Deposited atmospheric chemicals A mountaintoppeat bog in Pennsylvania provides a record daring to I800
been variable, and they d e pend on interactions within the stratosphere, troposphere, biosphere, Lithosphere, and ocean.C o m e quently, appropriate samples for tracing changes must be related to wind direction and precipitation pattems as well as to the sources of chemical inPt. Regional changes in the deposition of mate.rials to terrestrial ecosystems have been measured recently in samples collected from peat bogs. Reducing conditions, which are normally found below the surface layer, preserve the record of pollen grains and chemicals deposited. Fallout radionuclides from nuclear weapons testing (a) and natural radionuclides from the decay of uranium have been deposited. These serve as tracers to measure the deposition history of manufactured chemicals introduced into the troposphere.
William R. sebell Universiiy of Pittsburgh Pittsburxh, Pa. 15261 The Northern Hemisphere is experiencing a series of severe ecological problems with forest decline; loss of fish in lakes, streams, and estuaries; and corrosion of monuments, buildings, and mads. These and associated problems were addressed at the International Symposium on Acidic Precipitation at Muskoka, Ont., in September 1985 and at the Hudson River Fcundation Conference on Acidification and Anadromous Fish of Atlantic Estuaries in October 1985. Cicumstantial evidence presented at these meetings pointed toward the deposition of atmospheric chemicals, espiaily nitric and sulfuric acids, but few quantitative measurements compared today's conditions with those occurring over the past 200 years. There are a number of questions to ask Was the impact of regional industrialization greater before pollution controls were introduced? Have pollution controls selectively m o v e d particulate matter (usually basic) while allowing gaseous (acidic) matter to escape? What effect have forest clearing and other land use practices had on the introduction and removal of chemicals from the atmosphere? Better scientific evidence is needed to
allow scientists to compare and assess the relative effects caused by civiliition before and during the Industrial Revolution. Changes caused by industrial, chemical, and nuclear activities have been measured in glaciers (1-3), sediments (4, and peat bogs (5).The rates of material deposition to such reservoirs have
W13~6w86108200847$01.50100 1886 American Chemical Society
Physiography, methods A bog site at an 823-m elevation near the peak of the Laurel Mountains in the Alleghenies ( 4 0 O 7 ' N, 79'11' W; Forbes State Forest, Harrisburg, h . j has been sampled. Because the bog is only 30 m below the peak of the mountains, nutrients and trace elements come from the atmosphere and not from runoff or from bedrock via springs in the watershed. This 11.2-hectare (28-acre) bog ecosystem represents a succession of vegetation changes since 1800, from Envimn. sci. Technol., Vol. 20, No. 9, lssS 847
Iny = 3.5372-0.171?~
-1920
-1900
@
I
/
virgin hemlock forest to clear cutting to reforestation. By 1894, clear cutting had caused a rise in the water table that produced a swamp or bog as a consequence of eliminating evapotranspiration from the forest of the undrained basin. Now, evapotranspiration again removes the excess precipitation due to the vegetation present. In 1909, the Commonwealth of Pennsylvania purchased this region, which is about 60 Irm to the east of Pittsburgh, as the first public land in the Ohio River watershed and preserved it as part of the Forbes State Forest. Wind patterns of the Laurel Mountains are intluenced by air masses passing over the Great Plains. The humid, continental-type climate receives 135 cm of precipitation evenly throughout the year. This precipitation is from moist air that is transported northward from the Gulf of Mexico and the Atlantic Ocean to meet cold arctic air from Canada traveling southward across the Great Lakes. Often the air masses meet and deposit moisture at the first mountainous region, the Laurel Mountains. The prevailing westerly winds also transport and deposit atmospheric particulates and gases that originate in the heavily indusaialized regions of Pennsylvania, Ohio, West Virginia, Indiana, and Michigan. Core samples from the upper layers of the bog were collected by driving a l k m diameter polyvinyl chloride tube vertically into a low-lying bog hollow 848 Environ. Sei. Technol.. MI. 20, No. 9,1986
away from tree roots and hummocks. npatment of the core included sectioning, weighing, drying at 70 OC, and homogenizing. Aliquots of each section were then taken for 137Cs,226Ra,zlOPb, S, N, C, H, and Br and for trace element analysis (7-9). Quality control of the y-radionuclide and chemical element measurements was checked by calibrated internal standards and by a National Bureau of Standards standard reference material (NBS SRM). The analytical variance expected was no larger than 10%of the value at the concentrations measured. Analysis of the several elements by instrumental neutron activation analysis (INAA) on duplicate samples was used to test the analytical precision in measuring elements, including sample homogeneity and instrumentation. Of the 34 elements measured, only W, 'Et, and Zn showed >40% differences between duplicates, indicating a possible deposition of single particles of the pure element. Chronology of deposition To develop the chronology of a core, natural levels of zlOPbare determined to ether with its parent radionuclide, 22%Ra. The 210Pb is produced from zzzRndecay (half-life of 3.8 days) after 2z2Rndiffuses into the atmosphere from soil that contains z26Ra.Because of this short half-life, a continuous source of zlOPbis produced by decay for deposition on the earth.The zloPbin excess of the amount in equilibrium with 226Ra
(that is, the unsupported amount) is used to date the deposited layers. It is assumed that zlOPbis in constant flux and that it is immobilized in the sediment. Figure 1 uses the CRS Model (8,9) and data for unsupported 210Pbto show the chronology of the core at depths of the sections. The integrated amount of 210Pbdeposited, 62.4 disintegrations per minute per square centimeter (dpm/cm2)-equivalent to 1.04 Becquerel international units of radioactivity per square centimeter (Bql cmz)-is obtained by adding the values from each section. Thus, the mean annual flux of zloPb to the peat bog is 1.95 dpm ~ m - ~ y r - ' ( 6 2 .h4 dpm cm-2yr1).Comparisons made of forest soils in the mountains of New Hamp shire showed deposition rates of 0.77-2.38 dpm cm-2yr1(IO). The explanation for the difference in the d e p sition rates can be found in the types of vegetation and in the impaction of cloud droplets on foliage (11). Graustein and 'hrekian state that "the measurement of 210Pbin soils is a practical way to study the effects of local variables, such as elevation, clouds, or vegetation, on the rate of delivery of submicrometer aerosols to the land surface" (la). The zlOPbdating of the sections may be approximated for one year, 1963, using 137Csfrom nuclear weapons tests. The 137Cswas first produced in large quantities for global fallout by the Ivy test conducted in 1952 at Eniwetok Atoll in the western Pacific Ocean. In subsequent nuclear tests the fallout of radionuclides increased to a maximum at 1963 and then decreased following the Nuclear Test Ban lkeaty in 1963. Figure 2 shows the I 3 T s deposition rate. The maximum deposition of IS7Cs is found in the 1956-64 (8-10 cm) layer, at a time corresponding to the maximum fallout from tests. The f i t detection of "'Cs, however, is found between 1932 and 1939 (14-16 cm), or about 20 years before the beginning of nuclear weapons fallout into the environment. This apparent anomaly is caused by initial mixing in the saturated peat bog, by diffusion and advection of 137Cs through the pore water, and by uptake in root and plant material (biological pumping or nutrient recycling) in the intervening 30 years since deposition. The approximate diffusion coefficient calculated, 1.1 x IO-* cm-2s-1, is 100 times smaller than that measured in marine and lake sediments (12, 13). The smaller peaks from nuclear weapons testing in 1958, 1956, and 1954 are smoothed by this diffusion. However, the amount of i37Csde sited (18.8 pCi cm-2, 0.695 Bq cm-p".in July 1983) probably remains in the core profie.
Comparisons of I3'Cs deposited from global and Nevada Test Site fallout have been made in Utah (14). An empirical relationship was found for global fallout, ("7Cs)0, and annual precipitation, P, over a range of 15-50 cm
(15): (I37CS)G = 2.22 P 26 mCi k d (1) The 137Cspredicted from this relationship for the Spruce Flats Bog, corrected for decay to year of deposition, 325 mCi km2,appears to fit to within the 13% estimated error even though the precipitation is 135 cm. It is believed that the amount of I3'Cs and 210Pbfallout deposited depends on the tropospheric particle removal processes (16) and on scavenging by terrestrial plants (17, 18). The '37Cs originates in the stratosphere but is added to the upper troposphere and removed by particulates in a manner similar to that for removing zlOF'b.The tropospheric residence time for particulate matter is 4-30 days, and both radionuclides are sorbed and deposited with tropos heric particulate matter (14, 19). The 7CsIS predominately a long-range tracer of particulate deposition from the entire troposphere, whereas 210Pbis a more regional tracer of particle deposition from the lower troposphere.
+
P '
Mass deposition Figure 3 shows the instantaneous mass deposition rate, a value related to the net of biomass productivity (input) and decomposition (loss) in the bog (20). During forest clearing, the mass deposition appeared to increase to a maximum at the time when clear cutting was completed and then decreased. Such a consequence could be possible if the nutrients and other atmospheric ma-
terials were no longer being intercepted by the lower elevation forest. During subsequent ecological changes, the a p parent mass deposition on the bog has decreased.
Deposition of elements Figure 4 (available as supplemental material) shows the deposition profile of carbon, sulfur, nitrogen, and bromine. Carbon concentrationsdecreased from 42.14% at the 0-2-cm layer to 1.0% at the 3CL32-m layer; similar losses are found for hydrogen. Such values are not typical of peat deposits (21). Because the peat layers are dated,
the use of net accumulation rate corrects for compaction. However, the mass accumulation calculated now may not reflect the amount of mass and elements at the time of deposition. This results from diagenesis of the peat ecosystem; the inorganic fraction remains intact, and the organic fraction is decomposed by microbial activity into C@ and C&. The sulfur accumulation is the minimum amount deposited because the loss of volatile H2S, CH,SH, and (CH&S occurs through anaerobic decay by bacteria (22). The current sulfur accumulation rate (0.19 mg cm-2yr1) has resulted from a steady increase and is now at least 20 times that of the 3CL32cm layer (from 1817). In terms of sulfur as a nutrient for agriculture, the current deposition^ rate at the Spruce Flats Bog is 19 kg ha-lyr'. In contrast, 18.8 kg ha-lyrl was estimated in 1978 at Hubbard Brook, N.H. (23). These data can be compared with measurements of acidity for the adjacent Linn Run-Wildcat Run watersheds (24). For the average chemistry of soil water on the Wildcat Run watershed during four major dormant-season runoff events in 1982, the concentration in p q l L was 170 for surface melt and throughfall, 256 for organic soil leachate, and 370 for mineral soil leachate (24). To test the annual deposition estimates from the bog core for accuracy, the deposition amount of Sod2- was converted to the concentration (pq/L) expected in precipitation. Using values for 0-6 cm (13.3 yr), t h ~
1981.7 3.8 1977.6 4.4 1972.9 5.1 1967.3 5.8 1960.3 8.3 1952.0 8.2 1943.8 8.3 1935.6 7.9 1927.1 9.0 1917.9 9.4 1909.5 8.3 1898.7 12.5 1886.3 14.3 1888.8 18.6 1845.2 28.3 1817.2 28.3 1778.0 30.0 1757.0
Envlmn. Sci. Technol., MI. 20. No. 9, 1988 849
annual average concentration for in precipitation for the 1970-83 period is 256 peq/L. Nitrogen accumulation is also shown in Figure 4. Nitrogen fixation and the denitrification process are responsible for the profile that is measured now. Because nitrogen is required for the synthesis of amino acids in plants, the actual anthropogenic input to bog vegetation is the amount in excess of that required by carbon in photosynthesis. Assuming that the bog vegetation has had the same ratio of nitrogen to carbon over time, the change in ratio would indicate the excess nitrogen input. The NIC ratio of 1977 vs. 1845 represents a factor of 2.7 times excess nitrogen input. The current total nitrogen deposition rate (1.0 mg cm-zyr') is now 45 times that of the 30-32-cm (1817) layer, assuming that no losses have occurred. In terms of nitrogen as a nut+ ent for agriculture, the current deposition rate at the Spruce Flats Bog is 100 kg ha-'yr'. Bromine deposition rates are also shown in Figure 4. Bromine reacts with organic compounds in plants and is
850 Envimn. Sei. Technol.. Vol. 20. NO.9. 1986
present in oil, leaded gasoline, and bituminous coal at 43 ppm (NBS SRM 1632a); it appears to be deposited and retained similarly to sulfur and nitrogen at the Spruce Flats Bog. However, bromine does not participate in the same anaerobic decay processes that are responsible for losses of sulfur and nitrogen from the bog ecosystem. Deposition rates for sulfur, nitrogen, and bromine appear to double every 25-35 yr. Nitrogen increases continuously, whereas the sulfur deposition rate appears almost constant after 1970, when controls, an increase in dispersion, or a decrease in combustion altered the previously established trend.
mace constituent deposition The measurements of trace constituents (Figure 4) represent the average deposition rate of elements each year during the time represented by the section of the core. For example, a 2-cm section at 28-30 cm represents 28.3 yr (1831.3-1859.6), whereas a 2-cm section at the top of the core represents 3.8 yr (1979.8-1983.6). Thus, the time-dependent deposition of elements is
treated identically to the '37Cs and *'OPb profiles developed previously, assuming no addition to or loss from the watershed. The alkali elements, as represented by cesium, are assumed to be most soluble (25). These elements are similar to the chemically insoluble elements europium, aluminum, vanadium, manganese, tantalum, and hafnium, with a maximum in 1909 and a minimum in 1983. Thus, it appears that these elements, which have widely different chemical properties, are all reacting similarly and are retained by the bog ecosystem. Several factors contribute to this total retention of elements by the bog. Elements are strongly adsorbed in peat, which has a cation exchange capacity 100-1ooO times greater than that of clay soil. Humification of certain peats produces much greater cation exchange capacity, which further limits the migration of elements (5). When organic matter decomposes, inorganic sediments of claylike material remain to further retard migration. The lead deposition change found in
western Pennsylvania, from 2.2 to 13 maximum in 1909 (2C22 cm), with an pg cm-2yr1in 1817 and 1978, respec- abrupt decrease in deposition after the tively, can be compared with values 1960 (8-10 cm) sections. These data from other areas. The natural flux of may indicate that controls instituted by lead to Lake Michigan before 1860 was coal-fired electrical power plants and 0.17pgcm-2yr',~mparedwith2.4@gby heavy industries reduced partidate cm-2yr1in 1978 (26). Near Seattle, the emissions to the atmosphere and that lead flux decreased with distance downthe maturing forests on the windward wind from the city in 1979 from 20.6 slope leading to the bog intercepted the pg cm-2yr1at Lake Washington, to 3.4 particles. However, emissions of iron pg cm-2yr-l at Lake Samamish (10 and of elements that are volatile on km), to 1.4 fig cmPyr' at Chester combustion (such as S, N, Br, As, Sb, MOM Reservoir (40 km) (27). Cd, and Pb) have not shown a decrease In the remote Thompson Canyon in the bog to 1983. Table 1 shows the enrichment factor near Yosemite National Park, the atmospheric deposition recorded in 1980, over time for lead and other elements in 0.4pg cm-2yr1,is 20 times that depos- excess of their natural abundances usited before 1885 (2s). In three northern ing aluminum or scandium as the norNew England lakes, the current lead maliziig factor (30, 31). flux has increased by some 10 times over the backgmund level since 1860 to 3.25 pg cm-2yrl (29). The trace elements measured are indicators of industrial effluents from nearby coal combustion, mining, and steel production. Fly ash from coal burning is shown by the increased deposition of aluminum, barium, magne- Using 1817 as the baseline, the relative sium, vanadium, and uranium to a enrichment (REf,), (that is, Efx
[PresentIlEf, 118171) is used to identify changes in classes of anthropgenic e l e ments. No REfx is observed for the rare earth metals, the alkali metals, or for Mg,Ta,U,andV Co, Cr, Se,W, and Ba show less than a factor of two REf,. As, Cd, Zn,P, Fe, and Mn have REfx of 2 to 10 times. Pb, Ca, and Sb have REf, of 10 to 40 times. C1, N, S, and Br have REfxof greater than 100 times. These enrichment factors represent the amounts of elements transported in the atmosphere and deposited on the bog in excess of the amounts present in the Earth's crust. The history of the enrichment factors illustrates the change in element deposition that is the result of human activity. At a given sampling site, the enrichment factor before human activity can be used as a baseline for the enrichment of elements up to the present. This method is probably the most accurate means of determining relative enricbment factors for elements in a region.
Overview A mountaintop bog in western %Msylvania serves as a reservoir for mate-
EnvIm. Scl. Technol., Vol. 20, NO.9,1986 0661
rials deposited from the atmosphere.
Biological activity in the bog decomposes plant matter, which becomes humified and mineralized at increasing depths. Little or no mixing of elements occurs below the active root zone, where anoxic conditions exist, except by diffusion and advection from water transport. Radionuclides produced by natural means and by nuclear weapons have been used to measure the ages of the layers deposited during the growing season of each y e m However, possible Agration of mobile elements, such as 13’Cs, must be considered in interpreting the period studied. The upper layers of the bog indicate that the d e p sition of total sulfur is at least 20 times and that of nitrogen is 45 times the value estimated prior to cutting the forest, with a doubling time for each of 25-35 yr. Bromine deposition also doubles every 35 yr, and although it serves as an analogue element for sulfur and nitrogen, it does not volatilii by anaerobic decay processes in the bog. The pattern of mass and element deposition illustrates the changes in land use (forest succession) and industrial effluents that were sources for the material deposited on the bog. The decrease in atmospheric particle removal shows up in the 1960 and later layers. Compared with terrestrial abundances, the relative enrichments over time for chlorine, nitrogen, sulfur, and bromine are more than 100 times those calculated for 1817; lead, calcium, and antimony are 10 to 40 times greater. Regional trace element signatures have been identified where proportional amounts of air masses at eastern stations have originated from the Midwest, Canada, and eastern North America (32). Although these new methods Can define chemicals in CUTrent air masses,the pollutant history of any region cannot be obtained except by measuring natural repositories, such as bogs or wetlands. Recent data collected at mountaintop bogs in N~~ yo&and no& western Virginia show patterns of trace &Pition similar to, but two to four times lower than, those in the Pennsylvaniabog (33).One notable ex852 Environ. Sci. Technol.. Vol. 20. NO.9. lsS6
ception is the deposition of vanadium, partly originating from oil combustion, which has now increased five times since 1800 in New York but has remained constant in Pennsylvania. Because the Pennsylvania site is downwind and near the center of the most heavily polluted region of the country (at the headwaters of the Ohio River), the high deposition rate for
College Park, Md. 20742; and Kenneth Rahn, University of Rhode island, Kingston, R.l. 02881.
Supplementary material available Figure 4 contains additional deposition rate information for 12 elements. Data are presented for carbon, nitrogen, sulfur, bromine, antimony, arsenic, cadmium, lead, cesium, aluminum, vanadium, and iron. Copies of the supplementary material from thii paper on microfiche (105 x 48 nun. 24x reduction, negativesj may be obtained from Microforms and Back Issues, American Chemical Societv. 1155 16th St.. N.W.. Wkhington, D.C.’20036: Full bibliographic citation (journal, title ofarticle, author) and prepayment, check or money order for $6 for photocopy ($8 for foreign) or $8 for microfiche ($7 for foreign), are
I
( I ) Herron, M. M. . I . Geophys. Res. 1982.87. 3052-60. (2) Weiss, H. et al. Geochim.
and Chem’cd Dating Techniques; Currie, L. A., Ed.; ACS Symposium Series 176; American Chemical Society:
Coast Ma,: Sci. 1977,5, 549-
many trace elements derived from coal combustion is expected. The ef. fects of atmospheric chemicals deposited on ecosystems often occur over decades. Thus, the information on pollutants from regional sources, together with the new data on the history of element deposition, may give the information required to the human effect on the global ecosystem. AcknowWment I would like to thank L. Sepesy, J. Miller, 1. C. Rosen, J . Sykora, V. Schmidt, c. Ford, R. Streeter, G. Shephard, andDinatale. K. E Oldfield, C. W.SchelL D. Schiller, Before publication, this article was reviewed for suitability as an ES&T feature by Glen Gordon, University of Maryland,
(5) Parkarinen, F!; Tblonen, K. Ambio 1976,5,3840. (6) DeOeer, L. E. et al. In “Foryarets for Skingsanstslt, FOA Report C W 8 9 T2 (AI) 1978: Environmental Quarterly, EML-349 Environmental Measurements Laboratory, Department of Energy: New York, 1978; pp. 149-61. (7) Schell, W. R. In Nuclear and Chemical Dating Techniques: Currie, L. A., Ed.; ACS Symposium Series 176; American Chemical Society, Washington, D,C,, 1982; pp, 331-61. (8) Appleby, F! 0.;Oldfield, E a r e n a 1978, 5. 1-8. (9) Oldfield, E; Appleby, p. 0.;Battarbee, R, w,Nature 1978, 271, 339-42, (IO)craustein, w.c . ; lhrekian, K. K. In precipitation Scavenging, Dry Deposition and Reswension: Prumacher, H. A., Ed.; Elsevier: Amsterdam, the Netherlands, 1983; pp. 1315-24. (11) Lovett, 0.M.; Reiners, U. A.; Olsen, R. K. Science 1982,218, 1303-4. (12) Duursma, E. K.; Bosch, C. J. Neth. J. Res. 1970, 4 395-468. (I3) A.; Leitzky, T.A. Limnoi. OCeMOgr 1975, 20,497-510. (14) Beck, H,L.; Krey, w. Scieme 1983, 220, 18-24. (15) sche1l, W. R, ~ ~~ ~ ~ ~ c t 1917,41, a 1019-31. (16) Ulrich, B. In Effeets ofAeeumulntion of
~
~h
A
Air Pollurmrs in Forest Ecos~stems;Ulrich.
P; Pankrath, I., Eds.; Reidel Publlishing: Dordrecht. the Netherlands, 1983; pp. 3345. (17) Meyer. R. In Eff‘ers of Accumulation of Air Pollutants in Forest Ecosystems: Ulrich. P; Pankrath. J.. Eds.: Reidel Publishing: Dordrecht, the Nelherlands, 1983; pp. 47..
)ostcomplete listing of bge chemistry faculties in Y.S. and Canada
OLLEGE ’HEMISTRY :ACULTIES
33.
(18) P w t . S. E.: Moore. H. E.; Martell. E. A. J . Geophys. Res. 1974, 77. 6515-20.
(19) Nevissi. A.: Beck. J. N.: Kuroda. P K. keolrh Phis. 1$74,27. 181-88. (20) Battarbee, R. W. et al. Arch. Hydrobiol. 1980, 89.440-48. (21) Mankinen. G . U.; Korpijaakko, E.; Shncyer, W. A. “State of New York Peat Resource Invenfory,” ERDA Report 82-25, Ncu York Stale Encrgy Research and Dcvclopmrnt Authorit). Jut) 1982, V d I . 122, . . Rremner. 1. M : S l e e k C G Adr M,crobiol. E d . 1978,Z. 155-201. (23) Eaton. I. S . ; Likens. G. E.: Borman. F. H. In Effecrs of Acid Roin on Terrestrial Ecosysremr: Hutchinson. T C.; Hauas, M.. Eds.; Plenum: New York. 1978: pp. 154-62. (24) DeWalle. D. R. et al. “Causes of Acidification of Our Streams an Laurel Hill in Southwestern Pennsylvania.” final report to the Bureau of Reclamation. Department of the Interior, Washington, D.C.; Project B117-PA. Institute for Research on Land and Water Resources. Pennsylvania State University, University Park, Pa.. 1982. (25) Darnrnan, A.W.H. Oikos 1978.30, 48095. (26) Rabbins. 1. A. In 7he Biogmchemirtry of Lead in rhe Environment: Nriagu, J. 0.. Ed.: Elsevier: the Netherlands. 1978: Part A, pp. 285-93. (27) Schell. W. R.: Barnes, R. S. In Handbook of Environmental Isotope Geochemcsrry: Fontes. J. C.: Fritz. P. Eds.: Elsevier: the Netherlands. ‘in press; Vol. B.’ (28) Shirahata. H.; Elias. R. W.; Patterson, C. C. Geochim. Cormochim. AGIO 1980, 44, 149-62. (29) Kahl, I. S.; Norton, S. A,; Williams. I. S. In Geological Aspect$ ofacid Deposition: Bricker. 0. P, Ed.; Acid Precipitation Series, Butlerworth. Boston, 1984 Vol. 7 , pp. 23-25. (30) Rahn, K. A. “The Chemical Composition of the Atmospheric Aerosol.’’ technical report. Graduate School of Oceanography. University of Rhode Island: Kingston, R.I., 1976. (31) Rahn. K. Science 1984,223. 132-39. (32) Rahn, K. A,; Lowenthal. D. H. Science 1985.228, 275-84. (33) Schell. W. R.: Sanchez, A. L.:Granlund. C. Air, Soil and Waur Pollut., in press.
I
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WiUinm R. Schell is a profcmor in the University of Pitrrhurgh S department of radiation health in rhe Graduate School of Public Health. He has a B. S.in chemistryfrom Oregon Stare University. an M.S. in agricultural chemistry from the Universiry a~ Idaho, and a Ph.D. in nuclear and inorganic chemistry from the University oj Washington. Schell is a member of a number of professional societies including ACS, AAAS, and the New York Academy oj Sciences.
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