DETERMINATION OF LEAD AEROSOLS
Lead (one of heavy metal), contributes only a small fraction to air pollution. Lead is emitted into the atmosphere from smelters that recover primary lead from ores and secondary lead from scrap. In urban areas with a large number of motor vehicles, the most important source of atmosphere lead is probably exhaust emission. The level of atmospheric lead varies directly with the size of the community and the traffic. The concentration is higher in commercial and industrial areas. The concentration tends to be high during the periods of low atmospheric turbulence. Annual permissible concentration = 0,5 µg/m³ ; in the working area- 0,05 mg/m³.
Express colorimetric drop method for lead aerosols determination in working area
PRINCIPLES: Lead particles from the air remain on the surface of the paper with hand pump. Lead reacts with sodium rhodisonate to produce lead rhodisonate with pink-red color.
TECHNIQUE: Air sample with volume of 10 dm³ is aspirated using aspirator and is drawn through the paper filter.
Nine filter paper disks are arranged on the glass slab. First eight disks are clear and final disk contains the sample.
- Drop in the centre of each clear disk the 0,01 ml standard solution and dry them.
- Drop in the center of all disks the following:
- a) 0, 01 buffered solution and dry
- b) 0, 01 ml sodium rhodisonate and dry
- c) 0, 01 ml 3% H₂ O₂ and read, using color scale while they are moist
RESULTS:
Where: C – concentration of lead aerosols, read by using color scale (converted to mg)
V₀ – adapted to standard condition volume of the air sample (1 mg = 1000 µg)