APPLICATION OF MS. EXCEL FOR EVALUATING AIR POLLUTION FROM POINT SOURCES BY GAUSSIAN PLUME MODEL PDF

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APPLICATION OF MS. EXCEL FOR EVALUATING AIR POLLUTION FROM POINT SOURCES BY GAUSSIAN PLUME MODEL Nguyen Tuan Khanh, Dang Tan Hiep Department of Environmental Science, University of Dalat, Dalat, Vietnam Introduction In sheet Plume shape, there are five important Second assumed situation: Gaussian pl...

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APPLICATION OF MS. EXCEL FOR EVALUATING AIR POLLUTION FROM POINT SOURCES BY GAUSSIAN PLUME MODEL Nguyen Tuan Khanh, Dang Tan Hiep Department of Environmental Science, University of Dalat, Dalat, Vietnam Introduction Gaussian plume model is the core of some regularized or commercial models in developed countries and presented in many textbooks. From the didactic standpoint, using professional software packages for practice in air pollution modeling is restricted by following reasons: i) students could not profoundly understand the nature of mathematical equations used in model, ii) financial limit in order to buy these packages, and iii) the course content is not compatible with knowledge and skills required to use packages. The application of EXCEL sheets in teaching air pollution modeling has performed in some universities. This approach is also chosen in our department due to its advantages in cost, practical conditions and pedagogical requirements. Certainly, the accuracy of calculation results is of second importance, because complex effects are neglected. With established Excel sheets, students could gain an understanding of how pollutants disperse in the air under different conditions in meteorology, terrain and stack characteristics.

In sheet Plume shape, there are five important arrays to demonstrate the trajectories of bentover, hot buoyant plumes (Figure 3). The main outputs of this sheet are graphs of plume shape. It can be seen changes of plume shape in different conditions of atmosphere, terrain and stack characteristics.

Second assumed situation: The emissions of five stacks are investigated with following input data: Terrain condition = rural; Atmospheric conditions: Ta = 293 K, uref = 4 m/s, wind blows to the south–west, stability class D. The assumed stacks have characteristics summarised in Table 1. Table 1. Characteristics of five assumed stacks. Stack

Figure 3. Sheet Plume Shape.

The calculation of ground-level concentration of pollutant from each stack is performed in sheets C_stack1 to C_stack5. A cartesian grid with distance increment of 50 m numbered from 5000 m to 5000 m on each axis is used to present the investigated area.

N o1

N o2

a, m b, m

-500 500

vs, m/s ds , m hs , m Ts, K

14 0.6 85 437

12 1.0 135 520

Q, g/s u, m/s H, m

50 7.00 94.0

400 7.92 154.0

N o3

N o4

N o5

-1000 500 -1000 1500 500 -1000 1000 1500 16 0.8 75 573

20 1.2 120 416

15 0.9 95 595

120 300 7.04 7.85 96.2 148.1

200 7.42 118. 4

The sheet C_tot is used to calculatie total ground-level concentration contributed by five stacks at each cartesian grid point.

Aim Application of MS. EXCEL for evaluating air pollution from point sources by Gaussian Plume Model.

Results First assumed situation:

Method The workbook Gaussian Plume Model is of size 750 kB in xlsx format and consists of eight sheets: sheet Parameters used to enter entries in atmospheric conditions, terrain and stack characteristics; sheet Plume Shape used to create a graph of plume shape; sheets C_stack1 to C_stack5 calculate ground-level concentrations of pollutant from five different stacks in an area of size 10 x 10 km; and sheet C_tot calculates total ground-level concentration contributed from five sources at a reception point (Figure 1).

Figures 4a – 4d show how the plume shape and the pattern of pollutant isopleths change dependent on the stability class. These graphs are the results of model calculations for the following conditions: Stack characteristics: cartesian coordinates (-500 m, 500 m), vs = 15 m/s, ds = 1 m, hs = 120 m, Ts = 616 K; Terrain condition = rural; Atmospheric conditions: Ta = 289 K, uref = 3 m/s, wind blows to the north-east and the stability class changes from slightly unstable (C) to moderately stable (F).

Figure 5. The area affected by five stacks emissions in the second assumed situation.

Notes: a, b – cartesian coordinates of stack; vs – stack exit velocity; ds – stack tip diameter; hs – stack height; Ts – plume temperature; uref – wind velocity at the reference height of 10 m; us – wind velocity at stack tip; u – wind velocity along the centerline; Ta – ambient ait temperature; Q – stack emission rate; H – effective stack height.

a)

Conclusion

Figure 1. Structure of the workbook model.

b)

In sheet Parameters, yellow cells are used to enter user’ optional model entries; cells of other colors are used to enter formulas or coefficients Figure 2).

•A simple, effective and useful tool is created to support teaching and learning the introduction course in air pollution modeling. •This workbook model could be used as a qualitative evaluation tool of air pollution from high stacks in industrial zones. Contact: Department of Environmental Science 1 Phu Dong Thien Vuong Str., House A6

c)

Tel: 84 63 3552276 Email: [email protected]

d)

Acknowledgements

Figure 2. Sheet Parameters. Figure 4. Plume shapes and pollution patterns in the situation assumed above with stability class changing from C (4a) to F (4d).

The authors wish to thank unacquainted colleagues in the Institute for Physics and Biophysics of the University of Salzburg (Austria) and the Carolina Environmental Program of the University of North Carolina (USA) because their pioneer research in this field has motivated our work....