UV light and temperature induced fluridone degradation in water and sediment and potential transport into aquifer

Efficacy and Fate of Fluridone Applications for Control of Invasive Submersed Aquatic Vegetation in the Estuarine Environment of the Sacramento-San Joaquin Delta

“…A laboratory experiment using a quantity of fluridone pellets that would theoretically produce a 10-part-per-million (ppm) aqueous solution demonstrated that < 1% of fluridone binds to sediment composed of sand, while > 90% of fluridone binds to sediment composed of clay or organic peat (Mossler et al 1993). In a laboratory experiment related to our study, a 10-ppm aqueous solution of fluridone had an estimated halflife of 48 days in French Island sediment but a half-life of only 38 days in a mixture of 25% French Island sediment and 75% pure sand (maintained at 20 °C with no light) (Wickham et al 2020). If fluridone released from pelleted formulations becomes bound to bed sediments, it could remain there for long periods because it would have low exposure to ultraviolet photolysis and likely would be less bioavailable for microbial metabolism and plant absorption (Bailey and White 1964;Muir and Grift 1982;Wickham et al 2020).…”

“…In a laboratory experiment related to our study, a 10-ppm aqueous solution of fluridone had an estimated halflife of 48 days in French Island sediment but a half-life of only 38 days in a mixture of 25% French Island sediment and 75% pure sand (maintained at 20 °C with no light) (Wickham et al 2020). If fluridone released from pelleted formulations becomes bound to bed sediments, it could remain there for long periods because it would have low exposure to ultraviolet photolysis and likely would be less bioavailable for microbial metabolism and plant absorption (Bailey and White 1964;Muir and Grift 1982;Wickham et al 2020). These high sediment concentrations of fluridone could negatively affect benthic organisms such as mollusks, zooplankton, and macroinvertebrates (Crosby and Tucker 1966;Yi et al 2011;Archambault et al 2015).…”

“…Conversely, during the month of June 2018, water temperatures were higher (mean: 21.5 °C, SD: 1.2 °C) and day length was at an annual maximum (up to 14 h 51 min). In a laboratory experiment, Wickham et al (2020) found that decreasing water temperature from 20 to 4 °C increased the estimated half-life of a 10-ppm aqueous solution of fluridone in French Island sediment from 1.8 to 5.1 months (maintained in dark conditions). In a similar laboratory experiment, Wickham et al (2020) observed a significant reduction in the halflife of fluridone in water with increasing ultraviolet light intensity (e.g., 27.3 d with 1000 µW/cm 2 ; 48.1 d with 25 µW/cm 2 ) but no effect of ultraviolet light intensity (up to 1000 µW/cm 2 ) on the degradation rate of fluridone in French Island sediment (12 h light: 12 h dark, 20 °C).…”

“…In a laboratory experiment, Wickham et al (2020) found that decreasing water temperature from 20 to 4 °C increased the estimated half-life of a 10-ppm aqueous solution of fluridone in French Island sediment from 1.8 to 5.1 months (maintained in dark conditions). In a similar laboratory experiment, Wickham et al (2020) observed a significant reduction in the halflife of fluridone in water with increasing ultraviolet light intensity (e.g., 27.3 d with 1000 µW/cm 2 ; 48.1 d with 25 µW/cm 2 ) but no effect of ultraviolet light intensity (up to 1000 µW/cm 2 ) on the degradation rate of fluridone in French Island sediment (12 h light: 12 h dark, 20 °C). West et al (1983) applied fluridone pellets at 1.12 kg ha −1 in six ponds spanning a range of locations across North America and found sediment concentrations up to 0.18 kg ha −1 (roughly 360-900 ppb) in samples collected 6 months after the treatment.…”

Combined effects of heatwaves and micropollutants on freshwater ecosystems: Towards an integrated assessment of extreme events in multiple stressors research

“…The thermometer symbol indicates an effect related to temperature only, whereas the symbols of the thermometer and of the chemical together indicate a combined effect of both. (1) Bighiu & Goedkoop ( 2021 ), (2) Zeng et al ( 2014 ), (3) Zamarreňo et al ( 2009 ), (4) Höfle ( 1979 ), (5) White et al ( 1991 ), (6) Berthelot et al ( 2019 ), (7) Hayes et al ( 2019 ), (8) Klausmeier et al ( 2004 ), (9) Duarte et al ( 2013 ), (10) Donnelly et al ( 1990 ), (11) Stelzer et al ( 2003 ), (12) Fernandes et al ( 2012 ), (13) Phillips et al ( 2017 ), (14) Kaushik and Hynes ( 1971 ), (15) Pomeroy and Wiebe ( 1988 ), (16) Delnat et al ( 2021 ), (17) Wickham et al ( 2020 ), and (18) Arias Font et al ( 2021 )…”