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New report from the unique Danish Pesticide Leaching Assessement Program (PLAP)

Results from this year's PLAP report show that the majority of the tested pesticides and degradation products in the period 2017-2019 did not leach into the groundwater when used correctly. Of the 32 substances tested, two substances - the pesticide propyzamide and the degradation product 1,2,4-triazole - were found in the groundwater above the requirement value of 0.1 μg / L.

2021.01.13 | Camilla Brodam

Photo: Jesper Rais

The new report from the Danish Pesticide Leaching Assessment Programme (PLAP) focuses on the period from July 2017 to June 2019, where 15 pesticides were sprayed on one or more PLAP fields to test the leaching of selected pesticides and degradation products. In total, the leaching risk of seven pesticides and 25 degradation products was evaluated. Water samples from drains and suction cells at a depth of one meter as well as the upper groundwater were analysed for their content of the 32 substances.

Three pesticides (bentazone, glyphosate, and propyzamide) and four degradation products of pesticides (CyPM, E / Z BH 517-TSO, AMPA, and 1,2,4-triazole) were found in water from drains and suction cells at a depth of one meter in concentrations above 0.1 μg / L, which is the maximum value applicable to ground- and drinking water. All of the seven substances were also found in the groundwater, but propyzamide (used for, among other things, weed control in winter oilseed rape) and 1,2,4-triazole (derived from various azole-type fungicides used for, among other things, grain) were found as the only two substances in groundwater samples in concentrations above the requirement value. Out of the 32 substances tested, one pesticide and 19 degradation products were not found in samples from groundwater, drains or suction cells at a depth of one meter. In addition, four substances were found in drainage water or suction cells at a depth of one meter, but not in groundwater or vice versa in groundwater, but not in drainage water and suction cells. One pesticide was found in both at a depth of one meter and in the groundwater. For all five substances, however, the measured values ​​were below 0.1 μg / L.

The results show that propyzamide leached briefly through cracked clay soil, in contrast to sandy soil, where a previous test has not shown leaching. The degradation product 1,2,4-triazole is still found to varying degrees in the groundwater below the six monitored VAP fields regardless of soil type. Especially on one of the cracked clay fields, the substance was found above the requirement value in 65 out of 255 groundwater samples. Here, the findings cannot be directly related to a specific azole application in the form of a spray or pickling agent. In a research project, funded by the Danish Environmental Protection Agency, it is therefore now being investigated whether there is a connection between the presence of 1,2,4-triazole in the groundwater and the accumulation of azole agents in the topsoil.

What is PLAP?

The Danish Pesticide Leaching Assessment Programme (PLAP) has been in operation since 1999 and has, on behalf of the Danish government, provided results on the risk of leaching of selected pesticides and degradation products from fields in Denmark. 

The fields represent different types of climate, geology, and soil in Denmark - including sandy fields and cracked clay fields and are located in areas with different climates. All fields are grown conventionally and sprayed with selected, approved pesticides in maximum permitted dosages.

Over the years, a total of 130 substances have been tested for leaching, of which 51 are pesticides and 79 are degradation products from the pesticides used. The results, which are compiled in this year's report, provide unique knowledge and documentation on the transport of pesticides and their degradation products through the soil and down to the groundwater under real field conditions.

The knowledge and documentation collected in PLAP is used in the authorities' work to protect our groundwater. Similar information cannot be obtained through laboratory tests or the leaching models used in the regulation of pesticides at both national and European level.

Read summary and report here

PLAP is funded through Pesticide Strategy 2017-2021. The results from PLAP are for the period 1999-2019 described in a series of reports prepared by the National Geological Survey of Denmark and Greenland (GEUS) together with the Department of Agroecology and the Department of Bioscience at Aarhus University.

The Danish summary ‘’Varslingssystemet for udvaskning af pesticider til grundvand. Moniteringsresultater juli 2017-juni 2019’

The overall report ‘Danish Pesticide Leaching Assessment Program: Monitoring Results May 1999 - June 2019’. 

PLAP reports from all years can be found at http://pesticidvarsling.dk.

Behind the research
Collaborators: Department of Agroecology at Aarhus University, Department of Bioscience at Aarhus University, and the National Geological Survey of Denmark and Greenland (GEUS)
Financing: PLAP is financed via Pesticide Strategy 2017-2021
Conflicts of interest: None
The article here is produced in collaboration with all collaborators who have had possibility to read and comment on the content

Contact:

Project manager and senior researcher Annette E. Rosenbom, The National Geological Survey of Denmark and Greenland (GEUS), telephone 91333552 and e-mail: aer@geus.dk 

Academic staff member Preben Olsen, Department of Agroecology, Aarhus University, telephone 21730711 and e-mail: preben.olsen@agro.au.dk

Research, Agro, DCA