File Download

There are no files associated with this item.

  Links for fulltext
     (May Require Subscription)

Article: Nitrogen sources and cycling revealed by dual isotopes of nitrate in a complex urbanized environment

TitleNitrogen sources and cycling revealed by dual isotopes of nitrate in a complex urbanized environment
Authors
Issue Date2018
PublisherElsevier. The Journal's web site is located at http://www.elsevier.com/locate/watres
Citation
Water research, 2018, v. 142, p. 459-470 How to Cite?
AbstractElevated nutrient inputs have led to increased eutrophication in coastal marine ecosystems worldwide. An understanding of the relative contribution of different nutrient sources is imperative for effective water quality management. Stable isotope values of nitrate (δ15NNO3-, δ18ONO3-) can complement conventional water quality monitoring programs to help differentiate natural sources of NO3- from anthropogenic inputs and estimate the processes involved in N cycling within an ecosystem. We measured nutrient concentrations, δ15NNO3-, and δ18ONO3- in 76 locations along a salinity gradient from the lower end of the Pearl River Estuary, one of China's largest rivers discharging into the South China Sea, towards the open ocean. NO3- concentrations decreased with increasing salinity, indicative of conservative mixing of eutrophic freshwater and oligotrophic seawater. However, our data did not follow conservative mixing patterns. At salinities <20 psu, samples exhibited decreasing NO3- concentrations with almost unchanged NO3- isotope values, indicating simple dilution. At salinities >20 psu, NO3- concentrations decreased, while dual NO3- isotopes increased, suggesting mixing and/or other transformation processes. Our analysis yielded mean estimates for isotope enrichment factors (15ε=-2.02‰ and 18ε=-3.37‰), Δ(15,18) = -5.5‰ and δ15N NO3- - δ15NNO2- =12.3‰. After consideration of potential alternative sources (sewage, atmospheric deposition and groundwater) we concluded that there are three plausible interpretations for deviations from conservative mixing behaviour (1) NO3- uptake by assimilation (2) in situ NO3- production (from fixation-derived nitrogen and nitrification of sewage-derived effluents) and (3) input of groundwater nitrate carrying a denitrification signal. Through this study, we propose a simple workflow that incorporates a synthesis of numerous isotope-based studies to constrain sources and behaviour of NO3- in urbanized marine environments.
Persistent Identifierhttp://hdl.handle.net/10722/258574
ISI Accession Number ID

 

DC FieldValueLanguage
dc.contributor.authorArchana, A-
dc.contributor.authorThibodeau, B-
dc.contributor.authorGeeraert, NAA-
dc.contributor.authorXu, MN-
dc.contributor.authorKao, SJ-
dc.contributor.authorBaker, DM-
dc.date.accessioned2018-08-22T01:40:42Z-
dc.date.available2018-08-22T01:40:42Z-
dc.date.issued2018-
dc.identifier.citationWater research, 2018, v. 142, p. 459-470-
dc.identifier.urihttp://hdl.handle.net/10722/258574-
dc.description.abstractElevated nutrient inputs have led to increased eutrophication in coastal marine ecosystems worldwide. An understanding of the relative contribution of different nutrient sources is imperative for effective water quality management. Stable isotope values of nitrate (δ15NNO3-, δ18ONO3-) can complement conventional water quality monitoring programs to help differentiate natural sources of NO3- from anthropogenic inputs and estimate the processes involved in N cycling within an ecosystem. We measured nutrient concentrations, δ15NNO3-, and δ18ONO3- in 76 locations along a salinity gradient from the lower end of the Pearl River Estuary, one of China's largest rivers discharging into the South China Sea, towards the open ocean. NO3- concentrations decreased with increasing salinity, indicative of conservative mixing of eutrophic freshwater and oligotrophic seawater. However, our data did not follow conservative mixing patterns. At salinities <20 psu, samples exhibited decreasing NO3- concentrations with almost unchanged NO3- isotope values, indicating simple dilution. At salinities >20 psu, NO3- concentrations decreased, while dual NO3- isotopes increased, suggesting mixing and/or other transformation processes. Our analysis yielded mean estimates for isotope enrichment factors (15ε=-2.02‰ and 18ε=-3.37‰), Δ(15,18) = -5.5‰ and δ15N NO3- - δ15NNO2- =12.3‰. After consideration of potential alternative sources (sewage, atmospheric deposition and groundwater) we concluded that there are three plausible interpretations for deviations from conservative mixing behaviour (1) NO3- uptake by assimilation (2) in situ NO3- production (from fixation-derived nitrogen and nitrification of sewage-derived effluents) and (3) input of groundwater nitrate carrying a denitrification signal. Through this study, we propose a simple workflow that incorporates a synthesis of numerous isotope-based studies to constrain sources and behaviour of NO3- in urbanized marine environments.-
dc.languageeng-
dc.publisherElsevier. The Journal's web site is located at http://www.elsevier.com/locate/watres-
dc.relation.ispartofWater research-
dc.titleNitrogen sources and cycling revealed by dual isotopes of nitrate in a complex urbanized environment-
dc.typeArticle-
dc.identifier.emailThibodeau, B: bthib@hku.hk-
dc.identifier.emailGeeraert, NAA: geeraert@hku.hk-
dc.identifier.emailBaker, DM: dmbaker@hku.hk-
dc.identifier.authorityThibodeau, B=rp02033-
dc.identifier.authorityBaker, DM=rp01712-
dc.identifier.doi10.1016/j.watres.2018.06.004-
dc.identifier.hkuros287436-
dc.identifier.volume142-
dc.identifier.spage459-
dc.identifier.epage470-
dc.identifier.isiWOS:000440125800045-

Export via OAI-PMH Interface in XML Formats


OR


Export to Other Non-XML Formats