80年代黄河流域水利水土保持措施减沙作用研究

７０、８０年代黄河输沙量明显减少，引起了社会有关部门的高度重视。本文在分析、汇总黄河上、中游３０多条主要交流水沙变化及其原因研究成果的基础上，对成果进行调整和补充，提出了８０年代黄河三门峡水库以上流域水利、水土保持措施的减沙作用研究成果：采用水文法计算结果是，实测年均减沙量为９．０４９亿ｔ，计算年均减沙量为１１．８０６亿ｔ，其中降雨偏小影响的减沙量为４．０７８亿ｔ，水利措施的年均减沙量为２．５１４亿ｔ，水土保持措施年均减沙量为５．２１４亿ｔ；水保祛计算年均减沙量为１１．５７７亿ｔ，其中水土保持措施的年均减沙量为４．９８５亿ｔ。     

清涧河水沙变化分析

清涧河流域水土流失严重。年侵蚀模数在１００００ｔ／ｋｍ２以上。自５０年代初开展水土保持工作，截至１９８９年底止，共治理水土流失面积２２０４．０７ｋｍ２，治理程度达５０．６７％，流域输水输沙明显减少。分析表明：清涧河水沙减少受降雨和流域治理的共同影响，与１９６９年以前相比，７０年代年均减沙１５．４％，８０年代年均减沙７１．３％。在减沙量中，降雨偏枯影响７０年代占１４．６％～２８．２％，８０年代占３６．９％～４１．８％；流域治理减沙量７０年代占７１．８％～８５．５％，８０年代占５８．２％～６３．１％。同时，流域治理减水量也由７０年代的１８．２％～３３．９％增加到８０年代的４２．９％～４７．７％。     

黄河中游流域产沙量随降雨变化的区域分异

在黄河中游地区选择 5 0多个位于不同自然地理地带和地域的水文测站流域 ,流域面积从 5 0 0 km2 至 2 5 0 0km2 ,代表 6种不同自然地理类型。在流域降雨、泥沙及环境特征数据获得基础上 ,以不同自然地理类型流域为参数 ,建立了流域产沙量与降雨季节性、年际变化和年降雨量之间关系。结果表明 ,对于不同类型流域 ,产沙量与降雨季节性变率和年际变率之间有相当好的正相关关系 ,不同类型流域曲线的斜率各不相同 ,在图中所处的位置也不相同。由沙黄土、砒砂岩流域 ,经黄土流域、黄土 基岩流域 ,到基岩山地 黄土流域和基岩山地流域 ,曲线的斜率渐趋减小 ,曲线的位置由上而下呈有序的排列。流域产沙量与年降雨量之间关系遵循 L angbein— Schumm曲线 ,但是由沙黄土、披砂岩流域向基岩山地流域过渡 ,流域产沙量峰值趋于减小 ,而峰值出现所需要的降雨量渐趋增大。流域产沙量随降雨变化的特征是流域降雨、地面物质、植被和地貌发育程度等因素共同作用的结果。     

伊通河(长春市区段)沉积物重金属元素化学形态分布特征

对伊通河（长春市区段）沉积物中重金属元素的含量和形态的分布特征进行了研究。结果表明,重金属元素的总量呈现出沿河变化的趋势,且各重金属元素沿河变化程度有很大区别;沉积物中铁主要以残渣态存在,Mn、Pb、Cu、Zn元素残渣态含量很低,而有效态含量却很大（70%）,即伊通河沉积物中存在着潜在的重金属污染。沉积物中重金属在各形态的叠加也有所区别,Pb和Cu主要叠加在有机物态和残渣态中,而Zn则主要叠加在铁锰氧化物态中。     

小流域侵蚀产沙分布式数学模型的研究

 为反映因下垫面因子空间分布不均和人类活动对流域侵蚀产沙的影响,建立了基于场次暴雨的小流域侵蚀产沙分布式数学模型。该模型能够模拟出流域在不同水土保持措施(不同土地利用类型)下的径流和侵蚀产沙的时空过程,从而加强了在水土保持措施制定中的应用,并能够检测流域管理措施对径流泥沙过程产生的影响,进而为配置流域内水土保持措施和检测流域管理,提供技术支撑和科学依据。经黑草河小流域实测资料率定和验证,计算值与实测值符合良好。     

流域侵蚀产沙的尺度变异规律研究

 侵蚀产沙的尺度变异规律,是当今土壤侵蚀研究的前沿,它涉及的研究范围广泛,小到土壤颗粒,大到全球气候变化与碳循环过程。特别是不同尺度流域之间侵蚀产沙和输移,究竟有什么样的内在联系,小流域所获得的研究成果是否能推广应用到大中流域,已成为迫切需要解决的重要科学问题。有关流域侵蚀产沙与输移过程随流域尺度复杂变化的研究,国际上刚刚开始,国内有关流域尺度研究主要涉及于水文学领域的一些尺度研究,关于流域侵蚀产沙与输移过程随流域尺度复杂变化的研究不多。作者对国外当前土壤侵蚀模型的最新进展进行了综述,并对侵蚀产沙的尺度变异规律进行了分析。由于具有GIS强大的空间数据管理和分析能力,它将在流域侵蚀产沙尺度变异这一侵蚀产沙的问题研究中发挥重要作用。     

发展沟道人工湿地 改善基岩产沙区生态

随着沟道坝系工程建设的开展 ,黄土高原基岩产沙区出现了一些沟道湿地迹象。发展沟道人工湿地对于改善区域农业生态环境、增加生物群落、净化环境和水源等具有重要意义。鉴别和确认湿地的类属有利于湿地的研究、利用、保护和发展。依据我国湿地的定义、界定条件及类型等 ,对黄土高原基岩产沙区沟道治理形成的湿地进行了确认 ,并指出了其发展前景     

Implication of relationships among suspended sediment size, water discharge and suspended sediment concentration: the Yellow River basin, China

According to the yearly maximum suspended sediment concentrations (SSC) in the Yellow River and its tributaries, the rivers are divided into three types of more than 300, 20–300, and less than 20 kg/m³. The middle Yellow River basin is located in the transitional zone from subhumid to semiarid climates, and covered by a thick loess mantle. Neighboring on the desert areas to the northwest, the surface material of the Loess Plateau exhibits some marked areal differentiation in grain size and forms three zones covered by sandy loess, (typical) loess and clayey loess from northwest to southeast. Controlled by these physico-geographical conditions, the grain size of river-transported sediment shows some particular characteristics; at small water discharge or SSC, the grain size of suspended sediment abruptly decreases to a minimum with increasing water discharge or SSC. At water discharge of more than ca. 40 m³/s or at SSC of more than ca. 40 kg/m³, the grain size increases with water discharge or SSC.During the low-stage season, the relatively clear baseflow may scour the coarse bed materials, so the suspended sediment is relatively coarse. In the rainy season, rainstorm runoff washes out fine loess materials to the river, making suspended sediment fine. During relatively strong rainstorms, there often occur hyperconcentrated flows at SSC of more than 300 kg/m³. The relatively coarse grains could then remain suspended in the mixture of water and fine suspended sediment.     

Using the soil gas radon as an indicator for ground contamination by non-aqueous phase-liquids

1 The Problem  One of the major problems facing risk assessment at polluted industrial sites and military bases is subsurface contamination by non-aqueous phase-liquids (NAPLs), since tracing the extent of a NAPL plume using conventional methods (drive point profiling) is usually associated with difficulties. In an effort to trace subsurface contamination as precisely as possible, monitoring points are placed in the area that might be affected by contaminants, and groundwater and soil samples are taken to the laboratory for analysis. However, the final number of monitoring points is hardly ever sufficient for distinctive contamination mapping, and this may ultimately result in an unsuitable remediation action being taken. 2 Objectives  To obtain a more detailed image of a subsurface NAPL plume and, hence, to facilitate remediation measures that are best suited for the site in question, a denser network of monitoring points is desirable. The aim of the investigation described in this paper was therefore to develop a new detection method for subsurface NAPL contamination, which is based on an easily accessibleindicator for NAPLs rather than on the analysis of soil and groundwater samples taken at the site. Based on the good solubility of radon in NAPLs, the idea was put forward that subsurface NAPL contamination should have an influence on the natural radon concentration of the soil gas. Provided this effect is significant, it would be possible to carry out a straightforward radon survey on an appropriate sampling grid covering the suspected site and thus enabling the NAPL contamination to be detected by the localization of anomalous low radon concentrations in the soil. The overall aim of the investigation was to assess the general suitability of the soil-gas radon concentration as an indirect tracer for NAPL contamination in the ground. 3 Methods  The partitioning coefficient K_NAPL/air is one of the most influential parameters governing the decrease of the radon concentration in the soil gas in the presence of a subsurface NAPL contamination. Since NAPL mixtures such as gasoline, diesel fuel and paraffin are among the most important NAPLs regarding remediation activities, laboratory experiments were performed to determine the radon-partitioning coefficient for these three NAPL mixtures. Field experiments were carried out as well. The aim of the field experiments was to test the use of the soil-gas radon concentration as a tracer for NAPL contamination on-site. For the field experiments, each site was covered with a suitable grid of soil gas sampling points. Finally, the lateral radon distribution pattern achieved on each of the sites was compared to the respective findings of the earlier research performed by conventional means. 4 Results and Discussion  The results of the laboratory experiments clearly show a very strong affinity of radon to the NAPL mixtures examined. The partitioning coefficients achieved correspond to those published for pure NAPLs (Clever 1979) and are thus in the expected range. The results of the field experiments showed that the minimum radon concentrations detected match the respective NAPL plumes traced previously. 5 Conclusions  Both the results of the lab experiments and the on-site findings demonstrate that the soil-gas radon concentration can be used as an indicator for subsurface NAPL contamination. The investigation showed that NAPL-contaminated soil volumes give rise to anomalous low soil-gas radon concentrations in the close vicinity of the contamination. The reason for this decrease in the soil-gas radon concentration is the good solubility of radon in NAPLs, which enables the NAPLs to accumulate and ‘trap’ part of the radon available in the soil pores. 6 Recommendations and Outlook  Further research is required into contamination with rather volatile NAPLs such as BTEX. Further research is also needed to examine whether it is possible to not only localize a NAPL plume, but also to obtain some quantitative information about the subsurface NAPL contamination. The authors also believe that additional investigations should be carried out to study the ability of the method to not just localize a NAPL contamination, but also to monitor on-site, clean-up measures.     

Historical Trace Metal Accumulation in the Sediments of an Urbanized Region of the Lake Champlain Watershed, Burlington, Vermont

This study documents the history ofpollution inputs in the Burlington region of LakeChamplain, Vermont using measurements of anthropogenicmetals (Cu, Zn, Cr, Pb, Cd, and Ag) in four age-datedsediment cores. Sediments record a history ofcontamination in a region and can be used to assessthe changing threat to biota over time and to evaluatethe effectiveness of discharge regulations onanthropogenic inputs.Grain size, magnetic susceptibility, radiometricdating and pollen stratigraphy were combined withtrace metal data to provide an assessment of thehistory of contamination over the last 350 yr inthe Burlington region of Lake Champlain. Magneticsusceptibility was initially used to identify land-usehistory for each site because it is a proxy indicatorof soil erosion. Historical trends in metal inputs inthe Burlington region from the seventeenth through thetwentieth centuries are reflected in downcorevariations in metal concentrations and accumulationrates. Metal concentrations increase above backgroundvalues in the early to mid nineteenth century. Themetal input rate to the sediments increases around1920 and maximum concentrations and accumulation ratesare observed in the late 1960s. Decreases inconcentration and accumulation rate between 1970 andthe present are observed for most metals. Theobserved trends are primarily a function of variationsin anthropogenic inputs and not variations in sedimentgrain size. Grain size data were used to removetexture variations from the metal profiles and resultsshow trends in the anthropogenic metal signals remain. Radiometric dating and pollen stratigraphy providewell-constrained dates for the sediments therebyallowing the metal profiles to be interpreted in termsof land-use history.