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Atmospheric deposition as found in dryfall (dust) and wetfall precipitation has been collected and analyzed since 1983 using an Aerochem Metrics wetfall/dryfall collector located at the Jornada LTER weather station north of Las Cruces, NM, USA. Wetfall occurring as precipitation is collected after each event with a sample size large enough to analyze. Each sample is analyzed for Br, Ca, Cl, F, HPO4, K, Mg, Na, NH4, NO3/NO2, SO4, Total N, and Total P. Analysis of Sr and Dissolved Organic Nitrogen was discontinued in 2003. Dryfall data are available as a separate data package.
An Aerochem metrics WET/DRY Precipitation collector holds both a WET and a DRY precipitation collector bucket (11" top diameter). Preliminary sample preparation is done as per written procedure: For WETFALL sample only: Add up to 100ml to one pre-weighed 125ml bottle of WETFALL sample. Add approximately 1 microliter of PMA (phenylmercuric acetate) for each milliliter of sample. Weigh 125ml bottle with sample. Subtract bottle weight from total weight and calculate amount of WETFALL assuming 1g=1ml water. If more WETFALL remains in collection bucket, weigh remaining bucket sample, obtain total WETFALL volume, and record in WET/DRY PRECIPITATION data book. Analysis: In each sample, F, Cl, NO3, SO4, NH4, Ca, Mg, Na, K, total N, and total P are determined by standard laboratory procedures: F, Cl, NO3, SO4 by ion chromatography, NH4 by autoanalyzer: Ca, Mg, Na, by atomic absorption spectrophotometry, total N and total P by persulfate digestion (D'Elia et al. 1977, Limnology and Oceanography 22:760-764) and by autoanalyzer. Dissolved Organic Nitrogen (DON) is determined by subtracting inorganic nitrogen (NO3-N and NH4-N) from Total Nitrogen (TN) as determined using the D'Elia persulfate digestion and autoanalyzer.