Environ. Sci. Technol. 1986, 20, 299-302 (5) Payne, J. R.; Kirstein, B. E.; McNabb, G. D.; Lambach, J. L.; de Oliveira, C.; Jordan, R. E.; Hom, W. In “Proceedings of the 1983 Oil Spill Conference”; API, Washington, DC, 1983; pp 423-434. (6) Green, W. J.; Frank, H. S. J . Solution Chem. 1979, 8, 187-196. (7) Leinonen, P. J.; Mackay, D. Can. J . Chem. Eng. 1973,51, 230-233. (8) Burris, D. R.; MacIntyre, W. G. Environ. Toricol. Chem. 1985,4, 371-377. (9) Burris, D. R.; MacIntyre, W. G. In ”Oil and Freshwater”; Vandermeulen, J. H., Ed.; Pergamon: Toronto, in press.
Banerjee, S. Environ. Sci. Technol. 1984, 18, 587-591. Fredenslund, A.; Gmehling, J.; Rasmussen, P. “VaporLiquid Equilibria Using UNIFAC, A Group-Contribution Method”; Elsevier Scientific: Amsterdam, 1977. Welty, J. R.; Wicks, C. E.; Wilson, R. E. “Fundamentals of Momentum, Heat and Mass Transfer”;Wiley: New York, 1984.
Received for reveiw July 17,1985. Accepted October 24,1985. This work was supported by a grant (AFOSR-83-0036)from the U.S. Air Force Office of Scientific Research.
NOTES Diagenetic Trace-Metal Profiles in Arctic Lake Sediments Jeffrey C. Cornwell” Institute of Marine Science, University of Alaska, Fairbanks, Alaska 9970 1
rn Heterogeneous trace-metal profiles have been found in the slowly accumulating sediments of Toolik Lake, AK. Elevated Ba, Co, Cu, Mo, and Ni concentrations near the sediment-water interface are inconsistent with inputs from recent watershed disturbances. The apparent cause of trace-metal enrichment is comigration with Mn and Fe in pore water resulting in narrow bands of trace-metal enrichment associated with high (>15%) concentrations of Mn and Fe. The misinterpretation of diagenetic enrichments as anthropogenic features is a potential problem in mildly reducing, Mn- and Fe-rich lake sediments.
Introduction The surfaces of hydrous Mn and Fe oxides are important sites for the removal of trace metals from natural waters (1-3). Selective extraction techniques show that trace metals on suspended particulates and in sediments are often associated with metal oxide phases (4-6). In Toolik Lake, AK, postdepositional migration of Mn and Fe within sediment results in Mn- and Fe-rich horizons (7). These arise from the reduction of Mn and Fe oxides, upward diffusion of Mn2+ and Fe2+,and precipitation of oxides closer to the sediment-water interface (8-10). The purpose of this study is to examine the effect of Mn and Fe migration on the distribution of trace metals (Ba, Co, Cu, Ni, and Zn) commonly found associated with lacustrine ferromanganese deposits ( 4 , 5). I will demonstrate that postdepositionalchemical reaction can result in trace-metal distributions that are similar to those influenced by anthropogenic inputs. Toolik Lake is a 1.5 km2,multibasin kettle lake formed 12 000 years ago in the northern foothills of the Brooks Range, AK. Disturbances to the 65 km2 watershed, including the construction of the Dalton Highway and the trans-Alaska oil pipeline, commenced in the early 1970s. The fine-grained sediment is dominated by the presence *To whom correspondence should be addressed at the Department of Oceanography,Texas A&M University, College Station, TX 77843.
0013-936X/86/0920-0299$01.50/0
of high concentrations (>15%) of Mn and Fe in narrow horizons. The diagenetic formation of the Mn- and Fe-rich layers occurs in Toolik Lake because of (1)large inputs of Mn and Fe relative to other sediment components (7), (2) low sediment accumulation rates (11), and (3) the moderately reducing sediment conditions arising from low rates of organic matter input to the sediment (12).
Methods The cores presented in this study, B and C, were obtained in 1980 from 5.5- and 8.0-m water depths respectively, using a KB corer modified to hold a 6.6 cm (inner diameter) plastic core liner. Undisturbed cores resulted from slowly lowering, not dropping, the corer into the sediment. Additional cores for pore water and solid-phase analysis of major sediment components were collected at each site (7). The cores were extruded, and 1.0-cm sections were frozen in plastic bags. The water content was determined by drying a t 65 “C, and a ceramic mortar and pestle was used for homogenization. Dried, ground sediment samples (0.25 g) were digested at 70 O C with 2.0 mL of concentrated HN03 and 4.0 mL of concentrated HCl until dryness (13). After addition of 10.0 mL of 1.5 N HC1, the mixture was briefly heated and the solution removed by pipetting. Cu, Ni, Zn, Co, and Ba were ’analyzed by atomic absorption spectrometry (AAS) with blanks carried throughout the entire procedure. Lead was not analyzed because of very low (
