Biomedical Engineering Reference
In-Depth Information
TABLE 2.2 Reported Half-Lives of Methanol and Benzene in the
Environment
Methanol
Half-Life (Days)
Benzene
Half-Life (Days)
Environmental Medium
Soil (based on unacclimated grab
sample of aerobic/water suspension
from groundwater aquifers)
1-7
5-16
Air (based on photooxidation
half-life)
3-30
2-21
Surface water (based on unacclimated
aqueous aerobic biodegradation)
1-7
5-16
Groundwater (based on unacclimated
grab sample of aerobic/water
suspension from groundwater aquifers)
1-7
10-720
Source: Adapted from Howard et al. (1991).
Once released into surface waters or the subsurface environment,
the fate of methanol depends on numerous environmental factors
including: the nature and quantity of the release and physical, chemi-
cal, and biological characteristics of the impacted media. Various
reports summarize estimates of possible methanol half-lives (the time
required for a 50% reduction in concentration) (Table 2.2) in various
environmental media. In the atmosphere, methanol would be photo-
oxidized relatively quickly; its reported half-life ranges between 3 and
30 days. In soil or groundwater, rapid biodegradation is expected as
well, with reported half-lives ranging from 1 to 7 days. Finally, in
surface water following a pure methanol spill, methanol would also be
expected to diminish quickly; reported half-lives are between 1 and
7 days as well. In Table 2.2, reported methanol half-lives are compared
to those of benzene to illustrate the relatively rapid degradation of
methanol.
On the basis of data summarized in Table 2.2, for the plausible
release scenarios envisioned, methanol appears unlikely to accumulate
in the soil, air, surface water, or groundwater. However, it is unclear
whether these reported rates were developed under realistic field
conditions or adjusted based on field experience. Consequently, these
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