Science2014-06-13 4:01 PM

新西兰山脉的土壤风化没有速度限制 Rapid Soil Production Breaks Global Weathering "Speed Limit" in the Western Southern Alps, New Zealand

论文摘要 

在新西兰山区工作的科学家们报告了非常高的土壤风化率,这与先前的研究是矛盾的,因为那些研究提示山区的土壤风化是有速度限制的。因为风化过程可以从大气中抽提二氧化碳,因此这一发现对科学家们将山区理解为碳汇有着重要的意义。山区是否起着碳汇的作用一直存在着争论。这大体上是因为科学家们对该化学风化过程——在该过程中,空气中的二氧化碳会与地球表面的化学性化合物起反应并被锁入到这些化合物之中——是如何在山区发生变化的缺乏清晰的掌握,尤其是那些经常性地因为板块而升高的山区。(该抬升过程会暴露新的岩石和土壤以供风化过程发生作用。)有些人曾经提出,在山体抬升时清除了如此多的风化土壤,其所造成的侵蚀会因为缺乏原始成分而放缓--从而限制了这些山对碳截留的促成作用。为了弄清楚这一问题,Isaac Larsen及其同事从新西兰的南阿尔卑斯山西部采集了土壤样本;那里有一些世界上抬升最快的山脉。为了测量随着时间推移的风化速度,研究人员评估了一些特定的元素,如玻元素等,从土壤中的清除情况。研究人员说,与先前的研究——这些研究提示土壤的风化会随着抬升活动增加所致的侵蚀而下降——相反,在这里,土壤的风化会随着侵蚀的增加而增加。这有可能是因为受到推挤的山体表面并非如所预期的完全与土壤进行了剥离;相反,较潮湿的气候会让它们保持在原位而发生风化作用。研究人员将他们的土壤风化速度与全世界的数据汇编进行了比较并发现,他们的土壤风化速度是迄今为止最高的风化速度。Larsen等人的工作帮助量化了板块活动及侵蚀作为全球风化流通的驱动因子的重要性,并因而最终成为对大气二氧化碳的控制因素。它对目前的一个有争议的辩论,即山脉是否对全球风化、二氧化碳循环及气候有“重要作用”,也具有重要的影响.

Abstract 

Evaluating conflicting theories about the influence of mountains on carbon dioxide cycling and climate requires understanding weathering fluxes from tectonically uplifting landscapes. The lack of soil production and weathering rate measurements in Earth’s most rapidly uplifting mountains has made it difficult to determine whether weathering rates increase or decline in response to rapid erosion. Beryllium-10 concentrations in soils from the western Southern Alps, New Zealand, demonstrate that soil is produced from bedrock more rapidly than previously recognized, at rates up to 2.5 millimeters per year. Weathering intensity data further indicate that soil chemical denudation rates increase proportionally with erosion rates. These high weathering rates support the view that mountains play a key role in global-scale chemical weathering and thus have potentially important implications for the global carbon cycle.

Editor's Summary

Weathering Heights

The production of soil is the result of chemical weathering of rocks and minerals. In regions where tectonic uplift brings fresh material to Earth's surface, erosion and weathering can accelerate. Using chemical tracers, Larsen et al. (p. 637, published online 16 January; see the Perspective by Heimsath) measured soil production rates of over 2 millimeters per year in New Zealand's Southern Alps, which are some of the fastest uplifting mountains in the world. Because chemical weathering consumes CO2, these rapid rates may over time influence global climate.

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