*2.3.2 The degree of contamination Cd*

The degree of contamination value (*Cd*) is the sum of all *C <sup>i</sup> <sup>f</sup>* , which accounts for the total of the sediment pollution. *C <sup>i</sup> <sup>f</sup>* are classified as follows:

*Cd* <8, low degree of contamination; 8≤ *Cd* <16, moderate degree of contamination; 16≤ *Cd* < 32, considerable degree of contamination; *Cd* ≥32, very high degree of contamination.

The thresholds are determined by the number of substances. Eight substances were analyzed in Håkanson's research; therefore, the threshold is 8 for the low degree of contamination. *Cd* classification thresholds should be modified for different assessments. For example, if there are five substances analyzed in an assessment, then the threshold for the low degree of contamination should be 5.
