Enclosure (1) TO COMDTINST 16478.12
At most locations there was no indication that AtoN batteries in elevated
levels of mercury in the sediment. Tampa Bay, where there were many batteries
and a high percentage of broken cases, was an exception.
The measurement of metal in sediments in Chesapeake Bay, Tennessee River, and
Puget Sound showed no correlation with proximity to batteries or lighted
AtoNs. In the Chesapeake Bay the measured mercury concentrations correlated
well with physical characteristics of the sediment, particularly organic
carbon in the sediment. This is a common phenomena in certain estuaries were
the small size particles associated with high organic levels have large
surface areas and thus more metal can adhere to the surface of the particles.
In the Chesapeake Bay the relationship with sediment type was the same whether
or not batteries were present. Neither the number of batteries found, the
proximity of sediments to batteries, nor proximity of sediments to lighted
AtoNs was found to affect sediment mercury concentrations in the Chesapeake
Bay Prototype investigation. The mercury concentrations in sediments around
AtoNs in the bay, were well within the range of reference concentrations
reported in the literature for the portion of the bay investigated. Similarly
the concentrations at lighted AtoNs was similar to or below the concentrations
measured at unlighted (and thus no batteries present) AtoNs during the
prototype investigation.
In the Tennessee River investigation elevated mercury concentrations were
found but associated with sources other than AtoN batteries in the
subwatersheds of the river. Samples collected within 20 meters of AtoNs,
revealed similar sediment concentrations regardless of proximity to batteries.
Statistical as well as subjective evaluation of the date revealed no
differences in concentrations between samples close to batteries (generally
within 10 meters of the AtoN) and samples beyond the area where batteries were
found. Except where a munitions manufacturing facility in the subwatershed
was a documented source of mercury, measured concentrations at lighted AtoNs
was within the range reported in the literature at unaffected areas and
measured at unlighted AtoNs. Where elevated mercury levels were found,
samples located 20 meters or more from batteries had similar concentrations to
samples adjacent to battery piles.
There is a relatively extensive body of information of background or reference
area mercury concentrations in Puget Sound sediments. There has even been a
background range established for unaffected areas of Budd Inlet, which is the
inlet where the Puget Sound AtoN Prototype investigation was conducted. All
of the samples collected at AtoNs, both lighted and unlighted had very similar
concentrations and were within the established background range for Budd Inlet
and Puget Sound. Samples were collected within an adjacent to battery piles
and at increasing differences from the concentrations of batteries. Both
statistical tests and qualitative
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