(4) Groundwater pollution source intensity evaluation
(a) Pollution source hazard rating
• Indicators, weights and scores
Using the method described in Sect. 3.2.2.2, indicator-specific scores are given: 10
for landfill volume (Y1) which reaches 70 Â 10
4 m
3 ; 1 for landfill period (Y2)
spans 20 years; 6 for maximum leachate production (Y3) which attains
1.85 Â 10
4 m
3 /a; 8 for landfill type (Y4) as mainly MSW and hazardous waste are
landfilled; 1 for seepage control (Y5) which relies on two composite anti-seepage
layers; and 1 for leachate treatment (Y6) as there is collection or treatment system.
Using the equation
S ¼b 1 Â Y1 þ b 2 Â Y2 þ b 3 Â Y3 þ b 4 Â Y4 þ b 5 Â Y5 þ b 6 Â Y6;
S ¼0:3130 Â 10 þ 0:2049 Â 1 þ 0:1707 Â 8 þ 0:1262 Â 6 þ 0:0993
 1 þ 0:0861  1
The hazard index of the landfill is calculated to be 5.6431, rated Grade II.
(b) Vadose zone mitigation rating
• Indicators and scores for pollution control
The sub-basin of the Qaidam Basin where the landfill sits is surrounded by bedrock
mountainous areas and classified into macroscopically closed tectonic basin. Thick
and loose sand and gravel of the Quaternary period have been deposited. Especially
the gravel layer and silty gravel layer of the middle and upper Pleistocene periods
provide sound media and space for groundwater endowment. According to experience, the permeability coefficient of sand and gravel ranges from 5.78 Â 10
−2 to
1.74 Â 10
−1 cm/s. Therefore, the vadose zone has weak performance in pollution
control, for which a score of zero is given.
• Indicators and scores for vulnerability
Considering the weak performance in pollution control, the comprehensive evaluation of vadose zone is not conducted, so is the vulnerability assessment.
(c) Rating and evaluation of groundwater pollution source intensity
Based on the above results, the hazard of pollution sources is rated Grade II.
Without consideration to the comprehensive evaluation of vadose zone, the
intensity of groundwater pollution sources for the landfill is rated Grade II.
(5) Health risk assessment of groundwater environment
(a) Hazard identification
According to the hydrogeological survey and field investigation, there is no
perennial water flow and groundwater endowment due to simple hydrogeological
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(a) Pollution source hazard rating
• Indicators, weights and scores
Using the method described in Sect. 3.2.2.2, indicator-specific scores are given: 10
for landfill volume (Y1) which reaches 70 Â 10
4 m
3 ; 1 for landfill period (Y2)
spans 20 years; 6 for maximum leachate production (Y3) which attains
1.85 Â 10
4 m
3 /a; 8 for landfill type (Y4) as mainly MSW and hazardous waste are
landfilled; 1 for seepage control (Y5) which relies on two composite anti-seepage
layers; and 1 for leachate treatment (Y6) as there is collection or treatment system.
Using the equation
S ¼b 1 Â Y1 þ b 2 Â Y2 þ b 3 Â Y3 þ b 4 Â Y4 þ b 5 Â Y5 þ b 6 Â Y6;
S ¼0:3130 Â 10 þ 0:2049 Â 1 þ 0:1707 Â 8 þ 0:1262 Â 6 þ 0:0993
 1 þ 0:0861  1
The hazard index of the landfill is calculated to be 5.6431, rated Grade II.
(b) Vadose zone mitigation rating
• Indicators and scores for pollution control
The sub-basin of the Qaidam Basin where the landfill sits is surrounded by bedrock
mountainous areas and classified into macroscopically closed tectonic basin. Thick
and loose sand and gravel of the Quaternary period have been deposited. Especially
the gravel layer and silty gravel layer of the middle and upper Pleistocene periods
provide sound media and space for groundwater endowment. According to experience, the permeability coefficient of sand and gravel ranges from 5.78 Â 10
−2 to
1.74 Â 10
−1 cm/s. Therefore, the vadose zone has weak performance in pollution
control, for which a score of zero is given.
• Indicators and scores for vulnerability
Considering the weak performance in pollution control, the comprehensive evaluation of vadose zone is not conducted, so is the vulnerability assessment.
(c) Rating and evaluation of groundwater pollution source intensity
Based on the above results, the hazard of pollution sources is rated Grade II.
Without consideration to the comprehensive evaluation of vadose zone, the
intensity of groundwater pollution sources for the landfill is rated Grade II.
(5) Health risk assessment of groundwater environment
(a) Hazard identification
According to the hydrogeological survey and field investigation, there is no
perennial water flow and groundwater endowment due to simple hydrogeological
5.2 Northwest China
183