中国食物链氮素资源流动特征分析

活化氮引起的资源环境问题成为国际关注的热点。研究利用养分流动方法，利用模型量化氮素流动特征的指标，阐明我国食物链氮素流动特征。结果表明：随着GDP增长，在食物消费拉动下，2005年人均化肥、饲料、食物氮素消费量分别为1980年的2.1、2.2和1.3倍，养活一个中国人的资源代价在增加。中国食物链氮素库存量和流量大幅增长，1980年到2005年农田氮素总流量从2104×10⁴t增加到4355×10⁴t，动物生产体系氮素流量从745×10⁴t提高到2255×10⁴t，家庭消费系统氮素流量从313×10⁴t增加到436×10⁴t。然而，2005年食物链氮素生产效率仅为9%，废弃物循环率下降。与此同时，食物链氮素流动排放造成巨大的环境压力，2005年食物链系统进入环境的氮素为4 288×104 t，是1980年的2.4倍。

Analysis on the Feature of Nitrogen Flow from Food Chain Perspective in China

Increasing nitrogen (N) applications have greatly contributed to the increasing food production in China during the last four decades, but have also contributed to rapidly increasing N losses to groundwater, surface waters and air. However, the pathways and magnitude of these losses are not well known quantitatively. Here, we present the model based on the MFA to quantify the index of nitrogen flow characteristics and to deliberate the characteristics of nitrogen flow in the food chain perspective from 1980 to 2005 in China. The results showed that with the growth of GDP and food consumption, the amount of fertilizer, feed, the food nitrogen consumption per capita increased dramatically, being 2.1, 2.2 and 1.3 times in 2005 of that in 1980 respectively, and the resources cost to support one Chinese is increasing year by year. With the increasing of food demand, the nitrogen amount of pool and the flow in the food chain in China grew remarkably. In 2005, the amount of nitrogen flow of crop production, animal production and household consumption was 43.5, 22.6 and 4.4 Tg and that in 1980 was only 21.0, 7.5 and 3.1 Tg respectively. However, the nitrogen use efficiency of food in China was only 9% in 2005 and the waste recycling rate was decreased. Meanwhile, the remainder of nitrogen flow caused great pressure to the environment, which means that 42.9 Tg N lost to the atmosphere and water in 2005, which were 2.4 times of that in 1980. Hence, food chain system has become the channel of nitrogen activated. There is a clear scope to strongly optimize N use by virtue of new nutrient management modes under the view of food chain.