12月16日，國際著名雜志Science在線刊登了加拿大和美國研究人員的最新研究成果“A Coherent Signature of Anthropogenic Nitrogen Deposition to Remote Watersheds of the Northern Hemisphere,。”,，研究證實在化肥之前很久人類已經(jīng)在固氮了。
過去曾經(jīng)有這樣一個時期,，其間氮僅能被某些能夠打破氮原子間強有力的三鍵的微生物所利用,。 新的研究顯示，人類打斷了這一自然氮循環(huán)的時間可早至一個世紀之前,，在1895年左右,。 Gordon Holtgrieve及其同事知道，自工業(yè)化前以來，人類的活動可能使得排入到生物圈的活性氮的量增加了一倍 --- 大多是通過使用內(nèi)燃機和富含氮的肥料使然,。 然而,，在分析了整個北半球數(shù)個原始湖泊的沉積物核心中發(fā)現(xiàn)的同位素之后，這些研究人員發(fā)現(xiàn),，甚至在肥料生產(chǎn)變得普遍之前很久,，人類的活動即造成了生物圈中氮的顯著增加。 當與如今化肥生產(chǎn)所引起的直接溢流相比時,，這些氮水平的升高相對較小,。 但是，它們可能來自焚燒煤渣,，且它們可能足以大到影響整個北半球流域的氮平衡（主要為生產(chǎn)力）,，時間如今已經(jīng)超過一個世紀。 一則由James Elser撰寫的相關的觀點欄目更為詳細地解釋了這些發(fā)現(xiàn),。（生物谷Bioon.com）
doi:10.1126/science.1212267
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A Coherent Signature of Anthropogenic Nitrogen Deposition to Remote Watersheds of the Northern Hemisphere
Gordon W. Holtgrieve1,*, Daniel E. Schindler1, William O. Hobbs2, Peter R. Leavitt3, Eric J. Ward4, Lynda Bunting3, Guangjie Chen5,6, Bruce P. Finney7, Irene Gregory-Eaves5, Sofia Holmgren8, Mark J. Lisac9, Peter J. Lisi1, Koren Nydick10, Lauren A. Rogers1, Jasmine E. Saros11, Daniel T. Selbie12, Mark D. Shapley7, Patrick B. Walsh9, Alexander P. Wolfe13
Humans have more than doubled the amount of reactive nitrogen (Nr) added to the biosphere, yet most of what is known about its accumulation and ecological effects is derived from studies of heavily populated regions. Nitrogen (N) stable isotope ratios (15N:14N) in dated sediments from 25 remote Northern Hemisphere lakes show a coherent signal of an isotopically distinct source of N to ecosystems beginning in 1895 ± 10 years (±1 standard deviation). Initial shifts in N isotope composition recorded in lake sediments coincide with anthropogenic CO2 emissions but accelerate with widespread industrial Nr production during the past half century. Although current atmospheric Nr deposition rates in remote regions are relatively low, anthropogenic N has probably influenced watershed N budgets across the Northern Hemisphere for over a century.
