Soil dissolved organic matter affects mercury immobilization by biogenic selenium nanoparticles

Area of Science:

• Environmental Chemistry
• Soil Science
• Nanotechnology

Background:

• Dissolved organic matter (DOM) in soil exhibits molecular weight (MW) heterogeneity.
• DOM-nanoparticle interactions are crucial for environmental fate and bioremediation.
• Selenium nanoparticles (SeNPs) are engineered nanomaterials with potential applications and environmental implications.

Purpose of the Study:

• To investigate the influence of DOM molecular weight fractions on selenium nanoparticle (SeNP) adsorption.
• To evaluate the effect of DOM-SeNP interactions on elemental mercury immobilization.
• To understand the role of DOM's molecular weight in governing SeNP fate and mercury bioremediation.

Main Methods:

• Extraction and fractionation of DOM from black soil into distinct MW ranges (e.g., >10,000 Da, 3500-10,000 Da, 1000-3500 Da, 100-1000 Da).
• Assessment of SeNP homoaggregation and fluorescence quenching titration in the presence of different DOM fractions.
• Evaluation of elemental mercury immobilization mediated by DOM-SeNP complexes.

Main Results:

• Intermediate MW DOM fractions (3500-10,000 Da) showed preferential adsorption to SeNPs over high MW fractions.
• Adsorbed DOM, particularly intermediate MW fractions, enhanced SeNP stability.
• Enhanced SeNP stability facilitated improved immobilization of elemental mercury.

Conclusions:

• Molecular weight of DOM significantly impacts its binding affinity to SeNPs.
• Preferential adsorption of intermediate MW DOM influences SeNP stability and aggregation.
• DOM-SeNP interactions mediated by MW are critical for effective mercury bioremediation using SeNPs.