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Table 1 Modified degree of contamination gradation

From: Effects of columbite/tantalite (COLTAN) mining activities on water quality in Edege-Mbeki mining district of Nasarawa state, North Central Nigeria

Modified degree of contamination (mCd)

According to [Abrahim and Parker 2008]

mCd < 1.5

Nil to very low degree of contamination

1.5 < mCd < 2

Low degree of contamination

2 < mCd < 4

Moderate degree of contamination

4 < mCd < 8

High degree of contamination

8 < mCd< 16

Very high degree of contamination

16 < mCd > 32

Ultra-high degree of contamination

mCd< 32

Extremely high degree of contamination