Organic compound distribution between nonionic surfactant solution and natural solids: applicability of a solution...

Area of Science:

• Environmental Chemistry
• Soil Science
• Physical Chemistry

Background:

• Organic compounds in soil pose risks to groundwater quality.
• Understanding contaminant partitioning is crucial for remediation strategies.
• Nonionic surfactants can enhance contaminant mobility in soil.

Purpose of the Study:

• To define and evaluate a solution property parameter (phi) for assessing organic compound distribution.
• To investigate the influence of soil properties and surfactant characteristics on contaminant release.
• To correlate phi values with the release ratios of organic compounds from soil to groundwater.

Main Methods:

• Studied BTEX and chlorinated pesticides with varying water solubilities (Sw).
• Utilized low organic matter clay (Ca-montmorillonite) and high organic matter soil (Shamou Mountain soil).
• Employed four nonionic surfactants (alkyl chain and aromatic group) below and above critical micelle concentration (CMC).

Main Results:

• The distribution coefficient (Koc or Ksf) depends on Sw, soil organic matter (SOM), and compound structure.
• Higher phi values correlate with increased organic compound release from soil to groundwater.
• For high Sw compounds (BTEX), phi values approximated 1.
• For low Sw compounds, phi values exceeded 1 and increased with higher affinity to surfactants.

Conclusions:

• The parameter phi effectively predicts organic compound release ratios.
• Soil organic matter composition and organic compound chemical structure significantly affect distribution.
• Surfactant properties, including CMC, play a key role in enhancing contaminant mobility.