assessment needs to consider (a) the capacity of aquifer systems against pollution
and the impact of external pollution load associated with human activities, as well
as (b) the change in groundwater value/functions and the migration and attenuation
of external pollutants in the soil-groundwater system (Guo et al. 2012; Hong et al.
2011; Javadi et al. 2011; Wang and Ji 2010). At present, the assessment and study
of groundwater pollution risks include the assessments of intrinsic vulnerability and
specific vulnerability, identification of external pollutant types and hazard levels,
and groundwater value/function evaluation (Wang 2013; Kou et al. 2013; Jin et al.
2012; Li et al. 2008; Shi 2013; Wang et al. 2012; Yang et al. 2010).
4.2.1 Assessment of Intrinsic Vulnerability
Intrinsic vulnerability, also known as inherent vulnerability, is a manifestation of
the groundwater system's capacity to adapt to changes in the external environment
(Huan et al. 2012; Focazio et al. 2003; Debernardi et al. 2008; Chen 2013). It is
highly stable as it emphasizes the natural attributes of regional aquifers. The
magnitude of intrinsic vulnerability is determined by many factors such as the depth
to water table, media in the seepage zone, and hydraulic conductivity of the aquifer
(Chen et al. 2002; China Geological Survey 2006; Hathhorn and Wubbena 1996). It
reflects the speed at which external pollutants reach the aquifer and the capacity of
the groundwater environment to absorb pollutants. The models for groundwater
vulnerability assessment currently used at home and abroad mainly include
DRASTIC, GOD, AVI, SEEPAGE, SINTACS and EPIK. They integrate basically
the same factors and highlights, but each has its own advantages (Chen et al. 2010;
Fan et al. 2007; Fu et al. 2000) (Table 4.3).
Among them, the DRASTIC model developed by the US EPA in 1985 is most
widely used to assess intrinsic vulnerability at home and abroad. It contains seven
indicators, and the calculation equation is written as follows:
V i ¼ D w D r þ R w R r þ A w A r þ S w S r þ T w T r þ I w I r þ C w C r
ð4:4Þ
wherein Vi represents the intrinsic vulnerability index; D denotes the depth to water
table, R net recharge of the aquifer; A aquifer media, S soil media, T topography,
I impact of vadose zone media, and C hydraulic conductivity; subscript r and
w indicate the rating and weight of the indicator respectively. The intrinsic vulnerability index is obtained by model weighting, and further the vulnerability index
is rated.
The research on the intrinsic vulnerability of groundwater serves as an embryonic form of groundwater pollution contamination assessment. It in essence simply
superimposed the natural attributes of groundwater environment on regional conditions such as hydrogeology, land use and climate. Assessment at this stage mainly
rested on the linear assessment model based on the exponential superposition
4.2 Groundwater Pollution Risk Assessment of Typical Groundwater …
81
and the impact of external pollution load associated with human activities, as well
as (b) the change in groundwater value/functions and the migration and attenuation
of external pollutants in the soil-groundwater system (Guo et al. 2012; Hong et al.
2011; Javadi et al. 2011; Wang and Ji 2010). At present, the assessment and study
of groundwater pollution risks include the assessments of intrinsic vulnerability and
specific vulnerability, identification of external pollutant types and hazard levels,
and groundwater value/function evaluation (Wang 2013; Kou et al. 2013; Jin et al.
2012; Li et al. 2008; Shi 2013; Wang et al. 2012; Yang et al. 2010).
4.2.1 Assessment of Intrinsic Vulnerability
Intrinsic vulnerability, also known as inherent vulnerability, is a manifestation of
the groundwater system's capacity to adapt to changes in the external environment
(Huan et al. 2012; Focazio et al. 2003; Debernardi et al. 2008; Chen 2013). It is
highly stable as it emphasizes the natural attributes of regional aquifers. The
magnitude of intrinsic vulnerability is determined by many factors such as the depth
to water table, media in the seepage zone, and hydraulic conductivity of the aquifer
(Chen et al. 2002; China Geological Survey 2006; Hathhorn and Wubbena 1996). It
reflects the speed at which external pollutants reach the aquifer and the capacity of
the groundwater environment to absorb pollutants. The models for groundwater
vulnerability assessment currently used at home and abroad mainly include
DRASTIC, GOD, AVI, SEEPAGE, SINTACS and EPIK. They integrate basically
the same factors and highlights, but each has its own advantages (Chen et al. 2010;
Fan et al. 2007; Fu et al. 2000) (Table 4.3).
Among them, the DRASTIC model developed by the US EPA in 1985 is most
widely used to assess intrinsic vulnerability at home and abroad. It contains seven
indicators, and the calculation equation is written as follows:
V i ¼ D w D r þ R w R r þ A w A r þ S w S r þ T w T r þ I w I r þ C w C r
ð4:4Þ
wherein Vi represents the intrinsic vulnerability index; D denotes the depth to water
table, R net recharge of the aquifer; A aquifer media, S soil media, T topography,
I impact of vadose zone media, and C hydraulic conductivity; subscript r and
w indicate the rating and weight of the indicator respectively. The intrinsic vulnerability index is obtained by model weighting, and further the vulnerability index
is rated.
The research on the intrinsic vulnerability of groundwater serves as an embryonic form of groundwater pollution contamination assessment. It in essence simply
superimposed the natural attributes of groundwater environment on regional conditions such as hydrogeology, land use and climate. Assessment at this stage mainly
rested on the linear assessment model based on the exponential superposition
4.2 Groundwater Pollution Risk Assessment of Typical Groundwater …
81