The Effects of Road Transport on Freshwater and Marine Ecosystems

More documents

Recommendations

Info

50 Figure 5.1 - Percentage <strong>of</strong> 0.5 M HCl extractable elements in road surface sediments from Moana Basin, Hawaii (From Sutherland & Tolosa 2000). <strong>The</strong> proportions present in the various phases, provides some information about the environmental mobility under those experimental conditions and probably the broad environmental mobility. <strong>The</strong> general mobility does not directly relate to the proportion present in the dissolved phase. Examination <strong>of</strong> the dissolved data presented earlier suggests that for Pb and Cd, the exchangeable fraction may control much <strong>of</strong> the dissolution process for these elements with some contribution from the carbonate phase. For Zn the exchangeable phase does not contribute much <strong>of</strong> the Zn seen in storm events and it is likely that this is sourced from carbonate and oxide phases. For Cu, the dissolved copper is likely to come from both organic and oxide phases in street surface particulates. Revitt & Morrison (1987) concluded following an assessment <strong>of</strong> speciation <strong>of</strong> key metals through the stormwater system that the proportion considered bioavailable were 59%, 53% 38% and 5% for Cd, Zn, Cu and Pb. <strong>The</strong> implications <strong>of</strong> the relative bioavailability, is discussed further in the following sections on effects in freshwaters and marine waters. Overall, geochemical processes on the road surface affect the behaviour and form <strong>of</strong> inorganic materials, compounds and metals on the road surface before and during storm events. <strong>The</strong> key factor is the affect <strong>of</strong> low pH (acidic) rainwater and the dissolution processes that move metals from solid phase to dissolved phases in stormwater. Although the exact processes are not known for all key metal contaminants, available information indicates that while on the road surface metals undergo phase re-distribution. Organic Compounds VOCs will be present in rainfall in concentrations that reflect their concentration in air and ambient temperature. VOCs will undergo processes whilst in urban air through reactions with other atmospheric constituents, such as hydroxyl radicals, which result in degradation. Volatilisation <strong>of</strong> VOCs from street surfaces and particulates is temperature dependent. In a reversal <strong>of</strong> this physical process, the atmosphere may also contribute VOCs to water, especially in cold weather. Air/water partitioning <strong>of</strong> VOCs is described by their Henrys Law constant (H) which identifies the ratio <strong>of</strong> the partial pressure <strong>of</strong> the compound in the gas phase to the concentration in the water that is in equilibrium with the atmosphere. A second dimensionless constant (H/RT) is derived using H, gas constant and temperature which provides the ratio <strong>of</strong> air to water concentrations at equilibrium. A VOC with an H/RT value <strong>of</strong> 0.05 or larger will be volatile when in water (e.g., BTEX in Table 3.2). Compounds such as MTBE which have lower H/RT values will tend to partition from the gas phase Kingett Mitchell Ltd Resource & Environmental Consultants
51 into water. Hence concentrations <strong>of</strong> MTBE in rain and water tend to be present in relatively constant concentrations. VOCs such as BTEX and MTBE have low partition coefficients with organic carbon (Koc). Coefficients for benzene (~80) are such that some retention by organic carbon will occur. <strong>The</strong> coefficient for MTBE is ~11 and little retention by organic carbon will occur. BTEX compounds are more biodegradable than MTBE. MTBE is considered relatively re-calcitrant and is not influenced by processes such as hydrolysis and photolysis. Table 5.2 - Summary <strong>of</strong> key physical properties <strong>of</strong> key VOCs. Property Benzene Toluene Ethylbenzene m,o,p Xylene MTBE Molecular weight 78.11 92.13 106.16 106.16 88.15 Specific gravity 0.8765 0.8661 0.867 0.861-0.88 0.744 Water solubility (mg/L) 1,780 534 140 178 50,000 Vapour pressure (25° C, mm Hg) 76 36.7 9.53 6.61 245-256 Log K ow 2.15 2.69 3.15 3.12 1.2 Log K oc 2.16 2.18 2.94 2.32 1.035-1.091 Henry’s Law Constant (H) (atm-m 3 )/(g-mole) 5.43x10 -3 5.95x10 -3 7.89x10 -3 6.56x10 -3 0.59-3.0x10 -3 Dimensionless Henrys Law Constant (H/RT) 0.22 0.243 0.323 0.268 0.02-0.12 Note: Log Kow = octonal/water partitioning coefficient. Log Koc = octonal/carbon partitioning coefficient. In relation to a number <strong>of</strong> the key VOCs emitted by vehicles the following comments can be made. Benzene Benzene is an aromatic hydrocarbon, it is non-polar and is relatively soluble in water (Table 5.2). Benzene is a stable molecule and is relatively un-reactive in the atmosphere. Slow oxidation <strong>of</strong> benzene will produce phenols and aldehydes (e.g., glyoxal [CHO]2). Both products are highly reactive and water-soluble and will be rapidly removed from the atmosphere by rain (USEPA 1993). Benzene’s low aqueous solubility limits its concentration in rain. Ethylbenzene Ethylbenzene has limited solubility in water compared to benzene and xylene (Table 5.2). Volatilisation is probably the key process influencing the fate <strong>of</strong> ethylbenzene. In water (1 m deep) a half life <strong>of</strong> about 5-6 hours has been estimated (Mackay & Leinonen 1975). A half life for atmospheric oxidation <strong>of</strong> 15 hours has been estimated. Degradation/breakdown pathways are complex with bacterial oxidation transforming ethylbenzene to compounds such as styrene (ethylbenzene). Toluene (Methylbenzene) Toluene has a moderate solubility in water (Table 5.2). <strong>The</strong> half-life in water (1 m deep) is estimated to be 5 hours. Some adsorption to organic matter and organic matter such sediments would be predicted from the log K ow . Atmospheric half life is estimated to be 15 hours. Formaldehyde Formaldehyde is very soluble in water (up to 55%) and reacts in water (hydrates) to form methylene glycol amongst other compounds. Decomposition <strong>of</strong> formaldehyde can produce a variety <strong>of</strong> compounds ranging from methanol to formic acid. In the atmosphere, formaldehyde is lost mainly through reaction with hydroxyl radicals and photolysis. <strong>The</strong> atmospheric residence time is relatively Kingett Mitchell Ltd Resource & Environmental Consultants
Page 1:
The Effect
Page 4 and 5:
Intentionally Blank ii
Page 6 and 7:
ii 4.2 Particulates in Urban Run<st
Page 8 and 9:
iv 7. IDENTIFICATION OF ENVIRONMENT
Page 10 and 11: vi MW Molecular weight N Nitrogen N
Page 12 and 13: 2 1. Moncrieff, I.; Kennedy, P. 200
Page 14 and 15: 4 Table 2.1 - Contaminant Source Cl
Page 16 and 17: 6 mg/kg) and Zn (25-34,500 mg/kg).
Page 18 and 19: 8 Bitumen Bitumen is produced in Ne
Page 20 and 21: 10 differences between petrol and d
Page 22 and 23: 12 on the nature of</strong
Page 24 and 25: 14 As such, available information i
Page 26 and 27: 16 An examination of</stron
Page 28 and 29: 18 Yang et al. (1999) examined the
Page 30 and 31: 20 to elevated concentrations in ty
Page 32 and 33: 22 sample of overs
Page 34 and 35: 24 suspension and that carried as b
Page 36 and 37: 26 Figure 4.1 - Variation in the co
Page 38 and 39: 28 Figure 4.2 - Variation in the co
Page 40 and 41: 30 Metal Cu Cd Pb Zn Table 4.6 - Su
Page 42 and 43: 32 probably reflect lower traffic d
Page 44 and 45: 34 (1995) provide a general review
Page 46 and 47: 36 Further data can be found in the
Page 48 and 49: 38 by ARC (1994) indicated that TPH
Page 50 and 51: 40 Cations/Anions Common ionic cons
Page 52 and 53: 42 Catchpits Between the street sur
Page 54 and 55: 44 5 PATHWAYS & FATE OF CONTAMINANT
Page 56 and 57: 46 The material wh
Page 58 and 59: 48 crystalline species present were
Page 62 and 63: 52 short (e.g., < 1 day). In water,
Page 64 and 65: 54 5.4.2 Dispersion Dilution and di
Page 66 and 67: 56 5.6 Summary The
Page 68 and 69: 58 6.2 Freshwater Ecosystems 6.2.1
Page 70 and 71: 60 General Assessment Tools Commonl
Page 72 and 73: 62 3. Increasing sediment inputs. 4
Page 74 and 75: 64 considered that taxa richness wa
Page 76 and 77: 66 Freshwater macro-invertebrate me
Page 78 and 79: 68 runoff to fish
Page 80 and 81: 70 deposition, tracking of<
Page 82 and 83: 72 one factor used to classify orga
Page 84 and 85: 74 Zinc Measurement of</str
Page 86 and 87: 76 in stormwater and receiving wate
Page 88 and 89: 78 minute; sub-mitochondrial partic
Page 90 and 91: 80 Toxicity tests have undertaken u
Page 92 and 93: 82 High molecular weight PAHs are t
Page 94 and 95: 84 Note: Sources refer Table 5.2. F
Page 96 and 97: 86 Although a range of</str
Page 98 and 99: 88 Bioaccumulation can be assessed
Page 100 and 101: 90 Figure 6.2 - metal concentration
Page 102 and 103: 92 6.5.3 Bioaccumulation of
Page 104 and 105: 94 Water Stormwater quality data fr
Page 106 and 107: 96 7. IDENTIFICATION OF ENVIRONMENT
Page 108 and 109: 98 3. Echinoderm (Fellaster zelandi
Page 110 and 111:
100 trace metals (probably Cu and Z
Page 112 and 113:
102 concentrations of</stro
Page 114 and 115:
104 that “concentrations
Page 116 and 117:
106 A large amount of</stro
Page 118 and 119:
108 A review of se
Page 120 and 121:
110 Samples of man
Page 122 and 123:
112 grazers such as mud flat snails
Page 124 and 125:
114 8. OVERVIEW 8.1 Vehicles as sou
Page 126 and 127:
116 The quality <s
Page 128 and 129:
118 International studies have show
Page 130 and 131:
120 A number of st
Page 132 and 133:
122 construction. Center for Resear
Page 134 and 135:
124 Carey, J.; Cook, P.; Ciesy, J.;
Page 136 and 137:
126 Ellis, J. B. 1986: Pollutional
Page 138 and 139:
128 Harrop D. O. 1984: Stormwater r
Page 140 and 141:
130 Kennedy, P. C.; Kjellstrom, T.
Page 142 and 143:
132 Maltby, L. A.; Boxall, D. M.; F
Page 144 and 145:
134 Novotny, V.; Muehring, D.; Zito
Page 146 and 147:
136 Ruck, J. 1998: Evaluation <stro
Page 148 and 149:
138 Terracciano, S. A.; O’Brien,
Page 150 and 151:
140 Webster, J. G.; Brown, K. L.; W
Page 152:
142 10. ACKNOWLEDGEMENTS Thanks to
show all

The Effects of Road Transport on Freshwater and Marine Ecosystems

Create successful ePaper yourself

Delete template?

Save as template?