Pitfalls and New Mechanisms in Moss Isotope Biomonitoring of Atmospheric Nitrogen Deposition

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• 作者：Xue-Yan Liu ; Keisuke Koba ; Cong-Qiang Liu ; Xiao-Dong Li ; Muneoki Yoh
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2012
• 出版时间：November 20, 2012
• 年：2012
• 卷：46
• 期：22
• 页码：12557-12566
• 全文大小：471K
• 年卷期：v.46,no.22(November 20, 2012)
• ISSN：1520-5851

文摘

Moss N isotope (未¹⁵N_bulk) has been used to monitor N deposition, but it remains questionable whether inhibition of nitrate reductase activity (NRA) by reduced dissolved N (RDN) engenders overestimation of RDN in deposition when using moss 未¹⁵N_bulk. We tested this question by investigation of 未¹⁵N_bulk and 未¹⁵NO₃^{鈥?/sup> in mosses under the dominance of RDN in N depositions of Guiyang, SW China. The 未15N_bulk of mosses on bare rock (鈭?.9鈥? was unable to integrate total dissolved N (TDN) (未15N = 鈭?.3鈥?, but it reflected 未15N-RDN (鈭?.5鈥? exactly. Moreover, 未15N-NO₃鈥?/sup> in mosses (鈭?.7鈥? resembled that of wet deposition (鈭?.9鈥?. These isotopic approximations, together with low isotopic enrichment with moss [NO₃鈥?/sup>] variations, suggest the inhibition of moss NRA by RDN. Moreover, isotopic mixing modeling indicated a negligible contribution from NO₃鈥?/sup> to moss 未15N_bulk when the RDN/NO₃鈥?/sup> reaches 3.8, at which maximum overestimation (21%) of RDN in N deposition can be generated using moss 未15N_bulk as 未15N-TDN. Moss 未15N-NO₃鈥?/sup> can indicate atmospheric NO₃鈥?/sup> under distinctly high RDN/NO₃鈥?/sup> in deposition, although moss 未15N_bulk can reflect only the RDN therein. These results reveal pitfalls and new mechanisms associated with moss isotope monitoring of N deposition and underscore the importance of biotic N dynamics in biomonitoring studies.}