Trace metals in sediments from the inner continental ... - Springer Link

Trace Metals in Sediments from the Inner Continental Shelf of the Western Beaufort Sea ERIC A. CREOELIUS Battelle Pacific Northwest Laboratories 439 West Sequim Bay Road Sequim, Washington 98382, U.S.A. JOHN H. TREFRY Department of Oceanography & Ocean Engineering Florida Institute of Technology Melbourne, Florida 32901, U.S.A. MARGARETE S. STEINHAUER Battelle Ocean Sciences 397 Washington Street Duxbury, Massachusetts 02332, U.S.A. PAUL D. BOEHM Arthur D. Little, Inc. 25 Acorn Park Cambridge, Massachusetts 02140, U.S.A.

ABSTRACT / Increased development and changing climate have enhanced global interest in the Arctic Ocean and adjacent seas. Using a large, 3-yr data base, we have determined the distribution of trace metals in sediments from the inner shelf of the western Beaufort Sea. Metal concentrations in these sediments reflect pristine conditions, consistent with those for most coastal areas in the Arctic and with predictions based on average continental crust. Geographic variations in metal values are primarily related to sediment grainsize distribution. However, grain-size patterns are a complex function of several variables including source areas, ice and water movement, as well as physical and chemical weathering. Future identification of any metal contamination in Beaufort Sea sediments will be simplified by understanding the predictable natural patterns.

Introduction

ronmental Assessment Program (OCSEAP) (Barnes and others 1984). Present efforts in the Beaufort Sea continue to expand the data base as well as our perspective of the overall system. In addition to greatly expanding the available data base, a study of sediment trace metals in the Beaufort Sea provides an opportunity to define metal concentrations in pristine coastal sediments and to investigate the role of physical and chemical weathering on the geochemistry of sediments at high latitudes. In the Arctic, there are generally fewer soil-forming processes and minimal chemical weathering. Even physical weathering can be limited by the time available for freshly eroded rock to be altered before it enters the sea. Sharma (1979) notes that more weathering occurs on the continental shelf than on land in the Arctic. In this paper, we combine the roles of grain size, organic matter content, and weathering to explain metal concentrations and distributions in sediments from the inner shelf of the Beaufort Sea.

The Arctic Ocean and adjacent seas, including the Beaufort Sea, have only recently been recognized as important components of the global hydrologic and geochemical cycles (Rey 1982; Edmond 1988). However, even as we learn to appreciate the global role of high-latitude processes, they may be changing. Industrial development along the Arctic shelf, especially in the Beaufort Sea, has grown continuously since the 1960s. In addition, present-day global warming trends could be most amplified in the Arctic (Lamb 1982). Thus, it is imperative that we enrich our scientific data base for the Arctic with an eye toward future changes. T h e work described here augments our knowledge of trace metal geochemistry and background metal concentrations in Beaufort Sea sediments. A surprisingly large number of studies have been carried out in the Beaufort Sea during the past 100 years. A summary of earlier work is given by Norton and Weller (1984). The first comprehensive study of the sediments was carried out during the Beaufort Sea Scientific Expedition of 1950-1951, supported by the U.S. Navy (Carsola 1954). A sizable effort on water and ice movement, sediment distribution, and geophysics preceded the discovery of oil beneath the Alaskan coast in 1968 (Reed and Sater 1974). During the 1970s and 1980s, a variety of research activities on oil-related impacts to the environment have been part of such programs as the Outer Continental Shelf EnviEnvironGeol Water Sci Vol. 18, No. 1, 71-79

Study Area

Our study area encompasses the inner continental shelf (water depths