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131.
A fluorescent labelling method is presented as a new tool for the investigation of organic particle transport and biogenic carbon cycling processes in sandy littoral interstices at Lake Tegel, Berlin, Germany. Passive particle transport through the pore system was studied by in situ exposition of 2.4 μm monodisperse polymeric resin microparticles stained with 7-amino-4-methylcoumarin (AMC). Uptake of fluorescein-5-isothiocyanate (FITC)-labelled Chlorella vulgaris and fine particulate organic matter (FPOM) by the interstitial fauna was investigated in laboratory and field experiments. The major portion (>85%) of the FITC-labelled particles added to sediment cores was recovered from the topmost centimetre of sediment during the study period of 14 days. Uptake of FITC-labelled FPOM was observed in several benthic groups, e.g. chironomids, microcrustaceans, oligochaetes and tardigrads, whereas C. vulgaris was ingested by oligochaetes only. There is evidence to suggest that both are suitable materials for investigating the fragmentation and ingestion of organic material by herbivorous and detritivorous fauna. Field experiments with inert microparticles and FITC-labelled FPOM (<1 mm) prepared from dried alder leaves were carried out in plexiglass tubes as in situ whole core technique. Within the investigation period of two weeks, the transport of FPOM was restricted to the topmost 2–3 cm of sediment in conjunction with a distinct fragmentation to finer size classes with respect to increasing sediment depth. Vertical FPOM transport was hindered by a high interstitial concentration of natural POM and an intensive settlement of the interstices by algae (mainly epispammic algae, 65–96% of algae cell number) and extra-cellular polymeric substances (EPS), which formed a dense three-dimensional structure. 相似文献
132.
Contribution of magnetic resonance sounding to aquifer characterization and recharge estimate in semiarid Niger 总被引:4,自引:0,他引:4
J.M. Vouillamoz G. Favreau S. Massuel M. Boucher Y. Nazoumou A. Legchenko 《Journal of Applied Geophysics》2008,64(3-4):99-108
To improve the knowledge of the regionally important Continental Terminal 3 (CT3) aquifer in south-western Niger, fifteen magnetic resonance soundings (MRS) were carried out in December 2005 in the vicinity of wells and boreholes. The output MRS geophysical parameters, i.e. water content and decay constants versus depth, were compared to hydrogeological characteristics, i.e. water table depth, total porosity, specific yield and transmissivity estimated from direct measurements, pumping tests and transient groundwater modelling. The MRS-determined parameters were then used to estimate the rates of groundwater recharge.Contained in poorly consolidated Tertiary sandstones, the CT3 aquifer's water table has continuously risen by 4 m in total over the past four decades. Additionally, a significant portion of this increase has occurred in the past decade alone, with an annual rise now ranging between 0.1 and 0.3 m depending on the monitored well. Increase in groundwater recharge due to land clearance and deforestation explains this situation. According to previous estimations, the pre-clearing recharge ranged from 1 to 5 mm per year in 1950–60 s, while more recent recharge rates (1990s–2000s) range from 20 to 50 mm per year. These recharge values are directly affected by estimated aquifer specific yield value, while the spatial variation of rates of water table rise can be attributed to large scale hydrodynamic heterogeneities in the aquifer. However, few field measurements were available to confirm these assumptions.The main results of this study are: (1) The water table depth and aquifer transmissivity are estimated from MRS output parameters with an average accuracy of ± 10% and ± 9% respectively. (2) The MRS-determined water content is linked to both the total porosity and the specific yield of the aquifer, but no quantitative formulation can be proposed as yet. (3) Using the average MRS-determined water content over the investigated area, i.e. 13%, the groundwater recharge rates can be estimated to be ~ 2 mm per year in the 1950–1960s (pre-clearing period), and ~ 23 mm per year for the last decade. (4) The variations in specific yield and transmissivity cannot explain by themselves the spatial variability of the rise of the water table. (5) The ranges in transmissivity and water content obtained from MRS are more realistic than the groundwater modelling outputs. Therefore, MRS could be used to better constrain the aquifer parameters in groundwater modelling with a dense site network.Finally, this work illustrates how MRS can successfully improve characterisation and transient multi-year groundwater balance of commonly found sedimentary aquifers, particularly when integrated with well observations and pumping tests. 相似文献
133.
Michael B. Turner Shane J. Cronin Ian E. Smith Robert B. Stewart Vince E. Neall 《Journal of Volcanology and Geothermal Research》2008
Eruption episodes, where a series of eruption events are generically related, can include the eruption of a wide spectrum of volcanic activity over decadal periods. This paper concentrates on the opening phases of an eruption episode which occurred approximately 1800 yrs BP from Mt Taranaki, New Zealand. These events spanned the eruption of differing bulk compositions and styles from two distinct vent locations; an andesitic sub-plinian eruption from the summit vent and a scoria cone-building eruption of basaltic magma from a satellite vent. Compositional profiles and zoning textures of plagioclase, amphibole and clinopyroxene phenocrysts from the opening andesitic event show evidence of magma mixing and subsequent crystallisation just prior to the initiation of the eruption episode. Titanomagnetite grain morphology and Ti variation suggest that the magma mixing event occurred within a few days to weeks before the eruption acting as a trigger for it. We present a magmatic model which is constrained by the petrological observations and eruptions of the episode. In this model magma differentiation at depth causes its rise and recharging of a mid-crustal magma storage area at 5–7 km. Although the recharging magma differed slightly in oxygen fugacity and temperature, it was compositionally and physically similar enough to the residing andesitic magma to allow efficient mixing. The petrological characteristics described here can be readily observed and enable identification of mixing events in other recent eruption episodes. 相似文献
134.
干旱内陆河流域地表水地下水联合调度研究进展 总被引:3,自引:0,他引:3
地表水-地下水联合调度是解决干旱内陆河流域水资源短缺的一个有效途径,对干旱区水资源优化配置具有重要意义.以地表水地下水联合调度内涵为基础.分析了干旱内陆河地表水-地下水联合调度模式的国内外研究现状.对地表水地下水联合调度的研究方法进行了评价并指出存在的不足之处,展望了地表水与地下水联合调度的研究趋势.指出在未来地表水-地下水联合调度中应加强与气象学、生态学等多学科交叉研究.探讨内陆河水资源高效利用模式和基于生态健康和环境发展的内陆河环境需水定值方法与阈值.开发内陆河地表水地下水联合调度信息系统和管理模式.指出综合水循环组成部分的集成模型是地表水-地下水联合调度模型发展的必然趋势. 相似文献
135.
应用 D、18O同位素峰值位移法求解大气降水入渗补给量 总被引:1,自引:0,他引:1
采用D、18O同位素峰值位移法求出研究区大气降水入渗补给量。通过野外地中渗透计法和降水入渗系数法对同位素法计算结果检验,发现D、18O同位素法计算结果具有较高精度,同时验证了在研究区用D、18O同位素方法求大气降水入渗补给量是可行和可靠的。用该方法求解大气降水入渗补给量具有方便快捷、经济省时的优点,在湿润、半湿润地区大气降水补给研究方面,具有很大的应用潜力和重要的应用价值。 相似文献
136.
应用匀坡及加坡原理,推导出了单井(孔)稳定流承压完整井渗透系数的计算公式,该公式已考虑到无效降深对渗透系数计算的影响,同时在计算过程中充分利用了水位恢复资料,而水位恢复的过程也排除了一些干扰因素的影响,因此,参数计算结果应更接近实际。 相似文献
137.
Due to the rapid expansion of the Sudanese capital city far away from its three Niles, it has become a necessity to estimate
the sustainability of the groundwater resources in this arid area. The purpose of this study – based on the stable-isotopic
composition of groundwater – is to identify the sources of recharge and their relative contribution. The results show that
groundwater infiltrated from the Niles under the present prevailing arid climate, with greater contribution from the White
Nile compared to the Blue Nile, occupies an extension of 12 km from the Niles within the two main aquifers. Paleogroundwater
of meteoric origin, infiltrated in the cooler pluvial earlier Holocene, occupies the outer zones beyond the Niles' effect.
A rational utilization policy is recommended to preserve the finite groundwater resources.
Received: 27 August 1998 · Accepted: 2 March 1999 相似文献
138.
中国北方第四系地下水同位素分层及其指示意义 总被引:11,自引:0,他引:11
中国北方第四系地下水中的D, 18O, 3H和14C含量存在明显的分层现象, 这种现象与末次冰期以来的古气候变化有着较好的对应性, 反映了全新世和末次冰期气候条件的差别以及地下水不同的形成机制.深层地下水为晚更新世末次冰期时期形成, 其δ(D) 和δ(18O) 值与全新世补给形成的浅层地下水相比, 分别贫4× 10-3~ 16× 10-3和1× 10-3~ 2× 10-3, 说明末次冰期时期年均气温较低.古地下水中D和18O的大陆梯度与全新世以来地下水中的梯度基本相同, 说明在过去30000a来尽管气温发生变化, 但中国北方大陆的大气循环模式没有发生实质性的改变.地下水同位素分层现象反映了3种不同的补给机制及参与现代水循环程度.这些信息对大陆尺度上的水循环研究和地下水的可持续开发利用有着重要的意义. 相似文献
139.
利津县城区的地热资源主要赋存于新生代新近纪和古近纪碎屑沉积岩中,热储类型为层状孔隙-裂隙型热储,地热资源类型属热传导型。新近纪馆陶组热储层组与古近纪东营组热储层组是主要的热储层。该文在论述利津县地热地质条件的基础上,对地热开发的经济、社会、环境效益及开发利用前景进行了分析,对地热开发中的尾水排放和回灌问题进行了探讨,最后提出了地热资源开发与管理方面的建议。 相似文献
140.
北京市永定河冲洪积扇中上部,具备建设地下水库的基本条件。本文在确定永定河地下水库水资源人工补给方式的基础上,分析了各方式的入渗能力,提出了地下水库的人工补给方案,利用地下水数值模拟的预测结果和有效储水率计算公式,首次研究了地下水库的储水能力,分析了永定河地下水库的水资源补给效果。结果表明,永定河地下水库水资源人工补给能力最大可达18.93m^3/s,回灌地表水2.42×108m^3的情况下地下水位最大回升32m,地下水储存量增加2.09×108m^3,回灌后1年和5年的有效蓄水率分别为78.6%和46.8%,北京永定河地下水库具有较好水资源回灌能力、储存能力,地下水人工调蓄能够起到明显的效果。 相似文献