Report from the Danish Pesticide Leaching Assessment Programme (PLAP) for the period 1999-2004

06-12-2005

The latest results from the PLAP shows that 8 out of 29 approved pesticides, or their metabolites, can leach from the root zone (approx. 1 m depth) in average concentrations exceeding 0.1 µg L-1, which is the EU threshold for drinking water. Metabolites are formed when a pesticide is degraded by, for example, soil microbes.

The results in the report comprise the period May 1999 to June 2004 with special emphasis on the period from July 2002 to June 2004. The results will be included in the Danish Environmental Protection Agency's assessment of whether the pesticides pose an unacceptable environmental risk. The eight pesticides contain the active ingredients rimsulfuron, terbuthylazine, glyphosate, metribuzin, bentazone, metamitron, ethofumesate and pirimicarb.

  • For the first time ever, a rimsulfuron metabolite has been found leached at levels exceeding the threshold. The average concentrations ranged between 0.10 and 0.12 µg L -1 in water sampled at 1 m depth on a sandy soil cropped with potatoes. The substance will be monitored for an additional year. It is then for the Danish Environmental Protection Agency to assess the need for regulations.
  • Four active ingredients, bentazone, metamitron, ethofumesate and pirimicarb, were found in concentrations averaging from 0.12 to 1.1 µg L -1 in drainage water. These substances will also be monitored for an additional year before the Danish Environmental Protection Agency assesses the need for regulations.
  • Glyphosate was applied to a loamy soil at the beginning of September and the subsequent leaching to the drainage system was significantly below the threshold value. The leaching of glyphosate as affected by time of application - before and after 15 September - has been investigated in PLAP in recent years. Two out of four late autumn applications caused leaching above the threshold value, whereas this happened in only one out of three cases with early autumn applications. These findings did not give rise to any restrictions in the use of glyphosate.
  • Metabolites of terbuthylazine and metribuzin have leached from the root zone (1 m b.g.s.) at levels exceeding the threshold of 0.1 µg L -1 . The metabolites of metribuzin have leached to greater depth, where average groundwater concentration exedeed 0.1 µg/l. Metribuzin has now been banned and the use of terbuthylazine has been regulated.

The average concentrations of 14 additional leached substances did not exceed 0.1 µg L-1. Seven of the 27 substances were not found in measurable concentrations during the monitoring period. The most recent results are described in the report: "The Danish Pesticide Leaching Assessment Programme: Monitoring results, May 1999-June 2004". The report is in English and can be purchased from the Geological Survey of Denmark and Greenland (GEUS) or downloaded from: www.pesticidvarsling.dk

For further information please contact:
Scientist Jeanne Kjær, GEUS. Tel.: +45 38 14 23 33.
Academic employee Preben Olsen, DIAS. Tel.: +45 89 99 17 63.

The report has been issued by: The Geological Survey of Denmark and Greenland (GEUS), The Danish Institute of Agricultural Sciences (DIAS) and The National Environmental Research Institute (NERI).