Open AccessA review of indirect N2O emission factors from artificial agricultural waters
Author(s) -
Jackie R. Webb,
Tim J. Clough,
Wendy C. Quayle
Publication year - 2021
Publication title -
environmental research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.37
H-Index - 124
ISSN - 1748-9326
DOI - 10.1088/1748-9326/abed00
Subject(s) - environmental science , irrigation , nitrous oxide , agriculture , surface water , surface runoff , nitrate , hydrology (agriculture) , water quality , nitrogen , environmental engineering , environmental chemistry , agronomy , ecology , chemistry , biology , geotechnical engineering , organic chemistry , engineering
Nitrous oxide (N 2 O) produced from dissolved nitrogen (N) compounds in agricultural runoff water must be accounted for when reporting N 2 O budgets from agricultural industries. Constructed (‘artificial’) water bodies within the farm landscape are the first aquatic systems that receive field N losses, yet emission accounting for these systems remains under-represented in Intergovernmental Panel on Climate Change (IPCC) emission factor (EF) guidelines and global N 2 O budgets. Here, we examine the role of artificial waters as indirect sources of agricultural N 2 O emissions, identify research gaps, and explore the challenge of predicting these emissions using default EFs. Data from 52 studies reporting dissolved N 2 O, nitrate (NO 3 ), and EFs were synthesised from the literature and classified into four water groups; subsurface drains, surface drains, irrigation canals, and farm dams. N 2 O concentration varied significantly between artificial waters while NO 3 did not, suggesting functional differences in the way artificial waters respond to anthropogenic N loading. EFs for the N 2 O–N:NO 3 –N concentration ratio were highly skewed and varied up to three orders of magnitude, ranged 0.005%–2.6%, 0.02%–4.4%, 0.03%–1.33%, and 0.04%–0.46% in subsurface drains, surface drains, irrigation canals, and farm dams, respectively. N 2 O displayed a non-linear relationship with NO 3 , where EF decreased exponentially with increasing NO 3 , demonstrating the inappropriateness of the stationary EF model. We show that the current IPCC EF model tends to overestimate N 2 O production in response to NO 3 loading across most artificial waters, particularly for farm dams. Given their widespread existence, there is a need to: (a) constrain their global abundance and distribution; (b) include artificial waters in the global N 2 O budget, and (c) expand the study of N processing in artificial waters across a geographically diverse area to develop our biogeochemical understanding to the level that has been achieved for rivers and lakes.