应用核磁共振技术分析干盐湖地区地下卤水空间分布特征——以昆特依干盐湖为例

昆特依干盐湖位于柴达木盆地西北部,为特大型综合盐类矿床.大盐滩是昆特依干盐湖内最大的盐滩,地下赋存有一定量的卤水矿床,但该矿床的水文地质条件差,主要卤水矿层含水性弱,开采难度大.核磁共振找水方法作为当今世界上唯一的直接找水地球物理新方法,具有高分辨力、高效率、信息量丰富和解的唯一性等优点,本文运用该方法对昆特依干盐滩地区地下卤水空间分布特征进行研究,通过对核磁共振数据进行处理与反演,结合已有的地质与钻井资料,对测点进行综合地质-地球物理解释,获得以下认识:1)大盐滩0~130 m深度范围内,共存在3个卤水含水层,主要呈扁平状或漏斗状、近似层状展布,W1为晶间潜卤水层,渗透系数较大,颗粒较粗,单位体积含水量为0.4%~2.7%,W2和W3为晶间承压卤水层,渗透系数较小,颗粒较粗,单位体积含水量分别为0.2%~1.1%和0.1%~0.8%;2)大盐滩地区存在两个卤水富集区,分别为研究区西南部沉积盆地中心的Ⅰ号富卤区和盆地东北部的Ⅱ号富卤区;3)根据区域内卤水富集分布以及构造情况,划定大盐滩向斜沉积中心、大盐滩北侧F1~F8及遥F6断裂发育区和冷湖构造带为区域内主要的找矿找水远景区;4)GMR核磁共振系统在干盐滩地区理论探测深度为130 m,该系统不仅可以有效地探测自由水,而且可以依据束缚水的分布解译地下各类含水盐类矿物和含水黏土矿物的存在与分布.     

陕北定边盐湖卤水水位历史演变及其气候指示意义(1265—1949年)

受自然环境和资料限制的原因,中国西北的季风边缘区内的湖泊千-百年时间尺度演变序列重建工作存在不足.历史文献中的湖泊演变信息丰富,有效利用可较好地解决这一问题.本文通过梳理历史文献记录的定边盐湖采盐方式资料,反演历史时期定边盐湖卤水水位,重建公元1265-1949年陕北定边盐湖卤水水位演变序列,该序列较好地指示出公元12...     

长江中下游湖泊群不同生活型水生植物分布的时空变化(1986—2020年)

不同生活型水生植物对水环境的影响和碳固持能力不同,开展大尺度范围内不同生活型水生植物的时空分布和动态变化研究,是全面掌握湖泊水生态环境变化趋势、准确核算水生生态系统碳源/碳汇的前提。以长江中下游10 km²以上(共131个)的湖泊为研究对象,基于野外调查和先验知识,通过光谱分析,研发了不同生活型水生植物遥感高精度机器学习识别算法,解析了长江中下游湖泊群不同生活型水生植物的时空变化规律。研究表明,长江中下游湖泊群不同生活型水生植物遥感监测精度为0.81,Kappa系数为0.74;1986—2020年长江中下游湖泊群水生植物面积为2541.58~4571.42 km²,占湖泊总面积的15.99%~28.77%,沉水植物是优势类型(Max_1995年=2649.21 km²,Min_2005年=921.38 km²),其次是挺水植物(Max_2005年=1779.44 km²,Min_2020年=569.05 km²)和浮叶植物(Max_2015年=685.68 km²,Min_2000年=293.04 km²);水生植物主要分布在长江干流流域湖泊群,其次是鄱阳湖流域、洞庭湖流域、太湖流域和汉江流域;变化趋势上,1986—2020年长江中下游湖泊群水生植物面积呈现先增长(1986—1995年)、后下降(1995—2010年)、再增加(2010年后)的趋势。本研究可为长江中下游湖泊群生态环境调查及水环境管理提供重要参考。     

青藏高原东南缘高山湖泊藻类响应气候变化和大气沉降的长期特征

高山湖泊远离人类活动直接影响,通常具有面积小、寡营养、食物网单一等特点,对气候变化和营养输入具有较高的敏感性。我国青藏高原东南缘地区氮沉降通量较高、增温幅度显著,已有研究显示该地区可能受湖泊类型、流域特征等影响存在差异性的湖泊响应模式。本研究选择该区域位于树线以下、具有不同水深的3个小型湖泊(盖公错纳、沃迪错、碧沽天池)开展沉积物调查和对比研究,通过钻孔样品测年、理化特征和藻类(硅藻群落、藻类色素)等多指标分析,结合区域气候定量重建和氮沉降等数据收集,评价了过去300年来藻类演替模式的异同特征及湖泊水深的调节作用。结果显示,3个湖泊中硅藻的优势物种与群落组成差异明显。深水型湖泊盖公错纳(最大水深39.4 m)的硅藻群落以浮游种为主(占比达82%),优势种为眼斑小环藻(Pantocsekiolla ocellata)、科曼小环藻(Pantocsekiella comensis);深水型湖泊沃迪错(最大水深20.7 m)的硅藻群落中浮游种和底栖种约各占50%,优势种为眼斑小环藻(Pantocsekiella ocellata)、连结脆杆藻(Saurosira construens);浅水湖...     

北京城区河湖水质分析

调研结果显示,2003年北京城区河湖(11个监测水体)总磷、总氮含量分别为0．142mg/L、1．481mg/L,已达到比较 严重的富营养状态．北京城市河湖属于藻型水体,初级生产力主要决定于浮游藻类的群落结构与密度．河湖水体中浮游 藻类密度为37867．82×10~4cells/L,其群落由蓝藻(Cyanophyta)、绿藻(Chlorophyta)、硅藻(Bcillariophyta)、甲藻(Pyrrophy— ta)、隐藻(Cryptophyta)、黄藻(Xanthophyta)、金藻(Chrysophyta)和裸藻(Eugleniphyta)构成．群落中蓝藻占绝对优势 (89．54%)．在近几年的夏秋季连续发生程度不同的微囊藻(microcystis)水华,对水体功能和城市景观造成了不良影响． 主要原因是：(1)氮磷和有机物的污染,(2)给城市河湖补给的水量少,(3)河湖生态系统被损害,水体自净能力差．本文 对如何改善北京城市河湖水质提出了建议．     

我国城市湖泊空间分布格局特征分析及影响因素探讨

城市湖泊作为城市与自然之间进行水气交换的蓝色空间,具有供水、防洪、休闲、气候调节以及改善城市生态环境等诸多生态服务功能。中国地域辽阔、城市众多,不同区域的城市湖泊受自然地理环境和社会经济发展等因素的影响而具有显著的空间差异特征。目前已有研究对我国省会城市和个别大型城市的湖泊空间分布及变化特征等开展研究,但全国范围内各行政等级单元内城市湖泊分布的空间格局及其影响因素仍缺乏综合分析。本研究基于中国城市湖泊数据集,从城市分布的地域单元、行政等级、城市规模3个方面对城市湖泊分布特征进行统计分析和比较,并结合自然和人类活动要素,初步探讨影响城市湖泊分布规模和丰度的主控因子。结果表明,2020年全国共有约11万个面积大于0.001km²城市湖泊(不包括太湖、滇池等大型湖泊),总面积约2112 km²,约占全国城市(遥感城市不透水层区域)面积的1.1%。城市湖泊的分布具有显著的集聚和分异特征,数量超过70%的城市湖泊分布在约20%的县(区)级行政单元,约21%的县(区)级行政单元基本没有(<10 m遥感影像分辨率下10个像元)城市湖泊分布。城市湖泊数...     

Did Lake Manly overflow at Ash Hill?

Near Ash Hill in the Mojave Desert, California, there is an impressive channel that is cut in bedrock. The channel is in a pass through which Lake Manly, the pluvial lake that occupied Death Valley, could have overflowed. Indeed, the channel has been attributed to such overflow. The pass, however, is 500 m above the highest shorelines of Lake Manly in Death Valley, and evidence from cores from dry lakes on either side of the pass does not support the overflow hypothesis. Despite its size, new field observations suggest that the channel was actually eroded by local runoff. Water from several tributaries collects into a single channel at this point, and the resulting discharge is apparently sufficient to cause retreat of a knickpoint from the downstream edge of the basalt flow into which the channel is cut. © 1998 John Wiley & Sons, Ltd.     

Impact of environmental factors on bacterial communities in floodplain lakes differed by hydrological connectivity

We analysed total bacterial number and mean volume of cells at three sites in each of ten floodplain lakes in the Middle Basin of the Biebrza River, North-Eastern Poland to test bacterioplankton communities change according to the distance to the river. The composition of the bacterial communities was determined by fluorescent in situ hybridization method. Total number of bacteria in the lakes ranged from 4.0 to 7.48 cells × 10⁶ mL⁻¹ with dominance by Actinobacteria, the contribution of which was positively correlated with water level. Old river channels (side-arms) featured Alpha- and Gammaproteobacteria. The community of Betaproteobacteria was limited by concentration of dissolved organic carbon. Archaea, in spite of a minor role (<3.65% of DAPI-4′,6-diamidino-2-phenylindole) in the communities, showed a positive relation to floodplain lake isolation. Multivariate analysis demonstrated that bacterioplankton in riverine lakes was similar to that in rivers, while lakes with limited water exchange showed a similarity to fertile lakes. Water level and nutrients were among the factors determining bacterial community structure.     

Analytical model of well leakage pressure perturbations in a closed aquifer system

Deep saline aquifers are commonly used for disposal and storage of various surface fluids. The target injection zone must be hydraulically isolated from overlying zones in order to ensure containment of the injected fluids. Improperly plugged nonoperational abandoned wells that penetrate the injection zone are the main potential leakage pathways. Leakage through such wells may cause an observable pressure signal in a zone overlying the injection zone; such a signal can be used to detect the leakage. In this paper we develop an analytical model to evaluate the pressure change induced by leakage through a well in a multilayer system. Unlike previous analytical models on the topic, our model uses a closed system, which may significantly affect the strength and behavior of the pressure signal induced by leakage. The analytical model is first presented for a two-layer system centered at the leaky well location. We evaluate the leakage-induced pressure change using the Laplace transform of Duhamel’s superposition integral, yielding the solution in the Laplace domain. We then derive a late-time asymptotic solution using the final value theorem, which suggests that the leakage rate becomes constant after sufficient time. We then obtain the multilayer solution by extending the two-layer solution and presenting it in matrix form in the Laplace domain. We apply the solution to three examples. In the first example, we apply the analytical model to a two-layer system, investigating its behavior and comparing the results with a numerical solution. In order to demonstrate behavior and potential applications of the multilayer analytical model, we present two multilayer examples: one with identical layers and another, replicating a CO₂ storage site, with dissimilar layers. The leakage-induced pressure change does not necessarily decrease as the distance increases from the injection zone toward the surface.     

应用EOS/MODIS资料监测河西内陆河下游水库湖泊水域的变化

利用EOS/MODIS资料,对2004年春季至秋季间分布在甘肃省河西境内的2个面积最大的水库———红崖山水库、双塔水库和位于内蒙古额济纳旗的东、西居延海湖泊的水体面积进行监测计算,并与近年同期平均值进行了对比分析,结果表明疏勒河、石羊河及黑河流域下游的水库湖泊水体面积都有不同程度的减小。