Episodic, seasonal, and annual export of atmospheric and microbial nitrate from a temperate forest

Sabo, Robert D.; Nelson, David M.; Eshleman, Keith N.

doi:10.1002/2015gl066758

Cited by 25 publications

(38 citation statements)

References 57 publications

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“…The 17 O values of nitrate are increasingly used in watershed studies to determine the relative abundance of unprocessed atmospheric nitrate in environmental waters, such as rivers and lakes (Sabo et al, 2016;Riha et al, 2015;Tsunogai et al, , 2016Michalski et al, 2004 17 O dry at some sites, such as semi-closed and/or highly polluted urban areas, where the majority of deposition comes from local sources.…”

Section: Discussionmentioning

confidence: 99%

Triple oxygen isotopes indicate urbanization affects sources of nitrate in wet and dry atmospheric deposition

et al. 2018

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Abstract. Atmospheric nitrate deposition resulting from anthropogenic activities negatively affects human and environmental health. Identifying deposited nitrate that is produced locally vs. that originating from long-distance transport would help inform efforts to mitigate such impacts. However, distinguishing the relative transport distances of atmospheric nitrate in urban areas remains a major challenge since it may be produced locally and/or be transported from upwind regions. To address this uncertainty we assessed spatiotemporal variation in monthly weighted-average 17 O and δ 15 N values of wet and dry nitrate deposition during one year at urban and rural sites along the western coast of the northern Japanese island of Hokkaido, downwind of the East Asian continent. 17 O values of nitrate in wet deposition at the urban site mirrored those of wet and dry deposition at the rural site, ranging between ∼ +23 and +31 ‰ with higher values during winter and lower values in summer, which suggests the greater relative importance of oxidation of NO 2 by O 3 during winter and OH during summer. In contrast, 17 O values of nitrate in dry deposition at the urban site were lower (+19 -+25 ‰) and displayed less distinct seasonal variation. Furthermore, the difference between δ 15 N values of nitrate in wet and dry nitrate deposition was, on average, 3 ‰ greater at the urban than rural site, and 17 O and δ 15 N values were correlated for both forms of deposition at both sites with the exception of dry deposition at the urban site. These results suggest that, relative to nitrate in wet and dry deposition in rural environments and wet deposition in urban environments, nitrate in dry deposition in urban environments forms from relatively greater oxidation of NO by peroxy radicals and/or oxidation of NO 2 by OH. Given greater concentrations of peroxy radicals and OH in cities, these results imply that dry nitrate deposition results from local NO x emissions more so than wet deposition, which is transported longer distances. These results illustrate the value of stable isotope data for distinguishing the transport distances and reaction pathways of atmospheric nitrate pollution.

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Section: Discussionmentioning

confidence: 99%

Triple oxygen isotopes indicate urbanization affects sources of nitrate in wet and dry atmospheric deposition

et al. 2018

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“…In 5 addition to these traditional isotopes, 17 O-excess (Δ 17 O; the definition will be presented in section 1.2) of nitrate has been used as an additional, more robust tracer for unprocessed NO 3 − atm (nitrate that had been supplied via atmospheric deposition and have survived the biological processing of nitrate, such as assimilation and denitrification, within surface ecosystems) in stream water in recent years (Bourgeois et al, 2018;Michalski et al, 2004;Riha et al, 2014;Sabo et al, 2016;Tsunogai 10 et al, 2010;Tsunogai et al, 2014;Tsunogai et al, 2016). By determining both concentration and the 17 O-excess of stream nitrate, we can quantify unprocessed NO 3 − atm in stream water accurately and precisely.…”

Section: Stream Nitrate Being Exported From Forested Watersheds 10mentioning

confidence: 99%

“…6(c)) in IJ2. (Bourgeois et al, 2018;Nakagawa et al, 2013;Riha et al, 2014;Sabo et al, 2016;Tsunogai et al, 2014;Tsunogai et al, 2016).…”

Section: Ij1 and Ij2 Sitesmentioning

confidence: 99%

Export flux of unprocessed atmospheric nitrate from temperate forested catchments: A possible new index for nitrogen saturation

Nakagawa¹,

Tsunogai²,

Obata³

et al. 2018

Preprint

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“…Other processes, such as mineralization, NO 3 − leaching and assimilation, are generally believed to have negligible 15 N fractionation (Mariotti et al ., ; Billy et al ., ). NO 3 − isotopes also carry information about source differentiation, in which atmosphere‐derived NO 3 − often exhibits greater δ 18 O‐NO 3 − compared to biologically processed NO 3 − (Pardo et al ., ; Kendall et al ., ; Sabo et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Multiyear dual nitrate isotope signatures suggest that N‐saturated subtropical forested catchments can act as robust N sinks

Zhu

Mulder

et al. 2016

Global Change Biology

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In forests of the humid subtropics of China, chronically elevated nitrogen (N) deposition, predominantly as ammonium (NH ), causes significant nitrate (NO ) leaching from well-drained acid forest soils on hill slopes (HS), whereas significant retention of NO occurs in near-stream environments (groundwater discharge zones, GDZ). To aid our understanding of N transformations on the catchment level, we studied spatial and temporal variabilities of concentration and natural abundance (δ N and δ O) of nitrate (NO ) in soil pore water along a hydrological continuum in the N-saturated Tieshanping (TSP) catchment, southwest China. Our data show that effective removal of atmogenic NH and production of NO in soils on HS were associated with a significant decrease in δ N-NO , suggesting efficient nitrification despite low soil pH. The concentration of NO declined sharply along the hydrological flow path in the GDZ. This decline was associated with a significant increase in both δ N and δ O of residual NO , providing evidence that the GDZ acts as an N sink due to denitrification. The observed apparent N enrichment factor (ε) of NO of about -5‰ in the GDZ is similar to values previously reported for efficient denitrification in riparian and groundwater systems. Episode studies in the summers of 2009, 2010 and 2013 revealed that the spatial pattern of δ N and δ O-NO in soil water was remarkably similar from year to year. The importance of denitrification as a major N sink was also seen at the catchment scale, as largest δ N-NO values in stream water were observed at lowest discharge, confirming the importance of the relatively small GDZ for N removal under base flow conditions. This study, explicitly recognizing hydrologically connected landscape elements, reveals an overlooked but robust N sink in N-saturated, subtropical forests with important implications for regional N budgets.

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Episodic, seasonal, and annual export of atmospheric and microbial nitrate from a temperate forest

Cited by 25 publications

References 57 publications

Triple oxygen isotopes indicate urbanization affects sources of nitrate in wet and dry atmospheric deposition

Triple oxygen isotopes indicate urbanization affects sources of nitrate in wet and dry atmospheric deposition

Export flux of unprocessed atmospheric nitrate from temperate forested catchments: A possible new index for nitrogen saturation

Multiyear dual nitrate isotope signatures suggest that N‐saturated subtropical forested catchments can act as robust N sinks

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