*4.2. Effects of Meteorological Conditions and Environmental Management on Atmospheric Pollution*

Affecting the formation, diffusion, dilution, transformation, transportation, and accumulation of airborne pollutants, meteorological conditions are crucial for establishing air quality levels [11,12]. In this study, the meteorological factors significantly influenced the seasonal variations of particulate matter concentrations. This is partly because of the stable interaction between particulate matter and meteorological factors. Precipitation, for example, can remove particulate matter in the atmosphere and reducing the concentrations across seasons [27,28]. However, there are also some unstable interactions. Within a certain range, the wind can dilute the concentrations of particulate matter, otherwise the effect could be the opposite. In spring, for instance, strong winds from the northwest can easily bring sandstorms from Loess Plateau and increase the concentrations of particulate matter. The increased relative humidity caused by precipitation can reduce the concentrations of particulate matter, whereas high relative humidity can accumulate water-soluble ions, such as NH4 +, NO3 <sup>−</sup>, and SO4 <sup>2</sup>−, which are major aerosol components during haze episodes [29,30]. In addition, there may be a combination of other factors, such as vegetation cover, which can adsorb the particulate matter. Vegetation cover is regulated by phenology, such as atmospheric temperature [14]. This may result in the different relationships between particulate matter and atmospheric temperature across seasons.

The environmental management could determine the pollution intensity and the types of pollutants. In this study, we found that the environmental regulation intensity could significantly alleviate the emissions of SO2, smoke and dust, neither the particulate matter (Table 5). Compared with SO2, smoke and dust, the composition, chemical process, and the influence factors of particulate matter are more complicated [30,31]. It may be ineffective by simply increasing the environmental regulation intensity in a short period. Therefore, further exploration and verification are needed in terms of environmental management.

**Table 5.** Correlation coefficients between the environmental regulation intensity and the concentration and emission of atmospheric pollutants.


\*: *p* < 0.05.

Considering the difficulty of artificial control of meteorological conditions, more attention has been paid to the environmental management, which has been confirmed as the effective way to the improvement of atmospheric pollution. A one-size-fits-all management model may also have side effects on the development of socio-economics in a developing region. To reduce atmospheric pollution, effective environmental management should factor in the seasonal meteorological conditions. For instance, increasing relative humidity is an effective measure to reduce airborne pollution in spring and autumn. In winter, it is quite clear that improving ventilation and reducing relative humidity may ameliorate some of the effects of atmospheric pollution [25,32]. It is necessary to implement the intensity of targeted atmospheric governance under specific meteorological conditions to achieve the sustainability of socio-economic development and environmental protection.
