Accurate and precise quantification of atmospheric nitrate in streams  draining land of various uses by using triple oxygen isotopes as tracers

Tsunogai, Urumu; Miyauchi, Takanori; Ohyama, T.; Komatsu, Daisuke; Nakagawa, Fumiko; Obata, Yusuke; Sato, Keiichi; Ohizumi, Tsuyoshi

doi:10.5194/bg-13-3441-2016

Cited by 33 publications

(74 citation statements)

References 72 publications

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“…The values and trends are consistent with prior empirical studies of 17 O wet at Rishiri between 2006 and 2007 and elsewhere in Japan (Tsunogai et al, 2016). These results also coincide well with model predictions (Alexander et al, 2009), which suggest that they indicate seasonal variation in the relative importance of oxidation of NO 2 by O 3 vs. OH in background, free tropospheric air.…”

Section: Discussionsupporting

confidence: 89%

“…Prior to isotopic analysis we reanalyzed nitrate and nitrate concentrations in the samples and found that differences between these and the original concentration measurements were < 10 %. For isotopic analysis, nitrite and nitrate in each filtrate sample was converted to N 2 O using chemical conversion (McIlvin and Altabet, 2005) with slight modification (Tsunogai et al, , 2016. Isotopic analysis of nitrite alone was also performed on samples with nitrite concentrations > 5.0 % of the total nitrite plus nitrate concentrations (McIlvin and Altabet, 2005).…”

Section: Discussionmentioning

confidence: 99%

“…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%

“…Nitrogen isotopes (δ 15 N) of nitrate can potentially reflect those of NO x , but mass-dependent isotopic fractionations during the oxidation of NO x to nitrate can also alter the original δ 15 N value of NO x , thus complicating efforts to use δ 15 N values of nitrate for source partitioning (e.g., Michalski, 2015, 2016; (Alexander et al, 2009;Morin et al, 2008;Michalski et al, 2003;Tsunogai et al, , 2016 since direct emissions of nitrate during combustion are relatively small (Fraser et al, 1998). (Michalski et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…The remaining fraction results from the extent to which O 3 vs. OH molecules oxidize NO 2 (Geng et al, 2017). 17 O values of atmospheric nitrate deposition are often highest in winter and lowest in summer (Michalski et al, 2003;Savarino et al, 2007;Tsunogai et al, , 2016, because longer periods of darkness and lower temperatures favor the oxidation of NO x by O 3 , as well as N 2 O 5 hydrolysis reactions, whereas oxidation of NO 2 by OH is more important when daylight is longer and temperatures higher (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

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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: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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Quantifying nitrate dynamics in a mesotrophic lake using triple oxygen isotopes as tracers

Tsunogai

Miyauchi

Ohyama

et al. 2018

Limnology & Oceanography

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Vertical distributions of both concentrations and stable isotopic compositions of nitrate, including the 17 O-excesses (D 17 O), were determined four times during 1 yr within the mesotrophic water column of Lake Biwa in Japan. By using both the deposition rate of atmospheric nitrate onto the entire surface of the lake and the influx/efflux of both atmospheric and remineralized nitrate via streams reported in the literature, we quantified the annual dynamics of nitrate (gross production rate of nitrate through nitrification and gross metabolic rate of nitrate through assimilation and denitrification), together with their seasonal variations, based on the D 17 O method. The results revealed that 642 6 113 Mmol (Mmol 5 10 6 mol) of the remineralized nitrate was supplied into the water column through nitrification in the lake on an annual basis, while 810 6 120 Mmol of nitrate was metabolized in the lake through assimilation and denitrification. In addition, it turns out that nitrification was active, not only in the hypolimnion, but also in the epilimnion and upper thermocline in this lake. Furthermore, the total metabolic rates of nitrate varied seasonally, with the highest rates in summer and the lowest in winter. Because the difference between the annual metabolic rate of nitrate estimated based on the D 17 O method and the annual assimilation rate of nitrate estimated based on the traditional 15 N incubation method was only 20%, we concluded that the D 17 O method reliably estimates the dynamics of nitrate in mesotrophic lakes. Nitrate (NO 23 ) is a key nutrient in aquatic environments that often limits primary production. Nitrate dynamics in an aquatic environment, i.e., gross production rate of nitrate through nitrification (F nit ), gross metabolic rate of nitrate through assimilation (F assim ), and gross metabolic rate of nitrate through denitrification (F denit ), are important parameters to be quantified when evaluating both the present and future state of the aquatic environment. In most studies that have been conducted to date, nitrate dynamics has been estimated via incubation experiments using 15 N tracer techniques. To quantify F assim , for instance, 15 N-labeled NO 2 3 is added into bottles that simulate in situ conditions of the aquatic environment studied, which leads to the production of particulate organic-15 N (PO 15 N) through assimilation over a known incubation period of several hours to several days (Dugdale and Goering 1967;Knap et al. 1996). The PO 15 N is then gathered and quantified using mass spectrometry.The experimental procedures using 15 N tracer, however, are generally costly and complicated. Besides, while the obtained nitrate dynamics is an instantaneous assimilation rate at the point of observation, such a value may be temporally variable in response to various factors such as changes in temperature, light intensity, nutrients, and community structure. As a result, tedious and time-consuming time series observations are needed to estimate long-term nitrate dynamics (s...

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Dual stable isotope characterization of excess methane in oxic waters of a mesotrophic lake

Tsunogai

Miyoshi

Matsushita

et al. 2020

Limnology & Oceanography

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To determine the source of excess methane in oxic, surface‐water columns often found in freshwater environments, we measured the in situ concentration and stable isotopic compositions (δ13C and δ2H) of methane in Lake Biwa, a mesotrophic lake in Japan. The values from the littoral zone and lake‐floor sediments were determined, besides those in the water column of the pelagic zone. Furthermore, we conducted incubation experiments to measure microbial oxidation rates and alterations in the isotopic signatures of methane. We found significant vertical and seasonal variations in both in situ concentrations and stable isotopic compositions of methane measured in the pelagic zone. We concluded that active microbial oxidation was primarily responsible for the variation in δ13C and δ2H values of methane in the pelagic water column. As a result, we defined a new indicator Δ(2,13) to characterize the sources of dissolved methane, in which variations in both δ13C and δ2H during methane oxidation had been corrected. The excess methane in oxic, surface‐water columns exhibited Δ(2,13) values similar to those in the littoral zone. We concluded that excess methane at the surface of the pelagic zone originated from the littoral zone via lateral transport. Anoxic near sediments and inflowing rivers were responsible for methane enrichment in water of the littoral zone and in the surface water columns of the pelagic zone.

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Accurate and precise quantification of atmospheric nitrate in streams draining land of various uses by using triple oxygen isotopes as tracers

Cited by 33 publications

References 72 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

Quantifying nitrate dynamics in a mesotrophic lake using triple oxygen isotopes as tracers

Dual stable isotope characterization of excess methane in oxic waters of a mesotrophic lake

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