Article

Biogeochemistry

, Volume 117, Issue 1, pp 185-204

First online:

Micro-scale modeling of pesticide degradation coupled to carbon turnover in the detritusphere: model description and sensitivity analysis

  • Holger PagelAffiliated withInstitute of Soil Science and Land Evaluation, Biogeophysics, University of Hohenheim Email author 
  • , Joachim IngwersenAffiliated withInstitute of Soil Science and Land Evaluation, Biogeophysics, University of Hohenheim
  • , Christian PollAffiliated withInstitute of Soil Science and Land Evaluation, Soil Biology, University of Hohenheim
  • , Ellen KandelerAffiliated withInstitute of Soil Science and Land Evaluation, Soil Biology, University of Hohenheim
  • , Thilo StreckAffiliated withInstitute of Soil Science and Land Evaluation, Biogeophysics, University of Hohenheim

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Abstract

Microbiologically active biogeochemical interfaces are excellent systems to study soil functions such as pesticide degradation at the micro-scale. In particular, in the detritusphere pesticide degradation is accelerated by input of fresh organic carbon from litter into the adjacent soil. This observed priming effect suggests: (i) pesticide degradation is strongly coupled to carbon turnover, (ii) it is controlled by size and activity of the microbial community and (iii) sorption and transport of dissolved carbonaceous compounds and pesticides might regulate substrate availability and in turn decomposition processes. We present a new mechanistic 1D model (PEsticide degradation Coupled to CArbon turnover in the Detritusphere, PECCAD) which implements these hypotheses. The new model explicitly considers growth and activity of bacteria, fungi and specific pesticide degraders in response to substrate availability. Enhanced pesticide degradation due to availability of a second source of carbon (dissolved organic carbon) is implemented in the model structure via two mechanisms. First, additional substrate is utilized simultaneously with the pesticide by bacterial pesticide degraders resulting in an increase in their size and activity. Second, stimulation of fungal growth and activity by additional substrates leads directly to higher pesticide degradation via co-metabolism. Thus, PECCAD implicitly accounts for litter-stimulated production and activity of unspecific fungal enzymes responsible for co-metabolic pesticide degradation. With a global sensitivity analysis we identified high-leverage model parameters and input. In combination with appropriate experimental data, PECCAD can serve as a tool to elucidate regulation mechanisms of accelerated pesticide degradation in the detritusphere.

Keywords

Soil organic matter Mechanistic model Biogeochemical interface Priming effect Carbon isotopes Gene abundance