The Danish Pesticide Leaching Assessment Program – a field based, early warning system. Preben Olsen - Danish Institute of Agricultural Sciences Jeanne Kjær & Marlene Ullum - Geological Survey of Denmark and Greenland Ruth Grant - The National Environmental Research Institute

The Danish Pesticide Leaching Assessment Program – a field based, early warning system. PLAP

Institutions involved DIAS - Danish Institute of Agricultural Sciences NERI - The National Environmental Research Institute EPA - Environmental Protection Agency EPA GEUS - Geological Survey of Denmark and Greenland

98% of drinking water supplies in DK derives from ground water Pesticides and their degradation products have been detected in about 30% of all screens monitored and 10% are > 0.1 µg/l Increasing concern about pesticide contamination of the Danish groundwater: Is the existing approval procedure for pesticides sufficient? Limitations comprises: Scale problems Spatial variability of the soil parameters Hydraulic boundary condition (e.g. tile drains) Improving the current risk assessment of pesticide leaching Include field studies in the actual risk assessment Background of the project

The bottom line …is it point or difffuse sources that cause problems to our groundwater?

PLAP.. shall funtion as an early warning system..is a monitoring programme for the evaluation of pesticide leaching risk under field conditions.. has the objective to analyse, whether approved pesticides – when applied in accordance with current regulations – leach to the groundwater in unacceptable concentrations

PLAP sites - precipitation Average precipitation Source: DMI 1997

PLAP sites - soils Jyndevad Silstrup Tylstrup Slæggerup Fårdrup Estrup

PLAP - sites 2 sandy soils 4 loamy soils 1-3 ha 26 pesticides May 1999 Sep 1999 Apr 2000

Leaching of pesticides from PLAP-fields

Fine sandy soil Tylstrup

70 x 166 m 1,1 ha Loamy sand 6 % clay 2% TOC 666 mm/y Groundwater: 3-4 m.b.g.s. N 050 m M1 M2 M3 M4 M5 M6 M7 Moniteringwells P3 P6 P4 P7 P8 P5 Piezometer Rain Gauge Pt-100 S1 S2 Suction cups, TDR og

Monitoring design -crossection

Agricultural management DateProduct Dosage Potatoes planted 4. MayVar. Dianella2200 kg/ha Herbicide application25. MaySencor WGMetribuzin0,2 kg/ha 25. MayAfalonLinuron1 l/ha 7. JunSencor WGMetribuzin0,15 kg/ha Tracer application27. MayPotasium bromide30 kg/ha Fungicide application22. Jun - 14 SepDithane DGMancozeb (ETU) 10*2,0 kg/ha Irrigation 12. Sep 33 mm Harvest 28. OctActive ingedients

Agricultural management DateProduct Dosage Potatoes planted 4. MayVar. Dianella2200 kg/ha Herbicide application25. MaySencor WGMetribuzin0,2 kg/ha 25. MayAfalonLinuron1 l/ha 7. JunSencor WGMetribuzin0,15 kg/ha Tracer application27. MayPotasium bromide30 kg/ha Fungicide application22. Jun - 14 SepDithane DGMancozeb (ETU) 10*2,0 kg/ha Irrigation 12. Sep 33 mm Harvest 28. OctActive ingedients Metribuzin - Desamino-metribuzin - Diketo-metribuzin - Desamino-diketo-metribuzin

Bromide concentration - unsaturated zone

Bromide concentration - saturated zone

Pesticide concentration - suction cup S1

Average concentration - 1 m depth

Pesticide concentration in groundwater - Tylstrup -

Concentrations are due to applications at least 4-6 years ago

Pesticide concentration in groundwater Diketo-metribuzin (µg/l)

The maximum allowed concentration of 0.1 µg/l was exeeded in 36% of the samples analysed Pesticide concentration in groundwater

Desamino-diketo-metribuzin (µg/l)

Previous use of metribuzine at Tylstrup

Conclusion - Tylstrup ETU (degradation product of mancozeb) linuron or metribuzin did not leach from the root zone Diketo-metribuzin, desamino-diketo-metribuzin (degradation products of metribuzin) leached from the root zone in concentrations exceeding 0.1 µg/l. Previous application of metribuzin has caused a marked groundwater contamination with 2 degradation products The degradation products of metribuzin are quite stable.

Leaching of pesticides in PLAP

Unacceptable leaching

Leaching of glyphosate - Estrup Drainage flow, mm/d Precip.,mm/d

Leaching of glyphosate - Estrup Drainage flow, mm/dPesticide, µg/l Drainage flow, mm/d Precip.,mm/d Glyphosate, µg/l

Leaching of glyphosate - Estrup 0,54 µg/l 0,17 µg/l Precip.,mm/d Glyphosate, µg/l Drainage flow, mm/d Pesticide, µg/l AMPA, µg/l

Leaching of pesticides in PLAP No leaching Unacceptable leachingLeaching

Leaching of pesticides in PLAP Unacceptable leachingLeaching No leaching

Leaching of pesticides in PLAP Unacceptable leachingLeaching No leaching

Status after 3 years of monitoring Leaching from fields can significantly pollute groundwater with pesticides Some approved pesticides can cause significant groundwater pollution When the damage is done, pesticides can be around for several years within the groundwater

Conclusion It provides a realistic description of the leaching behaviour of pesticides under field conditions It provides essential data for the calibration/validation of the models used in the current risk assessment of pesticides leaching The PLAP monitoring programme gives an important contribution towards an improved risk assessment of pesticides leaching:

Further information is available on

Estrup - loamy soil

Sampling of drainage water Campbell logger ISCO samplers 30 o V notch Inlet Outlet Presure transducer

Geological profile -Tylstrup

Precipication 1047 mm 35% more than the yearly normal ( )

Leaching of glyphosate - Silstrup

0,12 µg/l 0,06 µg/l

Required by locations included in the PLAP (examples) Be fields in crop rotations with a size of 1-3 ha Past cultivation known for at least 10 years Undisturbed soil - no previous excavations Irrigation system (sandy soils) Room for a bufferzone Tracers could be applied (bromide) Inside an infiltration area -downward gradient A thin, unsaturated zone (shallow groundwater) A well defined groundwater table Old drainage system (loamy soils) Homogenius soil And several more……