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EC number: 200-756-3
CAS number: 71-55-6
Concentrations of volatile
organic compounds in mesocosms showed seasonably variable declines which
were generally considered the exponential although some compounds showed
seasonal breaks associated with increased volatilisation. Compounds
showing biodegradation generally disappeared much faster as temperatures
rose. The results of the study showed that for chlorinated C2
hydrocarbons the main removal process is by volatilisation. This is
demonstrated in the paper by the comparable release rates recorded for
F-12 (which is not subject to biodegradation or absorption onto
particulate matter) and materials in this group. The author's attribute
the higher release rates in the winter period to the effect of bad
weather increasing surface water movement whereas losses during the
summer period can be attributed to increased temperatures. The authors
consider that as surface movement in the mesocosm tanks will be
appreciably less than that in the open estuary their estimates of losses
may be appreciably less than is the case in practice. These results are
at variance with those recorded in the laboratory studies where the
effects of water movement are not fully taken into account. The results
are shown in tables below.
8 - 16 C (spring)
20 - 22C (summer)
3 – 7C (winter)
= concentration (mg/L)
in the mesocosm measured by analysis after stripping at the start of the
= removed rate constant (l)
= DT50 (days) were volatilisation appears to dominate.
– dichlorodifluoromethane (Freon) - internal standard to confirm closed
loop stripping procedure (confirmation of recovery).
results with non poisoned mesocosms 20 - 22C (summer)
Tank with HgCl2
Tank without HgCl2
* not possible to calculate.
Results of the study showed that
1,1,1-trichloroethane DT50 in marine estuaries is in the region of 24
days (spring), 11 days (winter) and 9.6 - 12 days in summer.
Although the study was conducted
between 1980 - 1983 it is designed to take into account all possible
components of removal of organic pollutants from the estuarine
environment. As this is a Tier 3 study the results obtained include all
possible interactions (volatility, absorption/adsorption, biodegradation
etc) that contribute to the removal of these materials from the aquatic
environment. For risk assessment purposes this study should be used in
preference to laboratory studies where interactions between the various
components of removal are not adequately addressed.
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