Hinrich L. Bohn

Effect of sulfuric acid and sulfur dioxide on the aggregate stability of calcerous soils

The water-stable soil aggregates were measured for two noncalcareous, two sodic-cal-careous, and six calcareous soils as affected by H2SO4 and SO2 treatment. The aggregate stability, the percentage of silt and clay remaining as an > 50 μ aggregate, decreased with increasing amounts of H2SO4 and SO2 When H2SO4 was applied at 1.3 times the acidtitratable basicity of the soils, the aggregate stability decreased on the average from 62 to 17 percent in the caleareous soils and from 45 to 32 percent in the noncalcareous soils. The relative aggregate stability, the ratio of the destroyed portion of the aggregate to its total, decreased similarly with relative acidification for all the calcareous soils. Drying at 105°C for 24 hr after the H2SO4 further destroyed approximately 10 percent more aggregate at 20 percent neutralization of the basicity. The sorption of SO2 from moist streams also reduced the aggregate stability but the reduction was less than equivalent amounts of H2SO4 solutions.

Solid activities of trace elements in soils

Current predictions of the soil solutions composition are based on unit activity of the mineral phase. Natural minerals, however, are solid solutions whose solid activities depend on their composition. Solid activities can be rigorously defined if the solid solution is homogeneous, but solid solutions dissolve nonstoichiometrically (incongruently) and create inhomogeneity and disequilibrium between the solids surface and interior. Mineral-water suspensions can reach a partial equilibrium if the solids surface composition remain constant. Approximate solid activities can then be calculated from measured ion activity products in the aqueous phase.

Propane Removal from Propane-Air Mixtures by Soil Beds

Dilute concentrations of hydrocarbons are difficult and expensive to remove from air by conventional scrubbing methods. Propane removal from propane-air mixtures by soil beds was measured in laboratory experiments and in an industrial application. In closed containers in the laboratory, the time to reduce the initial 1–3 percent propane concentrations by half was 5 to 20 hours for soils at pH 6–8, moderate moisture contents, and temperatures ≥15°C. The propane removal rate was slower when the soil was air dry at 2°C temperature, or was pH 5.3. A test soil bed continuously removed 92-98 percent of the propane from an input air stream containing 0.6–1 percent propane.

Pollutant removal from wood and coal flue gases by soil treatment

If many homeowners convert to solid fuels for heating, residential flue gases will be a large source of air pollution. Control of this pollution requires an inexpensive, reliable, and effective method of flue gas treatment. One such method is to force flue gases through soil beds. Such soil treatment removes all detectable smoke, odor, and polynuclear organic matter (POM), up to 97% of the CO, and at least 97% of the SO2 from flue gases of wood and coal combustion. The technique is low cost, reliable, almost maintenance-free, and also appears suitable for other small point sources of air pollution.

Solid activity coefficients of soil components

Abstract Solute transport in soils depends on the solutes aqueous solubility, but predicting this solubility is limited by our meager knowledge of the activities of components in solid phases and on solid surfaces. Current predictions are based on the solubility of pure minerals. Natural minerals, however, are impure and exist as solid solutions or contain isomorphous substituents. The chemical potentials (activities) and aqueous solubilities of solid components depend on their concentration in the solid phase, if the solid is a solution rather than a mechanical mixture. Solid activities can be rigorously defined if the solid is homogeneous, but solid solutions dissolve nonstoichiometrically at the surface thus creating inhomogeneity and disequilibrium. Mineral-water suspensions can, however, reach a partial equilibrium if the solids surface composition remains constant. Then approximate solid activities can be calculated from measurements of the ion activity product in the aqueous soil solution. This paper discusses the assumptions necessary to calculate approximate solid activities in soils and presents some values calculated from soil measurements. This paper also derives some modified solid activity coefficients which are more convenient for soil solutions. The treatment is general but seems most appropriate for trace metal ions.

Beryllium effects on potatoes and oats in acid soil

The most likely means of Be entry into the food chain would appear to be via root, tuber, and forage crops grown on acid soils. Potatoes (Solanum tuberosum) and oats (Avena sativa) were grown in greenhouse pots of a strongly acid soil treated with 0 to 300 ppm Be and 0 to 1000 ppm CaC03. Germination and yield decreased, and plant Be content increased, with increasing soil Be content. The Be content of the potato tubers appeared to be low and unaffected by the soil Be content. Liming the soil and increasing the time between Be contamination and crop planting lessened the effect of Be.

A Clean New Gag

(1971). A Clean New Gag. Environment: Science and Policy for Sustainable Development: Vol. 13, Special Holiday Good News Issue, pp. 4-9.

Filtration of Airborne Particulates by Gravel Filters: I. Initial Collection Efficiency of a Gravel Layer

An equation derived for initial collection of efficiency E0 of a gravel bed filter predicts that — ln(1 — E0) is proportional to the thickness of the gravel layer, to the — 5/3 power of the diameter of uniform gravels, and to the — 2/3 power of the Darcy airflow velocity. The experimental data obtained from NH4CI fume removal from dry air at room temperature by sieved gravel fractions generally supported the equation, except that the effect of mean gravel size was represented by the —1.43 power of the average diameter.

Stability diagram of CaNaK-plagioclase with authigenic minerals

Abstract Conventional stability diagrams are limited essentially to the equilibria of aqueous solutions with pure end-member minerals. These diagrams extend to natural minerals containing isomorphous ion substitutes and to solid solutions if moles of ion charge are employed instead of moles. Stability diagrams derived from moles of ion charge are, in the strictest sense, limited to closed systems but natural solutions and solids tend to be open systems. Because natural solutions are not at complete equilibrium with solids, however, and because thermodynamic data are uncertain, stability diagrams derived from moles of ion charge in solution may be as applicable to natural conditions as diagrams based on moles.

CHEMICAL ACTIVITY AND AQUEOUS SOLUBILITY OF SOIL SOLID SOLUTIONS

Solid solutions are homogeneous or regular mixtures of two or more substances in a solid. Examples are glasses, olivine (Mg,Fe)2SiO4, kaolinite (Al(OH)3·AlOOH·2SiO2 or Al2Si2O5(OH)4), coprecipitates, isomorphous substitutes, and exchangeable cations. The chemical activity and aqueous solubility of a solid component decrease with its homogeneously- or regularly-mixed concentration in the solid. The decreased solid activity is responsible for the low equilibrium solubility of soil components and for ion retention by soils. This mechanism is also implicitly stated by cation exchange and adsorption equations. Solid solutions are likely to be nonideal mixtures because of the close proximity of ions in solids. The degree of nonideality is expressed by the activity coefficient. Several assumptions permit calculating individual solid ion activity coefficients, which range from 1 to 10 and average about 5, for Al and transition metal ions in soils. Iron(III), carbonate, sulfate, and phosphate ions have higher activity coefficients, representing their tendency to form separate phases (heterogeneous or mechanical mixing) rather than solid solutions. Ion interactions with O2− and OH− ligands on soil surfaces, plus the decrease in chemical activity due to homogeneous mixing of the ions with other ions on soil surfaces, i.e., the formation of solid solutions, can account for the strong retention of so many ions by soils.