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Transport and Transformation of Urea and Its Derivatives through a Mineral Subsoil
Author(s) -
Swensen Berit,
Singh Bal Ram
Publication year - 1997
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/jeq1997.00472425002600060010x
Subject(s) - urea , chemistry , ammonium , nitrification , lysimeter , hydrolysis , environmental chemistry , nitrogen , nitrate , ammonia , soil water , geology , soil science , organic chemistry
The transport and transformation potential of N compounds derived from urea, applied as a deicing agent during the winter period, have been investigated in a coarse, heterogeneous glacial‐contact deposit in southeast Norway. The hydrolysis of urea to ammonium‐N (NH + 4 ‐N) and subsequent oxidation to nitrate‐N (NO − 3 ‐N) was monitored by extraction of soil water from five depths (from 70 to 220 cm) in a lysimeter trench. Urea transport through a soil profile is normally negligible, although urea is a hydrophilic, uncharged molecule. In this study, urea was rapidly transported to at least 220 cm. The measured urea‐N concentrations varied from 2 to 50 mg L −1 throughout the profile. This transport was explained by minimal hydrolytic activity because of soil temperatures close to 0°C, and by different preferential flow mechanisms being important during the snowmelt period. Urea hydrolysis occurred at all depths. The NH + 4 ‐N formed in this in situ hydrolysis was oxidized to NO − 3 ‐N. The nitrification started immediately and was most rapid at the 70‐ and 105‐cm depth, but was detectable at all depths down to 220 cm 120 d after solute application. Nitrification also occurred during the winter following the urea application. One year after the urea application, about 40% of the applied urea‐N was recovered as NO − 3 ‐N in the unsaturated zone (0–450 cm), and it is estimated that at least 50% of the applied N will reach the groundwater as NO − 3 ‐N.