Microbial mechanisms responsible for the variation of soil Cd availability under different pe+pH environments.

Area of Science:

• Environmental Microbiology
• Soil Science
• Biogeochemistry

Background:

• Soil cadmium (Cd) contamination poses environmental risks.
• Water management practices can influence soil properties and contaminant mobility.
• Understanding microbial roles in Cd availability under varying redox and pH is crucial.

Purpose of the Study:

• To investigate microbial mechanisms linking water management to soil Cd availability.
• To explore how changing redox potential (pe) and pH affect Cd dynamics.
• To identify microbial biomarkers sensitive to different water regimes.

Main Methods:

• Application of four water regimes (aerobic, aerobic + dissolved oxygen, continuous flooding, continuous flooding + N2) to Cd-contaminated soil.
• Analysis of soil pe + pH, Cd, sulfur (S), and iron (Fe) availability.
• Phylogenetic molecular ecological network (pMEN) and functional gene profile analysis to assess bacterial community structure, interactions, and functions.
• Structural equation modeling to determine the influence of soil pe + pH on microbial communities and Cd availability.

Main Results:

• Anoxic water treatments effectively decreased soil pe + pH, leading to reduced Cd availability and increased S and Fe availability compared to aerobic treatments.
• Anaerobic microbial families (e.g., Anaerolineaceae, Geobacteraceae) were enriched under anoxic conditions, while aerobic-sensitive families (e.g., Gemmatimonadaceae, Sphingomonadaceae) responded to aerobic treatments.
• Bacterial community structure and network interactions were significantly altered by water regimes, enhancing adaptation to varying pe + pH environments.
• Predicted functional categories related to metabolism, motility, and transport were affected by irrigation, facilitating bacterial acclimation.

Conclusions:

• Water management strategies, particularly anoxic conditions, can effectively reduce soil Cd availability by altering soil pe + pH.
• Microbial communities play a key role in mediating Cd availability, with distinct groups responding to aerobic and anaerobic environments.
• Soil pe + pH is a significant driver of microbial community shifts, enzyme activities, and ultimately, soil Cd availability and redox-sensitive element reduction.