Transactions on Ecology and the Environment vol 4, 1994 WIT Press, ISSN

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1 Irnmission and dry deposition of the trace gases Og and SO^ downwind of a main industrial region in Eastern Germany G. Spindler, W. Rolle, D. Theiss Institut Troposphdrenforschung e. V., Permoserstr. 15, D Leipzig, Germany ABSTRACT In this paper we present a short description of the measuring station near by the small village of Melpitz. Results of continuous measurement of the immission of SO^ Og, NO2 and NO and some results of the calculation of deposition velocities and fluxes for SC>2 and Og by the gradient technique are shown. The deposition velocities vary in the range from 0.03 to 0.16 cms"^ for SC>2 and 0.19 to 0.28 cms"^ for Og by night and in the range from 0.19 to 0.31 for SC>2 and 0.24 to 0.42 for Og. in the daytime Deposition velocities and fluxes are influenced by daytime and by the state of vegetation noticeable. INTRODUCTION In 1991 the integrated research project SANA (scientific observations program for the rehabilitation of the atmosphere above the new countries of Germany) has been established to study the changing air pollution after the German unification in East Germany [1,2]. One scientific topic of the research project SANA is the registration of the change of emission and the effect on the immission and deposition. The new social facts and the new economical conditions after the political union of East and West Germany produce chances for a new efficient industrial structure and for the change from brown coal combustion to the application of other less environmental polluting power supply. The expected result of changing in the air pollution in the future are the drop of SO2-emission and a simultaneous increase of the emission from NO and NO2 by increasing motor vehicle number. Figure 1 shows the regions with the most expensive SO2-emission and the location of the measurement place at Melpitz in the country of Saxonia.

2 294 Pollution Control and Monitoring N A Measurement Place Melpitz SAXONIA Region with the Highest SO2-Emission in Germany Distance Leipzig to Melpitz 41 km Figure 1: Location of the measurement place near Melpitz The position of Melpitz is likewise a measurement site of the immission network from UBA (Umweltbundesamt) and from the SANA wet deposition network. For additional comparisons an equipment exists for the registration of inferential method parameters on the same site[3,4,5]. EXPERIMENTAL The measurement station is placed in an old large meadow which is very good suitable for micrometeorology experiments. This station is equipped to measure the dry deposition of SO2, Og, NO, and NO^ The compass card of the wind direction for Melpitz is shown in Figure 5. The gradient method is based on measurements of meteorological parameters such as wind velocity, temperature and relative humidity in different heights. The experimental realisation of the measurement of profiles for the concentration of trace gases in Melpitz in different heights is shown in Figure 2. The air streams in a continuous flow from 8 heights through black Teflon tubes. The maximum height is 12 m, all tubes are 22 m long, the inside diameter is 7,5 mm. The air stream is approximately 500 l/h, the resulting transport time from the inlet equiped with a quartz filter to the analyser is 4-5 s. Profile measurement is realised as a multiplexed system

3 Pollution Control and Monitoring 295 with 3 gas multiplexers for the different analysers. Meteorological parameters are measured at an other tower quite near to the tower of air sampling. The measurement heights in both cases are the same. The meteorological parameters are continuously registrated as 10 s averages. 0,50/1, 43/3, 59/7,89/zero air 0,89/2,42/5,32/1 1,69/zero air every hour 6 profits per hour rotameter air pump Figure 2: Gradient system for chemical species The profiles are calculated from hourly mean values by logarithmic fits of the profiles from concentration (c^) and wind speed (u^). The displacement height (d) is calculated as monthly mean by iterations of hourly mean values of the wind profile by near neutral conditions (0,03>Rj>-0.03; Ri-RICHARDSON-number) [6,7] (1-3). -->!-!>"<' «' >-', with stable conditions unstable conditions c = dc (2) u = du = JL^ x» dz z - d (3)

4 296 Pollution Control and Monitoring The quantity of the RICHARDSON-number (Rj) is a criterion for the following calculations with the functions of stability. These are different for varying of the stability of the boundary layer (4). gdt/ * /dz RICHARDSON-number (4) R > 0 unstable conditions R, < 0 stable conditions It is possible to get results by the gradient method with a gas multiplexer system for 30 to 50 % of the measurement time. In this case hourly mean values are calculated. The results are limited by fast changes in the immission concentration, by different stability in the profile distance, by wetness in the tubes and by other technical problems. The deposition velocities (vy) are not calculated if the wind is directed from the village of Melpitz (Figure 5). -Q Z Daytime [h] ii Figure 3: Temporal distribution of daily maximum RESULTS In Figure 4 the immission situation from Mai 1992 to March 1994 is demonstrated. The SO2 immission decreased from winter 92/93 to winter 93/94 caused by closure of power plants in the mean wind direction. U. Ratzlaff, K. Muller and E. Bruggemann [8] measured a decreasing of Ca^* from coal combustion and calcium carbide production in the aerosols (PM 10) at the same time. The ozone immission and those of the nitrogen oxides NC>2 and NO show no extrem change. For ozone the measured

5 Pollution Control and Monitoring 297 values are clearly higher in August 92 and May 93. The reason in both cases is a meteorological situation with large sunny periods. A histogram illustrates the temporal distribution of daily immission maximum for ozone and sulphur dioxide for the entire time of measuring (Figure 4). The immission maximum for sulphur dioxide is typical in the later morning, with the reason of more turbulence at a transport of the trace gas SO2 from higher layers to the ground. The ozone immission maximum is in the afternoon, because ozone is a secondary product of photochemical reactions and it is also limited by sunshine. The secondary maximum near midnight is a vertical or horizontal transport phenomenon. Table 1 shows the calculated deposition velocities [vy] for four different months. The deposition velocity is influenced by the state of the vegetation and their wetness. In both September we find low deposition velocities for sulphur dioxide over cutted grass. For ozone the variation of v^ is not as big as for sulphur dioxide. The deposition velocities differ for night and day because the turbulence in the boundary layer as an important factor for the transport is very different. The flux [FJ is important for the impact in to the ecosystem [9]. For SC>2 the impact decreases dramatically. It is caused by a decreasing immission. For ozone the situation is comparably in all months. SUMMARY It was shown, * that the sulphur dioxide concentration in Saxonia is decreasing, that it is possible to calculate deposition velocities for trace gases over a longer time by gradient technique with a completeness from 30 to 50% of the measured hourly mean values, that the dry impact of sulphur over the grassland near Torgau is decreasing. This location is the upwind side of the Leipzig city area. ACKNOWLEDGEMENTS We wish to thank the Bundesminister fur Forschung und Technologie for supporting the research project SANA (P12/103551). We are also greatly indebted to N. Beier from the University of Munich and F.Meixner from the Fraunhoferinstitut fur Atmospha'rische Umweltforschung, Garmisch-Partenkirchen for scientific discussions in front of the construction of the measurement station and technical supporting.

6 298 Pollution Control and Monitoring REFERENCES 1. Dlugi, R., Foken, Th., Kramm, G., Nestlen, M., and Spindler, G. ' Wissenschaftliches Programm zur Bestimmung der Deposition im Rahmen des Verbundprojektes SANA', Fraunhofer Institut for Atmosph rische Umweltforschung (IFU), Garmisch-Partenkirchen, Verbundforschungsvorhaben SANA 'Wissenschaftliches Begleitprogramm zur Sanierung der Atmosphare uner den neuen Bundeslandern' Konzept, Garmisch-Partenkirchen Hicks, B.B., Baldocchi, D.D., Meyers, T.P., Hosker, Jr., R.P., and Matt, D.R. 'A preliminary multiple resitance routine for deriving dry deposition velocities from mesured quantities', Water, Air, and Soil Pollution Vol. 36, pp Muller, H. personal communication Hicks, B.B., Hosker, R.P., Meyers, T.P., and Womack, J.D. 'Dry deposition inferential measurement techniques -1. Design and tests of a prototype meteorological and chemical system for determining dry deposition' Atmos. Environ. Vol. 25A, pp Giisten, H. 'Messung der trockenen Deposition von Spurengasen mit mikrometeorologischen Methoden' Proceedings Tagung der Arteitsgemeinschaft der GroRforschungseinrichtungen (AGF) Bonn-Bad Godesberg 1989, pp Stull, R. B. (Ed). An Introduction to Boundary Layer Meteorology Kluwer Academic Publishers, Dordrecht, Boston, London, Ratzlaff, U.,Muller, K., and Bruggemann, E.' Comparing Investigation of Aerosols and Wet Deposition Sampler from Leipzig and the Rural Measurement Station Melpitz', in this proceedings 9. Spindler, G., and Rolle, W. 'Aufbau von Begasungskammern fur kleinere Forstpflanzen - Ermittlung von Ozondepositionsraten' UWSF - Z Umweltchem. Qkotox. Vol. 5, pp , 1993

7 running 10 day averages (centred) H & 30 o a 25 O) n o CL 0 Figure: Immission of trace gases in Melpitz (May 1992 to March 1994) O o 2_ 5' OQ

8 300 Pollution Control and Monitoring Table: 1 Examples for deposition velocities and fluxes calculated with gradient technique (monthly mean values) daytime [h] Sep. 92 SO2 O3 Apr. 93 S02 03 June 93 S02 C)3 Sep. 93 SO , monthly mean value Deposition Velo ci tyv; j [cm/s] availability of hourly mean values [%] , monthly mean value monthly impact [kgha~'month~1] (S) 1.19 Flux FC; [ugm (03) (?3) ($) (03) 1.90 Sector without deposition calculation (10 ) Figure: 5 compass card of the wind direction for Melpitz (May 1992 to March 1993), calm is for 4,3% of the measuring time (Uz<0.5ms"\ z=11,7m)