Abstract
Pesticides that persist in soils may be taken up by the roots of plants. One way to assess plant uptake is to theoretically predict the extent of plant uptake using a mathematical model. In this study, a model was developed to predict plant uptake of pesticide residues in soils using various parameters, such as pesticide mobility within soil, plant transpiration stream, root–soil transfer rate, plant growth, and pesticide dissipation in either soils or plants. The accuracy of the model was evaluated by comparing the modeled concentrations with measured uptake concentrations of chlorpyrifos (CP) in lettuce, grown on treated soils with concentrations of approximately 10 and 20 mg kg-1 CP. Measured concentrations of CP in lettuce at 21, 30, and 40 d after planting were between the 5th and 95th percentiles of model variation. A high correlation coefficient of > 0.97 between modeled and measured concentrations was found. Coefficients of variation of mean factors to residual errors were between 25.3 and 48.2%. Overall, modeling results matched the experimental results well. Therefore, this plant uptake model could be used as an assessment tool to predict the extent of plant uptake of pesticide residues in soils.
Highlights
Many studies have shown that theoretical prediction from mathematical models can assess the extent of plant uptake of hazardous substances, such as heavy metals and organic pollutants persistent in soil [1,2,3,4,5,6]
Plant uptake models for pesticides that persist in soils are based mainly on a bioconcentration factor (BCF) that indicates the ratio of pesticide concentrations in the plant and soil [10]
Total ion chromatogram and mass spectrum of CP identified by gas chromatography-mass spectrometer (GC-MS) are shown in S1 Fig. The mass spectrum of CP shared > 93% similarities with the mass spectral library data provided by the National Institute of Standards and Technology (NITS)
Summary
Many studies have shown that theoretical prediction from mathematical models can assess the extent of plant uptake of hazardous substances, such as heavy metals and organic pollutants persistent in soil [1,2,3,4,5,6]. Unlike heavy metals, it is difficult to develop a plant uptake model for organic chemicals, as their dissipation behaviors might be consistent or variable, depending on environmental conditions. Shone and Wood [11] introduced the root concentration factor (RCF) to demonstrate the relationship between concentrations of pesticides in root and soil solutions. Thereafter, they defined the transpiration stream concentration factor (TSCF) that indicates the ratio of PLOS ONE | DOI:10.1371/journal.pone.0172254. Thereafter, they defined the transpiration stream concentration factor (TSCF) that indicates the ratio of PLOS ONE | DOI:10.1371/journal.pone.0172254 February 17, 2017
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