DOI: 10.5194/hess-24-3583-2020
论文题名: Irrigation return flow causing a nitrate hotspot and denitrification imprints in groundwater at Tinwald; New Zealand
作者: Kilgour Stewart M. ; Lauren Aitchison-Earl P.
刊名: Hydrology and Earth System Sciences
ISSN: 1027-5606
出版年: 2020
卷: 24, 期: 7 起始页码: 3583
结束页码: 3601
语种: 英语
Scopus关键词: Denitrification
; Dissolved oxygen
; Groundwater
; Indicators (chemical)
; Irrigation
; Isotopes
; Water management
; Chemical concentrations
; Dissolved oxygen concentrations
; Groundwater system
; Irrigation return flows
; Isotopic composition
; Management implications
; Nitrate concentration
; Nitrate transport
; Nitrates
; concentration (composition)
; denitrification
; dissolved oxygen
; groundwater
; isotopic composition
; nitrate
; water chemistry
; New Zealand
英文摘要: Nitrate concentrations in groundwater have been historically high (N 11:3 mg L1) in an area surrounding Tinwald, Ashburton, since at least the mid-1980s. The local community is interested in methods to remediate the high nitrate in groundwater. To do this, they need to know where the nitrate is coming from. Tinwald groundwater exhibits two features stemming from irrigation with local groundwater (i.e. irrigation return flow). The first feature is increased concentrations of nitrate (and other chemicals and stable isotopes) in a hotspot around Tinwald. The chemical concentrations of the groundwater are increased by recirculation of water already relatively high in chemicals. The irrigation return flow coefficient C (irrigation return flow divided by irrigation flow) is found to be consistent with the chemical enrichments. The stable isotopes of the groundwater show a similar pattern of enrichment by irrigation return flow of up to 40% and are also enriched by evaporation (causing a loss of about 5% of the original water mass). Management implications are that irrigation return flow needs to be taken into account in modelling of nitrate transport through soil– groundwater systems and in avoiding overuse of nitrate fertiliser leading to greater leaching of nitrate to the groundwater and unnecessary economic cost. The second feature is the presence of denitrification imprints (shown by enrichment of the 15N and 18ONO3 values of nitrate) in even relatively oxic groundwaters. The denitrification imprints can be clearly seen because (apart from denitrification) the nitrate has a blended isotopic composition due to irrigation return flow and N being retained in the soil–plant system as organic N. The nitrate concentration and isotopic compositions of nitrate are found to be correlated with the dissolved oxygen (DO) concentration. This denitrification imprint is attributed to localised denitrification in fine pores or small-scale physical heterogeneity where conditions are reducing. The implication is that denitrification could be occurring where it is not expected because groundwater DO concentrations are not low. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/162640
Appears in Collections: 气候变化与战略
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作者单位: Kilgour Stewart, M., Aquifer Dynamics, 20B Willoughby St., Lower Hutt, 5010, New Zealand, Gns Science, P.O. Box 30 368, Lower Hutt, 5040, New Zealand; Lauren Aitchison-Earl, P., Environment Canterbury, P.O. Box 345, Christchurch, 8011, New Zealand
Recommended Citation:
Kilgour Stewart M.,Lauren Aitchison-Earl P.. Irrigation return flow causing a nitrate hotspot and denitrification imprints in groundwater at Tinwald; New Zealand[J]. Hydrology and Earth System Sciences,2020-01-01,24(7)