Fighting against POLLUTION to Save Environment
Fighting against POLLUTION to Save Environment
Proc. Seminar on “Pollution Monitoring an Control Technology” by Grammya Research Analysis Institute, Baroda, August, 1989. Report No.GRAI/TR – 8938.
D. B. Boralkar *, V. K. Gupta and S. K. Tyagi
Central Pollution Control Board, Sectional Office - Delhi, B.B. Marg, NEW DELHI - 110 019.
* Present Address : Western Zonal office, 46-B, Gautam Nagar, Race Course Circle, Vadodara - 390 007.
It is widely agreed that in urban and suburban complexes a primary source of Lead pollution is the gasoline. Non-automotive sources of Lead in urban and suburban environments may include coal combustion, refuse and sludge incineration, burning of lead painted surfaces and certain industrial processes.
In this method, lead in air-borne particulates is collected by drawing air through a filter. The filter, with collected particulates, is digested to prepare a test sample. Preparation of this sample is simple and rapid. The aqueous acidic sample is scrutinised by an atomic absorption spectrophotometer at a suitable wavelength and the concentration of lead is calculated.
This method has been used in the city of Delhi over a period of two years for determination of Lead in suspended particulate matter (SPM) in ambient air at important traffic intersections.
APPLICABILITY: This method is applicable to the measurement of the concentration of airborne particulate lead found in either ambient or industrial atmospheres.
MEASUREMENT RANGE: Because airborne-particulate-Lead may constitute 1 to 5% of airborne particulate matter, analytical sensitivity is not ordinarily a problem. Based upon the flame mode, washed glass filters and a nominal air sample volume of 2000 m³, Lead is measurable up to 0.010 µg/m³.
INTERFERENCES: No serious interferences have been reported for lead. Any possible interference due to silica from the glass fibre filters or silicates from samples can be overcome by allowing the acid extract to stand overnight and centrifuging at about 2000 r.p.m. for 30 minutes.
A prepared test sample, containing the inorganic constituents in aqueous acidic solution, is reduced in the flame furnace to the atomic state. The amount of Lead is measured by making use of its property of absorbing light of its characteristic frequency in the atomic state.
The most important reactions relate to the complete dissolution of the particulate sample in acidic medium to form a homogeneous test sample. As microgram quantities of material may be involved, losses due to incomplete dissolution, volatility, or absorption must be avoided.
Mount the glass fibre filter on a conventional high-volume or other sampler head. Draw air through the filter at a flow rate between 1.13 m³/min and 1.60 m³/min for an appropriate period, such as 24 h. Calculate and record the total volume of air sampled, in cubic meters, as the product of mean flow rate and time (APHA, 1977).
Cut the exposed filter into small fragments and place in a beaker. Initiate the dissolution of the filter matrix by adding 1 ml to 2 ml of nitric acid and continue to heat gently until a few drops of nitric acid are left. Addition of nitric acid can be repeated depending upon the filter matrix. Add 10 ml of water. Bring nearly to the boil and filter through a Whatman 41 filter into a glass beaker. Transfer to a 100 ml volumetric flask. Rinse the beaker with another 10 ml of water. Repeat the rinsing 2 to 3 times. Transfer to the 100 ml volumetric flask and make up test sample to the mark. Mix the contents of the volumetric flask thoroughly after adjustment to volume. Transfer the contents of the volumetric flask to a polyethylene storage bottle. The test sample is now ready for analysis. The above method applies to the digestion of glass fibre filters. Cellulose filters can be digested or extracted using nitric acid. Filter blank is run simultaneously with each batch (APHA, 1977; Environment Canada, 1976).