Contribution of Volatile Precursor Substances to the Flux of Perfluorooctanoate to the Arctic

Schenker, U.; Scheringer, M.; MacLeod, M.; Martin, J.W.; Cousins, I.T.; Hungerbühler, K.
2008 | Environ. Sci. Technol. | 42 (3710-3716)

Dependence of persistence and long-range transport potential on gas-particle partitioning in multimedia models

Gotz, C.W.; Scheringer, M.; MacLeod, M.; Wegmann, F.; Schenker, U.; Hungerbuhler, K.
2008 | Environ. Sci. Technol. | 42 (10) (3690-3696)

A novel approach of modeling gas-particle partitioning using polyparameter linear free energy relationships (ppLFERs) is implemented into three different multimedia box models (the OECD Pov and LRTP screening tool (The Tool), ChemRange, and CliMoChem) and compared to approaches based on the octanol-air partition coefficient (K-OA). In all three multimedia models, calculated overall persistence is not strongly influenced (differences <3%) by the gas-particle partitioning approach selected. The long-range transport potential (LRTP) is more sensitive to the choice of the gas-particle partitioning model. In CliMoChem,the LRTP of polarchemicals is higher if the ppLFER gas-particle partitioning approach is applied, with differences up to a factor of 2. Modeled concentrations of polar chemicals in Arctic air are also higher in the ppLFER version of CliMoChem. The model results obtained with the ppLFER approach are in good agreement with measured concentrations of alpha-HCH, methoxychlor, and trifluralin in Arctic air, whereas results from the K-OA-based version of the model are in some cases lower by a factor of 10-100. If the required chemical property data are available, the ppLFER approach holds considerable potential to improve the gas-particle partitioning description for polar chemicals in multimedia models.

Modelling the long-term fate and transport of PFO(A) emitted from direct sources using a two-dimensional global-scale model

2008 | Organohalogen Compd. | 70 (1438-1441)

Measurement and modeling of diel variability of polybrominated dipbenyl ethers and chlordanes in air

Moeckel, C.; MacLeod, M.; Hungerbuhler, K.; Jones, K.C.
2008 | Environ. Sci. Technol. | 42 (9) (3219-3225)

Short-term variability of concentrations of polybrominated diphenyl others (PBDEs) and chlordanes in air at a semirural site in England over a 5 day period is reported. Four-hour air samples were collected during a period dominated by a high pressure system that produced stable diel (24-h) patterns of meteorological conditions such as temperature and atmospheric boundary layer height. PBDE and chlordane concentrations showed Clear diel variability with concentrations in the afternoon and evening being 1.9 - 2.7 times higher than in the early morning. The measurements are interpreted using a multimedia mass balance model parametrized with forcing functions representing local temperature, atmospheric boundary layer height, wind speed and hydroxyl radical concentrations. Model results indicate that reversible, temperature-controlled air-surface exchange is the primary driver of the diel concentration pattern observed for chlordanes and PBDE 28. For higher brominated PBDE congeners (47, 99 and 100), the effect of variable atmospheric mixing height in combination with irreversible deposition on aerosol particles is dominant, and explains the diel patterns almost entirely. Higher concentrations of chlordanes and PBDEs in air observed at the end of the study period could be related to likely source areas using back trajectory analysis. This is the first study to clearly document diel variability in concentrations of PBDEs in air over a period of several days. Our model analysis indicates that high daytime and low nighttime concentrations of semivolatile organic chemicals can arise from different underlying driving processes, and are not necessarily evidence of reversible air-surface exchange on a 24-h time scale.

Regional differences in gas-particle partitioning and deposition of semivolatile organic compounds on a global scale

Gotz, C.W.; Scheringer, M.; MacLeod, M.; Wegmann, F.; Hungerbuhler, K.
2008 | Atmos. Environ. | 42 (3) (554-567)

Variability in gas-particle partitioning of semivolatile organic compounds (SOCs) and related atmospheric processes (particle-associated deposition, rain washout and degradation) are investigated on a global scale. Two different sorption approaches (one using the octanol-air partition coefficient, K-OA, and one based on poly-parameter linear free energy relationships, ppLFER) and two different atmospheric box models (unit-world and highly spatially and temporally resolved) are applied. In the unit-world model, the overall deposition and atmospheric fate of SOCs calculated with the K-OA-based sorption approach are similar to the ones calculated with the ppLFER approach. Rain washout dominates the atmospheric removal of polar chemicals in the unit-world model while non-polar chemicals are removed mainly through degradation or particle-associated deposition. In contrast, big differences and a high sensitivity to the selected sorption approach are found in the spatially and temporally resolved model. The highly resolved geographic variability cannot be represented using the KOA-based approach if aerosol components other than OM are of importance for sorption. In particular, aerosols in dry regions (desert) and regions with low OM aerosols (arctic, some oceanic regions) are more appropriately described by the ppLFER approach. With the ppLFER approach, good agreement between modeled deposition fluxes and measurement data are found for higher chlorinated PCBs and TCDD/Fs. In general, we recommend the ppLFER approach for highly resolved environmental fate models. (C) 2007 Elsevier Ltd. All rights reserved.

Estimation of cumulative aquatic exposure and risk due to silver: Contribution of nano-functionalized plastics and textiles

Blaser, S.A.; Scheringer, M.; MacLeod, M.; Hungerbuhler, K.
2008 | Sci. Total Environ. | 390 (2-3) (396-409)

Products with antimicrobial effect based on silver nanoparticles are increasingly used in Asia, North America and Europe. This study presents an analysis of risk to freshwater ecosystems from silver released from these nanoparticles incorporated into textiles and plastics. The analysis is presented in four stages; (i) silver mass flow analysis and estimation of emissions, (ii) assessment of the fate of silver in a river system and estimation of predicted environmental concentrations (PECS), (iii) critical evaluation of available toxicity data for environmentally relevant forms of silver and estimation of predicted no-effect concentrations (PNECs), and (iv) risk characterization. Our assessment is based on estimated silver use in the year 2010, focusing on the Rhine river as a case study. In 2010, biocidal plastics and textiles are predicted to account for up to 15% of the total silver released into water in the European Union. The majority of silver released into wastewater is incorporated into sewage sludge and may be spread on agricultural fields. The amount of silver reaching natural waters depends on the fraction of wastewater that is effectively treated. Modeled PECS in the Rhine river are in satisfactory agreement with monitoring data from other river systems. Because a complete characterization of the toxicity of environmentally relevant silver species is lacking, only a limited risk assessment is possible at this time. However, our study indicates that PEC/PNEC ratios greater than 1 cannot be ruled out for freshwater ecosystems, in particular sediments. No risk is predicted for microbial communities in sewage treatment plants. (c) 2007 Elsevier B.V. All rights reserved.

Estimating enthalpy of vaporization from vapor pressure using Trouton’s rule

MacLeod, M.; Scheringer, M.; Hungerbuhler, K.
2007 | Environ. Sci. Technol. | 41 (8) (2827-2832)

The enthalpy of vaporization of liquids and subcooled liquids at 298 K (Delta H-VAP(o)) is an important parameter in environmental fate assessments that consider spatial and temporal variability in environmental conditions. It has been shown that Delta H-VAP(o) for non-hydrogen-bonding substances can be estimated from vapor pressure at 298 K (P-L(o)) using an empirically derived linear relationship. Here, we demonstrate that the relationship between Delta H-VAP(o) and P-L(o) is consistent with Trouton's rule and the Clausius-Clapeyron equation under the assumption that Delta H-VAP(o) is linearly dependent on temperature between 298 K and the boiling point temperature. Our interpretation based on Trouton's rule substantiates the empirical relationship between Delta H-VAP(o) and P-L(o) for non-hydrogen-bonding chemicals with subcooled liquid vapor pressures ranging over 15 orders of magnitude. We apply the relationship between Delta H-VAP(o) and P-L(o) to evaluate data reported in literature reviews for several important classes of semivolatile environmental contaminants, including polycyclic aromatic hydrocarbons, chlorobenzenes, polychlorinated biphenyls and polychlorinated dibenzo-dioxins and -furans and illustrate the temperature dependence of results from a multimedia model presented as a partitioning map. The uncertainty associated with estimating Delta H-VAP(o) from P-L(o) using this relationship is acceptable for most environmental fate modeling of non-hydrogen-bonding semivolatile organic chemicals.

Alternative approaches for modeling gas-particle partitioning of semivolatile organic chemicals: Model development and comparison

Gotz, C.W.; Scheringer, M.; MacLeod, M.; Roth, C.M.; Hungerbuhler, K.
2007 | Environ. Sci. Technol. | 41 (4) (1272-1278)

We present a novel model of gas-particle partitioning based on polyparameter linear free energy relationships (ppLFERs) that is capable of representing a broad range of aerosol properties. We apply the model to semivolatile organic chemicals including PCBs, DDT, and polar pesticides, and compare it to a widely adopted model based on the octanol-air partition coefficient (K-OA). For nonpolar chemicals and cases where sorption to aerosols is dominated by absorption into organic matter, the two models are highly correlated and both are appropriate. Significant differences between the models are found for (a) polar chemicals and (b) aerosols with low organic matter content. The explicit description of polar interactions in the ppLFER approach implies stronger interactions between chemicals and aerosols than the K-OA-based model, which describes polar interactions only implicitly and to a limited extent. Practical application of the ppLFER-based model to a wide range of chemicals is currently limited by data gaps in measured Abraham solvation parameters and uncertainties in estimation methods.

Modelling the fate and transport of PFCAs emitted from direct sources using a global-scale chemical fate model.

Armitage, J.M.; Cousins, I.T.; Prevedouros, K.; MacLeod, M.; Russell, M.H.; Buck, R.C.

SETAC North America 28th Annual Meeting, in Milwaukee, Wisconsin, USA | February 3, 2023

The origin and significance of short-term variability of semivolatile contaminants in air

MacLeod, M.; Scheringer, M.; Podey, H.; Jones, K.C.; Hungerbuhler, K.
2007 | Environ. Sci. Technol. | 41 (9) (3249-3253)

Persistent semivolatile contaminants such as polychlorinated biphenyls (PCBs) cycle between air and surface media in the environment. At different locations and times, PCB concentrations in air over a diel (24-hour) period have been observed to have maxima either during the day or at night. These observations have been interpreted as evidence of temperature-mediated air-surface exchange and of degrading reactions with hydroxyl radicals in the atmosphere. However, a general explanation of the processes responsible for the observed diel variability in concentrations has not been provided. Here, we interpret diel monitoring data using a multimedia mass balance model parametrized with local data on temperature, wind speed, atmospheric mixing height, and hydroxyl radical concentrations. We demonstrate that four factors are sufficient to account for the variability of PCB concentrations in air over a diel period; temperature, local atmospheric stability, hydroxyl radical concentration, and source type. We apply the model to re-interpret past diel monitoring studies and find that the observed patterns of concentrations can be rationalized by consideration of these factors. Using insights from this study, future diel monitoring campaigns can be targeted to observe the influence of specific fate and transport processes. Such studies will contribute to more accurate understanding of the processes controlling the shortterm local, and long-term global fate of persistent semivolatile contaminants.

Modeling Global-Scale Fate and Transport of Perfluorooctanoate Emitted from Direct Sources

Armitage, J.M.; Cousins, I.T.; Prevedouros, K.; MacLeod, M.; Russell, M.H.; Buck, R.C.
2006 | Environ. Sci. Technol. | 40 (6969-6975)

Modeling Global-Scale Fate and Transport of Perfluorooctanoate Emitted from Direct Sources

Armitage, J.M.; Prevedouros, K.; Cousins, I.T.; MacLeod, M.; Buck, R.C.; Russell, M.; Korzeniowski, S.
2006 | Environ. Sci. Technol. | 40 (6969-6975)

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