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.


NADP Map Highlight

  pH map

The 2013 full annual report will be released on the NADP website in October 2014.

Figure 1 shows the precipitation-weighted mean hydrogen ion concentration as pH (in pH units) for 2013. Typically, a precipitation pH of less than 5.1 is considered to be "acidic precipitation". The decreasing pH of precipitation from west to east is clearly evident, with the lowest values (e.g. most acidic) seen in the industrial Midwest. The measured pH of precipitation in this area is typically between 4.7 and 4.9 pH units in recent years. Conversely, the pH as measured in the Western U.S. is typically between 5.3 and 5.7 pH units. The pH scale is logarithmic, so the difference in pH between these areas is rather large.

pH map

Figure 2 shows the annual flux of hydrogen ions to the Earth's surface (in kilograms of hydrogen ion per hectare of area for 2013). As with the pH concentration map, the hydrogen ion flux increases as you move towards the East Coast and South. The flux is also high along the Northwest Coast. Therefore, during 2013, most of the West has about 0.01-0.02 Kg of hydrogen ion added to each hectare, whereas the Northwest, South, and East had between 2 and 5 times as much hydrogen ion added to each hectare.

The two maps are linked by the amount of precipitation that was measured during the year. Figure 1 shows the typical precipitation pH as measured in the laboratory. By multiplying this value by the amount of annual precipitation, the second map is generated which represents the total flow of hydrogen ions to the surface with the precipitation during the year. This calculation is made for all measurement locations, and shown together, produce the deposition map.

NADP Applied Research Highlight

Estimates of Inorganic Nitrogen Wet Deposition from Precipitation for the Conterminous United States, 1955-84

The USGS has recently published Estimates of Inorganic Nitrogen Wet Deposition from Precipitation for the Conterminous United States, 1955-84, by Jo Ann M. Gronberg, Amy S. Ludtke, and Donna L. Kninfong. This report provides estimates of inorganic nitrogen deposition from precipitation for the conterminous United States for 1955-56, 1961-65, and 1981-84. The estimates were derived from ammonium, nitrate, and inorganic nitrogen concentrations in atmospheric wet deposition and associated precipitation-depth data. The estimates presented here predate the already available NADP National Trends Network (NTN) inorganic nitrogen deposition raster datasets, and effectively expand the length of nitrogen deposition records.

The national historical data sources that were coalesced for the nitrogen deposition estimates were: 1) Air Force Cambridge Research Center's study by Junge, 1955-1956; 2) Public Health Service and the National Center for Atmospheric Research, by Lodge and others, 1960-1966; and 3) National Atmospheric Deposition Program, 1981-1984). A fourth study that took place from 1972-1982, conducted jointly by the National Oceanic and Atmospheric Administration, U.S. Environmental Agency, and World Meteorological Organization, is discussed in the report and the data is available online.

The nitrogen deposition estimates, in kilograms per hectare, are presented as 2,338.383-meter by 2,338.383-meter resolution raster datasets. The units and resolution used are the same as those used in the NADP National Trends Network raster datasets from 1985 to 2012, for easier comparison between these sources. All data from the 4 national studies, as well as a regional USGS study by Pearson, are available in tabular datasets. These data sets include the analytical results (including Ca, Mg, K, Na, NH4, NO3, N, Cl, SO4, pH, conductance when available), precipitation depth, calculated site-specific precipitation-weighted concentrations, and raster datasets of nitrogen from wet deposition, and are provided as appendixes in this report

This publication is available online at doi:10.3133/sir20145067

New Book Released on Air Pollution and Freshwater Ecosystems

book coverA practical book for professionals who rely on water quality data for decision making, this new book titled Air Pollution and Freshwater Ecosystems: Sampling, Analysis, and Quality Assurance, is based on three decades experience of three highly published water and watershed resource professionals. The authors of this book are Timothy J. Sullivan (E & S Environmental Chemistry, Corvallis, Oregon, USA; member of NADP), Alan T. Herlihy (Oregon State University, Corvallis, USA), and James R. Webb (University of Virginia, Charlottesville, USA).

The book focuses on the analysis of air pollution sensitive waters and the consequent effects associated with soil and water acidification, nutrient-N enrichment, or the effects of atmospherically deposited toxic substances. It also covers lake zooplankton and/or stream macroinvertebrate biomonitors. Explanations of the reasons behind various recommendations provide readers with the tools needed to alter recommended protocols to match particular study needs and budget.

Key features of the book:

  • Supplies practical hands-on recommendations for water quality investigation
  • Covers all major aspects of water quality study, including field sampling, laboratory measurements, quality assurance and quality control, data analysis, and sampling of aquatic biota
  • Integrates knowledge of whole watershed systems
  • Provides detailed description of how to design a field study that is linked to needs and research questions

For more information and to purchase the book, please visit:


NADP Fall Meeting Announcement

The 37th Annual NADP Meeting and Scientific Symposium: The Global Connection of Air and Water is being held in Indianapolis, IN at the Hilton Indianapolis Hotel and Suites from October 21-24, 2014. The invitation for the 37th Symposium is for scientists, resource managers, policy-makers, and students interested in atmospheric deposition, air quality, climate change, and their effects on natural and cultural resources. 

The Scientific Symposium will include two days (October 22nd and 23rd) of oral presentations grouped by theme (e.g., mercury deposition and effects, urban air chemistry and deposition, etc.), a keynote address and video presentation by NASA astronaut David Wolf, a submitted poster session with reception, a student poster session, and an optional group outing to the Indianapolis Motor Speedway. NADP committee meetings, which are open to all, convene on Tuesday, October 21st and the NADP Total Deposition Science Committee will meet on Friday, October 24th.

Registration is available on the meeting website. The registration fee is $249 if made before September 30, 2014 ($295 after September 30th).

More information on the NADP 2014 Annual Meeting and Scientific Symposium (including a full list of oral presentation themes) can be found on the meeting website.