Isotopic composition of water-soluble nitrate in bulk atmospheric deposition at Dongsha Island: sources and implications of external N supply to the northern South China Sea

CORC > 厦门大学 > 海洋环境－已发表论文

	Isotopic composition of water-soluble nitrate in bulk atmospheric deposition at Dongsha Island: sources and implications of external N supply to the northern South China Sea
	Yang, J. -Y. T. ; Hsu, S. -C. ; Dai, M. H. ; Hsiao, S. S. -Y. ; Kao, S. -J. ; Gao SJ(高树基)
刊名	http://dx.doi.org/10.5194/bg-11-1833-2014
	2014
关键词	WET DEPOSITION NITROGEN DEPOSITION ORGANIC NITROGEN SEASONAL-VARIATIONS STABLE-ISOTOPES PACIFIC-OCEAN N-2 FIXATION FRESH-WATER EAST CHINA AIR
英文摘要	National Science Council, Taiwan; National Natural Science Foundation of China [NSFC 2014CB953702, 41176059, 2009CB421206, 2009CB421200, 41130857]; Increased reactive nitrogen (N-r, NO3- + NH4+ + dissolved organic nitrogen) emission from the Asian continent poses profound threats to ecosystem safety from terrestrial throughout the ocean proper. To quantify atmospheric N-r input, diagnose its sources, and evaluate influence on marine nitrogen cycle of the South China Sea (SCS), an oligotrophic marginal sea adjacent to the emission hot spot China, we conducted measurements of concentrations of nitrate and ammonium as well as other major ions and dual isotopes of nitrate (delta N-15(NO3) and delta O-18(NO3)) in atmospheric deposition collected from Dongsha Island off southern China. The delta N-15(NO3) and delta O-18(NO3) for dry deposition averaged at -2.8 parts per thousand and +58.8 parts per thousand, ranging from -7.5 to +3.7% and from similar to+17 to + 88 parts per thousand, respectively. Wet deposition, although with limited samples, showed a similar flux-weighted mean in delta N-15(NO3) (-2.6 parts per thousand) yet a significantly higher mean in delta O-18(NO3) (+78.8 parts per thousand). The dual isotope ratios showed an anti-correlation and an inverse seasonality; the delta(NNO3)-N-15 values were higher in summer compared to those in winter, while the delta(ONO3)-O-18 values were higher in winter than those in summer. In winter, not only dual isotopic compositions of nitrate but also the ammonium and nitrate dry deposition fluxes were relatively uniform, demonstrating a persistent influence of fossil fuel combustion sourced from Asian continental outflows via the northeasterly monsoon winds. More variable isotopic values in summer likely suggest varying sources and dynamical formation processes of dry deposition nitrate. Biomass burning and lightning are suggested to be responsible for the observed higher delta N-15(NO3) values in summer. Atmospheric nitrate and ammonium deposition together was estimated to be similar to 50 mmol N m(-2) year(-1), with the dominance of nitrate in dry deposition but ammonium slightly higher in wet deposition. If not including this additional fertilization of atmospheric inorganic nitrogen deposition to enhance the carbon sequestration, CO2 release out of the SCS would be double than that of the present amount, 460 +/- 430 mmol C m(-2) year(-1). Our study demonstrates that atmospheric deposition may serve as an important external N-r supplier to the SCS; however it is difficult to separate the isotopic signal from N-2 fixation (-2-0 parts per thousand) due to their similarity in delta N-15(NO3). More studies related to isotopic composition of nitrogen speciation in atmospheric N-r deposition, their relative contributions and source identification, and the role of typhoons in the SCS are required.
语种	英语
出版者	COPERNICUS GESELLSCHAFT MBH
内容类型	期刊论文
源URL	[http://dspace.xmu.edu.cn/handle/2288/88188]
专题	海洋环境－已发表论文
推荐引用方式 GB/T 7714	Yang, J. -Y. T.,Hsu, S. -C.,Dai, M. H.,et al. Isotopic composition of water-soluble nitrate in bulk atmospheric deposition at Dongsha Island: sources and implications of external N supply to the northern South China Sea[J]. http://dx.doi.org/10.5194/bg-11-1833-2014,2014.
APA	Yang, J. -Y. T.,Hsu, S. -C.,Dai, M. H.,Hsiao, S. S. -Y.,Kao, S. -J.,&高树基.(2014).Isotopic composition of water-soluble nitrate in bulk atmospheric deposition at Dongsha Island: sources and implications of external N supply to the northern South China Sea.http://dx.doi.org/10.5194/bg-11-1833-2014.
MLA	Yang, J. -Y. T.,et al."Isotopic composition of water-soluble nitrate in bulk atmospheric deposition at Dongsha Island: sources and implications of external N supply to the northern South China Sea".http://dx.doi.org/10.5194/bg-11-1833-2014 (2014).