New insights into how chalcopyrite mitigates nitrous oxide emissions from denitrification

Area of Science:

• Environmental Science
• Water Quality Management
• Biogeochemistry

Background:

• Green infrastructure, specifically bioretention systems, effectively removes nitrogen from stormwater.
• Incomplete denitrification in bioretention systems leads to nitrous oxide (N2O) emissions due to low carbon-to-nitrogen ratios.

Purpose of the Study:

• To evaluate the impact of chalcopyrite and pyrite amendments on denitrification and N2O reduction in bioretention systems.
• To elucidate the mechanisms by which these minerals influence nitrogen cycling and N2O mitigation.

Main Methods:

• Experimental setup with three groups: chalcopyrite, pyrite, and control.
• Measurement of N2O flux, nitrate removal efficiency, and microbial gene abundance (nosZ).
• Assessment of electron transport system activity to understand enzyme function.

Main Results:

• Chalcopyrite amendment increased nitrate removal efficiency by 19.0% (71.3% total).
• N2O flux was significantly reduced in chalcopyrite groups.
• Chalcopyrite led to an 11-fold increase in nosZ gene abundance and enhanced electron transport activity.

Conclusions:

• Chalcopyrite promotes autotrophic denitrification via sulfur and iron oxidation, enhancing nitrogen removal.
• Released copper ions from chalcopyrite further aid in N2O reduction.
• Chalcopyrite is a promising amendment for improving nitrogen removal and mitigating N2O emissions in nature-based solutions.