## 3 Results and Discussion
### Continuous Observation Experiment
#### 3.4.3 The Connection between Wind Fields and VOCs  
Atmospheric wind fields affect the transport and dispersion processes of pollutants through horizontal motion and vertical transport. A wind-dominated pollutant transport process was observed in the navigation monitoring of the IP site, and the variations in VOCs at different moments during this period are reflected in Figure 23. The six sub-plots given in Figure 23 were all collected in the vicinity of industrial plants in the industrial areas. VOCs are significant precursors of O\({}_{3}\) and secondary organic aerosols contributing to PM\({}_{2.5}\). Once VOCs are emitted into the ambient air, their levels in the atmosphere are determined by meteorological conditions and atmospheric chemical transformation conditions. The average diurnal variations in temperature, humidity, and wind level, from 0:00 on 4 August to 0:00 on 6 August 2021, are shown in Figure 24. The meteorological conditions fluctuated considerably during the two days of observation. The relationship between temperature and humidity follows an approximately opposite trend. At 6 am, temperatures remained low, and humidity remained high. As the temperature increased, the relative humidity gradually decreased. At around 16:00 p.m., the temperature reached a maximum of 34 \({}^{\circ}\)C, while the relative humidity dropped to a minimum of 62%. Wind speed was generally low, with the wind level remaining below level 3. However, the wind direction fluctuated widely with several instances of wind shear. The weather conditions were dominated by high temperatures and low humidity, and light wind prevailed during the observation period. The variation in VOCs and O\({}_{3}\) concentrations under different wind speed conditions is shown in Figure 25. Wind is essential for the transport and dispersion of atmospheric pollutants. Under low wind speeds, the changes in the concentration of VOCs and O\({}_{3}\) were positively correlated to wind speed to a certain extent. As wind speed increased, the concentrations of VOCs and O\({}_{3}\) also partially increased. This was mainly because increased airflow promotes the volatilization of VOCs and facilitates the dispersion of VOCs and O\({}_{3}\) into the air, increasing local pollutant concentration. Under high wind speeds, the concentrations of VOCs and O\({}_{3}\) were negatively correlated with wind speed to a certain extent. Although windy weather allows for a rapid dilution and removal of pollutants, higher wind speeds can also lead to the long-range transport of particulate matter and the accumulation of high concentrations in the downwind direction, thus diluting the local pollutant concentration and decreasing VOC and O\({}_{3}\) concentrations. Figure 22: Percentages of individual VOCs. In addition, a good correspondence between O\({}_{3}\) and VOCs can also be seen in Figure 25. O\({}_{3}\) concentration was single-peak, reaching its maximum value in the afternoon, while the VOC concentration underwent a bimodal change, reaching its maximum values in the morning and evening rush hours. The single peak of O\({}_{3}\) occurred at the trough of VOC concentrations. Before sunrise, light intensity was weak, with good overall air quality and no significant pollution.