3.1.4.2 Screening Main Control Factors Based on Specific
Vulnerability
In view of the specific vulnerability of vadose zone, “maximum pollution thickness
(M)” (Fig. 3.1) is introduced, which refers to the vertical distance from the location
of discharge by pollution sources to the groundwater table. A larger M value means
longer time that pollutants come into contact with soil media before entering the
groundwater. It allows for more complete reactions (adsorption, degradation, and
etc.), more significant attenuation, and better mitigation performance of vadose
zone, and vice versa.
The impact of vadose zone media on mitigation performance of vadose zone is
mainly manifested in the thickness of media particles and the degree of fissure
development. Finer media particles or less developed fissures denotes greater
adsorption and slower pollutant transport, which allows for more complete various
reactions of contaminants and better mitigation performance of vadose zone, and
vice versa. In addition, the impact of vadose zone media is also closely related to
the thickness of media. Thicker media implies better mitigation performance of
vadose zone. Therefore, vadose zone media are divided by the diameter of particles
into cohesive soil media and non-cohesive soil media. The thickness of cohesive
soil layer (M1) and the thickness of non-cohesive soil layer (M2) are taken as the
main factors of mitigation performance of vadose zone.
Fig. 3.1 Schematic diagram
of maximum contamination
thickness (M)
3.1 Indicators of Pollution Source Intensity Evaluation
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