Testing MACRO (version 5.1) for pesticide leaching in a Dutch clay soil

• Published in: Pest management science Vol. 63; no. 10; pp. 1011 - 1025
• Main Authors: Scorza Júnior, Rômulo P, Jarvis, Nicholas J, Boesten, Jos JTI, van der Zee, Sjoerd EATM, Roulier, Stéphanie
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-10-2007; Wiley; Wiley Subscription Services, Inc
• Subjects: Agronomy. Soil science and plant productions; Aluminum Silicates - analysis; bentazon; Benzothiadiazines - analysis; Biological and medical sciences; Bromides - analysis; Calibration; clay soils; Comparative analysis; computer software; environmental models; field soils; flow; Fundamental and applied biological sciences. Psychology; groundwater contamination; Hot Temperature; hydraulic conductivity; imidacloprid; Imidazoles - analysis; insecticide residues; Leaching; MACRO; MACRO model; MACRO software; macropore flow; mathematical models; model description; Models, Chemical; Neonicotinoids; Nitro Compounds - analysis; pesticide leaching; pesticide residues; Pesticides; Pesticides - analysis; Phytopathology. Animal pests. Plant and forest protection; porous-media; preferential flow; scale; Simulation; simulation models; Soil - analysis; Soil and water pollution; Soil science; Soils; solute transport; water; Water - analysis; Netherlands; Europe; Western Europe; Pesticides; MACRO; Clay soil; Water pollution; Simulation model; Preferential flow; Leaching; pesticide leaching; groundwater contamination; Ground water
• ISSN: 1526-498X; 1526-4998
• DOI: 10.1002/ps.1434

Testing of pesticide leaching models against comprehensive field-scale measurements is necessary to increase confidence in their predictive ability when used as regulatory tools. Version 5.1 of the MACRO model was tested against measurements of water flow and the behaviour of bromide, bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one-2,2-dioxide] and imidacloprid [1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine] in a cracked clay soil. In keeping with EU (FOCUS) procedures, the model was first calibrated against the measured moisture profiles and bromide concentrations in soil and in drain water. Uncalibrated pesticide simulations based on laboratory measurements of sorption and degradation were then compared with field data on the leaching of bentazone and imidacloprid. Calibrated parameter values indicated that a high degree of physical non-equilibrium (i.e. strong macropore flow) was necessary to describe solute transport in this soil. Comparison of measured and simulated bentazone concentration profiles revealed that the bulk of the bentazone movement in this soil was underestimated by MACRO. Nevertheless, the model simulated the dynamics of the bentazone breakthrough in drain water rather well and, in particular, accurately simulated the timing and the concentration level of the early bentazone breakthrough in drain water. The imidacloprid concentration profiles and its persistence in soil were simulated well. Moreover, the timing of the early imidacloprid breakthrough in the drain water was simulated well, although the simulated concentrations were about 2-3 times larger than measured. Deep groundwater concentrations for all substances were underestimated by MACRO, although it simulated concentrations in the shallow groundwater reasonably well. It is concluded that, in the context of ecotoxicological risk assessments for surface water, MACRO can give reasonably good simulations of pesticide concentrations in water draining from cracking clay soils, but that prior calibration against hydrologic and tracer data is desirable to reduce uncertainty and improve accuracy. Copyright © 2007 Society of Chemical Industry