- E. Berg van den (1)
- F.F.J. Bransen (1)
- P.J. Brink van den (7)
- T.C.M. Brock (8)
- S.J.H. Crum (4)
- J.G.M. Cuppen (1)
- A. Focks (1)
- R. Gylstra (1)
- L.H. Hand (1)
- M.W. Hoorn van den (1)
- M.M.S. Horst ter (1)
- M. Leistra (1)
- L. Maltby (1)
- S.J. Maund (3)
- A. Rico (1)
- I. Roessink (2)
- J.S. Warinton (1)
- L. Wendt-Rasch (1)
- R.P.A. Wijngaarden van (7)
- P. Woin (1)
- A.J. Zweers (1)
Evaluating Aquatic invertebrate vulnerability to insecticides based on intrinsic sensitivuty, biological traits, and toxic mode of action
Rico, A. ; Brink, P.J. van den - \ 2015
Environmental Toxicology and Chemistry 34 (2015)8. - ISSN 0730-7268 - p. 1907 - 1917.
ecological risk-assessment - fresh-water arthropods - species sensitivity - community structure - lambda-cyhalothrin - short-term - responses - microcosms - recovery - stream
In the present study, the authors evaluated the vulnerability of aquatic invertebrates to insecticides based on their intrinsic sensitivity and their population-level recovery potential. The relative sensitivity of invertebrates to 5 different classes of insecticides was calculated at the genus, family, and order levels using the acute toxicity data available in the US Environmental Protection Agency ECOTOX database. Biological trait information was linked to the calculated relative sensitivity to evaluate correlations between traits and sensitivity and to calculate a vulnerability index, which combines intrinsic sensitivity and traits describing the recovery potential of populations partially exposed to insecticides (e.g., voltinism, flying strength, occurrence in drift). The analysis shows that the relative sensitivity of arthropods depends on the insecticide mode of action. Traits such as degree of sclerotization, size, and respiration type showed good correlation to sensitivity and can be used to make predictions for invertebrate taxa without a priori sensitivity knowledge. The vulnerability analysis revealed that some of the Ephemeroptera, Plecoptera, and Trichoptera taxa were vulnerable to all insecticide classes and indicated that particular gastropod and bivalve species were potentially vulnerable. Microcrustaceans (e.g., daphnids, copepods) showed low potential vulnerability, particularly in lentic ecosystems. The methods described in the present study can be used for the selection of focal species to be included as part of ecological scenarios and higher tier risk assessments.
Acute tier-1 and tier-2 effect assessment approaches in the EFSA Aquatic Guidance Diocument: are they sufficiently protective for insecticides? : Are they sufficiently protective for insecticides?
Wijngaarden, R.P.A. van; Maltby, L. ; Brock, T.C.M. - \ 2015
Pest Management Science 71 (2015)8. - ISSN 1526-498X - p. 1059 - 1067.
species sensitivity distributions - pyrethroid insecticide - lambda-cyhalothrin - chronic toxicity - daphnia-magna - chironomus-riparius - gamma-cyhalothrin - risk-assessment - joint toxicity - chlorpyrifos
BACKGROUND The objective of this paper is to evaluate whether the acute tier-1 and tier-2 methods as proposed by the Aquatic Guidance Document recently published by the European Food Safety Authority (EFSA) are appropriate for deriving regulatory acceptable concentrations (RACs) for insecticides. The tier-1 and tier-2 RACs were compared with RACs based on threshold concentrations from micro/mesocosm studies (ETO-RAC). A lower-tier RAC was considered as sufficiently protective, if less than the corresponding ETO-RAC. RESULTS ETO-RACs were calculated for repeated (n =¿13) and/or single pulsed applications (n =¿17) of 26 insecticides to micro/mesocosms, giving a maximum of 30 insecticide¿×¿application combinations (i.e. cases) for comparison. Acute tier-1 RACs (for 24 insecticides) were lower than the corresponding ETO-RACs in 27 out of 29 cases, while tier-2 Geom-RACs (for 23 insecticides) were lower in 24 out of 26 cases. The tier-2 SSD-RAC (for 21 insecticides) using HC5/3 was lower than the ETO-RAC in 23 out of 27 cases, whereas the tier-2 SSD-RAC using HC5/6 was protective in 25 out of 27 cases. CONCLUSION The tier-1 and tier-2 approaches proposed by EFSA for acute effect assessment are sufficiently protective for the majority of insecticides evaluated. Further evaluation may be needed for insecticides with more novel chemistries (neonicotinoids, biopesticides) and compounds that show delayed effects (insect growth regulators).
Integrating chemical fate and population-level effect models of pesticides: the importance of capturing the right scales
Focks, A. ; Horst, M.M.S. ter; Berg, E. van den; Baveco, H. ; Brink, P.J. van den - \ 2014
Ecological Modelling 280 (2014). - ISSN 0304-3800 - p. 102 - 116.
asellus-aquaticus l - potential application - lambda-cyhalothrin - life-history - growth - invertebrates - isopoda - field - ecotoxicology - biodiversity
Any attempt to introduce more ecological realism into ecological risk assessment of chemicals faces the major challenge of integrating different aspects of the chemicals and species of concern, for example, spatial scales of emissions, chemical exposure patterns in space and time, and population dynamics and dispersal in heterogeneous landscapes. Although these aspects are not considered in current risk assessment schemes, risk assessors and managers are expressing increasing interest in learning more about both the exposure to and the effects of chemicals at landscape level. In this study, we combined the CASCADE-TOXSWA fate model, which predicts the fate of pesticides in an interconnected system of water bodies with variable hydrological characteristics, with the MASTEP mechanistic effect model, which simulates population dynamics and effects of pesticides on aquatic species at the scale of individual water bodies. To this end, we extrapolated MASTEP to the scale of realistic landscapes and linked it to dynamic exposure patterns. We explored the effects of an insecticide on the water louse Asellus aquaticus for a typical Dutch landscape covering an area of about 10 km2 containing 137 water bodies (drainage ditches) with a total length of about 65 km and different degrees of connectivity. Pesticide treatments used in potato crop were assumed to result in a spray-drift input of 5% (non-mitigated) and 1% (mitigated) of the amount of pesticide applied into parts of the water body network. These treatments resulted in highly variable exposure patterns both in space and time. The effects of the pesticide on the species were investigated by comparing two scenarios with low and high individual-level sensitivity. We found that downstream transport of the pesticide led to exposure of water bodies that did not receive direct spray-drift input, even though this particular pesticide was assumed to dissipate rapidly from water. The observed differences in population-level effects and recovery patterns ranged from no observable effects in the low spray-drift and low sensitivity scenario to severe reduction of abundances in the high spray-drift and high sensitivity scenario. These results illustrate the sensitivity of our modelling approach, but also show the need for precise calculations of pesticide inputs and model parameterisation. Our study demonstrates the potential of coupled fate-and-effect to explore realistic scenarios at the scale of heterogeneous landscapes. Such scenarios could include the application of multiple pesticides to one or more crop types. Spatial realism of the landscape represented in the model ensures realistic consideration of population growth and dispersal as the two main recovery mechanisms. Future options for the landscape-scale fate-and-effect simulation approach include exploring the effects of mitigation measures on the risk estimates at landscape scale and hence represent a step towards risk management.
Acute toxicity tests with Daphnia magna, Americamysis bahia, Chironomus riparius and Gammarus pulex and implications of new EU requirenments for the aquatic effect assessment of insecticides
Brock, T.C.M. ; Wijngaarden, R.P.A. van - \ 2012
Environmental Science and Pollution Research 19 (2012)8. - ISSN 0944-1344 - p. 3610 - 3618.
lambda-cyhalothrin - pyrethroid insecticide - risk-assessment - chlorpyrifos - exposure - invertebrates - mesocosms - community - model - macroinvertebrates
Threshold concentrations for treatment related effects of 31 insecticides, as derived from aquatic micro-/mesocosm tests, were used to calibrate the predictive value of the European Tier-1 acute effect assessment on basis of laboratory toxicity tests with Daphnia magna, Chironomus spp., Americamysis bahia and Gammarus pulex. The acute Tier-1 effect assessment on basis of Daphnia (EC(50)/100) overall was protective for organophosphates, carbamates and most pyrethroids but not for neonicotinoids and the majority of insect growth regulators (IGRs) in the database. By including the 28-day water-spiked Chironomus riparius test, the effect assessment improves but selecting the lowest value on basis of the 48-h Daphnia test (EC50/100) and the 28-day Chironomus test (NOEC/10) is not fully protective for 4 out of 23 insecticide cases. An assessment on basis of G. pulex (EC(50)/100) is sufficiently protective for 15 out of 19 insecticide cases. The Tier-1 procedure on basis of acute toxicity data (EC(50)/100) for the combination of Daphnia and A. bahia and/or Chironomus (new EU dossier requirements currently under discussion) overall is protective to pulsed insecticide exposures in micro-/mesocosms. For IGRs that affect moulting, the effect assessment on basis of the 48-h Chironomus test (EC(50)/100) may not always be protective enough to replace that of the water-spiked 28-day C. riparius test (NOEC/10) because of latency of effects.
Effects of the pyrethroid insecticide gamma-cyhalothrin on aquatic invertebrates in laboratory and outdoor microcosm tests
Wijngaarden, R.P.A. van; Barber, I. ; Brock, T.C.M. - \ 2009
Ecotoxicology 18 (2009)2. - ISSN 0963-9292 - p. 211 - 224.
species sensitivity distributions - active ingredient chlorpyrifos - fresh-water microcosms - lambda-cyhalothrin - experimental ditches - community - responses - toxicity - single - field
The sensitivity of a range of freshwater lentic invertebrates to gamma-cyhalothrin (GCH), a single enantiomer of the synthetic pyrethroid lambda-cyhalothrin, was assessed in single species laboratory tests and an outdoor multi-species ecosystem test. The most sensitive species in the laboratory single species tests with GCH was Chaoborus obscuripes (96 h EC50: 3.8 ng/l). The species sensitivity distribution curve, based on the laboratory 96 h EC50 acute toxicity data for eight species, gave a median HC5 value for GCH of 2.12 ng/l. The NOECcommunity derived from the multi-species ecosystem test was 5 ng/l, and the insects Chaoborus sp. and Caenis sp. were identified as the most sensitive species. The results indicate that the median HC5, based on eight species selected to include those known to be sensitive to pyrethroids, provided a good estimation of the NOECcommunity for GCH. Furthermore, the results for GCH indicated that the endpoints typically used in higher-tier risk assessments for pesticides in Europe (HC5 and NOECcommunity) were consistent with expectations when compared to the equivalent endpoints for the racemate LCH
Impact of triphenyltin acetate in microcosms simulating floodplain lakes; II comparison of species sensitivity distributions between laboratory and semi-field
Roessink, I. ; Belgers, J.D.M. ; Crum, S.J.H. ; Brink, P.J. van den; Brock, T.C.M. - \ 2006
Ecotoxicology 15 (2006)5. - ISSN 0963-9292 - p. 411 - 424.
fresh-water microcosms - prosobranch snails mollusca - organotin compounds - fungicide carbendazim - aquatic invertebrates - endocrine disruptors - lambda-cyhalothrin - primary producers - daphnia-magna - tributyltin
The study objectives were to shed light on the types of freshwater organism that are sensitive to triphenyltin acetate (TPT) and to compare the laboratory and microcosm sensitivities of the invertebrate community. The responses of a wide array of freshwater taxa (including invertebrates, phytoplankton and macrophytes) from acute laboratory Single Species Tests (SST) were compared with the concentration¿response relationships of aquatic populations in two types of freshwater microcosms. Representatives of several taxonomic groups of invertebrates, and several phytoplankton and vascular plant species proved to be sensitive to TPT, illustrating its diverse modes of toxic action. Statistically calculated ecological risk thresholds (HC5 values) based on 96 h laboratory EC50 values for invertebrates were 1.3 ¿g/l, while these values on the basis of microcosm-Species Sensitivity Distributions (SSD) for invertebrates in sampling weeks 2¿8 after TPT treatment ranged from 0.2 to 0.6 ¿g/l based on nominal peak concentrations. Responses observed in the microcosms did not differ between system types and sampling dates, indicating that ecological threshold levels are not affected by different community structures including taxa sensitive to TPT. The laboratory-derived invertebrate SSD curve was less sensitive than the curves from the microcosms. Possible explanations for the more sensitive field response are delayed effects and/or additional chronic exposure via the food chain in the microcosms
Interpretation and extrapolation of ecological responses in model ecosystems stressed with non-persistent insecticides
Wijngaarden, R.P.A. van - \ 2006
University. Promotor(en): S.J. Scheffer, co-promotor(en): Theo Brock; N.M. van Straalen. - Wageningen : Alterra - ISBN 9032703498 - 248
toxiciteit - modellen - oppervlaktewater - insecticiden - risicoschatting - lambda-cyhalothrin - chloorpyrifos - methodologie - zoetwaterecologie - aquatische ecosystemen - ecotoxicologie - toxicity - models - surface water - insecticides - risk assessment - chlorpyrifos - methodology - freshwater ecology - aquatic ecosystems - ecotoxicology
This thesis aims to contribute to the discussion concerning whether micro- and mesocosm studies can serve as adequate models for robust risk assessment of pesticides. For this purpose, results from freshwater micro- and mesocosm experiments conducted under different experimental conditions are presented and compared. Case studies with the relatively well-studied insecticides chlorpyrifos (organophosphate) and lambda-cyhalothrin (synthetic pyrethroid) are used as examples of the variability typical in model ecosystem studies. These studies are placed in the context of other studies to gain insights into the consistency of the outcomes of micro- and mesocosm experiments performed with non-persistent insecticides which act upon the insect nervous system
Ecological effects of Spring and late Summer applications of Lambda-Cyhalothrin on freshwater microcosms
Wijngaarden, R.P.A. van; Brock, T.C.M. ; Brink, P.J. van den; Gylstra, R. ; Maund, S.J. - \ 2006
Archives of Environmental Contamination and Toxicology 50 (2006)2. - ISSN 0090-4341 - p. 220 - 239.
toxiciteit - zoetwaterecologie - lambda-cyhalothrin - seizoenen - lente - zomer - oppervlaktewater - sloten - toxicity - freshwater ecology - seasons - spring - summer - surface water - ditches - active ingredient chlorpyrifos - insecticide dursban(r) 4e - aquatic risk-assessment - community responses - fate - zooplankton - organisms - mesocosms - recovery
The aim of the study was to compare the effects of the pyrethroid insecticide lambda-cyhalothrin (treated at 10, 25, 50, 100, 250 ng active ingredient a.i./L) on a drainage ditch ecosystem in spring and late summer. Microcosms (water volume approximately 430 L) were established using enclosures in a 50-cm¿deep experimental ditch system containing communities typical of macrophyte-dominated freshwater ecosystems. Effects on macroinvertebrates, zooplankton, phytoplankton, macrophytes, and community metabolism were assessed and evaluated using univariate and multivariate statistical techniques. The macroinvertebrate community responded most clearly to treatment and, as anticipated, insects and crustaceans were among the most sensitive organisms. Statistical analysis showed that the underlying community structure was significantly different between the spring and summer experiments. However, the most sensitive species (Chaoborus obscuripes and Gammarus pulex) were abundant in spring as well as in late summer. In spring and late summer, only slight and transient effects were observed at the community level in the 10-ng/L treatment. Overall, the study did not show substantial differences in the responses of sensitive taxa between spring and late summer treatments, and effects thresholds were similar irrespective of season of treatment.
Effects of lambda-cyhalothrin in two ditch microcosm systems of different trophic status
Roessink, I. ; Arts, G.H.P. ; Belgers, J.D.M. ; Bransen, F.F.J. ; Maund, S.J. ; Brock, T.C.M. - \ 2005
Environmental Toxicology and Chemistry 24 (2005)7. - ISSN 0730-7268 - p. 1684 - 1696.
insecticiden - toxiciteit - sloten - waterkwaliteit - oppervlaktewater - trofische graden - eutrofiëring - lambda-cyhalothrin - insecticides - toxicity - ditches - water quality - surface water - trophic levels - eutrophication - insecticide dursban(r) 4e - active ingredient chlorpyrifos - outdoor experimental ditches - aquatic risk-assessment - fresh-water microcosms - pyrethroid insecticide - population-level - community - responses - fate
The fate and effects of the pyrethroid insecticide lambda-cyhalothrin were compared in mesotrophic (macrophyte-dominated) and eutrophic (phytoplankton-dominated) ditch microcosms (0.5 m3). Lambda-cyhalothrin was applied three times at one-week intervals at concentrations of 10, 25, 50, 100, and 250 ng/L. The rate of dissipation of lambda-cyhalothrin in the water column of the two types of test systems was similar. After 1 d, only 30% of the amount applied remained in the water phase. Initial, direct effects were observed primarily on arthropod taxa. The most sensitive species was the phantom midge (Chaoborus obscuripes). Threshold levels for slight and transient direct toxic effects were similar (10 ng/L) between types of test systems. At treatment levels of 25 ng/L and higher, apparent population and community responses occurred. At treatments of 100 and 250 ng/L, the rate of recovery of the macroinvertebrate community was lower in the macrophyte-dominated systems, primarily because of a prolonged decline of the amphipod Gammarus pulex. This species occurred at high densities only in the macrophyte-dominated enclosures. Indirect effects (e.g., increase of rotifers and microcrustaceans) were more pronounced in the plankton-dominated test systems, particularly at treatment levels of 25 ng/L and higher.
Threshold levels for effects of insecticides in freshwater ecosystems: a review
Wijngaarden, R.P.A. van; Brock, T.C.M. ; Brink, P.J. van den - \ 2005
Ecotoxicology 14 (2005)3. - ISSN 0963-9292 - p. 355 - 380.
insecticiden - toxiciteit - waterverontreiniging - oppervlaktewater - carbamaten - risicoschatting - organo-fosforinsecticiden - ecotoxicologie - aquatische ecosystemen - insecticides - toxicity - water pollution - surface water - carbamates - risk assessment - organophosphorus insecticides - ecotoxicology - aquatic ecosystems - active ingredient chlorpyrifos - probabilistic risk assessment - outdoor experimental ditches - artificial stream system - pyrethroid insecticide - littoral enclosures - dursban(r) 4e - cotton pyrethroids - lambda-cyhalothrin - aquatic organisms
A literature review of freshwater (model) ecosystem studies with neurotoxic insecticides was performed to assess ecological threshold levels, to compare these levels with the first tier approach within European Union (EU) administration procedures, and to evaluate the ecological consequences of exceeding these thresholds. Studies published between 1980 and 2001 were reviewed. Most studies covered organophosphates and synthetic pyrethroids in lentic waters. The most sensitive taxa were representatives of crustaceans, insects and fish. Based on toxic units, threshold values were equivalent for compounds with a similar mode of action. This also accounted for the nature and magnitude of direct effects at higher concentrations. Although laboratory single species toxicity tests may not allow predictions on precise ecological effects, some generalisations on effects and recovery can be made with respect to acute standard laboratory EC50 data. The NOECecosystem usually is a factor of 10 or more higher than first tier acceptable concentrations, particularly in the case of single applications and acetylcholinesterase inhibitors. Acceptable concentrations, as set by the EU first tier approach, appear to be protective. Recovery of sensitive endpoints usually occurs within 2 months of the (last) application when peak concentrations remain lower than (0.1–1) × EC50 of the most sensitive standard test species. The consistency of response patterns found in model ecosystem studies can be useful when estimating the ecological risks of pesticides. The use of an effect classification system was also helpful in evaluating effects.
Aquatic risk assessment of a realistic exposure to pesticides used in bulb crops: a microcosm study
Wijngaarden, R.P.A. van; Cuppen, J.G.M. ; Arts, G.H.P. ; Crum, S.J.H. ; Hoorn, M.W. van den; Brink, P.J. van den; Brock, T.C.M. - \ 2004
Environmental Toxicology and Chemistry 23 (2004)6. - ISSN 0730-7268 - p. 1479 - 1498.
toxiciteit - pesticiden - risicoschatting - zoetwaterecologie - gewasbescherming - spuiten - tulpen - lambda-cyhalothrin - asulam - fungiciden - metamitron - aquatische ecosystemen - ecotoxicologie - toxicity - pesticides - risk assessment - freshwater ecology - plant protection - spraying - tulips - fungicides - aquatic ecosystems - ecotoxicology - fresh-water microcosms - insecticide lambda-cyhalothrin - active ingredient chlorpyrifos - dursban(r) 4e - responses - mixture - fate - ecosystems - community
The fungicide fluazinam, the insecticide lambda-cyhalothrin, and the herbicides asulam and metamitron were applied to indoor freshwater microcosms (water volume approximately 0.6 m3). The treatment regime was based on a realistic application scenario in tulip cultivation. Concentrations of each pesticide were equal to 0%, 0.2%, 0.5%, 2%, and 5% spray drift emission of label-recommended rates. Contribution of compounds to the toxicity of the pesticide package was established by expressing their concentrations as fractions of toxic units. The fate of the compounds in the water, and responses of phytoplankton, zooplankton, periphyton, macroinvertebrates, macrophytes, decomposition, and water quality were followed for 13 weeks. The half-lives of lambda-cyhalothrin, metamitron, and fluazinam were 1 to 2 d; that of asulam was >30 d. No consistent effects could be demonstrated for the 0.2% treatment regime that was therefore considered the no-observed-effect concentrationcommunity (NOEC). The macroinvertebrate populations of Gammarus pulex, Asellus aquaticus, and Proasellus meridianus were the most sensitive end points, followed by species of copepods and cladocerans. Responses mainly were due to lambda-cyhalothrin. The 0.5% treatment regime resulted in short-term effects. Pronounced effects were observed at the 2% and 5% treatment levels. At the end of the experiment, the macrophyte biomass that consisted of Elodea nuttallii, showed a decline at the two highest treatment levels, asulam being the causal factor (NOEC: 0.5% treatment level). Primary production was reduced at the 5% treatment level only. In our experiment, the first-tier risk assessment procedure for individual compounds was adequate for protecting sensitive populations exposed to realistic combinations of pesticides. Spray drift reduction measures seem to be efficient in protecting aquatic ecosystems in agricultural areas.
The effects of a pesticide mixture on aquatic ecosystems differing in trophic status: responses of the macrophyte Myriophyllum spicatum and the periphytic algal community
Wendt-Rasch, L. ; Brink, P.J. van den; Crum, S.J.H. ; Woin, P. - \ 2004
Ecotoxicology and Environmental Safety 57 (2004)3. - ISSN 0147-6513 - p. 383 - 398.
aquatisch milieu - waterplanten - schadelijke waterplanten - asulam - herbicidenmengsels - lambda-cyhalothrin - metamitron - onbedoelde effecten - niet-doelorganismen - pesticidenresiduen - trofische graden - onkruiden - aquatic environment - aquatic plants - aquatic weeds - herbicide mixtures - nontarget effects - nontarget organisms - pesticide residues - trophic levels - weeds - fresh-water microcosms - insecticide dursban(r) 4e - phytoplankton succession - pyrethroid insecticides - fungicide carbendazim - phosphorus release - final conclusions - primary producers - model-ecosystems - zooplankton
The effects of a pesticide mixture (asulam, fluazinam, lambda-cyhalothrin, and metamitron) on aquatic ecosystems were investigated in 20 outdoor aquatic microcosms. Ten of the microcosms simulated mesotrophic aquatic ecosystems dominated by submerged macrophytes (Elodea). The others simulated eutrophic ecosystems with a high Lemna surface coverage (Lemna). This paper describes the fate of the chemicals as well as their effects on the growth of Myriophyllum spicatum and the periphytic algal community. In the Elodea-dominated microcosms significant increase in the biomass and alterations of species composition of the periphytic algae were observed, but no effect on M. spicatum growth could be recorded in response to the treatment. The opposite was found in the Lemna-dominated microcosms, in which decreased growth of M. spicatum was observed but no alterations could be found in the periphytic community. In the Elodea-dominated microcosms the species composition of the periphytic algae diverged from that of the control following treatment with 0.5% spray drift emission of the label-recommended rate (5% for lambda-cyhalothrin), while reduced growth of M. spicatum in the Lemna-dominated microcosms was recorded at 2% drift (20% for lambda-cyhalothrin). This study shows that the structure of the ecosystem influences the final effect of pesticide exposure.
Fate of the insecticide lambda-cyhalothrin in ditch enclosures differing in vegetation density
Leistra, M. ; Zweers, A.J. ; Warinton, J.S. ; Crum, S.J.H. ; Hand, L.H. ; Beltman, W.H.J. ; Maund, S.J. - \ 2004
Pest Management Science 60 (2004)1. - ISSN 1526-498X - p. 75 - 84.
waterverontreiniging - lambda-cyhalothrin - sloten - insecticiden - landbouw - waterkwaliteit - ecotoxicologie - waterbodems - aquatische ecosystemen - water pollution - ditches - insecticides - agriculture - water quality - ecotoxicology - water bottoms - aquatic ecosystems
Use of the insecticide lambda-cyhalothrin in agriculture may result in the contamination of water bodies, for example by spray drift. Therefore, the possible exposure of aquatic organisms to this insecticide needs to be evaluated. The exposure of the organisms may be reduced by the strong sorption of the insecticide to organic materials and its susceptibility to hydrolysis at the high pH values in the natural range. In experiments done in May and August, formulated lambda-cyhalothrin was mixed with the water body of enclosures in experimental ditches containing a bottom layer and macrophytes (at different densities) or phytoplankton. Concentrations of lambda-cyhalothrin in the water body and in the sediment layer, and contents in the plant compartment, were measured by gas-liquid chromatography at various times up to 1 week after application. Various water quality parameters were also measured. Concentrations of lambda-cyhalothrin decreased rapidly in the water column: 1 day after application, 24-40% of the dose remained in the water, and by 3 days it had declined to 1.8-6.5%. At the highest plant density, lambda-cyhalothrin residue in the plant compartment reached a maximum of 50% of the dose after 1 day; at intermediate and low plant densities, this maximum was only 3-11% of the dose (after 1-2 days). The percentage of the insecticide in the ditch sediment was 12% or less of the dose and tended to be lower at higher plant densities. Alkaline hydrolysis in the water near the surface of macrophytes and phytoplankton is considered to be the main dissipation process for lambda-cyhalothrin.