nitrophenols and pentaerythritol

An international ring test involving 14 laboratories was organized on behalf of the Commission of the European Economic Communities (EEC) with the purpose of evaluating two proposed screening methods for assessment of biodegradability in seawater: (a) a shake flask die-away test based primarily on analysis of dissolved organic carbon and (b) a closed bottle test based on determination of dissolved oxygen. Both tests are performed with nutrient-enriched natural seawater as the test medium and with no inoculum added other than the natural seawater microflora. The test methods are seawater versions of the modified OECD screening test and the closed bottle test, respectively, adopted by the Organization for Economic Cooperation and Development (OECD) and by the EEC as tests for "ready biodegradability." The following five chemicals were examined: sodium benzoate, aniline, diethylene glycol, pentaerythritol, and 4-nitrophenol. Sodium benzoate and aniline, which are known to be generally readily biodegradable consistently degraded in practically all tests, thus demonstrating the technical feasibility of the methods. Like in previous ring tests with freshwater screening methods variable results were obtained with the other three compounds, which is believed primarily to be due to site-specific differences between the microflora of the different seawater samples used and to some extent also to differences in the applied concentrations of test material. A positive result with the screening methods indicates that the test substance will most likely degrade relatively rapidly in seawater from the site of collection, while a negative test result does not preclude biodegradability under environmental conditions where the concentrations of chemicals are much lower than the concentrations applied for analytical reasons in screening tests. Nevertheless, the screening tests are considered useful and cost-effective tools for an initial assessment of biodegradability in marine environments.

Topics: Aniline Compounds; Benzoates; Benzoic Acid; Biodegradation, Environmental; Ethylene Glycols; Nitrophenols; Propylene Glycols; Reference Standards; Seawater; Water Pollutants, Chemical

A comparative study has been performed on test methods for assessing the biodegradability of chemicals in seawater environments. A simple shake flask die-away test with natural seawater and 14C-labeled chemicals added in microgram/liter concentrations is proposed as a "simulation" test. The analytical parameter used in this test is residual dissolved 14C activity. The performance of the simulation test has been compared with the performance of similar screening tests with dissolved organic carbon analysis and test compounds added in mg/liter concentrations to nutrient-enriched seawater. All chemicals investigated that passed the screening tests were also degradable in the simulation test and some results with simulation tests were positive; even screening tests were negative, while some compounds, including maleinhydrazide, known to be degradable in soil, remained undegraded in either type of test. Disappearance times after the ended lag time were smaller in screening tests than in simulation tests, but the rates of biodegradation cannot be meaningfully compared, as zero-order kinetics in combination with an exponentially growing population of degraders prevail in screening tests, while first-order kinetics and frequently a constant activity of degraders (cooxidation) prevail in simulation tests where the test material is a secondary substrate only. In screening tests, lag times are sometimes excessively long and highly variable. Whether the lag times could be decreased and their variability narrowed by supplementation with a cosubstrate (yeast extract) or by inoculation with seawater that had been preadapted to the test material was investigated. In most experiments such test modifications had no significant effect but in one experiment with 4-nitrophenol, inoculation with 1% preadapted seawater decreased the lag phase from greater than 35 to 9 days.

Topics: Aniline Compounds; Benzoates; Benzoic Acid; Biodegradation, Environmental; Ethylene Glycols; Methods; Nitrophenols; Propylene Glycols; Reference Standards; Seawater; Water Pollutants, Chemical