The occurrence and atmospheric behavior of tri- to deca-polybrominated diphenyl ethers (PBDEs) were investigated during a 2-week campaign concurrently conducted in July 2012 at four background sites around the Aegean Sea. The study focused on the gas/particle (G/P) partitioning at three sites (Ag. Paraskevi/central Greece/suburban, Finokalia/southern Greece/remote coastal, and Urla/Turkey/rural coastal) and on the size distribution at two sites (Neochorouda/northern Greece/rural inland and Finokalia/southern Greece/remote coastal). The lowest mean total (G + P) concentrations of ∑7PBDE (BDE-28, BDE-47, BDE-66, BDE-99, BDE-100, BDE-153, BDE-154) and BDE-209 (0.81 and 0.95 pg m-3, respectively) were found at the remote site Finokalia. Partitioning coefficients, K P, were calculated, and their linear relationships with ambient temperature and the physicochemical properties of the analyzed PBDE congeners, i.e., the subcooled liquid pressure (P L°) and the octanol-air partition coefficient (K OA), were investigated. The equilibrium adsorption (P L°-based) and absorption (K OA-based) models, as well as a steady-state absorption model including an equilibrium and a non-equilibrium term, both being functions of log K OA, were used to predict the fraction Φ of PBDEs associated with the particle phase. The steady-state model proved to be superior to predict G/P partitioning of BDE-209. The distribution of particle-bound PBDEs across size fractions < 0.95, 0.95-1.5, 1.5-3.0, 3.0-7.2, and > 7.2 μm indicated a positive correlation between the mass median aerodynamic diameter and log P L° for the less brominated congeners, whereas a negative correlation was observed for the high brominated congeners. The potential source regions of PBDEs were acknowledged as a combination of long-range transport with short-distance sources.
- MeSH
- Adsorption MeSH
- Halogenated Diphenyl Ethers analysis MeSH
- Air Pollutants analysis MeSH
- Environmental Monitoring * MeSH
- Publication type
- Journal Article MeSH
- Geographicals
- Greece MeSH
A model for gas-particle partitioning of polycyclic aromatic hydrocarbons (PAHs) was evaluated using polyparameter linear free energy relationships (ppLFERs) following a multiphase aerosol scenario. The model differentiates between various organic (i.e., liquid water-soluble (WS)/organic soluble (OS) organic matter (OM), and solid/semisolid organic polymers) and inorganic phases of the particulate matter (PM). Dimethyl sulfoxide and polyurethane were assigned as surrogates to simulate absorption into the above-mentioned organic phases, respectively, whereas soot, ammonium sulfate, and ammonium chloride simulated adsorption processes onto PM. The model was tested for gas and PM samples collected from urban and nonurban sites in Europe and the Mediterranean, and the output was compared with those calculated using single-parameter linear free energy relationship (spLFER) models, namely Junge-Pankow, Finizio, and Dachs-Eisenreich. The ppLFER model on average predicted 96 ± 3% of the observed partitioning constants for semivolatile PAHs, fluoranthene, and pyrene, within 1 order of magnitude accuracy with root-mean-square errors (RMSE) of 0.35-0.59 across the sites. This was a substantial improvement compared to Finizio and Dachs-Eisenreich models (37 ± 17 and 46 ± 18% and RMSE of 1.03-1.40 and 0.94-1.36, respectively). The Junge-Pankow model performed better among spLFERs but at the same time showed an overall tendency for overestimating the partitioning constants. The ppLFER model demonstrated the best overall performance without indicating a substantial intersite variability. The ppLFER analysis with the parametrization applied in this study suggests that the absorption into WSOSOM could dominate the overall partitioning process, while adsorption onto salts could be neglected.
A combined modeling and spectroscopic approach is used to describe Cd(II), Cr(VI), and Pb(II) adsorption onto nanomaghemite and nanomaghemite coated quartz. A pseudo-second order kinetic model fitted the adsorption data well. The sorption capacity of nanomaghemite was evaluated using a Langmuir isotherm model, and a diffuse double layer surface complexation model (DLM) was developed to describe metal adsorption. Adsorption mechanisms were assessed using X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. Pb(II) adsorption occurs mainly via formation of inner-sphere complexes, whereas Cr(VI) likely adsorbs mainly as outer-sphere complexes and Cd(II) as a mixture of inner- and outer-sphere complexes. The simple DLM describes well the pH-dependence of single adsorption edges. However, it fails to adequately capture metal adsorption behavior over broad ranges of ionic strength or metal-loading on the sorbents. For systems with equimolar concentrations of Pb(II), Cd(II), and Cr(VI). Pb(II) adsorption was reasonably well predicted by the DLM, but predictions were poorer for Cr(VI) and Cd(II). This study demonstrates that a simple DLM can describe well the adsorption of the studied metals in mixed sorbate-sorbent systems, but only under narrow ranges of ionic strength or metal loading. The results also highlight the sorption potential of nanomaghemite for metals in complex systems.
- MeSH
- Adsorption MeSH
- Chromium chemistry MeSH
- Photoelectron Spectroscopy MeSH
- Cadmium chemistry MeSH
- Kinetics MeSH
- Hydrogen-Ion Concentration MeSH
- Quartz chemistry MeSH
- Nanostructures chemistry MeSH
- Lead chemistry MeSH
- Osmolar Concentration MeSH
- X-Ray Absorption Spectroscopy MeSH
- Models, Theoretical * MeSH
- Ferric Compounds chemistry MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Modern drugs with low bioavailability (such as hypolipidemics, anti-inflammatory drugs, diuretics) present, due to their poor water solubility a significant problem in the formulation of solid dosage forms intended for systemic absorption of the active substance. Several methods have been described for improving solubility and hence bioavailability of the mentioned drugs. One of the most promising techniques is the incorporation of active substance in liquid-solid systems. The systems are based on the conversion of a liquid drug to a free-flowing compressible dry powder, by sorption on suitable excipients – porous carriers (alumsilicates, microcrystalline cellulose), coated subsequently with a material of high absorption capacity (SiO2). Liquid-solid systems exhibit some advantages including low production costs, simple processing and enhanced drug release. The main benefit is high bioavailability of the liquid drug, caused by the large surface area available for absorption without previous dissolution of active substance. The review clarifies specific aspects associated with the formulation of liquid-solid systems – excipients and their properties (surface area, adsorption capacity), methods of preparation, process variables (solubility, liquid loading) and evaluation of the dosage form.
- MeSH
- Absorption MeSH
- Anti-Inflammatory Agents administration & dosage pharmacokinetics MeSH
- Biological Availability * MeSH
- Chemical Phenomena MeSH
- Diuretics administration & dosage pharmacokinetics MeSH
- Technology, Pharmaceutical MeSH
- Hypolipidemic Agents administration & dosage pharmacokinetics MeSH
- Dosage Forms MeSH
- Drug Delivery Systems * MeSH
- Humans MeSH
- Methylcellulose MeSH
- Drug Carriers MeSH
- Polyethylene Glycols MeSH
- Surface-Active Agents MeSH
- Drug Design * MeSH
- Solubility MeSH
- Tablets MeSH
- Check Tag
- Humans MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
... 2.3.2.2 Chemiluminescence (luminol) 2.3.2.3 Laser-induced fluorescence and tuneable diode laser absorption ... ... 47 iv -- 2.4.3.1 Transport of reactive nitrogen species in urban plumes 49 -- 2.4.3.2 Air quality models ... ... with combustion space heaters 96 -- 3.5.4 Indoor nitrous acid concentrations 107 -- 3.5.5 Predictive models ... ... COMPOUNDS (PARTICULARLY NITROGEN OXIDES) ON PLANTS 115 -- 4.1 Properties of NOx and NHy 122 -- 4.1.1 Adsorption ... ... oxide compounds 270 -- 5.4.1 Nitric oxide 270 -- 5.4.1.1 Endogenous formation of NO 270 -- 5.4.1.2 Absorption ...
Environmental health criteria, ISSN 0250-863X 188
2nd ed. 550 s. : il. ; 21 cm
- Conspectus
- Lékařské vědy. Lékařství
- NML Fields
- hygiena
- hygiena
- toxikologie
- NML Publication type
- publikace WHO
... methods 21 -- 2.4.1 Sampling and analysis in air 28 -- 2.4.1.1 Direct measurement 28 -- 2.4.1.2 Adsorption-liquid ... ... desorption 28 -- 2.4.1.3 Adsorption-thermal desorption 28 -- 2.4.1.4 Cold trap-heating 28 -- 2.4.2 Sampling ... ... KINETICS IN LABORATORY ANIMALS -- AND HUMANS 48 -- 6.1 Pharmacokinetics 48 -- 6.1.1 Absorption 48 -- ... ... Distribution 49 -- 6.1.3 Elimination and fate 51 -- 6.1.4 Physiologically based pharmacokinetic modelling ...
Environmental health criteria ; 163
[1st ed.] 174 s. : tab. ; 18 cm
