库姆塔格沙漠北部三垄沙地区风沙运动特征

Aeolian Sediment Transport in the Sanlongsha Area to the North of Kumtagh Desert

风沙地貌发育受控于近地表风沙运动,目前这一领域的研究较多关注短时期内(几分钟至几小时)、单一方向(正对主风向)的风沙流结构特征,结果难以与长期的地貌过程联系起来。为此,我们采用八方位四层梯度集沙仪,于2014年5月至2015年5月,在库姆塔格沙漠北部三垄沙地区进行了一个完整年度的风沙运动观测。经过6个时段的连续观测,获取了不同方向、不同高度的192个运动沙粒样品。结果表明:(1)近地表1m高度内,收集的样品总质量为405.2kg,其中约75.3%集中在近地表0~0.2m,反映了近地表输沙特征。(2)平均输沙率为55.2kg·m^(-1)·d^(-1),风沙运动的风向以北风、东北风和西北风为主;不同季节差异明显,春季输沙率最大,是年均输沙率的2.5倍,夏季次之,冬季最小。(3)年度平均输沙通量廓线(风沙流结构)呈指数函数递减趋势,部分通量廓线出现了戈壁风沙流的"象鼻效应"。(4)平均净输沙率1.159kg·m^(-1)·d^(-1),随高度增加呈递减趋势,合成输沙方向为193.2°;不同时段净输沙率随高度的变化基本与全年一致,合成输沙方向随高度增加有从东北向北偏的趋势。综上所述,该区域输沙强度以春季最为强烈,输沙方向以N、NE和NW方向为主,且春、夏两季节分别有一个次输沙方向,为S方向。本研究对于深入理解三垄沙地区风沙运动特征和揭示库姆塔格沙漠沙物质来源有重要意义。

The development of aeolian geomorphology is controlled by near surface sand movement, whereas the current research pays more attention to the short period （a few minutes to a few hours） and single direc- tion （facing the main direction） of the blowing sand structure characteristics, and it is difficult to relate the results to the long-term geomorphological processes. Thus, we conducted a whole year field observation of aeolian sediment transport from May 2014 to May 2015 in the Sanlongsha Area of the Northern Kumtagh Desert, adopting the eight-directional four layer gradient sand trap （SEDST）. After continuous observation of six periods, totally obtained 192 sand samples from different directions and different heights. Observation results show that the total weight of the captured sediments is 405.2 kg within 1 m above the ground and 75.3 % of them are transported within 0--0. 2 m, reflecting the characteristics of near surface sediment transport. The average sediment transport rate is 55.2 kg- m-1 ~ d-1, with sediments mainly from the N, NE and NW directions, and there is significant diversity in different seasons, and the maximum transport rate in spring is 2.5 times of the annual average value, followed by summer and winter minimum. The annual aver- age sediment flux profile （blowing sand structure） shows exponential decline trend, part of the flux profile has presented the ＂trunk effect＂ over the gobi surface. The annual mean net flux is 1. 159 kg. m-1.d-1, a- long with the increase of the height decreased, and the variation of net flux with altitude at different time periods is consistent with that of the whole year; the annual mean resultant sediment transport direction is 193.2, and the direction of sediment transport increases with the increase of the height from the northeast to the north. In conclusion, the sediment transport intensity reaches the strongest in the spring, and the main sediment transport direction is N, NE and NW, with a secondary sediment transport direction, S direction, in spring and summer, respectively. The study has great significance for the further understanding ae- olian sediment transport of Sanlongsha area and revealing the material sources of Kumtagh desert.