Effects of global change during the 21st century on the nitrogen cycle
Effects of global change during the 21st century on the nitrogen cycle
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DOI：
10.5194/acp-15-13849-2015
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发表时间：
2015-01-01
影响因子：
6.3
通讯作者：
Galloway, J. N.
中科院分区：
文献类型：
--
作者：
Fowler, D.;Steadman, C. E.;Galloway, J. N.
世纪初的全球氮（N）循环已被证明受到来自人类活动的活性氮（N-r）输入的强烈影响，包括燃烧相关的NOx、工业和农业固氮，2010年估计为220 TgNyr（-1），这大约等于未管理的陆地和海洋生态系统中生物固氮的总和。根据目前的预测，21世纪气候和土地利用的变化将增加生物和人为固定，到2100年左右，总固定量将达到约600 TgNyr（-1）。如果农业中氮的利用效率得到提高，并对燃烧相关的排放采取控制措施，则人类活动直接贡献的比例不太可能大幅增加。Nr处理过程中对气候的最大响应之一是向大气排放NH3，假设在没有增加人类活动的情况下全球表面温度变化5 ℃，估计NH3将从2008年的65 TgNyr（-1）增加到2100年的93 TgNyr（-1）。随着对动物产品需求的增加，排放量发生变化，综合影响将使NH3排放量增加到135 TgNyr（-1）。另一个主要变化是气候变化对气溶胶成分的影响，特别是在较温暖的气候中，NH 4 NO 3在接近地面的地方升华形成HNO 3和NH 3的增加，它们比气溶胶更快地存款到陆地表面。在20世纪70年代至80年代，污染地区（特别是欧洲和北美）上空的无机气溶胶以（NH 4）（2）SO 4为主，SO2排放量的大幅减少已将这些地区大气中的大部分SO 42-清除。来自人为排放的无机气溶胶现在主要是NH 4 NO3，这是一种挥发性气溶胶，对PM10和全球人类健康影响以及富营养化和气候影响有很大贡献。据估计，NH 4 NO3的挥发性和气相分解产物HNO 3和NH3的快速干沉积正在减少这些地区N-r的运输距离、沉积足迹和国家间交换。这些都是以区域或国家为基础的，已经大大减少了氮对敏感土壤、沃茨和大气的输入。迄今为止，还没有人试图制定一项全球战略来调节人类对氮循环的投入。然而，考虑到全球Nr使用的规模、未来潜在的增加以及Nr以多种形式大量泄漏到土壤、沃茨和大气中，需要采取国际行动。目前的立法将无法在全球范围内实现减排规模，以从氮沉降对敏感生态系统的影响中恢复过来，或减少向全球大气中的N2 O排放。这种变化需要在全球经济中大幅提高氮的使用效率，同时优化运输和粮食消费模式。这将允许减少氮的使用、对大气的投入和对敏感生态系统的沉积。这种变化将带来巨大的经济和环境共同利益，有助于推动采取必要的行动。
The global nitrogen (N) cycle at the beginning of the 21st century has been shown to be strongly influenced by the inputs of reactive nitrogen (N-r) from human activities, including combustion-related NOx, industrial and agricultural N fixation, estimated to be 220 TgNyr(-1) in 2010, which is approximately equal to the sum of biological N fixation in unmanaged terrestrial and marine ecosystems. According to current projections, changes in climate and land use during the 21st century will increase both biological and anthropogenic fixation, bringing the total to approximately 600 TgNyr(-1) by around 2100. The fraction contributed directly by human activities is unlikely to increase substantially if increases in nitrogen use efficiency in agriculture are achieved and control measures on combustion-related emissions implemented.Some N-cycling processes emerge as particularly sensitive to climate change. One of the largest responses to climate in the processing of Nr is the emission to the atmosphere of NH3, which is estimated to increase from 65 TgNyr(-1) in 2008 to 93 TgNyr(-1) in 2100 assuming a change in global surface temperature of 5 degrees C in the absence of increased anthropogenic activity. With changes in emissions in response to increased demand for animal products the combined effect would be to increase NH3 emissions to 135 TgNyr(-1). Another major change is the effect of climate changes on aerosol composition and specifically the increased sublimation of NH4NO3 close to the ground to form HNO3 and NH3 in a warmer climate, which deposit more rapidly to terrestrial surfaces than aerosols. Inorganic aerosols over the polluted regions especially in Europe and North America were dominated by (NH4)(2)SO4 in the 1970s to 1980s, and large reductions in emissions of SO2 have removed most of the SO42- from the atmosphere in these regions. Inorganic aerosols from anthropogenic emissions are now dominated by NH4NO3, a volatile aerosol which contributes substantially to PM10 and human health effects globally as well as eutrophication and climate effects. The volatility of NH4NO3 and rapid dry deposition of the vapour phase dissociation products, HNO3 and NH3, is estimated to be reducing the transport distances, deposition footprints and inter-country exchange of N-r in these regions.There have been important policy initiatives on components of the global N cycle. These have been regional or country-based and have delivered substantial reductions of inputs of Nr to sensitive soils, waters and the atmosphere. To date there have been no attempts to develop a global strategy to regulate human inputs to the nitrogen cycle. However, considering the magnitude of global Nr use, potential future increases, and the very large leakage of Nr in many forms to soils, waters and the atmosphere, international action is required. Current legislation will not deliver the scale of reductions globally for recovery from the effects of Nr deposition on sensitive ecosystems, or a decline in N2O emissions to the global atmosphere. Such changes would require substantial improvements in nitrogen use efficiency across the global economy combined with optimization of transport and food consumption patterns. This would allow reductions in Nr use, inputs to the atmosphere and deposition to sensitive ecosystems. Such changes would offer substantial economic and environmental co-benefits which could help motivate the necessary actions.