典型森林树种对大气颗粒物湿沉降的影响

Effect of Forest Tree Species on Wet Deposition of Atmospheric Particles

选择典型森林树种油松和侧柏作为研究对象,通过在2种树的冠层不同高度处（8,6,4,2m）布设湿沉降监测装置进行定位监测,比较单位叶面积滞尘量和降水对叶表面颗粒物冲刷率来分析2种树种对于大气颗粒物湿沉降的影响,并分析了树冠层不同高度颗粒物湿沉降以及不同粒径颗粒物湿沉降通量的变化规律,最后通过叶片显微结构来分析2种树种滞尘差异的原因。结果表明：（1）油松单位叶面积的滞尘量高于栓皮栎;降雨对2种树种叶面上大气颗粒物的冲刷率表现为栓皮栎高于油松。（2）油松枝下高2m处滞尘能力最强,大气颗粒物湿沉降通量最小;栓皮栎树冠中部4m处滞尘能力最强,且湿沉降通量最小。（3）油松冠层下部对于10-100μm污染物具有明显的截留作用,而栓皮栎的树冠上部对其具有更明显的截留作用。对于0.4-3μm和3-10μm颗粒物,油松的截留能力要强于栓皮栎。（4）油松和栓皮栎在叶表面显微结构的差异导致两者吸附颗粒物能力不同,油松叶片具有更多的褶皱、开度和密度较高的气孔以及相对较深的沟槽使其具有更强的吸附颗粒物的能力。

Typical forest tree species Platycladus orientalis and Quercus variabilis were chosen as the main research objects, and monitoring devices were set up at different canopy heights （8 m, 6 m, 4 m, and 2 m） of 2 different tree species for location monitoring. The wet deposition effect of tree species on atmospheric particulates was analyzed by the comparison of dust detention per unit leaf area and the sour rate of rainfall of 2 tree species. The wet deposition of particulates at different canopy height and the variation law of wet deposition flux of size-fractionated particulate matters were also analyzed, and the reason of the differences in dust-retention capacity of different tree species was explored by leaf microscopic structure analysis. The results showed that： （1） The dust detention per unit leaf area of Platycladus orientalis was higher than that of Quercus variabilis, while the sour proportion of rainfall of Quercus variabilis was higher than that of Platycladus orientalis. （2） The lowest wet deposition flux of particulates and the strongest retention capacity of Platycladus orientalis occurred at 2 m under branch height, while those of Quercus variabilis were observed at the height of 4 m in the middle of canopy. （3） The canopy bottom of Platycladus orientalis and the upper canopy of Quercus variabilis had the significant retaining effect on the range of 10 μm to 100 μm particulates. The retention capacity of Platycladus orientalis was better than that of Quercus variabilis for 0.4 to 3 μm and 3 to 10 μm particulates. （4） The difference in the leaf microscopic structure of the 2 different tree species caused different dust detention capacity. Platycladus orientalis has more wrinkles, stomata with higher opening and density, and relatively deeper grooves, which increased the particulate absorption capacity of this tree species.