The equilibria of bisolute sorption on soil

Area of Science:

• Environmental Chemistry
• Soil Science
• Adsorption Science

Background:

• Understanding mixed organic pollutant sorption on soils is crucial for environmental risk assessment.
• Sorption behavior can be influenced by pollutant concentrations and their loading sequence.

Purpose of the Study:

• To investigate the effects of concentration and loading sequence on mixed organic pollutant sorption equilibria.
• To determine how contamination history influences competitive sorption between phenanthrene and naphthalene on soil.

Main Methods:

• Measured binary sorption equilibria for phenanthrene and naphthalene on soil across ten concentration levels.
• Investigated simultaneous and sequential loading scenarios to simulate different contamination histories.
• Compared experimental results with predictions from the Ideal Adsorbed Solution Theory (IAST).

Main Results:

• Naphthalene sorption was consistently lower in the presence of phenanthrene, regardless of loading order.
• Phenanthrene sorption equilibria were dependent on the loading sequence, showing significant competition when the soil was pre-contaminated.
• IAST predictions showed discrepancies, particularly for phenanthrene sorption under specific sequential loading conditions.

Conclusions:

• Contamination history, specifically pre-contamination, plays a critical role in the competitive sorption of organic pollutant mixtures.
• The complex sorption behavior may be attributed to adsorption within ink-bottle shaped pores of the soil matrix.
• Current models like IAST may require refinement to accurately predict mixed pollutant sorption dynamics influenced by historical contamination.