NADP: Keeping You Connected, Issue 7

Why is Total Deposition Important?

Most people in NADP spend the majority of their time sampling wet deposition in the National Trends Network (NTN) and Mercury Deposition Network (MDN), and NADP has provided these data for nearly 40 years. Wet deposition is the absorption of atmospheric pollutants into precipitation droplets, followed by the droplet removal via precipitation and fog. NADP is best known for these measurements. A large subset of NADP members and data users are increasingly concerned with total deposition, the combination of both wet and dry deposition (Figure 1). Dry deposition is the uptake of atmospheric gases and particles by soil, water, vegetation, or snow on the earths’ surface without precipitation. Total deposition is becoming more of a concern to many scientists, inside and outside of NADP. NADP has therefore been expanding to incorporate total deposition through the recent addition of two networks, the Atmospheric Mercury Network (AMNet) and the Ammonia Monitoring Network (AMoN). NADP also now has two separate scientific committees focused on the total deposition of atmospheric pollutants and its effects.

Figure 1: Click to enlarge

The Total Deposition Science Committee (TDEP) was formed in 2011 with a mission to improve estimates of total atmospheric deposition by advancing the science of measuring and modeling atmospheric wet, dry, and the combined deposition of pollutants. In 2006, the Critical Loads of Atmospheric Deposition Science Committee (CLAD) was initiated. CLAD’s purpose is to advance the science and use of critical loads in the United States to support policy and land management decision-making related to the effects of total atmospheric deposition on ecosystems. These two committees complement each other: TDEP works to improve estimates of total deposition, while CLAD uses this information to estimate the impacts of deposition on ecosystems.

Membership on both committees includes academic and agency scientists from Federal and State management and regulatory agencies, and NADP operators.

TDEP is using a combined measurement and modeling approach to estimate total nitrogen and sulfur deposition to the contiguous U.S. This work culminated in a recent journal article (Schwede & Lear, 2015) that was highlighted in the December 2014 NADP Newsletter and is summarized by the TDEP fact sheet. It is important to note that measurement data from several networks besides NADP went into these estimates of total deposition (see Table 1).

Figure 2. Click to enlarge

CLAD has also been using a variety of modeled and empirical data to make a series of critical load maps. These maps display estimates of the maximum amount of a particular pollutant that an ecosystem or species can be exposed to before experiencing negative effects. In order to determine when ecosystem effects are occurring, critical loads are compared against total deposition estimates. CLAD and critical loads were highlighted in the August 2015 newsletter. Much of the committee’s work was summarized in a recent journal publication (Blett et al., 2014) and the recently published 2015 Summary of Critical Load Maps. This new summary is available for download at the NADP website, and printed versions are available from the Program Office. CLAD plans for this summary to be an ongoing NADP publication.

Future Direction

At the 2016 Spring NADP meeting, TDEP reported on accomplishments to date and a work plan for the future, which includes developing estimates of total mercury deposition. Dr. Leiming Zhang of Environment Canada is currently modeling dry mercury deposition at AMNet sites. This estimate will be combined with wet deposition measurements to estimate total mercury deposition at sites with AMNet and MDN monitors. The NADP Executive Committee renewed the TDEP Science Committee for another four years. TDEP will continue to support CLAD and provide the best available estimates of total deposition for determining critical load exceedances.

The Increasing Importance of Deposition of Reduced Nitrogen in the United States

A recently released journal article in the Proceedings of the National Academy of Sciences (PNAS) discusses the total deposition of nitrogen in the atmosphere and the changes in its composition since 1990. The paper evaluates the summed deposition of both nitrate (NO₃^-) and ammonium (NH₄⁺) ions, which NADP represents as the total wet deposition of inorganic nitrogen. This study takes an interesting view of the issue, focusing not on the total deposition amounts exclusively, but rather the relative contributions from NO₃^- versus NH₄⁺ and their relative change over time. The manuscript illustrates that nitrogen wet deposition was clearly dominated by NO₃^- during the early 1990s (see Figure 3). However, over time, with reductions in NO₃^- emissions across the United States under the 1990 Clean Air Act Amendments and related legislation, total nitrogen deposition is now dominated by reduced nitrogen over much of the country, particularly throughout the central U.S. In the Northeast and much of the Southeast, the contribution of nitrogen is roughly equal parts from NO₃^- and NH₄⁺. NO₃^- wet deposition now dominates only in regions of the Pacific Northwest, the interior Rocky Mountains, and in Florida. The authors note similar changes in the relative contributions of ammonium and nitrate based species in dry deposition, but this conclusion is somewhat limited by the fewer observations that are available as compared to wet deposition.

Figure 3. Click to enlarge

EPA’s Progress Reports have been an important tool for communicating information from long-term environmental and emissions monitoring programs. Combined with agency programmatic data, EPA evaluates the progress of emission reduction programs and shows the combined effects of agency programs on power sector emissions of SO₂, NO_x, ozone and fine particles (PM_2.5). Recent highlights are described below.

The authors attribute the change in relative contributions of nitrogen species to the growth of agriculture (i.e., increasing ammonia emissions) and successful control of nitrogen oxides emission over the previous 30 years. Expanded observations of reduced nitrogen species have allowed for the observation of this nitrogen shift from a NO₃^--dominated to an NH₄⁺-dominated condition.

Dr. Yi Li, the lead author of the study, who now works for the state of Arizona, notes the implications of these changes is related to increase of ammonia (NH₃) emissions in last decades. Compared to nitrogen oxides (NO_x), NH₃ has received less attention and is not currently a nationally-regulated air emission. The principal sources of NH₃ in rural areas are from agricultural activities. The findings emphasize the important contribution of NH₃ not only in the wet nitrogen deposition but also dry deposition.

This study illustrates an innovative use of the NADP data, both from the National Trends Network (NTN) and the Ammonia Monitoring Network (AMoN). This study combined NTN and AMoN data with observational data from other national networks, including the Clean Air Status and Trends Network (CASTNET) and the Interagency Monitoring of Protected Visual Environments (IMPROVE) network. These networks are supported by multiple federal agencies, including the U.S. EPA, the National Park Service, and the Bureau of Land Management.

Reference:

Yi Li, Bret A. Schichtel, John T. Walker, Donna B. Schwede, Xi Chen, Christopher M. B. Lehmann, Melissa A. Puchalski, David A Gay, and Jeffrey L. Collett Jr., 2016. Increasing importance of deposition of reduced nitrogen in the United States. PNAS 113 (21) 5874-5879; doi:10.1073/pnas.1525736113

The Impact of the National Atmospheric Deposition Program

The Multistate Research Program created an Impact Statement for the NADP highlighting the program’s impacts as a National Research Support Project (NRSP) from 2009-2014. The report provides an overview of NADP, as well as how NADP data have helped advance research on many topics including ecosystems, agriculture, air quality, and climate change. View the full Impact Report here.

Operator Corner

NADP sites are located across a variation of elevations, climates, and surrounding conditions, sometimes resulting in interesting stories from the operators that run the site. Here are some brief “Operator Corner” highlights that NADP has collected.

Our Youngest Site Operator

	Sampling must go on, even on days when the babysitter is sick. The CO94 operator’s son had some fun helping his mom with a bucket change in March 2016 (Figure 4). She said he really enjoyed watching the collector open and close!
Figure 4. Click to enlarge

8-Mile Snowmobile Ride

Figure 5. Click to enlarge	Figure 6. Click to enlarge

At just over 10,610 feet (3,234 meters) elevation, CO97 is one of the highest elevation sites and can sometimes be a challenge to get to thanks to deep snowfall. It is an 8-mile snowmobile ride from the trailhead to the Continental Divide (Figure 5), where the Forest Service operates the CO97 site (Figure 6). On a normal day, it’s a half-hour ride while on the worst days, it could take three to four hours due to the snowmobiles getting stuck and having to dig them out. During peak season, the road to the top is groomed for the public, but a storm could come through between fresh grooms, so it is not always known whether they will be riding in powder or a groomed trail.

Wildfire Close Call

In 2011, NM08 was in the process of setting up an electronic rain gage when a 25,000-acre wildfire burnt right through nearby locations. Luckily, the fire did not hurt the site, but the destruction outside the fence was extensive. The site operator could fortunately keep an eye on the fire around the site because she is a smoke jumper who was assigned to battle this fire.

Pesky Winter

Figure 7. Click to enlarge	Figure 8. Click to enlarge

Winter weather can be a challenge for many NADP sites. OK06 and WY98 recently sent in photos of their winter encounters, which included a sudden ice storm and large snowstorm. The sudden ice storm impacted OK06 in January 2016, and the site was inaccessible for several days (Figure 7). A power outage appeared to have caught the lid mid-cycle, blocking the lid enough to keep the motor constantly cycling until it burnt out.

Washington State Student Repeat Winner for NADP-Related Science Fair Project

Figure 9. Click to enlarge

For the second year in a row, Ella Ashford, a student from Port Townsend, Washington, won first place at the Washington State Science and Engineering Fair. She won in the Earth and Environmental Sciences category’s senior division (Figure 9). Ella used NADP data to illustrate the impact of ammonia emissions from a local pulp and paper mill on air quality in her hometown. She exposed water samples to ammonia gas in a test chamber to illustrate how air pollution can impact water quality. Her samples were sent to the NADP’s Central Analytical Laboratory for testing.

Figure 10. Click to enlarge

See the story about Ella’s first win here. Congratulations to Ella and her impressive, successful projects!

Call for Abstracts Now Open for the 2016 NADP Scientific Symposium

The 2016 NADP Scientific Symposium and Fall Meeting will take place on October 31-November 4, 2016 in Santa Fe, New Mexico and is intended for scientists, resource managers, policy-makers, and students interested in atmospheric deposition, air quality, climate change, and their effects on natural and cultural resources. NADP committee meetings, open to all, convene on Monday, October 31 and Tuesday, November 1. The Scientific Symposium will be held Wednesday-Friday, November 2-4.

The Call for Abstracts is now open for the meeting! Oral and poster presentations are invited on all aspects of deposition monitoring, networks, equipment, sampling and analytical methods, modeling, research linking data to ecological responses, and the application and use of data for management and policy decisions. The submission deadline is Friday, July 15, 2016.

Recent Publications

A listing of recent journal publications that have used NADP data (the networks used are listed in bold next to the DOI). A publically available online database that lists citations using NADP data is accessible at: http://nadp.isws.illinois.edu/lib/bibliography.aspx.

Coburn, S., Dix, B., Edgerton, E., Holmes, C. D., Kinnison, D., Liang, Q., ... & Volkamer, R., 2016. Mercury oxidation from bromine chemistry in the free troposphere over the southeastern US. Atmospheric Chemistry and Physics, 16 (6), 3743-3760.
doi:10.5194/acp-16-3743-2016 MDN

David, M. B., Gentry, L. E., & Mitchell, C. A., 2016. Riverine Response of Sulfate to Declining Atmospheric Sulfur Deposition in Agricultural Watersheds. Journal of Environmental Quality.
doi:10.2134/jeq2015.12.0613 NTN

Domagalski, J., Majewski, M. S., Alpers, C. N., Eckley, C. S., Eagles-Smith, C. A., Schenk, L., & Wherry, S., 2016. Comparison of mercury mass loading in streams to atmospheric deposition in watersheds of Western North America: Evidence for non-atmospheric mercury sources. Science of The Total Environment.
doi:10.1016/j.scitotenv.2016.02.112 MDN

Eagles-Smith, C. A., Ackerman, J. T., Willacker, J. J., Tate, M. T., Lutz, M. A., Fleck, J. A., ... & Davis, J. A., 2016. Spatial and temporal patterns of mercury concentrations in freshwater fish across the Western United States and Canada.Science of The Total Environment.
doi:10.1016/j.scitotenv.2016.03.229 NTN, MDN

Fegel, T. S., Baron, J. S., Fountain, A. G., Johnson, G. F., & Hall, E. K., 2016. The differing biogeochemical and microbial signatures of glaciers and rock glaciers. Journal of Geophysical Research: Biogeosciences.121: 919-932.
doi:10.1002/2015JG003236 NTN

Simpson, M., & Hubbart, J. A., 2016. Spatial trends of precipitation chemistry in the Central Plains region of the United States. Environmental Earth Sciences, 75(8), 1-15.
doi:10.1007/s12665-016-5526-4 NTN, AMNet

Singh, N. K., Reyes, W. M., Bernhardt, E. S., Bhattacharya, R., Meyer, J. L., Knoepp, J. D., & Emanuel, R. E., 2016. Hydro-Climatological Influences on Long-Term Dissolved Organic Carbon in a Mountain Stream of the Southeastern United States. Journal of Environmental Quality.
doi:10.2134/jeq2015.10.0537 NTN

Stoddard, J. L., Van Sickle, J., Herlihy, A. T., Brahney, J., Paulsen, S., Peck, D. V. Peck, R. Mitchell, A. I. Pollard, 2016. Continental-Scale Increase in Lake and Stream Phosphorus: Are Oligotrophic Systems Disappearing in the United States?.Environmental Science & Technology, 50(7), 3409-3415.
doi:10.1021/acs.est.5b05950 NTN

Sullivan, T. P., & Gao, Y., 2016. Assessment of nitrogen inputs and yields in the Cibolo and Dry Comal Creek watersheds using the SWAT model, Texas, USA 1996–2010. Environmental Earth Sciences, 75(9), 1-20.
doi:10.1007/s12665-016-5546-0 NTN

Yen, H., Daggupati, P., White, M. J., Srinivasan, R., Gossel, A., Wells, D., & Arnold, J. G., 2016. Application of Large-Scale, Multi-Resolution Watershed Modeling Framework Using the Hydrologic and Water Quality System (HAWQS). Water, 8(4), 164.
doi:10.3390/w8040164 NTN