A global assessment of precipitation chemistry and deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity and pH, and phosphorus
Date
2014Author
Vet, Robert
Pienaar, Jacobus J.
Artz, Richard S.
Carou, Silvina
Shaw, Mike
Metadata
Show full item recordAbstract
A global assessment of precipitation chemistry and deposition has been carried out under the direction
of the World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) Scientific Advisory
Group for Precipitation Chemistry (SAG-PC). The assessment addressed three questions: (1) what do
measurements and model estimates of precipitation chemistry and wet, dry and total deposition of
sulfur, nitrogen, sea salt, base cations, organic acids, acidity, and phosphorus show globally and
regionally? (2) has the wet deposition of major ions changed since 2000 (and, where information and
data are available, since 1990) and (3) what are the major gaps and uncertainties in our knowledge? To
that end, regionally-representative measurements for two 3-year-averaging periods, 2000e2002 and 2005e2007, were compiled worldwide. Data from the 2000e2002 averaging period were combined
with 2001 ensemble-mean modeling results from 21 global chemical transport models produced in
Phase 1 of the Coordinated Model Studies Activities of the Task Force on Hemispheric Transport of Air
Pollution (TF HTAP). The measurement data and modeling results were used to generate global and
regional maps of major ion concentrations in precipitation and deposition. A major product of the
assessment is a database of quality assured ion concentration and wet deposition data gathered from
regional and national monitoring networks. The database is available for download from the World Data
Centre for Precipitation Chemistry (http://wdcpc.org/). The assessment concludes that global concentrations
and deposition of sulfur and nitrogen are reasonably well characterized with levels generally
highest near emission sources and more than an order of magnitude lower in areas largely free of
anthropogenic influences. In many parts of the world, wet deposition of reduced nitrogen exceeds that of
oxidized nitrogen and is increasing. Sulfur and nitrogen concentrations and deposition in North America
and Europe have declined significantly in line with emission reduction policies. Major regions of the
world, including South America, the more remote areas of North America, much of Asia, Africa, Oceania,
polar regions, and all of the oceans, are inadequately sampled for all of the major ions in wet and dry
deposition, and particularly so for phosphorus, organic forms of nitrogen, and weak acids including
carbonates and organic acids. Measurement-based inferential estimates of dry deposition are limited to
sulfur and some nitrogen in only a few regions of the world and methods are highly uncertain. The
assessment concludes with recommendations to address major gaps and uncertainties in global ion
concentration and deposition measurements
URI
http://hdl.handle.net/10394/15869https://doi.org/10.1016/j.atmosenv.2013.10.060
https://www.sciencedirect.com/science/article/pii/S1352231013008133