基于人体健康的3种城市森林夏季林内紫外线辐射环境特征比较研究

Comparing the summer ultraviolet radiation characteristics in the shade of 3 urban forests based on human health effects

以中波紫外线为主的紫外辐射对人体健康具有多种生物学影响,城市森林能够为居民提供温和的紫外辐射环境。为了解林下紫外线辐射环境特征是否存在树种间差异,对北京市3种常见遮荫树种的夏季林下紫外辐射(UV)强度、林内与林外UV辐射的比值(SR)、UV-B在总UV辐射中占比(UV-B/UV),以及VD合成和红斑效应两种人体作用有效辐射强度(UV_(VD)、UV_(er))进行了测算。结果表明:(1)三种林分林内紫外辐射总量是林外的3%-10%,不同林分的林内UV强度具有显著差异,元宝枫林对UV屏蔽能力最强,其次是栾树林和国槐林;(2)三种林分林冠对不同波长上紫外辐射能量的屏蔽能力具有明显的一致性,林冠对UV-B的屏蔽能力没有在UVA波段强和稳定,林内UV-B/UV普遍高于林外,其中元宝枫林最高,其次为栾树林,国槐林最低;(3)林冠明显改变了日光UV_(VD)和UV_(er)两种人体作用光谱曲线的形态,三种林分内的人体作用光谱曲线形态相似,强度上,林内外UV_(VD)/UV_(er)值均接近1,不同林分间没有显著差异;(4)胸径、无截取散射、平均叶倾角、叶面积指数和叶片透光性等树种特性或林冠结构特征会影响林内UV的强度,但不同林分内的紫外辐射光谱曲线变化趋势和波峰、波谷的位置基本一致,说明林内UV光质特征的树种间差异不明显。

Ultraviolet(UV),primarily ultraviolet B(UV-B)radiation,has multiple biological effects on human health,and urban forests can provide residents with a moderate UV radiation environment.In order to understand whether there are inter-species differences in UV radiation characteristics in canopy shade,diurnal spectral irradiance measurements in the open and below grove canopies of 3 native tree species in Beijing,Chinese scholartree(Sophora japonica,SJ),goldenrain tree(Koelreuteria paniculate,KP)and Shangtung maple(Acer truncatum,AT),had been taken in summer using a portable fiber spectrometer with a cosine corrector.The results showed that:(1)the ratios of UV radiation in shade to which in the open(Shade Ratio,SR)were 0.03-0.1.There were significant differences in UV irradiance between different grove shade at the same time period.AT grove had the lowest shade ratio with a range of 0.03 to 0.05 compared to the range of 0.03-0.09 for KP grove,and 0.07-0.1 for SJ grove;(2)significant consistency in shade ratios of the three groves were found at each wavelength.Shade ratios in UV-B band was not as low and stable as it was in the UV-A band,which indicated that the tree canopy had a stronger effect on UV-A radiation screening than UV-B.The proportion of UV-B radiation in total UV radiation(UV-B/UV)values in shade were generally higher than that in the open,with the highest in AT grove,followed by KP grove and the lowest in the SJ grove;(3)the canopy significantly changed the spectral waveform of both daylight vitamin D production spectrum weighted UV irradiances(UV_(VD))and erythema action spectrum weighted UV irradiance(UV_(er)),but the spectral curves in different grove shade were similar.In terms of intensity,the ratios of UVVD/UVer were 0.84-1.27.The mean value of the ratios were 0.99 for SJ grove,0.95 for KP grove,0.98 for AT grove and 1 for which in the open,with no significant differences between 3 groves;(4)the diameter at breast height(DBH),diffuse non-interception(DIFN),mean tilt angle of the leaves(MTA),leaf area index(LAI),leaf transmission,and other features of tree species or structural characteristics of the canopy,could affect the intensity of UV radiation in grove shade.But the UV radiation spectral waveforms and the positions of the peaks and valleys within different groves were generally consistent,indicating that there were no significant inter-species differences in UV light quality between groves.