Parameter estimation of a plant uptake model for cyanide: application to hydroponic data

Area of Science:

• Environmental Science
• Plant Physiology
• Bioremediation

Background:

• Cyanide contamination poses environmental risks.
• Phytoremediation offers a sustainable solution for pollutant removal.
• Understanding plant uptake mechanisms is crucial for optimizing phytoremediation.

Purpose of the Study:

• To model the transport and fate of free cyanide and ferrocyanide in willow plants.
• To determine key parameters influencing cyanide uptake and phytoremediation efficiency.
• To assess the applicability of saturation kinetics for cyanide uptake.

Main Methods:

• A plant uptake model was applied to experimental data from hydroponically grown willow (Salix eriocephala var. Michaux).
• Least-squares optimization was used to determine best-fit parameter values and their uncertainty.
• Model sensitivity analysis was performed to identify important parameters for field-scale applications.

Main Results:

• Volatilization and cell wall adsorption of free cyanide were negligible.
• Maximum uptake rate for free cyanide and leaf loss rate for noncyanide 15N were significant.
• Saturation kinetics may apply to free cyanide uptake, but not ferrocyanide uptake.
• The model accurately predicted most observed data, except for underestimated stem and leaf assimilate concentrations.

Conclusions:

• Willow plants actively play a role in free cyanide uptake, potentially via preferential diffusion.
• Noncyanide 15N redistribution in phloem should be considered for improved model accuracy.
• The findings support the potential of willow phytoremediation for cyanide-contaminated sites.