Polysiloxane/SiO2 hybrid coatings have been prepared on Kapton films by a sol-gel process. The erosion resistance of polysiloxane/Si02 （20 wt pct） coating was evaluated by exposure tests of vacuum ultraviolet radiat...Polysiloxane/SiO2 hybrid coatings have been prepared on Kapton films by a sol-gel process. The erosion resistance of polysiloxane/Si02 （20 wt pct） coating was evaluated by exposure tests of vacuum ultraviolet radiation （VUV） and atomic oxygen beam （AO） in a ground-based simulation facility. The experimental results indicate that this coating exhibits better AO resistance than pure polysiloxane coating. The erosion yield （Ey） of the polysiloxane/Si02 （20 wt pct） hybrid coating is about 10-27 cm3/atom, being one or two orders of magnitude lower than that of polysiloxane. VUV radiation can affect the erosion process greatly. Under simultaneous AO and VUV exposure, the value of Ey of the polysiloxane/5iO2 （20 wt pct） hybrid coating increases by 3g% compared with that under single AO exposure.展开更多
喀斯特地区特殊的地表、地下侵蚀产沙是引发石漠化发生发展的重要物理过程。以喀斯特山地石漠化过程中不同石漠化状况的裸坡面为研究对象,通过模拟其地表微地貌及地下孔(裂)隙构造特征,采用人工模拟降雨试验研究其地表及地下侵蚀产沙特...喀斯特地区特殊的地表、地下侵蚀产沙是引发石漠化发生发展的重要物理过程。以喀斯特山地石漠化过程中不同石漠化状况的裸坡面为研究对象,通过模拟其地表微地貌及地下孔(裂)隙构造特征,采用人工模拟降雨试验研究其地表及地下侵蚀产沙特征。结果表明:无石漠化、潜在石漠化和轻度石漠化的裸坡在相同条件下的地表产沙量总体上高于地下产沙量,且10 min降雨时段内地下产沙量在0~100 g之间。不同石漠化强度的裸坡地表、地下侵蚀产沙量均随雨强的增大而增加;小雨强(30~80 mm h^(-1))下,随着石漠化强度加剧其地表越不易发生侵蚀,而石漠化强度达到一定程度时(基岩裸露率40%)土壤流失以地下流失为主;大雨强(150 mm h^(-1))下,地表产沙量及其分配比例随基岩裸露率变化不明显,而地下产沙量则呈先增加后减小的变化且在基岩裸露率为30%时达到最大。不同石漠化强度的裸坡地表产沙量及其分配比例随地下孔(裂)隙度变化不明显,地下产沙量及其分配比例总体上随地下孔(裂)隙度增加而增加;在不同地下孔(裂)隙度下(1%~5%),地表、地下产沙量及其分配比例随基岩裸露率变化(10%~50%)差异较大。研究结果对认识喀斯特地区石漠化发生发展机制、揭示土壤侵蚀特征、防治地表地下水土流失具有重要的理论和现实意义。展开更多
The Pisha sandstone-coverd area is among the regions that suffer from the most severe water loss and soil erosion in China and is the main source of coarse sand for the Yellow River. This study demonstrated a new eros...The Pisha sandstone-coverd area is among the regions that suffer from the most severe water loss and soil erosion in China and is the main source of coarse sand for the Yellow River. This study demonstrated a new erosion control method using W-OH solution, a type of hydrophilic polyurethane, to prevent the Pisha sandstone from water erosion. We evaluated the comprehensive effects of W-OH on water erosion resistance and vegetation-growth promotion through simulated scouring tests and field demonstrations on the Ordos Plateau of China. The results of simulated scouring tests show that the water erosion resistance of W-OH treated area was excellent and the cumulative sediment yield reduction reached more than 99%. In the field demonstrations, the vegetation coverage reached approximately 95% in the consolidation-green area, and there was almost no shallow trenches on the entire slope in the treated area. In comparison, the control area experienced severe erosion with deep erosion gullies appeared on the slope and the vegetation coverage was less than 30%. This study illustrated that W-OH treatment can protect the Pisha sandstone from erosion and provide the vegetation seeds a chance to grow. Once the vegetation matured, the effects of consolidation-growth mutual promotion can efficiently and effectively improve the water erosion resistance and ecological restoration.展开更多
Present study shows suspended sediment dynamics in the meltwater of Chhota Shigri glacier,Himachal Pradesh,India for different melt seasons during the period 2011-2014.Maximum suspended sediment concentration in the m...Present study shows suspended sediment dynamics in the meltwater of Chhota Shigri glacier,Himachal Pradesh,India for different melt seasons during the period 2011-2014.Maximum suspended sediment concentration in the meltwater was found during the month of July 2011,2012 and 2014 constituting to 55.2%,48.3% and 46.9%,respectively.Whereas in 2013,maximum suspended sediment concentration was observed in August accounting for46.1% of the total.On the other hand,maximum suspended sediment load was monitored in the month of July 2011,2012 and 2014 constituting 59.5%,63% and 55.7% of the total,respectively.Whereas in2013,maximum suspended sediment load was observed in the month of August accounting for 49.8% of the total suspended sediment load.Annual distribution of suspended sediment concentration(SSC)and suspended sediment load(SSL)in the Chhota Shigri glacier shows higher value of SSC and SSL during the study period 2012 and 2013,which may be due to the presence of high glacial runoff and negative mass balance of the studied area during these time periods.Marked diurnal variation has been observed in the SSC of meltwater.Strong correlation was observed between SSC and SSL with discharge.On the other hand,SSC and SSL also showed strong exponential correlation with air temperature of the studied area.Sediment yield from the catchment of Chhota Shigri glacier is high during the peak melt season(July and August)and low during the late melt season(September and October).The average value of erosion rate for Chhota Shigri glacier basin during the study period 2011-2014 was calculated to be 1.1mm/yr,which is lower than the average erosion rate of other Himalayan glaciers such as Rakiot,Chorabari and Gangotri glaciers,which may be caused by its geological setting containing high erosion resistant rocks such as granite,granite gneiss and porphyritic granite.展开更多
Identifying land management practices(LMPs)that enhance on-site sediment management and crop productivity is crucial for the prevention,reduction,and restoration of land degradation and contributing to achieving land ...Identifying land management practices(LMPs)that enhance on-site sediment management and crop productivity is crucial for the prevention,reduction,and restoration of land degradation and contributing to achieving land degradation neutrality(LDN).We reviewed studies in Ethiopia to assess the effects of LMPs on soil loss(84 studies)and crop productivity(34 studies)relative to control practice.Yield variability on conserved lands was assessed using 12,796 fixed plot data.Effects of LMP on soil loss were 0.5-55 t ha^(−1)y^(−1)compared to control practices yielding 50 to 140 t ha^(−1)y^(−1).More than 55%of soil loss records revealed soil loss less than the tolerable rate(10 t ha^(−1)).Area closure,perennial vegetation cover,agronomic practices,mechanical erosion control practices,annual cropland cover,and drainage groups of practices led to 74.0±18.3%,69.0±24.6%,66.2±30.5%,66.1±18.0%,63.5±20.0%,and 40±11,1%soil loss reduction,respectively.A yield increase of 25.2±15.0%,37.5±28.0%,and 75.4±85.0%was found from drainage,agronomy,and mechanical erosion control practices,respectively.The average yield loss by erosion on fields without appropriate land management practice and on conserved fields was 26.5±26.0%and 25±3.7%,respectively.The findings suggest that practices that entail a continuous presence of soil cover during the rainy season,perennial vegetation,retention of moisture,and barriers for sediment transport were most effective at decreasing soil loss and increasing productivity.This review provides evidence to identify the best LMP practices for wider adoption and inform decision-making on LMP investments towards achieving sustainable solutions to reverse land degradation.展开更多
文摘Polysiloxane/SiO2 hybrid coatings have been prepared on Kapton films by a sol-gel process. The erosion resistance of polysiloxane/Si02 （20 wt pct） coating was evaluated by exposure tests of vacuum ultraviolet radiation （VUV） and atomic oxygen beam （AO） in a ground-based simulation facility. The experimental results indicate that this coating exhibits better AO resistance than pure polysiloxane coating. The erosion yield （Ey） of the polysiloxane/Si02 （20 wt pct） hybrid coating is about 10-27 cm3/atom, being one or two orders of magnitude lower than that of polysiloxane. VUV radiation can affect the erosion process greatly. Under simultaneous AO and VUV exposure, the value of Ey of the polysiloxane/5iO2 （20 wt pct） hybrid coating increases by 3g% compared with that under single AO exposure.
文摘喀斯特地区特殊的地表、地下侵蚀产沙是引发石漠化发生发展的重要物理过程。以喀斯特山地石漠化过程中不同石漠化状况的裸坡面为研究对象,通过模拟其地表微地貌及地下孔(裂)隙构造特征,采用人工模拟降雨试验研究其地表及地下侵蚀产沙特征。结果表明:无石漠化、潜在石漠化和轻度石漠化的裸坡在相同条件下的地表产沙量总体上高于地下产沙量,且10 min降雨时段内地下产沙量在0~100 g之间。不同石漠化强度的裸坡地表、地下侵蚀产沙量均随雨强的增大而增加;小雨强(30~80 mm h^(-1))下,随着石漠化强度加剧其地表越不易发生侵蚀,而石漠化强度达到一定程度时(基岩裸露率40%)土壤流失以地下流失为主;大雨强(150 mm h^(-1))下,地表产沙量及其分配比例随基岩裸露率变化不明显,而地下产沙量则呈先增加后减小的变化且在基岩裸露率为30%时达到最大。不同石漠化强度的裸坡地表产沙量及其分配比例随地下孔(裂)隙度变化不明显,地下产沙量及其分配比例总体上随地下孔(裂)隙度增加而增加;在不同地下孔(裂)隙度下(1%~5%),地表、地下产沙量及其分配比例随基岩裸露率变化(10%~50%)差异较大。研究结果对认识喀斯特地区石漠化发生发展机制、揭示土壤侵蚀特征、防治地表地下水土流失具有重要的理论和现实意义。
基金funded by the National Key Research and Development Program of China (2017YFC0504505)the National Key Technology Support Program of China during the Twelfth Five-year Plan Period (2013BAC05B02, 2013BAC05B04)
文摘The Pisha sandstone-coverd area is among the regions that suffer from the most severe water loss and soil erosion in China and is the main source of coarse sand for the Yellow River. This study demonstrated a new erosion control method using W-OH solution, a type of hydrophilic polyurethane, to prevent the Pisha sandstone from water erosion. We evaluated the comprehensive effects of W-OH on water erosion resistance and vegetation-growth promotion through simulated scouring tests and field demonstrations on the Ordos Plateau of China. The results of simulated scouring tests show that the water erosion resistance of W-OH treated area was excellent and the cumulative sediment yield reduction reached more than 99%. In the field demonstrations, the vegetation coverage reached approximately 95% in the consolidation-green area, and there was almost no shallow trenches on the entire slope in the treated area. In comparison, the control area experienced severe erosion with deep erosion gullies appeared on the slope and the vegetation coverage was less than 30%. This study illustrated that W-OH treatment can protect the Pisha sandstone from erosion and provide the vegetation seeds a chance to grow. Once the vegetation matured, the effects of consolidation-growth mutual promotion can efficiently and effectively improve the water erosion resistance and ecological restoration.
基金DST (Department of Science and Technology), Govt. of India for financial support for this research projectSERB, DST, Government of India for awarding NPDF (National Postdoctoral Fellowship) (Reference No. PDF/2016/000286)the partial funding given to this project by GLACINDIA, CHARIS, INDICE, IFCPAR/CEFIPRA and SAC
文摘Present study shows suspended sediment dynamics in the meltwater of Chhota Shigri glacier,Himachal Pradesh,India for different melt seasons during the period 2011-2014.Maximum suspended sediment concentration in the meltwater was found during the month of July 2011,2012 and 2014 constituting to 55.2%,48.3% and 46.9%,respectively.Whereas in 2013,maximum suspended sediment concentration was observed in August accounting for46.1% of the total.On the other hand,maximum suspended sediment load was monitored in the month of July 2011,2012 and 2014 constituting 59.5%,63% and 55.7% of the total,respectively.Whereas in2013,maximum suspended sediment load was observed in the month of August accounting for 49.8% of the total suspended sediment load.Annual distribution of suspended sediment concentration(SSC)and suspended sediment load(SSL)in the Chhota Shigri glacier shows higher value of SSC and SSL during the study period 2012 and 2013,which may be due to the presence of high glacial runoff and negative mass balance of the studied area during these time periods.Marked diurnal variation has been observed in the SSC of meltwater.Strong correlation was observed between SSC and SSL with discharge.On the other hand,SSC and SSL also showed strong exponential correlation with air temperature of the studied area.Sediment yield from the catchment of Chhota Shigri glacier is high during the peak melt season(July and August)and low during the late melt season(September and October).The average value of erosion rate for Chhota Shigri glacier basin during the study period 2011-2014 was calculated to be 1.1mm/yr,which is lower than the average erosion rate of other Himalayan glaciers such as Rakiot,Chorabari and Gangotri glaciers,which may be caused by its geological setting containing high erosion resistant rocks such as granite,granite gneiss and porphyritic granite.
文摘Identifying land management practices(LMPs)that enhance on-site sediment management and crop productivity is crucial for the prevention,reduction,and restoration of land degradation and contributing to achieving land degradation neutrality(LDN).We reviewed studies in Ethiopia to assess the effects of LMPs on soil loss(84 studies)and crop productivity(34 studies)relative to control practice.Yield variability on conserved lands was assessed using 12,796 fixed plot data.Effects of LMP on soil loss were 0.5-55 t ha^(−1)y^(−1)compared to control practices yielding 50 to 140 t ha^(−1)y^(−1).More than 55%of soil loss records revealed soil loss less than the tolerable rate(10 t ha^(−1)).Area closure,perennial vegetation cover,agronomic practices,mechanical erosion control practices,annual cropland cover,and drainage groups of practices led to 74.0±18.3%,69.0±24.6%,66.2±30.5%,66.1±18.0%,63.5±20.0%,and 40±11,1%soil loss reduction,respectively.A yield increase of 25.2±15.0%,37.5±28.0%,and 75.4±85.0%was found from drainage,agronomy,and mechanical erosion control practices,respectively.The average yield loss by erosion on fields without appropriate land management practice and on conserved fields was 26.5±26.0%and 25±3.7%,respectively.The findings suggest that practices that entail a continuous presence of soil cover during the rainy season,perennial vegetation,retention of moisture,and barriers for sediment transport were most effective at decreasing soil loss and increasing productivity.This review provides evidence to identify the best LMP practices for wider adoption and inform decision-making on LMP investments towards achieving sustainable solutions to reverse land degradation.
