Study On Phosphorus Flow In Family System And Influence On Environment In China

With the growing of urbanization, the food consumption structure in urban and rural areas of China changes significantly, consequently the change of phosphorus flow model has led to tremendous pressure of ecological environment and serious pollution problems in cities and towns. Therefore, to understand the influence of urbanization on phosphorus flow characteristics, recycling, environment uses the method of material flow analysis analyzing the statistical data, survey data and literatures. The influence between urbanization and regional phosphorus balance in agro-ecosystem were analyzed in China and Beijing city were also studied. The results were shown as follows.1. The urbanization development will increase the consumption proportion of animal food greatly. The proportion of urban resident take in the phosphorus from animal food increase from 21% in the 80's to 41% in 2006; The proportion of rural resident take in the phosphorus from animal food increase from 7% in the 80's to 14% in 2006. The quantity of rural family take in animal phosphorus amount is the urban family 1/3. Scenario analysis showed that, if changing the food structure, the proportion of urban and rural resident take in the phosphorus from animal food would be 36%-38 % and 23 %-25 %.2. The quantity of phosphorus input family system is increasing. The quantity of phosphorus input urban family increased from 64,000 tons to 193,000 tons in 1981-2006, the ratio of increment is 8% per year. The quantity of phosphorus input urban family per capita between 275-335 grams. The quantity of phosphorus input rural family was about 300,000 tons from 1981 to 2000. After 2000, phosphorus input quantity has presented the declining trend. The quantity of phosphorus input rural family per capita was 355 grams, after 2000, it declined. Scenario analysis showed that, if changing the food structure, The quantity of phosphorus input urban and rural family would be 344,900 tons - 446,100 tons and 263,900 tons - 290,500 tons, 536-567 grams and 400-410 grams per capita.3. The quantity of phosphorus discharged into the water from family system was rising. The quantity of phosphorus discharged into the water from urban family was 5,000 tons, 25 grams per capita in1981, the quantity of phosphorus discharged into the water from urban family was 122,000 tons, 212 grams per capita in2006. The quantity of phosphorus discharged into the water from rural family was23,000 tons in1981, the maximum was104,000 tons in 2000, then reduced to93,000 tons in 2006. The urban family per capita contribution rate of phosphorus to water was rural family's 1.6 times. Scenario analysis showed that, the phosphorus of urban family would be 60%-80%, the urban family is main source of phosphorus discharged into the water.4. The phosphorus quantity of family system return to the farmland declined continually. The phosphorus return to the farmland which came from urban family was 46,000 tons and 228 grams per capita in 1981,22,000 tons and 38 grams per capita in 2006. The phosphorus return to the farmland which came from rural family was 211,000 tons and 264 grams per capita in 1981, 99,000 tons and 134 grams per capita in 2006. Scenario analysis showed that, if the human excreta recycle ratio enhanced, the quantity of phosphorus would be 2.2-2.7 times higher than the present.5. Phosphorus cycling ratio felt down rapidly. In the 80's, the phosphorus cycling ratio of urban family was 35%-70%, then dropped to 16%-30% in the 90's, the phosphorus cycling ratio wasl3%-15% in 2000-2006. In the 80's, the phosphorus cycling ratio of rural family was 62%-75%, then dropped to 47%-61% in the 90's, the phosphorus cycling ratio was43%-46% in 2000-2006. Scenario analysis showed that, if it change the food structure and enhance the human excreta recycle ratio, the phosphorus cycling ratio of urban family would be 34%-44%, the phosphorus cycling ratio of rural family would be 59%-67%.6. In the national system which was relatively close, the urbanization rate and nutrient cycling indicators have significant correlation. The fertilizer phosphorus input increased from 49.1 kg/hm~2 to 137.5 kg/hm~2 in1981-2005, increased 1.8 times. The phosphorus proportion which originated organic fertilizer gradually dropped from 41.9% to16.1% in 1981-2005. The surplus phosphorus quantity increased from 6.1 kg/hm~ to 70.9 kg/hm~2 in 1981-2005, the surplus phosphorus quantity increment is 11% per year.7 Compared with 1995 and 2005 in Beijing various areas, nutrient cycling indicators enhanced along with urbanization rate. The amount of fertilizer phosphorus input is suburbs > exurbs > urban. The proportion of organic fertilizer input is urban > exurbs > suburbs. The surplus phosphorus quantity is urban > exurbs > suburbs. The urbanization rate and fertilizer has negative significant correlation in Beijing various areas in 1995, the urbanization rate and organic fertilizer has significant correlation, the correlation between urbanization rate and surplus phosphorus was not remarkable. The correlation between urbanization rate and nutrient cycling indicators were not remarkable.