Abstract
To address the soil–plant transfer modelling of 13 US-EPA Polycyclic Aromatic Hydrocarbons (PAHs), a mechanistic model—MM_19—has been developed based on the fugacity concept. For that, the Mackay_97 model has been improved in terms of reconsidering the losses related to the transport and transformation mechanisms taking place in the compartments—roots and aboveground shoots—of the three short-life species (Eleusine indica, Cynodon dactylon and Alternanthera sessilis). Model input parameters consist of both experimental and literature data, including the initial soil and air PAHs content, flowrates, PAHs physico-chemical properties, retention times and transport half-lives of PAHs inside plant species. Using in situ weather data and Penman’s law, xylem flows were estimated as the evapotranspiration for each plant. Model calibration was performed using a Generalized Reduced Gradient (GRG) nonlinear optimization solver method. Sensitivity analysis showed that the phloem flow was the most sensitive among all tested parameters. According to the Nash–Sutcliffe efficiency (NSE), the MM_19 model is more efficient than the Mackay_97 model for all three plant species. Finally, the impact of PAHs physico-chemical parameters on their sol-plant transfer was discussed in terms of slight, intermediate and high molecules weight. The NSE values showed that the MM_19 model is more efficient than the Mackay_97 model. Indeed, comparisons between experimental and simulated results in the MM_19 model showed similarities for each compartment of the plant species. Thus, the MM_19 model can be used to predict the soil–plant transfer of organic pollutants.
Highlights
Soil–plant transfers of organic pollutants depend on the physico-chemical properties of the molecules under consideration and on the physiological processes involved in plant development [1]
There are some dynamic mechanistic models which integrate the physiological characteristics of plants, as well as the exchanges that can occur between plant and their environment
The sensitivity analysis shows that changes in the α factor have the greatest influence on the model (Table S4, Supplementary Material E)
Summary
Soil–plant transfers of organic pollutants depend on the physico-chemical properties of the molecules under consideration and on the physiological processes involved in plant development [1]. The goal of modelling organic pollutants in plants is to predict the kinetics and balance (of the extraction of these pollutants by species at different times) [2,3]. Both empirical and mechanistic models are usually used. Empirical models are based on statistical relationships and do not consider the physiological characteristics of the plant, nor the exchanges between compartments of the environment [4]. Bioconcentration factors, regression equations, root concentration factor, partition coefficients and translocation factors have been established to predict the transfer of organic pollutants from soil to plant compartments [3]. There are different types of models, such as the one
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