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Infiltration Mechanism Controls Nitrification and Denitrification Processes under Dairy Waste Lagoon
Author(s) -
Baram S.,
Ar S.,
Ronen Z.,
Kurtzman D.,
Dahan O.
Publication year - 2012
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2012.0015
Subject(s) - vadose zone , infiltration (hvac) , denitrification , nitrification , sediment , environmental chemistry , wastewater , environmental science , nitrate , hydrology (agriculture) , pore water pressure , soil water , nitrogen , environmental engineering , chemistry , soil science , geology , geotechnical engineering , geomorphology , physics , organic chemistry , thermodynamics
Earthen waste lagoons are commonly used to store liquid wastes from concentrated animal feeding operations. The fate of ammonium (NH 4 + ) and nitrate (NO 3 ‐ ) was studied in the vadose zone below earthen‐clay dairy farm waste lagoons using three independent vadose zone monitoring systems. The vadose zone was monitored from 0.5 to 30 m below land surface through direct sampling of the sediment porewater and continuous measurement of the sediment profile's water content variations. Four years of monitoring revealed that wastewater infiltration from the lagoon is controlled by two mechanisms: slow (mm d −1 ), constant infiltration from the lagoon bed; and rapid (m h −1 ) infiltration of wastewater and rainwater via preferential flow in desiccation cracks formed in the unsaturated clay sediment surrounding the lagoon banks. The preferential flow mechanism is active mainly during wastewater‐level fluctuations and intensive rain events. The vadose zone below the waste sources remained unsaturated throughout the monitoring period, and all infiltrating NH 4 + was oxidized in the upper 0.5 m. The NH 4 + oxidation (nitrification) was coupled with NO 3 ‐ reduction (denitrification) and depended on the sediment water content, which was controlled by the infiltration mechanism. Coupled nitrification–denitrification (CND) resulted in 90 to 100% reduction in the total nitrogen mass in the vadose zone, with higher removal under high water content (∼0.55 m 3 m ‐3 ). Mass balance of nitrogen and isotopic composition of NO 3 ‐ indicated that CND, rather than cation exchange capacity, is the key factor regulating nitrogen's fate in the vadose zone underlying earthen waste lagoons.