A Model for Nitrogen Transformations in Effluent Irrigated Soil Aggregates

Kremen, Arie; Shavit, Uri; Bear, Jacob; Shaviv, A.

doi:10.13031/2013.11232

Cited by 1 publication

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“…The soil aggregate model is rather parameter intensive, requiring diffusion rates, reaction rate coefficients, and soil properties. Wherever possible, preference was given to postprocessing data obtained experimentally (38,39,50,51) (e.g., nitrification kinetics and soil properties). If relevant data were not easily obtainable, published values have been used.…”

Section: Simulations and Resultsmentioning

confidence: 99%

Model Demonstrating the Potential for Coupled Nitrification Denitrification in Soil Aggregates

Kremen

Bear

Shavit

et al. 2005

Environ. Sci. Technol.

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A model of reactive, multi-species diffusion has been developed to describe N transformations in spherical soil aggregates, emphasizing the effects of irrigation with reclaimed wastewater. Oxygen demand for respiratory activity has been shown to promote the establishment of anaerobic conditions. Aggregate size and soil respiration rate were identified as the most significant parameters governing the existence and extent of the anaerobic volume in aggregates. The inclusion of kinetic models describing mineralization, nitrification, and denitrification facilitated the investigation of coupled nitrification/denitrification (CND), subject to O2 availability. N-transformations are shown to be affected by effluent-borne NH4+-N content, in addition to elevated BOD and pH levels. Their incremental contribution to O2 availability has been found to be secondary to respiratory activity. At the aggregate level, significant differences between apparent and gross rates of N-transformations were predicted (e.g., NH4+ oxidation and N2 formation), resulting from diffusive constraints due to aggregate size. With increasing anaerobic volume, the effective nitrification rate determined at the aggregates level decreases until its contribution to nitrification is negligible. It was found that the nitrification process was predominantly limited to aggregates <0.25 cm. Assuming that nitrification is the main source for NO3- formation, denitrification efficiency is predicted to peak in medium-sized aggregates, where aerobic and anaerobic conditions coexist, supporting CND. In effluent-irrigated soils, the predicted NO2- formation rate in small aggregates is enhanced when compared to freshwater-irrigated soils. The difference vanishes with increasing aggregate size as anaerobic NO2- consumption exceeds aerobic NO2- formation due to the coupling of nitrification and denitrification.

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Section: Simulations and Resultsmentioning

confidence: 99%