| A representative Holocene loess-soil profile is studied high-resolutionly in this thesis at Pacun , Yuzhou city in the upper reaches of the Huaihe River. Through field observation, sampling and experimenting, a lot of datas of grain-size, magnetic susceptibility at the loess-soil profile are gained. It is analyzed that the connections between the experiment data and sediment environment, sedimentary feature of the deposits. The analysis of mechanical grain-size composition and grain-size parameter is emphasized, including frequency curves, accumulative frequency curves, normal probability accumulative frequency curves, grain-size median, mean size, standard deviation, skewness, kurtosis. By discussing the similarity and distinction between the loess-soil substance in the upper reaches of the Huaihe River and that in the Loess Plateau, it is revealed that the source of loess-soil substance and the depositional dynamics of loess-soil in the upper reaches of the Huaihe River. Analyzed the frequency of the burst of the Yellow River, the sand damage of the northern and eastern of Henan and their influential factors, it is revealed that the human activity had greatly affected the burst of the Yellow River, the sand damage of the northern and eastern of Henan and the acceleration of the depositional ratio of the TS in Yuzhou. These have importantly actual significances to acquaint the substance composition, pedogenic change, Holocene loess sediment environment changes, and the depositional dynamics of the Yuzhou, these also have importantly actual significances to reflect the affection to soil erosion of the Loess Plateau, the burst of the Yellow River, the sand damage of the northern and eastern of Henan, and the sand storm by human activities. According to study, the thesis draws the following conclusions: (1) By comparison of the magnetic susceptibility and grain size of loess-soil profile in the Holocene among Yuzhou YPC profile, Longdong XJN profile and the JYC profile which is in the Guanzhong Basin, it is found that the magnetic susceptibility of loess-soil profile sequences in the upper reaches of the Huaihe River was much lower, the grain size was much thicker, and the separation is worse than those in the Loess Plateau and the Guanzhong Basin. It is represented that there are different substance source and depositional dynamics in the two areas. By contrast of the loess of the LoessPlateau, the substance source of the Upper reaches of the Huaihe River is closer, and the transport wind is stronger.(2) The source of loess-soil substance in the upper reaches of the Huaihe River is composed of both near and distant substance. The near substances are dominant, which are silt and clay deposits of the floodplain by the frequent breaching of dike and route-changing, overflowing of the Yellow River. The main depositional dynamics is the northeaster in the area. The distant substances are minority composition, and it is very thin dust carried by West wind in the upper air. The loess-soil sediment profile was formed by the local wind along NE direct and the west in the upper air.Since the penetration of the Yellow River, with massive silt by the soil erosion in the middle reaches, it pours into the plain of the lower reaches. With the decreasing of the gradient ratio, the mitigation of the velocity ratio, the transport dynamics abate, so massive silt is deposited in the riverbed. The riverbed is rising year after year, even some reaches are higher than the ground. Then it is easy to breach the dike, change the route and overflow the plain with massive silt and clay. The massive deposits provide continual substances, which deposited in the lower reaches of the regional wind mainly by northeaster. The transport dynamics of the loess is similar to the aeolian sand in the plain, and both substances are come from the soil erosion of the Loess Plateau.(3) The forming process of loess in the upper reaches of the Huaihe River is discussed. A large number of silt and clay were deposited in the plain by the frequent breaching of dike and route-changing, overflowing of the Yellow River since Yellow River formed. The dry and loose silt was blow by strong wind along NE direct in winter and spring, formed sandy windstorm, the thicker grain-size was carried by the form jumping and creeping, and the thinner grain was carried by the suspending form and deposited in the place about 20-150km distance beside the region of the silt source. At last, the former formed the sandy soil, but with the physical process, the chemical process and the biological pedogenic process, the latter became the sandy loess by the long-lasting wind blowing.(4) By comparison of the frequency of the burst of the Yellow River, climate change curve, the frequency of sandstorm, and the changes of cultivated areas and population, we found that the land cover and the land use of the middle of the Yellow River have been greatly changed by human activities after the Holocene climatic optimum. With the aggravation of soil erosion, the Yellow River pour more silt into the plain of thelower reaches, causing the higher riverbed, the acceleration of breach and overflow, the expansion of the floodplain, in a word more substance to transport. We also found that because of destroy of the land cover of the sandy land which had been fixed in the lower reaches of the Yellow River, the sand start to move again under the northeast wind, lead to severe soil erosion. All of these provide more sand to transport, lead to more soil erosion and sand storm, and also accelerate the depositional ratio of loess-soil in Yuzhou. So to reduce the soil erosion and the damage of sand storm, first we have to conserve water and soil in the middle of the Yellow River, on the other hand we have to fix the active sand and conserve the land cover of sandy land.
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