论文部分内容阅读
从1961～1997年,因人类活动而输入到美国的氮翻了一番,特别是在上个世纪60年代和70年代,其增长量最大。尽管无机氮肥的使用量增长最大,但矿物燃料燃烧所造成的NO_x排放,也有明显的增加。1961年,美国农业生产系统中的生物固氮量是活性氮的最大来源;到了1997年,尽管生物固氮量也有增加,但相比而言,无机氮肥的使用和NO_x的排放增加得更快,成为两个最大的氮源。1961～1997年,在输入到美国的活性氮中,有2/3发生了脱氮反应或者是被贮存在土壤与生物群落之中,有1/3输出到境外。在输出到境外的这部分氮中,通过河流流到海洋中的分量最大,其次是通过粮食和饲料出口而到其它国家以及通过大气平流传输到了海洋中。动物性蛋白的消费是美国农业系统中氮使用的主要驱动因子,如果饮食方式或农业生产方式不发生改变,在来来30年的时间里,美国肥料的使用量将继续增长,流向海洋中的氮通量将可能再增长30%,但也有可能出现下降。
From 1961 to 1997, the nitrogen input to the United States for human activities doubled. Especially in the 1960s and 1970s, it had the largest growth. Although the use of inorganic nitrogen fertilizer increased the most, the emission of NO x caused by the combustion of fossil fuels also increased obviously. In 1961, the biological nitrogen fixation of agricultural production system in the United States was the largest source of active nitrogen. By 1997, in spite of the increase of biological nitrogen fixation, the use of inorganic nitrogen fertilizer and the emission of NO x increased more rapidly, becoming The two largest nitrogen sources. Between 1961 and 1997, about two-thirds of the active nitrogen input to the United States was denitrified or stored in soils and biomes, with one-third exported outside the country. Of this part of the nitrogen exported to the outside world, the largest part of the nitrogen that flows through the river to the ocean, followed by exports of food and feed to other countries and through the atmospheric advection to the ocean. The consumption of animal proteins is a major driver of nitrogen use in the US agricultural system and the use of US fertilizers will continue to increase in the coming 30 years if the dietary patterns or agricultural practices do not change Nitrogen flux will likely increase by 30%, but it is also likely to decline.