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  FORESTRY SYMPOSIUM 1996
WATER QUALITY PARAMETERS OF FOG, RAIN, THROUGHFALL AND STREAM WATER AT HORTON PLAINS

R P R U Rajapaksha*, K A Nandasena*, E R N Gunawardena*
and P T W Rosier**
* University of Peradeniya; ** Institute of Hydrology, Wallingford, UK.

Dying of natural forest in the Horton Plains has been a major concern in recent times. One of the possible causes is atmospheric pollution. Since, fog carries higher amounts of pollutants compared to rain, a study was conducted to assess the different water quality parameters at Horton Plains where fog is very prevalent.

Rain, fog, throughfall and stream water samples were collected and analyzed at weekly intervals from November 1995 to end of April 1996. They were tested for pH, electrical conductivity (EC), Nitrate Nitrogen (NO3 - N), Ammonium Nitrogen (NH4 - N) and Sulfate Sulfur (SO4 - S). Plastic buckets were used to collect rain water and throughfall. A fog collector was designed and constructed to collect cloud water.

The average acidity of rain water and fog was 6.5 and 4.97 respectively. Fog tends to have higher acidity giving a value as low as 3.88, which is 35 times higher than rain. According to literature, this high acid levels could burn the tender leaves. The highest concentration of NO3 -N, NH4 - N, and SO4 -S observed in fog during the experimental period were 10.23 mg/l, 5.04 mg/l and 9.4 mg/l respectively. These values were very much higher compared to what observed in rain water. These pollutant levels with high acidity may, perhaps, provide stress to plants at Horton Plains.

The concentration of chemicals are also high in throughfall. However, soil acts as a buffer and provides good quality water to streams as shown by very low concentrations of chemicals.

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Department of Forestry and Environmental Science,
University of Sri Jayewardenepura,Sri Lanka. 1999. All rights reserved.