乌珠穆沁沙地生物基可降解聚乳酸(PLA)沙障防风固沙效益

Effects of Biodegradable Poly Lactic Acid (PLA) Sand Barrier on Wind Prevention and Sand Fixation in Urumqi Sandy Land

为了探究PLA沙障对乌珠穆沁沙地沙化治理的效果,以方格状铺设不同规格(方格边长0.5 m×0.5 m, 1 m×1 m, 2 m×2 m和3 m×3 m)PLA沙障,以不同规格沙障影响的风蚀特征为研究对象,裸沙地设置对照(CK),采用美国HOBO便携式风速采集仪观测距地表10,20,50,100,200 cm高度的风速,同时使用自动旋转集沙仪收集近地表0—30 cm高度输沙量,分析了防风效能、固沙效益和风沙流挟沙粒径的变化特征。结果表明:(1) PLA沙障规格小于3 m×3 m时,风速廓线呈“S”型变化趋势;PLA沙障平均的地表粗糙度为0.64 cm, CK的平均粗糙度为0.51 cm,粗糙度提高了25.48%。(2)铺设PLA沙障后输沙量降低了38.72%~75.69%;PLA沙障输沙率随高度呈现良好的指数关系(R2>0.77);1 m×1 m和2 m×2 m沙障的固沙效益高于其他2种规格沙障,3 m×3 m规格的固沙效益最低,基本接近CK。(3)乌珠穆沁沙地风蚀物颗粒大小介于2~500μm,且大部分颗粒为100~250μm的细沙;铺设PLA沙障后,障格内细沙含量增加了8.70%~11.94%,中沙含量减少了10.63%~14.06%(p<0.05)。综上所述,铺设PLA沙障能有效降低乌珠穆沁沙地近地表风速,增加地表粗糙度并且能够降低近地表的输沙量,改变0—30 cm高度的风沙流结构,具有较好的治理效果。

In order to explore the effect of PLA sand barrier on desertification control in Urumqi sandy land, PLA sand barriers of different sizes(square length: 0.5 m×0.5 m, 1 m×1 m, 2 m×2 m and 3 m×3 m) were laid in grid shape. The wind erosion characteristics of sand barriers with different specifications were studied. The bare sandy land was set as the control(CK), and HOBO portable wind speed acquisition instrument was used to observe the wind speed at heights of 10 cm, 20 cm, 50 cm, 100 cm and 200 cm above the surface. At the same time, the automatic rotary sand collector was used to collect the sediment transport at 0—30 cm height near the surface, and the variation characteristics of windbreak efficiency, sand fixation efficiency and sand carrying diameter of wind-blown sand flow were analyzed. The results show that:(1) when the PLA sand barrier size is less than 3 m×3 m, the wind speed profile presents an S-shaped change trend;the average surface roughness of PLA sand barrier is 0.64 cm, and that of CK is 0.51 cm, which is 25.48% higher than that of PLA sand barrier;(2) sediment transport decreases by 38.72%~75.69% after PLA sand barrier was laid;the sediment transport rate of PLA barrier shows a good exponential relationship with height(R~2>0.77);the overall surface roughness decreased in the order: 1 m×1 m>0.5 m×0.5 m>2 m×2 m>3 m×3 m>CK;the sand fixation benefits of 1 m×1 m and 2 m×2 m sand barriers are higher than these of the other two types of sand barriers, and the sand fixation benefit of 3 m×3 m sand barriers is the lowest, basically close to CK;(3) the size of wind erosion particles in Urumqi sandy land is between 2~500 μm, and most of the particles are fine sand between 100~250 μm;After PLA sand barrier was laid, the fine sand content in the barrier increases by 8.70%~11.94%, the contents of medium sand decreases by 10.63%~14.06%(p<0.05). In conclusion, laying PLA sand barriers can effectively reduce near-surface wind speed in Urumqi sandy land, increase surface roughness. reduce near-surface sediment transport, and change the aeolian sand flow structure of 0—30 cm height, which has better control effect.