| The problem of hydraulic erosion of long and gentle slope cultivated land in the black soil area of northeast China was serious.Grass filter strips was a kind of ecological engineering measure which was easy to manage,less investment and effective.This article in view of the northeast black earth area,gentle slope farmland soil erosion problems,through three different flowings under the condition of scour simulation test,the research of3 m bandwidth grass filter strips on runoff,sediment,nitrogen and phosphorus of hindered effect,analysis of aggregate grassed filter belt migration and the influence of sedimentation,sediment source and the REE tracer technology analysis,to black soil district gentle slope cultivated land provided a scientific basis for prevention and control of soil and water loss.The main research conclusions were as follows:(1)When the scour flow was 0.25L/s,0.375L/s and 0.5L/s,the average interception rate of the herbage filtration zone to runoff was 30.68%,35.81% and 31.68%,respectively.The average interception rate of sediment was 25.15%,32.73% and 33.49%,respectively.Combined with the analysis of runoff rate and sediment transport rate,the grass filter strips has a better blocking effect on runoff and sediment under the condition of 0.375L/s.The total nitrogen concentration decreased with the increase of the scouring flow,and the total phosphorus concentration increased with the increase of the scouring flow.(2)Under different scouring flow conditions,about 30% of micro aggregates <0.25 mm were lost along with runoff,which was larger than the soil samples tested.With the increase of scouring flow,the herbage filter belt mainly intercepts large aggregates in runoff,but the interception effect of micro-aggregates is poor.When the flow rate is large,the deposition amount of micro-aggregates on the slope is in front of the > belt in the > belt after the belt,while the deposition amount of large aggregates is behind the > belt in the > belt before the belt.It is found that MWD and GMD can better reflect the characteristics of the lost soil aggregates.(3)The average interception rate of runoff under different flow conditions was 36.62%,24.31%,35.02% and 47.52% respectively when the runoff was scour in turn according to flow rates of 0.375L/s,0.5L/s,0.375L/s and 0.25L/s.The average interception rate of sediment was 45.07%,2.26%,26.14% and 43.21%,respectively.When the traffic gradually decreases,the overall interception effect tends to be better.(4)When scouring by flow rate of 0.375L/s,0.5L/s,0.375L/s and 0.25L/s,the micro-aggregates in runoff and sediment were about 40%,and the proportion of large aggregates was nearly 60%.The deposition rate of microaggregates before,in and after theherbage filter strips ranged from 28.66% to 36.42%,and that of large aggregates ranged from 63.58% to 71.34%.The large aggregates in runoff were still intercepted in the herbage filter strips.The deposition amount of micro-aggregates in the slope was in front of the >belt,while the deposition amount of large aggregates was in front of the > belt.(5)REE tracer technique was used to determine sediment sources under multiple scouring conditions.It was found that in runoff sediment,erosion sediment mainly came from runoff flow of 0.5L/s,that was,there were many Ce markers.In the slope sediment deposition,the pre-belt sediment mainly comes from the runoff of 0.25L/s,that was,the Nd element marks more,the sediment in the middle and after the belt mainly comes from the runoff of 0.5lL/s,that was,the Ce element marks more. |
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