摘要
城市森林内PM2.5浓度的状况可以直接反映城市森林对PM2.5的净化效果,也是居民休闲游憩关心的森林环境问题。选择北京西山3种典型的游憩型城市森林,通过对林内PM2.5浓度一年四季昼夜24h内变化的同步观测,分析了不同类型城市森林内PM2.5浓度的季节变化、日变化以及影响因素,结果表明:(1)北京西山3种游憩林内PM2.5浓度多数时候远低于城区对照值,在春、夏、秋三季都达到了国家城市化地区的标准,甚至在春季、秋季还达到了国家一类地区的标准。(2)城市森林在不同季节对PM2.5的净化效果存在差异,林内PM2.5浓度总体上呈现冬季>夏季>秋季>春季的规律。(3)林内PM2.5浓度在一天24h内有很大变化波动,夜间浓度总体上高于白天,日变化曲线近似呈"双峰双谷"型,两个高峰出现在夜晚和早上,两个低谷出现在凌晨和中午前后。一年四季白天低谷出现时间有所不同,春季15:00左右、夏季13:00—17:00、秋季13:00—15:00、冬季9:00—11:00。(4)PM2.5在不同类型游憩林内的变化趋势和浓度值存在一定差异。郁闭度较大的侧柏林夜间PM2.5浓度总体上高于其它两种林型,其高峰和低谷出现时间延迟,高峰值大,高峰期持续时间长,且这种规律在秋季表现得更明显。(5)基于上述研究认为,北京西山城市森林为居民在PM2.5污染比较突出的都市背景下提供了一个相对清洁、健康的森林游憩环境,春季、夏季、秋季全天以及冬季9:00—11:00均是森林中PM2.5状况健康而适宜外出游憩的时段。
The status of PM2.5 concentration in the urban forest can directly reflect the function of urban forest reducing PM2.5 pollution, and it is also the important environmental issue that residents concern about during recreating in forest. PM2.5 concentrations in three recreation urban forests were simultaneously measured in typical days over the four seasons in the West Mountain of Beijing, China. We analyzed the seasonal and diurnal vacation of PM2.5 concentrations in three different recreation urban forests and their influencing factors in this study. The results were as follows： （1） PM2.5 concentrations in three recreation forests in the West Mountain were much lower than that in the urban background of Beijing in most of the time over the year. PM2.5 concentrations in three recreation forests achieved the national standard for urban areas in spring, summer and autumn. Furthermore, the concentration was even as low as the national, standard set for the first class region in spring and autumn. （2） PM2.5 concentrations changed in the order of winter 〉summer〉autumn〉spring, indicating that the purifying effect of urban forests on PM2.5 varied in different seasons. （3） PM2.5 concentrations in forest changed greatly in 24 hours a day. In general the concentrations during night time were higher than that of the day time, and diurnal variation curves showed nearly ＂two peaks and two vales＂, with two peaks appearing at night and in the morning, and two troughs in the early morning and around noon. Throughout the year, vales appeared in the day time at around 15：00 in spring, 13 ： 00-- 17 ： 00 in summer, 13 ： 00-- 15 ： 00 in autumn, 9 ： 00-- 11 ： 00 in winter. （4） The trend and the values of PM2.5 concentrations were different from each other in three kinds of urban forests. In Platycladus orientalis forest with higher canopy density, the peak time and vale time of PM2.5 concentrations at night occurred later, PM2.5 concentration was higher at peaks time, and the duration of the peak was longer than that in other two forests. Therefore, PMzs concentration at night in Platycladus orientalis forest was higher than that in Cotinus coggygria forest and the mixed forest, especially in autumn. We, therefore, concluded that the urban forests in the West Mountain of Beijing can provide a relatively healthy forest recreation environment for the residents in the urban area. Spring, autumn and summer are the comparatively fine seasons for Beijing residents to recreate in the West Mountain, and the healthy time according to the status of PMzs concentration are the whole day in spring, 9：00--17：00 in summer, the whole day in autumn and 9：00--11：00 in winter.
出处
《生态学报》
CAS
CSCD
北大核心
2014年第19期5650-5658,共9页
Acta Ecologica Sinica
基金
林业公益性行业科研专项经费课题(201304301-05)
国家"十二五"科技支撑计划重大项目课题(2011BAD38B03)
关键词
北京西山
城市森林
PM2.5
日变化
季节变化
森林游憩环境
West Mountain of Beijing
urban forest
PM2.5
diumal variation
seasonal variation
recreation environment of forest
