Vanadium bioavailability and toxicity to soil microorganisms and plants

Area of Science:

• Environmental Chemistry
• Soil Science
• Ecotoxicology

Background:

• Vanadium (V) is a redox-sensitive metal, often present as vanadate in aerobic solutions.
• Limited data exists on vanadium's toxicity to soil biota.
• Understanding vanadium's impact on soil ecosystems is crucial for environmental risk assessment.

Purpose of the Study:

• To determine the toxicity of added vanadate to soil organisms (microbial and plant assays).
• To investigate the relationship between vanadate toxicity and vanadium sorption in different soil types.
• To establish robust measures for critical vanadium concentrations in soils.

Main Methods:

• Five soils with diverse properties were spiked with seven different doses of dissolved vanadate (3.2–3200 mg V kg⁻¹).
• Toxicity was assessed using two microbial and three plant assays to determine median effective concentrations (EC50).
• Vanadium sorption strength and soil solution vanadium concentrations were analyzed.

Main Results:

• EC50 values for microbial assays ranged from 28 to 690 mg added V kg⁻¹.
• EC50 values for plant assays ranged from 18 to 510 mg added V kg⁻¹.
• Vanadium toxicity to plants decreased with increased soil vanadium sorption; soil solution vanadium was a more consistent toxicity indicator across soils.

Conclusions:

• Soil vanadium sorption significantly reduces the toxicity of added vanadate to soil organisms.
• Soil solution vanadium concentration provides a more reliable metric for assessing vanadium toxicity thresholds compared to total soil vanadium.
• These findings aid in understanding vanadium's environmental fate and ecological risk in soils.