This special issue of Clean Air is devoted to the majority (35 of 40) of the papers presented at the Latrobe Valley AirShed Study's two-day scientific summit. Alec Smith, Air Quality Branch Manager at the SA Department of Environment and Planning.
LATROBE VALLEY AIRSHED STUDY SYMPOSIUM PROCEEDINGS PAPERS
AN OVERVIEW OF THE LATROBE VALLEY AIRSHED STUDY
B. Tucker
- INTRODUCTION
- HISTORY
- ACHIEVEMENTS
- CONCLUSION
The coincidence of the change in focus and the change in the presidency was fortuitous. Details of the scenario, jointly developed by SECV and EPAV, are based on the recent N R E C study on electricity generation in Victoria and on discussions with industry in the Valley.
METEOROLOGY AND AIR QUALITY OF THE LATROBE VALLEY
1% of the time (this is around 9 hours per year - the interpretation of 'three days' used by modellers to compare with the SEPP targets). Values of 132 and 91 ppb SO2 were recently measured at Mt Tassie in the middle of the night due to the Loy Yang power station.
DATA PROCESSING AND
The observed acidity levels are not particularly high by world standards and are up to a quarter of the levels found in the eastern United States. Furthermore, there is an indication that a related problem of acid deposition occurs in the Latrobe Valley: it warrants investigation.
COMMUNICATIONS IN THE SECV AND EPAV MONITORING
Almost no acidification has been detected in areas outside the Latrobe Valley, and the acid in the Latrobe Valley rain is thought to come from local sources. The effect of clouds on hills, while reasonably well understood and considered in the past, seems to be re-emerging as a problem.
NETWORKS
The Melbourne Airshed Study (MAS) was initiated in 1979 to evaluate the effect of the SECV Newport D power plant. Changes to the data logging and reporting system are hampered by the capabilities of LVAMN's central computer.
LOCAL AIR MASS STRUCTURES AND CIRCULATIONS ON EXTREME
DAYS IN THE LATROBE VALLEY David Jones and Gregory Hall
The above points suggest the potential inadequacy of pollutant distribution models that use a constant average wind speed and direction with an allowed degree of variability around that average. A model using a three-dimensional time-varying wind field appears to be a minimum requirement to adequately model pollutant distribution in the Latrobe Valley airshed.
DIAGNOSTIC WIND FIELD MODEL STUDIES
- MODEL DESCRIPTION The model generates a 3D wind field
- RESULTS OF THE VALIDA- TION PROGRAM
- RECENT RESULTS FROM THE CONTINUING VALIDA-
- CONCLUSIONS
- MIXING HBGHTS AND STABIUTY 1 Daytime Mixing Height Model
- Pasquill Stability
- STATISTICAL DISTRIBUTION OF MIXING DEPTH AND STABILITY
The large decrease is associated with the transition to the upper air data which appear to be poorly correlated between 100 and 500 m. On the other hand, the upper air observations do not seem to be sufficient at heights between 100 and about 500 m.
A METEOROLOGICAL DATA FILE FOR USE WITH THE ISCST MODEL
Delaney and B. van Meurs
The file also contains derived data such as hourly mixing depth calculated from the morning radiosonde flight at Minniedale Road using the method of Driedonks (1982), and Pasquill stabilities determined from the Monin-Obuchov length L using the method of Golder (1972). The daytime mixing heights in the file were calculated using the method of Driedonks (1982), where the mixing height h at time t + d t is given by.
POLLUTION SOLUTIONS
SOLVENT RECOVERY -
During the morning, warming of the land results in convective mixing, at the surface, of these westerly winds. This warming of the land also results in the production of sea breezes and updrafts.
THE SUMMERTIME WIND REGIME OF THE LATROBE VALLEY
Also evident in Figure 2(a) are the light westerly winds ahead of the sea breeze. These westerly winds also delay the onset of the east coast sea breeze on the second day.
PARTICLE DISPERSION BY SEA BREEZES SN THE LATROBE
The Colorado State University Mesoscale Model (Mahrer and Pielke, 1977; . McNider and Pielke, 1981) was used to model the wind regime in the Latrobe Valley. On the second day, these westerlies are convectively mixed to the surface in the western part of the.
VALLEY
Particles also collect in the leading edge of the east coast sea breeze, as illustrated more clearly in Figs. However, the distance of the inland source (Morwell) from the coast is such that the near surface layers of the atmosphere have become stable by the time the sea breeze reaches that location (late afternoon).
DISPERSION COEFFICIENTS FOR THE PLUMES FROM THE LATROBE
The difference between the lines of best fit obtained at Mount Isa and Loy Yang is due to the difference in the buoyancy of the two plumes. The effect of cloud buoyancy on cloud growth W2(e) can be seen by scaling the value of Wz(i) with the buoyancy length scale in a manner similar to that used for Wy(e).
PLUME RISE IN THE LATROBE VALLEY Peter Manins, John Carras
RESULTS
This performance is much better than the error in determining plume height from the aircraft data and may therefore be due to chance. Final rise height is taken as the height of the plume center line at distances less than 10 km from the stack.
CONCLUSIONS
The horizontal lines show where the plume was cut by the aircraft at the indicated distances and the dashed line is an interpretation of the plume adjustment. The constraints on wind speed simply ensure that either it is windy enough for neutrai conditions to apply or that a lower rise height than obtained with the stable formula is predicted to be conservative.
MODELLING MESOSCALE EFFECTS IN THE LATROBE VALLEY WITH A
NESTED MODEL
The arrival of the sea breeze in the Latrobe Valley is in good agreement with the observations presented by Abbs and Physick (1988). The superimposed case shows a weakening of the flow while the non-superimposed case shows a cyclonic bend of the flow in this region.
SUMMARY
These effects are evident in the 1600 EST day 2 wind fields (Figs. 2c and 3c), as a difference in the inland penetration of the east coast sea breeze. At three sites in Melbourne, samples were also taken during the evening hours of the day preceding the event days: see Fig. A second set of samples was taken at Trafalgar North, Darnum North and Yannathan during the afternoon hours of the event day.
ATMOSPHERIC FLUOROCARBONS AS INDICATORS OF AIR MOVEMENTS
During the summer of 1988, these tracers were used in a study of the roles of air transport from Melbourne and Latrobe Valley air recirculation for high ozone events in the Valley. During the afternoon and evening hours of the day concentrations remain fairly constant, but begin to increase during the early morning hours as the nocturnal surface inversion is first eliminated (Fraser et al. 1977 showed this) or fluorocarbon-rich air passes. . During the hours characterized by low concentration, the values varied in an interval up to twice the minimum value for Fl 1 and F12, while during the period of high concentrations, the values varied over a factor of up to 6 for F l l and 3 for F12.
INTO AND WITHIN THE LATROBE VALLEY
The available data from the Latrobe Valley were grouped based on the available information on the source of the measured air mass. Dilution of Melbourne air during passage into the Latrobe Valley occurs through lateral mixing and growth of the planetary boundary layer in the morning. Camberwell, which is close to the route and has a sample available approximately 40 minutes before the route time, gives a dilution of 3.4 to 6.2.
AIRCRAFT STUDIES IN THE MELBOURNE AND LATROBE
Dilution factors represent limitations on the dilution of ozone-forming precursors, nitrogen oxides (NOx) and non-methane hydrocarbons (NMHCs) that can be transported from Melbourne to the Valley. Further investigation into the sources and levels of the two fluorocarbons within urban centers in the Valley is needed to optimize the utility of these fluorocarbons as air tracers at the Latrobe Valley Airport.
VALLEY REGIONS
Flight path altitudes are given in the legend, while point times and 03 and NOx concentrations are indicated. In the early afternoon of March 25th, the top of the mixed layer was at 3500' north of Berwick and 3000' east of Traralgon. Very high concentrations of oxidants were observed near Bacchus Marsh and Melton, about 40 km WNW of central Melbourne, with a strong odor and eye irritation.
SOURCES OF POLLUTANTS IMPORTANT TO THE LATROBE
Based on the measured data, it is clear that areas around Melbourne may be exposed to greater photochemical impacts. Other point sources include smaller industrial sources as well as larger commercial premises. The source numbers were already well known to the industries, but it was necessary to actually count the number of commercial and domestic premises in the region and arrange them into the appropriate grid squares.
VALLEY AIRSHED
INTRODUCTION - THE NEED TO DETERMINE SOURCES
Major point sources are those that discharge from a height of 50 meters or more, or have a floating plume (blowing flux > . 50 m4 s"3). Area sources include domestic and smaller commercial premises, motor vehicles , biogenic sources and Diffuse dust sources. Vehicle movement numbers are obtained from a combination of visual traffic counts, time-lapse photography and traffic counter data from the Road Traffic Authority and local councils.
THE AIR EMISSIONS INVENTORY Much of the above need has been
Delaney (1987) conducted a sensitivity study of the Deardorff and Willis (1982) model and applied it to a case study of fumigation of the Hazelwood plume at Minniedale Road. On the other hand, the model is extremely sensitive to the wind direction at plume height because the plume spreads little in the stable air before atomization and is therefore very narrow. After considerable development work, it now appears that these models are capable of quantitative prediction of the structure and movement of phenomena such as the sea breeze.
ANNUAL STATISTICS
His study shows that the model is only moderately sensitive to (no more than linearly dependent on) parameters such as wind speed, mixed layer depth (ie, plume height), and mixed layer growth rate. IRT from Melbourne in PBL by NW wind shift to SW associated with passage of a trough. 03 in Melbourne caused by recirculation of emissions from central, western and bayside suburbs in local bay breezes.
IRT from Melbourne in PBL by NW wind shift SW associated with passage of trough. Reductions in visibility were negligible except when the plume was transported in stable air.
CONCLUSION
The worst results from Loy Yang Power Station with a response rate of 3%t1 caused a 2.9% reduction in visual range at 12 km downwind, with greater reductions further downwind if conditions persisted. These results reproduce observations of elevated layers of haze and negligible power plant impact at ground level. The relatively high in-plume S 02 oxidation rate of 3%h~1 suggests the potential for significant levels of sulfate aerosol to build up in elevated layers if wind reversals recirculate polluted air over the valley.
FINE PARTICLE MASS EMISSIONS
After applying the reduction factors in Table 1 to the emission inventory, the relative sizes of the model inputs for night and day can be seen in Figure 1. This diagram shows the evolution of the mixed layer height with time as well as the final plume height for various main point source emitters. There were 12 elevated point sources, with power stations accounting for the bulk of the emissions; surface emissions were.
MODELLING OF LVD FREQUENCY DISTRIBUTIONS
The particulate emissions from the 1984 emission inventory are scaled with the reduction factors shown in Table 1. It is clear that the predicted contribution of the point sources to the LVDs measured at the measuring stations is minimal. Running the model only for elevated point sources yielded no exceedances of the 20 km limit for any monitoring station: in fact, the predicted worst-case LVDs (Table 3) are significantly better than this.
