Howard M. Liljestrand

Spatial variations of acid precipitation in southern California

Wet-precipitation-only samplers were used to collect acid . precipitation at nine sites in the Los Angeles basin of southern California during the 1978-1979 hydrolog1c year. Concentrations of the major cations (H^+, NH_4^+, Na^+, K^+, Ca_2^+, and Mg_2^+) and the major anions (Cl^-, NO_3^-, and SO_4^(2-)) as well as trace species were determined. The relative importances of natural and anthropogenic sources were calculated by a chemical balance. Variations of sea salt, soil dust, NH_4^+, SO_4^(2-), and NO_3^- contributions agreed with source ~istributions, scavenging, and advection patterns. The nitrate to non-sea-salt sulfate equivalent ratio varied from 0.4 near coastal stationary sources to 2.8 in rural mountain areas with a precipitation-weighted average ratio of 1.1. Equilibrium models are used to relate the chemical composition of rain water with P_(SO)_2, P_(NH)_3, P_(NO)_2, P_(NO), and P_(HNO)_3 during precipitation. Mass-balance calculations indicate that less than 2% of the anthropogenic emissions of NO_x and SO_x in southern California are locally scavenged on an annual basis.

Measured Effects of Liquid Soil Stabilizers on Engineering Properties of Clay

Stabilization of pavement subgrade soils and base materials has traditionally relied on treatment with lime, cement, and sometimes fly ash. Marketed as alternatives to these conventional bulk soil stabilizers, a variety of concentrated liquid chemical products are sold by several companies. Most transportation agencies, however, are hesitant to specify these nontraditional liquid stabilizers without reliable data to support vendor claims of product effectiveness. Standard laboratory soil tests were conducted to measure changes in the engineering properties of five clay soils when treated with three liquid chemical products. The tests involved three reference clays (kaolinite, illite, montmorillonite), two high-plasticity natural clays, and three representative liquid stabilizers (ionic, polymer, enzyme types). Tests were conducted on untreated control soil samples and on samples treated with each product at the suppliers’ recommended application rates. All of the test specimens were prepared in accordance with a specified 10-step protocol that allowed objective comparisons of the test results. Each treated and untreated soil was characterized in terms of the Atterberg limits, compacted unit weight, one-dimensional free swell potential, and undrained triaxial shear strength. Given some variation in the test samples, the test results did not show consistent, significant changes in the properties of these soils as a result of treatment with these three products. Higher application rates might yield more favorable results. Clearly, independent laboratory evaluations with project-specific soils are warranted before the use of these proprietary liquid stabilizers in the field.

Partitioning of moderately hydrophobic endocrine disruptors between water and synthetic membrane vesicles

The partition coefficient between water and lipid membrane vesicles (Klipw) has been used as an alternative to the 1-octanol-water partition coefficient (Kow) between water and organic solvent, because it more closely represents actual biological membranes. Despite theoretical differences, log Klipw correlates well with log Kow for conventional nonpolar organic pollutants. In the present study, Klipw values of 11 structurally diverse endocrine-disrupting chemicals (EDCs) were measured for three different types of lipid membrane vesicles from dipalmitoylphosphatidylcholine (DPPC), DPPC/cholesterol, and palmitoyloleoylphosphatidylcholine. Correlation analyses were conducted to evaluate the effects of hydrophobicity, molar liquid volume (MLV), and polar surface area (PSA) for 20 EDCs, including nine from a previous study. Correlations that include MLV and PSA reduce the predicted value of log Klipw, suggesting that lipid membranes are less favorable than 1-octanol for a hydrophobic solute because of the higher molar volume and higher hydrogen-bonding potential. These results suggested that Kow alone has limited potential for estimating Klipw and that additional descriptors are required. In addition, Klipw values vary by as much as two orders of magnitude because of the changes in membrane fluidity and the amount of cholesterol in the lipid bilayer. Therefore, lipid components should be chosen carefully to evaluate the bioconcentration of these compounds.

Mechanisms of Soil Stabilization with Liquid Ionic Stabilizer

Numerous commercial suppliers are marketing liquid chemical products for stabilizing pavement subgrade and base soils. These nontraditional chemical stabilizers may offer viable alternatives for stabilizing sulfate-rich soils where conventional lime or cement treatment can lead to excessive soil expansion. Typically sold as concentrated liquids that are diluted in water before application, these products may be less expensive to use than lime or cement. However, many transportation agencies are hesitant to specify nontraditional liquid stabilizers without better information on the stabilizing mechanisms and documented field experiences. To identify the mechanisms associated with one class of these products, a representative ionic soil stabilizer and a sodium montmorillonite clay were selected for a detailed physical-chemical study. Laboratory testing included chromatography, spectroscopy, X-ray diffraction, electron microscopy, and standard titration analyses. These tests have shown that the principal active constituents of the selected ionic stabilizer are d-limonene (a by-product of citrus processing) and sulfuric acid, which react to form a concentrated, low-pH solution of sulfonated limonene. The observed changes in clay chemistry following treatment indicated that this product would stabilize a soil by altering the clay lattice. The result is the formation of a more highly weathered, less-expansive clay structure. On the basis of this understanding of the underlying mechanisms, ionic stabilizers applied at sufficiently high application mass ratios may improve the properties of certain soils on some highway construction projects.

Effect of water content on transient nonequilibrium NAPL–gas mass transfer during soil vapor extraction

The effect of water content on the volatilization of nonaqueous phase liquid (NAPL) in unsaturated soils was characterized by one-dimensional venting experiments conducted to evaluate the lumped mass transfer coefficient. An empirical correlation based upon the modified Sherwood number, Peclet number, and normalized mean grain size was used to estimate initial lumped mass transfer coefficients over a range of water content. The effects of water content on the soil vapor extraction SVE process have been investigated through experimentation and mathematical modeling. The experimental results indicated that a rate-limited NAPL-gas mass transfer occurred in water-wet soils. A severe mass transfer limitation was observed at 61.0% water saturation where the normalized effluent gas concentrations fell below 1.0 almost immediately, declined exponentially from the initiation of venting, and showed long tailing. This result was attributed to the reduction of interfacial area between the NAPL and mobile gas phases due to the increased water content. A transient mathematical model describing the change of the lumped mass transfer coefficient was used. Simulations showed that the nonequilibrium mass transfer process could be characterized by the exponent beta, a parameter which described the reduction of the specific area available for NAPL volatilization. The nonequilibrium mass transfer limitations were controlled by the soil mean grain size and pore gas velocity, were well described by beta values below 1.0 at low water saturation, and were well predicted with beta values greater than 1.0 at high water saturation.

Average rainwater pH, concepts of atmospheric acidity, and buffering in open systems

Abstract The system of water equilibrated with a constant partial pressure of CO 2 , as a reference point for pH acidity-alkalinity relationships, has nonvolatile acidity and alkalinity components as conservative quantities, but not [H + ]. Simple algorithms are presented for the determination of the average pH for combinations of samples both above and below pH 5.6. Averaging the nonconservative quantity [H + ] yields erroneously low mean pH values. To extend the open CO 2 system to include other volatile atmospheric acids and bases distributed among the gas, liquid and particulate matter phases, a theoretical framework for atmospheric acidity is presented. Within certain oxidation-reduction limitations, the total atmospheric acidity (but not free acidity) is a conservative quantity. The concept of atmospheric acidity is applied to air-water systems approximating aerosols, fogwater, cloudwater and rainwater. The buffer intensity in hydrometeors is described as a function of net strong acidity, partial pressures of acid and base gases and the water to air ratio. For high liquid to air volume ratios, the equilibrium partial pressures of trace acid and base gases are set by the pH or net acidity controlled by the nonvolatile acid and base concentrations. For low water to air volume ratios as well as stationary state systems such as precipitation scavenging with continuous emissions, the partial pressures of trace gases (NH 3 , HCl, HNO 3 , SO 2 and CH 3 COOH) appear to be of greater or equal importance as carbonate species as buffers in the aqueous phase.

Diffusion of inorganic chemical species in compacted clay soil

This research was conducted to study the diffusion of inorganic chemicals m compacted clay soil for the design of waste containment barriers The effective diffusion coefficients (D*) of amonlc (C1 , Br , and I ) and cationic (K ~, Cd 2+, and Zn 2÷) species in a synthetic leachate were measured Two clay soils were used in the study. The soils were compacted and pre-soaked to mlmmlze mass transport due to suction in the soil The results of the diffusion tests were analyzed using two analytical solutions to Flcks second law and a commercially available seml-analyhcal solution, POLLUTE 3.3 Mass balance calculations were performed to indicate possible sinks/sources in the diffusion system Errors in mass balance were attributed to problems with the chemical analysis (I), the inefficiency of the extraction procedure (K ÷), precipitation (Cd 2. and Zn 2÷ ), and chemical complexatlon (C1- and Br-) The D* values for C1 reported in this study are in excellent agreement with previous findings for other types of soil The D* values for the metals (K + , Cd 2÷ , and Zn 2~ ) are thought to be high (conservative) due to (1) Ca 2÷ saturation of the exchange complex of the clays, (2) preclpitatmn of Cd 2÷ and Zn 2÷ , and (3) nonlinear adsorptmn behavior In general, high D* values and conservative designs of waste containment barriers will result if the procedures described in this study are used to determine D* and the adsorption behavior of the solutes is similar to that described in this study

Source contributions to acid precipitation in Texas

Abstract Wet-precipitation-only sampling at Austin, Prairie View and Highlands, Texas, has been conducted in 1980–1981 to characterize the main sources of acid rain chemical composition. These results are compared with those of previous investigators to identify spatial distributions of source contributions. A chemical mass balance model is used to determine the spatial distributions of background crustal source alkalinity and sea salt contributions. Moisture from the Gulf of Mexico influences all three sites, as confirmed by bivariate analysis. Ammonia gas from biogenic/agricultural sources is found to be a poor buffer against further acidification in areas of local acid emissions.

Use of a parallel artificial membrane system to evaluate passive absorption and elimination in small fish

A parallel artificial lipid membrane system was developed to mimic passive mass transfer of hydrophobic organic chemicals in fish. In this physical model system, a membrane filter-supported lipid bilayer separates two aqueous phases that represent the external and internal aqueous environments of fish. To predict bioconcentration kinetics in small fish with this system, literature absorption and elimination rates were analyzed with an allometric diffusion model to quantify the mass transfer resistances in the aqueous and lipid phases of fish. The effect of the aqueous phase mass transfer resistance was controlled by adjusting stirring intensity to mimic bioconcentration rates in small fish. Twenty-three simple aromatic hydrocarbons were chosen as model compounds for purposes of evaluation. For most of the selected chemicals, literature absorption/elimination rates fall into the range predicted from measured membrane permeabilities and elimination rates of the selected chemicals determined by the diffusion model system.

LABORATORY SORPTION AND HYDRAULIC CONDUCTIVITY TESTS: EVALUATION OF MODIFIED-CLAY MATERIALS

This study examines a new design philosophy for liner systems; that of controlling the hydraulic conductivity of leachate as a whole as well as retarding the advective and diffusive fluxes of pollutants by increasing the sorption of pollutants onto the liner systems. Claymax® (pure clay) and Organo-Clay (commercially available clays coated with organic amines) were evaluated as hydraulic barriers and as resistances to pollutant transport. Batch adsorption tests show that the removal capacity of lead by Claymax is 12-fold greater than that of Organo-Clay. However, the partition coefficients of a series of chlorobenzenes for Organo-Clay are 420-600 times greater than those for Claymax. The hydraulic conductivity of Claymax to tap water is at least two orders of magnitude lower than the value of 1 x 10-7 cms-1 for a clay liner required by the United States Environmental Protection Agency (EPA). Moreover, the hydraulic conductivity of Claymax with Organo-Clays is virtually unaffected when it is permeated with synthetic leachate.