En jämförande studie mellan uppmätt och MACRO-simulerad pesticidutlakning på ett odlingsfält i Skåne
Sammanfattning: The Swedish Environmental Protection Agency (Naturvårdsverket) manages an environmental supervisor program in which they attempt to calculate the amount of pesticide leaching in various catchments in different parts of Sweden. In the present study, this kind of calculation was done for the Vemmenhög catchment in southern Sweden using the MACRO simulation model. The MACRO model is a non-steady state model of water flow and solute transport in macroporous field soils. In order to improve and validate the calculations, one field within the catchment at Näsbygård (Skåne, southern Sweden) has been investigated for soil physical properties such as the near saturated conductivity, bulk density, pF-curves, organic carbon content and soil texture. The objective was to see if there is any connection between landscape position, soil physical properties and pesticide leaching. There were some connections found between the landscape position and physical and hydraulic properties of the soil. The hilltops had the highest amount of clay, the lowest amount of organic carbon and showed the lowest near saturated hydraulic conductivity at the highest measured supply tension. The midslopes had instead the highest amount of sand and showed the highest near-saturated hydraulic conductivity at the highest measured supply tension. The hollows had the highest amount of organic carbon and the lowest near-saturated hydraulic conductivity at the lowest measured supply tension. The results from the MACRO-simulations suggest that the main leaching is from the hilltops due to a lower organic carbon content and a higher amount of clay. If the soil has a smaller amount of organic carbon this decreases pesticide sorption so that more will leach, and if the macrostructure is well developed due to a higher clay content the pesticide will bypass the soil matrix and quickly move deep into the soil. The second highest leaching was calculated for the hollows. They have a high organic carbon content but the groundwater is also at a shallow depth, which decreases the transport distance and therefore the effectiveness of attenuation processes such as degradation and sorption. These results could probably be useful in the future in attempts to calculate the amount of pesticide leaching in the whole Vemmenhög catchment (and maybe also in other similar catchments). However the predictions should first be checked for their validity in, e.g., column leaching experiments.
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