A laboratory method for testing the volatility from aqueous solution: first results and comparison with theory

Area of Science:

• Environmental Science
• Chemical Engineering
• Physical Chemistry

Background:

• Chemical mobility in the environment is crucial for understanding contaminant fate.
• Volatilization from aqueous solutions is a key transport process for chemicals with low water solubility and high vapor pressure.

Purpose of the Study:

• To develop and validate a laboratory apparatus for simulating chemical volatilization from stirred water bodies.
• To investigate the influence of environmental factors like wind velocity, air humidity, and temperature on volatilization rates.
• To compare experimental substance fluxes with theoretical predictions.

Main Methods:

• A laboratory apparatus was designed to simulate a stirred water body with controlled wind velocities and water temperatures.
• Experiments were conducted using naphthalene, pentachlorophenol, trichloroethene, and di(2-ethylhexyl)phthalate.
• Substance concentrations in the water were monitored over time to determine volatilization rates and half-residence times.

Main Results:

• Chemical concentrations in the water decreased exponentially, aligning with theoretical models.
• Half-residence times were independent of wind velocity (below 1 m/s) and air humidity.
• Temperature was identified as a significant factor influencing volatilization rates.
• Measured substance fluxes closely matched theoretical values.
• For pentachlorophenol, pH significantly affected its volatility due to partial dissociation.

Conclusions:

• The developed laboratory apparatus effectively simulates environmental volatilization processes.
• Temperature is a critical parameter controlling the rate of chemical volatilization from water.
• The study provides valuable data for predicting the environmental fate and transport of chemicals.