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The occurrence and influence of deep biopores on pesticide leaching from land surface to chemically reduced ground water in glacial clayey till

Project: Research

  • Jørgensen, Peter R (Project coordinator)
  • Spliid, Niels Henrik (Participant)
  • Hansen, Søren (Participant)
  • Petersen, Carsten T. (Participant)
  • Krogh, Paul Henning (Project manager)
  • Nielsen, Marie Habekost (Participant)
  • Pesticide Research and Environmental Chemistry
  • Department of Terrestrial Ecology
  • PJ-Bluetech v. M.E.C. Holding Aps.
  • University of Copenhagen
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Groundwater resources in Denmark are influenced by leaching pesticides from cities and agriculture. One of the main routes pesticide-leaching are cracks and large biological pores (biopores) in glacial till, that covers about 40% of groundwater. Fractures incidence is generally well known, as are biopores in the top 1 to 2 meters of soil (root zone). However, there is very limited knowledge about the role of biopores below the root zone and towards the groundwater. The available few but well-documented studies show that that large biopores, possibly root canals from former forest cover, may follow deep cracks from the last ice age and present very effective pathways for pesticide leaching to groundwater. This leaching may potentially represent a large groundwater risk, particularly if the deep root canals is directly connected to the root and worm burrows continuously formed in the root zone which can cause short circuits between pesticide leaching in the field and the underlying groundwater. It is unknown to what extent this short circuit occurs at ordinary moraine soils and groundwater represents a potential risk as a very quick route of pesticide transportation to the groundwater.
The project will answer this question by examining the occurrence and correlation with the active formation of biopores due to earthworms (and roots) in the root zone. The project investigates the role of the deep biopores as fast pesticide transport routes from the soil surface, passing the microbiologically active root zone and then to chemically reduced groundwater till. Leaching of recently chemically reduced groundwater is important because most pesticides in this environment degrades very slowly, creating the basis for a retransmission of the entire groundwater system if pesticides leaches from the surface and from point sources.
The project investigates pesticide transport pathways through the soil column by pumping colored gas into 20 m long horizontal wells about 3.5 below ground level and map where the gas comes up through the field macropores. Then infiltrated pesticides and color tracers on field surface of the wells and made measurements of leaching to the underlying horizontal wells. After these tests excavated infiltration fields down to the wells and transport routes mapped using the tracks after they infiltrated color tracers. Including also conducted a basic study of earthworms and roots digging activity and penetration depth and whether these form the contact to the deep root canals in the crevices below the root zone. Apart from the mapping of transport routes in the field and in the excavations compared the probability of hitting pesticide transport routes, respectively. horizontal and vertical monitoring wells and on this basis, the risk of overlooking pesticide leaching in the deep biopores with these types of drilling, especially where vertical wells are used as monitoring wells in pesticide warning and pollution studies (point and area sources). Finally built project's accumulated knowledge about the deep biopores spatial occurrence and their functionality as pesticide transport pathways to groundwater in a mathematical pesticide leaching model (Daisy2D) used to perform scenario calculations of pesticide leaching to field drains and underlying groundwater for typical Danish conditions on clay soils.
Effective start/end date01/09/201131/12/2015

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Research outputs

ID: 128935541