsaturated soil may be inferred from SEM photographs. Observations of isolated water menisci indicate the existence of an immobile water domain. The surface geometry of the water menisci was analyzed quantitatively and surface tension and capillary pressure were determined.

PAM application techniques and mobility in soil

High application rates (50–200 mg Kg−1 soil) and strong adsorption to soil aggregates severely limit polyacrylamide (PAM) application as a soil conditioner below the top soil. Limited penetration, 0 to 20 cm, was obtained upon introducing tritium-labeled PAM-2J into a clayey and sandy loam, respectively. This low penetration rate is related to the adsorption of the polymer to the surface of soil particles. This study tested the potential effect of modifying PAM application management by lowering the viscosity of the applied PAM solution, thus increasing the efficiency of polymer subsurface penetration under reduced application rates. One way of enhancing PAM penetrability may be a temporary reduction in adsorption. A significant reduction (up to five fold) in the viscosity of polymer solution flowing through narrow capillaries, caused by the addition of NaCl or CaCl2 to the solution, was observed in the laboratory. The application of PAM affected soil structure by redistributing soil pore sizes, as indicated by changes in water content under different pressures

Measuring transient solute transport through the vadoze zone using time domain reflectometry

Time domain reflectometry (TDR) was used to monitor the transport of conservative tracers in the field under transient water flow in a controlled experiment under a kiwifruit vine. A mixed pulse of chloride and bromide was applied to the soil surface of a 16 m2 plot that had been isolated from the surrounding orchard soil. The movement of this solute pulse was monitored by TDR. A total of 63 TDR probes were installed into the plot for daily measurements of both the volumetric water content (θ) and the bulk soil electrical conductivity (σa). These TDR-measured σa were converted into pore water electrical conductivities (σw) and solute concentrations using various θ–σa–σw relationships that were established in the laboratory on repacked soil. The depth-wise field TDR measurements were compared with destructive measurement of the solute concentrations at the end of the experiment. These results were also compared with predictions using a deterministic model of water and solute transport based on Richards’ equation, and the convection–dispersion equation. TDR was found to give a good indication of the shape of the solute profile with depth, but the concentration of solute was under- or over-estimated by up to 50%, depending on the θ–σa–σw relationships used. Thus TDR can be used to monitor in situ transport of contaminants. However, only rough estimates of the electrical conductivity of the soil solution can so far be obtained by TDR.

Salt Accumulation in the Loessial Sequence in the Be'er Sheva Basin, Israel

Evidence of climatic changes is recorded in the salt content of the surface sediments in arid zones. In wetter periods airborne salts are removed downward by leaching to the groundwater, whereas in drier periods they accumulate. The period of salt accumulation in the loessial sediments of the northern Negev is about 10,000 yr. This period represents the recent aridification phase. The beginning of this stretch of time followed the last humid period in the region. Top paleo soil (calcic horizon) found in the region and dated 12,000 yr B.P. is an indicator of this humid period.

Hydrogeochemistry of continental brackish waters in the southern coastal plain, Israel

Abstract The southern Coastal Plain in Israel incorportates a transitional fringe of the desert in which three different chemical types of groundwater are found: (1) near-surface waters from springs along the Besor River course: (2) shallow- to moderate-depth waters from the slightly westward-dipping Pleistocene coastal aquifer (this aquifer, which consists of sandstone layers of the Kurkar Group, is recharged in the Coastal Plain); and (3) deep waters of the westward-dipping Upper Cretaceous Judea Group carbonates, which are recharged in the mountains in the east. A thick aquiclude of Upper Cretaceous-Tertiary rocks separates the Judea Group aquifer from the overlying coastal aquifer in the southern Coastal Plain. Isotopically light oxygen and depleted deuterium characterize the Judea Group waters, as expected from high-altitude recharge. The isotopic composition of the Coastal Plain waters is variable, but for the most part enriched in 18O and D. Within the southern Coastal Plain aquifer a southern subgroup comprises waters more depleted in heavy isotopes than those of either the northern or eastern subgroups. The Besor waters are isotopically similar to the Judea Group waters, reflecting their origin in the mountain region, and flow through the surficial river gravels and sands. It is suggested that leakage of the Besor waters into the underlying southern Coastal Plain aquifer results in mixing of the two water types. The most prominent chemical feature characterizing the groundwater of the southern Coastal Plain is Na + Cl − > 1 . This Na + Cl − ratio can be maintained only by a continuous input from a non-marine source of Na. The most plausible source of this Na is the dissolution of feldspar derived from the windblown loess deposits which cover the area and/or leaching of trona minerals found in the unsaturated zone, combined with base-exchange processes.

LONG-TERM EFFECTS OF EXTENSIVE GYPSUM AMENDMENT APPLIED WITH SODIC WATER IRRIGATION ON SOIL PROPERTIES AND SOIL SOLUTION CHEMICAL COMPOSITION

Four neighboring locations, two noncultivated and two gypsum-treated, were sampled and analyzed for chemical composition of soil solution. Accumulation of soluble sodium salts in the gypsum-treated loessial soil irrigated with sodic waters was found to be significant after 11 yr of amendment application. A combination of high salinity and low ESP values in the topsoil significantly improved soil hydraulic conductivity and thus enhanced salt input and accumulation. It is predicted that continuation of such management could result in an increase in the concentration of sodium-soluble salts at shallower depths. Under these circumstances, the common ion effect would inhibit gypsum dissolution, thus making additional gypsum application useless.

Kinetics of chemical processes in a carbonate aquifer: A case study of water-rock interaction in the aquifer of western and central Galilee (Israel)☆

The origin of ions in the groundwater of the western and central Galilee (W.C.G.) aquifer is attributed to the dissolution of carbonate rock. Similar chemical compositions have been obtained in laboratory experiments that simulated natural conditions. The field and experimental data indicate the time dependency of ionic composition. A linear correlation was found between the Mg2+ concentration and the aquifer decay time. The kinetic factors of the W.C.G. groundwater were found to resemble other carbonate-aquifer waters, e.g., in Pennsylvania and Virginia.