北京风沙若干问题的讨论

本文在实地调查研究的基础上提出对北京风沙一些问题的看法:1)北京风沙物质来源为本地超沙,尘的来源复杂,以外来成分最多;2)分析35午风沙资料得出这些年北京平原风沙趋于成少。

STUDY ON SOME BASIC PROBLEMS OF WIND-DRIFT SAND IN BEIJING

In recent years, argument about wind-drift sand of Beijing has continued arising This paper presented some understandings for wind-drift sand problems of Beijing based on the field investigaton. 1) In accordance with geoche-micaJ analysis of heavy minerals and microelements in the sand caused by various reasons, and comparison with near by deserts and sandy lands, it is confirmed that wind-drift sand materials in Beijing are river sediments of the local region, which are blown off and then accumulated, and dust storm and particles come mainly from the areas where prevailing wind occurs and passes through. 2) According to the data observed in meteorological stations in various counties of Beijing for a long time, wind-drift sand of Beijing is divided into five types, i.e. blowing sand; blowing sand-suspended dust,suspended dust by strong wind; suspended dust and sand storm. Regional distributive law of different wind-drift sand is presented too in this paper. Meanwhile it points out that differances of geomorphic position and surface sediment type of stations are the basic causes of the formation of different sand types 3 ) Several fluctuations of sand drifting days occur with increasing or reducing of strong wind days and the changes in phenomenon of sand storm, suspended dust and biowing sand also take place, but the general trend of sand drifting days are gradually reducing. Taking the data of Beijing city as an example, the average annual sand drifting days reduce from 78 days in the early 1950s to 19.3 days in the eariy 1980s. It indicates that increasing green areas and establishing and perfecting anti-wind system in Beijing in planned way are the primary measures to cotrol wind-drift sand