Nutrient Analytical Services Laboratory


Particulates & Sediments

Carbon and Nitrogen


Samples are combusted in pure oxygen (O2) under static conditions. Products of combustion are passed over suitable reagents in the combustion tube where complex oxidation occurs. In the reduction tube, oxides of nitrogen (N) are converted to molecular N. The carbon dioxide (CO2), water vapor and N are mixed and released into the thermal conductivity detector where the concentrations of the sample gases are measured.

USEPA. 1997. Method No. 440.0 Determination of Carbon and Nitrogen in Sediments and Particulates of Estuarine/Coastal Waters Using Elemental Analysis. Cincinnati, OH. September 1997.


Phosphorus


Samples concentrated on glass fiber filters are combusted in a muffle furnace at 550° for 90 minutes. Samples are later place in plastic centrifuge tubes where they receive 10 ml of 1 N Hydrochloric Acid for extraction.

Ammonium molybdate and antimony potassium tartrate react in an acid medium with dilute solutions of phosphorus to form an antimony-phospho-molybdate complex which is reduced to an intensely blue-colored complex by ascorbic acid. Color is proportional to phosphorus concentration.

Aspila, I., H. Agemian and A.S.Y. Chau. 1976. A semi-automated method for the determination of inorganic, organic and total phosphate in sediments. Analyst. 101:187-197.


Biogenic Silica


Samples concentrated on membrane filters are placed in polypropylene centrifuge tubes, then digested at 100°C in a 0.2N NaOH solution for 20 minutes. They are quickly cooled in an ice bath, then neutralized with 1N H2SO4.

Silicomolybdate is reduced in acid solution to “molybdenum blue” by ascorbic acid. Oxalic acid is added to eliminate interference from phosphates. Detection of the silicomolybdate complex in the supernatant is by colorimetry.

Technicon Industrial Method No. 186-72 W/B†. Technical Industrial Systems. Tarrytown, New York, 10591.


Total Suspended Solids and Total Volatile Solids


Total suspended solids (TSS) are the retained material on a tared glass filter pad after filtration of a well-mixed sample of water. Results are expressed in mg/L. Total volatile solids (TVS) is a measurement of the volatilized material calculated from the measurement of a total suspended solid (TSS) sample minus the combusted remains.

APHA. 1975. Method 208D. Total Nonfilterable Residue Dried at 103-105 °C (Total Suspended Matter) in Standard Methods for the Examination of Water and Wastewater, 14th Edition. American Public Health Association. Washington, D.C. 1193pp.

USEPA. 1979. Method No. 160.2 (with slight modification) in Methods for chemical analysis of water and wastes. United States Environmental Protection Agency, Office of Research and Development. Cincinnati, Ohio. Report No. EPA-600/4-79-020 March 1979. 460pp.

APHA. 1975. Method 208E (with modification). Total volatile and fixed residue @ 550°C in Standard Methods for the Examination of Water and Wastewater, 14th Edition. American Public Health Association. Washington, D.C. 1193pp.


Chlorophyll a and Phaeopigments


Chlorophyll, in a measured volume of water, is concentrated by filtering through a glass fiber filter, and the pigments on the filter are extracted in 90 % acetone. EPA Methods 445.0, modified 445.0, and the spectrophotometric method based on EPA Method 446.0 and Standard Methods 10200H, 19th ed. are used in this lab.

EPA Methods 445.0 and modified 445.0 are fluorometric determinations of chlorophyll α. Fluorescence is proportional to chlorophyll concentration. In Method 445.0, fluorescence of the extract is measured before and after acidification using a fluorometer. From these readings, the concentrations of total chlorophyll α, active chlorophyll α (also known as corrected), and phaeophytin can be determined. In the modified method445.0, the fluorometer is equipped with specific wavelength filters which read only emissions from chlorophyll a, without interferences from chlorophyll b and phaeopigments. Therefore, the sample is not acidified and only active (corrected) chlorophyll α is determined. Welschmeyer, N.A. 1994. Fluorometric analysis of chlorophyll a in the presence of chlorophyll b and phaeopigments. Limnol. Oceanogr., 39: 1985-1992.

EPA Method 446.0 and Standard Methods 10200H are spectrophotometric determinations of chlorophyll α. Using the Jeffreys and Humphreys Trichromatic equation which uses absorbance values at 750, 664, 647, and 630 nm, no acidification is required. Chlorophyll α, b, and c can be calculated, but phaeophytin cannot. Using Lorenzen’s Monochromatic equation, which uses readings at 750, 664, and 665 nm before and after acidification, chlorophyll α corrected for phaeophytin and phaeophytin, can be determined. Chlorophyll b and c cannot be determined using this equation.


Sediment Size Analysis


This method uses sodium hexametaphosphate as a deflocculant (breaks up the fines) and Ro-tap sieve technique to identify sediment size classes of 2 mm through 63 microns. It does not differentiate between sizes (phi) less than 63 microns.
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