minimal during the high flow season. During the low flow season, P b from the same source of pollution might well reach 2.4 pg I,-’, but with no effect because of fixation by the soil for the same reason given previously. Gpneral Conclusions
During a complete year, the lead content varies in some river waters which we have analyzed from 14.4 to less than 0.2 pg L-l. Precautions in the analytical procedure show the highest values to be accurate. The lead fallout due to atmospheric rain leaching is higher than lead transport in river. The circulation of 21nPbshows that at least 87% of this atmospheric lead is retained by soils. During the high flow rate period, this pollution is thought to correspond to a maximum lead content in river waters. equal to 0.4 pg Dry lead depclsit on roads, which can be carried on to rivers, could lead to a significant increase in water lead content. This increase is not observed during the low flow season, indicating that the lead is retained by the soils. During the high flow season, pollution from this source falls below a significant proportion in Ariege and Garonne rivers, and could be negligible in the Hers river. It seems most likely that Pb originates from natural sources. It is easily accounted for by the presence of particles with high lead content, up to 200 ppm during high flow rate periods. During low flow rate periods, the lead content of river waters is reduced; as both the solid matter load of waters and their lead contents are lower, the lead content of the particles is then less then 50 pprn. Acknowledgment
We are grateful to Dr. Patterson from Caltech, Pasadena, Calif., for his critiques of the lead analysis values and for his kindness in letting us know the results of the IDOE study before publication.
L i t e r a t u r e Cited (1) Smith, W. H., Enuiron. Sei. Technol., 7, 361 (1973). (2) Lerche, H., Breckle, S. W., Naturu;issenschajten, 5, 218 (1974) (in German). (3) Impes, R., N’Vunzu, Z., Nangiot. P., International Symposium on Environmental Health Aspects of Lead, p 135, Amsterdam, Oct. 2-6, 1972. (4) “Biologic Effects of Atmospheric Pollutants-Lead”, National Academy of Sciences, Washington, D.C., 1972. (5) Chow, T. J., Nature ( L o n d o n ) ,225 (5229),295 (1970). (6) Durum, W. H., Hem, J. D., Heidel, S. G., U.S. Geol. Suru., Circ., No. 643 (1971). (7) Hem, J . D., Durum, W. H., J . Am. Water Works Assoc., 65,562-8 (1973). 18) Lazrus, A. L., Lorange, E., Lodge, P. J., Environ Sei. T e c h n o / , 4 (1).55 (1970). (9) Hem. J . D., Geochim. Cosmochim. Acta, 40,599-609 (1976). (10) Benninger, L. K., Lewis, D. M., Turekian. K. K., Am. Chem. Soc. S y m p . Ser., No. 18,201-10 (1975). (11) Fisenne, J. M., U.S. AEC, Rep. UCRL, 18140,145-58 (1968). (12) Moore, H. E., Poet, S. E., J . Geophys. Res., 81 (6), 1056-8 (1976). (13) Baltakmens, T.,N. Z. J . Sei., 17,435 (1974). (14) de Martonne, E., Demangeon, A., “Geographie Universelle”,Vol. VI, A. Colin, Paris, 1947. (15) Brunet, R., These &-sciences, Fac. Lettres et Sci. Hum., Toulouse, SBrie B, tome 1, 1965. (16) Kolthoff, I. M., Elving, P. J.,“Treatise on Analytical Chemistry”, Part 11, Vol. 6, Interscience, New York, N.Y., 1964. (17) Charlot. G.. “Les MBthodes de Chimie Analvtiaue”. “ . 5th ed. Masson et Cie, Paris, 1966. (18) Martin, J . M., Th6se &-sciences, A. Colin, Paris, 1971. (19) Abdullah, M. I., Royle, L. G., International Symposium on Environmental Health Aspects of Lead, Amsterdam. Oct. 2-5, 1972. (20) Patterson, C. C., personal communication. (21) Marenco, A., Fontan. J., Tellus, 24, 38 (1972). (22) Davidson, C. I., Hering, S. V., Friedlander, S. K., International Conference on Environmental Sensing and Assessment, Las Vegas, Nev., Sept. 18, 1975.
Receiced for reuieu: August 4, 1977. Accepted J u l y I O , 1978
A Sensitive Technique for Measurement of Benzene and Alkylbenzenes in Air Norman E. Hester” and Raymond A. Meyer Rockwell International, Environmental Monitoring and Service Center, Newbury Park, Calif. 9 1320
An automated gas chromatographic technique has been developed to monitor benzene and alkylbenzene concentrations in ambient air. Sub-parts-per-billionconcentrations can now be measured in air without using preconcentration or trapping techniques. Multi-day benzene and toluene measurements have been made, and typical Newbury Park, Calif., concentrations are in the range of 0.4 to 13 ppb. The concentrations of benzene and alkylbenzenes in ambient air are of interest for two significant reasons. First, benzene and the alkylbenzenes are known to be reactive photochemically (I). Second, it is suspected that long-term exposure to even trace levels of benzene and other aromatics can have harmful effects, and concern for these effects has led to a recent OSHA emergency exposure limit for benzene in air (2).
The common methods currently used for measurement of benzene and alkylbenzene concentrations in ambient air employ either trapping ( 3 ) or freeze-concentration ( 4 ) of 0013-936X/79/0913-0107$01.00/0
@ 1979 American Chemical Society
samples before analysis. These preconcentration steps are usually necessary because of the limited sensitivity of the flame ionization detection (FID) technique commonly employed for the analysis. Within the last 2 years photoionization detectors (PID) for gas chromatography have become commercially available, and recent work with this detection system on liquids has shown that the PID is one to two orders of magnitude more sensitive to most aromatics than is the FID (5-7). The application of the PID to the gas chromatographic determination of benzene and alkylbenzenes in air samples seemed timely, and the results of work in this area are reported in this note. Experimental
An automated gas chromatographic system was built by Rockwell for this study. This unit basically consists of an automated gas sampling valve, an isothermal oven, and a photoionization detector and electrometer (HNU Models PI-51 and PI-52). Chromatographic separations were done on a 6 f t X in. stainless steel column packed with 10% Volume 13, Number 1, January 1979 107
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