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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. Source


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). Source


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. Source


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 4 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. Source


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. Source

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