Fugacity capacity

Abstract: Dermal and non-dietary pathways are potentially significant exposure pathways to pesticides used in residences. Exposure pathways include dermal contact with residues on surfaces, ingestion from hand- and object-to-mouth activities, and absorption of pesticides into food. A limited amount of data has been collected on pesticide concentrations in various residential compartments following an application. But models are needed to interpret this data and make predictions about other pesticides based on chemical properties. In this paper, we propose a mass-balance compartment model based on fugacity principles. We include air (both gas phase and aerosols), carpet, smooth flooring, and walls as model compartments. Pesticide concentrations on furniture and toys, and in food, are being added to the model as data becomes available. We determine the compartmental fugacity capacity and mass transfer-rate coefficient for wallboard as an example. We also present the framework and equations needed for a dynamic mass-balance model.

Abstract: 1 Introduction.- 2 Fundamental Properties of Chemicals.- 2.1. Introduction.- 2.2. Molecular and molar properties.- 2.2.1. Molecular structure.- 2.2.2. Additive and constitutive properties.- 2.2.3. The quantification of molecular structure.- 2.2.4. The development of an index of molecular connectivity.- 2.2.5. Applications of the molecular connectivity index.- 2.2.6. Structure-activity relationships and toxicology.- 2.3. Partition coefficients.- 2.3.1. Additive-constitutive properties.- 2.3.2. Fragment constants.- 2.3.3. Molecular connectivity.- 2.3.4. Experimental determination of partition coefficient.- 2.3.5. Activity coefficients.- 2.4. Partition coefficient and bioconcentration.- 3 Chemical Release and Environmental Pathways.- 3.1. Natural phenomena.- 3.2. Human activities.- 3.3. Manufacturing processes.- 3.4. Physical form and source description.- 3.5. Estimating releases.- 3.6. Environmental pathways.- 4 Modelling Strategies.- 4.1. Modelling philosophy.- 4.2. Model categories.- 4.3. Material balance and dimensional analysis.- 4.4. Partitioning models.- 4.5. Fugacity.- 4.5.1. Fugacity capacities (Z).- 4.5.2. Fugacity models.- 4.5.3. Calculation of fugacity capacity.- 4.6. System design.- 4.7. Model evaluation.- 5 The Soil Environment.- 5.1. Introduction.- 5.2. Physical processes.- 5.2.1. Adsorption.- 5.2.2. Diffusion.- 5.2.3. Volatilization.- 5.3. Chemical processes.- 5.3.1. Ionization.- 5.3.2. Hydrolysis.- 5.3.3. Oxidation/reduction.- 5.3.4. Complexation.- 5.4. Mathematical models of soil systems.- 5.4.1. Unsaturated soil zone (soil) modeling.- 5.4.2. Saturated soil zone (groundwater) modeling.- 5.4.3. Ranking models.- 5.4.4. Aquatic equilibrium models.- 6 The Aquatic Environment.- 6.1. Introduction.- 6.2. The hydrosphere.- 6.3. Physical processes.- 6.3.1. Hydrodynamic transport.- 6.3.2. Solubility in water.- 6.3.3. Volatilization from water.- 6.4. Chemical processes.- 6.4.1. Aqueous photolysis.- 6.4.2. Metals in water.- 6.5. Biodegradation..- 6.6. Mathematical models.- 6.6.1. Environmental rates approach.- 6.6.2. Model ecosystem approach.- 6.6.3. Aquatic fate models.- 7 The Atmospheric Environment.- 7.1. Introduction.- 7.2. Acidification pathways.- 7.2.1. Sulphur dioxide.- 7.2.2. Oxides of nitrogen.- 7.2.3. Chlorofluorocarbons and ozone depletion.- 7.3. Atmospheric sink mechanisms.- 7.3.1. Removal processes.- 7.4. Atmospheric residence time.- 7.5. Atmospheric dispersion modeling.- 7.5.1. Simple models.- 7.5.2. More complex models.- 8 Conclusions.- References and Bibliography.

Abstract: Equilibrium sampling of organic pollutants into the silicone polydimethylsiloxane (PDMS) has recently been applied in biological tissues including fish. Pollutant concentrations in PDMS can then be multiplied with lipid/PDMS distribution coefficients (DLipid,PDMS) to obtain concentrations in fish lipids. In the present study, PDMS thin films were used for equilibrium sampling of polychlorinated biphenyls (PCBs) in intact tissue of two eels and one salmon. A classical exhaustive extraction technique to determine lipid-normalized PCB concentrations, which assigns the body burden of the chemical to the lipid fraction of the fish, was additionally applied. Lipid-based PCB concentrations obtained by equilibrium sampling were 85 to 106% (Norwegian Atlantic salmon), 108 to 128% (Baltic Sea eel), and 51 to 83% (Finnish lake eel) of those determined using total extraction. This supports the validity of the equilibrium sampling technique, while at the same time confirming that the fugacity capacity of these lipid-rich tissues for PCBs was dominated by the lipid fraction. Equilibrium sampling was also applied to homogenates of the same fish tissues. The PCB concentrations in the PDMS were 1.2 to 2.0 times higher in the homogenates (statistically significant in 18 of 21 cases, p < 0.05), indicating that homogenization increased the chemical activity of the PCBs and decreased the fugacity capacity of the tissue. This observation has implications for equilibrium sampling and partition coefficients determined using tissue homogenates. Environ. Toxicol. Chem. 2011; 30:1515–1521. © 2011 SETAC

Abstract: A major route of exposure to hydrophobic organic contaminants (HOCs), such as benzo[a]pyrene (BaP), is ingestion. Matrix-bound HOCs may become bioavailable after mobilization by the gastrointestinal fluids followed by sorption to the intestinal epithelium. The purpose of this research was to measure the bioavailability of [14C]-BaP bound to pristine soils or field-contaminated sediment using an in vitro model of gastrointestinal digestion followed by sorption to human enterocytes (Caco-2 cells) or to a surrogate membrane, ethylene vinyl acetate (EVA) thin film. Although Caco-2 cells had a twofold higher lipid-normalized fugacity capacity than EVA, [14C]-BaP uptake by Caco-2 lipids and EVA thin film demonstrated a linear relationship within the range of BaP concentrations tested. These results suggest that EVA thin film is a good membrane surrogate for passive uptake of BaP. The in vitro system provided enough sensitivity to detect matrix effects on bioavailability; after 5 h, significantly lower concentrations of [14C]-BaP were sorbed into Caco-2 cells from soil containing a higher percentage of organic matter compared to soil with a lower percentage of organic matter. The [14C]-BaP desorption rate from Caco-2 lipids consistently was twofold higher than from EVA thin film for all matrices tested. The more rapid kinetics observed with Caco-2 cells probably were due to the greater surface area available for absorption/desorption in the cells. After 5 h, the uptake of BaP into Caco-2 lipid was similar in live and metabolically inert Caco-2 cells, suggesting that the primary route of BaP uptake is by passive diffusion. Moreover, the driving force for uptake is the fugacity gradient that exists between the gastrointestinal fluid and the membrane.