A new report from the Danish Pesticide Leaching Assessment Programme reveals that several pesticides or their metabolites are being leached from the root zone of agricultural soils.

Some pesticides continue to leach from the root zone even three years after they were first applied. That is one of the results from the monitoring programme – the Pesticide Leaching Assessment Programme (PLAP) – which covers the period from May 1999 to June 2006. The results have been published in a report prepared by the Geological Survey of Denmark and Greenland, the Faculty of Agricultural Sciences and the National Environmental Research Institute, both from the University of Aarhus.

The programme monitored 31 approved pesticides. Eleven of these pesticides or their breakdown products can be leached through the root zone (top 1 m of agricultural soil) at average annual concentrations exceeding 0.1 µg per litre, which is the threshold set by the Ministry of the Environment for carrying out further evaluations of the substances.

The report deals with the period from May 1999 to June 2006 with special emphasis on the period from July 2003 to June 2006. The new results show that:

· One metabolite of rimsulfuron has leached from the root zone for a number of years. Three years after the pesticide was applied, the metabolite continues leaching from the root zone at average annual concentrations of between 0.10 and 0.14 µg per litre.

· The compounds ethofumesate, bentazone, pendimethalin, propyzamide, metamitron and its metabolite desamino-metamitron, azoxystrobin and its metabolite CyPM, as well as the metabolites from pirimicarb have been measured in average concentrations of between 0.12 and 3.1 µg per litre. These substances have repeatedly been found below the root zone of the plants, in addition to being found less frequently and in smaller concentrations at greater depths.

Similar to previous occasions, the new results, together with other available information about the substances, will form part of the Danish Environmental Protection Agency’s overall evaluation of whether the leaching should be classed as unacceptable and therefore could give rise to a regulation on the use of the pesticides, or indeed a ban.

The breakdown products of, respectively, terbuthylazine and metribuzin have been leached from the root zone in annual average concentrations of more than 0.1 µg per litre. Metribuzin has thus already been banned, just as the use of terbuthylazine has been regulated to protect the groundwater. Propyzamide and pendimethalin will be monitored for another year, whereafter the Danish Environmental Protection Agency will reconsider their continued use.

Over the years glyphosate has been used several times in PLAP, both in early and late autumn (before or after 15th September). At three out of five late autumn applications and at one out of three early applications, the average annual concentrations were 0.1 µg per litre. Glyphosate and its metabolite AMPA have been found only sporadically in the deeper soil layers and only in low concentrations.

The average concentrations for 14 other leached substances did not exceed 0.1 µg per litre. During the monitoring period, six (clomazone, desmedipham, linuron, metsulfuron-methyl, and triasulfuron) of the 31 applied pesticides were not leached in detectable quantities.

The report (with a Danish summary) – "Danish Pesticide Leaching Assessment Programme: Monitoring results, May 1999-June 2006" – can be purchased from GEUS or downloaded from http://pesticidvarsling.dk/publ_result/index.html.

Fur further information please contact:

Academic employee Preben Olsen, Faculty of Agricultural Sciences, University of Aarhus, telephone: +45 8999 1763, e-mail: Preben.Olsen@agrsci.dk .

Senior scientist Jeanne Kjær, Geological Survey of Denmark and Greenland, telephone: +45 3814 2333