Exhaust and Fuel Emissions in Water Supplies

Transcription

1 Exhaust and Fuel Emissions in Water Supplies Prepared by: Dr Graeme Batley CSIRO Division of Energy Technology Centre for Advanced Analytical Chemistry Lucas Heights Science and Technology Centre Private Mail Bag 7 Bangor NSW 2234

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3 Appendix E5 Exhaust and Fuel Emissions in Water Supplies Appendix E5 Exhaust and Fuel Emissions in Water Supplies Introduction As part of the next stage of the environmental impact statement (EIS) for Sydney's Second Airport, a more detailed commentary was required on the effects of aerial pollutants on catchments, Lake Burragorang and rainwater tanks. In particular this concerned polycyclic aromatic hydrocarbons (PAHs), benzene, butadiene, formaldehyde, phenol, and xylene. Such contaminants are associated with both combusted and uncombusted aviation fuel. Consideration would need to be given to expected emission levels, atmospheric fate and potential transport routes that might lead to them being deposited in areas of potential concern. This report addresses these issues. Polycyclic Aromatic Hydrocarbons 2.1 Impact on Reservoirs The presence of PAHs in aircraft exhaust has been well documented (Shabad and Smimov, 1972, 1976; Sears, 1978; Krahl et al., 1998). The United States Environment Protection Authority lists 16 PAHs that are especially relevant to environmental and human health. Of these, ten, namely fluoranthene, pyrene, benzo(a)anrhracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenz(a,h)anthracene, benzo(g,h,j)perylene and indeno(1,2,3,c,d) pyrene, have been used as preliminary fingerprints of aircraft turbines. There are concerns that PAHs could present a risk to drinking water and to aquatic life in Lake Burragorang and associated creeks and rivers in the catchment, as well as in rainwater tanks. It is appropriate to consider benzo(a)pyrene as representative of the above PAHs. Fortunately there has been a study that specifically dealt with releases of PP}( Environment 6, Infrastructure Pty Ltd Page E5-1

4 Second Sydney Airport Proposal Environmental Impact Statement Supplement benzo(a)pyrene from aircraft engines (Shabad and Smimov, 1972, 1976). This research showed that engine emissions amounted to between two and 10 milligrams per minute in Given improvements in aircraft engines since that time, it is likely that these numbers are now lower. Soot scraped from engine nozzles and exhaust pipes was reported to have contained 250 to 350 micrograms per kilogram (Shabad and Smirnov, 1972). While no rainfall data were provided, this study did analyse soil samples under aircraft corridors. Soil samples collected in the above study, at a 20 kilometre radius of a Moscow airport, contained not more than one microgram per kilogram of benzo(a)pyrene in surface soil, whereas under the flight corridor, up to 5.5 micrograms per kilogram were found. In areas of high industry and traffic, there was no detectable influence of aviation inputs. Snow samples were collected as a means of sampling dry deposition of benzo(a)pyrene. Adjacent to taxiways the snow accumulated in the range 1.0 to 2.2 micrograms per square metre within 150 metres of the main runway. This decreased to 0.28 micrograms per square metre at 1,800 metres from the runway and to 0.03 microgram per square metre at 10 to 15 kilometres distant. A separate study by McVeety and Hites (1988) showed that the ratio of dry to wet deposition is typically in a ratio of 9:1 for a number of United States studies. In their second paper, Shabad and Smirnov (1976) noted that the amount of benzo(a)pyrene discharged in a car park in a big city would be much higher than an aircraft because a single automobile engine discharges 10 microgram per minute of benzo(a)pyrene compared to a total airport estimate of 4 milligram per minute. It is important to note that PAHs are very hydrophobic organic compounds. This is reflected in octanol/water coefficients (K.,) having values between 10 3 and The larger ringed molecules, and those with greatest toxicity, have the highest values. In precipitation, there would therefore be very low water solubility of PAHs, and preferential association with atmospheric particulates, especially particulate organic carbon. On the basis of the Russian data, the annual fallout of benzo(a)pyrene at 15 kilometres distant from the airport would be of the order of 10 micrograms per square metre. Much of this will be particle associated. To translate this number to a number for Lake Burragorang requires many assumptions. These include assuming a size of the Moscow airport being studied in relation to the Second Sydney Airport. Furthermore we have no data for the greater distance from the airport that we would need to make comparisons in the Sydney case. If we assume a similar size airport and simply calculate the PAH concentration that might be added to the Lake per year on the basis of the projected Russian value for BaP of 10 micrograms per square metre, and use the Lake surface area of 74 square kilometres, and an average runoff to the Lake of 633,000 megalitres per year, the accumulated benzo(a)pyrene will be micrograms per litre. Expressed as total PAHs, this could be as high as 0.01 micrograms per litre. The Lake's catchment occupies 9,050 square kilometres, but any runoff from land surfaces would contribute only particulate-associated PAHs for the reasons discussed above. Page E5-2 Department of Transport and Regional Services

5 Appendix E5 Exhaust and Fuel Emissions 'n Water Supplies In natural fresh waters, the Australian and New Zealand Environment and Conservation Council (ANZECC) guideline for total PAHs is three micrograms per litre for ecosystem protection, and in drinking water, the health-related guideline value is 0.01 micrograms per litre. The specific interim guideline proposed for benzo(a)pyrene in water for ecosystem protection is 0.3 micrograms per litre. During water treatment, any PAH-containing suspended particulates present in reservoirs would be effectively removed during the coagulation, settling and filtration processes, to less than one nanogram per litre. No PAHs have been found in Australian drinking waters. Typical concentrations in drinking water in the United States are 0.55 nanograms per litre. The fate of PAHs entering water systems via dry atmospheric deposition would involve rapid partitioning to solid phases both in the vapour phase and in the water body, with ultimate accumulation in bottom sediments. Soot emissions from aircraft engines would form ideal surfaces for adsorption. When PAHs contact soils they would also bind strongly to organic matter. Their mobility would only be in the particulate phase, either as dust or washed off into streams by rain. Once in the water body, they are likely to eventually settle to the bottom. The particulate fraction is generally considered as being not bioavailable. Our own data on PAHs (Brockbank et al., 1998) show that the concentrations of benzo(a)pyrene from urban road runoff reach a maximum during a storm event of one microgram per litre, all principally attached to particles. On dilution in the receiving water, this would be significantly reduced. Again the soluble concentration will be low. Note that the concentrations of benzo(a)pyrene in the Parramatta River of 0.05 to one microgram per litre referred to in Technical Paper No. 7, from the paper by Smith et al. (1991), are total solvent extractable and not dissolved concentrations, which will also be lower. Total PAHs in rainfall, in the range nanograms per litre dissolved and nanograms per litre particulate, have been reported for an urban site in Switzerland (Leuenberger et al., 1988). There was a seasonal dependence, with lowest values found in summer and highest in winter. More recently, at a site 30 kilometres west of Minneapolis, USA, total PAHs of 41 nanograms per litre dissolved and 40 nanograms per litre particulate were found (Franz and Eisenreich, 1998). McVeety and Hites (1988) studying the atmospheric deposition of PAHs to water surfaces in Siskiwit Lake in northern Lake Superior, USA, showed that dry deposition was the predominant input (average dry to wet input of 9:1). For the most volatile PAHs (phenanthrene, and anthracene) approximately 80 percent of the wet and dry input was lost via surface volatilisation, whereas the least volatile showed no detectable loss. Outflow of lake water was an insignificant mechanism of PAM removal from the lake. The distributions of PAHs in the lake correlated with aqueous solubilities. Concentrations of PAHs decreased with water depth, consistent with removal by sedimenting particles. On the basis of the above findings, it is reasonable to conclude that PAN concentrations in Lake Burragorang would safely meet ecosystem guidelines. They may not necessarily meet drinking water guidelines, but the assumption that it will after water treatment, is a valid one. PPK Environment fa Infrastructure Pty Ltd Page E5-3

6 Second Sydney Airport Proposal Environmental Impact Statement Supplement 2.2 Impact on Rainwater Tanks Since PAHs would be present in wet and dry deposition, it is likely that they would also be found in rainwater tanks. This would occur both by direct run off to tanks from roofs, as well as wash off of any particulate associated dry deposition. Experience in western NSW with pesticides applied by aerial spraying lead to similar results (Chapman, 1998, personal communication). Using the data quoted above for PAHs in rainfall, the concentrations of dissolved PAHs in rainwater tanks could exceed the drinking water guideline value in urban areas. These however were mainly lower molecular weight molecules. Benzo(a) pyrene concentrations in the Swiss study ranged from undetectable to 2.6 nanograms per litre (Leuenberger et al., 1988) and 0.06 nanograms per litre in the Minneapolis study (Franz and Eisenreich, 1998). Removed from major road traffic sources, these concentrations are likely to be considerably lower. The first flush concentration would be the major carrier of these contaminants, as was found with stormwater (Brockbank et al., 1998). In storm runoff events, however a major factor affecting PAH concentrations appeared to be particulate loads which may vary during a rainfall event depending on storm intensity. First flush diversion options are probably a desirable means of overcoming these issues, otherwise the use of a filter would effectively trap particulate associated PAHs. Natural settling of particulates in the tanks will also effectively remove most of the contaminants from the bulk water. Note that there are other contaminants that need to be avoided in roof runoff, whose health impacts may be even more serious. These issues were covered in Technical Paper No Benzene and Other Volatiles 3.1 Impact on Reservoirs Volatile aerial pollutants considered in the draft EIS included benzene, 1,3 butadiene, formaldehyde, phenol and xylene. Benzene was considered representative of gaseous emissions of xylene, toluene and formaldehyde, and could even be used to model butadiene. Although phenol is included in this group of chemicals, it has a low vapour pressure and could hardly be considered a volatile compound. Phenol would be poorly modelled by benzene. The partitioning of benzene between air and water has been modelled in Technical Paper No. 7 using Henry's Law, based on what was considered a worst case contour from air quality predictive models. The data underpinning this model are not detailed in this report and were not provided. It is assumed that the concentration is Page E5-4 Department of Transport and Regional Services 1

7 Appendix E5 Exhaust and Fuel Emissions in Water Supplies to be based on calculated aircraft emissions during take-off and landing, diluted by known wind dispersion patterns. A limitation of the Henry's Law consideration is that it considers only vapour-water equilibria, and neglects water-particle interactions. Once dissolved in rainwater (or surface water) association of the low molecular weight volatiles with particles may occur, as it does with PAHs. In particular, this interaction is with particulate organic matter, and can be described by an organic carbon-water partition coefficient: Koc = Coc/Cw where Coc is the concentration of chemical in the particulate organic carbon phase and Cw is the concentration in water. For particles having a fraction by weight of organic carbon f ac, the particle-water partition coefficient Kd can be calculated as: Kd = Cs/Cw = oc- f Koc = f K ow where Cs is the concentration of chemical sorbed to natural particles and Kow is the octanol/water partition coefficient. Because the Kow values are low for the low molecular weight volatiles such as benzene ( ) compared to PAHs ( , particle association will not be as significant. The Henry's Law approach could be considered to be conservative, representing a worst possible case with respect to soluble contaminants in rainwater. Particulateassociated contaminants, as already stated, settle in the receiving waters and are readily removed during treatment, so do not represent a threat to human health. The estimation of a wet deposition concentration of benzene, based on Henry's Law, in Technical Paper No. 7, gave a value of 0.07 nanograms per litre for the Badgerys Creek option. The paper incorrectly quotes the drinking water guideline as one gram per litre instead of one microgram per litre. The guideline on raw waters for drinking purposes (ANZECC, 1992) is 10 micrograms per litre. The ecosystem protection guideline is 300 micrograms per litre (ANZECC 1992). The 0.07 nanograms per litre value is the rainwater concentration and does not take into account any dilution in the reservoir. Although all catchment waterways receiving woutd-aet'as additional surfaces for exposure and conduits to the main reservoir, and would need to be considered in any calculation of exposure surfaces, the approach used which considers only input rainfall concentrations is again a conservative one. Formaldehyde, 1,3-butadiene, xylene and phenol are not listed in the drinking water guidelines for ecosystem protection, the water quality guideline for phenol is 50 micrograms per litre. The relative percentage of volatile organic carbon by weight of these compounds in aircraft engine exhaust is 16.6, 1.99, 0.21 and 0.27 respectively, PPK Environment Et Infrastructure Pty Ltd Page E5-5

8 Second Sydney Airport Proposal Environmental Impact Statement Supplement compared to 2.15 percent for benzene. The risk to human health was considered to be greatest for benzene and 1,3-butadiene (Technical Paper No. 6). Henry's Law constants for benzene and butadiene are respectively 0.55 and 7.46 Kilo Pascal per cubic metre per mole (Mackay and Shiu, 1981). This means that for the same atmospheric concentration, there would be 13.5 times more benzene than butadiene partitioning to water, thus justifying the choice of benzene as a model compound. Photochemical degradation pathways exist for butadiene and formaldehyde that would further reduce their concentrations. Note that the Henrys Law constant for benzo(a)pyrene by comparison is 4.2 X 10' 8 Kilo Pascal per cubic metre per mole. The waters and land in the catchment would receive dry as well as wet depositions of contaminants. Dry deposition would include both dry particle deposition and vapour phase deposition. The latter would include equilibrium solubility in the waters. The relative water solubilities of benzene, butadiene and benzopyrene are respectively 1,780, 735 and grams per cubic metre (Mackay and Shiu, 1981). While the formation of enriched surface films of these compounds is likely with the poorly soluble PAHs, it is less likely in the case of benzene and butadiene. Catchment soils would effectively trap most of these compounds, and transport into waterways would be unlikely. Where it does occur, it would most likely be in association with particulates. In either case, this would represent a small input to catchments as distinct from wet deposition, which is effective in scavenging both. 3.2 Impact on Rainwater Tanks As with PAHs, volatiles would be expected to accumulate in rainwater tanks. Since predicted water concentrations of benzene were below drinking water guidelines, it can reasonably be assumed that there would be no threat to human health from benzene or the other volatiles. 4. Conclusions A more detailed review of the physical and chemical behaviour of PAHs, benzene, formaldehyde, 1,3-butadiene, phenol and xylene has been conducted. This has confirmed the predicted absence of threats to either human or aquatic ecosystem health, as a consequence of the deposition in reservoirs and rainwater tanks, following emissions from aircraft engines, should a new airport be constructed in Sydney's west. Page E5-6 Department of Transport and Regional Services

9 Appendix E5 Exhaust and Fuel Emissions in Water Supplies 5. Acknowledgments The author is grateful to Drs John Carras and Peter Nelson, CSIRO Energy Technology for helpful comments. PPK &wit onnt not Cr Infral;ttuctuto Pty Ltd Pane E5-7

10 Second Sydney Airport Proposal Environmental Impact Statement Supplement References ANZECC (1992), Australian Water Quality Guidelines for Fresh and Marine Waters. Brockbank, C.I., Batley, G.E., Ball, J.E. and Tilley, J.H. (1998), Metals and Hydrocarbons in Stormwater Run-Off from Urban Roads, CSIRO Division of Energy Technology Investigation Report No ET/IR118, 115 pages. Franz, T.P. and Eisenreich, S.J. (1998), "Snow Scavenging of Polychlorinated Biphenyls and Polycyclic Aromatic Hydrocarbons in Minnesota", in Environmental Science & Technology, 32: Krahl, J., Siedel, H., Jeberien, H.E., Ruckert, M. and Bahadir, M. (1998), "Pilot Study: PAH Fingerprints of Aircraft Exhaust in Comparison with Diesel Engine Exhaust", in Fresnius' Journal of Analytical Chemistry, 360: Leuenberger, C., Czuczwa, J., Heyerdahl, E. and Giger, W. (1988), "Aliphatic and Polycyclic Aromatic Hydrocarbons in Urban Rain, Snow and Fog", in Atmosphere & Environment, 22: Mackay, D. and Shiu, W.Y. (1981), "A Critical Review of Henry's Law Constants for Chemicals of Environmental Interest", in Journal of Physical and Chemical Reference Data, 10: McVeety, B.D. and Hites, R.A. (1988), "Atmospheric Deposition of Polycyclic Aromatic Hydrocarbons to Water Surfaces: A Mass Balance Approach", in Atmosphere & Environment, 22: Sears, D. R. (1978), Air Pollutant Emission Factors for Military and Civil Aircraft, Office of Air Quality, Planning and Standards, US Environment Protection Agency Report No EPA-450/ ( ). Shabad, L.M. and Smirnov, G.A. (1972), "Aircraft Engines as a Source of Carcinogenic Pollution of the Environment [Benzo(a)pyrene Studies] ", in Atmosphere & Environment, 6: Shabad, L.M. and Smirnov, G.A. (1976), "Aviation and Environmental Benzo(a)pyrene Pollution, in, Environmental Pollution and Carcinogenic Risks", in INSERM Symposia Series, 52: Smith, D.J., Bragg, J. and Wrigley (1991), "Extractable Polycyclic Hydrocarbons in Waters from Rivers in South-Eastern Australia", in Water Research, 25: Page E5-8 Department of Transport and Regional Services