The impact of urban groundwater upon surface water - eTheses ...

WATER QUALITY INTERACTIONS
extent. An additional reason for the high levels of VOCs detected in the abstraction wells is
that many are associated with industries that use VOCs on site. The use of these compounds is
specialised and generally restricted to these locations rather than the more widespread
distribution of the inorganic contaminant sources such as chloride.
Sample Type
Abstraction
Wells
Shallow
Groundwater
Riverbed
Piezometers
Number of
samples
Samples in which
VOCs were
detected (%)
Samples in which
total VOC content
14 79 50 114 879
20 60 95 4 70
44 82 79 13 210
Surface Water 3 100 67 8 11
Table 7.5 The level of total VOC contamination in the aquifer (analysis was for a range of 52
VOCs)
The most frequently detected compounds were Trichloroethene (TCE), cis 1,2-Dichloroethene
(DCE), Tetrachloroethene (PCE), Trichloromethane (TCM, chloroform), 1,1-Dichloroethane
(DCA), and 1,1,1-Trichloroethane (TCA). This is in agreement with results from the sampling
of abstraction wells in the Birmingham Aquifer undertaken by previous workers (Rivett, 1990
and Taylor et al., 1999). Both TCE and TCA are widely used for metal degreasing by industry
in the Tame Valley and the primary use of PCE is in dry cleaning. TCM is a by-product of
water treatment processes and may indicate leakage from water mains or sewer pipes. TCM
285
< 10 μgl -1 (%).
Mean Total VOC
content (μgl -1 )
Maximum Total
VOC content
(μgl -1 )