中国粮食硒含量的地理分布

本文应用多重正态分布理论,将粮食硒含量分成三级,编制中国粮食硒含量等级分布图,并且分析了我国粮食硒含量地域分异的主要原因。

GEOGRAPHICAL DISTRIBUTION OF SELENIUM CONTENT OF GRAINS IN CHINA

Selenium is an essential trace elenint to animal and man, but abnormal content (deficiency or excess) of selenium in environment is harmful. Selenium in environment has an influence on animal and man by means of biogeochemical food chain, rock-soil and water-plant-animal and man. Grain is the key link of them.This paper studies geographical distribution of selenium content of grains (wheat, corn and rice) in China and its relation to geographical epidemic of white muscle disease of animal and kashin disease and Kaschin-Beck's disease of man, which are endemics with relation to selenium deficiency in environment, by the method of statistical plotting.Statistics shows that frenquency distribution of selenium content of grains belongs to the approximate longnormal distribution. Therefore, according to' classifica-iton of equal ratio,different selenium content of grains is sorted out into three classes; high, medium and low, and a distribution map of selemium content degree of grains in China has been plotted. As shown in the map, grains containing high selenium mainly grow in the Northwestern part of China, next in Enshi county in Hu-bei province and Ziiyang county in Shaanxi province (There are areas in these two counties where selenium toxicosis occurs in livestock and man). Grains containing medium selenium are distributed in Southeast China, Northwest China and Northeast China plain, North China plain, Fenhe basin, Weibe plain and Sichuan basin. Grains containing low seleniumare distributed in the Lesser Hinggan Mountains, the Changbai Mountains, the Luzhong Mountains, the Loess plateau, the Qinling Mountains, the Daba Mountains, the eastern part of the Qinghai-Tibet plateau and the Qaidam Basin. It is outlined that low selenium zone is mostly distributed in mountainous and hilly regions in the so-called transition zone situated between the dry desert and steppe zone of the Northwest China and humid-hot evergreen forest zone of the Southeast China.Geographical distribution of the above-mentioned three endemics is fundamentally in accordance with that of grains containing low selenium. A difference of selenium mean content of grains between endemic areas and nonedemic areas is statistically very significant.