Dryfall deposition chemistry data

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Dry atmospheric fallout (dryfall) is collected monthly using an Aerochem Metrics wetfall/dryfall collector located at the LTER weather station. Each sample is analyzed for NO3, NH4, Cl, SO4, Ca, Mg, Na, K, Total N, & Total P.

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Method of recording: instrumental

An Aerochem metrics WET/DRY Precipitation collector holds both a WET and a DRY precipitation collector bucket. The bucket is replaced in the field with a clean bucket whenever one is brought back from the field for processing. The DRY is collected once a month. The WET is collected after each collectable rain event. Preliminary sample preparation is done in Rm 236 as per written procedure. Samples are then sent to Dr. Bill Schlesinger at Duke University for analysis. Results sent back have had values adjusted for any dilutions done when preparing the samples for analysis. Blank values have also been subtracted out. Preparation of WETFALL/DRYFALL PRECIPITATION samples for analysis: (FILE: WETDRY.PRO) UPDATED: 6/8/88 as per conversation with Bill Schlesinger. Cleaning: All materials that come in contact with sample are cleaned as follows: 1. Rinse thoroughly with tap water. 2. Wash with dilute solution of Alconox detergent. 3. Rinse minimum 3 times thoroughly with deionized water. 4. Rinse minimum 3 times thoroughly with solution of 1N HCl. 5. Rinse minimum 5 times thoroughly with deionized water. 6. Do not touch any surfaces that will be in contact with sample. 7. Place materials in drain to dry in such a position that surfaces to be in contact with sample will not be contaminated by drain or by particulate fallout. Do not leave collector buckets overnight. 8. Filter apparatus, bottles, etc. used to process sample are to be rinsed 3 times with deionized water immediately prior to using when they are clean. Otherwise, clean as per steps 1-7 above immediately before using. The DRY precipitation is collected as near to the first of each month as possible. The following is to be done for DRYFALL sample only: 1. Add 500ml deionized water to DRYFALL collection bucket and swirl carefully to dissolve dryfall. Blanks Prepare 2 blanks by filtering 200ml deionized water through new 0.45um filter. Split this sample between 2 125ml bottles. Add 100ul PMA to one of the bottles only. Total N & P: Sample is not filtered. Add at least 100ml to 125ml bottle. Preserve with 100ul of 1000ppm phenyl mercuric acetate (PMA) per 100ml sample. NO3 & NH4: 100ml of sample is filtered using 0.45um Metricel membrane filter. Preserve with 100ul of 1000ppm phenyl mercuric acetate (PMA) per 100ml sample. Minimum sample size is 20ml. Ca,Mg,Na,K, 100ml of sample is filtered using 0.45um Cl, SO4 Metricel membrane filter. No preservation is necessary. Minimum sample size is 60ml. Each bottle is labeled with type of analysis to be performed, type of precipitation (wet or dry), and collection date. We try to provide subsamples of 100ml for each type of analysis. Samples are refrigerated until just prior to shipping. 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.

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Raw analyzed data has been adjusted for dilution factor occurring in sample preparation and for blank values associated with each date. Values were reported for NO3-N and NH4-N prior to October 1987. These values have been corrected in the data set so they now report NO3 and NH4. The conversion is NO3-N x 62/14 = NO3 NH4-N x 18/14 = NH4 DON=Total N - (NO3-N + NH4-N) -(blank +PMA)

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Jornada LTER weather station located about 1km south of NMSU College Ranch headquarters.


Frequency of measurement: monthly

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