CAJ | 학술논문

干旱、半干旱地区湖泊沉积物能否有效地记录大气粉尘源区的风沙活动历史对理解沙尘暴发生的气候和环境背景具有重要的意义.对于位于内蒙古浑善达克沙地南缘的夏日淖(湖)近代沉积物进行137Cs/210Pb定年和沉积学分析显示,碎屑沉积物具有两个明显的粒度组分,其一是与当地沙丘砂粒度分布相同的中细砂组分;另一为与大气降尘粒度相似的粉砂组分,自1957年以来反映这两个粒度组分相对变化的中值粒径和>63μm砂的含量都具有显著的变化.与浑善达克地区和中国北方气象记录对比发现,沉积物中值粒径和>63μm砂的含量分别与沙尘暴和6m/s风速(或大风)发生频次呈正相关,与温度呈负相关;最近50年来这些沉积和气候参数具有总体一致的变化.这样的事实说明,夏日淖沉积物主要由风力搬运沉积的,其粒度与风沙活动存在内在联系,粗粒沉积物增加是风沙活动加强的结果.因此,干旱、半干旱地区湖泊中风力搬运的沉积物粒度受风沙活动强度控制,可以成为重建过去风沙活动历史的重要标志.
간한、반간한지구호박침적물능부유효지기록대기분진원구적풍사활동역사대리해사진폭발생적기후화배경배경구유중요적의의.대우위우내몽고혼선체극사지남연적하일뇨(호)근대침적물진행137Cs/210Pb정년화침적학분석현시,쇄설침적물구유량개명현적립도조분,기일시여당지사구사립도분포상동적중세사조분;령일위여대기강진립도상사적분사조분,자1957년이래반영저량개립도조분상대변화적중치립경화>63μm사적함량도구유현저적변화.여혼선체극지구화중국북방기상기록대비발현,침적물중치립경화>63μm사적함량분별여사진폭화6m/s풍속(혹대풍)발생빈차정정상관,여온도정부상관;최근50년래저사침적화기후삼수구유총체일치적변화.저양적사실설명,하일뇨침적물주요유풍력반운침적적,기립도여풍사활동존재내재련계,조립침적물증가시풍사활동가강적결과.인차,간한、반간한지구호박중풍력반운적침적물립도수풍사활동강도공제,가이성위중건과거풍사활동역사적중요표지.
Atmospheric dust produced in arid and semi-arid regions by wind activities plays an important role in global climate system.As northern part of China has been recognized as an important source area for global dust loading,the hydrological closed lake in these regions could be an ideal preservative place for the eolian sediments.The sediments in the Xiarinao Lake with out any rive recharge,located at the southern of the Hunshandake Desert could be wind blown since.The grain size measurements on modem sediment core XN06-1 from the lake showed that the sediment is composed of two major components of the sands and silts.The grain size distribution for the sands is same as that of the sand-dunes,and for the silts is similar to that of dust storms.The decay corrected 210pb conceatration in the core is as high as 18.7 ± 3.5 dpm/g which would be attributed to the contribution of the atmospheric dust instead of rivers loading sediments.So,these evidences support that the sediments in the Xiarinao Lake are mostly eolian sediment.The sediment core for the top of 25cm has been dated by 137Cs/210Pb ehrological method.The median grain size and the content of the > 63μm particles in the sediment core from Xiarinao Lake have been used to reconstruct the history of wind and dust activies in the Hunshadeke Desert for recent 5 decades.The median grain size and sand (> 63μm)content of the sediment core vary in ranges of 9～19μm(6.9～5.7φ)and 0.3%～30.4% respectively (Fig.4),showing a decreasing trend for the both of them from 1957～2005A.D.These changes parallel to changes in frequency of dust storm,wind speed,and temperature from meteorological stations around the Hunshandeke Desert and Northern China during the last about 50 years,indicating that the activities of dust storm and wind become negative with increasing air temperature,and also supporting that grain size of the eolian sediments in the lakes in dust source regions could be used as a proxy of intensity of dust and wind activities.