container. The measurements for Pb, Cu, and Cd were made by injecting 20 wuL 
of the final solution into a graphite-furnace AA spectrophotometer. 
Manganese and zinc 
The measurements for Mn were made by ICP spectrometry with a solution 
made by diluting 2 mL of stock solution B to 4 mL with H90- Zinc was measured 
by flame AA directly from stock solution B. 
Mercury 
Mercury concentration was determined on a separate portion of the 
sample. Two hundred milligrams of sediment (100 mg if sample concentrations 
were expected to be >50 ppb) were decomposed in a l-oz teflon screw-top vial 
with 2 mL of concentrated HNO3 (J. T. Baker Chemical Co.) and 2 mL of HC10, 
(G. Frederick Smith Chemical Co. (GFS) double distilled from Vycor, a pure 
silica glass). The mixture was heated in a capped vial until the solution 
reached 200°C. The solution was then heated with the cap off for about 
45 minutes, after which the samples were removed from the heat_ source. 
Immediately, 1 mL of concentrated HNO3 was added; the vial was filled with H)0 
and capped tightly until used. The sample solution then was added to a flask 
containing 125 mL of Hj0 and 4 mL of 10-percent (weight:volume) SnClj in 7A 
percent HCl. Nitrogen was passed through the solution to remove elemental Hg, 
which was collected on gold foil located in the center of the coils of an 
induction furnace. Activation of the furnace released the Hg, which was 
measured by a cold-vapor AA technique. Blanks, standard rocks, and internal 
sediment standards were analyzed for each set of samples. A series of 
solutions was prepared that had the same Hg- concentration range expected in 
the samples. 
The concentrations of Hg in bottom sediments determined during the first 
year of the monitoring program were typically less than the detection limit of 
U5) 
