Study On The Atmospheric Environment Capacity In Lanzhou

With the acceleration of the process of urbanization,industrialization and regional economic integration,the increasing air pollutants emmited by industrial sources,transportation sources and living sources has made air pollution problems in China increasingly prominent;Air pollution has caused great threats and damages to public health,ecological environment and social economy,which has seriously restricted the sustainable development of regional social economy.In order to improve regional environmental air quality,ensure human living enviroment,implement regional sustainable development strategies,promote industrial restructuring and improve control level of air pollution,it is very necessary to control the amount of the total air pollutant.In the study of total air pollution control,according to regional meteorological conditions,determining the geographic regional total control coefficient A and the pollution diffusion space is the basis for rationally accounting for the atmospheric environmental capacity and further scientifically determining the total pollutant emissions.Firstly,the capacity measurement factors are determined according to relevant National policy and the environmental quality of Lanzhou City,At the same time,the spatial extent of pollution diffusion?control area?is determined by GIS method.Secondly,this study first used the WRF model to simulate the boundary-layer heights of the downtown area of Lanzhou?Chengguan District,Anning District,Xigu District,Qilihe District?and the wind speeds at different levels within the boundary layer,calculating the atmospheric environmental capacity of SO₂,NOx and VOC_S in the downtown area of Lanzhou by the A value method.Finally,it compared the total emissions of SO₂ and NOx in the downtown area of Lanzhou in 2016 obtained from MEIC checklist statistics with the environmental capacity of SO₂ and NOx under normal conditions,and combined with the results of regional environmental quality's monitoring data,to explain the rationality of setting atmospheric environmental capacity.In addition,in order to cope with the heavy pollution situation that may occur when low-level temperature inversion occurs,this study also gives the corresponding atmospheric environmental capacity when the inversion temperature appears in different heights?100m and 150m?.The conclusions are as follows:?1?The annual average values of PM₁₀ and PM_2.5 monitored by Lanzhou Background Point?Yuzhong station?in 2013-2016 exceeded the national secondary standard,indicating that PM₁₀ has already no environmental capacity;Therefore,the total control factors of this study are SO₂,NOx and VOCs;At the same time,the GIS method is used to determine the spatial extent of pollution diffusion from the perspective of pollution diffusion unit.?2?The A value of the downtown area of Lanzhou has seasonal variation characteristics,which is larger in spring and summer,and smaller in autumn and winter.The main reason for the larger A value in spring and summer is that the height of boundary layer and the average wind speed in the boundary layer are relatively larger,while in winter,the opposite is true;To achieve the goal of continuous and stable regional environmental quality,this study selects the A value under unfavorable weather conditions of winter in each district to determine the total amount of air pollutants discharged from each district.?3?Under normal conditions?A value method based on average mixed layer height?,the basic atmospheric environmental capacities of SO₂,NOx and VOCs in downtown Lanzhou are:2.15×10⁴t/a?1.21×10⁴t/a and 4.01×10⁴t/a,respectively;The changing atmospheric environmental capacity of SO₂ and NOx is:0.68×10⁴t/a and0.08×10⁴t/a,respectively;the atmospheric environmental capacities of SO₂,NOx and VOCs are:2.83×10⁴t/a?1.29×10⁴t/a and 4.01×10⁴t/a,respectively.?4?The actual annual emissions of SO₂ in 2016?1.62×10⁴t/a?did not exceed the limit of atmospheric environmental capacity?2.83×10⁴t/a?,and there is still a margin?1.21×10⁴t/a?.This is consistent with the current situation that the average annual concentration of SO₂ in the four national air quality control points in Lanzhou City in2016 reached the standard;The actual annual emissions of NOx?3.16×10⁴t/a?have exceeded the calculated capacity value?1.29×10⁴t/a?,NOx already has no environmental capacity?-1.87×10⁴t/a?.This is consistent with the current situation that the average annual concentration of NOx in the four national air quality control points in Lanzhou City exceeded the standard;in this study,the atmospheric environment capacity of the downtown area of Lanzhou calculated by the A-value method is consistent with the regional pollution diffusion characteristics,and the calculation results are reasonable.?5?When the height of inversion temperature of Lanzhou is 100m,the atmospheric environmental capacities of SO₂,NOx and VOCs are:1.03×10⁴t/a?0.29×10⁴t/a and 0.66×10⁴t/a,respectively.Comparing with the environmental capacity under normal conditions,the reduction ratios are 63.5%,77.6%and 83.5%,respectively.When the height of inversion temperature of Lanzhou is 150m,the atmospheric environmental capacities of SO₂,NOx and VOCs are:1.29×10⁴t/a?0.42×10⁴t/a and1.12×10⁴t/a,Comparing with the environmental capacity under normal conditions,the reduction ratios are 54.6%?67.5%and72.1%.