柴达木盆地卤水型Li、Rb关键金属矿产元素分布特征及富集机制

针对柴达木盆地卤水型锂(Li)和铷(Rb)关键金属矿产资源分布规律不清、富集机制不明的问题,全面调查了盆地第三系古卤水和第四纪现代盐湖卤水中的Li、Rb资源分布规律.研究显示,大风山、南翼山、油泉子、尖顶山、碱石山含油背斜构造古卤水Li、Rb资源禀赋较好,Li平均含量达81.1~128.9mg L^?1,Rb平均含量达4.5~29.2mg L^?1,均具有很好的开发利用前景;柴达木盆地东台、西台、一里坪盐湖及涩聂湖中,除已知的较好Li资源禀赋外,Rb含量最高可达12.5mg L^?1,亟需关注Rb资源的开发利用.基于水体氢、氧和硼同位素特征进一步查明了卤水Li和Rb资源的富集机制,第三系古卤水δD、δ¹⁸O平均值为?40.7‰和2.84‰,多数富Li、Rb古卤水的δD、δ¹⁸O与岩浆水接近;低于河水而与地热流体接近的δ¹¹B值说明,除蒸发作用和水-岩反应外,深部岩浆热液流体的补给才是古卤水矿种元素超常富集的关键机制.而现代盐湖卤水Li、Rb资源的超常富集与火山地热水的补给密切相关,盆地西部盐湖晶间卤水相对高的Li、Rb含量和垂向上随深度增加而Li、Rb含量有所增加的规律,则是由局部古卤水沿断裂带上涌补给造成.     

九江地震台观测井水氢氧同位素特征及意义

在地震地下流体观测研究中,基于氢氧同位素示踪技术研究地下水补给源及循环过程是常用的技术方法之一。本文给出了九江地震台2号观测井水、大气降水、周边水库水及高山泉水等样品的氢氧同位素测定结果,表明地下水δ~(18)O测值介于-7.59‰～-6.09‰,平均值-6.99‰,δD测值介于-45.22‰～-39.69‰,平均值-42.32‰,变异异数分别为0.09、0.16;大气降水δ~(18)O测值介于-13.00‰～-1.27‰,平均值-4.74‰,δD测值介于-96.13‰～-4.74‰,平均值-46.87‰,变异异数分别为0.40、0.56,与降水相比,地下水氢氧同位素变化更为稳定。大气降水氢氧同位素2017年5～10月表现为明显的降水效应,2018年11～4月表现为明显的温度效应,而地下水氢氧同位素并未表现出明显的降水效应和温度效应。氢氧同位素及过量氘揭示地下水在下渗补给前经历了明显的蒸发分馏作用,并与围岩进行~(18)O交换,δ~(18)O与δD计算得出的补给高程分别约为647、440m。九江台观测井的观测层地下水为大气降水成因的构造裂隙水,属于大气成因型且循环过程为较稳定的裂隙水补给并形成承压自流井。     

青藏高原盐湖卤水中溴的分布特征及来源初探

溴是完备工业体系的关键必备元素。盐湖卤水是溴的重要来源。青藏高原盐湖众多,富含钾、锂、硼等资源元素,开发潜力巨大。然而,目前针对青藏高原盐湖溴浓度、分布特征及其物源的研究仍然薄弱。本次研究采集了26个青藏高原盐湖表卤水样品并分析其溴浓度,进一步总结其他64个已报道盐湖数据,系统分析了青藏高原盐湖溴浓度分布特征,并进一步探讨了溴的可能物源。结果表明:青藏高原盐湖表卤水溴分布在0.5~246.8 mg/L之间,平均为41.1 mg/L,其中,碳酸盐型盐湖卤水平均溴浓度最高(47.0 mg/L),且集中分布在高原南部,而氯化物型盐湖平均溴浓度最低(30.1 mg/L),盐湖溴浓度呈现自南向北降低的趋势;青藏高原盐湖中溴有多种来源,高原南部富溴盐湖溴的来源可能主要与热泉补给有关,而柴达木盆地盐湖高溴来源可能主要与深部地层水(如油田水、背斜构造裂隙孔隙水、砂砾孔隙卤水、气田水等)补给有关。     

柴达木盆地尕斯库勒盐湖地表水-地下水的转化与铀的补给通量

流域范围内地表水和地下水转化对盐湖成盐元素的运移和富集具有十分重要的意义.本文通过尕斯库勒盐湖盆地内流域水体的水化学和B同位素特征识别了地表水和地下水之间的定量转化关系,在此基础上估算了流域中铀的补给通量.结果表明,流域水体中离子的分异除了蒸发浓缩作用之外,还受重力分异及掺杂作用的影响;上游库拉木勒克萨伊河和阿特阿特坎河水体在出山口附近转入地下并在中游补给地表水和地下水,其补给率分别占48.8%和51.2%,年均补给量分别为1.08×108和1.13×108m3/a;在中游至尾闾盐湖段,阿拉尔河和侧向补给对盐湖卤水的补给率占55.2%,深部水体的补给占44.8%;至少从5.7 ka以来,上游水体对盐湖卤水中铀的补给通量为4.11×103t,在湖积平原黏土沉积带以及祁漫塔格山前局部还原带可能具有较大规模的铀矿.研究结果有助于建立盐湖盆地水循环模式、揭示卤水资源形成机制;同时为尕斯库勒盐湖盆地水资源的高效利用和寻找铀矿提供理论依据和技术支持.     

全球尺度海拔高度对陆地高等植物的叶蜡正构烷烃δD值的影响初探

野外研究表明叶蜡δD_(n-alkane)值可以作为古高度重建的代用指标.然而,由于缺乏全球范围叶蜡δD_(n-alkane)值对高度的分析,限制了全球范围内叶蜡δD_(n-alkane)值作为古高度重建代用指标的可靠性.基于全球植物叶蜡δD_(n-alkane)值的数据库,分析了陆生高等植物叶蜡δD_(n-alkane)值随海拔高度的变化.叶蜡δD_(n-alkane)值随高度增加而下降的趋势对应于降水δD(δD_(prec))值随高度的变化,表明叶蜡δD_(n-alkane)值可以有效记录δD_(prec)值的变化.当消除纬度效应时,全部植物叶蜡δD_(n-alkane)-高度的递减率为(-1.01±0.10)‰(100m)~(-1),而双子叶植物和单子叶植物分别为(-1.03±0.13)‰(100m)~(-1)和(-0.47±0.13)‰(100m)~(-1).我们的研究证实了利用叶蜡δD_(n-alkane)值获取全球古高度变化的指标是可靠的,全球叶蜡δD_(n-alkane)-高度的整体递减率为叶蜡未调查区域提供了古高度重建的一种选择.     

古骨可溶性胶原蛋白的提取及其重建古食谱的可行性分析

当前在古食谱研究中,胶原蛋白(不可溶性)的提取,主要采用明胶化法.然而,胶原蛋白的直接降解产物——可溶性胶原蛋白,常常予以忽视并摒弃.本文通过凝胶层析,分管提取了古骨的酸提取液,从中分辨出三个峰,对各峰提取物的C和N含量,C/N摩尔比值及稳定同位素比值进行分析,并与对应的不可溶胶原蛋白(ISC)进行了比较,以探讨可溶性胶原蛋白(SC)在古食谱研究中的可行性.三个峰中,第二峰(保留时间在17.5~27.5 min)峰形最为平缓,表明其所含蛋白质的分子量不一致;其各管提取物,在C和N含量,C/N摩尔比值上与ISC最为接近.基于以上发现,可以看出,第二峰提取物即为SC.更为重要的是,两种蛋白的δ13C值和δ15N值均相近.具体而言,C/N摩尔比值落于正常范围的SC,与对应的ISC相比,δ13C差异的平均值仅为(0.3±0.2)‰(N=2),δ15N值大约相差(0.6±0.1)‰(N=2);而C/N摩尔比值稍高于正常范围的SC,与对应的ISC相比,δ13C差的平均值也仅为(0.4±0.1)‰(N=2),δ15N值也约相差(0.3±0)‰(N=2).这些差异,远低于δ13C和δ15N值在食物链营养级之间的差异(δ13C约为1‰~1.5‰,δ15N值约为3‰~5‰),表明SC与ISC具有相似的性质,其C和N稳定同位素分析,在古食谱研究中极具应用价值.     

柴达本盆地沙下盐湖的卤水化学及矿物沉积特征——以察尔汗盐湖区北部外围地带为例

对柴达木盆地察尔汗盐湖区外围沙下盐湖的卤水及沉积进行了综合研究。沙下盐湖卤水化学组成与地表径流和开放性盐湖卤水之间存在明显的差异性,具有高Na~++Cl~-、低Mg~(2+)+Ca(2+)+SO_4~(2-)、贫K~++CO_3~(2-)+HCO_3~-等特征。沙下盐湖析盐层位含有新生矿物并夹带碎屑矿物,其盐类矿物组合为:石盐+羟氯镁铝石+光卤石。25℃等温蒸发相图表明,其卤水演化方向往光卤石析出区迁移,在穿越上覆盖层通道中卤水发生的物理化学反应与独特的沉积特征,可以作为继续寻找沙下盐湖的指导。     

中国北方黄土区C-3草本植物碳同位素组成研究

对生长在我国北方黄土区的367个C-3草本植物样品进行了碳同位素分析, 结果表明我国北方黄土区C-3草本植物δ ¹³C值分布区间为-21.7‰ ~ -30.0‰, 平均值为-26.7‰; 黄土高原中部半湿润区的C-3草本植物δ ¹³C值分布集中, 在-24.4‰ ~ -28.5‰之间, 平均值为-27.5‰; 而黄土高原西部边缘的半干旱-干旱气候区的C-3植物δ ¹³C值变化范围在-21.7‰ ~ -30.0‰, 平均值为-26.2‰; C-3植物的δ ¹³C值在黄土高原中部的半湿润气候区比黄土高原西部边缘半干旱-干旱气候区显著偏轻. 年降雨量是造成这种显著偏轻的主要原因, C-3植物的碳同位素组成随着年降雨量的减少而变重, 在我国北方黄土区年降雨量每增加100 mm, C-3植被 δ ¹³C平均值将偏负约0.49‰左右.     

碳氮稳定同位素示踪鄱阳湖流域蚌湖丰水期的氮污染

鄱阳湖边缘深水区是鄱阳湖水位上涨时扩散而成的低洼湖区,通过对其一典型边缘湖泊——蚌湖丰水期的氮浓度和同位素特征值的检测,分析这类洪泛湖泊在水位最高时期水体颗粒有机质及无机氮的氮同位素变化特征,并识别氮污染来源及转化途径.结果表明:6月悬浮颗粒有机质碳氮同位素值(δ~(13)C:-26.7‰~-23.7‰,δ~(15)N:2.6‰~6.2‰)介于土壤有机质(δ~(13)C:-25.21‰±0.52‰,δ~(15)N:3.79‰±0.37‰)和水生植物的碳氮同位素值(δ~(13)C:-28.8‰~-24.9‰,δ~(15)N:5.3‰~8.2‰)之间.7月相比于6月,降低的δ~(13)C(-27.6‰~-23.2‰)和升高的δ~(15)N(4.3‰~7.7‰)表明暴雨冲刷带来更多的周边陆地碎屑输入.无机氮在6月以铵态氮(NH_4~+-N)为主要形态,7月以硝态氮(NO_3~--N)为主要形态.6月δ~(15)NH_4~+较负的特征值(-18.6‰±5.2‰)表明铵态氮主要来源于雨水,硝态氮(δ~(15)NO_3~-:1.4‰±3.0‰)主要来源于农业化肥和雨水.7月相比于6月,铵态氮和硝态氮的浓度和同位素值都大幅升高(分别升高了0.3和2倍,6‰和3‰),是暴雨冲刷陆地使农业化肥、城镇生活废水和畜禽养殖废水输入的结果.水生植物的δ~(15)N在7月(8.8‰±1.1‰)相比于6月(6.6‰±1.1‰)也升高了较多,是由于水生植物吸收了更高δ~(15)N废水无机氮的结果.通过颗粒有机质和无机氮的δ~(15)N分析可知,湖区水体氮的矿化作用和硝化作用较强,藻类对湖泊的内源氮贡献较弱,沿河湖的畜禽养殖在暴雨时对水域污染的威胁较大.本研究提供了洪泛湖泊氮污染治理的科学依据.     

塔里木盆地西部古岩盐氯同位素分布特征与找钾分析

塔里木盆地在晚白垩-第三纪地史发展过程中, 曾与广海相通, 多期海水的侵入和间断以及适宜的构造、古环境条件使得其内部发育的两大次级盆地—— 北部库车及西南莎车盆地沉积厚层岩盐, 具备成钾的基本地质条件, 一直被列为中国寻找古钾矿的重点地区. 但由于该区岩盐普遍贫Br, 使得经典的Br×103/Cl系数法找钾往往难以反映实际成盐情况. 而对该盆地不同地区盐矿点古岩盐氯同位素分析发现, 莎车及库车产出的岩盐氯同位素分布明显不同, 前者显著偏负, 后者则全为正值. 结合现有关于卤水、岩盐氯同位素研究数据, 参考岩盐Br×10³/Cl系数、卤水水化学特征, 证明δ³⁷Cl值是贫Br地区指导找钾的一有效指标. 运用这一指标推测, 莎车盆地形成岩盐的古卤水浓缩程度明显高于库车盆地, 特别是莎车盆地西部的喀什坳陷δ³⁷Cl值最为偏负, 推测当时成盐古卤水已浓缩到晚期阶段, 可作为一找钾远景区开展更进一步调查研究.     

SCIENCE CHINA Earth Sciences SUBJECT INDEX TO VOLUME 57(2014)

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Distribution of throughfall and stemflow in multi‐strata agroforestry,perennial monoculture,fallow and primary forest in central Amazonia,Brazil

The partitioning of rain water into throughfall, stemflow and interception loss when passing through plant canopies depends on properties of the respective plant species, such as leaf area and branch angles. In heterogeneous vegetation, such as tropical forest or polycultural systems, the presence of different plant species may consequently result in a mosaic of situations with respect to quantity and quality of water inputs into the soil. As these processes influence not only the water availability for the plants, but also water infiltration and nutrient leaching, the understanding of plant effects on the repartitioning of rain water may help in the optimization of land use systems and management practices. We measured throughfall and stemflow in a perennial polyculture (multi‐strata agroforestry), monocultures of peach palm (Bactris gasipaes) for fruit and for palmito, a monoculture of cupuaçu (Theobroma grandiflorum), spontaneous fallow and primary forest during one year in central Amazonia, Brazil. The effect on rain water partitioning was measured separately for four useful tree species in the polyculture and for two tree species in the primary forest. Throughfall at two stem distances, and stemflow, differed significantly between tree species, resulting in pronounced spatial patterns of water input into the soil in the polyculture system. For two tree species, peach palm for fruit (Bactris gasipaes) and Brazil nut trees (Bertholletia excelsa), the water input into the soil near the stem was significantly higher than the open‐area rainfall. This could lead to increased nutrient leaching when fertilizer is applied close to the stem of these trees. In the primary forest, such spatial patterns could also be detected, with significantly higher water input near a palm (Oenocarpus bacaba) than near a dicotyledonous tree species (Eschweilera sp.). Interception losses were 6·4% in the polyculture, 13·9 and 12·3% in the peach palm monocultures for fruit and for palmito, respectively, 0·5% in the cupuaçu monoculture and 3·1% in the fallow. With more than 20% of the open‐area rainfall, the highest stemflow contributions to the water input into the soil were measured in the palm monocultures and in the fallow. Copyright © 1999 John Wiley & Sons, Ltd.     

A Monte Carlo study of rainfall forecasting with a stochastic model

A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities.     

Anthropogenic Eutrophication and Red Tide Outbreak in Lacustrine Systems of the Kashmir Himalaya

Red tide, a recurrent phenomenon has become conspicuous in several Kashmir lake ecosystems since 1991. The responsible organism (Euglena pedunculata), a rare flagellate rediscovered in the Kashmir Himalaya (Khan 1993) caused first and unprecedented red tide outbreak, constituting a maximum of 96% of resident numerical phytoplankton density in Dal Lake. At present, conflicting hypotheses exist on the generation of causal assemblage(s) imparting redness to waters: Jeeji Bai (1991) linked its origin to acid precipitation – a fallout of burning oil‐fields during the Gulf War – whilst Khan (1993) holds local factor(s) responsible. Field/experimental studies support the latter contention that the influx of untreated sewage, in unison with warm temperatures, high levels of PhAR, iron and interruption to hydrological flow‐pattern together with absence/or reduction in grazing activity created conducive environmental milieu for red tide outbreak. Dal Lake “red tide” drifted the bloom‐inoculum to other waters, including Lake Wular, where additional ecological niches were carved out, threatening the aesthetic value and biological diversity of Kashmir lakes. Ecological monitoring indicates frequent seasonal red tide occurrence in Dal Lake (including summer‐autumn event of 1998) which testifies its unabated eutrophication status. Further studies are needed on ecological adaptability and biogeographic distribution of this rare and unique red tide‐causing flagellate.