Analysis of the entire installation process of air quality monitoring stations: key points from site selection to operation and maintenance
1、 Site selection planning and environmental adaptation
Geospatial requirements
Horizontal diffusion conditions: Avoid vortex areas formed by obstacles such as high-rise buildings and trees, and prioritize open areas to ensure unobstructed airflow. According to the Technical Specification for the Layout of Environmental Air Quality Monitoring Points, the distance between urban monitoring points and the nearest obstacle must be greater than twice the height of the obstacle.
Vertical gradient control: The height of the sampling port from the ground should be within the range of 1.5-15 meters, and the traffic pollution monitoring point can be appropriately reduced to 3 meters, but not lower than the height of the roof. It is recommended to set up multi-level monitoring in industrial areas to capture the vertical distribution characteristics of pollutants.
Special terrain correction: Mountain cities need to consider the influence of valley wind circulation and place stations above the ridge line; Coastal areas should avoid turbulent disturbance zones at the intersection of sea and land winds.
Prevention and control of interference from cultural activities
Stay at least 50 meters away from fixed sources of pollution (chimneys, exhaust pipes), and no points are allowed around the restaurant oil fume exhaust outlets.
Vibration sensitive areas (along subway lines, heavy machinery operation areas) need to be equipped with shock-absorbing bases, and the noise background value should not exceed 55dB (A).
Electromagnetic radiation protection: Keep a distance of at least 30 meters from high-voltage transmission lines, and if necessary, use a double-layer copper mesh shielding cover to wrap the instrument compartment.
2、 Hardware system integration deployment
Infrastructure supporting construction
Bearing foundation: The thickness of the concrete pouring platform is ≥ 15cm, with a built-in Φ 12mm threaded steel mesh (20 × 20cm), and M16 anchor bolts are pre embedded for fixing the bracket.
Lightning protection system: The height of the independent lightning rod is ≥ 1.5 meters, the grounding resistance is<4 Ω, and the signal line is connected to the grounding terminal block of the lightning arrester.
Temperature control guarantee: The double-layer insulation box is equipped with semiconductor refrigeration chips (TEC1-12706 type), and the temperature inside the box is controlled at 25 ± 2 ℃ in summer and above 15 ℃ in winter.
3、 On site construction standard process
Modular assembly process
Bracket assembly: Hot dip galvanized steel pipes (φ 80 × 4mm) are welded into a three-dimensional frame, and silicone sealant is applied to the flange connections for waterproofing. The torque of each node meets the 8.8 level bolt standard specified in the national standard GB/T 3098.1.
Pipeline laying: PVDF hard sampling pipes are laid overhead along the bridge, with a slope of ≥ 3 ‰ to facilitate the discharge of condensed water. The particulate matter sampling manifold is equipped with a heat tracing strip to maintain a constant temperature of 50 ℃, preventing moisture from condensing and blocking the filter membrane.
Cable management: Power lines and signal lines are routed in separate slots with a spacing of>30cm. RS485 communication lines use twisted pair shielded cables, and the terminals are matched with 120 Ω resistors to suppress reflection interference.
Construction of Precision Calibration System
Zero drift correction: Clean air filtered by activated carbon is automatically introduced daily for baseline reset, with an allowable deviation of ≤± 0.5% F.S. per week.
Span calibration cycle: SO ₂/NOx is dynamically calibrated monthly using standard gas (concentration value of 80% of full scale), and O3 is verified quarterly using an ozone generator to generate a standard concentration field on site.
Multi point linear test: According to the requirements of HJ 655-2013, select 5 concentration gradients (including zero points) and draw calibration curves. The correlation coefficient R ² must be ≥ 0.999 before it can be put into use.
4、 Intelligent operation and maintenance management system
Remote monitoring system architecture
Deploy the edge computing gateway to achieve local pre-processing, and abnormal data trigger the three-level alarm mechanism:
L1 level (yellow): Single factor exceeding the standard for 1 hour → Automatic retesting of quality control samples
L2 level (orange): Multi factor synchronization exception → Start backup device for parallel monitoring
Level 3 (red): Data interruption exceeding 30 minutes → Dispatch work order to local operation and maintenance personnel
Blockchain technology is applied to the storage of raw data, and the hash value is synchronized to the regulatory platform to ensure immutability.
5、 Quality control strengthening measures
Inter laboratory comparison mechanism
Participate in the laboratory capability verification organized by the China Environmental Monitoring Station every year, and continue to operate only after obtaining a qualified certificate. Simultaneously carry out cross validation of portable detection instruments, with a relative error controlled within ± 15% considered as an effective comparison result.
Emergency response plan
Formulate special treatment plan for special weather: close the cover plate of the open sampling port and cut off power before rainstorm; Priority should be given to cleaning up dust accumulation in optical windows after sandstorms; During the typhoon season, retract the retractable mast components in advance. Establish a spare parts inventory, with no less than 2 sets of key sensors in stock.