Metaldehyde Aquatic Half-Life Data

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I am researching the behaviour of micro-pollutants in surface waters and drinking water treatment systems. 

I am currently reviewing data for a number of surface water resources impacted by metaldehyde. I am unable to find any reliable data relating to the half-life of metaldehyde (hydrolysis and photolysis).

Does anyone have any data that could aid me? Or perhaps any working assumptions they make when determining the probable half-life of metaldehyde, for instance when modelling the persistence of metaldehyde in an impounding reservoir?

Thanks in advance.

Taxonomy

4 Answers

  1. Dear Adam,

    Metaldehyde is a white-colored crystalline solid. It is insoluble in water. It is highly flammable and when ignited will give off irritating fumes. It may be toxic by ingestion and is very irritating to skin and eyes. It is used to make other chemicals. About Biological Half-life, the urinary excretion of metaldehyde was less than 1% of the dose ... Elimination half-life is 27 hr . Vapor-phase metaldehyde will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 13 hours. Metaldehyde does not contain chromophores that absorb at wavelengths >290 nm and therefore is not expected to be susceptible to direct photolysis by sunlight. If released to soil, metaldehyde is expected to have moderate mobility based upon a measured Koc of 240. Volatilization from moist soil surfaces is expected to be an important fate process based upon an estimated Henry's Law constant of 5.2X10-5 atm-cu m/mole. Metaldehyde is not expected to volatilize from dry soil surfaces based upon its vapor pressure. A reported half-life of approximately 2 months in soil suggests that biodegradation is not an important environmental fate process in soil; microbiological decomposition of metaldehyde in soil proceeds to carbon dioxide and water. If released into water, metaldehyde is not expected to adsorb to suspended solids and sediment based upon the measured and estimated Koc values. Utilizing the Japanese MITI test, a 0% of theoretical BOD in four weeks suggests that biodegradation is not an important environmental fate process in water. Volatilization from water surfaces is expected to be an important fate process based upon this compound's estimated Henry's Law constant. Estimated volatilization half-lives for a model river and model lake are 26 hours and 12 days, respectively. An estimated BCF of 3.2 suggests the potential for bioconcentration in aquatic organisms is low. Hydrolysis is expected to be an important environmental fate process since this compound contains functional groups that hydrolyze under environmental conditions. Occupational exposure to metaldehyde may occur through inhalation of dust and dermal contact with this compound at workplaces wheremetaldehyde is produced or used. The general population can be exposed to metaldehydeused as a molluscicide as a result of both application and post-application activities, on a short term exposure basis.Under anaerobic conditions, the half-life of metaldehyde has been reported as greater than 200 days

  2. Rather than metabolic half-life, I think Adam is asking about degradation in the natural environment. It is common experience that metaldehyde is highly persistent in impounding reservoirs, and I would think a half-life of several months would be a minimum in UK waters.

    1 Comment

    1. Thanks Rob. That has been my assumption up until now, but its good to have confirmation. 

  3. The elimination half-life of metaldehyde is 27 hours, if treating an animal for exposure it could take up to 4 days. CH3CHO)4 is the usual source of this pesticide  against gastropods. I have used Ozone to treat for this contaminant with good results. 

  4. Has a half life of only a few days according to Toxipedia. Hydrolyses to acetaldehyde, then oxidizes to acetic acid.