PELMO (Pesticide Leaching Model)

PELMO is a one dimensional simulation model simulating the vertical movement of pesticides in soil by chromatographic leaching. PELMO is based on the PRZM 1 model, but was improved with regard to the requirements of the German authorities responsible for the registration of pesticides.

vertical movementpesticidessoilchromatographic leaching


contributed at 2019-12-16


Fraunhofer Institute for Molecular Biology and Applied Ecology
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Model Description

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After the release of the first version of PELMO in 1991 the runoff routines were upgraded and routines for estimating the volatilsation of pesticides were added in 1995. (version 2.01) PELMO 2.01 was validated within a joined project of the Industrieverband Agrar (IVA), the German Environmental Protection Agency and the Fraunhofer-Institut für Umweltchemie und Ökotoxikologie in Schmallenberg shared by the KfA Jülich and the SLFA Neustadt (Klein et al, 1997). In 1998 a complementary tool was added to PELMO 2.01 in order to enable the transformation of the applied a.i. to possible metabolites and to allow for further metabolism including the formation of CO2 (PELMO 3.0; Jene, 1998). Recently, additional validation tests in lysimeters and field plots have been performed (Fent et al, 1998). The PELMO version that is used for the implementation of the FOCUS-scenarios was developed in 1999 (PELMO 3.2). It was necessary to slightly change the format of the scenario data files and the handling of leap years because of the needs of the FOCUS-scenarios. A number of changes were also made in the output routines to make sure that the present version of FOCUSPELMO is echoed in the output according the decisions of the Focus version control group. Minor changes were also made in the routine that is estimating soil temperatures based on air temperatures to make sure that the results are correct also for soil depths below 1.0 m. Finally, the runoff routine in PELMO was c alibrated based on field experiments by introducing a new parameter in the model (“fraction of soil water available for runoff”).

Table 1 Summary of the processes in PELMO. [* = turned off for the FOCUS scenarios]



Process Approach
water movement capacity-based water flow (tipping bucket approach) using a daily time step for all hydrological processes, preferential flow and capillary rise are not considered
pesticide movement convection dispersion equation based on a daily time step
crop simulation changing root zone during growing season, changing foliage (areal extent) during growing season, crop interception of water*, crop interception of pesticides*, foliar washoff*, foliar degradation*
degradation in soil first order degradation rate, correction of rate constant with depth, soil moisture and soil temperatures
pesticide sorption to soil Kd, Koc, Freundlich equation for sorption option for increase of sorption with time option for automated pH-dependence*
pesticide volatilization (from soil) simple model using Fick’s and Henry’s law
runoff Soil Conservation Service curve number technique
soil erosion* Modified Universal Soil Loss Equation
soil temperature an empirical model that uses air temperatures
plant uptake simple model based on soil concentrations
pesticide applications applications may be foliar sprays, applied to the soil surface, or incorporated into the soil; for soil incorporated applications a variety of soil distributions can be specified
metabolism a sophisticated scheme with up to 8 metabolites (A -> B as well as A -> B <> C) may be simulated simultaneously with the parent



Role and Place in FOCUS scenarios calculation

The major objective of FOCUS is to implement a harmonised approach for European Tier 1 risk assessments according to Council Directive 91/414/EEC. The process implementation of each model was adjusted and harmonised scenario definitions were implemented in windows shells around the individual simulation models. Similar to PRZM PELMO has advantages in a computer environment with limited hardware recourses. On standard PCs (e.g. Pentium III, 400 MHz, 64 MB) the typical computing time for a standard Tier 1 run with 9 scenarios is about 5 to 10 minutes. FOCUSPELMO allows efficient and user friendly calculations for compounds up to eight metabolites.

Current use outside FOCUS

PELMO is offically used by the Umweltbundesamt (UBA, the German Environmental Protection Agency, and the Biologische Bundesanstalt (BBA, Federal Biological Research Centre, to assess the leaching potential of pesticides within the registration process in Germany for about ten years. Special scenarios describing the German climate and soil conditions are used for this purpose. It is possible to do PELMO simulations according to the German procedure using FOCUSPELMO as all necessary input files are provided within the FOCUSPELMO package.

Excerpt of existing model documentation

Model documentation

  • Anderson, E.A. (1978): Initial Parameter Values for the Snow Accumulation and Ablation Model. Part IV.2.2.1, National Weather Service River Forecast System - User's Manual, NWS/NOAA, U.S. Dept. of Commerce, Silver Springs, MD., March 31, 1978.
  • Carsel, R.F., C.N. Smith, L.A. Mulkey, J.D. Dean, and P. Jowise (1984).  User's manual for the pesticide root zone model (PRZM): Release 1.  EPA-600/3-84-109.  U.S. EPA, Athens, GA.
  • Haith, D.A., and R.C. Loehr (Eds.) (1979):  Effectiveness of Soil and Water Conservation Practices for Pollution Control.  U.S. Environmental Protection Agency, Athens, GA.  EPA-600/3-79-106.
  • Jene, B. (1998): PELMO 3.00 Manual extension, Staatliche Lehr- und Forschungsanstalt für Landwirtschaft, Weinbau und Gartenbau, D-67435 Neustadt/Wstr.
  • Klein, M.: PELMO(1995): Pesticide Leaching Model, User manual version 2.01. Fraunhofer-Institut für Umweltchemie und
  • Ökotoxikogie, D57392 
  • OECD (1997):  Approved draft proposal for an updated OECD guideance document No. 106: Adsorption/Desorption. OECD Guidlines for Testing of Chemicals, 1-44.
  • PRZM 2.0 and 3.12 manuals.

References for PELMO applications

  • Fent, G., B. Jene and R. Kubiak (1998). Performance of the Pesticide Leaching Model PELMO 2.01 to predict the leaching of bromide and 14C-Benazolin in a sandy soil in comparison to results of a lysimeter- and field study. Staatliche Lehr- und Forschungsanstalt für Landwirtschaft, Weinbau und Gartenbau (SLFA) Neustadt. Poster Abstract 6B-030, IUPAC Congress Book of Abstracts, London 1998
  • Hassink, J., Klein, M., Klein A. and W. Kördel (1993): Fate of Herbicides in Soils under Different Types of Land use. BCPC 827-834
  • Klein M. (1994), Evaluation and Comparison of Pesticide Leaching models for Registration Purposes, Results of Simulations performed with the Pesticide Leaching Model, Journal of Environmental Science  & Health, A29(6),1197-1209 (1994)
  • Klein M. (1997), Statistical distribution of pesticide concentrations in leachate - results of a Monte-Carlo analysis performed with PELMO, Chemosphere, 35, 379-389
  • Klein M. (1998): Comprehensive tracer studies on the environmental behaviour of pesticides: the lysimeter consept in F. Führ, R.J. Hance, J.R. Plimmer, J.O. Nelson (eds.), ACS Symposium series 699, 246-258, Washington.
  • Klein M. (1999):Monte-Carlo Analysis Using Pesticide Fate Models, J. Pesticide Sci. 24, 55-59.
  • Klein, M. and H. Klöppel (1993), Usefulness of models for the prediction of run-off events - comparison with experimental data, The science of the Total Environment, Supplement.
  • Klein, M., Hosang, J., Schäfer, H., Erzgräber, B., Resseler, H. (2000): Comparing and evaluating pesticide leaching models. Results of simulations with PELMO, Agricultural Water Management 44 (1-3) (2000) pp. 263-281
  • Klein, M., Müller, M., Dust, M., Görlitz, G., Gottesbüren, B., Hassink, J., Kloskowski, R., Kubiak, R., Resseler, H., Schäfer, H., Stein B. and H. Vereecken (1997), Validation of the pesticide leaching model PELMO using lysimeter studies performed for registration, Chemosphere 35 No 11, 2563-2587.

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How to Cite

Michael Klein (2019). PELMO (Pesticide Leaching Model), Model Item, OpenGMS,

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