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Few data exist for the surface area of snow despite its importance for modeling wet deposition and migration of reversibly deposited contaminants in snow. A method for determining the surface area of snow is described that uses a commercial nitrogen adsorption instrument (Gemini III 2375, Micromeritics Instruments Inc.). The method uses a sample vial containing snow and a reference vial containing an equal amount of snow that has been melted and refrozen in order to minimize its surface area. The basic quantity measured is the difference in volumes of nitrogen delivered to the sample and reference vials. This volume difference must be corrected for the free space difference in the vials before the adsorbed volume of nitrogen can be inferred. Two methods for obtaining this correction are discussed, measured, and estimated, and the results of BET analysis are presented for both types of correction. Fresh snow samples collected in southern Ontario exhibit type II isotherms with moderate to small BET constant...

Biosorption has attracted attention as a cost-effective means for the treatment of metal-bearing wastewater. However, the mechanism of metal binding is not clearly understood, and consequently, modeling of the biosorption performance is still raising debates. In this study, the biosorption of trivalent chromium was investigated with protonated brown alga Ecklonia biomass as a model system. Titration of the biomass revealed that it contains at least three types of functional groups. The Fourier transform infrared spectrometry showed that the carboxyl group was the chromium-binding site within the pH range (pH 1-5) used in this study, where chromium does not precipitate. The pK value and the number of carboxyl groups were estimated to be 4.6 +/- 0.1 and 2.2 +/- 0.1 mmol/g, respectively. The equilibrium sorption isotherms determined at different solution pH indicated that the uptake of chromium increased significantly with increasing pH. A model for the description of chromium biosorption was developed incorporating the hydrolysis reactions that chromium undergoes in the aquatic phase. The model was able to predict the equilibrium sorption experimental data at different pH values and chromium concentrations. In addition, the speciation of the binding site as a function of the solution pH was predicted using the model in order to visualize the distribution of chromium ionic species on the binding site.

Vicki H. Grassian, Gerald Meyer, Hector Abruna, Geoffrey W. Coates, Luke Ekem Achenie, TomAllison, Bruce Brunschwig, John Ferry, Miguel Garcia-Garibay, Jorge Gardea-Torresdey, Clare P.Grey, James Hutchison, Chao-Jun Li, Charles Liotta, Arthur Raguskas, Shelley Minteer, Karl Mueller,Jeffrey Roberts, Omowunmi Sadik, Russell Schmehl, William Schneider, Annabella Selloni, Peter Stair,Jon Stewart, David Thorn, Julian Tyson, Bettina Voelker, J. Michael White, and Frankie Wood-Black

Intake fraction (iF), the proportion of emissions inhaled by an exposed population, is useful for prioritizing sources with the greatest impact on population exposure per unit emissions. This article reports iF estimates for urban winter wood smoke emissions. We used two approaches, incorporating spatiotemporal statistical models for (1) winter wood smoke fine particulate matter (PM2.5) emissions and concentration and (2) concentrations of levoglucosan (a wood smoke particulate marker). Empirical data used in our models were measured in Vancouver, Canada during 2004-2005. We used Monte Carlo simulations to quantify uncertainty. The estimated geometric mean iF (units: per million) is 13 (one geometric standard deviation range: 6.6-24) for wood smoke PM2.5 and 15 (4.5-50) for levoglucosan. These iF estimates are comparable to or slightly larger than iF values for urban vehicle emissions reported in the literature. On average, higher-income areas have lower wood smoke PM2.5 concentrations and intake. Our results emphasize the importance of urban wood smoke as a source of PM2.5 exposure and highlight the comparatively large population exposure and potential environmental justice benefits from reducing wood smoke emissions.

Perfluoroalkyl acids (PFAAs) are persistent and bioaccumulative compounds that have been associated with adverse health outcomes. In human blood, PFAAs exist as both linear and branched isomers, yet for most linear homologues, and for all branched isomers, elimination rates are unknown. Paired blood and urine samples (n = 86) were collected from adults in China. They were analyzed by a sensitive isomer-specific method that permitted the detection of many PFAAs in human urine for the first time. For all PFAAs except perfluoroundecanoate (PFUnA), levels in urine correlated positively with levels in blood. Perfluoroalkyl carboxylates (PFCAs) were excreted more efficiently than perfluoroalkane sulfonates (PFSAs) of the same carbon chain-length. In general, shorter PFCAs were excreted more efficiently than longer ones, but for PFSAs, perfluorooctanesulfonate (PFOS, a C8 compound) was excreted more efficiently than perfluorohexanesulfonate (PFHxS, a C6 compound). Among PFOS and perfluorooctanoate (PFOA) isomers, major branched isomers were more efficiently excreted than the corresponding linear isomer. A one-compartment model was used to estimate the biological elimination half-lives of PFAAs. Among all PFAAs, the estimated arithmetic mean elimination half-lives ranged from 0.5 ± 0.1 years (for one branched PFOA isomer, 5m-PFOA) to 90 ± 11 years (for one branched PFOS isomer, 1m-PFOS). Urinary excretion was the major elimination route for short PFCAs (C ≤ 8), but for longer PFCAs, PFOS and PFHxS, other routes of excretion likely contribute to overall elimination. Urinary concentrations are good biomarkers of the internal dose, and this less invasive strategy can therefore be used in future epidemiological and biomonitoring studies. The very long half-lives of long-chain PFCAs, PFHxS, and PFOS isomers in humans stress the importance of global and domestic exposure mitigation strategies.

Precise determination of organophosphate esters (OPEs) in the environment is crucial to estimating their potential toxicity effects on human health. Previous studies have mainly focused on OPEs from direct sources. This study explored a potential indirect source of OPEs: the oxidation of organophosphite antioxidants (OPAs). OPAs are frequently used to retard degradation in polymers through their oxidation to OPEs. In this work, five OPAs [tris(2-chloroethyl) phosphite, triphenyl phosphite, tris(2,4-di- tert-butylphenyl) phosphite, bis(2,4-di- tert-butylphenyl) pentaerythritol diphosphite, and trisnonylphenol phosphite] could be identified, with geometric mean (GM) concentrations from 2.46 to 70.4 ng/g, in indoor dust. Their oxidation products, triisodecyl phosphate (TiDeP), tris(2,4-di- tert-butylphenyl) phosphate (AO168═O), bis(2,4-di- tert-butylphenyl) pentaerythritol diphosphate (AO626═O2), and trisnonylphenol phosphate (TNPP), were found at significantly higher GM concentrations (30.5-3759 ng/g). Surprisingly, two novel oxidation products AO168═O (GM: 3759 ng/g) and TNPP (GM: 2185 ng/g) had higher concentrations than tris(2-chloroethyl) phosphate (GM: 1608 ng/g) and triphenyl phosphate (GM: 1827 ng/g), which are well-known OPEs. These four novel OPEs (TiDeP, TNPP, AO168═O, AO626═O2) contributed 54.1% to the total concentration of the eight OPEs. The present investigation demonstrates that oxidation of OPAs is an important indirect source of novel OPEs in indoor environments. This is the first detection of four OPAs and their newly identified OPE oxidation products in indoor dust.

International audience; We report the results of two complementary studies of the heterogeneous reaction between gas-phase ozone and aqueous chlorophyll. In the first experiment, the chlorophyll is present at the air–water interface and its concentration is measured as a function of time, using laser-induced fluorescence, to obtain the surface kinetics. Under most experimental conditions, these are well described using a Langmuir–Hinshelwood formalism. The second experiment was carried out in a wetted-wall flowtube apparatus and measured the uptake coefficient of ozone by the chlorophyll solution. The uptake coefficient decreases with increasing ozone concentration, consistent with the surface mechanism found in the fluorescence experiment. The two experiments agree that the uptake coefficient for ozone by such chlorophyll samples is ~2–5 × 10−6 with unpolluted boundary layer ozone concentrations. At low wind speed, the reaction between ozone and chlorophyll at the sea surface may represent the driving force for ozone deposition at the ocean surface, significantly increasing its deposition velocity there.

Loadings from Toronto, Canada to Lake Ontario were quantified and major sources and pathways were identified, with the goal of informing opportunities for loading reductions. The contaminants were polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs) and polycyclic musks (PCMs). Loadings were calculated from measured concentrations for three major pathways: atmospheric processes, tributary runoff, and wastewater treatment plant (WWTP) effluents. Although atmospheric deposition to the Great Lakes has received the greatest attention, this was the dominant loading pathway for PCBs only (17 ± 5.3 kg/y or 66% of total loadings). PCB loadings reflected elevated urban PCB air concentrations due to, predominantly, primary emissions. These loadings contribute to consumption advisories for nearshore fish. PBDE loadings to the lake, again from mainly primary emissions, were 48% (9.1 ± 1.3 kg/y) and 42% (8.0 ± 5.7 kg/y) via tributaries and WWTPs, respectively, consistent with emissions deposited and subsequently washed-off of urban surfaces and emissions to the sewage system. PAHs loadings of 1600 ± 280 kg/y (71%) from tributaries were strongly associated with vehicle transportation and impervious surfaces. PCM loadings were 83% (±140 kg/y) from WWTP final effluent, reflecting their use in personal care products. Opportunities for source reduction lie in reducing the current inventories of in-use PCBs and PBDE-containing products, reducing vehicle emissions of PAHs and use of PAHs in the transportation network (e.g., pavement sealants), and improving wastewater treatment technology.

Dramatic changes in molecular structure, degradation pathway, and porosity of biochar are observed at pyrolysis temperatures ranging from 250 to 550 °C when bamboo biomass is pretreated by iron-sulfate-clay slurries (iron-clay biochar), as compared to untreated bamboo biochar. Electron microscopy analysis of the biochar reveals the infusion of mineral species into the pores of the biochar and the formation of mineral nanostructures. Quantitative (13)C nuclear magnetic resonance (NMR) spectroscopy shows that the presence of the iron clay prevents degradation of the cellulosic fraction at pyrolysis temperatures of 250 °C, whereas at higher temperatures (350-550 °C), the clay promotes biomass degradation, resulting in an increase in both the concentrations of condensed aromatic, acidic, and phenolic carbon species. The porosity of the biochar, as measured by NMR cryoporosimetry, is altered by the iron-clay pretreatment. In the presence of the clay, at lower pyrolysis temperatures, the biochar develops a higher pore volume, while at higher temperature, the presence of clay causes a reduction in the biochar pore volume. The most dramatic reduction in pore volume is observed in the kaolinite-infiltrated biochar at 550 °C, which is attributed to the blocking of the mesopores (2-50 nm pore) by the nonporous metakaolinite formed from kaolinite.