Dynamic Changes Of Nitrogen Footprint And Its Affecting Factors In Minjiang Basin Of Fujian Province

Large amounts of artificial active nitrogens are emitted to the environment,causing lots of negative effects to river basins.Minjiang River as the first largest river in Fujian Province,the continuous increase of people's activity strength had caused lots of negative effects to the ecological environment in such river basin.Therefore,taking Minjiang River Basin as research object,this paper conducted analysis on the dynamic change of nitrogen footprint in the basin during 2000-2015 and its influence factors applying nitrogen footprint theory.The research results can not only expand the application scope of nitrogen footprint,but also have certain guidance significance to nitrogen management in Minjiang river basin.The obtained research results mainly include:(1)The per capita nitrogen footprint in Minjiang River Basin during 2000-2015 fluctuated at 23.15 kg N/a-27.48 kg N/a,generally presenting dynamic growth trend,and per capita nitrogen footprint increased by 18.8%in 16 years.Food production nitrogen footprint is the biggest component of nitrogen footprint in the river basin with annual proportion at 63%;food consumption nitrogen footprint accounted for 20%,and the annual proportion of energy accounted for 17%.Food consumption nitrogen footprint showed first decrease and then increase trend,while the nitrogen footprint of food production and energy presented gradual upward trend.Seen from sub-basin,except Meixi sub-basin had low per capita nitrogen footprint,other sub-basins showed certain growth trend.(2)The nitrogen footprint of urban and rural residents' food had certain differences,mainly due to food consumption and food consumption structure.Nitrogen footprint change of rural residents' food is mainly subject to the consumption decrease on food and vegetables as well as the increase of consumption on meat products.Nitrogen footprint increase in urban areas is mainly originated from the consumption increase on high nitrogen food(aquatic products,pork and poultry meat).Reasonably guiding dietary habits of urban and rural residents is the important method for reducing food nitrogen footprint.(3)After conducting relevant analysis on the relation of per capita disposable income,per capita regional GDP,Engel coefficient,proportion of educated population(above junior college)as well as residents' consumption level,it is found that nitrogen footprint in the basin had significant positive correlations with per capita disposable income,residents' consumption level and level of education,but significant negative correlation with Engel Coefficient,showing that economic development is the important driving force of nitrogen footprint.(4)Net nthropogenic nitrogen input had significant correlation(R2=0.78,p<0.01)with net nitrogen footprint,showing that to a certain extent,large amounts of nitrogen input in the basin influenced nitrogen emission of people's activities.By virtue of comparison on the two,it is found that the ratio continuously increased during 2000-2015,showing that nitrogen input in the basin more and more emitted to the environment,thus improving the utilization rate on nitrogen input has important significance on reducing nitrogen footprint.(5)Nitrogen footprint has certain influence to water quality(ammonia nitrogen concentration)of the basin.Seen from relevancy,urban nitrogen footprint was more sensitive to ammonia nitrogen content in water body of the basin(r=0.52,p<0.05).The increase of nitrogen footprint shows that more active nitrogens had emitted to the environment,which may result in the further decrease of water quality of the basin,and further deterioration of its ecological environment...