Applications of the time-naught term in the Cooper and Jacob (1946) equation

The ability to manipulate analytical expressions for aquifer drawdown can provide insights into groundwater flow processes and assist with assessing strengths and weaknesses of aquifer parameter estimation methods. In the Cooper and Jacob (1946) parameter estimation method, the antilog of the horizontal-axis intercept in a plot of drawdown vs. log(time) is referred to as time naught (t(0)), which is used for estimating storativity. This article briefly reviews traditional uses of the time-naught concept and then spends time introducing new insights and applications involving (1) time-naught/distance relationships, including ways to compensate for certain missing data; (2) use of time naught in a simple method providing a quick visual check of which data in a Cooper-Jacob plot are suitable for use in linear regression; (3) application of time naught, as determined for one well, in estimating the later minimum time for which data from a distant well can be used in the Cooper-Jacob method; (4) development of relationships between drawdown and time naught; (5) use of time naught in a simple algebraic equation to estimate drawdown at smaller times than feasible using the Cooper-Jacob method; and (6) employment of time naught and a vertical-axis intercept on a plot of drawdown vs. log(time) for evaluating storativity. This information may be useful to new hydrogeologists or others interested in further developing their analytical well hydraulics skills.     

Use of electrophoresis for transporting nano-iron in porous media

Research has been conducted to evaluate if electrophoresis could transport surface stabilized nanoscale zero-valent iron (nZVI) through fine grained sand with the intent of remediating a contaminant in situ. The experimental procedure involved determining the transport rates of polymer modified nZVI and hematite in fine grained sands under an applied electrical gradient under different physical and chemical conditions. Results indicated transport of polymer modified nZVI and hematite can be accomplished by electrophoresis, with rates found to be much higher than diffusion alone and comparable to those predicted by electrokinetic theory. This study indicates there is potential for this method to deliver polymer modified nZVI into contaminated zones within fine grained sands for the purpose of remediation.     

What is the future fate of estuaries given nutrient over-enrichment,freshwater diversion and low flows?

Freshwater inflow is central to the definition of estuaries and if we lose control of the quantity of freshwater flow or discharge (including seasonal timing) to estuaries, then freshwater water quality has the potential to become a moot issue in estuarine ecosystems (Definition of estuaries: estuaries (aestus = tide) are physico-chemically, geomorphically, and biotically diverse ecosystems. Although numerous definitions of estuaries exist, we prefer the following: an estuary is a partially enclosed coastal water body in which freshwater runoff, often seasonally and episodically pulsed, dilutes salty ocean water and the biotic structure is influenced by dynamic tidal action and associated salinity gradients and reef building organisms and wetlands influence development and evolution of ecological structure and function (see for expanded definition)).     

Isotope-ratio-monitoring gas chromatography-mass spectrometry: methods for isotopic calibration

In trial analyses of a series of n-alkanes, precise determinations of 13C contents were based on isotopic standards introduced by five different techniques and results were compared. Specifically, organic-compound standards were coinjected with the analytes and carried through chromatography and combustion with them; or CO2 was supplied from a conventional inlet and mixed with the analyte in the ion source, or CO2 was supplied from an auxiliary mixing volume and transmitted to the source without interruption of the analyte stream. Additionally, two techniques were investigated in which the analyte stream was diverted and CO2 standards were placed on a near-zero background. All methods provided accurate results. Where applicable, methods not involving interruption of the analyte stream provided the highest performance (sigma = 0.00006 at.% 13C or 0.06% for 250 pmol C as CO2 reaching the ion source), but great care was required. Techniques involving diversion of the analyte stream were immune to interference from coeluting sample components and still provided high precision (0.0001 < or = sigma < or = 0.0002 at.% or 0.1 < or = sigma < or = 0.2%).     

A global experimental system approach of karst springs' hydrographs and chemographs

Investigation techniques for karst flow systems are based mainly on the study of different signals leaving the system caused by natural or induced external influences. Each signal represents one of the systems outputs (e.g., hydraulic, chemical, physical, or isotopic responses) that reflect the characteristics of the entire system. In this paper, we present a method to infer information about the structure of karst systems. It is based on a simultaneous analysis of chemical and hydraulic responses. Beside the classical piston flow at the beginning of a flood pulse, we define a chemically based recession flow phase. During this phase, field data show that the concentration of total dissolved solids can be considered as an exponential function of the logarithm of flow. This relationship allows two parameters to be defined, one of which is dependent on the structure and degree of development of the karst conduit network, the other is dependent mainly on bioclimatic factors. Data collected from seven karst springs are used to support ideas introduced in the paper.