Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 412695
Title Can time-weighted average concentrations be used to assess the risks of metsulfuron-methyl to Myriophyllum spicatum under different time-variable exposure regimes?
Author(s) Belgers, J.D.M.; Aalderink, G.H.; Arts, G.H.P.; Brock, T.C.M.
Source Chemosphere 85 (2011)6. - ISSN 0045-6535 - p. 1017 - 1025.
Department(s) CWC - Environmental Risk Assessment
Wageningen Environmental Research
Publication type Refereed Article in a scientific journal
Publication year 2011
Keyword(s) aquatic plants - sulfonylurea herbicides - macrophytes - sensitivity - pesticides - toxicity - bioassays - growth - model
Abstract We tested the effects of the herbicide metsulfuron-methyl on growth of the submerged macrophyte Myriophyllum spicatum under laboratory conditions using different exposure scenarios. The exposures of each scenario were comparable in the concentration×time factor, viz., the same 21-d time-weighted average (TWA) concentrations but variable in peak exposure concentrations (ranging from 0.1 to 21000ngaiL(-1)) and exposure periods (1, 3, 7, 14 or 21d). To study recovery potential of the exposed M. spicatum plants we continued the observation on shoot and root growth for another 21d in herbicide-free medium so that the total observation period was 42d. Non-destructive endpoints, length and number of new shoots and roots, were determined weekly from day 14 onwards. Destructive endpoints, dry-weight (DW) of main shoots, new shoots and new roots, were measured at the end of the experiment (t=42d). Metsulfuron-methyl exposure in particular inhibited new tissue formation but was not lethal to main shoots. On days 21 and 42 after start exposure, EC(10)/EC(50) values for new tissues expressed in terms of peak concentration (=measured concentration during exposure periods of different length) showed large differences between exposure scenarios in contrast to EC(10)/EC(50) values for days 21 and 42 expressed in terms of 21-d and 42-d TWA concentrations, respectively. At the end of the experiment (day 42), 42-d TWA EC(x) values were remarkably similar between exposure scenarios, while a similar trend could already be observed on day 21 for 21-d TWA EC(x) values. For the macrophyte M. spicatum and exposure to the herbicide metsulfuron-methyl the TWA approach seems to be appropriate to use in the risk assessment. However, the data from the toxicity experiment suggest that on day 21 also the absolute height of the pulse exposure played a (minor) role in the exposure - response relationships observed
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