Data Series 283

Data Series 283

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Sampling Protocols

Springs were sampled using equipment that had been cleaned with detergent and rinsed as described in the National Field Manual for the Collection of Water-Quality Data (U.S. Geological Survey, 1998), sealed in plastic bags, and packed in backpacks for transport, on foot, to the sampling sites. Water-quality samples were withdrawn from spring pools or from inflows or outflows of spring pools, using 140-mL plastic syringes. Samples were processed on site. Samples requiring filtration were passed from the syringe through a disposable disk or capsule filter (0.45-μm pore diameter) and into the appropriate sample bottle. Disk and capsule filters were rinsed with sample water before sample collection. Bottled samples for major-ion, trace-element, stable-isotope, and tritium analyses were sealed in a plastic bag and stored in a backpack for transport to an ice-filled cooler in a field vehicle at the trailhead. Samples for nutrient analysis and alkalinity titration were stored on ice in an insulated container and transported by backpack to an ice-filled cooler in a vehicle at the trailhead. Alkalinity samples were titrated within 5 or 6 hours of sample collection. Additional information about sample processing can be found in Appendix A.

Field measurements taken on-site included: dissolved oxygen, pH, specific conductance, and air and water temperature. Except for dissolved oxygen, these parameters were measured using meters and by methods outlined by the USGS (1998). Dissolved oxygen was measured using a CHEMetrics colorimetric test kit (Gilbert and others, 1982).

The flow rate of water discharging from springs was either estimated visually or measured using the volumetric method described by Rantz and others (1982). Spring discharge was estimated visually at Willow Spring South Rivulet, Superintendent’s Spring, Chalone Bridge Spring, and McCabe Canyon Spring No. 1. Discharge was measured volumetrically with a 5-qt container and stop watch at Split Rock Spring and Moses Spring, and with a 1-qt container and stop watch at Oak Tree Spring.

Analyses of spring samples to determine the concentration of major ions, nutrients, and trace elements were conducted by the USGS National Water Quality Laboratory in Lakewood, Colorado. Analytical procedures used at the National Water Quality Laboratory are described by Faires (1993); Fishman and Friedman (1989); Fishman (1993); Garbarino, Kanagy, and Cree (2006); Garbarino (1999); Patton and Truitt (1992); and Patton and Krysyalla (2003). In addition, the National Water Quality Laboratory followed laboratory quality-assurance protocols detailed in Maloney (2005). The stable-isotope composition (oxygen-18 and deuterium) of spring samples was determined at the USGS Isotope Lab in Reston, Virginia. The procedural methods for the isotopic analyses are described by Coplen and others (1991) and Epstein and Mayeda (1953). Measurements of tritium concentration of spring samples were conducted at the University of Miami Tritium Laboratory in Miami, Florida. A description of the methods used is described by Östlund (1987).

For quality-assurance purposes, temperature meters were calibrated in USGS labs in Sacramento, California, prior to field sampling. The pH and specific-conductance meters were calibrated in the field twice daily with known standards. Sampling equipment was cleaned before the collection of each sample. To evaluate the potential for cross-contamination during field sampling, a field blank was collected and processed at Moses Spring at the beginning of the sampling effort on June 6, 2006. A field blank is an aliquot of inorganic-free blank water, purchased from a commercial laboratory and processed identically to environmental samples—passed through the 140-mL sampling syringe and 0.45-μm disk filter and into a sample bottle. The field blank was analyzed for trace elements, nutrients, and total nitrogen. The field blank was not analyzed for major ions because the specific conductance was sufficiently low (1 μS/cm) to ensure that the concentrations of dissolved major ions were not present at levels within an order of magnitude of concentrations in the environmental samples.

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