Theoretical Study of Functions of Tree Shade to Reduce Human Dosage of Lethal Ultraviolet Ray for Urban Design

人们认为，太阳的光化紫外线会因臭氧和氧气的吸收而突然终止。关于平流层臭氧消耗的第一份报告发表于1985年[Farman et al., 1985]。在日本，最近的观测显示，由于人类引起的平流层臭氧减少，紫外线b辐射（280-320 nm）增加[日本气象厅，1998年；Sasaki et al., 1998]。对UV-B增加的大部分关注是由于预测这将产生重大的生物影响，包括对人类健康的有害影响。如果假定给定的紫外线的性质，人体所受紫外线的剂量将因地被覆盖材料的反射率和透射率而增加或减少。这些材料的光谱特性需要数据基础。这里的主要目的是描述植物叶片在紫外线区域的光谱特性，并提出可能的好处。在紫外波段（UV-A、UV-B、UV-C）中，绿叶的反射率很低（约5%），透过率为零。一片绿叶植物吸收了整整95%的入射紫外线。从早春初叶，到夏季的深绿色，再到秋季的颜色和冬季的落叶，紫外光区的特征没有变化，而可见光和近红外区的特征变化显著。结果表明，从理论上讲，植物的叶子是有害紫外线的另一个终结者，保护植物本身和动物，包括人类。在生物多样性方面，应该考虑在我们的生活或工作空间内种植植物的有机设计，以减少紫外线。这些城市设计将服务于冷却城市热岛、创造美丽景观和减少二氧化碳等温室气体的综合功能。少

It has been considered that the actinic ultraviolet rays of the sun are abruptly terminated by ozone and oxygen absorption. The first report of stratospheric ozone depletion was published in l985 [Farman et al., 1985]. In Japan, recent observations showed an increase of ultraviolet-B (UV-B) radiation(280-320 nm) resulting from human-induced decreases in stratospheric ozone [Japan Meteorological Agency, 1998 ; Sasaki et al., 1998]. Most of the concern over the increase of UV-B has arisen due to the prediction that this would have significant biological impact, including harmful effects on human health. If given qualities of ultraviolet assumed, the human dosage of ultraviolet would be multiplied or reduced by the reflectance and transmittance of ground cover materials. The basis of data is needed concerning spectral properties of these materials. The primary purpose here is to describe spectral properties of a plant leaf in the ultraviolet region, and suggest the possible benefits. The … More ultraviolet region of solar radiation is conveniently divided into segments A(320-400nm), B(280-320nm), and C(wavelengths shorter than 280nm), In the ultraviolet region (UV-A, UV-B, UV-C), reflectance of a green leaf was very low (around 5%), and transmittance was absolutely zero. A green leaf of plant absorbed a full 95% of the incident ultraviolet. The features in the ultraviolet region did not change from the inception of foliage in early spring, through the intense deep green of summer, to autumn coloration and falling leaves in winter, whereas they showed significant change in the visible and near-infrared regions. The results indicate, theoretically, that plant leaves are working as another terminator of harmful ultraviolet ray, protecting plants themselves and animals, including humans. Regarding biological diversity, organic design with plants within our living or working spaces should be considered in reducing ultraviolet ray. These urban designs would serve the integrated functions of cooling the urban heat island, creating beautiful landscapes, and reducing greenhouse gases like carbon dioxide (C02). Less