TOWARD A STANDARD METHOD OF MEASURING COLOR IN FRESH-WATER

Researchers use various wavelengths between 270 and 450 nm to measure color. Data from 20 Quebec takes indicate that spectrophotometric estimates of water color at different wavelengths are significantly different. We propose the measurement of light absorbance at 440 nm as a standard method for measuring color in freshwater and provide an equation to convert absorption coefficients at 4,40 nm (g440) to standard Pt units. An equation for standardizing reported color values estimated at different wavelengths is also provided- We show that Pt-Co standard solutions do not adequately mimic the spectral properties of aquatic humic compounds and that conventional Pt units are inappropriate for measuring these compounds in water. Tannic acid equivalents may provide a suitable alternate unit for quantifying color in freshwater. An equation is provided to estimate tannic acid equivalents from g440 in lake water.