Partitioning Of Organic Chemicals Research Articles

Toxic Burdens of Freshwater Biofilms and Use as a Source Tracking Tool in Rivers and Streams.

Biofilms, composed of periphyton, bacteria, and organic detritus, are the base of the food web in many streams and rivers. This media adsorbs and actively sequesters organic and inorganic contaminants from the water column. Here, we demonstrate the utility of using the contaminant concentrations in the biofilm matrix as an environmental media in source tracking and understanding biological impacts at higher trophic levels. Physical partitioning of polychlorinated biphenyl (PCB) and polybrominated diphenyl ether congeners is the dominant mode of uptake from water to biofilm and bioaccumulation factor: log Kow relationships suggest that PCB uptake is often near equilibrium between log Kow 5-7. We show that the concentrations of metals in biofilms are more effective at delineating and recording spatial and temporal differences in metal inputs than bed sediments and water samples. The burden of metals in the biofilm matrix explained adverse impacts and variability in periphyton metrics and ecological integrity in macroinvertebrates. This work provides new insights into the partitioning of organic chemicals onto biofilms and shows clear linkages between metals in the biofilm matrix and ecological health of invertebrates that depend on biofilms as a food source.

Evaluating the Salting-Out Effect on the Organic Carbon/Water Partition Ratios (KOC and KDOC) of Linear and Cyclic Volatile Methylsiloxanes: Measurements and Polyparameter Linear Free Energy Relationships

Dissolved inorganic salts influence the partitioning of organic chemicals between water and sorbents. We present new measurements of the salting-out constants (Ks) for partition ratios between water and organic carbon (KOC) and between water and dissolved organic carbon (KDOC) of three cyclic volatile methylsiloxanes (cVMS), two linear volatile methylsiloxanes (lVMS), three polychlorinated biphenyls (PCBs), and α-hexachlorocyclohexane (α-HCH). Ks, KOC, and KDOC were derived from volatilization rates of the chemicals from mixtures of water and organic carbon with varying concentrations of sodium chloride in a purge-and-trap system. KOC and KDOC values at different salinities were determined by fitting their values to reproduce observed volatilization rates using a fugacity-based multimedia model and assuming first-order kinetics for volatilization. The Ks values of cVMS and lVMS ranged from 0.16–0.76. The log KOC of cVMS and lVMS in fresh water interpolated from our measurements ranged from 5.20 to 7.36 an...

Applications of polyparameter linear free energy relationships in environmental chemistry.

Partitioning behavior of organic chemicals has tremendous influences on their environmental distribution, reaction rates, bioaccumulation, and toxic effects. Polyparameter linear free energy relationships (PP-LFERs) have been proven to be useful to characterize the equilibrium partitioning of organic chemicals in various environmental and technical partitioning systems and predict the respective partition coefficients. Over the past decade, PP-LFER solute descriptors for numerous environmentally relevant organic chemicals and system parameters for environmentally important partitioning systems have been determined, extending substantially the applicability of the PP-LFER approaches. However, the information needed for the use of PP-LFERs including descriptors and parameters is scattered over a large number of publications. In this work, we review the state of the art of the PP-LFER approaches in environmental chemical applications. The solute descriptors and system parameters reported in the literature and the availability of their database are summarized, and their calibration and prediction methods are overviewed. We also describe tips and pitfalls associated with the use of the PP-LFER approaches and identify research needs to improve further the usefulness of PP-LFERs for environmental chemistry.

Partitioning of Organic Chemicals to Storage Lipids: Elucidating the Dependence on Fatty Acid Composition and Temperature

Lipids serve as important compartments in partitioning of neutral organic chemicals into organisms. Storage lipids, made up of triglycerides with various fatty acids, are among the major classes of lipids. Here, we present experimental equilibrium partition data for diverse chemicals in fish oil, linseed oil, and goose fat at 37 °C. These data, in combination with data from the literature for olive oil and milk fat, show that the fatty acid composition of triglycerides has no significant influence on the partition coefficient. This result allows the derivation of a general predictive model for partitioning into storage lipids. We have collected storage lipid/water partition coefficients for 247 compounds to calibrate polyparameter linear free energy relationships (pp-LFERs) for 37 °C, which achieved a model fit with a root mean squared error of 0.20 log units. To extend the applicability of this model toward the aquatic food chain, we also measured fish oil partition data at 7 °C. The resulting enthalpies were used to calibrate an additional pp-LFER for the temperature dependence of storage lipid/water partitioning. This model allows us to estimate partition coefficients at desired temperatures that occur under typical ambient conditions.

Hexadecane/air partitioning coefficients of multifunctional compounds: Experimental data and modeling

The logarithmic hexadecane–air partitioning constant ( L) is one of the most common measures for solute–solvent nonspecific interaction. It is thus an essential compound descriptor for Linear Solute Energy Relationships (LSERs) that are used for predicting partitioning of organic chemicals. In this work L values from 2.3 to 13.7 – thus covering 11 orders of magnitude of the linear partitioning coefficient – were measured with standard deviations of <0.28 (average = 0.10) using inverse gas chromatography with non-polar capillary columns. The 104 studied compounds were all multifunctional, 52 of them were environmentally relevant pesticides, 6 hormones, 6 drugs and 4 phthalates. In addition, the predictive performance of 3 software tools (ABSOLVE, SPARC, COSMOtherm) for the L value was evaluated. To this end the data set was divided into 2 subsets: one with compounds containing maximally 2 functional groups and the other with more than 2 functional groups. None of the software tools reached the desired accuracy, defined as root mean square error over all compared compounds, of ±0.3 units. ABSOLVE performed well for the bifunctional compounds but failed for many pesticides and drugs. SPARC had major problems with highly fluorinated and phosphate containing compounds, but showed a good performance for all other compounds. COSMOtherm worked best for the predictions of the pesticides and drugs while its performance for the bifunctional compounds was somewhat poorer than the other tested models. Lastly, the experimental L values from this work were used to refine the LSER descriptors S, A and B of a suite of multifunctional and mostly polar compounds including pesticides and pharmaceuticals. The performance of the refined descriptors was significantly better for the prediction of the water–air partitioning, equal for the heptane–methanol partitioning but slightly poorer for the octanol–water partitioning than that of the former values.

VOC and SVOC Emissions from Slurry and Solid Phase Bioremediation Processes

Gaseous emissions of volatile organic compounds (VOCs) and semi-VOCs (SVOCs) from slurry and solid phase bioremediation processes were evaluated. The specific processes considered were those used for the bioremediation of concentrated industrial wastes and of contaminated soils and sediments. The purpose of the evaluation was to document the extent to which such processes emit VOCs and SVOCs. Such information is needed to answer questions such as (1) what are the VOC and SVOC emissions that occur during the operation of these processes?; (2) should emission controls be considered for such processes?; and (3) to what extent does volatilization contribute to the loss of organic compounds in what is considered a bioremediation process? These questions are relevant to understanding the performance of aerobic processes treating concentrated hydrocarbons. The results of this evaluation indicated that, although volatile losses of VOCs and SVOCs can occur from slurry and solid phase bioremediation units, in such units, biodegradation is the primary method of SVOC loss. In well-acclimated bioremediation units, biodegradation of xylene/somers also can be a primary chemical loss mechanism. In situations where mass balances of SVOCs could be determined, volatile losses of SVOCs such as polycyclic aromatic hydrocarbons and polychlorinated biphenyls were <0.1% and frequently <0.01% of the mass of such chemicals in the bioremediation units. Greater volatile losses occurred in the initial phase of units operated as batch bioreactors. This is likely due to higher concentration driving forces from the liquid phase to the air phase coupled with biomass that is not fully acclimated to degrading the added VOCs and SVOCs. To minimize volatilization losses from bioreactors, the bioreactors should be designed and operated as well-acclimated continuously fed units rather than as intermittent batch units. There are many fundamental and operational factors that can affect gaseous emissions from bioremediation units. The more important factors are the partitioning of organic chemicals to solids in the unit, rate of microbial activity, volatility of the chemicals, and manner in which the unit is operated.

Prediction of Soil Sorption Coefficients Using a Universal Solvation Model

Using a database of 440 molecules, we develop a set of effective solvent descriptors that characterize the organic carbon component of soil and thereby allow quantum mechanical SM5 universal solvation models to be applied to partitioning of solutes between soil and air. Combining this set of effective solvent descriptors with solute atomic surface tension parameters already developed for water/air and organic solvent/air partitioning allows one to predict the partitioning of any solutes composed of H, C, N, O, F, P, S, Cl, Br, and I between soil and water. We also present linear correlations of soil/water partitioning with 1-octanol/water partition coefficients using the same database. The quantum mechanical calculations have the advantages that they require no experimental input and should be robust for a wide range of solute functionality. The quantitative effective solvent descriptors can be used for a better understanding (than with previously available models) of the sources of different partitioning phenomena in cases where the results exhibit significant fragment interactions. We anticipate that the model will be useful for understanding the partitioning of organic chemicals in the environment between water and soil or, more generally, between water and soil or sediments (geosorbents).

Partitioning of Organic Chemicals to Polyacrylate-Coated Solid Phase Microextraction Fibers: Kinetic Behavior and Quantitative Structure−Property Relationships

The solid phase microextraction technique uses polymer-coated fused-silica fibers to extract organic chemicals from an aqueous or gaseous phase. In the current paper, the partitioning behavior of organic chemicals from water to polyacrylate coating is described in terms of a two-compartment model and first-order kinetics. Experimental results show that, through agitation, it is possible to achieve a sufficiently small aqueous diffusion layer around the fiber to prevent aqueous diffusion from being the limiting factor in the absorption process. This then implies that the equilibration time is completely determined by the polyacrylate phase. In addition, the kinetic rate constants derived from the experimental results, viz. the uptake rate constant and polyacrylate−water partition coefficient, are modeled by multivariate techniques, using physicochemical and quantum chemical descriptors. These models clearly show that, besides hydrophobicity expressed as the octanol−water partition coefficient, the energy of the lowest unoccupied molecular orbital (and related properties) and the most positive charge on any hydrogen atom in the molecule are important descriptors. This indicates that hydrogen bonding plays a significant role in polyacrylate−water partitioning. The models that are presented can be used to predict absorption profiles of organic chemicals to polyacrylate-coated fibers, thereby giving the opportunity to predict the kinetics (including equilibration times) by computations alone.

A Thermodynamic analysis of the relationships between molecular size, hydrophobicity, aqueous solubility and octanol-water partitioning of organic chemicals

This study presents a thermodynamic analysis of the relationship between molecular size, hydrophobicity, aqueous solubility and octanol-water partitioning for several classes of hydrophobic organic compounds including chlorinated dibenzo p-dioxins, PCBs, polynuclear aromatic hydrocarbons, alkylbenzenes, linear alcohols and alkanes. The purpose of the thermodynamic analysis is to explore the contribution of chemical-water and chemical-chemical interactions involved in the aqueous solution process. This is important for the development of relationships between the molecular structure and environmentally relevant properties of organic chemicals. The results show that the free energy of aqueous solvation is virtually independent on the molar volume of the solute for each of the congeneric series that was investigated. Within each congeneric series, congeners are therefore approximately equally “hydrophobic”, and the relationship between the aqueous solubility of (subcooled) liquid hydrophobic chemicals and molecular volume predominantly reflects the dependence of chemical-chemical interactions on the molecular volume in the (subcooled) liquid phase, rather than chemical-water interactions as is usually assumed. The results indicate that improvements of quantitative structure-aqueous solubility relationships may be achieved by modelling chemical-chemical interactions in the pure (subcooled) liquid phase, rather than merely chemical-water interaction, and that within congeneric series of non-polar organic substances, an increase in octanol-water and environmental partition coefficients with increasing congener size is due to an increase in the congener's lipophilicity, not hydrophobicity.

Partitioning of organic chemicals at the air-water interface in environmental systems

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPartitioning of organic chemicals at the air-water interface in environmental systemsJohn T. Hoff, Donald Mackay, Robert Gillham, and Wan Ying ShiuCite this: Environ. Sci. Technol. 1993, 27, 10, 2174–2180Publication Date (Print):October 1, 1993Publication History Published online1 May 2002Published inissue 1 October 1993https://doi.org/10.1021/es00047a026RIGHTS & PERMISSIONSArticle Views682Altmetric-Citations110LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (865 KB) Get e-Alerts Get e-Alerts

Dynamic partitioning of organic chemicals in regional environments: a multimedia screening-level modeling approach

A screening-level spatial-multimedia-compartmental (SMCM) approach to modeling the fate and transport of volatile organic pollutants in regional environments is presented. The SMCM approach, which makes use of both uniform (i.e., well-mixed) and nonuniform (one-dimensional) compartments, incorporates a variety of transport phenomena associated with pollutant transport such as dry deposition, rain scavenging, runoff, infiltration, soil drying, and pollutant diffusion and convection in the vadose zone. The multimedia distributions of trichloroethylene, tetrachloroethylene, and 1,1,1-trichloroethane in the Los Angeles area, and tetrachloroethylene in the San Diego area, were explored by using the SMCM model. The predicted concentrations were found to be in reasonable agreement with the available field data. The study suggests that the SMCM approach is useful and efficient for rapid screening-level analysis of the steady-state or dynamic multimedia distribution of chemical pollutants.

The extent of multimedia partitioning of organic chemicals

This paper examines the question of the extent of multimedia partitioning of organic chemicals. Partition profiles are estimated for releases into air, water, and soil. The analysis shows that cross-media partitioning can be expected for 50 – 80 % of all organic chemicals.