北京西山不同海拔油松林PM_(2.5)浓度及叶片吸附量变化规律

Variations in PM_(2.5) concentration and leaf adsorption capacity of Pinus tabulaeformis forests at different altitudes on Beijing Xishan Mountains

以北京西山不同海拔梯度油松人工林为研究对象,对油松林PM_(2.5)浓度变化和叶片PM_(2.5)吸附量进行分析,并应用电子显微镜对不同海拔油松叶表面微形态特征进行观察,阐释叶片吸附PM_(2.5)差异。结果表明:随着海拔升高PM_(2.5)质量浓度逐渐降低,不同海拔油松林PM_(2.5)质量浓度日变化均呈典型的双峰曲线,7:00和19:00是一天的两个峰值,最小值出现在13:00—15:00左右;从不同月份看,不同海拔油松林PM_(2.5)质量浓度最高值出现在冬季的2月,最低值在8月;不同海拔油松林PM_(2.5)质量浓度全年均值为84 m((102.28±18.44)μg/m^3)>110 m((94.18±18.34)μg/m^3)>160 m((81.53±19.23)μg/m^3)>230 m((75.39±15.71)μg/m^3);随着海拔升高单位叶面积PM_(2.5)吸附量逐渐减小,每升高50 m,单位叶面积PM_(2.5)吸附量降低23.25%,每公顷PM_(2.5)吸附量下降26.43%,不同海拔油松林每公顷PM_(2.5)吸附量全年均值为84 m((8.61±1.08)kg/hm^2)>110 m((7.30±0.94)kg/hm^2)>160 m((6.35±0.99)kg/hm^2)>230 m((4.34±1.14)kg/hm^2);处于低海拔的油松叶表面较粗糙,气孔内部和周围聚集大量颗粒物,在叶面形态上更有利于吸附PM_(2.5),高海拔则相反。高海拔空气质量优于低海拔,低海拔的植物吸附颗粒物多于高海拔。研究结果可为城市造林和森林净化大气提供数据支持。

PM2.5 concentration and leaf PM2.5 adsorption capacity of Pinus tabulaeformis artificial forests at different altitudes on Beijing Xishan Mountains were analyzed, surface micro-morphological characteristics of Pinus tabulaeformis at different altitudes were observed using electron microscopy, and differences in leaf PM2.5 adsorption were then interpreted. The results revealed the following： PM2.5 concentration decreased as the altitude increased; diurnal variations in PM2.5 concentration displayed a typical bimodal curve for the Pinus tabulaeformis forests at different altitudes; the highest peaks were observed at 7：00 and 19：00, while minimum concentrations were detected at 13：00-15：00; PM2.5 concentration was the highest in the winter month of February and the lowest in August; annual mean PM2.5 concentration at varying forest altitudes was 84 m （（102.28 18.44） μg/m3） 〉 110 m （（94.18 18.34） μg/m3） 〉 160 m （（81.53 19.23） μg/m3） 〉 230 m （（75.39 15.71） μg/m3）; PM2.5 adsorption amount per unit leaf area decreased as the altitude increased （PM2.5 adsorption amount per unit leaf area reduced by 23.25% as the altitude increased by 50 m）; PM2.5 adsorption amount per hectare decreased by 26.43%, with the Pinus tabulaeformis forests at different altitudes exhibiting annual mean values of 84 m （（8.61 1.08） kg/hm2） 〉 110 m （（7.30 0.94） kg/hm2） 〉 160 m （（6.35 0.99） kg/hm2） 〉 230 m （（4.34 1.14） kg/hm2）; leaf surface texture was rough at the lower altitudes, with a high number of particles inside and around the stomata （a function more conducive to PM2.5 adsorption with respect to leaf morphology）; and leaf surface texture at the high altitudes exhibited opposite features. Air quality at the high altitudes was superior to that at the low altitudes, and plant adsorption particles were higher at the low altitudes than at the high altitudes. The results can provide data support for urban afforestation and purification of the atmosphere using forests.