城镇化对我国食物消费系统氮素流动及循环利用的影响

城镇化的快速发展,在改变养分氮素流动模式的同时带来了巨大的生态环境压力和严重的污染问题.以1982年、1992年和2002年我国城镇与农村居民食物消费系统氮素流动为对象,采用物质流分析方法,探讨了城镇化对氮素流动特征及循环利用率的影响.结果表明:2002年我国城镇居民人均消费氮量为4.770kg,高于农村居民(4.314kg)10%.1982年到2002年,随着城镇化率的提高,城镇居民消费的食物氮提高了145.3%,农村减少了8.1%;城镇排入水体环境的氮增加了18.4倍,而氮素循环利用率只有13.0%,降低了40个百分点.情景分析结果表明,如果在人口增加的同时,食物结构达到国家营养纲要的标准,到2010年我国植物性氮消费量比2002年将增多142.3万t,增加了37.6%,动物性氮消费量将增多53.8万t,增加了 27.1%,城镇产生的粪尿和垃圾中氮将增加126万t.因此,伴随城镇化快速发展,在带来食物氮素需求和环境排放氮素大幅度增加的同时,也会对动植物生产带来巨大压力.

The influence of urbanization on nitrogen flow and recycling utilization in food consumption system of China

The fast development of urbanization has brought the huge ecological pressure and serious environmentally pollution by changing nitrogen flux pattern. This article studied the nitrogen flux characteristics in food consumption system of household between the rural and the urban inhabitants of China in 1982,1992,2002 and explored the influence of urbanization on nitrogen flux and utilization by recycling through the material flow analysis method.The results showed that the average nitrogen consumption per capita of urban inhabitants in 2002 was 4.770kg, which was higher 10% than that of the rural inhabitants (4.314kg). From 1982 to 2002, nitrogen consumption with food by the urban inhabitants was increased by 145.3%, but reduced by 8.1% by the rural. With urbanization in china as meantime, the nitrogen dispersed into the water body from urban households in 2002 was increased by 18.4 times as much as that in 1982. In 1982, the difference in nitrogen recirculation ratio between urban and rural household was not big and both ratio were above 50%, but in 2002, nitrogen recirculation ratio in urban reduced to 13.0%, which was lower 40 percentage points compared to that of the rural. It was indicated that the nitrogen utilization by recycling would decrease significantly with increase of the urbanization ratio and the change of lifestyle.
The scenario analysis showed that nitrogen consumption in 2010 will be increased by 37.6%(net increase of 1.423 million tons) through plant produce,and by 27.1%(net increase of 538000 tons) through animal husbandry over 2002,if food constitute for chinese reaches the standard issured by National Nutrition Council. At same time, the nitrogen in urban waste and garbage in 2010 will increase by 1.26 million tons, compared to 2002. Therefore, the fast development of urbanization can not only results in large scale increase of nitrogen flux and environmental emissions, but also lead the huge pressure to the animal and crop production.