SUVA and Total DOC

Dissolved organic matter is assessed in several ways.  Total dissolved organic carbon (DOC) is determined by high temperature catalytic oxidation.  At high temperatures, organic carbon is oxidized to carbon dioxide.  The instrument then measures the total carbon dioxide produced from a known sample volume.  Total DOC measurements are reported as concentration.  Total organic carbon fluxes can be determined from discharge data.

The aromatic character of DOC can be described with the aid of a spectrophotometer using specific UV absorbance (SUVA) measurements at 254 nm.  Absorbance of a filtered sample through a 1 cm 2-way quartz cuvette is measured at 254 nm.  This measurement is representative of the average absorbance at 254 nm of all of the organic molecules.  The SUVA value for each sample is determined by dividing the absorbance value by the concentration of DOC.  This is useful because it can help describe the source of DOC in runoff during the course of a storm event, which in turn can be useful in determining the flow path of runoff.