LAKE SALVADOR EMPACT SAMPLING PROGRAM

ANALYTICAL TECHNIQUES

Chlorophyll a, Phaeo-pigments

Chlorophyll-a containing plankton were concentrated from a volume of water by filtering at a low vacuum through a glass fiber filter (GFF). The pigments were extracted from the phytoplankton using a solution of 90% Acetone and 10% dimethyl sulfoxide (DMSO). The samples were allowed to steep for 2 to 24 hours (maximum) to extract the chlorophyll-a. The sample was then centrifuged to clarify the solution. The fluorescence was measured before and after acidification with 0.1 N HCl. The fluorescence readings were then used to calculate the concentration (in ug/l) of chlorophyll a and pheophytin a in the sample extract. This procedure is a modification of EPA method 445.0 (Arar and Collins 1992) in which DMSO is used in lieu of grinding for extraction of the pigments.

Nutrients

Water samples were analyzed for nutrients with a Technicon Auto-Analyzer II using the methods listed below for each nutrient:

• Nitrate-Nitrite (EPA Method 353.2, Detection Limit 0.05 mg/l)
• Nitrite (EPA Method 353.2, Detection Limit 0.05 mg/l)
• Ammonium (EPA Method 350.1, Detection Limit 0.01 mg/l)
• Silicate (Technicon Method 186-72W/B, Detection Limit 0.03 mg/l)
• Phosphorus (EPA Method 365.2, Detection Limit 0.01 mg/l)

Salinity

Salinity samples were titrated using a Haake-Buchler Digital Chloridometerù. This device measures the amount of chloride in the sample by titrating it with silver. The corresponding salinity is then calculated.

Suspended Load

Suspended load was determined by filtering a known volume of water through a combusted (550o C) and pre-weighed glass fiber filter (Whatman Type GF/F or equivalent). The filters are dried (at 60o C) then re-weighed to determine total suspended load in mg/l. The filters are then combusted at 550o C, cooled, then re-weighed to determine percent organic (APHA, 1992).

Carbon

Total carbon (TC) is measured by employing High Temperature Catalytic Oxidation (HTCO) using a Shimadzuù TOC-5000A Analyzer. The machine operates by combusting the swater ample (at 680 centigrade) in a combustion tube filled with a platinum-alumina catalyst. The carbon in the sample is combusted to become CO2 which is detected by a non-dispersive infrared gas analyzer (NDIR) to give the total amount of carbon in the sample. Inorganic carbon (IC) is anlayzed by first treating the sample with Phosphoric acid (to remove organic carbon) then performing the above analysis to obtain the total amount of inorganic carbon in the sample. Total Organic Carbon (TOC) is obtained by subtracting the IC value from the TC value.

References

APHA. 1992. Standard Methods for the examination of water and wastewater, 18th ed. American Public Health Association, Inc. New York.

Arar, E. J. and G. B. Collins. 1992. Method 445.0 In vitro determination of Chlorophyll-a in marine and freshwater phytoplankton by fluorescence. Environmental Monitoring Systems Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, OH 45268. Reprinted by Turner Designs, Sunnyvale, CA 94086.