Urban Ecological Security Research Based On Disaster-causing Mechanism Of Oxygen Imbalance

As early as 1842,Engels had a classic description of the oxygen imbalance disaster in his book named《The State of the Working Class in Britain》.At present,the situation of the rapid increase of net oxygen consumption has become grim worldwide.Oxygen is no longer an endless natural resource.Unfortunately,the problem of oxygen imbalance receives far less attention than greenhouse gas and haze particles.Oxygen concentration in air,as the ecological characterization of environmental quality and the regulating object of public security,is not as strictly restrained as other quantitative indicators,such as green coverage rate,and soil erosion rate.Under the framework of urban ecological security,this paper systematically constructs the theory of urban development affecting oxygen imbalance.The atmospheric movement in Yancheng City remains relatively stagnant during the research period(from 2000 to 2015).It takes the urban as a large-scale closed space to study the oxygen imbalance appeared by the combined action of its own oxygen emission process and oxygen consumption process.Depending on the theoretical structure and location conditions,74 large cities selected in China are compared one by one.Yancheng is the best choice as the case region of oxygen imbalance.Based on the monitoring scheme and disaster-causing mechanism,urban ecological security analyzing,controlling and warning are carried out by adopting the methods of literature review,holographic information analysis,big data statistics,intelligent multi-model integration research,etc.The results show that:1.The hydrothermal factors,crop varieties,vegetation types and community patterns of Yancheng City determine the fluctuation and differentiation of oxygen emission in space-time dimension.Natural disasters triggered by climate anomalies such as terrible cold,high temperature,drought and flood will reduce the city’s ability to resist the risk of oxygen imbalance.2.The burning of coal occupies a majority share of oxygen consumption,and the main contradiction of oxygen imbalance is that oxygen consumption increment is greater than oxygen emission increment.The key driving force to expand the extent of oxygen imbalance includes industrial intensity and economic development.Human activities dominate disaster-pregnant environment and make the ecosystem productivity,energy consumption and land use out of order as a whole,which is the root of unsafe environmental factors.3.The complete materials supply system built on construction land adsorbs high-energy-consuming enterprises and high-value-output entities.When calibrating the relationship between land use environment and oxygen emission/consumption,amount of oxygen consumption should be subject to construction land in the disaster-causing model.The average value of the research period is 0.02 Tg O/km~2/a.Net primary productivity(NPP)is calculated by improved CASA model based on remote sensing and physiology.According to NPP grids,amount of oxygen emission should be subject to cultivated land(0.0019 Tg O/km~2/a),woodland(0.002 Tg O/km~2/a),grassland(0.0011 Tg O/km~2/a),water area(0.0009 Tg O/km~2/a)and unused land(0.0012 Tag O/km~2/a)respectively.4.Relying on characteristics of oxygen imbalance and disaster-causing mechanism,the probability of disaster is calculated by“regional oxygen balance coefficient”,which is segmented into four levels:very safe,general safe,unsafe and very unsafe.It is recognized that the regions of Tinghu,Dongtai,Funing,Xiangshui are high-probability of oxygen imbalance disaster,and that the months of January,February,November,December and the years of climate anomalies are high-frequency.The spatial relationship is set up by logistic regression.The critical hazard sources such as point elements,and traffic lines are identified;Meanwhile the harmful consequences of independent variables acting on dependent variables are identified either.5.Grasping carrier of disaster-pregnant environment as the main line to perform dynamic analysis,we adopt the NSGA-II(A Fast Elitist Non-Dominated Sorting Genetic Algorithm for Multi-objective Optimization)method combined with policy essentials,objective functions and constraint conditions.Taking 2025 as the expected year,we plan three future scenarios(benchmark,optimization and green development)and divide the catastrophe of disaster into three stages(post-disaster,mid-disaster and pre-disaster).The result shows that the oxygen deficit of the benchmark scenario in2025(post-disaster)is 75.25 Tg O,the“regional oxygen balance coefficient”is 0.88%,the oxygen as a natural resource have entered the depletion stage,and the qualitative change of hypoxia in air will be completed in less than a year.6.With the help of CLUE-S(Conversion of Land Use and its Effects at Small region extent)model,control measures including development control,sectional management,ecological protection and zonal avoidance are fulfilled.It is found that the optimized scenario will make public environment in 2025 better than that in 2015,so it is recommended.By means of landscape evaluation and design,the adjustment direction,restoration direction and oxygen exchange channels are put forward.Aiming at the goal of guaranteeing urban safety and human-oriented security,warning system positioned for feedback of transverse catastrophe of oxygen imbalance is proposed.