to produce leachate that discharges contaminants in the hazardous waste beyond
landfills. If not well collected and treated, such leachate will contaminate groundwater sources (Sun 2012).
Due to factors such as improper pretreatment measures, the leachate produced in
China’s typical HWLFs, which contains hazardous components, undermines more
seriously the groundwater safety and human health in the surrounding areas.
(4) Leakage source intensity
Field investigation, testing and sampling found a common risk of leakage in the
impervious layer in China’s typical HWLFs. The leakage source intensity associated with leachate leakage seriously threatens the health of humans that rely on soil
and groundwater resources. The consequent persistent environmental risks have
attracted increasing attention of the state. The leakage source intensity involves the
volume of leachate produced and the concentration of contaminants contained
therein (Tang 2014).
• Volume of leachate
The amount of leachate produced is related to local hydrogeological conditions
such as precipitation and water content of landfilled waste. Given such great
uncertainties, it can be quantitatively described using the Monte Carlo method.
• Concentration of contaminants contained
The concentration of contaminants in the leachate refers to the concentration at
which the leachate begins to form after the landfill is closed. It is related to the types
and characteristics of landfilled hazardous waste, as well as precipitation, and can
be calculated using the equation recommended in the EPACMTP model.
3.1.3 Characteristic Factors of OCS Hazards
Pollution in OCS sites is mainly caused by crude oil, residual oil, solvent oil,
gasoline and diesel and dominated by benzene-related groundwater contamination
(Zhu 2015; Yao et al. 2012).
There are two ways of groundwater contamination in oilfield development:
infiltration and penetration, of which the former is more common and dominant
(Liu et al. 2010). The mud pit, oily sewage, oil sludge and casing oily sewage can
all infiltrate into the unconfined aquifer through the vadose zone and lead to
groundwater contamination (Tao et al. 2017). A thinner vadose zone has better
water permeability and weaker pollution-proof capacity and more facilitates pollution in the unconfined aquifer, and vice versa. Penetration mainly occurs to the
reinjection water returned outside casing during the oil recovery process and to the
mud pit during the drilling process (Li et al. 2016). In the process of oil recovery, if
there is an accident of water return, the oily sewage can directly enter the aquifer in
the path of return under the effect of water head pressure difference, and then diffuse
36
3 Rating and Evaluation of Pollution Source Intensity …
landfills. If not well collected and treated, such leachate will contaminate groundwater sources (Sun 2012).
Due to factors such as improper pretreatment measures, the leachate produced in
China’s typical HWLFs, which contains hazardous components, undermines more
seriously the groundwater safety and human health in the surrounding areas.
(4) Leakage source intensity
Field investigation, testing and sampling found a common risk of leakage in the
impervious layer in China’s typical HWLFs. The leakage source intensity associated with leachate leakage seriously threatens the health of humans that rely on soil
and groundwater resources. The consequent persistent environmental risks have
attracted increasing attention of the state. The leakage source intensity involves the
volume of leachate produced and the concentration of contaminants contained
therein (Tang 2014).
• Volume of leachate
The amount of leachate produced is related to local hydrogeological conditions
such as precipitation and water content of landfilled waste. Given such great
uncertainties, it can be quantitatively described using the Monte Carlo method.
• Concentration of contaminants contained
The concentration of contaminants in the leachate refers to the concentration at
which the leachate begins to form after the landfill is closed. It is related to the types
and characteristics of landfilled hazardous waste, as well as precipitation, and can
be calculated using the equation recommended in the EPACMTP model.
3.1.3 Characteristic Factors of OCS Hazards
Pollution in OCS sites is mainly caused by crude oil, residual oil, solvent oil,
gasoline and diesel and dominated by benzene-related groundwater contamination
(Zhu 2015; Yao et al. 2012).
There are two ways of groundwater contamination in oilfield development:
infiltration and penetration, of which the former is more common and dominant
(Liu et al. 2010). The mud pit, oily sewage, oil sludge and casing oily sewage can
all infiltrate into the unconfined aquifer through the vadose zone and lead to
groundwater contamination (Tao et al. 2017). A thinner vadose zone has better
water permeability and weaker pollution-proof capacity and more facilitates pollution in the unconfined aquifer, and vice versa. Penetration mainly occurs to the
reinjection water returned outside casing during the oil recovery process and to the
mud pit during the drilling process (Li et al. 2016). In the process of oil recovery, if
there is an accident of water return, the oily sewage can directly enter the aquifer in
the path of return under the effect of water head pressure difference, and then diffuse
36
3 Rating and Evaluation of Pollution Source Intensity …