100,386 research outputs found
Detection of Naphthalene Sulfonates from Highly Saline Brines with High-Performance Liquid Chromatography in Conjunction with Fluorescence Detection and Solid-Phase Extraction
No full textGerman Federal Ministry of Environment (BMU) [FKZ: 0327579
Exploring the influence of operational parameters on the reactivity of elemental iron materials.
No full textIn an attempt to characterize material intrinsic reactivity, iron dissolution from elemental iron materials (Fe0) was investigated under various experimental conditions in batch tests. Dissolution experiments were performed in a dilute solution of ethylenediaminetetraacetate (Na2-EDTA – 2 mM). The dissolution kinetics of 18 Fe0 materials were investigated. The effects of individual operational parameters were assessed using selected materials. The effects of available reactive sites [Fe0 particle size (≤2.0 mm) and metal loading (2–64 g L−1)], mixing type (air bubbling, shaking), shaking intensity (0–250 min−1), and Fe0 pre-treatment (ascorbate, HCl and EDTA washing) were investigated. The data were analysed using the initial dissolution rate (kEDTA). The results show increased iron dissolution with increasing reactive sites (decreasing particle size or increasing metal loading), and increasing mixing speed. Air bubbling and material pre-treatment also lead to increased iron dissolution. The main output of this work is that available results are hardly comparable as they were achieved under very different experimental conditions. A unified experimental procedure for the investigation of processes in Fe0/H2O systems is suitable. Alternatively, a parameter (τEDTA) is introduced which could routinely used to characterize Fe0 reactivity under given experimental conditions
INTEGRATED APPROACH FOR INNOVATIVE MONITORING STRATEGIES OF RESERVOIRS AND LAKES
No full textAn innovative strategy significantly increasing data density by introducing a flexible, problem-orientated, and cost-effective water quality monitoring approach is presented. Most current monitoring strategies produce water quality data based on fixed stations conducted on fixed dates throughout a defined period of time and, thus, often give a biased and insufficient picture of the water quality. Establishing a refined picture of water quality while not increasing monitoring costs clearly needs a change in monitoring strategy. The complexity of social-economic needs, environmental aspects and evolving legislative guideline values makes the design of a suitable innovative strategy challenging. The combination of investigative and risk-based monitoring with real-time monitoring of proxies (e.g., electrical conductivity (EC)) is a vital asset within this here proposed innovative strategy. For the former, organic micropollutants (e.g., pesticides, pharmaceuticals) are suggested in this article to be a powerful tool for source apportionment as they allow to determine and quantify the cause and impact of water quality impairments. This strategy was tested in a field campaign in which an area of elevated EC was investigated at Lake Garda, Italy. A radio-controlled boat was used for EC mapping and sampling. As no chemical indicators for significant anthropogenic sources could be detected, the elevated EC could be assigned to natural sources
Reducing the ambiguity of karst aquifer models by pattern matching of flow and transport on catchment scale
No full textAssessing the hydraulic parameters of karst aquifers is a challenge due to
their high degree of heterogeneity. The unknown parameter field generally
leads to a high ambiguity for flow and transport calibration in numerical
models of karst aquifers. In this study, a distributed numerical model was
built for the simulation of groundwater flow and solute transport in a
highly heterogeneous karst aquifer in south-western Germany. Therefore, an
interface for the simulation of solute transport in one-dimensional pipes
was implemented into the software COMSOL Multiphysics® and
coupled to the three-dimensional solute transport interface for continuum
domains. For reducing model ambiguity, the simulation was matched for
steady-state conditions to the hydraulic head distribution in the model
area, the spring discharge of several springs and the transport velocities
of two tracer tests. Furthermore, other measured parameters such as the
hydraulic conductivity of the fissured matrix and the maximal karst conduit
volume were available for model calibration. Parameter studies were
performed for several karst conduit geometries to analyse the influence of
the respective geometric and hydraulic parameters and develop a calibration
approach in a large-scale heterogeneous karst system.
Results show that it is possible not only to derive a consistent flow and
transport model for a 150 km2 karst area but also to combine the use
of groundwater flow and transport parameters thereby greatly reducing model
ambiguity. The approach provides basic information about the conduit network
not accessible for direct geometric measurements. The conduit network volume
for the main karst spring in the study area could be narrowed down to
approximately 100 000 m3
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Interactive comment on “Influence of aquifer heterogeneity on karst hydraulics and catchment delineation employing distributive modeling approaches”
No full textDue to their heterogeneous nature, karst aquifers pose a major challenge for
hydrogeological investigations. Important procedures like the delineation of
catchment areas for springs are hindered by the unknown locations and
hydraulic properties of highly conductive karstic zones.
In this work numerical modeling was employed as a tool in delineating
catchment areas of several springs within a karst area in southwestern
Germany. For this purpose, different distributive modeling approaches were
implemented in the finite element simulation software Comsol
Multiphysics®. The investigation focuses on the question to
which degree the effect of karstification has to be taken into account for
accurately simulating the hydraulic head distribution and the observed
spring discharges.
The results reveal that the representation of heterogeneities has a large
influence on the delineation of the catchment areas. Not only the location
of highly conductive elements but also their geometries play a major role
for the resulting hydraulic head distribution and thus for catchment area
delineation. The size distribution of the karst conduits derived from the
numerical models agrees with knowledge from karst genesis. It was thus shown
that numerical modeling is a useful tool for catchment delineation in karst
aquifers based on results from different field observations
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