乌兰布和沙漠东北部大气降尘特征及影响因素分析

Analysis of the characteristics and affecting factors of atmospheric dustfall in northeastern Ulan Buh Desert

采用野外定位实测法,对乌兰布和沙漠东北部5种不同下垫面(绿洲防护林带、农田、固定沙丘、半固定沙丘、流动沙丘)的大气降尘进行了研究。结果表明:(1)研究区大气降尘具有明显的时空分异规律,不同月份的降尘量之间有着极显著差异(P<0.0001),4月份的降尘量达年内最大值,3-6月的降尘量之和占全年总量的46.3%;不同下垫面的年降尘量之间存在极显著差异(P<0.0001),从大到小为:流动沙丘>半固定沙丘>固定沙丘>林带>农田;不同高度的降尘量也存在极显著差异(P<0.0001),0.5m的降尘量大于1.5m的。(2)扬沙和沙尘暴发生的总天数与降尘量之间存在极显著线性相关关系(P<0.01),因此认为大风(≥6m/s)持续时间与扬沙和沙尘暴发生总天数是影响降尘的一个主要因子;降雨对降尘具有一定的抑制作用;下垫面状况是决定起尘强度的一个关键因子,其对降尘的影响主要是通过地表植被的防风固沙作用实现的。

Using field observation method, the atmosphere dustfall of different underlying surfaces （ oasis protec- tion forest belt, farmland, fixed dune, semi- fixed dune and mobile dune ） in northeastern Ulan Buh Desert were studied. The results showed that： （1） there were obvious temporal and spatial distribution laws in atmos- pheric dusffall. An highly significant difference about dusffall capacity existed among different months （P 〈 0. 0001 ） , dusffall capacity reached the peak in April; from March to June, the summation of dustfall capacity to- taled 46.3% of annual total quantity. There was an extremely significant difference about dusffall capacity among different underlying surfaces （P 〈 0.0001 ） ; the order from high to low was mobile dune, semi fixed sand dune, fixed sand dune, forest land and farmland; Besides, there was also a very significant difference between different sampling height （ P 〈 0. 0001 ） ; dustfall capacity in 0.5m height was larger than that in 1.5m height. （2） The total days of blowing sand and sandstorms had highly significant linear correlation （ P 〈 O. O1 ） with dustfall capac- ity, which suggested that the time of wind duration and the total days of blowing sand and sandstorms are impor- tant factors to the change of dustfall capacity; rainfall has some certain inhibition effect to dustfall; the condition of underlying surface is a key factor to decide dustfall intensity, and its influence is mainly accomplished by the wind prevention and sand fixation effect of land vegetation.