Interactions, Transformations, and Bioavailability of Nano-Copper Exposed to Root Exudates

Area of Science:

• Environmental Science
• Soil Science
• Nanotechnology

Background:

• Engineered nanomaterials (ENMs) are increasingly released into soil systems.
• Understanding ENM interactions with plants is crucial due to potential bioavailability and effects.
• Plant root exudates play a significant role in the fate of ENMs in soil.

Purpose of the Study:

• To investigate the influence of root exudates on the fate of nanocopper (nCu) from a thermodynamic perspective.
• To determine thermodynamic parameters for interactions between nCu, synthetic root exudate (SRE), and its components.
• To understand the impact of these interactions on copper uptake and bioaccumulation in plants.

Main Methods:

• Nano isothermal titration calorimetry (nITC) was used to measure thermodynamic parameters.
• Interactions were studied between nCu and SRE (sugars, organic acids, amino acids, phenolic acids), and between Cu²⁺ and SRE.
• Plant-nCu exposure experiments were conducted.

Main Results:

• Strong interactions were observed between nCu and SRE (Kd = 5.645 × 10³ M⁻¹), and between Cu²⁺ and SRE (Kd = 7.181 × 10⁴ M⁻¹).
• nCu dissolution was the predominant interaction in the presence of SRE.
• SRE induced complex transformations of nCu, forming Cu²⁺, Cu⁺, and Cu⁰.
• SRE binding significantly decreased Cu uptake and bioaccumulation in plants.

Conclusions:

• Nano isothermal titration calorimetry provides fundamental thermodynamic insights into nCu-root exudate interactions.
• Root exudates significantly alter the fate and bioavailability of nanocopper in soil.
• This understanding is vital for assessing the environmental impact of ENMs on crop plants.