Hydrogeologie des Kabul-Beckens (Afghanistan), Teil I: Grundwasserleiter und Hydrologie

Shallow groundwater currently represents the main source for water supply in Kabul. Detailed information on the hydrogeology of the Kabul basin is therefore needed to improve the supply situation and to develop sustainable concepts of groundwater use. The basin is situated at the intersection of three major fault systems and comprises three major aquifers, all consisting of coarse sandy to gravely material originating from the surrounding mountains. The aquifers were deposited by several rivers draining the basin. Marl is the basal layer of the aquifers. Usually the aquifers are covered by loess loams which are an important feature in groundwater protection. The coarse aquifer material has high permeability. Deeper parts are affected by cementation of pore spaces, resulting in formation of semi-diagenetic conglomerates which decrease well yields. The main groundwater recharge occurs after the snowmelt from direct exfiltration from the rivers and from foothill infiltration. The high withdrawals of the last few years and a steadily rising population have led to a strong overexploitation of the groundwater resource as indicated by falling groundwater levels and deteriorating groundwater quality.     

Sorption kinetics of Fe(II), Zn(II), Co(II), Ni(II), Cd(II), and Fe(II)/Me(II) onto hematite

The reactions of Fe(II) and other divalent metal ions including Zn, Co, Ni, and Cd on hematite were studied in single and competitive binary systems with high sorbate/sorbent ratios in 10 mM PIPES (pH 6.8) solution under strict anoxic conditions. Adsorbed Me(II) was defined as extractable by 0.5 N HCl within 20 h, and fixed Me(II) was defined as the additional amount that was extracted by 3.0 N HCl within 7 days. Binary systems contained Fe(II) plus a second metal ion. The extent of uptake of divalent metal ions by hematite was in order of Fe> or =Zn>Co> or =Ni>Cd. For all metals tested, there was an instantaneous adsorption followed by a relatively slow stage that continued for the next 1-5 days. This sequence occurred in both single and binary systems, and could have been due to a variety of sorption site types or due to slow conversion from outer- to inner-sphere surface complexes due to increasing surface charge. Sorption competition was observed between Fe(II) and the other metal ions. The displacement of Fe(II) by Me(II) was in order of Ni approximately Zn>Cd, and the displacement of Me(II) by Fe(II) was in order of Cd>Zn approximately Ni>Co. Fixed Fe(II) was in order of Fe+Co (20%)>Fe+Cd (6%)>Fe approximately Zn (4%)>Fe approximately Ni (4%) after 30 days. There was no fixation for the other metals in single or binary systems.     

Sorption of Zn(II), Pb(II), and Co(II) using natural sorbents: equilibrium and kinetic studies

Natural Jordanian sorbent (consisting of primary minerals, i.e., quartz and aluminosilicates and secondary minerals, i.e., calcite and dolomite) was shown to be effective for removing Zn(II), Pb(II) and Co(II) from aqueous solution. The major mineral constitutions of the sorbent are calcite and quartz. Dolomite was present as minor mineral and palygorskite was present as trace mineral. The sorbent has microporous structure with a modest surface area of 14.4 m(2)g(-1). pH(zpc) (pH of zero point charge) of the sorbent was estimated by alkaline-titration methods and a value of 9.5 was obtained. The sorption capacities of the metals were: 2.860, 0.320, 0.076 mmol cation g(-1) for Zn(II), Pb(II) and Co(II) at pH 6.5, 4.5 and 7.0, respectively. The shape of the experimental isotherm of Zn(II) was of a "L2" type, while that of Pb(II) and Co(II) was of a "L1" type according to Giles classification for isotherms. Sorption data of metals were described by Langmuir and Freundlich models over the entire concentration range. It was found that the mechanism of metal sorption was mainly due to precipitation of metal carbonate complexes. The overall sorption capacity decreased after acid treatment, as this decreased the extent of precipitation on calcite and dolomite. The effect of Zn(II) ions concentration on sorption kinetics was investigated. Kinetic data were accurately fitted to pseudo-first order and external diffusion models which indicated that sorption of Zn(II) occurred on the exterior surface of the sorbent and the contribution of internal diffusion mechanism was insignificant. Furthermore, the sorption rate of Zn(II) was found to be slow, where only 10-20% of the maximum capacity was utilized in the first 30 min of interaction.     

Zur Berechnung der Rißbreite. Teil 2: Anwendungen des Rechenmodells

About the Calculation of Crack Width. Part 2: Applications of the Mathematical Modell The limitation of crack width that DIN 1045‐1 required are possible through succesive corrections of reinforcement area or/and their diameter. At part 1 a general procedure which can transform these iterative proofs to the design of cross sections – subjected to axial tension respectively bending with axial load – was reported. Part 2 shows the applications of the general procedure for the calculating of crack width – checks, respectively into dimensioning transformated checks and represents design diagrams and tables for usual practical cases.     

Removal of Cu(II), Ni(II), and Co(II) from aqueous solutions using layered double hydroxide intercalated with EDTA

A sample of a layered double hydroxide intercalated by EDTA has been synthesized and its chemical formula [Zn₄Al₂(OH)₁₂](EDTA) · 8H₂O was determined. The possibility of applying such sorbent for the extraction of Cu(II), Ni(II), and Co(II) from aqueous solutions was investigated. Comparative investigation of the sorption capacity of carbonate and chelate forms of layered double hydroxides was performed. It is shown that the degree of extraction of metals on sorbent [Zn₄Al₂(OH)₁₂](EDTA) · 8H₂O completely correlates with the stability of complex compounds of these metals in the solution.     

The sorption of copper(II), manganese(II), zinc(II) and arsenic(III) onto human hair,and their desorption

Human hair has been studied in relation to sorption from aqueous solutions of Cu²⁺, Mn²⁺, Zn²⁺ and AsO₃^3?. At an equilibrium concentration of 0.3 μg ml^?1 the sorptions are relatively low for Mn (1.1 μg g^?1) and As (0.1 μg g^?1), and higher for Zn (10 μg g^?1) and Cu (35 μg g^?1). But only in the case of copper is the sorption significant relative to the indigenous levels of the elements in the hair. The greater sorption of Cu²⁺ may be correlated with better binding to the hair fibre, probably both electrostatically and to the sulphur in the keratin. There appears to be at least three modes of attachment, or three mechanisms of attachment of Cu²⁺ to the hair. An inter-element effect was observed, where Cu²⁺ severely inhibits the sorption of Zn²⁺ and Mn²⁺. Also the total sorption of Cu²⁺ is reduced on zinc or manganese-treated hair. Some comments are made regarding the results and the problems of exogenous contamination of human hair.