Soil urease functional stability to Hg pollution: An ecotoxicological perspective

Area of Science:

• Environmental Science
• Soil Science
• Biochemistry

Background:

• Mercury (Hg) is a persistent soil pollutant with significant ecotoxicological implications.
• Soil enzymes, like urease, are sensitive indicators of heavy metal contamination.
• Understanding enzyme resistance and resilience to Hg stress is crucial for accurate toxicity assessments.

Purpose of the Study:

• To investigate the functional stability of soil urease under varying mercury (Hg) concentrations and exposure durations.
• To compare the Hg resistance of urease in different soil types (fluvo-aquic vs. red soil).
• To evaluate the long-term effects of Hg aging on soil urease activity and ecotoxicity.

Main Methods:

• Exposure of soil samples to different concentrations of Hg for various time periods (acute and chronic).
• Measurement of soil urease activity over time.
• Comparison of urease response in fluvo-aquic soil (high organic matter) and red soil.
• Determination of the ecological dose (ED10) for Hg toxicity.

Main Results:

• Soil urease activity showed a biphasic response: initial enhancement followed by inhibition under acute Hg exposure.
• Fluvo-aquic soil urease exhibited greater resistance to acute Hg pollution than red soil urease.
• Over a 30-day aging period, soil urease activity recovered, and hormesis effects were observed under high Hg stress in red soil.
• The ecological dose (ED10) for Hg was lower under short-term exposure (0.09–0.59 mg kg⁻¹) compared to longer aging periods (0.28–2.71 mg kg⁻¹).

Conclusions:

• Aging reduces Hg ecotoxicity by decreasing Hg availability and increasing soil urease resilience.
• Soil urease activity and stability are significantly influenced by Hg exposure time and soil properties.
• Accurate heavy metal pollution risk assessment using soil enzymes requires consideration of exposure duration and enzyme functional stability.