Lead , Bromine , Chlorine , and Iodine in Polluted

Content Provider	Semantic Scholar
Author	Lininger, Ronald L.
Copyright Year	2010
Abstract	Ten samples of particulate matter of radius greater than 0.5 microns have been collected on the M.I.T. campus in Cambridge, Mass., using a Casella four-stage cascade impactor. Concurrent values of environmental parameters are also noted. Analysis for lead has been performed using total deposition anodic strippic voltammetry, a new method developed and carried out by another researcher, which method is briefly described herein. Analysis for bromine, chlorine, and iodine substance has been conducted by pile neutron activation. The concentrations of particulates measured in this study show generally good agreement with the previous work of other investigators. The amounts per cubic meter of air are of the order of: for lead and chlorine, 10 6 grams; for bromine 10-7 to 10 grams; and for -9 iodine, 10 grams. The data indicate that bromine pollution from automobile exhausts is clearly in excess of bromine from maritime sources only when there is haze, smoke, or fog present in amounts sufficient to restrict the visibility to about five miles or less. In all cases, the ratio Br/Pb observed is several times smaller than in gasoline. To account for this observation, a theory is proposed suggesting a photochemical reaction which releases gas-phase bromine from automobile exhaust particles. This reaction may be inhibited by the presence of soot and water vapor in the air under conditions of low visibility. Seven simultaneous measurements of ozone, obtained from a separate study by another colleague, are related to the value of chloride concentration totals observed herein. A simple linear correlation coefficient is calculated as -0.55. Though this statistic is uncertain because of the limited number of samples, the results of a literature search suggest two independent mechanisms by which a negative correlation might be expected. The first mechanism is a complex series of reactions between ozone and chloride resulting in a destruction of ozone proportional to the amount of chloride present. The second mechanism involves the effect of nitrogen dioxide, which is suggested to be creative of ozone and destructive of chloride in particulate form through the release to the gas phase of HC1. Because of the theoretical arguments, further work seems Justified to obtain more data upon which to base a correlation coefficient of greater statistical significance. Brief remarks are included attempting to explain the relation of the environmental parameters observed to the variability in the pollutant data. In addition to the effect of low visibility stated above, relationships are noted with traffic density, rain, wind direction, and change of air mass. Thesis Supervisor: John W. WInchester Title: Associate Professor of Geochemistry Thesis Co-Supervisor: Reginald E. Newell Title: Assistant Professor of Meteorology
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Alternate Webpage(s)	http://dspace.mit.edu/bitstream/handle/1721.1/54320/17392130-MIT.pdf?sequence=2
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article