NADP: Keeping You Connected, Issue 2

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 NADP: Keeping You Connected December 2014 | Issue 2 

NADP: Keeping You Connected is a quarterly e-newsletter designed to keep you informed about our changing chemical climate and other updates from the National Atmospheric Deposition Program. To offer feedback or submit a suggestion, please email If you were forwarded this notification and would like to receive future newsletters, click here to subscribe.

In this issue:

NADP Map Highlight

Hybrid Approach to Mapping Total Deposition

   Figure 1. Click to enlarge
Total deposition estimates are derived from summing wet and dry deposition. A Total Deposition Science Committee (TDEP) was formed within NADP in 2011 with a mission to improve estimates of atmospheric deposition by advancing the science of measuring and modeling atmospheric wet, dry, and total deposition of species such as sulfur, nitrogen, and mercury. Members of this multi-agency committee worked to develop a “hybrid approach” to mapping total deposition that combines measured and modeled values. Dry deposition is the deposition of aerosol particles and gases to a solid surface (the ground) through gravitational settling or molecular movement. Measurement of dry deposition is very difficult, so estimates are usually made with modeling techniques.  

One of the initial goals of TDEP is to provide estimates of total sulfur and nitrogen deposition across the U.S. for use in critical loads and other assessments, where loading results in the acidification and eutrophication of ecosystems. Measured values are given more weight at the monitor locations, while modeled data from the Community Multiscale Air Quality (CMAQ) model are used to fill in spatial gaps and provide information on chemical species that are not measured by routine monitoring networks. One of the main advantages to this approach is that it will provide continuous spatial and temporal coverage of total deposition estimates in the U.S. (beginning in 2000), which until this point, has been unavailable.

Figure 2
   Figure 2. Click to enlarge
The first map is the 2013 Dry Deposition of Nitrogen (Figure 1). This is the modeled estimate of non-wet deposition of nitrogen, in the same units and color scheme as figure 2. This comparison shows that dry deposition is much more important in the western parts of the U.S., where wet deposition is less important under these dry climates. Certain locations in the East are important too, given dry periods and contributing N sources. You might also note that some of the same locations are high in both wet and dry deposition.

Figure 3
Figure 3. Click to enlarge

The second map is the 2013 Wet Deposition of Nitrogen (Figure 2). This is analogous to the normal inorganic Nitrogen wet deposition map, but uses a different color ramp. As is clear from the NADP series of maps, wet deposition of inorganic Nitrogen is most prevalent in the Eastern U.S., and heaviest in the Midwest and Northeast (shown by the higher values).

The third map combines the wet and dry maps (Figure 3), again following that total deposition is equal to wet plus dry deposition. Notice that the values at a particular point are larger than both the points in the wet and in the dry deposition map.

NADP Applied Research Highlight

A Global Assessment of Precipitation Chemistry and Deposition

      Figure 4. Click to enlarge
A new global assessment of worldwide precipitation chemistry and deposition was released in the Atmospheric Environment journal in 2014. This assessment, led by Robert Vet and Silvina Carou of Environment Canada, is a major update to the last assessment published in 1996. This assessment provides the global distribution of precipitation composition and deposition of major ions (Figure 4), a more thorough quality assurance review of the available data, and uses the best available global model simulations to fill in global monitoring gaps.

   Figure 5. Click to enlarge
The authors determined that in North America, many of the problems associated with nitrogen and sulfur deposition have been substantially reduced over the past several decades (Figure 2; Figure 3). This is largely due to stringent regulations of air pollutant emissions from electric power plants, industry and automobiles. Canada and the U.S. have reduced the problems associated with chemical deposition in all but the most sensitive ecosystems, such as high elevation forests where soils are thin and easily damaged. But chemical deposition in Asia is at much high levels than in Europe and North America, and is quite extensive over that continent. Little data is available on the continents of Africa and in South America, although high quality programs for measuring wet and dry deposition of major ions are being established in South America and some high quality measurements continue at stations in equatorial Africa and in South Africa.

   Figure 6. Click to enlarge
The assessment also found that ammonium deposition is on the rise globally, particularly in areas with intensive agriculture. We see this pattern quite clearly here in the United States.

This assessment was performed under the auspices of the World Meteorological Organization's Global Atmosphere Watch program. Given our historical record and quality assurance, NADP's data was a major contributor to the resulting assessment.

Publication information:

Robert Vet, Richard S. Artz , Silvina Carou, Mike Shaw, Chul-Un Ro, Wenche Aas, Alex Baker, Van C. Bowersox, Frank Dentener, Corinne Galy-Lacaux, Amy Hou, Jacobus J. Pienaar, Robert Gillett, M. Cristina Forti, Sergey Gromov, Hiroshi Hara, Tamara Khodzher, Natalie M. Mahowald, Slobodan Nickovic, P.S.P. Rao, Neville W. Reid (2014). A global assessment of precipitation chemistry and deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity and pH, and phosphorus. Atmospheric Environment, Volume 93, pages 3-100. doi:10.1016/j.atmosenv.2014.02.017

Student Interest

Students Present Research at the 2014 NADP Scientific Symposium

Students from the University of Illinois at Urbana-Champaign, Purdue University, and the University in São Paulo (Brazil) were among the presenters of research at the recent 2014 NADP Scientific Symposium and Fall Meeting in Indianapolis, Indiana.  Similar to previous years, the symposium planning committee made a special effort to reach out to students to present at the annual meeting. They felt it was an opportunity for students to not only learn what NADP scientists are working on in the field, but also a special opportunity for students to share innovative science research that is happening at the universities with senior scientists from around the country.

Andrew Nelson
   Andrew Nelson, University of Illinois at Urbana-Champaign
Andrew Nelson, a graduate student in the Department of Civil and Environmental Engineering at the University of Illinois at Urbana-Champaign, gave an oral presentation titled Quantifying Bi-Directional Ammonia Flux from Managed Cropland by Relaxed Eddy Accumulation during Technical Session 3 which focused on agricultural emissions and atmospheric deposition. According to the presentation, the use of nitrogen-based fertilizers are estimated to contribute more than 40% of total gaseous ammonia (NH3) emissions in central Illinois based on the Carnegie Melon University model. Andrew's research seeks to address the need for enhanced understanding of agricultural ammonia emission pathways by measuring bi-directional flux of gaseous NH3 over a corn canopy. The abstract for Andrew's presentation is available.

Srinidhi Balasubramanian, University of Illinois at Urbana-Champaign
   Srinidhi Balasubramanian, University of Illinois at Urbana-Champaign
Srinidhi Balasubramanian is also a graduate student in the Department of Civil and Environmental Engineering at the University of Illinois at Urbana-Champaign. She presented a poster at the annual meeting titled Increasing Spatial and Temporal Resolution of Gaseous Ammonia Emissions from Chemical Fertilizer Usage. The poster presented a method and results for increasing spatial and temporal resolution of NH3 emissions from chemical fertilizing usage, which are used as inputs to chemical transport models to estimate particulate matter concentrations and reactive nitrogen deposition. The abstract for Srinidhi's poster is available.

Kan Fu, University of Illinois at Urbana-Champaign
   Kan Fu, University of Illinois at Urbana-Champaign
Another graduate student of the Department of Civil and Environmental Engineering at the University of Illinois at Urbana-Champaign, Kan Fu, also presented a poster at the annual meeting. The poster was titled Preliminary Results from the Weather Research and Forecasting (WRF) model over Midwest USA. This study utilized the WRF model to provide inputs to Chemical Transport Models, which were used to estimate atmospheric particle matter concentrations and reactive nitrogen deposition over Midwest USA. The abstract for Kan's poster is available.

Austin Pearson, Purdue University
   Austin Pearson, Purdue University
Austin Pearson, a graduate student in the Department of Agronomy at Purdue University, presented a poster at the annual meeting titled Variations in Background NH3 Concentrations in Agricultural Regions within the United States. This poster highlighted that the variation in background NH3 concentrations in agricultural regions is of increasing interest due to the difficulty in determining agriculture-specific NH3 emissions. In this study, integrated two week samples of atmospheric NH3 concentrations were obtained from the Ammonia Monitoring Network (AMoN) and measurements of diurnal NH3 concentrations by a Tunable Diode Laser were conducted in June 2014 to determine the annual and diurnal variability in NH3 background concentrations. The abstract for Austin's poster is available.

Marcelo Vieira-Filho, University of São Paulo, Brazil
   Marcelo Vieira-Filho, University of São Paulo, Brazil
Finally, Marcelo Vieira-Filho, a graduate student at the University of São Paulo (Brazil), presented a poster at the annual meeting titled Atmospheric Ammonia Diurnal Variation in an Urban Environment: Case Study Results for São Paulo, Brazil. For the last year, Marcelo was studying abroad with the "Scientists Without Borders" program at the University of Illinois at Urbana-Champaign. The poster discussed how this research aimed to characterize the temporal patterns associated with urban ammonia by evaluating ammonia concentration variability at a street with heavy traffic in a São Paulo summer season from November 9-December 17, 2013. The abstract for Marcelo's poster is available.

Fall 2014 Meeting Highlights

National Atmospheric Deposition Program 2014 Scientific Symposium and Meetings in Indianapolis

   Indianapolis capital Building (Click to enlarge)
Scientists from the United States, Canada, the European Union, and Southeast Asia met in Indianapolis October 21 through 24, 2014 for the annual NADP scientific symposium and technical committee meetings. They shared their discoveries about acid rain; discussed monitoring of mercury in precipitation, the atmosphere, and forests; and presented studies of nitrogen and ammonia in the air, rain, and streams. Science committees met to integrate their knowledge about the global connection of air and water into plans for understanding the status and changes of atmospheric and precipitation chemistry worldwide.

Martin Risch, a research scientist with the U.S. Geological Survey in Indiana, is current chairman of NADP and organized the 4-day event at the Indianapolis Hilton Hotel downtown. "The theme of this year's meeting was The Global Connection of Air and Water", said Risch. The group hosted NASA astronaut and Indianapolis native Dr. David Wolf as their keynote speaker. "As the work of the NADP becomes increasingly international in scope, we felt the perspective of a fellow scientist who had observed the earth's air and water from such a unique outlook would be of great interest and inspiration," said Risch.

   Keynote speaker Dr. David Wolf (Click to enlarge)
Dr. Wolf is a NASA veteran who spent 168 days in space, including 7 spacewalks to build the International Space Station. He is a medical doctor and engineer who contributed inventions and research that significantly improved the understanding of space and the human body. In his presentation to NADP, Dr. Wolf showed how the ground-based monitoring of the NADP connected with NASA's observations from the Space Shuttle, International Space Station, and satellites in earth orbit. He shared videos and commentary of his experiences with the space program and engaged the group in a discussion of future challenges in atmospheric and earth science. Many NADP participants continued conversations with Dr. Wolf during breaks at the symposium.

Risch had high praise about the oral and poster presentations from his fellow scientists. "Speakers at our symposium described the first international synthesis of global precipitation chemistry, new findings about atmospheric mercury from southeastern Asia, the status of ecosystem responses to changes in acid rain in North America, and a study combining NASA observations from space with land-based data that better defines how air pollution affects coastal areas". He said agenda topics included complex computer models, sophisticated scientific instruments, and intricate methods for measuring and analyzing atmospheric pollutants and their transport.

"The NADP meetings have to cover a wide range of topics", Risch commented, "because so many things the modern world does can affect the air, and what's in the air typically returns to earth in the rain or as dry fallout". To illustrate this point, he noted that the meeting had sessions about agricultural emissions, atmospheric mercury deposition, and urban air chemistry. Looking toward the future, scientists will gather to refine methods for calculating the mass of air pollutants deposited to the land in wet and dry forms and to compute a "critical load" or tipping point at which levels of these pollutants begin to damage ecosystems.

   David Gay (left) and Martin Risch (center) with keynote speaker Dr. David Wolf (Click to enlarge)
Dr. David Gay is the coordinator of the NADP Program Office at the University of Illinois, which supports NADP activities, such as managing laboratories, equipment, and data from the networks. "Since our annual scientific meeting was in Indianapolis this year, you may be interested to learn that Indiana has 11 active and historic NADP monitoring sites for acid rain, mercury, and ammonia," he said. "Four of these sites have been in continuous operation, collecting and analyzing precipitation samples for acid rain for over three decades. Monitoring data for mercury in the rain in Indiana extends back to 2000." "Across North America", Dr. Gay observed, "NADP data indicate a steady decline in the amount of sulfur in the rain over the past two decades, documenting the benefits of air pollution regulations. Nitrogen in the rain, originating from many of the same emissions sources as sulfur, has not yet shown the same pattern of decline in NADP monitoring data," he said. "As recent regulations become implemented for emissions of mercury, a toxin that can make some fish unsafe to eat, NADP monitoring will be a source of information about changes in the amounts of mercury in the air, rain, and forests."

More information about the 2014 National Atmospheric Deposition Program scientific symposium, including all abstracts and many of the presentations, are available on the conference web page on the NADP web site. Martin Risch can be contacted at 317-600-2763, Dr. David Gay can be contacted at 217-333-7871,

Recent Publications

A listing of recent journal publications that have used NADP data. Publications are separated by network.

National Trends Network (NTN)

Driscoll, C.T., Fakhraeil, H., Johnson, C., Driscoll, K., 2014. Response of Adirondack Ecosystems to Decreases in Acid Deposition: A roadmap to Recovery? Prepared in advance of a meeting on Acid Rain in the Adirondacks: A Roadmap to Recovery in Saratoga Springs, NY 16 October 2014.

Templer, P. H., Weathers, K. C., Lindsey, A., Lenoir, K., & Scott, L. (2014). Atmospheric inputs and nitrogen saturation status in and adjacent to Class I wilderness areas of the northeastern US. Oecologia, 1-11. November, 2014.

BassiriRad, H., Lussenhop, J. F., Sehtiya, H. L., & Borden, K. K. (2014). Nitrogen deposition potentially contributes to oak regeneration failure in the Midwestern temperate forests of the USA. Oecologia, 1-11. November, 2014.

Clow, D. W., Roop, H. A., Nanus, L., Fenn, M. E., & Sexstone, G. A. (2014). Spatial patterns of atmospheric deposition of nitrogen and sulfur using ion-exchange resin collectors in Rocky Mountain National Park, USA. Atmospheric Environment. Accepted for publication, 12 November 2014.

Hagedorn, B., & Whittier, R. B. (2014). Solute sources and water mixing in a flashy mountainous stream (Pahsimeroi River, US Rocky Mountains): Implications on chemical weathering rate and groundwater surface water interaction. Chemical Geology. January 2015.

Paulot, F., Jacob, D. J., Pinder, R. W., Bash, J. O., Travis, K., & Henze, D. K. (2014). Ammonia emissions in the United States, European Union, and China derived by high-resolution inversion of ammonium wet deposition data: Interpretation with a new agricultural emissions inventory (MASAGE_NH3).Journal of Geophysical Research: Atmospheres, 119(7), 4343-4364.

Mercury Deposition Network (MDN)

Yu, X., Driscoll, C. T., Warby, R. A., Montesdeoca, M., & Johnson, C. E. (2014). Soil mercury and its response to atmospheric mercury deposition across the northeastern United States. Ecological Applications, 24(4), 812-822.

Wright, G., Gustin, M. S., Weiss-Penzias, P., & Miller, M. B. (2014). Investigation of mercury deposition and potential sources at six sites from the Pacific Coast to the Great Basin, USA. Science of The Total Environment,470, 1099-1113.

Atmospheric Mercury Network (AMNet)

Civerolo, K. L., Rattigan, O. V., Felton, H. D., Hirsch, M. J., & DeSantis, S. Mercury Wet Deposition and Speciated Air Concentrations from Two Urban Sites in New York State: Temporal Patterns and Regional Context. Aerosol and Air Quality Research, 14: 1822-1837, 2014

McClure, C. D., Jaffe, D. A., & Edgerton, E. S. (2014). Evaluation of the KCl Denuder Method for Gaseous Oxidized Mercury using HgBr2 at an In-Service AMNet Site. Environmental science & technology, 48(19), 11437-11444.