Terbutryn

Transformation and stable isotope fractionation of the urban biocide terbutryn during biodegradation, photodegradation and abiotic hydrolysis

Terbutryn is a widely used biocide in construction materials like paint and render to prevent the growth of microorganisms, algae and fungi. Terbutryn is released from the facades into the environment during rainfall, contaminating surface waters, soil and groundwater. Knowledge of terbutryn dissipation from the facades to aquatic ecosystems is scarce. Here, we examined in laboratory microcosms degradation half-lives, formation of transformation products and carbon and nitrogen isotope fractionation during terbutryn direct (UV light with λ = 254 nm and simulated sunlight) and indirect (simulated sunlight with nitrate) photodegradation, abiotic hydrolysis (pH = 1, 7 and 13), and aerobic biodegradation (stormwater pond sediment, soil and activated sludge). Biodegradation half-lives of terbutryn were high (>80 d). Photodegradation under simulated sunlight and hydrolysis at extreme pH values indicated slow degradability and accumulation in the environment. Photodegradation resulted in a variety of transformation products, whereas abiotic hydrolysis lead solely to terbutryn-2-hydroxy in acidic and basic conditions. Biodegradation indicates degradation to terbutryn-2-hydroxy through terbutryn-sulfoxide. Compound-specific isotope analysis (CSIA) of terbutryn holds potential to differentiate degradation pathways. Carbon isotope fractionation values (εC) ranged from -3.4 ± 0.3‰(hydrolysis pH 1) to +0.8 ± 0.1‰(photodegradation under UV light), while nitrogen isotope fractionation values ranged from -1.0 ± 0.4‰(simulated sunlight photodegradation with nitrate) to +3.4 ± 0.2‰?(hydrolysis at pH 1). In contrast, isotope fractionation during biodegradation was insignificant. ΛN/C values ranged from -1.0 ± 0.1 (hydrolysis at pH 1) to 2.8 ± 0.3 (photodegradation under UV light), allowing to differentiate degradation pathways. Combining the formation of transformation products and stable isotope fractionation enabled identifying distinct degradation pathways. Altogether, this study highlights the potential of CSIA to follow terbutryn degradation in situ and differentiate prevailing degradation pathways, which may help to monitor urban biocide remediation and mitigation strategies.

Monitoring terbutryn pollution in small rivers of Hesse, Germany

Four small river systems in Hesse, Germany, were investigated with respect to seasonal and spatial concentrations of the herbicide terbutryn [2-(t-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine]. Despite introduction of a ban on its use as a herbicide in July 2003, terbutryn was still present in the rivers during the whole sampling period from September 2003 to September 2006, and there was no trend of decreasing concentration during this time. In the Weschnitz and Modau river systems the mean terbutryn concentration exceeded the German drinking water ordinance threshold value for single biocides. Maximum concentrations of up to 5.6 microg l(-1) were determined in the Weschnitz River. Higher terbutryn concentrations in summer are suggested to originate from agricultural sources, as well as from sediment redissolution. Effluents of two sewage treatment plants had high terbutryn concentrations, indicating that terbutryn enters the rivers from this source. Sources other than agriculture must explain terbutryn occurrence in the rivers during winter, when farm pesticide application typically ceases. The potential for mobilization of terbutryn from sediments and leaching from soils are discussed.

Transformation of biocides irgarol and terbutryn in the biological wastewater treatment

The biocides irgarol and terbutryn enter the wastewater treatment plant (WWTP) via combined sewer systems after leaching from coatings and paints of materials. In this study, the biotransformation of irgarol and terbutryn was examined in aerobic batch experiments with activated sludge taken from the nitrification zone of a conventional WWTP, since currently there is no information about the fate of irgarol and terbutryn in biological wastewater treatment. Both, irgarol and terbutryn were transformed into one main transformation product (TP) following pseudo first-order kinetics. The TPs were tentatively identified by high-resolution mass spectrometry (HR-MS) to be irgarol sulfoxide and terbutryn sulfoxide. The final confirmation of the proposed chemical structures of the TPs was achieved by a comparison of mass spectra and nuclear magnetic resonance (NMR) spectra with those of authentic reference standards (e.g., synthesized). An analytical method for the sensitive quantification of irgarol, terbutryn and their TPs in environmental samples was developed based on solid phase extraction (SPE) and LC tandem MS detection. Irgarol sulfoxide and terbutryn sulfoxide were detected in the effluents (average concentrations up to 22 ng L(-1) and 65 ng L(-1)) of all four investigated WWTPs as well as in streams and small rivers (up to 14 ng L(-1) and 34 ng L(-1)). Luminescent bacteria inhibition test with Vibrio fischeri exhibited that the TPs irgarol sulfoxide and terbutryn sulfoxide feature a similar bacterial toxicity than the parent compounds.

Degradation of terbutryn in sediments and water under various redox conditions

A laboratory study was conducted to examine the degradation of terbutryn [2-(t-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine] in sediment and water under different redox conditions. Terbutryn degraded slowly in static aerobic systems (loosely capped flask, 25 degrees C) with half-lives of 240 and 180 days in pond and river sediment, respectively. Degradation products, identified by co-chromatography on TLC and HPLC systems, included hydroxy-terbutryn, terbutryn-sulfoxide and N-deethyl terbutryn. Hydroxyterbutryn was the major degradation product in sediments and water representing 60-70% of the extractable radioactivity after 515 days incubation. Under nitrogen aeration in respirometer flasks (redox potential -46 to +210 mv) degradation of terbutryn was very slow with half lives greater than 650 days.

Effects of co-exposure of the triazine herbicides atrazine, prometryn and terbutryn on Phaeodactylum tricornutum photosynthesis and nutritional value

Triazine herbicides are widely used in agricultural production, and large amounts of herbicide residue enter the ocean through surface runoff. In this study, the toxicities of the triazine herbicides atrazine, prometryn and terbutryn (separately and mixed) to Phaeodactylum tricornutum were investigated. The EC50 values of atrazine, prometryn and terbutryn were 28.38 μg L^-1, 8.86 μg L^-1, and 1.38 μg L^-1, respectively. The EC50 of an equitoxic mixture of the three herbicides was 0.78 TU, indicating that they had synergistic effects. The equitoxic mixture accumulated in P. tricornutum, which damaged chloroplast and mitochondria structures and significantly decrease the biomass, levels of key cellular components (such as chlorophyll a (chl a), carbon (C) and nitrogen (N) content, fatty acid content) and the effective photochemical quantum yield of photosystem II (PSII, ∆Fv/Fm). The mixture also downregulated key genes in the light response (PsbD, PetF), dark response (PGK, PRK), tricarboxylic acid (TCA) cycle (CS, ID, OGD, and MS) and fatty acid synthesis (FABB, SCD, and PTD9). P. tricornutum partially alleviates the effects of the mixture on photosynthesis and fatty acid synthesis by upregulating PetD, PsaB, RbcL and FabI expression. The triazine herbicide mixture reduced the biomass and nutritional value of marine phytoplankton by inhibiting photosynthesis and energy metabolism.