Introduction to analytical methods to measyre air pollution
Answers
The analytical approaches employed in the study and control of air pollution are rapidly attaining a degree of sophistication that would have been impossible to achieve even one decade ago. The relatively crude and inefficient gravimetric and titrimetric methods once used have been replaced by sensitive reliable and rapid procedures such as those based on chromatography, infrared spectroscopy, fluorometry, spectrophotometry, atomic absorption spectros- copy and ring oven techniques. In spite of the progress that has been made, is still much to be done. Fortunately, the fundamental principles are well established and most of the effort remaining can be directed toward their applications for air pollution study. In addition to the techniques mentioned above, developments and applications in the fields of the electron microprobe, x-ray fluorescence, ion-selective electrodes, thin-layer chromatography, spe- cffic reactions, dispersion staining and neutron activation will contribute significantly. The needs for analytical advances fall in three general areas; critical or definitive studies, field tests and monitoring methods. The definitive studies of air pollution require analytical approaches that are the ultimate in reliability and sensitivity. Critical or referee determinations must provide exact data for research, standards for reference analytical comparisons and legally acceptable information for presentation in cases involving litigation. Field methods are required for emergency use and for surveys and similar investigations, where qualitative information and immediate quantitative approximations are required. Finally, there is great need for continuous and automatic measurements that can provide basic background data on pollutant levels, variations in concentrations, and interrelationships existing between significant species in complex mixtures of pollutants.
Among the common gaseous pollutants, sulphur dioxide, hydrogen sulphide, oxides of nitrogen, hydrogen fluoride, chlorine, hydrogen chloride, hydrogen cyanide, ammonia, carbon monoxide, ozone and hydrocarbons (and their derivatives) are of most general concern. Particulate pollutants are of interest in terms of the total dustfall, sootfall or stain index. The identification and determination of individual species is becoming critically important and it is no longer acceptable to report only simple values of mass or particle counts.
For example, both organic and inorganic carcinogens should be measured. In the latter group asbestos, arsenic, beryllium, chromium and nickel have been indicted as carcinogenic to man; and lead, selenium, titanium, cadmium, cobalt, mercury, silver and zinc have been demonstrated to be carcinogenic in animal studies.
Much could be said about the determination of other gaseous pollutants, but here only brief comments on analytical methods for the more important pollutants can be offered.
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