The Effects of Road Transport on Freshwater and Marine Ecosystems

34
(1995) provide a general review <strong>of</strong> VOC data in general urban stormwater run<strong>of</strong>f that was available up
to that time.
<strong>The</strong> United States Geological Survey (USGS) carried out a survey <strong>of</strong> volatile organic compounds
(VOC) in stormwater in 16 US cities required to obtain National Pollution Discharge Elimination system
permits (Delzer et al. 1996). It should be noted that detection was influenced by detection limit
compared to other VOCs and the seasonality <strong>of</strong> MTBE emissions in some areas (due to winter use).
MTBE detections ranged from 0.2 to 8.7 mg/m 3 (median 1.5 mg/m 3 ). <strong>The</strong> survey conducted from 1991
to 1995 found that the most prevalent VOCs were toluene, total xylenes, chlor<strong>of</strong>orm, total trimethylbenzene,
tetrachloroethene and naphthalene followed by MTBE. MTBE was detected in 6.9%
<strong>of</strong> the stormwater samples. Table 4.9 provides a summary <strong>of</strong> the data for selected constituents
measured in the USGS survey.
Table 4.9 - VOCs in United States stormwater (all data mg/m 3 ) (From Delzer et al. 1996).
Parameter Median Minimum Maximum Detection
Frequency %
Toluene 0.3 0.02 6.6 23.2
Total xylene 0.4 0.2 15.0 17.5
Total trimethyl-benzene 0.3 0.2 15.0 12.4
Naphthalene 0.3 0.2 5.1 7.4
MTBE 1.5 0.2 8.7 6.9
Ethylbenzene 0.3 0.2 2.0 5.0
Studies on the spatial variability <strong>of</strong> VOCs in streams on Long Island and New Jersey have been
reported by O’Brien et al. (1997). Streams sampled contained urban run<strong>of</strong>f and other discharges. A
range <strong>of</strong> VOCs were detected <strong>of</strong> these naphthalene and MTBE were specifically identified as being
sourced from motor vehicles. Acetone was detected but has a variety <strong>of</strong> sources in the urban
environment. A range <strong>of</strong> VOCs were not detected at a detection limit typically <strong>of</strong> 0.05 – 0.10 mg/m 3 .
No other identified vehicle VOC emission compounds were identified.
Lopes & Dionne (1998) reviewed the occurrence <strong>of</strong> VOCs in urban stormwater and highway run<strong>of</strong>f.
VOC data for highways is limited. Chloromethane, toluene, xylenes, 1,2,4–trimethylbenzene and
1,2,3–trichlopropene have been detected in highway run<strong>of</strong>f in Texas.
Fuel related VOCs are present in urban waterways because <strong>of</strong> their prevalence in the urban
environment. Terracciano & O’Brien (1998) reported on VOCs in streams on Long Island, New York.
A number <strong>of</strong> VOCs were commonly detected in samples. <strong>The</strong>se included 1,1,1-trichloroethane (TCA),
TTBE, tetrachloroethene, total benzene, toluene, ethylbenzene and xylene. Higher concentrations
and frequency <strong>of</strong> detection was found in winter when volatility was at its lowest. <strong>The</strong> low level
concentrations <strong>of</strong> MTBE measured in stream waters in the United States has been considered to
result from equilibration between atmospheric MTBE and stream water rather than direct discharge.
<strong>The</strong>re appears to be no data on the concentration <strong>of</strong> VOCs in New Zealand urban and motorway
stormwater. Overseas data indicates that the concentration <strong>of</strong> most VOCs in stormwater are low.
4.4.3 PAHs
Based upon PAH concentrations found in fine particle size fractions <strong>of</strong> urban gutter dusts, ARC (1992)
estimated the PAH concentrations in urban stormwater run<strong>of</strong>f from residential and industrial roadways
in Auckland. Total PAH concentrations were estimated to be 62.2 µg/m 3 and 27.1 µg/m 3 in the
Pakuranga and Southdown catchments respectively. No specific monitoring <strong>of</strong> PAHs in stormwater in
New Zealand was available until recently (Sherriff 1998, Brown et al. 2003, O’Reilly et al. 2002 and
Timperley et al. 2003).
Kingett Mitchell Ltd
Resource & Environmental Consultants