118 Organic compounds in soils, sediments & sludges
organic mercury compounds reacted with the clay Miscelle in soil to form an intermediate which subsequently gave a dialkylmercury or diphenylmercury and a mercury-clay
compound. Based on the hypothesis, the dialkylmercury compounds would escape
into the atmosphere while diphenylmercury compounds would escape into the atmosphere while diphenylmercury would accumulate in the soil. Metallic mercury would
result from the further degradation of the mercury-clay compound. However, repeated
attempts to detect the disubstituted organic mercury compounds formed in soil through
degradation failed, indicating that decomposition was not by Booer’s mechanism.
Work has also been done on the absorption and inactivation of organomercurials
by micro-organisms that tolerate and even thrive on mercurials [35, 36]. It has been
postulated that inactivation occurred by the uptake of fungicide by micro-organisms,
followed by metabolic breakdown and by possible utilisation of portions of the
by-products. However, whether or not biological inactivation and mercury evolution
occur together has not been determined.
Spectrophotometric methods
Kimura and Miller et al [37–39] have also studied the decomposition of organic fungicides in soil to mercury vapour and to methyl-or ethylmercury compounds and devised
methods for the determination of these compounds in the vapours liberated from the
soil sample. The mixed vapours of mercury and organomercury compounds is passed
successfully through bubbles containing a carbonate-phosphate solution to absorb
organic mercury and through an acidic potassium permanganate solution to absorb
inorganic mercury vapour. In both cases the mercury in the scrubber solution is determined photometrically at 605 nm with dithizone. The method is capable of determining
10 µg or more of organic mercury/1000 L air in the presence of mercury vapour.
Kimura and Miller et al [38] have described a procedure for the determination of
organomercury (methylmercury, ethylmercury and phenylmercury compounds) and
inorganic mercury in soil. In this method the sample is digested in a steam bath with
sulphuric acid (0.9M) containing hydroxyl ammonium sulphate, sodium chloride and,
if high concentrations of organic matter are present, potassium dichromomate solution.
Then, 50% hydrogen peroxide in added. Finally, when decomposition is complete
excess potassium permanganate is added.
Air is swept through the solution to remove elemental mercury which is determined
spectrophotometrically qt 605 nm using dithizone.
Kimura and Miller et al [38] demonstrated that mercury in several organic forms
can be digested then aerated from unfiltered soil digests. For samples of 10 g of soil
cores containing 5 µg mercury or less, the standard deviations of a single determination
were 0.12, 0.15 and 0.23 µg, respectively, using 2 cm cylindrical optical cells.
Kimura and Miller et al [39] also described the following methods for the determination in soil samples, of extractable organic mercury, total mercury and extractable
ionic mercury.
Phenyl and alkylmercury compounds are extracted from about 1g soil by shaking
for 2 hours with 0.1M phosphate pH8 buffer containing 6 mg thiomalic acid, added
just prior to use, and analysed after acidification with 9M hydrochloric acid containing
hydroxylammonium chloride. The final determination is made by the dithizone mircroprocedure of Polley and Miller et al [40]. Diphenyl- or dialkylmercury compounds
organic mercury compounds reacted with the clay Miscelle in soil to form an intermediate which subsequently gave a dialkylmercury or diphenylmercury and a mercury-clay
compound. Based on the hypothesis, the dialkylmercury compounds would escape
into the atmosphere while diphenylmercury compounds would escape into the atmosphere while diphenylmercury would accumulate in the soil. Metallic mercury would
result from the further degradation of the mercury-clay compound. However, repeated
attempts to detect the disubstituted organic mercury compounds formed in soil through
degradation failed, indicating that decomposition was not by Booer’s mechanism.
Work has also been done on the absorption and inactivation of organomercurials
by micro-organisms that tolerate and even thrive on mercurials [35, 36]. It has been
postulated that inactivation occurred by the uptake of fungicide by micro-organisms,
followed by metabolic breakdown and by possible utilisation of portions of the
by-products. However, whether or not biological inactivation and mercury evolution
occur together has not been determined.
Spectrophotometric methods
Kimura and Miller et al [37–39] have also studied the decomposition of organic fungicides in soil to mercury vapour and to methyl-or ethylmercury compounds and devised
methods for the determination of these compounds in the vapours liberated from the
soil sample. The mixed vapours of mercury and organomercury compounds is passed
successfully through bubbles containing a carbonate-phosphate solution to absorb
organic mercury and through an acidic potassium permanganate solution to absorb
inorganic mercury vapour. In both cases the mercury in the scrubber solution is determined photometrically at 605 nm with dithizone. The method is capable of determining
10 µg or more of organic mercury/1000 L air in the presence of mercury vapour.
Kimura and Miller et al [38] have described a procedure for the determination of
organomercury (methylmercury, ethylmercury and phenylmercury compounds) and
inorganic mercury in soil. In this method the sample is digested in a steam bath with
sulphuric acid (0.9M) containing hydroxyl ammonium sulphate, sodium chloride and,
if high concentrations of organic matter are present, potassium dichromomate solution.
Then, 50% hydrogen peroxide in added. Finally, when decomposition is complete
excess potassium permanganate is added.
Air is swept through the solution to remove elemental mercury which is determined
spectrophotometrically qt 605 nm using dithizone.
Kimura and Miller et al [38] demonstrated that mercury in several organic forms
can be digested then aerated from unfiltered soil digests. For samples of 10 g of soil
cores containing 5 µg mercury or less, the standard deviations of a single determination
were 0.12, 0.15 and 0.23 µg, respectively, using 2 cm cylindrical optical cells.
Kimura and Miller et al [39] also described the following methods for the determination in soil samples, of extractable organic mercury, total mercury and extractable
ionic mercury.
Phenyl and alkylmercury compounds are extracted from about 1g soil by shaking
for 2 hours with 0.1M phosphate pH8 buffer containing 6 mg thiomalic acid, added
just prior to use, and analysed after acidification with 9M hydrochloric acid containing
hydroxylammonium chloride. The final determination is made by the dithizone mircroprocedure of Polley and Miller et al [40]. Diphenyl- or dialkylmercury compounds