shall be deemed (Grade I for undetected indicators). The results of groundwater
quality evaluation are as shown in Table 5.52.
As shown in Table 5.52, there are pollutants far exceeding the limits at all of the
three sampling sites. In light of this, the overall groundwater quality at the sampling
sites is rated Grade V. At No. 1 sampling site, ammonia nitrogen and permanganate
index reach Grade V standards and arsenic Grade IV standard. At the other two
sampling sites, permanganate index reaches Grade V standard and arsenic and
nickel Grade IV standards. In general, the groundwater quality in the OCS site is
poor, but there is no excess of organic pollutants such as benzene and toluene.
(3) Groundwater pollution source intensity evaluation
(a) Pollution source hazard rating
• Indicators, weights and scores
The characteristic pollutants of the OCS site include petroleum, sulfide, total cyanide, benzene and toluene. Since the monitoring data are available for petroleum
and sulfide only, petroleum, sulfide and total cyanide are selected as pollution
factors for evaluation. The pollutants are discharged in the vadose zone with a
source intensity of less than 50 Â 10
4 m
3 /a. The pollution through continuous
infiltration affects more than 10% of the total area. The pollution sources exist for
over 20 years, and the seepage control relies on partial seal.
Using the aforementioned method, indicator-specific scores are given: 10 for
comprehensive evaluation of pollution factors (Z1), 1 for discharge source intensity
(Z2), 8 for location of discharge (Z3), 8 for mode of discharge (Z4), 10 for affected
area (Z5), 5 for seepage control measures (Z6), and 10 for duration of existence (Z7).
Table 5.52 Results of groundwater quality assessment
Items
No. 1 sampling site
No. 2 sampling site
No. 3 sampling site
p H
I
I
I
Ammonia nitrogen
V
III
III
Permanganate index
V
V
V
Hexavalent chromium
I
I
I
Arsenic
IV
IV
IV
Lead
I
I
I
Mercury
III
III
III
nickel
III
IV
IV
Benzene
I
I
I
Toluene
I
I
I
Ethylbenzene
I
I
I
Xylene
I
I
I
Grade of water quality
V
V
V
Level of water quality
Very poor
Very poor
Very poor
192
5 Application Cases
quality evaluation are as shown in Table 5.52.
As shown in Table 5.52, there are pollutants far exceeding the limits at all of the
three sampling sites. In light of this, the overall groundwater quality at the sampling
sites is rated Grade V. At No. 1 sampling site, ammonia nitrogen and permanganate
index reach Grade V standards and arsenic Grade IV standard. At the other two
sampling sites, permanganate index reaches Grade V standard and arsenic and
nickel Grade IV standards. In general, the groundwater quality in the OCS site is
poor, but there is no excess of organic pollutants such as benzene and toluene.
(3) Groundwater pollution source intensity evaluation
(a) Pollution source hazard rating
• Indicators, weights and scores
The characteristic pollutants of the OCS site include petroleum, sulfide, total cyanide, benzene and toluene. Since the monitoring data are available for petroleum
and sulfide only, petroleum, sulfide and total cyanide are selected as pollution
factors for evaluation. The pollutants are discharged in the vadose zone with a
source intensity of less than 50 Â 10
4 m
3 /a. The pollution through continuous
infiltration affects more than 10% of the total area. The pollution sources exist for
over 20 years, and the seepage control relies on partial seal.
Using the aforementioned method, indicator-specific scores are given: 10 for
comprehensive evaluation of pollution factors (Z1), 1 for discharge source intensity
(Z2), 8 for location of discharge (Z3), 8 for mode of discharge (Z4), 10 for affected
area (Z5), 5 for seepage control measures (Z6), and 10 for duration of existence (Z7).
Table 5.52 Results of groundwater quality assessment
Items
No. 1 sampling site
No. 2 sampling site
No. 3 sampling site
p H
I
I
I
Ammonia nitrogen
V
III
III
Permanganate index
V
V
V
Hexavalent chromium
I
I
I
Arsenic
IV
IV
IV
Lead
I
I
I
Mercury
III
III
III
nickel
III
IV
IV
Benzene
I
I
I
Toluene
I
I
I
Ethylbenzene
I
I
I
Xylene
I
I
I
Grade of water quality
V
V
V
Level of water quality
Very poor
Very poor
Very poor
192
5 Application Cases