‘Measurements include rainfall amounts, nitrate (NO3-N), ammonia (NH4-H), soluble reactive phosphate (SRP), and total nitrogen and phosphorus concentrations in bulk precipitation collected at multiple locations.
To measure the chemical composition of bulk precipitation inputs.
Location of Sampling Stations: Bulk precipitation (BP) is collected at four sites (R20B, N01B, 020B, and HQ). Grid locations N-31, N-22, N-30 and C-16, respectively.
Frequency of Sampling: Samples are collected as soon as possible after each rain event (or when there has been an accumulation of at least 4 mm in the on-sight rain gauges after a number of small precipitation events) during the period May 1 to October 31. During the winter, collections are less frequent, depending upon the freeze-thaw patterns.
Variable Measured: 1. Amount of precipitation (mm); 2. concentration of NO3-N in each sample; 3. using volume-weighted monthly composite from each site, measured concentrations of NH4-N, soluble reactive phosphate (SRP), and total N and total P.
Methods: Precipitation amounts (mm) are measured at each site using a standard rain gauge. Bulk precipitation samples for analysis are collected into a single, acid-washed 500 mL polyethylene bottle with a plastic funnel glued into the cap.
After each rain event ( greater than 4mm) precipitation amounts at each site are recorded and BP samples for analysis are returned to the laboratory. Samples are inspected and removed of foreign debris and insects. They are decanted and weighed into acid washed polyethylene bottles and frozen until analysis. Each same is analyzed for NO3-N. Monthly a volume weighted composite is made for each site and subsequently analyzed for NH4-N, SRP and total N and total P.
Nitrogen and phosphorous nutrient determinations are analyzed on an 0.I. Analytical Flow Solution IV (FSIV) instrument. Simultaneous determinations of nitrate (single events) and SRP (monthly composition) may be analyzed from a single aliquot by use of a stream splitter. In the same manner, total N and total P are analyzed simultaneously. Ammonium determinations are performed as a single analyte. A Windows ®- based software program (WINFLOW) purchased with the FSIV allows automation of the analyzer. Regression curve information, graphic display during analyses, and calculated results provide the operator immediate information about samples. At the completion of each run, data files are electronically stored on the instrument’s computer and also transferred to offsite backup data storage.
Inorganic Nitrogen (N) and Phosphorus (P) (nitrate, ammonium, and orthophosphate or SRP, soluble reactive phosphate) are run within one month of sample collection. As NO3 and SRP are analyzed simultaneously, dual standards (both N & P) are utilized. Concentrations range from 0.5 to 250 ug/L NO₃-N and 0.5 to 150 ug/L SRP. Ammonium standards range from 0.5 to 200 ug/L NH₄-N. The concentrations of most stream water samples are found within these ranges of concentrations but may be manually diluted if needed. As these samples are analyzed, they are checked immediately by the Lab Research Assistant (RA) and rerun immediately if values are off. Data are entered by the Lab RA into the Master Excel spreadsheet.
Total N and total P concentrations values are determined in a two-step process, utilizing a Total Persulfate Digestion (modified from J.J. Ameel American Environmental Laboratory, October 1993), followed by simultaneous determinations of nitrate and SRP on FSIV instrument. In general, a series of 10 duplicated standard solutions, a digestion recovery standard (i.e. Spike solution: ATP + urea), 4 spiked samples, an oxidizing reagent blank and 88 samples comprise each digestion run. Dual standards (both NO₃ and SRP) are used, ranging in concentrations from 0 to 2000 ug/L NO₃-N and 0 to 200 ug/L SRP. Pyrex screw-top digestion tubes are used for this procedure using potassium persulfate as the oxidizing agent in an autoclave digestion for 55 minutes at 17 psi. A 3N sodium hydroxide reagent is used in this procedure for maintaining proper pH. Approximately 1 liter of cocktail solution (matches the final chemical composition of samples +reagents) is digested along with samples and used as the carrier solution for the FSIV determinations. Digested samples are then analyzed for NO3-N and SRP using FSIV instrument. A digestion recovery value is calculated from digestion recovery standards and spiked samples and then applied to all samples to determine corrected TN and TP concentration values.
Summary of All Changes: When this study was established in 1982, bulk precipitation was collected on four watersheds 001D, 001C, N01B, and N04D). All sampling sites were at lowland positions (on Tully soils) just above stream banks. In 1983 bulk precipitation was limited to three watershed (001C, N01B and N04D). In 1984, bulk precipitation was collected from 001C and N01B through June, with N04D being added in mid - June. An additional site for collection of bulk precipitation at headquarters (HQ) was added in April 1985. Bulk precipitation was moved from N04D to 020B in February of 1992 following the bison introduction.
No preservatives were used in 1982. Phenyl mercuric acetate (PMA) as a preservative was added to samples starting in 1983; its use was discontinued as of June 27, 1994. A stock solution of 1 mg/g PMA was made and 0.5 mL was added to each bulk precipitation collector prior to placement in the field. Because of the toxicity of this preservative, all collections were returned to the laboratory for volume measurements. No PMA - treated samples were disposed of on the prairie.
Samples collected in 1982-1983 were analyzed according to the methods outlined in Appendix A of the 1983 LTER Methods Manual. In 1984, methods of chemical analysis were modified. Samples collected in 1984 to present were analyzed according to the methods given in Appendix A of the 1984 LTER Methods Manual.
In 2001, 001C watershed was renamed to R20B.
For additional metadata information see: http://lter.konza.ksu.edu/sites/default/files/DC.pdf
For additional methods information see: http://lter.konza.ksu.edu/sites/default/files/MM.pdf