Three-terminal dielectric bridge measurements (in the range 20 Hz to 100 kHz between — 5°C and —90 to — 120°C) have been made of ice doped with (a) conductivity-enhancing ionic impurities (HCl, HF, NaCl, KF, NH4F) and (b) conductivity-depressing solutes (NH4OH, NH4Cl, NH5CO3, NaHCO3). Blocking electrodes were used for the first group. The true ice parameters were extracted from linearized plots of the Debye equations. Chlorides and fluorides showed very similar characteristics in their spectra and static conductivity. The results suggest that static conductivity is controlled by extrinsic protons. On the other hand, bases, or solutes that impart a positive freezing potential to the ice, suppress extrinsic protons. In this case, the static conductivity was not, or only weakly, temperature dependent and lower than in the first group. A conductivity cross-over was observed in neither case. The dielectric conductivity contribution is strongly dependent on impurity concentration but apparently less affected than the static conductivity by the nature of the solute. The principal relaxation time is reduced by most solutes, exceptions are pure (bicarbonate-free) bases, sodium bicarbonate, and carbon dioxide.

ABSTRACT. Three-terminal dielectric bridge m easurem ents (in the range 20 Hz to 100 kHz between -5°C a nd -go to -120°C) have been made of ice doped with (a ) conductivity-enhancing ionic impurities (HCI, HF, NaCI, KF, NH.F) and (b ) conductivity-depressing solutes (NH.OH, NH.CI, NH s C0 3 , NaHC0 3 ) . Blocking electrodes were used for the first group. The true ice parameters were extracted from linearized plots of the D e bye equations. Chlorides and fluorid es showed very similar characteristics in their spectra and static conduc tivity. The results sugges t that static conductivity is controlled by extrinsic protons. On the other h and , bases, or solutes that impart a p ositive freezing potential to the ice, suppress extrinsic protons. In this case, the stati c conductivity was not, or only weakly, te mperat ure depe ndent and lower than in the first group. A conduc tivity cross-over was observed in neither case. The diel ectric conductivity contribution is strongly dependent o n impurity conce ntration but a ppare ntly less affected than the static con ductivity by the nature of the solute. The principal relaxation time is reduced by most solutes, exceptions are pure (bicarbonate-free) bases, sodium bicarbonate, and carbon dioxide. R EsuME. Conductiuitc et dispersion clectrigue de cristaux de glace dopis auec des impuretcs en concentration co/Inlle. Nous avons effectu e des mesures e lectriques a la m e thode du pont (d e 20 Hz a 100 kHz e ntre -5°C et -go, -120°C) dans le cas d e glace dopee avec: (a ) des impuretes ioniques augmentant la conductivite (HCl, HF, NaCI, KF, NH.F), et (b ) d es impuretes diminuant la conductivite (NH.OH, NH.Cl, NH 5 CO" NaH C0 3 ) . D es electrodes bloqua ntes ont ete utilisees d ans le premier cas. Les param etr es propres a la glace ont ete obtenus a partir des form es linearisees des equa tions de D e bye. L es chlorures e t Ies fluorures entrainent des caracteristiques tres semblables d a ns les spectres et la conductivite statique . L es resultats suggerent que la conductivite en courant continu est co ntrcMe par des protons extrinseques, c'est-a-dire introduits p a r les impuretes. Au contra ire, les hydroxydes et les sels qui conduisent la glace a presenter un potentiel positif lors de la congelation, supprime nt les protons extrinseques. Dans ce cas la conductivite en coura nt continu n'est pas, ou seul ement faiblement, d ep endante de la temperature; e1le est, e n outre bien plus faible que pour le premier groupe d 'impuretes. L e "cross-over" de conductivite n'a e te observe dans a ucun d es cas . La contribution dieIectrique a la conductivite depend fortement de la concentration en impuretes mais est beaucoup moins affecte par la nature des impuretes que la conduc ti v ite en courant continu. L e temps d e relaxation prin cipal est diminue par toutes les impure tes saufles hydrox ydes purs (sans CO 2 ), le bi carb o n ate de sod ium e t le dioxyde de carbo n e .ZUSAMMENFASSUNG . Elektrische L eitfiihigkeit IllId R elaxation in Eiskristallen mit bekanntem Gehalt a...

A systematic study of the dielectric relaxation spectrum of ionic impurities in ice over a wide range of concentrations and temperatures required the development of methods to compare the spectra. The studied impurities fall roughly into two categories, those that increase the dc conductivity of the ice and attendant space‐charge effects, and those that suppress these effects. The former were measured with blocking layers inserted between the sample and electrodes, the latter with stainless steel guard electrodes. Linearized plots of the Debye expressions were used for separating up to 4 spectral components by an iterative fitting and correction technique. With blocking layers, the Maxwell‐Wagner model of a layered dielectric yields the ice bulk parameters. Analysis suggests that, in general, ice is best described by a small number of discrete components, each characterized by a single relaxation time. Advantages of the blocking‐layer technique are experimental simplicity, reproducible values of electrical parameters obtained exclusively from ac measurements, and the systematic coverage possible. The results are useful for evaluating electrical properties of ice in the environment. The model should be applicable to the investigation of rocks other than ice.

Interest in using technical standards to evaluate revegetation success, specifically for cover, production, and diversity parameters, at coal mines is increasing. To help evaluate the feasibility of developing such standards in Wyoming, a vegetation database was established for five mines in the Southern Powder River Basin. The baseline vegetation data for these mines comprised fifteen data sets (individual studies), and within these sets, the data were separated into five major and six minor standardized plant communities. Baseline data were collected during twelve years from 1978 through 1999, although not all standardized plant communities were sampled in each of those twelve years. In the two predominant plant communities, Mixed Grass Prairie (MGP) and Big Sagebrush Shrubland (BSS), statistical evaluations of the data sets revealed two important considerations. First, for cover data, the results are statistically different between quadrat and point-transect sampling methods. Second, herbaceous species production data can be correlated with precipitation over a relatively small area (e.g., an individual mine), but the influence of other factors, such as sampling methodology, preclude correlations over larger areas. Production data could not be correlated with Palmer Drought Indices, and cover data could not be correlated with either climate factor. The statistical evaluations also indicated significant differences between the data sets and between the mines. Based on all the evaluations of the available data, calculation of a regional data technical standard using detailed statistical methods may be difficult. While a simple approach, such as selection of a conservative number (e.g., the highest mean production value) might be considered, calculation of cover and production standards on an individual mine basis is considered feasible.

Interest in the ground water quality distributions at uranium in situ mining wellfields has increased because of the need to address differences in federal and state water quality standards and restoration requirements. There has been considerable discussion about the water quality distributions at individual wellfields because of specific operators' concerns (e.g., modifying a monitoring program). However, this is one of the first overviews of water quality distributions at wellfields in Wyoming. Three water quality parameters (Total Dissolved Solids (TDS), uranium, and radium) were evaluated at nine wellfields. These parameters were selected for information on overall water quality (TDS) and on water quality in the vicinity of the production zones (uranium and radium). Box and Whisker Plots were used to compare the TDS and Uranium concentrations in each production zone and surrounding monitor ring. Visually, the plots indicate that it is difficult to distinguish between TDS concentrations in a production zone and surrounding monitor ring, and the TDS concentrations are all below 1,200 milligrams per liter (mg/l) with the majority below 500 mg/l. In contrast, it is much easier to distinguish the uranium concentrations in a production zone because they are generally much higher than the concentrations in the surrounding monitor ring. This is confirmed by statistical analyses. Even so, the uranium concentrations in the production zone often do not exceed 0.03 mg/l, the Maximum Concentration Limit for uranium established by the U.S. Environmental Protection Agency for drinking water. Frequency histograms of radium concentrations in the production zones show scattered data, and most of the concentrations exceed 100 picoCuries per liter (pCi/l). In contrast, the majority of the radium concentrations in the monitor rings are less than 100 pCi/l, with most less than 20 pCi/l, and the higher concentrations are only in a few wells in the ring (generally in areas where the ore trend extends beyond the mining area). The limited contrast in TDS concentrations, as compared to the generally significant contrasts in uranium and radium concentrations, inside and outside a production zone must be taken into consideration in efforts to harmonize federal and state ground water quality standards and restoration criteria.