RC - What is RC? - Rotterdam Convention

a
particulate matter.
Considering the vapour pressure of the compound, i.e. 20 Pa at
20 °C (McConnell et al., 1975), transfer across soil-air
boundaries may be significant. Depending on the soil type,
adsorption will hinder this transport (see below). In a field study
in the ex-USSR, concentrations of hexachlorobutadiene in air above
vineyard were found to be 0.08 and 0.003 mg/m 3 at 1 day and 3
months, respectively, following a spring application of 250 kg/ha.
The method of analysis was not reported. Volatilization of the
compound from light soils was more rapid than from heavy soils
(Litvinov & Gorenshtein, 1982).
The Henry coefficient of hexachlorobutadiene is 0.43 (1040
Pa.m 3 .mol -1 ) at 25 °C (Shen, 1982) and 0.3 at 22 °C Hellmann,
1987a). These values are comparable to those of other chlorinated
aliphatic alkenes. They indicate possible transfer of the compound
across water-air boundaries leading to a wide distribution, with
aerial transport playing a major role (McConnell et al., 1975). In
a model experiment, hexachlorobutadiene was allowed to evaporate
from a 20-mg/litre aqueous-methanolic solution, containing 10%
methanol, in a porcelain basin with slow magnetic stirring at 22 °C.
UV spectrophotometry recorded a 25% loss within 28 min. It was
shown
that methanol decreased the disappearance time. For the transfer of
this and other model results to flowing waters, a reduction factor
of 30 was proposed for the rate of evaporation on the basis of
limited data for two compounds (Hellmann, 1987a).
2
In a model experiment, UV spectrophotometric analysis of
solutions of hexachlorobutadiene in deionized water to which
1 g/litre of clay mineral (Fuller's earth) was added revealed a
clay-water partition coefficient of 500 litre/kg, showing limited
adsorption to pure clay minerals comparable to that of other
chlorinated alkenes (Hellmann, 1987b). Based on the log
octanol-water partition coefficient (log Kow) of 4.78-4.90
(Table 1), hexa-chlorobutadiene is expected to adsorb strongly to
organic matter. The organic carbon-water partition coefficient
(Koc) can be estimated to be 25 120 litre/kg on the basis of a log
Kow of 4.8 using the semi-empirical equation of Karickhoff (1981).
Oliver & Charlton (1984) determined a Koc value of 158 500
litre/kg on the basis of sediment and water concentrations in the
Niagara River, USA. Partition coefficients of approximately
200-260 litre/kg were found for two unspecified types of soil in
model experiments employing gas chromatographic analysis of
solutions of hexa-chlorobutadiene in water (Leeuwangh et al.,
1975; Laseter et al., 1976). In field experiments conducted along
the Mississippi river in the USA in 1974-1975, some water samples
were found to contain 1.0-1.5 µg/litre, whereas levee soil samples
at the same sites contained 62-1001 µg/kg dry weight. At a more
polluted site near a Hex-waste landfill, water samples contained
0.04-4.6 µg/litre and mud samples 270-2370 µg/kg dry weight. These
studies show that soil-water partition coefficients can range over
to 4 orders of magnitude assuming equilibrium (Laseter et al.,