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A talajok állandó pH-értéken történo (pH-sztat) titrálása során felszabadítható aciditás vizsgálatára egy új mérorendszert fejlesztettünk ki, mely azon alapul, hogy számítógép és aktív visszacsatolás révén lúg adagolásával tartjuk állandó értéken a talajszuszpenzió pH-ját. A mérés során az adagolt lúg mennyisége és ido adatpárokból két elsorendu kinetikai függvény összegeként írtuk le a savanyító ionok deszorpciójának idofüggését. A kapott függvény extrapolációjával kiszámítottuk a végtelen idore extrapolált, adott pH-értéknél maximális savanyúság értékeket. A kapott adatokat a klasszikus módszerrel mért vizsgálati eredményekkel összevetve megállapítottuk, hogy az egyszeri extrakció során felszabadítható aciditást igen nagy statisztikai valószínuséggel a gyorsabb deszorpciós folyamat határozza meg, de a teljes folyamat egyensúlyi értékei a Kappen módszerével mért aciditás kétszeresét is elérik. Ennek okát keresve kimutattuk, hogy az aciditás növekedése egyre nagyobb reakció félidot, vagyis egyre lassabb reakciót eredményez, azaz a növekvo aciditással a talajalkotók nehezebben hozzáférheto részén is megkötodnek savanyúságot okozó ionok. Azt találtuk, hogy a talaj humusztartalmának növekedése és kisebb mértékben a leiszapolható rész mennyisége teheto felelossé a deszorpció lassulásáért. A kísérletek eredményei megerosítik, hogy a humuszanyagok makromolekulái, illetve az agyagfrakció belso kötohelyei miatt kialakuló megnövekedett diffúziós úthossz teheto leginkább felelossé a deszorpciós sebesség csökkenéséért. A függvénybol egy órás extrakcióra számított értékeket is összevetettük az egyszeri Ca-acetát extrakció aciditásértékeivel. Azt találtuk, hogy az egy óra alatt az állandó pH-n deszorbeálódó savanyúság 2,5 cmol H+/kg y1-értéknél több savanyúsággal rendelkezo talajok esetében kb. másfélszerese az azonos ido alatt kalcium-acetáttal eltávolítottnak, a különbség a növekvo aciditással egyre növekszik.
A complex investigation was performed for a polluted area using both experi-mental and computer modelling methods. Among the experimental methods the adsorption and desorption isotherms were measured to estimate the concentration dependent equilibrium in the soil-groundwater system. A new calculation method was worked out for determining the transport para-meters from results of laboratory tests. Heavy metal solution was leached through a soil column continuously. The effluent fluidum was collected, and the heavy metal concentration of the collected fractions was measured by atomic absorption spectrophotometer. As the result of the analytic process breakthrough curves were measured in laboratory scale. Due to the applied initial and boundary conditions the transport equation can be solved analytically. Using the Ogata and Banks (1961) solution of the transport equation a new curve fitting method was introduced. After several transformations of the equation a theoretical function was fitted to the measured concentration vs. time and to the concentration vs. effluent volume data. The parameters of the fitted curve could be used as the dispersion and retardation parameters of a transport model. The water chemistry of the system controls the rate of adsorption and desorption of metals to and from sediment. Adsorption removes the metal from the water column and stores the metal in the substrate. Desorption returns the metal to the water column, where recirculation and bioassimilation may occur. Metals are probably desorbed from the soil if the salt concentration of the water increases, and in case of some metals decreases with the redox potential and with pH. Parallel to determining the basic transport parameters of the system using the column study, the maximal equilibrium concentration of chromium-containing compounds with different oxidation states were calculated with the MINTEQ model with two variable functions (pH and redox potential). As a result of the calculations a non-liner relation was established, as at specific points the maximal equilibrium concentration of chromium increases with a high gradient. This means that there are combinations of pH and redox potential values in the case of which chromium has a high solubility. It is advisable to avoid these points in the pH-E h field if we want to stabilize the contaminant. This state is to be reached when the goal is the mobilization of the pollutant to make the soil cleaning process possible. With the introduced calculation method areas on the pH-redox potential field (at high pH and E h values) are found in which the concentration of pollutants may reach a critical value. The introduced calculation method is quick and gives results accurate enough for a pilot test.
For estimating the lime requirement (LR) in some countries it is accepted to use hydrolytic acidity suggested by Kappen, which is based on a single time extraction of hydrogen- and aluminum ion with calcium acetate. More accurate results could be achieved if we measured the total surface acidity (TSA) of soils. For this reason it is an improvement to use a direct measurement method and equipment, which is suitable to estimate the results of long-term processes and TSA, via investigating the kinetic properties of desorption. The method of measurement: A pH electrode is dipped into continuously stirred soil suspension containing background salt (e.g. KCl), and it isconnected to a computer using an amplifier and A/D converter. A computer program has been developed that controls an automatic burette, which adds the base solution into the system if pH is less than the pre-adjusted value (e.g. pH 6.5 or pH 6.8) and stops adding when pH reaches this value. For evaluation, the amount of added base vs. time data series can be used. With increasing time the amount of added base keeps to a constant (asymptotic) value. The program fits an exponential associate function on measured data, and outputs the asymptotic value connected to infinite time, which can be used to calculate LR. Supposing that there are two processes with different rates, in this case the function can be created as the addition of two first order kinetic sub-processes: The faster process that takes place on the outer surfaces features easily removable acidity, and the slower process probably describes processes within the deeper pores. The fitting error of parameters is about 0.3-1%, which means that the TSA value, based on these measured data and method can be estimated with high accuracy. The measurement is fully automated. The evaluation is based on extrapolation, so the precision of results increases with the number of measurement points and the length of measurement time. Depending on the application, a quick measurement with approximate results or a longer measurement with more precise results can be chosen.
Titrálásos módszer talajok redox pufferkapacitásának meghatározására
Titration method for the determination of the redox buffering capacity of soils
A talajok redox pufferképességének mérésére kidolgoztunk egy olyan titrálásos módszert, mellyel a szakirodalomban szereplő redox vizsgálati módszerek hátrányai kiküszöbölhetők.
A mérés során nem az aktuális redoxpotenciált mérjük, hanem oxidáló vagy redukáló szeres titrálással folyamatosan változtatjuk a minta oxidációs állapotát, ezzel gyakorlatilag kiküszöböljük a mintavétel és a mintatárolás jelentős redox állapotot befolyásoló hibáit. A pH és Eh keresztkölcsönhatás kiküszöbölése érdekében párhuzamosan mérjük a rendszer pH-ját és Eh-ját és a szakirodalomból ismert korrekciókat a kiértékelő szoftver automatikusan elvégzi. A teljesen automatizált mérés során pufferkapacitás értéknek a rendszer titrálási átcsapási pontját, vagyis az inflexiós pontot vettük figyelembe, melyet a derivált görbe maximuma alapján keresett meg a program. A módszert számos magyarországi talajmintán alkalmaztuk, eltérő adagolási időkkel, és az eredményekből a redoxtulajdonságokat okozó folyamatok kinetikájára is következtethettünk.
Az oxidációs redox pufferkapacitás vizsgálatoknál azt találtuk, hogy az egyes adagolások között eltelt időt növelve a pufferkapacitás növekedett, míg a reduktív irányban csökkent. Ez a folyamatirány eltérő mechanizmusra utal.
A titration method has been elaborated for the measurement of the redox buffering capacity of the soil, which offsets most of the disadvantages of conventional measuring, because more than just the actual redox potential is detected. During the measurement, the redox state of the samples is changed continuously by titration with reducing or oxidising agents, thus practically eliminating sampling and sample storage errors that influence the redox state. To avoid problems associated with the pH-Eh cross effect, both values are measured in parallel, and corrections are automatically made by the evaluation software. During the automated measurements, the inflexion point of the redox potential curve was taken as the buffering capacity value, calculated as the maximal value of the derivative curve. This method was used for a large number of Hungarian soil samples, with different addition times, and was also suitable for investigating the kinetic properties of soil redox processes. In the case of oxidative redox buffering capacity measurements, it was found that the buffering capacity increased with an increase in the time between additions, while it decreased for reductive measurements. This suggests the existence of different mechanisms for the two processes.
This method was elaborated for determining of the redox buffer ability of soil samples. Its relationship to the redox potential is similar to that of the acidity values to pH. The acidity value depends on the analytical methods. If the applied oxidant does not buffer the redox potential, it can be substituted by acidity, otherwise by hydrolytic acidity. Therefore, it is an extensive quantitative feature of soil, which shows the quantity of oxidants that makes it possible to bring the soil into a given, strongly oxidated state. By use of this method, the errors mentioned in the case of redox potential measurement can be eliminated, and moreover, a characteristic feature of soil, that changes to a far lesser extent as a function of time and conditions, can be measured.
The effects of genotypes, nutrient and water supply on the dry matter production and potassium uptake dynamics of maize (Zea mays L.) were studied on chernozem soil in the Debrecen-Látókép long-term field experiment (Eastern Hungary).According to the experimental results and calculations it can be concluded that — in addition to the previously used and considered soil and plant nutrient contents — the calculation of the plant-extracted nutrient amount (depending on the applied hybrid, NPK nutrient levels and water supply) is suggested to enable the characterization of the growth and nutrient demand dynamics of maize genotypes. This parameter gives information not only about the available nutrient amount at a given sampling time, but about the supply level of plants up to the sampling time as well. For the proper characterization of the mentioned dynamics of maize plants authors suggest to take the following sampling times into consideration: the intensive vegetative growth period, the switch between the vegetative and generative growth phases (silking), and the grain filling phase.
Abstract
In this study, we compile the findings to date on using several cellulose-based materials as adsorbents of potentially toxic elements (PTEs) from wastewater. Furthermore, this review discussed the destiny of PTEs-loaded cellulose-based adsorbents and some sustainable methods for their management, hoping to close the pollution loop.
This paper aims at determining the behavior of thermal water brought to surface and how this might impact reinjection wells and the rock during reinjection. The biggest problem is that reinjection wells are predisposed to choking. We searched for a method to examine this process, including a model for physico-chemical changes in the water—rock interaction. Two different samples of powdered rock (designated α and β) were analyzed using thermal water samples from production and reinjection wells. The pH shows significant differences between the samples from wells where free water treatment was carried out, and those from the aerated thermal waters, as well as for the rock sample. Basically, a decrease in sediment volume can be obtained by increasing the pH. The salt effect was more coherent. Its result was an interesting case of W-shaped graphs from the producing well. On the other hand there is virtually no difference between the samples with acid titration.
Our research team has developed a new well completion and rework technology involving lasers. The system is made up of a high-power laser generator and a custom-designed directional laser drilling head. The laser head is attached to a coiled tubing unit to maximize production and to carry out special downhole tasks. In this phase of the development effort, laser technology is particularly well suited to cost-efficiently drill short laterals from existing wells in a single work phase, drilling through the casing and cement as well as the formation. The technology, which is an extended perforation solution, enables a more intensive interaction with the downhole environment and supports cutting edge subsurface engineering scenarios such as barite removal. Laser-induced heat treatment appears to be a suitable alternative to effectively remove the almost immovable deposits and scales from thermal water-well pipes.
