Influences of Aquatic Plants on the Fate of the Pyrethroid Insecticide Lambda-Cyhalothrin in Aquatic Environments

Abstract

Aquatic exposure assessments for pesticides are generally based on laboratory studies performed in water alone or water sediment systems. Although aquatic macrophytes, which include a variety of bryophytes, macroalgae, and angiosperms, can be a significant component of many aquatic ecosystems, their impact on pesticide fate is generally not included in exposure assessments. To investigate the influence of aquatic plants on the fate and behavior of the pyrethroid insecticide lambda (lambda)-cyhalothrin, two laboratory experiments (to assess adsorption and degradation) and an indoor microcosm study (to assess fate under semirealistic conditions) were conducted. In the laboratory studies, adsorption to macrophytes was extensive and essentially irreversible, and degradation occurred rapidly by cleavage of the ester bond. In the indoor microcosm, which contained water, sediment, and macrophytes from a pond, degradation was also rapid, with DT50 and DT90 values of less than 3 and 19 h, respectively, for dissipation from the water column and of less than 3 and 56 h, respectively, for the whole system. For adsorptive and readily degraded pesticides like lambda-cyhalothrin, we conclude that macrophytes have considerable influence on fate and behavior in surface waters.

Mitigating with macrophytes: Submersed plants reduce the toxicity of pesticide‐contaminated water to zooplankton

“…For example, Elodea could be sorbing malathion onto its surfaces and thus reducing water toxicity to Daphnia. However, although many highly-lipophilic insecticides with Log K OW values greater than 6.0 (e.g., pyrethroid and organochlorine insecticides) will bind rapidly to submersed macrophytes [20,21], malathion is relatively hydrophilic (Log K OW ¼ 2.3), and it remains unclear how much macrophytes will sorb this insecticide. In the aforementioned experiment by Gao et al [23], the authors found no evidence that malathion was taken up by macrophytes during the first 48 h following exposure.…”

“…For example, macrophytes can sorb insecticides, potentially reducing the duration and intensity of exposure experienced by aquatic taxa [18,19]. In fact, submersed macrophytes can sorb up to 90% of insecticides from the water column within 24 h, but such high sorption rates only occur for highly lipophilic compounds (i.e., Log octanolwater partition coefficient, K OW > 6.0), such as organochlorine (e.g., dichlorodiphenyltrichloroethane [DDT]) and pyrethroid (e.g., lambda-cyhalothrin) insecticides [20,21]. For less lipophilic compounds-such as the commonly applied organophosphate insecticides chlorpyrifos (Log K OW ¼ 4.81) and malathion (Log K OW ¼ 2.3)-the amount of insecticides removed from the water column by macrophytes typically ranges from 0 to 50% in a 24-h period [18,22,23].…”

Threshold Levels for Effects of Insecticides in Freshwater Ecosystems: A Review

“…S-stag = single application in a stagnant system; S-stream = single application in a running system; M-stag = multiple applications in a stagnant system; M-stream = multiple applications in a running system; L-stag = prolonged constant exposure in a stagnant system; L-stream = prolonged constant exposure in a running system. but also by the distribution of the active ingredient over different environmental compartments such as sediment, organic and inorganic particulate material, aquatic plants (e.g., Hill, 1989;Brock et al, 1993;Brock, 1994, Samsøe-Petersen et al, 2001;Hand et al, 2001) and volatilisation from the water (e.g., Larkin and Tjeerdma, 2000). Initial half-life values of dissolved organophosphates and carbamates in the water of stagnant (model) ecosystems are in the order of less than 1-10 days (Crossland and Bennett, 1984;Hanazato and Yasuno, 1990;Lahr and Diallo, 1993;Crum and Brock, 1994;Tanner and Knuth, 1995;Wayland and Boag, 1995;Giddings et al, 1996).…”

“…Initial half-life values of dissolved organophosphates and carbamates in the water of stagnant (model) ecosystems are in the order of less than 1-10 days (Crossland and Bennett, 1984;Hanazato and Yasuno, 1990;Lahr and Diallo, 1993;Crum and Brock, 1994;Tanner and Knuth, 1995;Wayland and Boag, 1995;Giddings et al, 1996). In the case of pyrethroids, initial half-life in the water columns are in the order of less than 1 h to 3 days (Stephenson et al, 1986;Heinis and Knuth, 1992;Fairchild et al, 1992b;Farmer et al, 1995;Hand et al, 2001;Roessink et al, in press). Reported half-life of sediment-adsorbed pesticides is generally much longer (days to weeks) in the above-mentioned studies.…”

Ecological Effects of Spring and Late Summer Applications of Lambda-Cyhalothrin on Freshwater Microcosms

“…Brock et al (1992), for example, showed for chlorpyrifos that the mixing of the compound through the water column was strongly influenced by the vegetation structure in microcosms. For lambda-cyhalothrin, it has been demonstrated that different densities of macrophytes can have considerable influence on the fate and bioavailability of this compound (Hand et al 2001;Leistra et al 2003). Experiments with chlorpyrifos simulating different environmental conditions indicated that at higher water temperatures, and in combination with higher light intensities, dissipation rates increased (Van Wijngaarden et al 2005).…”