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Shanley J.B.,U.S. Geological Survey | Engle M.A.,U.S. Geological Survey | Scholl M.,U.S. Geological Survey | Krabbenhoft D.P.,U.S. Geological Survey | And 3 more authors.
Environmental Science and Technology | Year: 2015

Atmospheric mercury deposition measurements are rare in tropical latitudes. Here we report on seven years (April 2005 to April 2012, with gaps) of wet Hg deposition measurements at a tropical wet forest in the Luquillo Mountains, northeastern Puerto Rico, U.S. Despite receiving unpolluted air off the Atlantic Ocean from northeasterly trade winds, during two complete years the site averaged 27.9 μg m-2 yr-1 wet Hg deposition, or about 30% more than Florida and the Gulf Coast, the highest deposition areas within the U.S. These high Hg deposition rates are driven in part by high rainfall, which averaged 2855 mm yr-1. The volume-weighted mean Hg concentration was 9.8 ng L-1, and was highest during summer and lowest during the winter dry season. Rainout of Hg (decreasing concentration with increasing rainfall depth) was minimal. The high Hg deposition was not supported by gaseous oxidized mercury (GOM) at ground level, which remained near global background concentrations (<10 pg m-3). Rather, a strong positive correlation between Hg concentrations and the maximum height of rain detected within clouds (echo tops) suggests that droplets in high convective cloud tops scavenge GOM from above the mixing layer. The high wet Hg deposition at this "clean air" site suggests that other tropical areas may be hotspots for Hg deposition as well. © 2015 American Chemical Society.


Duan F.,Frontier Global Sciences
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2015

This paper investigated the performance of sustainability of a conceptual offshore platform that integrated renewable energy utilization and microalgae bio-fuel production in East China Sea. Triple I light (III light), which is calculated based on ecological footprint, bio-capacity, cost and benefit, was introduced to evaluate the economic together with environmental impacts. The assessment results for an assumed scenario suggested the sustainability of the conceptual system. The environmental effect and the economic impact played almost the same role in the assessment results. In the meanwhile, the non energy production dominated the system performance. Copyright © 2015 by the International Society of Offshore and Polar Engineers (ISOPE).


Sather M.E.,U.S. Environmental Protection Agency | Mukerjee S.,National Exposure Research Laboratory | Smith L.,Alion Science and Technology Corporation | Mathew J.,Houston Laboratory | And 10 more authors.
Atmospheric Pollution Research | Year: 2013

Gaseous oxidized mercury (GOM) dry deposition measurements using surrogate surface passive samplers were collected in the Four Corners area and eastern Oklahoma from August, 2009-August, 2011. Using data from a six site area network, a characterization of the magnitude and spatial extent of ambient mercury pollution in the arid Four Corners area was accomplished, which included the observation of a strong regional signature in the GOM dry deposition data set. GOM dry deposition rate estimates ranged from 0.4-1.0 ng/m2 h at the six Four Corners area monitoring sites, while the GOM dry deposition rate estimate at the eastern Oklahoma monitoring site was lower at 0.2 ng/m2 h. The highest GOM dry deposition estimates were recorded during the spring and summer while the lowest GOM dry deposition estimates were recorded during the fall and winter. During the second year of this study the highest annual GOM dry deposition estimate so far measured in the United States (U.S.) with smooth-edge surrogate surface passive samplers, 10 889 ng/m2, was recorded at the Mesa Verde National Park site, a site at which the two-year cumulative GOM dry deposition estimate exceeded the mercury wet deposition estimate. GOM dry deposition estimates during the second year of the study were statistically significantly higher than the first year of the study at six of the seven sites. The data from this study provide a two-year baseline of GOM dry deposition data in the Four Corners area and eastern Oklahoma immediately before the current implementation of new U.S. power plant and boiler mercury control regulations which will significantly reduce mercury emissions from those two sectors of local and regional anthropogenic mercury emission sources. © Author(s) 2012.


Lamarque J.-F.,U.S. National Center for Atmospheric Research | Shindell D.T.,NASA | Josse B.,French National Center of Weather Research | Young P.J.,University of Colorado at Boulder | And 30 more authors.
Geoscientific Model Development | Year: 2013

The Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) consists of a series of time slice experiments targeting the long-term changes in atmospheric composition between 1850 and 2100, with the goal of documenting composition changes and the associated radiative forcing. In this overview paper, we introduce the ACCMIP activity, the various simulations performed (with a requested set of 14) and the associated model output. The 16 ACCMIP models have a wide range of horizontal and vertical resolutions, vertical extent, chemistry schemes and interaction with radiation and clouds. While anthropogenic and biomass burning emissions were specified for all time slices in the ACCMIP protocol, it is found that the natural emissions are responsible for a significant range across models, mostly in the case of ozone precursors. The analysis of selected present-day climate diagnostics (precipitation, temperature, specific humidity and zonal wind) reveals biases consistent with state-of-the-art climate models. The model-to-model comparison of changes in temperature, specific humidity and zonal wind between 1850 and 2000 and between 2000 and 2100 indicates mostly consistent results. However, models that are clear outliers are different enough from the other models to significantly affect their simulation of atmospheric chemistry. © Author(s) 2013. CC Attribution 3.0 License.


Yim S.,Korea Advanced Institute of Science and Technology | Sim D.M.,Korea Advanced Institute of Science and Technology | Park W.I.,Global Frontier R and nter for Hybrid Interface Materials Busandaehak ro 63beon gil Geumjeong gu | Choi M.-J.,Korea Advanced Institute of Science and Technology | And 4 more authors.
Advanced Functional Materials | Year: 2016

Precise modulation of electrical and optical properties of 2D transition metal dichalcogenides (TMDs) is required for their application to high-performance devices. Although conventional plasma-based doping methods have provided excellent controllability and reproducibility for bulk or relatively thick TMDs, the application of plasma doping for ultrathin few-layer TMDs has been hindered by serious degradation of their properties. Herein, a reliable and universal doping route is reported for few-layer TMDs by employing surface-shielding nanostructures during a plasma-doping process. It is shown that the surface-protection oxidized polydimethylsiloxane nanostructures obtained from the sub-20 nm self-assembly of Si-containing block copolymers can preserve the integrity of 2D TMDs and maintain high mobility while affording extensive control over the doping level. For example, the self-assembled nanostructures form periodically arranged plasma-blocking and plasma-accepting nanoscale regions for realizing modulated plasma doping on few-layer MoS2, controlling the n-doping level of few-layer MoS2 from 1.9 × 1011 cm-2 to 8.1 × 1011 cm-2 via the local generation of extra sulfur vacancies without compromising the carrier mobility. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Sather M.E.,U.S. Environmental Protection Agency | Mukerjee S.,National Exposure Research Laboratory | Allen K.L.,U.S. Environmental Protection Agency | Smith L.,Alion Science and Technology Corporation | And 11 more authors.
The Scientific World Journal | Year: 2014

Gaseous oxidized mercury (GOM) dry deposition measurements using aerodynamic surrogate surface passive samplers were collected in central and eastern Texas and eastern Oklahoma, from September 2011 to September 2012. The purpose of this study was to provide an initial characterization of the magnitude and spatial extent of ambient GOM dry deposition in central and eastern Texas for a 12-month period which contained statistically average annual results for precipitation totals, temperature, and wind speed. The research objective was to investigate GOM dry deposition in areas of Texas impacted by emissions from coal-fired utility boilers and compare it with GOM dry deposition measurements previously observed in eastern Oklahoma and the Four Corners area. Annual GOM dry deposition rate estimates were relatively low in Texas, ranging from 0.1 to 0.3 ng/m2h at the four Texas monitoring sites, similar to the 0.2 ng/m2h annual GOM dry deposition rate estimate recorded at the eastern Oklahoma monitoring site. The Texas and eastern Oklahoma annual GOM dry deposition rate estimates were at least four times lower than the highest annual GOM dry deposition rate estimate previously measured in the more arid bordering western states of New Mexico and Colorado in the Four Corners area. © 2014 Mark E. Sather et al.


PubMed | U.S. Geological Survey, University of Vermont, Frontier Global Sciences and University of Illinois at Urbana - Champaign
Type: Journal Article | Journal: Environmental science & technology | Year: 2015

Atmospheric mercury deposition measurements are rare in tropical latitudes. Here we report on seven years (April 2005 to April 2012, with gaps) of wet Hg deposition measurements at a tropical wet forest in the Luquillo Mountains, northeastern Puerto Rico, U.S. Despite receiving unpolluted air off the Atlantic Ocean from northeasterly trade winds, during two complete years the site averaged 27.9 g m(-2) yr(-1) wet Hg deposition, or about 30% more than Florida and the Gulf Coast, the highest deposition areas within the U.S. These high Hg deposition rates are driven in part by high rainfall, which averaged 2855 mm yr(-1). The volume-weighted mean Hg concentration was 9.8 ng L(-1), and was highest during summer and lowest during the winter dry season. Rainout of Hg (decreasing concentration with increasing rainfall depth) was minimal. The high Hg deposition was not supported by gaseous oxidized mercury (GOM) at ground level, which remained near global background concentrations (<10 pg m(-3)). Rather, a strong positive correlation between Hg concentrations and the maximum height of rain detected within clouds (echo tops) suggests that droplets in high convective cloud tops scavenge GOM from above the mixing layer. The high wet Hg deposition at this clean air site suggests that other tropical areas may be hotspots for Hg deposition as well.


PubMed | Cherokee Nation Environmental Programs, Houston Laboratory, National Exposure Research Laboratory, Frontier Global Sciences and 2 more.
Type: | Journal: TheScientificWorldJournal | Year: 2014

Gaseous oxidized mercury (GOM) dry deposition measurements using aerodynamic surrogate surface passive samplers were collected in central and eastern Texas and eastern Oklahoma, from September 2011 to September 2012. The purpose of this study was to provide an initial characterization of the magnitude and spatial extent of ambient GOM dry deposition in central and eastern Texas for a 12-month period which contained statistically average annual results for precipitation totals, temperature, and wind speed. The research objective was to investigate GOM dry deposition in areas of Texas impacted by emissions from coal-fired utility boilers and compare it with GOM dry deposition measurements previously observed in eastern Oklahoma and the Four Corners area. Annual GOM dry deposition rate estimates were relatively low in Texas, ranging from 0.1 to 0.3 ng/m(2)h at the four Texas monitoring sites, similar to the 0.2 ng/m(2)h annual GOM dry deposition rate estimate recorded at the eastern Oklahoma monitoring site. The Texas and eastern Oklahoma annual GOM dry deposition rate estimates were at least four times lower than the highest annual GOM dry deposition rate estimate previously measured in the more arid bordering western states of New Mexico and Colorado in the Four Corners area.


News Article | January 24, 2011
Site: techcrunch.com

A new study published today by the nonprofit Center for Consumer Freedom (CCF) based on testing done by Frontier Global Sciences in Seattle, found that many reusable bags sold by major U.S. retailers today contain unsafe amounts of lead. The CCF advertises itself as a force against the “nanny-state,” and advocates for “consumer freedom.” They also appear to argue that food, beverage and restaurant businesses should be able to do, sell and give away whatever the heck they please, never mind the environmental or social consequences. Frontier Global Sciences is a privately held business that provides environmental sampling and analysis services. “Of the 44 organizations whose bags were tested, 16 are selling or distributing reusable bags containing lead in amounts greater than 100 ppm (parts per million), which is where many states set the limit for heavy metals in packaging… National chains such as CVS, Safeway, Bloom, and Walgreens were among those with high levels of lead found in their reusable bags. CVS and Safeway led the pack with 697 and 672 ppm respectively; both were nearly seven times the 100 ppm limit. To date, CVS is the only store that tested above 100 ppm to have recalled their bags. Previously lululemon athletica, Sears-Canada, and Wegmans have all recalled bags due to high levels of lead. Retailers testing positive for excessive levels of lead included Staples, Giant Eagle, Piggly Wiggly, Giant, Gerbes, KTA Superstore, Brookshire Brothers, Stater Bros., and, ironically, the District of Columbia Department of Environment.” In a press statement CCF senior research analyst J. Justin Wilson says “retailers were goaded into selling these bags” by environmentalists. He also suggests that banning stores from giving away, and enabling the pervasive consumption of disposable, non-biodegradable plastic bags inevitably results in stores selling cheap, unsafe reusable goods. It’s hard to believe the bans on plastic bags — from China and Italy to multiple U.S. cities— are causing more harm than good, however. Consider the magnitude of plastic, single-use bag waste in recent years: in Europe, an estimated 100 billion disposable plastic bags are used annually, according to the green blog Environmental Leader. Meanwhile, the San Jose Mercury News reports, in the U.S. only 13 percent of recyclable, non-biodegradable plastic bags actually get recycled each year. Until tech and design innovators, or groups like PopTech’s Ecomaterials Innovation Lab and the Sustainable Packaging Coalition can devise a zero-impact single use bag, concerned shoppers with any environmental awareness should probably opt to bring their own, lead free reusables. It’s even possible to make one out of old school plastic disposables, or buy one made of safe, and recycled materials from a specialty web store like ReuseIt.com or One Bag at a Time (hat tip: Ecosalon).

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