Fighting against POLLUTION to Save Environment

Autoexhaust lead pollution of roadside ecosystem in Delhi:

J. Ind. Asso. Environ. Mgmt. 19, 21-27, 1992.

D. B. BORALKAR, S. K. TYAGI and S. B. SINGH
Central Pollution Control Board, 'Parivesh Bhawan' , CBD-Cum-office Complex, East Arjun Nagar,
Shahdara DELHI-110 032

Lead in Vegetation

Contamination of plant due to atmospheric lead was generally considered to be surface phenomenon and largely susceptible to be removed by washing, scrubbing, etc.

The variation in lead content of all the three plant species varied significantly between February and May, 1985 (F-calculated 9.98 is greater than F-Table 5.32). However, there was no significant variation observed among the interaction between location, plant species and season, i.e., February and May, 1985. This suggests that the lead accumulation is influenced by the seasonal changes. Lead particles deposited from ambient air adhered to the surface of the plant parts and were less subject to removal by wind action during winter.

Generally there was reduction in the total chlorophyll content of leaves, total biomass production and total leaf area per plant at the five traffic intersections as compared with that of the NPL Nursery (Table 8). Close examination of data on the reduction of chlorophyll, biomass and leaf area revealed that among all the three plant species, growth performance of Eugenia (Jamun) was generally better as compared with that of the other two species.

Assessment of Impact of Autoexhaust Lead Pollution of Plant Species

One of the main objectives of the study is to screen and select the plants by field trials for their suitability to grow along the roadside so that they can serve as immediate filters of autoexhaust pollutants.

Quite logically, the choice will fall upon a plant species that would accumulate maximum quantities of lead by all means, while its optimum metabolism would not be in jeopardy. Therefore, percent increase of lead in plants (A) and soil (B) and percent retention of chlorophyll (C) biomass (D) and leaf area (E) were calculated for all the plant species at all the five traffic intersections and the NPL Nursery.

The average of the sum (A + B + C + D + E)/5 would thus give a Lead Pollution Tolerance Index (LPTI). Higher LPTI of a plant species would thus suggest its better suitability for lead accumulation by tolerance, and such species could be recommended for plantation along the roadside.

Among the three species studied over the period of six months from November, 1984 to May, 1985, at most of the traffic intersections (80%), the maximum value of LPTI was recorded in Eugenia plants followed by Nerium and Alstonia (Table 9).

AUTOEXHAUST LEAD

Table 8 : GROWTH PERFORMANCE OF PLANTS* OF DIFFERENT SPECIES COLLECTED FROM DIFFERENT LOCATIONS

Table 9 : LEAD POLLUTION TOLERANCE INDEX (LPTI) OF PLANT SPECIES AT DIFFERENT TRAFFIC INTERSECTIONS

Most promising one followed by Nerium. The former, a tree species, could be planted along the roadside; while latter, being a shrub, would be suitable for growing in the road-divider channels.

FINDINGS

The general levels of lead in the ambient air at five different traffic intersections are in the range of 185 ng/m3 to 324 ng/m3, while background concentration at NPL Nursery was 62 ng/m3 (Table 4).

The lead content in soil in the pots of the three plant species at all locations increased in May, 1985 as compared to February, 1985. But this increase was found to be insignificant when the data were subjected to the analysis of variance.

Lead accumulation in plant (root, shoot, leaf and leaf washing) had significant variation between May and February. It was more in February than in May (Table 7).

Eugenia (Jamun) was found to be suitable for growing along the roadsides. The tree would not only accumulate and adsorb the lead from the autoexhaust but shall also provide shade for human beings and shelter to the birds.

Nerium (Kaner), a dense shrub, is suitable for growing in the road divider channels. The profusely dense leaves on branches can serve as filters of particulate pollutants emitted from the autoexhausts.

FURTHER WORK

Considering the fact that the behaviour of plant species under the impact of any specific chemical varies widely and that the duration of investigation on three plant species is very short (only 10 months) and therefore, investigations using a few more plant species have been conducted and published elsewhere.

ACKNOWLEDGEMENTS

Authors gratefully acknowledge and thank Central Pollution Control Board for its permission to publish this Paper.

REFERENCES

• C.B.P. & C.W.P. (1987). Calendar. 7957-88, Central Board for the Prevention & Control for Water Pollution, New Delhi.
• Page AL; Ganje TJ and Joshi MS (1971). Lead quantities in plant, soil and air near some major highways in Southern California. Hilgardia, 41(1), 1–31.
• Smith WH (1976). Lead contamination of the roadside ecosystem. Air Poll Control Assoc, 26(8), 753–766.
• Flanagan JT; Wade KJ; Currie A and Curtis DJ (1980). The deposition of lead and zinc from traffic pollution on two roadside shrubs. Environ Pollut (Ser. B), 1(1), 71–78.
• Khandekar RN, Kelkar DN and Vohra KG (1980). Lead, cadmium, zinc, copper and iron in the atmosphere of Greater Bombay. Atmos Environ, 14, 457–461.
• Shrivastava JP (1986). Status of selected trace elements in some common vegetables. Indian J Air Poll Control, 7(1), 19–24.
• Boralkar DB; Mukherjee U & Singh SB (1986). Increase of lead concentration in ambient air during the IX Asian Games, New Delhi 1982 as indicated by the plants. Indian J Air Poll Control, 7(2), 65–73.
• APHA (1977). Methods of Air Sampling and Analysis. Second Edn., American Public Health Association.
• Jackson ML (1958). Soil Chemical Analysis. Prentice-Hall of India Pvt. Ltd., New Delhi.
• Aron DI (1949). Copper enzymes in isolated chloroplasts. Plant Physiol, 24(1), 1–15.
• Mishra R (1968). Ecology Workbook. Oxford & IBM Publishing Co., Calcutta.
• Boralkar DB; Tyagi SK and Sengupta (1990). Autoexhaust lead pollution of roadside ecosystem in Delhi (Part-II). Proc. International Conference on Environmental Planning and Management, University of Roorkee.

* (ug/g Dry Wt. of Root + Shoot + Leaf Washing)