Alice M. Bobra

Relationships between aqueous solubility and octanol-water partition coefficients

Abstract The physical chemical equations relating solubility to octanol water partition coefficient are presented and used to develop a new correlation between these quantities which includes a melting point (fugacity ratio) correction. The correlation is satisfactory for 45 organic compounds but it is not applicable to organic acids. When applied to very high molecular weight (> 290) compounds the correlation is less satisfactory; either it is believed because the data are inaccurate or because the tendency for these compounds to partition into organic phases is less than expected. This may have profound environmental implications.

Acute lethal toxicity of hydrocarbons and chlorinated hydrocarbons to two planktonic crustaceans: The key role of organism-water partitioning

Abstract The acute toxicities of 38 hydrocarbons and chlorinated hydrocarbons were determined for two planktonic crustaceans, freshwater Daphnia magna and saltwater Artemia. In both cases median lethal concentrations (LC50 values) at 48 h and 24 h, respectively, were strongly correlated with aqueous solubility, there being little direct dependence on chemical structure. In the case of solid chemicals, it is suggested that the appropriate correlating solubility is that of the subcooled liquid chemical, not that of the solid. Many solids constrained by low water solubility are thus unable to achieve dissolved concentrations sufficient to cause acute toxicity to the test organisms. It is hypothesised that acute toxicity is non-selective and is controlled by organism-water partitioning so that each hydrocarbon group may contribute equally to toxicity and no single group of hydrocarbons is the dominant toxicant. The partitioning characteristics are expressed in two mathematical models which relate the LC50 to the chemical properties of solubility and molar volume.

The water solubility of crude oils and petroleum products

Abstract Solubilities are reported for 42 crude oil and petroleum products in water as a function of temperature, salinity, oil weathering and water-to-oil volume ratio. The applicability of several analytical techniques (purge-and-trap gas chromatography, high pressure liquid chromatography, and fluorescence) for the determination of dissolved hydrocarbon concentrations is discussed critically. The effect of water-to-oil volume ratio on the apparent solubility of oils in water is discussed in detail.

A predictive correlation for the acute toxicity of hydrocarbons and chlorinated hydrocarbons to the water flea (Daphniamagna)

Abstract The acute toxicities of aqueous solutions of 33 hydrocarbons and chlorinated hydrocarbons to Daphnia magna were measured in a closed bioassay system. It was observed that the 48-hour LC 50 s were at similar fractions of the saturated solubilities (C L ), corresponding to the substances solubility in cases of liquids or the subcooled liquid solubility in cases of solids. An implication of these results is that the equi-toxic concentrations are at similar concentrations of these substances in the organism. These concentrations are controlled by organism-water partitioning. They are proportional to the water concentration and to the organism-water partition coefficient, which is in turn controlled by, and inversely proportional to C L . For these substances, toxicity is primarily determined by solubility, although compound-specific effects are also present. The implications and potential applications of the procedure are discussed.

Acute toxicity of dispersed fresh and weathered crude oil and dispersants to Daphnia Magna

The toxicity of fresh and weathered crude oils and chemical dispersants to Daphnia magna has been investigated using a novel system which eliminates evaporative losses and maintains oil in emulsified form at 5 and 20°C. Bioassays were conducted for dispersants alone, for water soluble fractions of crude oils obtained at various water/oil ratios, for physical dispersions of crude oils and for chemical dispersions of crude oils. The results suggest that generally the dispersed oil particles are the primary sources of toxicity, with the dissolved oil and dispersants contributing relatively little toxicity. The toxicity of the oil particles appears to be influenced by particle size. A mathematical model has been prepared and calibrated using these data, and gives a satisfactory representation of the observed toxicity of chemically dispersed oil.

Acute toxicity of fresh and weathered crude oils to Daphniamagna

Abstract The acute toxicites are reported of aqueous solutions of four fresh crude oils, nine weathered crude oils, a natural gas condensate and a synthetic oil mixture to Daphnia magna in a closed system. Fresh crude oils were observed to produce LC50s at dissolved oil concentrations which are 26 to 32% of their saturated solubilities. This is in agreement with previous work on pure hydrocarbons. Weathering a crude oil causes a marked reduction in solubility and a reduction in LC50, but the fraction of the solubility necessary to produce lethality increases until it exceeds 100%, i.e. it becomes impossible to form a lethal aqueous solution. Weathering thus produces aqueous solutions which are more toxic in the sense of having lower LC50s but the saturated solutions of weathered crude oils are less toxic as are the equi-diluted saturated solutions. Two methods of correlating the toxicity of fresh and weathered crude oils are proposed, one in which toxicity is related directly to aqueous solubility and another, in which the toxicities of the dominant dissolved components are added.

Distribution of hydrocarbons among oil, water and vapor phases during oil dispersant toxicity tests.

A set of equations has been derived which permit the calculation of the partition of a hydrocarbon or group of hydrocarbons between oil, water and vapor phases as may occur during dispersed oil toxicity testing. It is hoped that these equations will be useful in designing and interpreting the results from dispersed oil toxicity tests, especially in elucidating the relative toxic contributions of dissolved and particulate oil.

Structure-Activity Relationships for Toxicity of Hydrocarbons, Chlorinated Hydrocarbons and Oils to Daphnia Magna

Structure-activity relationships between hydrocarbon toxicity and physical-chemical properties are investigated. The acute toxicities of aqueous solutions of hydrocarbons, chlorinated hydrocarbons and crude oils to Daphnia magna in a closed bioassay system are reported and the toxicities correlated with solubilities.