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Luca Nizzetto,
Matthew Macleod,
Katrine Borgå,
Ana Cabrerizo,
Jordi Dachs,
Antonio Di Guardo,
Davide Ghirardello, Kaj M Hansen,
Andrew Jarvis,
Anders Lindroth,
Bernard Ludwig,
Donald Monteith,
Judith A Perlinger,
Martin Scheringer,
Luitgard Schwendenmann,
Kirk T Semple,
Lukas Y Wick,
Gan Zhang,
Kevin C Jones
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ABSTRACT: The global distribution of linear and cyclic volatile methyl silxoanes (VMS) was investigated at 20 sites worldwide, including 5 locations in the Arctic, using sorbent-impregnated polyurethane foam (SIP) disk passive air samplers. Cyclic VMS are currently being considered for regulation because they are high production volume chemicals that are potentially persistent, bioaccumulative, and toxic. Linear and cyclic VMS (including L3, L4, L5, D3, D4, D5, and D6) were analyzed for in air at all urban, background, and Arctic sites. Concentrations of D3 and D4 are significantly correlated, as are D5 and D6, which suggests different sources for these two pairs of compounds. Elevated concentrations of D3 and D4 on the West coast of North America and at high elevation sites suggest these sites are influenced by trans-Pacific transport, while D5 and D6 have elevated concentrations in urban areas, which is most likely due to personal care product use. Measured concentrations of D5 were compared to modeled concentrations generated using both the Danish Eulerian Hemispheric Model (DEHM) and the Berkeley-Trent Global Contaminant Fate Model (BETR Global). The correlation coefficients (r) between the measured and modeled results were 0.73 and 0.58 for the DEHM and BETR models, respectively. Agreement between measurements and models indicate that the sources, transport pathways, and sinks of D5 in the global atmosphere are fairly well understood.
Environmental Science & Technology 03/2011; 45(8):3349-54. · 4.80 Impact Factor
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Luca Nizzetto,
Matthew Macleod,
Katrine Borgå,
Ana Cabrerizo,
Jordi Dachs,
Antonio Di Guardo,
Davide Ghirardello, Kaj M Hansen,
Andrew Jarvis,
Anders Lindroth,
Bernard Ludwig,
Donald Monteith,
Judith A Perlinger,
Martin Scheringer,
Luitgard Schwendenmann,
Kirk T Semple,
Lukas Y Wick,
Gan Zhang,
Kevin C Jones
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ABSTRACT: Understanding the legacy of persistent organic pollutants requires studying the transition from primary to secondary source control.
Environmental Science & Technology 09/2010; 44(17):6526-31. · 4.80 Impact Factor
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ABSTRACT: Decamethylcyclopentasiloxane (D(5)) is a volatile compound used in personal care products that is released to the atmosphere in large quantities. Although D(5) is currently under consideration for regulation, there have been no field investigations of its atmospheric fate. We employed a recently developed, quality assured method to measure D(5) concentration in ambient air at a rural site in Sweden. The samples were collected with daily resolution between January and June 2009. The D(5) concentration ranged from 0.3 to 9 ng m(-3), which is 1-3 orders of magnitude lower than previous reports. The measured data were compared with D(5) concentrations predicted using an atmospheric circulation model that included both OH radical and D(5) chemistry. The model was parametrized using emissions estimates and physical chemical properties determined in laboratory experiments. There was good agreement between the measured and modeled D(5) concentrations. The results show that D(5) is clearly subject to long-range atmospheric transport, but that it is also effectively removed from the atmosphere via phototransformation. Atmospheric deposition has little influence on the atmospheric fate. The good agreement between the model predictions and the field observations indicates that there is a good understanding of the major factors governing D(5) concentrations in the atmosphere.
Environmental Science and Technology 07/2010; 44(14):5365-70. · 5.23 Impact Factor
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[show abstract]
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ABSTRACT: Decamethylcyclopentasiloxane (D5) is a volatile compound used in personal care products that is released to the atmosphere in large quantities. Although D5 is currently under consideration for regulation, there have been no field investigations of its atmospheric fate. We employed a recently developed, quality assured method to measure D5 concentration in ambient air at a rural site in Sweden. The samples were collected with daily resolution between January and June 2009. The D5 concentration ranged from 0.3 to 9 ng m−3, which is 1−3 orders of magnitude lower than previous reports. The measured data were compared with D5 concentrations predicted using an atmospheric circulation model that included both OH radical and D5 chemistry. The model was parametrized using emissions estimates and physical chemical properties determined in laboratory experiments. There was good agreement between the measured and modeled D5 concentrations. The results show that D5 is clearly subject to long-range atmospheric transport, but that it is also effectively removed from the atmosphere via phototransformation. Atmospheric deposition has little influence on the atmospheric fate. The good agreement between the model predictions and the field observations indicates that there is a good understanding of the major factors governing D5 concentrations in the atmosphere.
06/2010;
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[show abstract]
[hide abstract]
ABSTRACT: Decamethylcyclopentasiloxane (D5) is a volatile compound used in personal care products that is released to the atmosphere in large quantities. Although D5 is currently under consideration
for regulation, there have been no field investigations of its atmospheric fate. We employed a recently developed, quality assured method to measure D5 concentration in ambient air at a rural site in Sweden. The samples were collected with daily resolution between January and June 2009. The D5 concentration ranged from 0.3 to 9 ng m-3, which is 1-3 orders of magnitude lower than previous reports. The measured
data were compared with D5 concentrations predicted using an atmospheric circulation model that included both OH radical andD5 chemistry. The model was parametrized using emissions estimates and physical chemical properties determined in laboratory experiments. There was good agreement between
the measured and modeled D5 concentrations. The results show that D5 is clearly subject to long-range atmospheric transport,
but that it is also effectively removed from the atmosphere
viaphototransformation.Atmosphericdepositionhaslittleinfluence
on the atmospheric fate. The good agreement between the
model predictions and the field observations indicates that there
is a good understanding of the major factors governing D5
concentrations in the atmosphere.
Environmental Science & Technology 06/2010; 44(14):5365-5370. · 4.80 Impact Factor
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ABSTRACT: A dynamic snowpack module was implemented in the Danish Eulerian Hemispheric Model Persistant Organic Pollutants (DEHM-POP), an atmospheric chemistry-transport model designed to study the environmental fate of persistent organic pollutants in the Northern Hemisphere. The role of the snowpack on the fate of alpha-hexachlorocyclohexane (alpha-HCH) was investigated by making simulations both with and without the formation of a snowpack and comparing model results with data from 21 air monitoring sites. The inclusion of a dynamic snowpack module in the DEHM-POP model generally improves the fit between modeled and observed alpha-HCH air concentrations for the winter and spring seasons and the overall correlation coefficient between predicted and observed concentrations are improved at 8 of the sites. The predicted snowpack concentrations are in good agreement with the few available snow measurements from the Arctic. The presence of a snowpack increases surface boundary layer air concentrations of alpha-HCH at midlatitudes, while the effect is more pronounced in the Arctic due to the longer periods of snow cover. The results indicate that the snowpack module in DEHM-POP acts as a fast-exchanging temporary storage medium for alpha-HCH, as significant fractions were rapidly revolatilized back into the atmosphere following deposition with snowfall, although the current parametrization for vapor-exchange probably over emphasizes this process. Nonetheless, increased air concentrations observed between March and May ("spring maximum events"; SME) at several high latitude monitoring stations are also predicted by the model. The model results indicate that the SMEs are associated with the revolatilization of previously deposited chemical from the snowpack, following a reduction in the capacity of the snowpack to retain alpha-HCH with increasing temperatures toward the end of the winter period, rather than the actual melting of the snowpack. The SMEs are not predicted at all the Arctic monitoring sites by the model, and the significance of the snowpack in controlling these in the model is, therefore, open to question given the uncertainties in the snow-air partition coefficient (K(sa)) and the reliance of the model on a one-layer snowpack rather than a multilayered snowpack.
Environmental Science and Technology 05/2008; 42(8):2943-8. · 5.23 Impact Factor
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ABSTRACT: 1] The POP version of the Danish Eulerian Hemispheric Model (DEHM-POP) is a further development of a 3-D dynamic atmospheric chemistry transport model covering the Northern Hemisphere, which was originally developed to study atmospheric transport of conventional air pollutants and other atmospheric constituents (e.g., SO X , heavy metals, and CO 2). Four different surface compartments (soil, ocean water, vegetation, and snow) are introduced in DEHM-POP with each compartment including the most dominant dynamic processes determining the exchange between air and the surface type to account for the consecutive cycles of deposition and reemission of persistent organic pollutants (POPs). This model setup makes it possible to study short-term atmospheric variability of POPs, which is exemplified in this paper by a study of the atmospheric variability of a-hexachlorocyclohexane (a-HCH), the major component of the worldwide most used insecticide: technical HCH. Simulated a-HCH air concentrations are evaluated against measurements from 21 monitoring stations within the model domain, and the model is able to predict the annual average concentration as well as the long-term trend for the 1990s. Significant correlations between simulated and measured short-term atmospheric concentrations of a-HCH are also found at the majority of the investigated monitoring stations, which shows that it is possible to resolve the atmospheric variability of POPs using an atmospheric chemistry transport model. Differences between simulated and measured atmospheric a-HCH variability can arise because the measurements may be influenced by local features that are not accounted for in the model with the relatively coarse horizontal resolution and surface description. (2008), Modeling short-term variability of a-hexachlorocyclohexane in Northern Hemispheric air, J. Geophys. Res., 113, D02310, doi:10.1029/2007JD008492.
Journal of Geophysical Research 01/2008; 113:D02310. · 3.02 Impact Factor
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ABSTRACT: The evolution in air pollution levels and spatial distribution in the 21st century is investigated with respect to climate
change. The coupled atmosphere- ocean general circulation model ECHAM4-OPYC3 is providing meteorological fields for two time
slices (1990s and 2090s) to the chemical long-range transport model DEHM-REGINA. The dominating impacts from climate change
on a large number of the chemical species are related to the predicted temperature increase since most of the reaction rates
of the involved species are temperature dependent. The ECHAM4-OPYC3 projects a global mean temperature increase of 3 K with
local maxima up to 11 K in the Arctic. As a consequence of this temperature increase, the temperature dependent biogenic emission
of isoprene is predicted to increase significantly over land by the DEHM-REGINA model simulation. This leads to an increase
in the ozone production and together with an increase in water vapour to an increase in the number of free OH radicals. Furthermore
an increase in the number of radicals contributes to a significant change in the typical life times of many species, since
hydroxyl radicals are participating in a large number of chemical reactions.
KeywordsAir pollution-biogenic emissions-chemical transport model-climate change-coupled models-isoprene
12/2007: pages 568-576;
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ABSTRACT: An arctic snow model was developed to predict the exchange of vapor-phase persistent organic pollutants between the atmosphere and the snowpack over a winter season. Using modeled meteorological data simulating conditions in the Canadian High Arctic, a single-layer snowpack was created on the basis of the precipitation rate, with the snow depth, snow specific surface area, density, and total surface area (TSA) evolving throughout the annual time series. TSA, an important parameter affecting the vapor-sorbed quantity of chemicals in snow, was within a factor of 5 of measured values. Net fluxes for fluorene, phenanthrene, PCB-28 and -52, and alpha- and gamma-HCH (hexachlorocyclohexane) were predicted on the basis of their wet deposition (snowfall) and vapor exchange between the snow and atmosphere. Chemical fluxes were found to be highly dynamic, whereby deposition was rapidly offset by evaporative loss due to snow settling (i.e., changes in TSA). Differences in chemical behavior over the course of the season (i.e., fluxes, snow concentrations) were largely dependent on the snow/air partition coefficients (K(sa)). Chemicals with relatively higher K(sa) values such as alpha- and gamma-HCH were efficiently retained within the snowpack until later in the season compared to fluorene, phenathrene, and PCB-28 and -52. Average snow and air concentrations predicted by the model were within a factor of 5-10 of values measured from arctic field studies, but tended to be overpredicted for those chemicals with higher K(sa) values (i.e., HCHs). Sensitivity analysis revealed that snow concentrations were more strongly influenced by K(sa) than either inclusion of wind ventilation of the snowpack or other changes in physical parameters. Importantly, the model highlighted the relevance of the arctic snowpack in influencing atmospheric concentrations. For the HCHs, evaporative fluxes from snow were more pronounced in April and May, toward the end of the winter, providing evidence that the snowpack plays an important role in influencing the seasonal increase in air concentrations for these compounds at this time of year.
Environmental Science and Technology 05/2006; 40(8):2644-52. · 5.23 Impact Factor
