ISSN:
1432-0703
Source:
Springer Online Journal Archives 1860-2000
Topics:
Energy, Environment Protection, Nuclear Power Engineering
,
Medicine
Notes:
Abstract Mercaptopyridine-N-oxide biocides in dilute aqueous solution underwent rapid reductions in toxicity on exposure to sunlight, according to bioassays with marine algae and bacteria. After 5 to 10 h exposure at 100 ppm of the parent compound, a tertiary butylamine derivative or the disulfide dimer, ten-fold increases in bioassay concentrations were necessary to equal the toxicities of the unirradiated solutions. Ultraviolet spectral measurements indicated that pyridine-N-oxide 2-sulfonic acid was an early photolytic intermediate. This compound and other possible photo-products were much less toxic than the original biocides and were also susceptible to further light-induced degradation and toxicity loss. Another photodegradation pathway led to an insoluble product. Estimates of early photolysis rates from ultraviolet spectral measurements indicated that temperature, pH, and salinity, within normal environmental limits, were not important variables. Wavelengths of 320–355 nm were effective in producing photodegradation, and exposure under 24 cm of seawater had no effect on the photodegradation rate. In the absence of oxygen, toxicity loss rates of sunlight-exposed biocides were less than one-tenth of those in oxygenated water. In aqueous solutions, biocides exposed to air in the dark underwent relatively slow oxidative changes. The mercaptopyridine-N-oxide class of biocides has a potential use in controlling microbial growth in the dark for long periods and then degrading rapidly to non-toxic products when discharged into sunlit natural waters. Prevention of microbial contamination in shipboard fuel storage tanks may be a possible application for these compounds.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01056251
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