太阳紫外线辐射及其生物效应

紫外（UV）辐射在太阳幅射光谱中的谱区范围是在100－400nm间，其能量仅占太阳辐射总量的8％，按照不同波长线所起的生物作用，可分为三部分，紫外线A段（UV－A），波长320－400nm，约占太阳辐射总量的6％，这部分生物作用较弱，主要是色素沉着作用，紫外线B段（UV-B），波长290－320nm，约占太阳辐射总量的1．5％，此段对人体影响较大，主要作用是抗佝偻病和红斑作用，是引起民皮肤癌，白内障，免疫系统能力下降的主要原因之一，紫外线C段（UV－C），波长100－290nm，约占太阳辐射总量的0．5％，由于几乎完全被臭氧层吸收而不能达到地面，以人工发生的紫外线灯进行实验，这段紫外线具有最大杀菌力，对机体细胞也有强烈的刺激破坏作用。

Surface Sunny Ultraviolet Radiation and Biology Effect

Ultraviolet radiation can be divided into three parts of the sun's radiation spe ctrum. The wavelengths of UV-A radiation range is from 320 to 400 nm. Ozone abs orbs very little of this part of the UV spectrum. Ultraviolet-A radiation is ne eded by humans for the synthesis of vitamin D.However,UV-A causes photoaging (t oughening of the skin),degradation of the immune system, and to a lesser degree, reddening of the skin and cataract formation. Ultraviolet B ranges in wavelengt h from 290 to 320 nm. Ozone absorbs much of the shorter wavelength radiation, bu t this absorption weakens as 320 nm is approached. Plants and animals are partic ularly affected by this part of the UV spectrum. Ultraviolet-B can redden the s kin (erythema) and reduce vitamin-D synthesis in a short term and may cause ski n cancer, cataracts, and may degrade the immune system in the long term. Ultraviol et C is characterized by wavelengths of less than 290 nm. Although highly danger ous to plants and animals, this part of the UV spectrum is completely absorbed b y stratospheric ozone and does not reach the earth′s surface.