THE EVALUATION OF COLOR IN NATURAL-WATERS

A model describing the objective evaluation of colour from the transmi ssion properties of natural waters was developed and applied to a wide range of Australian waters. These calculated colours show that measur ement of filtered water absorbance at 456 nm calibrated against Pt Co colour standards agrees with the visually perceived colour intensity b y comparator methods and the Pt -Co or Hazen scale of measurement with in a maximum error range of +/- 20%. The error is significantly larger when analytical wavelengths below 440 nm are used. The interference t o colour measurement caused by scattering of suspended matter was acco unted for at the analytical wavelength. The light scatter component wa s found to be significant when the ratio of turbidity (in nephelometri c turbidity units) to colour (in Hazen units) is greater than 0.02. Th e use of the 456 nm wavelength is proposed for the standardization of colour measurement in natural waters.