Total chlorophyll

Overview

Fluorescence of water is measured to estimate the chlorophyll concentration in the water. Chlorophyll is the green pigment in plants and algae. Chlorophyll measurements are used to dertermine how much algae is in the water. When a beam of light from the meter is shown on the water at a specific wavelength of 470 nanometers, chlorophyll and some other organic matter in the water fluoresce (emit or reflect) another wavelength of light at 650 to700 nanometers. A photodetector measures the amount of fluoresced light. That measurement then is converted to an equivalent measure of chlorophyll.

Water-quality standards and criteria are developed by the States, approved by the U.S. Environmental Protection Agency (USEPA), and then promulgated (passed into law) as standards by each State. Graphs on this website allow comparison of measured and computed data to these standards and criteria by plotting them as straight lines. When evaluating data to decide whether water quality is suitable for the intended use, viewers are cautioned to consider the uncertainty associated with these computed data.