Study On Atmospheric PM_2.5pollution Characteristics And The Source Reduction Strategy Of Anthropogenic Pollution Sources In Changchun

According to Report on the State of the Ecology and Environment in China,the proportion of cities at prefecture level and above meeting ambient air quality standards increased from 29.3%to 64.3%of all cities from 2017 to 2021,and ambient air quality has improved significantly.However,since China began monitoring fine particulate matter(PM_2.5)at the end of 2013,PM_2.5has always been the primary pollutant of air pollution.The source,generation and migration transformation process of PM_2.5 are complex,with strong spatial and temporal heterogeneity,which can have serious adverse effects on human production and life,and is considered to be one of the most difficult compound air pollutants to manage at present.The management of PM_2.5 is a long-term and arduous task.Government departments at all levels have also put forward early warnings for heavy polluted weather,but the emergency response has not been effective.As technology develops and people’s living standards continue to improve,solutions to PM_2.5pollution problems should be pursued at a lower cost and with a smaller impact area.For this reason,in the study of emission reduction from anthropogenic sources of PM_2.5 in cities and towns,the construction of more accurate emission reduction implementation plans becomes a key issue to be addressed at this stage in order to achieve environmental management goals.Taking Changchun as the study area,this thesis uses theories and methods such as the CMAQ model,trajectory analysis and the revenue sharing contract model to analyze the pollution characteristics of PM_2.5 and the spatial and temporal distribution and impacts of pollution sources.The emission reduction scenarios and precise emission reduction plans under long-term and short-term emergency and other control objectives are designed,and the market facilitation mechanism for residential source electric heating emission reduction countermeasures are explored.The main research findings of the thesis are as follows.（1）Analysis of PM_2.5 pollution characteristics in Changchun.The most distinctive feature of PM_2.5 pollution in Changchun is the seasonal difference,with PM_2.5 ambient air quality concentrations being highest in winter and lowest in summer.In winter,there are the most polluted days with daily average concentrations greater than 75μg/m³,with a clear bimodal pattern within a day,and peaks occur between 9.00am-11.00am and 9.00pm-2.00am respectively.The highly polluted area within the built-up area of the central city is the core area within the boundary of the city bypass.Anthropogenic sources of PM_2.5 emissions are the highest from residential and industrial sources,accounting for 49.7%and 38.6%of total emissions respectively.Industrial and residential sources contribute the most to the ambient quality concentration of PM_2.5,ranging from30.6%to 36.4%and 23.6%to 31.8%respectively.The ranking of contribution is not consistent with the ranking of emissions.（2）The PM_2.5 emission reduction scenarios were designed and modelled under the long-term control objective of low health risk.The scenario parameters were set with reference to the medium and long-term planning objectives of Changchun City,taking into account the impact of climate policy.The three scenarios are"low","medium"and"high".The"low"emission reduction scenario reduces total PM_2.5 emissions by 22.0%,which basically achieves China’s secondary ambient air quality standard for PM_2.5 and is close to the target concentration value recommended by World Health Organization（WHO）for Stage 1.The"medium"emission reduction scenario reduces total PM_2.5 emissions by 52.5%,which will achieve the WHO recommended Stage 1 target and is close to the Stage 2 target concentration value.The"High"emission reduction scenario will reduce total PM_2.5 emissions by 79.3%,which will achieve the WHO recommended Stage 4 target and is close to the guideline target concentration value,while basically achieving China’s PM_2.5Tier 1 ambient air quality standard.The health effects are assessed as an average 90.6%reduction in all-cause mortality,significantly reducing health risks.However,there is some short-term health risk from 24-hour concentrations during the winter heating months.（3）In response to the short-term emergency control objectives of heavy pollution events,the grid-based precision control scheme was designed based on the gridded system of the ambient air quality model,with trajectory traceability analysis as the core technical approach.This design of the plan follows the laws of pollutant transport and dispersion.It combines trajectory analysis with meteorological-chemical transport models to determine more precise control parameters such as control area,control time,and control intensity.By doing so,it aims to implement short-term emergency control strategies with smaller social impact and lower costs.The grid-based precision control scheme developed in the two retrospective case studies has the following advantages compared to the region-wide pollution abatement scheme:firstly,it significantly reduces the control area,with the number of control grids accounting for 15.6%and 25.0%of the region-wide grids and 44.1%and 57.3%of the Changchun administrative district grids;secondly,it determines a more suitable control time of 24 hours in advance based on PM_2.5 concentration and IAQI prediction results.A more suitable control time of 24 hours in advance was determined.This study has demonstrated the feasibility of the scheme in the following 3 aspects:firstly the scheme achieves the PM_2.5 concentration reduction target effectively;secondly,under the principle of operability,the specific abatement sectors are identified as industrial sources,transport sources and residential sources,which are highly implementable;finally accounting for the abatement costs of industrial sources among them,compared with the total abatement costs of all industrial enterprises in the city,the 1st case is reduced by 29.4%and the 2nd case is increased by0.3%.Taking into account the fact that only some regions pay certain other costs in pollution abatement,the scheme is also acceptable in terms of total costs.（4）The design of the scheme has been further confirmed as operational by predictive practical exercises.Analysis of countermeasures to reduce PM_2.5 emissions from residential heating in winter.In view of the high pollutant emissions and the difficulty in reducing emissions from the burning of coal in winter heating,a revenue-sharing contract model is implemented between the equipment supplier and the electricity supplier in the supply chain for the"coal to electricity"energy substitution in the electric heating method,based on market research on the application of electric heating technology and game relationship analysis of the market structure,a study on the mechanism to facilitate the operation of the electric heating market for residential sources was conducted..This model has the advantages of high market allocation efficiency and low management costs,which can effectively promote the smooth operation of the electric heating market and help reduce pollutant emissions from residential sources.The revenue sharing contract model designed in this thesis is for the equipment supplier to first reduce the price of the equipment to attract consumers to use it and expand the market size;then the electricity supplier shares the electricity revenue to the equipment supplier to compensate for the loss of revenue of the equipment supplier.The results of the benefit-sharing scenario show that the model is feasible to be applied to the electric heating market.When the replacement rate of electric heating for residential customers is 70%,the residential source emission reduction rate can reach up to 61.9%,which can achieve the emission reduction requirement of residential sources in the"high"emission reduction scenario.