Laboratory versus field soil aging: Impacts on cadmium distribution, release, and bioavailability

Area of Science:

• Environmental Science
• Soil Science
• Geochemistry

Background:

• Most soil metal aging studies rely on controlled laboratory experiments.
• Limited research exists on how aging influences metal distribution and bioavailability under field conditions.
• Understanding metal aging in situ is crucial for accurate environmental risk assessment.

Purpose of the Study:

• To compare cadmium (Cd) aging in soil under controlled laboratory versus field conditions.
• To monitor time-dependent changes in soil Cd speciation, release kinetics, and plant bioavailability over 438 days.

Main Methods:

• Conducted parallel 438-day aging experiments for cadmium in soil under laboratory and field conditions.
• Monitored changes in soil Cd speciation (fractionation).
• Assessed Cd release kinetics using the Elovich equation and plant bioavailability through vegetable uptake.

Main Results:

• Aging decreased weakly bound Cd fractions, increasing stable fractions in both settings.
• Field-aged soil showed higher available Cd (0.74 mg kg⁻¹) than lab-aged soil (0.65 mg kg⁻¹).
• Field-aged soil exhibited greater Cd release (2.74 mg kg⁻¹) and higher vegetable Cd accumulation (1.49 mg kg⁻¹ FW) than lab-aged soil.

Conclusions:

• Field aging significantly increases soil cadmium bioavailability and plant uptake compared to laboratory aging.
• The Elovich equation effectively models soil available Cd aging, with a slower transformation rate in field conditions.
• Laboratory data may overestimate or underestimate soil metal bioavailability and distribution, impacting soil quality criteria development.