Enclosure (1) TO COMDTINST 16478.12
A conservative assumption is that all of this mercury is released into the
environment in one year. To enter the food chain, the mercury must first be
converted to Hg(+).It may also be conservatively assumed that all of this
mercury is somehow oxidized to Hg(+).The earth itself, through volcanoes and
along continental subduction zones, releases about 1,600 tons of mercury into
the atmosphere each year. All of this mercury is Hg(+).This material falls to
earth constantly as acid rain. Morel and Mason estimated that as much mercury
falls as acid rain on a 40-meter diameter circle around each AtoN as is
released from the complete disintegration of ten batteries.
In addition to the mercury released by environmental sources, humans release
1,300 tons of mercury per year through waste incineration and 2,600 tons per
year through burning of fossil fuels. Relative to these inputs, the mercury
released form an AtoN battery into the rivers or the oceans is minuscule. The
only significant measurable mercury pathway to humans from AtoNs would start
with acute methylation and ingestion of mercury by biota living near the AtoN.
Site Characterizations
Drs. Morel and Mason suggested site characterizations for this potential
pathway. They conjectured that any Hg(0) released might stay in the
surrounding sediment and migrate into deeper layers over time, forming "hot
spots". Such hot spots may also be formed by Hg(0) that is bonded to fragments
from broken batteries. Benthic organisms living in these hot spots may
accumulate mercury and pass it up the food chain. Based on the conclusions of
this study, the Volpe center designed in-situ characterizations in battery
fields to determine (1) whether elemental mercury indeed remained at the
location after battery disposal and (2) whether any organic forms of mercury
were evident.
Some environmental factors are likely to affect the behavior of elemental
mercury, in turn affecting the conclusions drawn from the Morel and Mason
study. These are factors that influence (1) whether batteries break, (2)
whether elemental mercury is exposed to an organic material that promotes
methylation, and (3) whether elemental mercury is exposed to a fresh water
environment also promoting methylation. These factors were all considered in
the development of a field sampling plan to confirm the results of the Morel
and Mason study.
Conclusions
The general conclusions from this portion of the analysis were:
The mercury in AtoN batteries is a minute fraction of the total mercury in
the environment.
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