Phenolic compounds are the main pollutants existing in wastewater and solid
waste from coking, dyeing, papermaking, medicine, and chemical industries. The
phenol contamination of groundwater can be mainly attributed to anthropogenic
factors. The background values for phenol identified at BJ7 are below the limits, but
excessive concentrations were detected in the landfill leachate and at ZK2 and ZK3
near the landfill with waste stacked. It is considered that there is phenol pollution in
the fissure water near ZK2 and ZK3, mainly caused by the landfill.
PAHs are widely distributed in the environment, and may be produced in any
place where organic matter is processed, discarded, burned or used. In the study
area, only PAHs were detected at ZK3, but not in the landfill leachate, so the
pollution sources exclude landfill leachate.
In short, based on data collection and on-site investigation, combined with the
hydrogeological data and the results of groundwater quality assessment and
groundwater pollution evaluation, it is preliminarily concluded that the fissure water
of the landfill suffers from sodium, chloride, ammonium, nitrite, total phosphorus,
aluminum, nickel and phenol pollution caused by the landfill. In addition, organic
pesticides (lindane, DDT, atrazine) are also detected in the landfill.
• Pollution pathways
According to the preceding analysis, it can be concluded that the groundwater in the
study area is contaminated in both direct and indirect ways. The direct pollution is
caused by the infiltration of sewage from sewers into the aquifer. The indirect
pollution is associated with the entry of pollutants remaining in the landfill into the
aquifer via the vadose zone through precipitation and leaching.
The pathways for pollution in the study area can be divided into continuous
infiltration and intermittent infiltration. The infiltration of pollutants from sewers
into the aquifer is considered as continuous infiltration, while the infiltration via
precipitation and leaching is deemed as intermittent infiltration.
Regardless of pathways, pollutants enter the aquifer from top to bottom through
the upper weathering zones. Therefore, the degree of groundwater contamination
depends mainly on the geological structure, material composition, thickness and
permeability of the upper soil layer. As the soil structure is quite different within the
study area, the monitoring sites show varying degrees of groundwater
contamination.
(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: 2
for landfill volume (Y1) which reaches 2250 m
3 ; 1 for landfill period (Y2) spans
20 years; 10 for landfill type (Y4) as mainly MSW and hazardous waste are
landfilled; 10 for maximum leachate production (Y3) which attains 25 Â 10
4 m
3 /a;
10 for seepage control (Y5) which relies on the natural soil layer; and 10 for
leachate treatment (Y6) as there no collection or treatment system.
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141
waste from coking, dyeing, papermaking, medicine, and chemical industries. The
phenol contamination of groundwater can be mainly attributed to anthropogenic
factors. The background values for phenol identified at BJ7 are below the limits, but
excessive concentrations were detected in the landfill leachate and at ZK2 and ZK3
near the landfill with waste stacked. It is considered that there is phenol pollution in
the fissure water near ZK2 and ZK3, mainly caused by the landfill.
PAHs are widely distributed in the environment, and may be produced in any
place where organic matter is processed, discarded, burned or used. In the study
area, only PAHs were detected at ZK3, but not in the landfill leachate, so the
pollution sources exclude landfill leachate.
In short, based on data collection and on-site investigation, combined with the
hydrogeological data and the results of groundwater quality assessment and
groundwater pollution evaluation, it is preliminarily concluded that the fissure water
of the landfill suffers from sodium, chloride, ammonium, nitrite, total phosphorus,
aluminum, nickel and phenol pollution caused by the landfill. In addition, organic
pesticides (lindane, DDT, atrazine) are also detected in the landfill.
• Pollution pathways
According to the preceding analysis, it can be concluded that the groundwater in the
study area is contaminated in both direct and indirect ways. The direct pollution is
caused by the infiltration of sewage from sewers into the aquifer. The indirect
pollution is associated with the entry of pollutants remaining in the landfill into the
aquifer via the vadose zone through precipitation and leaching.
The pathways for pollution in the study area can be divided into continuous
infiltration and intermittent infiltration. The infiltration of pollutants from sewers
into the aquifer is considered as continuous infiltration, while the infiltration via
precipitation and leaching is deemed as intermittent infiltration.
Regardless of pathways, pollutants enter the aquifer from top to bottom through
the upper weathering zones. Therefore, the degree of groundwater contamination
depends mainly on the geological structure, material composition, thickness and
permeability of the upper soil layer. As the soil structure is quite different within the
study area, the monitoring sites show varying degrees of groundwater
contamination.
(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: 2
for landfill volume (Y1) which reaches 2250 m
3 ; 1 for landfill period (Y2) spans
20 years; 10 for landfill type (Y4) as mainly MSW and hazardous waste are
landfilled; 10 for maximum leachate production (Y3) which attains 25 Â 10
4 m
3 /a;
10 for seepage control (Y5) which relies on the natural soil layer; and 10 for
leachate treatment (Y6) as there no collection or treatment system.
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141