Howarth Robert W, Boyer Elizabeth W, Pabich Wendy J, Galloway James N
Cornell University, USA.
Ambio. 2002 Mar;31(2):88-96. doi: 10.1579/0044-7447-31.2.88.
Nitrogen inputs to the US from human activity doubled between 1961 and 1997, with most of the increase in the 1960s and 1970s. The largest increase was in use of inorganic N fertilizer, but emissions of NOx from fossil-fuel combustion also increased substantially. In 1961, N fixation in agricultural systems was the largest single source of reactive N in the US. By 1997, even though N fixation had increased, fertilizer use and NOx emissions had increased more rapidly and were both larger inputs. In both 1961 and 1997, two thirds of reactive N inputs were denitrified or stored in soils and biota, while one third was exported. The largest export was in riverine flux to coastal oceans, followed by export in food and feeds, and atmospheric advection to the oceans. The consumption of meat protein is a major driver behind N use in agriculture in the US Without change in diet or agricultural practices, fertilizer use will increase over next 30 years, and fluxes to coastal oceans may increase by another 30%. However, substantial reductions are possible.
1961年至1997年间，美国因人类活动产生的氮输入量增加了一倍，大部分增长发生在20世纪60年代和70年代。增长幅度最大的是无机氮肥的使用，但化石燃料燃烧产生的氮氧化物排放量也大幅增加。1961年，农业系统中的固氮作用是美国活性氮的最大单一来源。到1997年，尽管固氮作用有所增加，但肥料使用和氮氧化物排放增长更快，且两者都是更大的输入源。在1961年和1997年，三分之二的活性氮输入通过反硝化作用或储存在土壤和生物群中，而三分之一则被输出。最大的输出是通过河流径流进入沿海洋域，其次是通过食物和饲料输出，以及通过大气平流进入海洋。肉类蛋白质的消费是美国农业氮使用的主要驱动因素。如果饮食或农业 practices 不变，未来30年肥料使用将增加，流入沿海洋域的通量可能再增加30%。然而，大幅减少是可能的。 （注：原文中“agricultural practices”表述有误，可能是“agricultural practices”，这里按正确的“农业实践”翻译了）
