Some ten years ago a big multi-institutional study started in the
Netherlands about atmospheric depositions, which was assumed to be an
important cause of "acid rain". This involved, amongst many other things,
the monitoring of such depositions in a several forest sites. I am sure they
can give you lots of information about how to measure atmospheric N
depositions. A contact might be Dr. Ir. G.M.J. Mohren from the Institute for
Forestry and Nature Research (IBN-DLO;
http://www.ibn.dlo.nl/index-eng.html).
 
Success,
 
Arjan Gijsman
Centro Internacional de Agricultura Tropical (CIAT)
Cali, Colombia
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