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M.M. Reddy

Publications and source records attributed to M.M. Reddy.

45 records · Page 3Linked to original sources
USGS1987

Description and testing of three moisture sensors for measuring surface wetness on carbonate building stones

Three sensors were tested on building stones exposed to conditions that produce deposition of moisture. A relative humidity probe, a gypsum collected circuit grid, and a limestone block resistor were tested as sensors for determining surface wetness. Sensors were tested under laboratory conditions of constant relative humidity and temperature and also under on-site conditions of variable relative humidity and temperature for 8 weeks at Newcomb, New York. Laboratory tests indicated that relative humidity alone did not cause sensors to become saturated. However, relative humidity did control the rate at which sensors dried after being saturated with distilled water. On-site testing of the relative humidity probe and the gypsum coated circuit grid indicated that they respond to a diurnal wetting and drying cycle; the limestone block resistor only responded to rainfall. (Author 's abstract)

Water-Resources Investigations Report↗
USGS1986

Authors' reply

No abstract available.

Colorado, Idaho, Montana, New Mexico, Utah, Wyomin↗
USGS1986

Use of the chloride ion in determining hydrologic-basin water budgets - A 3-year case study in the San Juan Mountains, Colorado, U.S.A.

Measurement of chloride concentration and water equivalent in precipitation and recharge at a site can be extrapolated to determine available moisture in a nearby basin. This method also may be extrapolated to a basin with similar climatic characteristics if precipitation, vegetation, and topographic data are available. The average accuracy of the total of evaporation, recharge, and runoff (assuming no storage) was about 10% of total precipitation. Soil-moisture measurements indicate the entire 10% error in moisture balance can be attributed to annual changes in storage. Data requirements for the method are considerably less than data requirements for energy-budget methods to determine available moisture. Potential applications of the method to hydrologic problem-solving are: 1. (1) Estimating total available moisture from chloride concentrations in groundwater or surface water or both. 2. (2) Modeling paleoclimate scenarios and evaluating their correctness by comparison with paleo-groundwater chloride concentrations. 3. (3) Providing an independent comparison for water budgets obtained by energy-budget methods. Obviously the method cannot be applied readily to systems with a lithologic source of chloride. Most systems primarily consisting of tuff, intrusive volcanic rock, nonmarine sediments, quartzite, and other metamorphic rocks will be suitable for application of the model.

Colorado↗
USGS1985

Estimates of average major ion concentrations in bulk precipitation at two high-altitude sites near the continental divide in southwestern Colorado

The composition of bulk precipitation from two high-altitude sites, established in 1971 near the Continental Divide in southwestern Colorado, has been monitored by season during the past decade. Calcium ions are the predominant cationic species; sulfate is the major anionic constituent. Bulk precipitation major ion concentrations exhibit log-normal distributions. Representative mean and standard deviation values for the major inorganic ionic species present in bulk precipitation have been calculated for three years of consecutive seasons. Standard deviations for all species, except nitrate, are similar. For two years of data grouped into quarters, deviations from mean values fall well within the plus or minus two standard deviation limit. There does not seem to be a systematic deviation from the mean concentration values, with respect to either ionic component or season.

Colorado↗
USGS1984

Proton and metal ion binding to natural organic polyelectrolytes—I. Studies with synthetic model compounds

A unified physico-chemical model, based on a modified Henderson-Hasselbalch equation, for the analysis of ion complexation reactions involving charged polymeric systems is presented and verified. In this model pH = p K a +p( ΔK a ) + log( α /1 − α ) where K a is the intrinsic acid dissociation constant of the ionizable functional groups on the polymer, ΔK a is the deviation of the intrinsic constant due to electrostatic interaction between the hydrogen ion and the polyanion, and alpha (α) is the polyacid degree of ionization. Using this approach p K a values for repeating acidic units of polyacrylic (PAA) and polymethacrylic (PMA) acids were found to be 4.25 ± 0.03 and 4.8 ± 0.1, respectively. The polyion electrostatic deviation term derived from the potentiometric titration data (i.e. p( ΔK a )) is used to calculate metal ion concentration at the complexation site on the surface of the polyanion. Intrinsic cobalt-polycarboxylate binding constants (7.5 for PAA and 5.6 for PMA), obtained using this procedure, are consistent with the range of published binding constants for cobalt-monomer carboxylate complexes. In two phase systems incorporation of a Donnan membrane potential term allows determination of the intrinsic p K a of a cross-linked PMA gel, p K a = 4.83, in excellent agreement with the value obtained for the linear polyelectrolyte and the monomer. Similarly, the intrinsic stability constant for cobalt ion binding to a PMA-gel ( β CoPMA+ = 11) was found to be in agreement with the linear polyelectrolyte analogue and the published data for cobalt-carboxylate monodentate complexes.

Organic Geochemistry↗
USGS1984

Proton and metal ion binding to natural organic polyelectrolytes—II. Preliminary investigation with a peat and a humic acid

We summarize here experimental studies of proton and metal ion binding to a peat and a humic acid. Data analysis is based on a unified physico-chemical model for reaction of simple ions with polyelectrolytes employing a modified Henderson-Hasselbalch equation. Peat exhibited an apparent intrinsic acid dissociation constant of 10 −4.05 , and an apparent intrinsic metal ion binding constant of: 400 for cadmium ion; 600 for zinc ion; 4000 for copper ion; 20000 for lead ion. A humic acid was found to have an apparent intrinsic proton binding constant of 10 −2.6 . Copper ion binding to this humic acid sample occurred at two types of sites. The first site exhibited reaction characteristics which were independent of solution pH and required the interaction of two ligands on the humic acid matrix to simultaneously complex with each copper ion. The second complex species is assumed to be a simple monodentate copper ion-carboxylate species with a stability constant of 18.

Organic Geochemistry↗