(a) Indicator weights and scores
The AHP method is applied to determine the weights of OCS hazard indicators,
which involves four steps: to establish the hierarchical structure; to construct
pairwise comparison matrixes; and to calculate the relative weight.
The weights of OCS hazard indicators are calculated, as shown in Table 3.6, and
their scores are as shown in Table 3.7.
(b) Rating and evaluation
The OCS hazard scoring equation is established based on indicator weights and
scores:
P ¼ c 1 Â Z1 þ c 2 Â Z2 þ c 3 Â Z3 þ c 4 Â Z4
þ c 5 Â Z5 þ c 6 Â Z6 þ c 7 Â Z7
ð3:3Þ
Wherein P represents the OCS hazard score; Ci and and Zi represent
indicator-specific weight and score respectively.
Based on the calculation results of Eq. (3.3), three grades are divided using the
approach of non-equidistant value range (0–10). Hazard reaches Grade I when
P < 4.0, Grade II when 4.0
P < 7.0 and Grade III when P ! 7.0. The greater
the P value, the higher the hazard of groundwater pollution sources.
(c) Comprehensive evaluation of pollution factors (Z1)
In order to comprehensively evaluate the potential hazards of pollutants to the
groundwater environment, the refined Nemerow’s pollution index is introduced to
Table 3.6 Weights of OCS hazard indicators
Indicator
Z1
Z2
Z3
Z4
Z5
Z6
Z7
Weight
0.22
0.17
0.16
0.1
0.09
0.12
0.14
Fig. 3.6 Hazard rating and evaluation indicator system for OCS
3.2 Method of Groundwater Pollution Source Intensity Rating …
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