Ultraviolet radiation is light radiation with a wavelength range of about 10~400nm.In this wavelength range, different wavelengths of ultraviolet radiation have different effects. In research and application, ultraviolet radiation is often divided into: Aband（400～320nm）；Band B (320 ～ 280nm);C-band (280 ～ 200nm);Vacuum ultraviolet band (200~10nm).Ultraviolet radiation with wavelength less than 200nm cannot propagate in the air due to absorption of the atmosphere.
On October 27, 2017,world health organizationThe list of carcinogens published by the International Agency for Research on Cancer is preliminarily collated and referenced. Ultraviolet radiation (wavelength 100-400 nm, including UVA, UVB and UVC) is included in the list of Class I carcinogens.[1]
The ultraviolet radiation of the sun is the main part of the ultraviolet radiation received by human beings, but due to the transmission of ultraviolet radiation in the atmosphereattenuationIn the process, the amount of ultraviolet radiation that really shines on the earth's surface only accounts for 4% of the total radiation.Therefore, in practical applications, artificial ultraviolet light source is particularly important.The artificial ultraviolet radiation source solves the shortage of natural light source (the sun) in time and space.
althoughozoneIt is an extremely trace component in the atmosphere, but it is the only material in the atmosphere that can absorb solar radiation with a wavelength shorter than 300nm, and its absorption coefficient increases with the decrease of wavelength.The ozone layer absorbs most of the ultraviolet B from the solar radiation, because the destruction of the ozone layer mainly causes the enhancement of the solar radiation in this band, especially the UVB radiation in the wavelength range of 290~315nm. In the wavelength range of 25nm, due to the absorption of ozone, its radiationstrengthWith the rate of 4 powerwavelengthDecrement.Therefore, the enhancement of ultraviolet radiation caused by ozone reduction is also highly wavelength dependent.
Generally used for ultraviolet radiation intensityUltraviolet indexIt is an indicator to measure the degree of possible damage to human skin (or eyes) caused by solar ultraviolet radiation reaching the ground around noon in a place. It mainly depends on latitude, season, stratospheric ozone, cloud conditions, altitude, ground albedo and atmospheric pollution conditions[2]The observation of ultraviolet radiation intensity mainly uses ultravioletSpectral radiometerFilter type ultraviolet radiometer, broadband spectrometer, etc.The most commonly used broadband instrument is Robertson Berger (RB)Ultraviolet radiometerIts temperature coefficient is about 0.01/K.The spectral response stability of the RB radiometer is more than ten years, of course, there are some differences between different instruments, so before the calibration of the RB radiometer network is re verified, the change trend obtained by using the RB radiometer data must be carefully checked.
Because of this, there are two existing sources of surface UV radiation data, the Ritual based ozone detection network and the satellite ozone detection system, which construct a radiation transfer model based on the ozone trend and the atmospheric scattering and absorption factors to calculate the UV radiation status. Although the irradiance calculated by the model may have errors,However, the theoretical relationship between ozone reduction and UV radiation increase under cloud free and low aerosol conditions has been determined by a lot of research work.Another is the direct measurement of RB radiometer network and single station multi filter instrument.
It is still difficult to determine the change of surface UV radiation, especially the long-term change trend, according to the measurement of UV radiation, because it requires high-precision and high stability data.The recent important progress is to evaluate the quality of data by optimizing instrument performance, comparing each other and reanalysing data.DifferentSpectral radiometerSeveral comparative experiments between them show that there are important differences among various instruments, mainly in the short wave region where the solar spectrum changes rapidly.Therefore, the problems of dynamic range, stray light suppression and wavelength calibration are very serious.In the wavelength range greater than 310 nm, the consistency will not be better than+5%, while in the shorter wavelength range, the consistency will be worse.To some extent, this is due to the uncertainty of calibration. This uncertainty comes from the fact that the spectral type of the solar spectrum changes with the solar zenith angle, column ozone amount and other atmospheric conditions.
Accurate measurement of solar ultraviolet spectral irradiance is very important for studying the effects of ozone, clouds and aerosols on solar ultraviolet radiation and their changes with time.The accurate measurement of solar short wave ultraviolet radiation can characterize the extent of ozone layer destruction, which is of great significance.The monitoring of solar ultraviolet radiation has been carried out worldwide.Over the past decade, a large number of stations have been established worldwide to monitor the spectral distribution of solar ultraviolet radiation reaching the surface.China Academy of MetrologyAnd the National Meteorological AdministrationBeijing Optical Instrument FactoryIn 2000, we began to research on solar ultraviolet spectral radiation measurement. We developed a solar ultraviolet spectral radiometer to measure solar radiation in UVB (280nm ～ 315nm) and UVA (315nm ～ 400nm) bands and the spectral irradiance of sky daylight reaching the ground within 2 π solid angle[3]。
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Impact on aquatic organisms
Aquatic biological systems provide a large amount of food for human beings. About 30% of all animal protein consumed by human beings in the world comes from the sea. In many countries, especially developing countries, this proportion will increase significantly.Therefore, it is very important to understand how the enhanced solar UVB radiation affects the output of aquatic ecological products.In addition, the ocean also plays a decisive role in the process of global warming. The plankton in the ocean is in the atmospherecarbon dioxideThe main sink of carbon dioxide plays a decisive role in the change trend of carbon dioxide concentration in the atmosphere.
Hader et al. studied the effect of solar UVB on the movement of a plant in the genus Chlamydomonas and a plant in the genus Protea. They found that UVB can weaken their swimming phenomenon and discrimination instinct, thus preventing Dongdong's plankton from constantly adapting to changing environmental conditions and possible dangerous situations.
Takeuchi and other researchers show that the enhanced solar UVB radiation will reduceMarine planktonThe productivity of complexMarine ecosystemAnd human beings. Any reduction in marine productivity will undoubtedly affect the global food supply.Worrest also pointed out that enhanced UVB radiation will affect the growth and rhythm of many microorganisms.Dohler and other researchers also found that UVB radiation strongly affected the nitrogen fixation process, thus affecting the reduction of the number of many important floating organisms;The decrease in the number of some important floating organisms will seriously affectAquatic ecosystemThe complex food chain and the total production of food.It is estimated that the loss of 16% of ozone content in the atmosphere will lead to a 5% reduction in plankton, which is equal to the annual fish yield of the world will be reduced by 700000 tons.
Enhanced UVB will lead to the decrease of seagrass abundance and redistribution in deep water.When the UVB intensity is higher than PAR level, the seagrass community may become short and poor, the population distribution is weakened, and the biomass is reduced. Therefore, the enhanced UVB has the potential to change the structure and distribution of seagrass population.
The increase of UVB radiation will causeMarine planktonShrimp, crab larvae and shellfish died in large numbers, even leading to the extinction of some species.UVB radiation can damage the early development stage of fish, shrimp, crabs, amphibians and other animals, and the most serious is to reduce their reproductive capacity and damage the growth and development of larvae.In late spring in high latitudes, the increase of UVB radiation may affect some species, because the increase of UVB radiation happens at the critical stage of their growth and development. Even a small increase or short-term fluctuation of UVB radiation will seriously affect the more sensitive species.
Murali et al. reported that the rate of UVB affecting phosphorus absorption by soybean is related to the amount of phosphorus used. When there is more phosphorus, UVB does not affect phosphorus absorption, and vice versa.Ambler et al found that in cotton without UVB supplementary irradiation, the speed of transferring Zn from cotyledons to young leaves was twice that of UVB treatment, which showed that UV could inhibit the movement of Zn in plants, and the mechanism was still unknown.Dai found that the electric conductivity of leaves of rice treated with UVB decreased, and this inhibition would affect the absorption capacity of rice roots, plant nutrition and rice biomass.
Doughty and Mope found that the cell membrane of charophyta polarized after ultraviolet radiation;The membrane resistance also decreases.Due to the damage of the membrane structure, the intracellular Cl -, K+, and Na+, and therefore a large amount of extravasation, while the active absorption of ions continues to decline.Wright et al. absorbed 86, Rb+, and 14C - and mannitol from the cultured tobacco cells and then irradiated them with UVB. The results showed that there were a large number of 86, Rb+, but no 14, C - and mannitol in the exosmosis. Therefore, UVB might destroy some specific ion channels on the plasma membrane, but it had little effect on the whole structure of the cells.This view has been confirmed by subsequent experiments.Zill and tolbert found that the activity of K-ATPase in root cells of wheat was inhibited after UVB treatment.In general, there are few studies on the absorption and operation of mineral ions by UVB.
Effect on skin canceration
Using the daily data of total solar radiation, cloud cover, solar zenith angle, ozone, water vapor pressure, air pollutants and ultraviolet radiation in Nanning, Guangxi, from September 2002 to October 2005, a model for calculating ultraviolet exposure based on meteorological factors was established;The daily UV exposure data from 1961 to 2007 were reconstructed using this model, and the characteristics of the reconstruction sequence were analyzed from different scales of year, spring, summer, autumn and winter;The data of skin cancer incidence from 1991 to 2003 were used to analyze the correlation between ultraviolet radiation exposure and the incidence of various skin cancers;The future changes of ultraviolet radiation are prospected.The main conclusions are as follows: from 1961 to 2007, the annual average daily value of UV exposure in Nanning was 95.83 W.h/m2;The absolute variability is the largest in summer, the relative variability is the largest in winter, and the absolute variability and relative variability are the smallest in autumn;The annual average and spring, summer and autumn ultraviolet radiation exposure has a weak downward trend, and the downward trend is obvious in winter;The mutation mainly occurred from the middle and late 1970s to the early 1980s and the early 1990s;The most significant cycle of the year and each season is quasi 7 years, and there is an obvious 11 year cycle in summer;From 1991 to 2003, the incidence of squamous cell carcinoma was significantly correlated with the ultraviolet radiation exposure;Basal cell carcinoma, squamous cell carcinoma and malignant melanoma all occurred at high ultraviolet radiation time;Looking forward to the changes of ultraviolet before 2050, it is believed that the years with high ultraviolet radiation may be near 2017, 2031 and 2045, and the years with low ultraviolet radiation may be near 2010, 2024 and 2038[4]。
