Chromophoric Dissolved Organic Matter (CDOM)

August 30th, 2019



Chromophoric Dissolved Organic Matter (CDOM) is the result of decaying material in aquatic environments

Chomorphoric and colored are used interchangeably to described CDOM , because a chromophore  is the part of the molecule responsible for color

These decay products are usually in the form of tannins -the breakdown of plant matter

Tannins, along with the rest of the CDOM, stain water bodies and have an effect on light penetration

Along with turbidity and chlorophyll, CDOM is an important consideration for determining the light attenuation (loss of light with depth) in a water body

Light attenuation can have cascading effects on the health and productivity of the water system

CDOM effects on water quality:

  • Limits light penetration in water bodies
  • Contains abundant nutrients for algal growth
  • Fuels bacterial respiration
  • Regulating heat transfer to the water system

A key attribute of certain CDOM is its fluorescent quality. Fluorescent dissolved organic matter, or fDOM, is the fraction of CDOM that fluoresces

fDOM is used to measure certain types of CDOM and to estimate the total CDOM in a water system

Benefits of using fluorescence to measure CDOM

  • More sensitive to absorption methods
  • Excitation and emission spectra provides more information than absorbance alone
  • May be applied to a wide array of scientific investigations

There are two main ways to measure CDOM

Water samples can be collected and brought back to the laboratory for analysis in a Spectrophotometer

Individual Fluorometers can be deployed, or a fluoroprobe can be attached to a multi-parameter sonde for in-situ  measurements

Spectrophotometers can analyze the reflective properties of water samples to reveal the amount and type of CDOM present.

The detector measures the transmittance and absorbance of the sample and converts it to a digital display.

An interior light coupled with a monochromator produces a specific wavelength of light that passes through the sample

Fluorometers measure the fluorescence of CDOM, which allows scientists to understand the type and quantity in a water body

The light excites the sample, and a detector measures the wavelength emitted. This fluorescence value is then recorded by the instrument

Bench-top fluorometer

Fluorescence-measuring sensor

A wavelength of light specific to the excitation spectrum of the compound of interest is sent through the sample


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