秸秆覆盖对农田土壤风蚀及细颗粒物释放的影响

为了确定保护性耕作措施对北京周边农田土壤风蚀及颗粒物释放的影响,通过风洞模拟试验,对比不同风速和不同覆盖度下农田土壤风蚀速率及TSP、PM_(10)、PM_(2.5)、PM_1的释放差异,并分析了4种细颗粒物在风蚀物中的占比。结果表明:(1)当风速12 m/s时,秸秆覆盖度达到20%能显著降低风蚀速率,当风速16 m/s时,秸秆覆盖度需达到40%才能达到理想的防风蚀效果。(2)TSP、PM_(10)、PM_(2.5)、PM_1 4种细颗粒物的释放量与风速呈正指数函数关系,与覆盖度呈负指数函数关系;随风速的增加,4种细颗粒物的释放能力为AB1B2B3B4B5,当覆盖度10%或60%时,细颗粒物的释放量随风速增大差异逐渐减小;覆盖度达60%以上时,细颗粒物的释放量基本达到稳定值。(3)TSP、PM_(10)、PM_(2.5)、PM_1 4种细颗粒物在风蚀物中的占比随风速的增加而降低,当覆盖度60%时占比接近稳定。

Effects of Straw Mulch on Soil Wind Erosion and Fine Particulate Matter Release in Farmland

To study the influence of protective farming methods on wind erosion in farmland and particulate emission in the surrounding areas of Beijing city,the wind erosion rates of farmland and the emission situations of TSP,PM₁₀,PM_2.5,and PM₁ under different wind speeds and different degrees of coverage were compared by wind tunnel experiments,and the proportions of these 4 kinds of particulates in Aeolian deposits were analyzed. The results showed that: (1) When the wind speed is less than 12 m/s,a mere 20% of straw coverage would significantly lower the wind erosion rate,and when the wind speed is greater than 16 m/s,a coverage rate of at least 40% could resist wind erosion effectively. (2) The relationship between the emissions of TSP,PM₁₀,PM_2.5,PM₁,and wind speed was a positive exponential function,and that with the coverage was a negative exponential function. As wind speed increases,the releasing abilities of 4 fine particulate matters could be represented like this: A > B1 > B2 > B3 > B4 > B5. When the coverage rate was less than 10% or greater than 60%,the differences of bust sizes of fine particulates decreased as wind speed rose,and when the rate upped to more than 60%,the bust size tended to be stable. (3) The proportions of 4 fine particulates in Aeolian deposits decreased as the wind speeds increased,and the numbers became stable when the coverage rate was greater than 60%.