In atmospheric environment monitoring, the reasonable placement of sampling points and number of points is one of the important processes to achieve monitoring purposes and ensure the representativeness of data. According to the distribution of pollution sources and different monitoring purposes, the layout methods of sampling points are divided into four types: grid layout method, concentric circle layout method, sector layout method, and functional area layout method When there are many and scattered pollution sources within the monitoring range, this method is used to set up sampling points. Draw the entire monitoring area as a square grid, and set sampling points at the nodes or centers of the grid lines. The number and spacing of points should be determined based on manpower, material resources, and actual situations Concentric circle point layout method; There are multiple concentrated pollution sources. When investigating the pollution situation in various directions and distances around the pollution source, draw several concentric circles on the ground with the pollution source as the center, and then draw several radiation lines from the center to the surrounding area. The distance between the concentric circles increases outward, such as 4:10:20:40. Set several sampling points on each circle For a single elevated point source, with the smoke plume flow direction as the axis, a fan shaped area is determined on the ground in the downwind direction of the point source as the distribution range, and the angle of the fan is generally about 45., It can also be taken as 60., But it should not be greater than 90.. The sampling points are located on several arcs (such as three or four) at different distances from the point source within the fan-shaped surface. One of the arcs must be located at the distance with the highest frequency of maximum ground concentration occurrence (about 10 times the effective height of the chimney). At least three sampling points are set on each arc, with an interval of 10o~20o between each other The functional area layout method divides the area to be monitored into several functional areas such as industrial areas, residential areas, commercial areas, transportation hubs, cultural areas, parks, etc. Each functional area is equipped with a fixed number of monitoring points In actual atmospheric environment monitoring, the use of the above methods for sampling points is often dominated by one method, and necessary adjustments are made using other methods to make the sampling point layout more representative. In addition, attention should also be paid when arranging points: (1) When arranging points in areas with frequent traffic, the position of the points should be away from the edge of the road by 15~30m; (2) All sampling points should avoid obvious obstacles such as forest land and high walls; (3) When arranging points on the windward side of tall buildings, the distance between the points and the building should be 10 times the height of the building, and at least 2 times or more should be maintained when conditions permit According to the different forms, concentrations, and analytical sensitivity of pollutants in the atmosphere, gas sample collection methods can be divided into two types: non concentrated sampling method and concentrated sampling method Non concentrated sampling method, also known as direct sampling method. When the content of the tested substance in the atmosphere is high or the sensitivity of the analysis method is high, a small amount of gas sample can be collected using plastic bags, syringes, or other suitable containers for analysis and measurement When the concentration of the tested substance in the atmosphere is low or the sensitivity of the analysis method is not high enough, the concentration sampling method should be used to collect gas samples. The most widely used concentration sampling methods include filtration or solution absorption (1) Filtering method. This method is used for the collection of particulate pollutants. When sampling, clamp the filter paper or organic filter membrane onto a dedicated sampling head, and connect the sampling head to the flow meter and air pump. After starting the air extraction pump, gas molecules pass through the filter paper (or membrane) and are measured by a flow meter. They are then discharged through the air extraction pump, and particulate matter is trapped on the filter paper or membrane. The longer the air extraction time, the more particulate matter is trapped on the filter paper (2) Solution absorption method. The instrument commonly used for collecting molecular or vapor pollutants and capturing the substance to be measured is an absorption tube, which contains an absorption liquid that can react with the substance to be measured. The absorption tube is connected to a flow meter and an air pump. Start the air pump, and when the atmosphere passes through the absorption liquid containing the absorption tube in the form of bubbles, a dissolution of the gas to be measured or a chemical reaction with the absorption liquid occurs at the gas-liquid interface, leaving the substance to be measured in the absorption liquid. At the same time, the molecules inside the bubble rapidly diffuse to the surface of the bubble due to their own thermal motion, and continue to undergo dissolution or chemical reactions. If this continues, the absorption process of the tested substance is completed. Obviously, the longer the ventilation time, the higher the concentration of the substance to be measured in the absorption solution. Therefore, the sampling process is the concentration process of the substance to be measured. In addition to filtration and solution absorption methods, the concentration sampling method also includes solid sampling tube retention method and low-temperature condensation method