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ACID RAIN AND DANUBE WATER MONITORING PROJECTS

IN HUNGARIAN SCHOOLS

I. Hobinka Fazekas Grammar School, Budapest, Hungary

M. Riedel Eötvös University, Budapest, Hungary

1. Introduction and goal

It is important to spread an environmentally conscious culture among young people, since students taking an active part in investigations of the environment can be expected to become active members of the society aiming to protect the environment. They will also get accustomed to basing opinion on facts resulting from experiments, which - with some limitations - they themselves will be able to measure as well. Thereby they will be able to differentiate between true, false or even distorted information.

2. Acid rain monitoring network

The chemical pollution of the environment has a wide variety of origins, such as sewage, fertilization, fuel burning, heavy metal wastes, etc. Acid rain is one of the serious environmental problems all over the word. The expression "acid rain" is, however, not new: R. A. Smith used it for the first time in 1872. The increasing acid content of rain water leads to the acidification of surface waters, to the increase of metal ion concentration, to the destruction of living creatures, like damage of forests, to the increased corrosion of buildings, statues, etc. For examples one-third of the Black Forest in Central Europe was damaged, and the corrosion damage in Hungary is estimated to tens of millions US Dollars.

The acid content of rain water can be attributed chiefly to the burning of fossil fuels which create carbon dioxide (CO2) and as by-products sulfur dioxide (SO2) and nitrogen oxides (NOx). These are converted by oxidation and by reactions with water into carbonic acid, sulfuric acid and nitric acid, in which form they appear in rain water. They are the results of complicated chain reactions. In the oxidation process ozone (O3) and the free OH. radical play an essential role. The degree of rain acidity is characterized by the pH value. It is known that the pH of pure water which is in equilibrium with the carbon dioxide content of the air (0.03%, p(CO2) = 30.4 Pa) is 5.6 due to the equilibrium:

CO2 + H2O H2CO3 H+ + HCO3-

The water in an open flask contains about 25 times more acid than the pure H2O. This value should be regarded as the neutral point of the rain, so acid rain has a pH<5.6.

Coal and oil consumption is growing fast world-wide, and therefore the amount of CO2 in the atmosphere is growing continuously. Generally, the concentration of SO2 has appeared constant during the last two decades because of the applied sulfur binding methods in the developed countries, but the amount of NOx shows a continuous rise. The production of these substances in the world is not equal. In heavily industrialized countries the acid pollution is especially high and in large cities rain water may reach a pH of 3.0-3.5. These endangered areas take about 5% of the Earth. In the decade from 1980 to 1990 the total SO2 output decreased by 23%, the total NOx output increased by 7%. Comparing it with the statistics of 1950, it will be clear, that the total output increased by 5 times. In 1980 the 2.9%, in 1990 the 2.6% of the total European sulfur output comes from Hungary, because of the use of domestic coals of high sulfur content. The same statistics for nitrogen shows 1.2% and 1.1%, respectively [1-4].

The acidity of rainfall is an environmental parameter, which can be examined satisfactorily and regularly even at the schools' level. Since schools can be found everywhere, possibly even in very polluted areas, statistical analysis of data arriving from many schools could provide valuable information to detect local anomalies. Such environmental investigations have already been run in several countries, e.g. in Germany, France, Great-Britain, USA, Japan, Norway, Malaysia. We established in Hungary an acid rain examining network of schools called "SEMI" in 1990 [5]. Students and teachers of some 80 schools from almost every part of Hungary take part its work.

The measurement of the pH of rain water of low buffer capacitance involves many difficulties [6,7]. The measurement with glass electrode is precise enough in case if suitable calibration, but the implementation requires high skills, and the needed equipment is not cheap either. For investigations in schools the color indicators in form of commercially available (e.g. Merck) "non bleeding indicator strips" proved to be most suitable [5]. In this product the indicator dye is bound to the paper with covalent bonding. After washing out one can use the strips several times. It is cheap, easy to use, with a precision of about 0.2-0.5 pH unit. The setting in of the stable equilibrium color needs 1/2 - 2 hours because of the low ion concentration.

In course of the work of the SEMI project much interesting data have built up concerning the local and time distribution of acid rain in our country. From the data provided by schools one can see that in the period 1990 - 1994 in the country different kinds of rainfall had been observed between pH 3.0 and 7.5 with a significant dispersion of time and areas. The average for whole Hungary is about pH = 4.6, which could even be pH = 3.8 without the neutralizing effect of the dust of limy soils. This is almost identical with the data of the official observations between 1978 and 1982 [2]. There are, however, big local differences caused by the local pollution and neutralizing effects. In Budapest we examined about 300 rain samples so far, according which the capital of Hungary is a much polluted area with average of pH = 4.2. In the 100 km radius around Budapest in the small settlements the average is about pH = 5.6. So, the rain in Hungary has in average one magnitude higher acid content than the neutral rain, but our country is still considered as a medium-polluted area in Europe. The total quantity of acids in the form of rain and dry precipitation is equivalent of 0.2 mol H+ annually per m2 that is equivalent of about 10 cm3 concentrated H2SO4.

3. Blue Danube chemical status monitoring

We joined the UNESCO supported project "Blue Danube" in 1992. One of its goals is to monitor the chemical quality along the whole Danube. From the most important 8 chemical parameters which determine the quality of the natural river waters the Chemical Index (CI) is calculated by the formula

CI =

where Pi is a dimensionless quantity proportional to the measured chemical parameter and Ei is a weighing number expressing the influence of the given parameter on the total quality of the water [8, 9]. The CI is an average which expresses the over all quality of the water, and ranges 1 - 100, i.e. from dead to healthy, clean water.

We applied simple commercially available rapid chemical tests (e.g. Merck, Riedel de Haën, Macherey and Nagel, Analaqua, Radelkis, etc.) for the in situ measurements of the different parameters [10]. All the methods are environmentally harmless. Oxygen concentration and 5 days biological oxygen consumption of the water were measured by means of a portable instrument with plastic membrane electrode. Simultaneous measurement was made by the traditional Winkler method, too. Accuracy of reading was: ± 2 %, which corresponds to ± 0,1 mg/dm3. Temperature was measured on the site with 0,1 oC scaled thermometer. NH4+-, NO3-- and PO43--ions were measured with rapid colorimetric method. The accuracy of reading was logarithmically depending on the measured range, typically ± 10 %. pH was measured with a portable pH-meter with glass electrode. Accuracy of reading: 0,01 pH. Conductance was measured with portable digital instrument connected to an electrochemical conductance measuring cell. Accuracy of reading: ± 1 S/cm.

The sampling of water was done at the Petõfi Bridge in Budapest once every week. In the measured period the CI was between 55 and 75 in Budapest, so the water qualification was second classed, that is, moderately polluted. We calculated the CI also from the data of the literature [11] measured in the 1970's resulting CI=71(65). The comparison shows that the water quality has not changed dramatically in the past decades. The short-time changes of the CI in the tested period show however, some slight fluctuations (e.g. maximum at the end of July, minimum in the beginning of June and in the end of August).

To follow the fate of one particular water volume of the Danube when passing the Hungarian territory we organized 3 expeditions during spring and summer of 1994 from Komárom to Mohács, along about 300 km. The speed of the Danube water is 7 km/h on the upper section (between 1800 and 1600 river km) and 6 km/h in the lover section (1600-1400 river km), consequently the flowing along lasts 2 and a half days. The staff of the expeditions were transported by motor boats, cars and railway. We take samples in every 15 km in the middle of the river. The samples were analyzed directly after taking it out from the river on the deck of the boat or at the shore. The 15 km distance and the speed of the water determined the about 2 hours' frequency of the sampling. During the day it caused a very stepped up work, since the complete series of measurements of the 8 parameters even with parallels needed about more than one hour. During the night some measurement points left out, because the colorimertic method needs daylight. After sunrise the motorboat of the expedition reached the traced water mass. Entering the upper area of higher water speed the CI = 75, at Budapest it falls to 50, then it is constant with small fluctuations in the industrial area (60), at the national park of Gemenc it is again 70, coming into again to urban territories it drops to 60. Its quality remains in the slightly polluted class.

4. Mátraderecske waters studied by the workshop of the conference

The participants of the workshop of the Rio Followup Conference made measurements of some chemical parameters of the natural waters sampled during the Mátraderecske excursion. The results are summarized in the table.
origin of waterproperty valueremark
brook crossing the villageNO2- concentration 0.3 mglhigh
O2 concentration 6.7 mgl
pH7,0
CO2 containing well of an old woman NO3-concentration 25-50 mglhigh
O2 concentration 0.4 mglvery low
pH7,0
total hardnessover 40 very high


5. General remark and conclusion

The most important consequence of the 5 years' student research projects SEMI and Blue Danube is that the scientific and the emotional influence of this work on our students was significant. Even the chemistry teachers of our retraining courses accept and follow this activity.


The projects were supported by the Pro Renovanda Cultura Hungariae Foundation, the Town Council of Budapest and the Ministry of Environment and Planning.

References

1. I. Pais, L. Horváth: in "Acidic Precpitation" Vol. 5., Ed. by A. H. M. Bresser and W. Salomons, Springer Vlg., New York, Berlin, Heidelberg p. 193

2. L. Horváth, E. Mészáros: Atmospheric Environment 18 (1984) 1843

3. Acid News 4/91

4. Air Pollution Project Europe, Norges Naturvernforbund, Norway, 1992

5. I. Hobinka, M. Riedel, B. Javorszky: Int. Conf. on Energy Alternatives/Risk Education, Vol. I., Ed. by G. Marx, National Centre for Educ. Technol., Veszprém, 1989., p. 199.

6. A. K. Covington, P. D. Whalley, W. Davisson: Pure Appl. Chem. 57 (1985) 877

7. W. Davison: Trends in Anal. Chem. 9 (1990) 80

8. E. Bach: DGM 24 (1980) 102

9. I. Pongratz, B. Ruf: Chemischer Index und Gewässergüte, Vlg. Dr Flad, Stuttgart, 1991.

10. Merckoquant-Tests, E. Merck, Darmstadt, Germany

11. Benedek P. et al.: Hidrológiai Közlöny, 1976, No 2., 50