Page 247 - Hydrogeology Principles and Practice

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230 Chapter Six

Table 6.5 Sources of organic contaminants found in urban groundwaters. After Lloyd et al. (1991).

Chemical class Sources Examples
Aliphatic and aromatic hydrocarbons Petrochemical industry wastes Benzene
(including benzenes, phenols and Heavy/fine chemicals industry wastes Toluene
petroleum hydrocarbons) Industrial solvent wastes Iso-octane
Plastics, resins, synthetic fibres, rubbers and paints production Hexadecane
Coke oven and coal gasification plant effluents Phenol
Urban runoff
Disposal of oil and lubricating wastes
Polynuclear aromatic hydrocarbons Urban runoff Anthracene
Petrochemical industry wastes Pyrene
Various high temperature pyrolytic processes
Bitumen production
Electrolytic aluminium smelting
Coal-tar coated distribution pipes
Halogenated aliphatic and aromatic Disinfection of water and waste water Trichloroethylene
hydrocarbons Heavy/fine chemicals industry waste Trichloroethane
Industrial solvent wastes and dry cleaning wastes Para-dichlorobenzene
Plastics, resins, synthetic fibres, rubbers and paints production
Heat-transfer agents
Aerosol propellants
Fumigants
Polychlorinated biphenyls Capacitor and transformer manufacture Pentachlorobiphenyls
Disposal of hydraulic fluids and lubricants
Waste carbonless copy paper recycling
Heat transfer fluids
Investment casting industries
PCB production
Phthalate esters Plastics, resins, synthetic fibres, rubbers and paints production
Heavy/fine chemicals industry wastes
Synthetic polymer distribution pipes

sampled that contained chlorinated solvents were Several factors were shown by Rivett et al. (1990)
located on the sites of metal manufacturing and to explain the distribution of organic contaminants
processing and mechanical engineering industries. including the historic use of solvents, point source
The results are shown in Table 6.6 and Fig. 6.19 and inputs close to sampling boreholes, thickness of the
indicate that chlorinated solvents are widespread, in unsaturated zone, the presence or absence of con-
particular TCE which is detected in 78% of bore- fining deposits above the aquifer and the depth of
holes. TCE is frequently observed at high levels with groundwater sampling. Higher concentrations of sol-
40% of boreholes contaminated above 30 µgL −1 to vents were found at deeper sampling levels, by virtue
a maximum of 5500 µgL −1 (Rivett et al. 1990). of their DNAPL behaviour, while the opposite was
Occasional high values are also observed for TCA and the case for hydrocarbons (LNAPLs).
PCE, the latter associated with dry cleaning laundry Urban districts can extend over wide areas of aquifer
sites. Contamination of the Birmingham aquifer by outcrop below which is a large volume of potentially
organic chemicals other than chlorinated solvents available water; a contrasting situation with adjacent
is low in the supply boreholes and, where present, rural areas where groundwater sources are increas-
is often associated with degraded lubricating oils. ingly fully developed (Lerner 2002). However, research