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本文研究了易溶性复盐钾光卤石(KCl·MgCl_2·6H_2O)的溶解机理及动力学。利用相图控制在固相光卤石饱和区的情况下研究改变温度、浓度、搅拌速度及成块压力对光卤石溶解过程的影响,发现MgCl_2、KCl首先以近相等的速度且出现KCl:MgCl_2的摩尔比值>1进入溶液,随后KCl从溶液中结晶出来。KCl在整个溶解过程中明显分为两个阶段,即以溶解为主导的过程和以结晶为主导的过程;在溶解时,MgCl_2受扩散控制,KCl属化学溶解过程,KCl结晶受扩散控制,获得了动力学的方程计算出MgCl_2的溶解活化能和KCl的溶解和结晶活化能。 相似文献
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本文根据1987、1991和1992年120个钻孔剖面岩性资料得出,察尔汗盐湖首采区及其附近地区上岩层中光卤石主要分布在首采区范围内,首采区外的东部、北部和东南部亦有少量分布.其分布井段一般为埋深3~10m.光卤石主要分布在中细粒致密(或松散)和含粉砂中粗粒松散石盐层中,多呈散状或似层状分布;在碎屑层中亦有少量光卤石分布.并对光卤石成因和沉积演化进行了初步讨论. 相似文献
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Dissolution of extensive outcrops of limestone and dolostone in humid tropical and subtropical southern China produced numerous caves and residual hills that are referred as tower karst. This study identifies and relates the physical and chemical characteristics of the surface sediment with the limestone bedrock in Guilin to assess the influence of the limestone dissolution process on sediment composition.The results of this study indicated that (i) both limestone and dolostone of the region are very pure (99.5% and 98.5% of CaCO3 and MgCO3, respectively); (ii) the material composition of limestone and dolostone is different from that of soil and sediment of the region: constituents of surface sediments are highly related with the clastic sedimentary rocks, such as the mudstone, but show negative correlation with limestone and dolostone; (iii) the limestone formations are highly resistant to physical weathering and disintegration; their durability versus physical weathering and their high susceptibility to chemical dissolution account for why residual towers can form and persist; (iv) a dual-zone environmental structure exists vertically downward from the surface in Guilin: the zone of unconsolidated clastic sediments that is predominantly acidic, and the zone of karstified limestone that is predominantly basic. The evidence suggests that the environment and processes differ in these two zones. The chemical dissolution of limestone that formed tower karst of the region is not mainly responsible for the accumulation of clastic sediment on the surface. 相似文献
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2001-2010年鄱阳湖采砂规模及其水文泥沙效应 总被引:4,自引:0,他引:4
在长江主河道采砂行为于2000年全面禁止之后,受中国长江中下游房产建筑行业的砂石需求的驱动,大量采砂船转移到鄱阳湖采砂,这种规模化的采砂行为对鄱阳湖的水文环境产生的影响还缺乏定量研究.本研究通过利用地形数据、水文数据和卫星遥感数据,分析了鄱阳湖2001-2010年的采砂场的空间分布和采砂量,定量分析了采砂行为对鄱阳湖水文和泥沙的影响.研究结果表明:①2001-2007年鄱阳湖采砂船主要集中于松门山以北的通江河道,2007年以后采砂行为扩张到鄱阳湖中部;②2001-2010年间,鄱阳湖采砂面积范围大约为260.4 km2,挖沙平均深度4.95 m,采砂量达到1.29×109m3或2154Mt,体积上相当于使鄱阳湖库容增加了6.5%,重量上相当于1955-2010年以来鄱阳湖自然沉积量的6.5倍;③鄱阳湖采砂通过扩大通江河道的过水断面面积,加快了湖水注入长江速率,是引起近年来鄱阳湖秋冬季枯水期提前、枯水期延长的主要原因之一;④鄱阳湖采砂过程中通过挖沙、洗沙使沙场附近的水体含沙量增加、水体透明度降低,从而影响长江河道的泥沙平衡. 相似文献
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Lake sediments can be significantly impacted by industrial activities. These impacts vary among sites and include both local
point sources and atmospherically-derived pollution. Here we present results of a lake sediment pollution record from Ullswater,
UK, where lead mining activities have taken place within the catchment since 1690, although large-scale mining did not begin
until 1840. Metal concentration data from 12 cores taken along a lake bed transect illustrate that lead mining at Greenside
Mine had a significant impact on the lake sediments. High Pb concentrations were identified throughout Ullswater, and exhibited
a spatial gradient from south to north, with concentrations decreasing with greater distance from the main source of input
at Glenridding. Furthermore, inter-element correlations exhibit spatial variation that reflects the processes by which they
are incorporated into the lake sediment record. Together, these observations illustrate potential shortcomings in palaeoenvironmental
reconstructions and pollution studies based on single cores from large and morphologically variable lakes. Sedimentation rates
were estimated by matching this pollution record with the historical record of mining activities. Within Ullswater, sedimentation
rates from 1840 to the present varied from 0.67 to 2.33 mm year−1 with a mean of 1.4 mm year−1; highest sedimentation rates were observed in the deepest section of the lake and close to the main inputs, and lowest sedimentation
rates were observed in the northern part of the lake, furthest from the main input. Despite the considerable changes in mining
techniques and production, there is little evidence to suggest significant changes in sedimentation rates over time. 相似文献
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Kumtagh Desert is one of the eight biggest deserts in China, but poorly investigated before our interdisciplinary study because of the difficulty of access. In this paper, 33 representative surface sediment samples were collected from the Kumtagh Desert and analyzed in the laboratory to obtain heavy mineral components and geochemical element contents. Results show that various kinds of heavy minerals are present in these samples, with high levels of epidote and hornblende. Si and Al take up a large part of chemical composition. Compared with the average composition of geochemical elements of the upper continental crust (UCC), except Si and Ca, all elements are depleted to a certain degree; Fe, Mg, Ca, P, Ti and Mn have high correlation coefficients in their contents. The mineral and geochemical composition of the Kumtagh Desert sediments have a similarity with that of rocks of Altyn Tagh Mountains, and the surface sediments of the alluvial/diluvial fans around the Altyn Tagh Mountains and that of the Taklamakan Desert, indicating that one major source of the Kumtagh Desert sediments is located in the Altyn Tagh Mountains. Alluvial deposits and lake sediments in Aqik valley and lower reaches of Shule River are prone to be eroded and transported by the strong northeasterly wind into the Kumtagh Desert, forming another source of the desert deposits. An A-CN-K ternary diagram shows that a weak degree chemical weathering by the loss of Na and K occurred in these sediments, whereas A-CNK-FM ternary diagram suggests that Fe and Mg have undergone a significant chemical differentiation. Physical weathering processes cause easy erosion and enrichment in fine particles for mafic minerals, thus coarse desert sand particles can be relatively depleted in Fe and Mg. The mineral and geochemical composition of sediments in arid regions experiencing less chemical weathering are mostly affected by physical weathering. 相似文献
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根据1958-2013各年代长江河口河槽海图水深资料,利用Arcmap地图分析软件建立不同时期的水深数据库,以河口河槽水体和泥沙容量为研究对象,结合典型潮汐过程和典型年代水沙同步实测资料,计算长江口各分汊河槽最大理论进潮量和悬沙含量,探讨近50年来长江分汊型河口河槽水体和泥沙容量的变化过程和影响因素.结果表明:①北港河槽总体稳定,南港河槽仍处于发育阶段,南港河槽发育中心在南港下段,北港河槽上段区域略有萎缩;②目前,南、北槽河槽由于工程影响仍处于持续调整过程中,进潮量主增区域在南港和南槽,北槽发育模式已经被固定和限制.③近30年来,由于流域来水来沙减少,同时北槽深水航道工程的建设,使南、北槽进潮量和悬沙通量及其比例均发生了显著变化;④南北港水道悬沙量主要集中于北港下段及南北槽区域,其洪枯季悬沙含量的变化主要受冬夏季风和海洋动力条件的影响. 相似文献
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基于Budyko假设和分形理论的水沙变化归因识别——以北洛河流域为例 总被引:1,自引:0,他引:1
全球气候变化及人类活动深刻影响了区域水文过程,进行水沙变化归因识别对流域生态保护和高质量发展尤为重要。基于Budyko假设和分形理论,采用弹性系数法,对北洛河流域上(丘陵沟壑区)、中(土石山林—高塬沟壑区)、下游(渭北旱塬农区)3种不同地貌和植被类型区1959—2019年的水、沙通量变化进行归因分析。结果表明,北洛河上、中、下游径流量均显著减少,由20世纪60年代的35 mm、32 mm、34 mm,减少到21世纪10年代的19 mm、24 mm、6 mm,60 a减少率分别为0.3 mm a-1、0.2 mm a-1、0.4 mm a-1。上游输沙量极显著减少,中游降低趋势不显著,下游显著减少,由20世纪60年代的99×106 t、8×106 t、3×106 t,减少到21世纪10年代的10×106 t、3×106 t、0.3×106 t,60 a减少率分别为1.5×106 t a-1、0.04×106 t a-1、0.1×106 t a-1。20世纪70年代以来,上游径流变化逐渐受人类活动影响,且影响程度逐渐增强,21世纪10年代人类活动贡献率达66.3%;气候变化是中游径流变化的主控因子,21世纪10年代降雨和潜在蒸散发的贡献率分别为77.0%和20.2%;下游径流减少主要为人类活动影响,21世纪10年代其贡献率为64.3%。对比20世纪60年代流域输沙量变化始终受人类活动主导,21世纪10年代人类活动对上、中、下游输沙量减少的贡献率分别为80.7%、59.2%和92.7%。上游人类活动对输沙量减少的贡献中,退耕还林等沟坡措施和沟道工程措施分别为39.0%、42.7%,中、下游人类活动贡献的估算结果反映出高植被覆盖区和农区汲水灌溉对区域水、沙的影响特征。 相似文献
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