Determination of the photodegradability of nitroaklanes by means of the Fujiki- and GSF-tests.

The light induced degradation of nitromethane, nitroethane, 1-nitropropane and 2-nitropropane in the gas phase (Fujiki-Test) and adsorbed on silica gel (GSF-Test) was studied. It was found that light induced degradation in the gas phase is significantly faster. 14C-labelled compounds were used in the case of reaction on silica gel. A new method for microsynthesis of the nitroalkanes is described

Verhalten von 2,4-Dichlophenol, 2,4,6-Trichlorphenol und Pentachlorphenol bei der Kompostierung in einer standardiserten Laboranlage.

In einer Versuchsanlage im Labormaßstab zur Kompostierung von standardisierten Hausmüll wurden Translokation, Umwandlung und Abbau von 14C-markierten 2,4-Dichlorphenol, 2,4,6-Trichlorphenol und Pentachlorphenol untersucht. Als Hauptabbauprodukte wurden die entsprechenden Anisole gefunden. Die Bilanzierung zeigt, daß das hoch chlorierte Pentachlorphenol mit der höchsten Konzentration im Kompost verbleibt

Determination photostability of selected agrochemicals in water and soil.

The photolysis of selected pesticides in aqueous solutions has been investigated. The photolysis produced different intermediate substances, which were also found to be soil and microbial degradation products The phototransformation in the presence of TiO2 and humic substances leads to a disappearance of these compounds The reaction rate is dependent on the semiconductor oxide and concentration. Photoproducts were isolated and characterized by different spectroscopic methods. Results from this study indicate that degradation products of isoproturon are more toxic on Daphnia magna than on the parent compound

Photochemistry and photoinduced toxicity of Acifluorfen, a diphenyl-ether herbicide

Photochemistry studies can be helpful in assessing the environmental fate of chemicals. Photochemical reactions lead to the formation of by-products that can exhibit different toxicological properties from the original compound. For this reason the photochemical behavior of the herbicide acifluorfen (5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid) in the presence of different solvents was studied. Photochemical reactions were carried out using a high-pressure mercury arc and a solar simulator. Kinetic parameters and quantum yields were determined. The identification of photoproducts was performed by mass spectrometry and [1H] nuclear magnetic resonance (NMR). Nitrofluorfen, hydroxy-nitrofluorfen, 2-chloro-4-(trifluoromethyl)phenol, 5-trifluoromethyl-5'-nitrodibenzofuran, and other derivatives were identified. The photochemical reactions were also carried out in the presence of either a singlet or a triplet quencher, and in the presence of either a radical initiator or a radical inhibitor. Substances used as inhibitors of the excited levels T1 and S1 showed that photodegradation of acifluorfen begins from a singlet state S1 through a pi,pi* transition. The role of free radicals in the photodegradation of acifluorfen was determined and a radical mechanism was proposed. Toxicity tests against Daphnia magna Strauss showed that acifluorfen was not toxic at a concentration of 0.1 mM; however, photoproducts formed after 36 h of UV exposure of the herbicide induced a remarkable toxicity to the test organism

The dissipation, distribution and fate of a branched 14C-nonylphenol isomer in lake water/sediment systems.

A single tertiary isomer which is believed to be one of the major branched isomers of the isomeric nonylphenol was synthesized for use in investigations on its metabolism and estrogenicity in aquatic organisms. The physico-chemical properties of the isomer were determined to enable the prediction of its behaviour in aquatic environments. From laboratory investigations on its dissipation and distribution in lake water, which are reported in this paper, it was found that it had a half-life of dissipation of 38.1 days and 20.1 days in an open lake water and in an open lake water/ sediment system, respectively, and to be rapidly partitioned in to sediment giving a high concentration factor of 1.76 after 28 days with an initial dose concentration of 2.52 ppm. The main dissipation route was found to occur through volatilization and co-distillation. The isomer was, however, found to be resistant to biodegradation in both the lake water and sediment, showing only a slight 9% loss (after 56 days) and 4.2% loss (after 28 days), of the 14C-residues in lake water and lake water/sediment systems, respectively, by microbial activity. Transformation to other more polar metabolites possibly by hydroxylation was also found to be minimal in both lake water and sediment samples after 14 days by HPLC analysis. After 7 days, only 2.25 and 7.4% transformation to a more polar metabolite was detected in lake water and sediment samples, respectively

Effects of 4-nonylphenol on phytoplankton and periphyton in aquatic microcosms.

The effects of nonylphenol (NP) on phytoplankton and periphyton were studied in 230 L outdoor microcosms. Phytoplankton cell density and biomass, phytoplankton and periphyton diversity, and assemblage composition were analyzed during a four-week preapplication period, followed by six weeks of NP treatment via controlled release and a six weeks postapplication period. Changes in species richness and diversity were not correlated with NP concentrations. However, changes in phytoplankton cell densities during the first week of the postapplication period were related to previous exposure. In the controls and the lowest-dosed microcosm, Conjugatophyceae constituted most of the biomass during the dosing and the postapplication period. In contrast, Dinophyceae dominated the biomass during the dosing and the postapplication period at higher NP concentrations. Principal response curves revealed changes in phytoplankton assemblage composition during the dosing and the postapplication period. Dinophyceae and most Cyanophyceae were more abundant at intermediate and higher NP concentrations, whereas Conjugatophyceae were less abundant compared to controls. Assemblages only partly recovered during the postapplication period. Periphyton taxon richness, diversity, and assemblage change was not related to NP concentrations. At the lowest and intermediate concentration, assemblages were significantly different from the controls and the higher concentrations, which were similar during the treatment period

Effects of a Branched p-Nonylphenol Isomer (4(3',6'-dimethyl-3'-heptyl)-phenol) on Embryogenesis in Lymnae stagnalis L.

The tertiary branched alkyl-chain isomers of p-nonylphenol (NP) are perceived to have more estrogenic potency than its constituent secondary and primary straight alkyl-chain isomers. Investigations with single tertiary branched isomers of NP can therefore contribute toward the elucidation of the mechanisms of toxicity and estrogenicity of NP. A single tertiary branched alkyl-chain isomer (4(3',6'-dimethyl-3'-heptyl)-phenol) was used in studies to determine its effects on embryonic growth and mortality in Lymnaea stagnalis L. Egg masses were exposed to the test compound for 20 days in a static waterborne-exposure regime with an average NP concentration of 105 microg/L and water temperature range of 18-20 degrees C. Observations were made under a microscope and pictures were taken with a digital camera to determine the various developmental stages of growth, the duration of growth in each stage, embryo hatchability, and embryo mortality. The isomer was found to cause significant delay in all stages of growth and more significantly in the Morula and Veliger stages. An increase in embryo mortality, from the third day until the end of the experiment, was observed in exposed egg masses compared to controls. The hatching success of embryos was also significantly reduced by exposure, with 81% hatchability in exposed egg masses compared to 93% in the controls, after 18 days of continuous exposure. The encapsulating jelly strand that completely covers the rows of egg masses may have prevented the isomer residues from effectively penetrating into the embryos as shown by the observed low bioconcentration factors of the isomer in egg masses during exposure, resulting in unexpectedly lower observed estrogenic effects. However, this factor was not investigated. In vivo biotransformation of some of the residues of the isomer into catechol metabolites by the embryos during exposure could also result in the reduction of its estrogenic potential. To understand more fully the extent of toxicity and estrogenicity of this isomer, in vitro estrogenic assays are recommended. It would also be necessary to investigate its estrogenic effects on embryo development after in vivo maternal exposure