Bijensterfte, oorzaken en gevolgen

The aim of the Danish Pesticide Leaching Assessment Programme initiated in 1998 is to monitor whether pesticides or their degradation products leach to groundwater under actual field conditions when applied in the prescribed manner. In cases where a pesticide or its degradation products leach to the groundwater the monitoring results generated by the programme should provide a basis for reassessment of the substance by the Danish Environmental Protection Agency. The programme presently evaluates the leaching risk of 40 pesticides and 27 metabolites at five agricultural sites ranging in size from 1.1 to 2.4 ha. The neonicotinoid insecticides imidacloprid and clothianidin were not included in this programme. The neonicotinoid insecticide thiamethoxam did not leach during the monitoring period (a highly significant result). Pronounced leaching was observed with the carbamate insecticide pirimicarb.

There is a growing public concern in Denmark regarding pesticide contamination of groundwater and surface waters. The Danish National Groundwater Monitoring Programme has revealed the presence of pesticides and their degradation products in approximately 30% of the monitored screens. As a result, some hundreds of abstraction wells out of about 8000 in general water supply have been closed. With this background, there is particular concern for reducing the leaching of pesticides into the groundwater.

The increasing detection of pesticides has raised doubts as to the adequacy of the existing approval procedures for pesticides. EU and hence Danish assessment of the risk of pesticide leaching to the groundwater is based mainly on data from laboratory or lysimeter studies. However, these types of data assessment do not provide satisfactory characterisation of the leaching that might occur under actual field conditions. The chemical and biological properties of soil and hydrogeology can vary significantly within as well as between fields, and climate conditions can vary during pesticide use. Furthermore, agricultural practice also varies between fields. Many of these parameters are not covered by laboratory or lysimeter studies.

The aim of the Danish Pesticide Leaching Assessment Programme initiated in 1998 is to monitor whether pesticides or their degradation products leach to groundwater under actual field conditions when applied in the prescribed manner. The programme is designed such that the findings can be evaluated in relation to the drinking water quality criterion, i.e. 0.1 microgram / L. The programme encompasses six test sites selected to represent the dominant soil types and the climatic variation in Denmark. In cases where a pesticide or its degradation products leach to the groundwater the monitoring results generated by the programme should provide a basis for reassessment of the substance by the Danish Environmental Protection Agency. The Danish counties are now obliged to identify areas where there is a particular risk of pesticide leaching, and where restrictions in the use of pesticides may be introduced to reduce the risk.

The programme presently evaluates the leaching risk of 40 pesticides and 27 metabolites at five agricultural sites ranging in size from 1.1 to 2.4 ha. The results so far show that:

Of the 40 pesticides applied, ten pesticides or their degradation products (clopyralid, chlormequat, desmedipham, florasulam, linuron, metsulfuron-methyl, thiamethoxam, tribenuronmethyl, iodosulfuron-methyl and triasulfuron) did not leach during the 1999-2008 monitoring period.

The monitoring data indicate pronounced leaching of 12 of the applied pesticides and three of their degradation products. Thus ethofumesate, bentazone, propyzamide, tebuconazole, glyphosate and its degradation product AMPA, metamitron and its degradation product metamitron-desamino, azoxystrobin and its degradation product CyPM, as well as the degradation products of metribuzine, terbuthylazine, pirimicarb and rimsulfuron, picolinafen, leached through the root zone to 1 m below ground surface (hereafter m b.g.s.) in average concentrations exceeding 0.1 µg/l. Except for the degradation products of metribuzine, rimsulfuron and terbuthylazine, leaching was mainly confined to the depth of 1 m, where pesticides were frequently detected in the samples from suction cups and drainage systems.

The monitoring data also indicate leaching of an additional 18 pesticides, in low concentrations, however. Thus, although the concentrations exceeded 0.1 µg/l in several samples, the average leaching concentrations at 1 m b.g.s. did not. Leaching was mainly confined to the depth of 1 m, where pesticides were detected in the samples from suction cups and drainage systems.

Bronnen:
Geological Survey of Denmark and Greenland 4, 25-28 (2004)
http://www.geus.dk/publications/bull/nr4/nr4_p25-28.pdf

The Danish Pesticide Leaching Assessment Programme
http://pesticidvarsling.dk/xpdf/plap1_rapport_sept-2001.pdf

Website The Danish Pesticide Leaching Assessment Programme
http://pesticidvarsling.dk/om_os_uk/uk-forside.html

Monitoring Results (1999-2008)
http://pesticidvarsling.dk/xpdf/vap-results-99-08.pdf

Powerpoint presentaties:
http://www.ust.is/ness/pest/Jeanne2.pdf
http://gammel.jordforsk.no/fagarealavr/baltic_sea/prebenolsen.ppt#263,5,... of the project