Benzotriazole is a commonly used additive in aircraft de-icing fluids. As a result of extensive de-icing activities the compound is detected in the groundwater below de-icing platforms at several international airports. The compound is toxic, and not biodegradable. Laboratory tests have been performed to study if UV irradiation can degrade the compound and reduce the aquatic toxicity. Benzotriazole can be degraded by UV irradiation at pH values below 7. Approximately 65% reduction in the benzotriazole concentration was achieved at a dose of 320 mWs/cm2, and almost 90% reduction was achieved at 1070 mWs/cm2, with an apparent first order relation between the logarithm to the UV dose and the reduction. Benzotriazole is not significantly mineralised by UV irradiation, but transformed into other compounds, of which aniline and phenazine were identified. The metabolites show toxic effects, but they are not as toxic as benzotriazole, resulting in a general decrease in toxicity as a result of UV irradiation.
A research has been undertaken studying pesticide residues in water from greenhouses and the use of soils and filter materials to reduce such losses. The pesticides detected in water samples collected downstream greenhouses include 9 fungicides, 5 herbicides and 4 insecticides. 10 compounds from flower and vegetable productions were frequently found to exceed environmental risk levels, and with a few exceptions the compounds were found in higher concentrations than those typically found in agricultural runoff. Some compounds were found in high concentrations (>1 microg/l) in undiluted runoff from greenhouses producing vegetables. Nutrient concentrations in the runoff were also sporadically very high, with phosphorous values varying between 0.85 and 7.4 mg P/l, and nitrogen values between 7.5 and 41.4 mg N/l. Undiluted runoff from the productions showed values of 60 mg P/l and 300 mg N/l. High values of pesticides correlated with high values of nutrients, especially P. Column experiments using a sandy agricultural soil and stock solutions of non-polar and slightly polar pesticides mixed with a complex binder and nutrients showed a significant reduction for nearly all of the compounds used, indicating that transport through soil will reduce the concentrations of the studied pesticides. The pesticide adsorption capacity of the filter materials pine bark, peat, Sphagnum moss, compost, oat straw, ferrous sand and clay soil were tested in batch and column experiments. Adsorption were studied contacting the filter materials with aqueous solutions containing greenhouse production pesticides. The batch experiments showed that pine bark and peat, both combining a high content of organic matter with a low ph, provided the highest adsorption for most of the tested pesticides. Sphagnum moss, compost and oat straw also showed high adsorption for most of the pesticides, while the mineral filters provided the lowest adsorption (30-55%). Further column experiments confirmed these results, displaying the best removal efficiency in the organic materials, varying from 200 microg/g in compost, to 500 microg/g in moss, straw and pine bark.
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