According to the analysis of the cross-sectional layer data of the landfill site, the
waste soil of the landfill site is in direct contact with the peripheral aquifer. The
floor of MSW has an elevation of 17.52–37.40 m, mostly lower than the elevation
of the 1st layer of groundwater (25.74–30.61 m). There is a close hydraulic correlation between the leachate in the garbage body and the 1st layer of groundwater
in the area.
3. Assessment of environmental conditions of groundwater in the informal
landfill
(1) Groundwater environmental quality of landfill
There are 3 layers of groundwater continuously distributed in the depth of 48 m
below the landfill, respectively phreatic water, interlayer water and confined water.
In addition, there are 1 minor layer of fine sand and 3 minor layers of silty sand and
silt distributed in lenticular shape in the 6th major layer of clayey soil of the landfill
site. Groundwater might be distributed in these minor layers. In this investigation, a
total of 15 water samples from various layers of groundwater within 48 m below
the landfill and surrounding ground were collected. The test indicator are divided
into three categories: ① a total of 27 conventional test items, including pH value,
permanganate index, chromaticity, nitrates, nitrites, total hardness, ammonia
nitrogen, total dissolved solids, fluoride, sulfate, cyanide, chloride, volatile phenols,
CODcr, total nitrogen, BOD 5 , total phosphorus, fecal coliforms, total coliforms,
suspended solids, K
+ , Na
+
, Ca
2+ , Mg
2+ , NH 4
+ , CO 3
2− , HCO 3
− , etc. ② a total of 10
heavy metal test indicators: mercury, iron, arsenic, manganese, cadmium, copper,
chromium, zinc, hexavalent chromium, lead, etc. ③ a total of 21 volatile organic
compounds indicators: 1,2-dichloroethane, dichloromethane, trihalomethane,
1,1,1-trichloroethane, tribromomethane, etc.
According to the test results, among the conventional test indicators, cyanide and
carbonate concentration are below the detectable limits; among the heavy metals
indicators, the measurement results of a total of 4 items including mercury, cadmium, hexavalent chromium and chromium are below the detectable thresholds;
among the volatile organic compounds indicators, the concentrations of 13 items
including 1,2-dichloroethane, trihalomethane, 1,1,1-trichloroethane, tribromomethane, 1,1-dichloroethylene, 1,2-dichlorobenzene, 1,4-dichloro benzene, trichlorethylene, trichlorobenzene (total), hexachlorobutadiene, tetrachlorethylene, di
(2-ethylhexyl) phthalate and vinyl chloride are below the detectable thresholds.
Detection results are obtained for all other indicators. The distribution of COD and
ammonia-nitrogen concentrations in the groundwater at the landfill site is shown in
Figs. 5.44, 5.45, 5.46, 5.47, 5.48 and 5.49.
It can be known from the above analysis:
① In the 3 layers of continuously distributed groundwater at the landfill site, the
indicators of iron, manganese and arsenic exceeded the standard slightly; none
of the volatile organic compounds indicators exceeded the standard; among
the conventional indicators, COD Cr , ammonia-nitrogen, total nitrogen and
total phosphorus exceeded the standard.
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257
waste soil of the landfill site is in direct contact with the peripheral aquifer. The
floor of MSW has an elevation of 17.52–37.40 m, mostly lower than the elevation
of the 1st layer of groundwater (25.74–30.61 m). There is a close hydraulic correlation between the leachate in the garbage body and the 1st layer of groundwater
in the area.
3. Assessment of environmental conditions of groundwater in the informal
landfill
(1) Groundwater environmental quality of landfill
There are 3 layers of groundwater continuously distributed in the depth of 48 m
below the landfill, respectively phreatic water, interlayer water and confined water.
In addition, there are 1 minor layer of fine sand and 3 minor layers of silty sand and
silt distributed in lenticular shape in the 6th major layer of clayey soil of the landfill
site. Groundwater might be distributed in these minor layers. In this investigation, a
total of 15 water samples from various layers of groundwater within 48 m below
the landfill and surrounding ground were collected. The test indicator are divided
into three categories: ① a total of 27 conventional test items, including pH value,
permanganate index, chromaticity, nitrates, nitrites, total hardness, ammonia
nitrogen, total dissolved solids, fluoride, sulfate, cyanide, chloride, volatile phenols,
CODcr, total nitrogen, BOD 5 , total phosphorus, fecal coliforms, total coliforms,
suspended solids, K
+ , Na
+
, Ca
2+ , Mg
2+ , NH 4
+ , CO 3
2− , HCO 3
− , etc. ② a total of 10
heavy metal test indicators: mercury, iron, arsenic, manganese, cadmium, copper,
chromium, zinc, hexavalent chromium, lead, etc. ③ a total of 21 volatile organic
compounds indicators: 1,2-dichloroethane, dichloromethane, trihalomethane,
1,1,1-trichloroethane, tribromomethane, etc.
According to the test results, among the conventional test indicators, cyanide and
carbonate concentration are below the detectable limits; among the heavy metals
indicators, the measurement results of a total of 4 items including mercury, cadmium, hexavalent chromium and chromium are below the detectable thresholds;
among the volatile organic compounds indicators, the concentrations of 13 items
including 1,2-dichloroethane, trihalomethane, 1,1,1-trichloroethane, tribromomethane, 1,1-dichloroethylene, 1,2-dichlorobenzene, 1,4-dichloro benzene, trichlorethylene, trichlorobenzene (total), hexachlorobutadiene, tetrachlorethylene, di
(2-ethylhexyl) phthalate and vinyl chloride are below the detectable thresholds.
Detection results are obtained for all other indicators. The distribution of COD and
ammonia-nitrogen concentrations in the groundwater at the landfill site is shown in
Figs. 5.44, 5.45, 5.46, 5.47, 5.48 and 5.49.
It can be known from the above analysis:
① In the 3 layers of continuously distributed groundwater at the landfill site, the
indicators of iron, manganese and arsenic exceeded the standard slightly; none
of the volatile organic compounds indicators exceeded the standard; among
the conventional indicators, COD Cr , ammonia-nitrogen, total nitrogen and
total phosphorus exceeded the standard.
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