A and C : Geometric mean of 10, once-a-monlh, observations
B           : Geometric mean of 7, once-a-month, observations
D           : Geometric mean of 9, once-a-month, observations

The base data (Table 4) were subjected to the analysis of variance. The variation in ambient air lead concentration is significant (F-calculated 8.785 is greater than F-Table 3.49) between timings. The variation due to location (F-calculatcd 3.269 is equal to F-Table 3.26) is not significant. As expected, lead concentration in ambient air during lean traffic period (between 12 noon and 4 p.m.) was lower than the morning and evening peak periods (9 a.m. to 12 noon and 4 p.m. to 7 p.m.). If any two timings are taken in pair for the analysis of variance, the variation between any pair of timings remains significant. Ambient air quality in regard to lead and other pollutants is required to study the impact of lead in synergism with other environmental constituents on plants specially located in traffic intersections. For such purpose, the 10-hr long measurement between 0900 and 1900 hours was decided to be adopted.

It was felt that a 10-hr continuous air sampling might adversely affect the SPM retention of the glass fibre filter (EPM 2000, Whatman). To examine this aspect, at Delhi Gate Traffic intersection, cumulative deposition of lead and SPM was studied. The results revealed that cumulative values of hourly lead and SPM deposition were in quite conformity with the values corresponding to those of total hours (Table 5). It was, therefore, concluded that a representative air sampling of 10-hour day time traffic hours can be done continuously.

Lead in Soil : The base data (Table 6) show that lead in the soil has increased in May 1985, compared with that in Feb. 1985, in all the pots of 3 plant species and at all locations. The analysis of variance of the data revealed no significant difference in lead content of soil between locations, seasons and plant seasons (F-calculated 6.67 is greater than F - Table 3.80) indicates significant variation.

Table 5 : COMULATIVE DEPOSITION OF LEAD AND SUSPENDED PARTICULATE MATTER*

Sr.No.	Time	Cumulative deposition
		Pb (ug)	SPM (mg)
1.	1000 to 1100 hrs (1-hrly)	0.41	58.3
2.	1000 to 1200 hrs (2-hrly)	0.54	110.4
3.	1000 to 1300 hrs (3-hrly)	0.73	160.9
4.	1000 to 1400 hrs (4-hrly)	0.83	191.7
5.	1000 to 1500 hrs (5-hrly)	0.96	240.4
6.	1000 to 1600 hrs (6-hrly)	1.08	353.5
7.	1000 to 1700 hrs (7-hrly)	1.28	414.6
8.	1000 to 1800 hrs (8-hrly)	1.62	475.4
9.	1000 to 1100 hrs (1-hrly)	0.38	53.3
10.	1000 to 1100 hrs (1-hrly)	0.13	39.2
11.	1100 to 1200 hrs (1-hrly)	0.14	42.1
12.	1200 to 1300 hrs (1-hrly)	0.13	43.2
13.	1300 to 1400 hrs (1-hrly)	0.13	60.2
14.	1400 to 1500 hrs (1-hrly)	0.12	71.2
15.	1600 to 1700 hrs (1-hrly)	0.20	83.7
16.	1700 to 1800 hrs (1-hrly)	0.19	83.8

*At Delhi Gate Traffic Intersection on 04/06/85

Condensed version of Table 6 is given with a view to indicate that winter and summer values of lead at Azadpur intersection, being significantly different from thr rest, cause interaction between locations and seasons to be significant.

Location	Winter February	Summer May
Delhi Gate	19.00	23.66
India Gate	22.66	25.33
Red Fort	28.00	28.00
Ashram	21.66	25.33
Azadpur	16.00	33.53

Table 6 : LEAD IN SOIL FROM POTS WlITH DIFFERENT PLANT SPECIES AND DIFFERENT LOCATIONS (ug/gm)

S.N.	Location	Traffic Density Class	ALSTONIA		EUGENIA		NERIUM
			Feb.	May	Feb.	May	Feb.	May
1.	Delhi Gate	I	14	27	20	22	23	22
2.	India Gate	II	25	25	22	30	21	21
3.	Red Fort	III	29	31	24	27	31	26
4.	Ashram	IV	25	25	17	27	23	24
5.	Azadpur	V	14	32	14	31	20	37
6.	NPL Nursery	-	6	23	3	19	4	20

Lead content of plants (ug/g dry wt. of root + shoot + leaf washing) of different locations in February, 1985 and May, 1985 is presented in Table 7. It is seen from the results that, at most of the traffic intersections, the lead content was higher as compared with that at NPL Nursery. The response of all the three species was different to the lead accumulation. Maximum accumulation of lead in samples of both the months, i.e., February (first quarter) and May, 1985 (second quarter) was found in Eugenia (Jamun) followed by Nerium and Alstonia. The accumulation of lead in plant species from five intersections was not found to be related to the traffic density .

Table 7 : LEAD CONTENT OF PLANTS* OF DIFFERENT PLANT SPECIES COLLECTED FROM DIFFERENT LOCATIONS

Sr.No.	Location	Traffic Density Class	ALSTONIA		EUGENIA		NERIUM
			Feb.	May	Feb.	May	Feb.	May
1.	Delhi Gate	I	645	221	794	465	373	366
2.	India Gate	II	462	212	533	371	482	191
3.	Red Fort	III	274	145	989	282	541	115
4.	Ashram	IV	530	247	306	584	662	430
5.	Azadpur	V	322	220	111	170	80	127
6.	NPL Nursery	-	232	140	154	69	208	105

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