Fighting against POLLUTION to Save Environment
Fighting against POLLUTION to Save Environment
Proc. Int. Conference on Environment Planning & Management, University of Roorkee (India),
April 5-7, 1990, pp. 204 – 210.
D.B. Boralkar, S.K. Tyagi** and B. Sengupta
West Zone Office,Central Pollution Control Board 46-B, Gautamnager, VADODARA,390 OO7,India
**Central Pollution Control Board, "Parivesh Bhavan" East Arjun Nagar, DELHI, 110 032, India
In metropolitan areas petrol driven vehicles are recognised today as the major source of lead pollution. In view of the rise in the number of vehicles on road as well as the Octane value of petrol from "83" to "87" there is logical possibility of increased lead emission from petrol driven vehicles. Central Pollution Control Board carried out systematic studies over a period of January 1984 to April 1987 in the city of Delhi in order to reassure ourselves with regard to lead contamination of the roadside ecosystem and search of the plant species that help mitigate roadside autoexhaust lead pollution. The present paper deals with the studies carried out during August 1985 to April 1987 which revealed increase of atmospheric lead concentration, increase of lead in the soil and accumulation of lead in the plant species "posted" at five specifically chosen traffic intersections. Alstonia scholaris, Eugenia jambolana and Polyalthia longifolia were found quite useful for roadside plantation and thereby help in mitigation of lead pollution.
Autoexhaust, Lead Pollution, Ecosystem, Roadside Ecosystem.
Lead in the form of alkyl lead compounds is added to improve the antiknock quality of motor spirit and most of it leaves the engine through exhaust pipe as particles of lead salts. The amount of lead in Indian gasoline varies from 0.06 to 0.44 gm per liter of motor spirit. In view of the substantial rise in the number of vehicles and also octane value of petrol from "83" to "87" there is logical possibility of increased lead emission from petrol driven vehicles. In the wake of promulgation of pollution control laws, automobile exhaust pollution and its adverse effect on the environment drew more attention of scientists as well as technologists all over (Smith,1976; Bayliss,1983; Mathur et al.,1985; C.P.C.B.,1985; Luhar and Patil,1986; Bhatnagar,1988 and many more).
Central Pollution Control Board (Ministry of Environment, Govt. of India) carried out systematic studies over a period of January,1984 to April,1987 in the city of Delhi in order to reassure ourselves with regard to lead contamination of the roadside ecosystem and search for the plant species that help to mitigate roadside autoexhaust lead pollution. The present paper deals with the studies carried out during August,1985 to April,1987.
Ambient air quality monitoring for lead (APHA,1977) at selected five traffic intersections (namely Delhi Gate, India Gate, Red-Fort, Ashram and Azadpur) and at control site i.e. the Nursery of National Physical Laboratory (NPL), was done once-a-month in 1985 and generally once in two months in 1986 and 1987, so as to have total fifteen observations. Plant species earlier grown properly in the nursery were installed at all the six sites and harvested once in three months for their growth performance study as below.
| Sr.No. | Plant species | Date of installation | Date of Harvest |
|---|---|---|---|
| 1 | Alstonia scholaris | Feb., '86 | May and Sept.,'86 |
| 2 | Eugenia jambolana | Feb., '86 | May and Sept.,'86 |
| 3 | Polyalthia longifolia | a) Feb., '86 b) Sept., '86 |
May and Sept.,'86 Dec.,'86 and Apr.,'87 |
| 4 | Populus deltoida | Sept., '86 | Dec.,'86 and Apr.,'87 |
| 5 | Putranjiva roxburghi | Sept., '86 | Dec.,'86 and Apr.,'87 |
The parameters studied included lead in soil (Jackson,1958), lead in foliage (washed, acid digested and then scrutinised on A.A.S), total leaf area in sq.meter per plant using area-meter and total biomass in gm. per plant (Mishra,1968).
The results of ambient air quality in regard to lead measured during the study period are presented in Table 1. Comparison of individual results of airborne lead concentrations at various traffic intersections and control location revealed correlation between lead in air and traffic volume. This indicates that automobile exhaust emission is the prominent source of airborne lead in the city of Delhi. It is seen from the results that the levels of lead in ambient air at traffic intersections were higher in winter and monsoon season as compared with that of summer season. A sharp increase in the lead concentration in ambient air at all the five traffic intersections was observed during the present study period of August,1985 to April,1987 as compared with that of the period from January,1984 to June,1985 (C.P.C.B., 1985) as below.
| Sr. No. | Period | Lead, ng/cu.m, (10-h average, once-a-month) |
|---|---|---|
| 1 | January,1984 to June,1985 | 185 (India Gate) to 324 (Red Fort) |
| 2 | August, 1985 to April, 1987 | 199 (India Gate) to 459 (Red Fort) |
The base data (Table 2) show that lead in the soil increased in Sept., 86, when compared with that of May, '86 / Dec.,'86 and Apr., '87 in all the pots of all plant species at all locations. The contamination of soil in the pots is thus evident due to sedimentation of atmospheric emission of autoexhaust lead as well as decomposition of lead-contaminated leaf litter fall. This may adversely affect the useful biological activities in soil (Smith, 1976).
Lead in Plants: Lead content of plants from different locations in May,1986; September,1986; December,1986 and April,1987 are presented in Table 3, indicating higher lead in plants from traffic intersections as compared with that of plants from control location. The response of plant species to lead accumulation varied, however, it was not found related to traffic density.
Plant Growth: Generally there was reduction in total leaf area and biomass production of the plant species at different traffic intersections as compared with that of N.P.L. Nursery (Table 4). Growth performance of Polyalthia (Ashok), Eugenia (Jamun) and Alstonia plant species was generally better than the other plant species studied.
Assessment of Impact: Plant species that would accumulate and adsorb maximum quantities of lead by all means without jeopardising its growth and metabolism would be preferable for growing along the roads so as to help mitigate the autoexhaust lead pollution. For this purpose percent increase of lead in plants (A) and soil (B) and percent retention of leaf area (C) and biomass (D) were calculated for all the plants species at all the traffic intersections with respect to N.P.L. Nursery (control site), the average of the sum i.e (A+B+C+D)/4 was designed as an Index of Lead Pollution Tolerance (L.P.T.I.). Higher value of the L.P.T.I. of a plant species would thus suggest its better suitability for lead accumulation and/or adsorption by tolerance. Among all the species studied Polyalthia, Alstonia and Eugenia seem to be the promising ones for their role in mitigation of autoexhaust lead pollution. L.P.T.I. values for all the species studied are presented in Table 5.