Enclosure (1) TO COMDTINST 16478.12
Chesapeake Bay), all of the detected mercury was particulate, and none of it
had dissolved. Even if mercury from batteries does dissolve into the water
column, the constant flushing, dilution, and dispersion, which is associated
with tidal, riverine, and large lake systems where AtoNs are most commonly
located, would diminish concentrations significantly below those of concern.
These findings strongly support the conclusion that mercury from AtoN
batteries is much more of a concern when in the sediments than in the water
column. If there is not a very strong and extensive indication of hazard in
the sediments, there is no reason to consider pathways associated with the
water column at most AtoN locations. For this reason, the prototype
investigations focused on sediments, and future consideration of
potentialhazards associated with AtoNs should generally be directed at
sediments.
Fate and Availability of Mercury
Most of the mercury from batteries discarded in the vicinity of AtoNs does not
enter a human health or environmental exposure pathway.
If the casings of the discarded batteries were broken, the liquid contents was
released immediately. In those cases, the dissolved ionic and methylated
forms were quickly diluted and transported away from the AtoN. The elemental
forms remaining on the electrodes, or other forms associated with the
batteries, dissolved very slowly and were then rapidly diluted and dispersed
away from the AtoN. Some of the dissolved form of mercury was most likely
scavenged by particles, some of which were deposited in the immediate vicinity
of the battery. Similarly some of the soluble mercury was converted and
settled, some in the immediate vicinity of the batteries. Some of the
particulate material associated with the batteries was likely deposited close
to the AtoN, and the mercury adsorbed to the particles deposited in the
sediment.
When primary batteries were discarded near the AtoN and not broken, a similar
process has taken place, only over a longer time frame. In some cases, such
as seen in the Tennessee River, the mercury is released very slowly, probably
over several decades. In such cases, the dilution and dispersion during the
release period results in such low concentrations that the presence of
mercury, or ingestion by organisms (if any), cannot be detected above the
natural variation. In areas such as Tampa Bay, the mercury was probably
released over years, rather than decades, as the cases deteriorates and storms
damage the batteries. In such cases, the releases may sometimes be detected.
The mercury which was released into the water column, either initially in the
dissolved form from broken batteries or over time in other forms, entered the
aquatic pool of mercury which undergoes extensive cycling and transformation.
The mercury in this pool can enter exposure pathways through ingestion by
aquatic organisms and vaporization. However, even on a very local scale the
mercury from AtoN batteries is
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