Environmental Engineering Reference
In-Depth Information
systems that include video images are used for these contaminants [LIE 98]. The
soil in contact with the sapphire window is scanned using a miniature color digital
camera located in the penetrometer. The image is displayed on the surface using a
video monitor and recorded using a video cassette recorder. Light-emitting diodes
are used to illuminate the ground. The field tests conducted by [LIE 98] on a site
polluted with chlorinated solvents and fuels have shown that NAPL contaminants
were easily identified in the visual display. NAPL bubbles were observed, as well as
gas bubbles associated with NAPL bubbles.
An example of a fluorescence intensity profile of a site polluted with petroleum
products [JAC 97] is shown in Figure 12.10. This profile provides ongoing
identification of pollutants without interrupting the cone penetration. Data were
collected every second or 20 mm during the penetration. The spectrum of light
entering into fluorescence, because of the contamination, is associated with multiple
wavelengths. The intensity distribution of wavelengths indicates the type of
hydrocarbon contaminants.
CONTAMINANT
IDENTITY
FLUORESCENCE
SPRECTRUM
0
3
6
9
12
15
18
21
24
27
30
33
36
39
0 25 50 75 100 125
Total Fluorescence Intensity
(%)
Figure 12.10.
Continuous identification of pollution by
hydrocarbons with LIF [JAC 97]
Olie
et al.
[OLI 94] have also developed a CPT with a fluorescent probe. The
probe contains a light source (ultraviolet) as well as a fluorescence detection system.
No fiber optic cable is necessary because the detection system is located in the
probe. During penetration, the measurements are made by illuminating the material
surrounding the probe with a small mercury lamp to produce the source of
ultraviolet light. The fluorescence emitted is detected in the probe by a small
