Variation of particle matters in three forests under different habitats in summer

Urban forests can reduce atmospheric particle matters and hence improve the quality of ambient air. To provide a theoretical basis for creating a health-leisure urban forest, in this paper, the mass concentrations of TSP, PM₁₀, PM_2.5, and PM₁ in three typical urban forest habitats as foothill(SL), river valley(HG) and ridge(SJ) in the Yuanshan Park of Shenzhen, southern China were observed during the whole day in the summer of 2015 with a cloudy weather. In the same time, the meteorological factors were also observed to understand the dynamic pattern of particle matter mass concentrations in different types of urban forests, as well as influencing factors.The results showed that:1)The daily mean mass concentrations of TSP or PM₁₀ in the 3 forests were all reached the grade-Ⅱ national standard for urbanized area ambient air quality, and the concentrations of TSP in HG forest and SJ even reached the standard grade-Ⅰ(120μg/m³).Meanwhile, the daily mean mass concentrations of PM_2.5 in each forest all achieved the national standard grade-Ⅰ for urbanized area ambient air quality(35μg/m³).2)The mass concentrations of different size particle matters varied in different forests.The four kinds of particles were all lowest in SJ forest(85.51, 58.82, 14.29, 5.13μg/m³, respectively).The TSP or PM₁₀ was highest in SL forest(162.19, 95.39μg/m³, respectively), and the PM_2.5 or PM₁ was highest in HG forest(21.76, 8.29μg/m³, respectively).3)During the observation period, the concentrations of four kinds of particle matters in three forests were higher in the nighttime, and lower in the daytime, with the peaks usually appeared at 01:00—07:00, and the vales at 11:00—15:00.4)There were some differences in relative humidity, wind velocity, barometric pressure and other meteorological factors among 3 forests.The concentrations of four kinds of particles were significantly negative correlated with temperature and wind velocity, and were obviously positive correlated with relative humidity.In addition, changes in the concentration of particle matters were influenced by a variety of meteorological factors working together.Therefore, we concluded that the urban forests in the Yuanshan Park of Shenzhen can provide a relatively healthy forest recreation environment for the residents in the urban area.The healthy time according to the status of 4 kinds of particles is 11:00—15:00 in summer.