Laboratory versus field soil aging: Impact on DDE bioavailability and sorption.

Area of Science:

• Environmental Chemistry
• Soil Science
• Contaminant Fate and Transport

Background:

• Persistent organic pollutants like p,p '-DDE can undergo aging in soil, altering their bioavailability and environmental risk.
• Understanding the kinetics of contaminant aging is crucial for accurate environmental risk assessment.

Purpose of the Study:

• To investigate the influence of aging on p,p '-DDE in laboratory-contaminated soil over 730 days.
• To compare laboratory aging effects with field-aged p,p '-DDE to determine appropriate aging durations for mimicking field conditions.

Main Methods:

• Sequential Supercritical Fluid Extraction (SFE) to determine p,p '-DDE distribution among fast, moderate, and slow desorbing soil sites.
• Solid-Phase Microextraction (SPME) to measure the freely dissolved concentration (C_free).
• XAD resin extraction to quantify the potentially bioaccessible fraction (F_XAD).

Main Results:

• p,p '-DDE's C_free and F_XAD decreased by up to 40% within the first 35 days of aging, then stabilized.
• The proportion of fast-desorbing sites decreased exponentially with aging, while moderate and slow sites increased, stabilizing after 90 days.
• Laboratory aging for 35-90 days approximated the C_free, F_XAD, and SFE profiles of field-aged p,p '-DDE (over 40 years).

Conclusions:

• Soil aging significantly reduces p,p '-DDE bioavailability in the short term.
• Laboratory aging studies require several months to adequately represent long-term field aging processes.
• SFE and XAD methods are effective in characterizing contaminant bioavailability and desorption kinetics influenced by aging.