Linking denitrification and infiltration rates during managed groundwater recharge

Area of Science:

• Environmental Science
• Soil Science
• Hydrology

Background:

• Managed groundwater recharge is crucial for water supply.
• Understanding biogeochemical processes in soils is vital for water quality.
• Denitrification is a key process for nitrate removal.

Purpose of the Study:

• To quantify the relationship between in situ denitrification rates and saturated infiltration in shallow, sandy soils.
• To identify optimal infiltration rates for nitrate load reduction during managed groundwater recharge.

Main Methods:

• Utilized thermal methods to measure point-specific flow rates.
• Employed chemical and isotopic analyses to assess denitrification.
• Analyzed pore water oxygen and nitrate profiles.

Main Results:

• Measured denitrification rates ranged from 3 to 300 μmol L(-1) d(-1).
• Denitrification was inhibited when infiltration rates exceeded 0.7 ± 0.2 m d(-1).
• High flow rates deepened the redoxocline, reducing the denitrification zone.

Conclusions:

• Denitrification rates positively correlate with infiltration rates below a specific threshold.
• An optimal infiltration rate exists for maximizing nitrate reduction in sandy soils.
• The study provides a quantitative link between hydrologic and biogeochemical processes in managed recharge systems.