ABSTRACT

A half kilometre long transect starting from a Fertilizer Complex taken in 1972, showed that the amount of leaf damage was inversely proportional to the distance from the Complex. Current literature shows that there are distinctive symptoms of air pollution damage on plants.Fumigation experiments carried out in laboratory indicated that the damaged area of leaves was proportional to the concentration of SO2. Compilation of the information gave an idea of using plants for air monitoring.

INTRODUCTION

For a developing country with limited resources, it is necessary to search for cheap and reliable methods of environmental data collection. This paper reports an attempt to map air quality in an industrial city.

Plants are easily affected by industrial air pollutants. SO2,amajor air-pollutant is known to induce characteristic damage symptoms in leaves (Middleton and Darlcy 1966) . Studies on fumigation of plants show that the amount of damage to leaves increases with increasing doses of SO2 (Banerjee and Chaphekar 1978) . A half km long transect starting from a fertilizer complex in Bombay, studied in 1971, shows that the amount of leaf damage is inversely proportional to the distance from, the complex (Chaphekar 1972) . Growth and distribution of lichens have been extensively used for mapping air pollution (De Sloover and Le Blanc 1968) . Higher plants have been used in a few instances (Craker etal. 1974). We chose the latter due to their easy availability.

THE AREA OF STUDY

The warm and humid city of Bombay (72°30'-58' E long, and 18°54'-19°15' N lat.), situated on the west coast of Peninsular India, is the most developed part of India. 5,000 industries, 220,000 vehicles and a human population of 7,600,000 constitute the 437 km2 area, and create and dump 1,000 tons of gaseous pollutants containing 38% CO,31% SO2, 10% NOx, 9% particulates and 8% hydrocarbons in the city air every day (NEERI 1975).

THE WORK

Two types of estimations were carried out :
Trees in the city were used for estimating dust fall for two consecutive; years. Mango, Mangiferaindica 1.. was selected to monitor airborne dust settling by gravity. Well-exposed, horizontally oriented leaves of this, tree, were collected every month from 20 different localities representing clean areas (CI),roadsides with heavy vehicular traffic (R5-HV), roadsides with heavy traffic of small automobiles (RS-LV), roadsides in industrial areas (RS-I) and the vicinity of chemical industries (I-C). The plucked leaves were put in polythene beakers and brought to in laboratory in polythene bags. Dust on each leaf was washed into the same beaker in which it was carried, dried and weighed. Leaf area was noted. The dust-fall was expressed as g/m2 .

Herbaceous plants cultivated under identical conditions of soil and watering, were used for the assessment of air pollutant load, as a whole, in the city. Commelina benghalensis L., a common ruderal species, was grown in plastic pots, from identical-sized cuttings from a local population and transported, after proper establishment,to ten spots selected over the city and representing 'clean' areas,roadsides and industrial areas. Watering was done at these spots by volunteers in comparable, if not in a completely uniform, ways.The plants were collected back after 25 + 2 days exposure to the ambient air at the localities, and analyzed for growth variables,chlorophyll and protein content of shoots.

RESULTS AND DISCUSSIONS

The values of dust-fall are low in September 1976 and high to very high in April 1977. Repetition throughout the next dry period shows that the dust keeps accumulating on leaves after the last showers in October 1977 till April 1978, after which pre-monsoon showers areexpected (Table 1). Within this general pattern, the quantities of dust accumulated at different area reflects the different activities in the vicinity. The 'clean' garden area near the south end of the city.

ACKNOWLEDGEMENTS

The authors thank the University Grants Commission, New Delhi, for financial assistance under the project No. F 23/170/75 (SR II), sanctioned to the senior author. They are grateful to the Director, Professor Haldar, for encouragement and personal interest in work.

REFERENCES

• Banerjee, A . K., 1976. Plants and pollution. M . Sc. thesis, Bombay University, Bombay, India.
• Banerjee, A .K. and Chaphekar, S.B., 1978. Observations of foliar injury to plants by sulphur-dioxide. GE0BI0S, 5: 8-11
• Bell, J.N.B. and Clough, W.S., 1973. Depression of yield in ryegrass exposed to SO2 . Nature, London, 241: 47-9.
• Chaphekar, S.B., 1972. Effects of atmospheric pollutants on plants in Bombay. J. Biol. Sciences, 15: 1-6.
• Craker, L.E., Berubo, J.L. and Frederickson, P.B., 1974. Community monitoring of air pollution with plants. Atmos. Environ., 8 : 845-53.
• Do Sloover, J. and Le Blanc, F., 1968. Mapping of atmospheric
• Pollution on the basis of lichen sensitivity. Proc. Symp. Hoc. Adv. Trop. Ecol. , Varanasi, 42-56.
• Middleton, J.T. and Darley, E .F., 1966. Plant damage - An indicator of the presence and distribution of air pollution. Bull. Org, mond. Sante/Bull. Wld. Hlth., Org., 34 : 377-80
• NEERI, 1975. Air Pollution Survey of Greater Bombay. A Report.