TRACE-METAL ANALYSIS PROCEDURES 
The analyses of trace metals in marine sediments were carried out by the 
U.S. Geological Survey Branch of Analytical Laboratories, Reston, Va. 
Concentrations of the following elements were determined: aluminum (Al), 
barium (Ba), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), 
Manganese (Mn), mercury (Hg), nickel (Ni), vanadium (V), and zinc (Zn). 
Analyses were carried out by the U.S. Geological Survey Branch of Analytical 
Laboratories, Reston, Va. The various procedures employed in each of the 
analyses are detailed below and summarized in table l. 
Preparation of stock solution A 
Exactly 0.5 g of ground bulk sediment or 0.2 g of the fine fraction was 
added to a covered teflon beaker and digested overnight with 5 mL of HC10,; 5 
mL of HNO3, and 13 mL of HF at approximately 140°C. The covers were removed 
and the temperature was increased to between 180° and 190°C, first producing 
fumes of HClO, and then evaporating the solution to dryness. The residue was 
dissolved and diluted to exactly 25 mL with 8N HCl. This solution is 
referred to as stock solution A. 
Two blanks containing all reagents were analyzed along with samples. All 
reagents were analyzed for contaminants prior to use, as is always 
necessary. The Canadian reference sediment standard MESS-l was analyzed in 
each set of samples. A series of solutions was prepared that approximated the 
concentration levels expected in the samples; this series was used as the 
standard in calibrating the inductively coupled plasma (ICP) spectrometer and 
atomic absorption (AA) spectrophotometer. 
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