Investigating the mechanism of Uranium removal by zerovalent iron

Zerovalent iron (ZVI) has been proposed as a reactive material in permeable in situ walls for groundwater contaminated by metal pollutants. For such pollutants that interact with corrosion products, the determination of the actual mechanism of their removal is very important to predict their stability in the long term. From a study of the effects of pyrite (FeS2) and manganese nodules (MnO2) on the uranium removal potential of a selected ZVI material, a test methodology (FeS2MnO2 method) is suggested to follow the pathway of contaminant removal by ZVI materials. An interpretation of the removal potential of ZVI for uranium in the presence of both additives corroborates coprecipitation with iron corrosion products as the initial removal mechanism for uranium.Keywords: iron, redox reactions, uranium, water treatmentresearc

Elemental iron (Fe0) for better drinking water in rural areas of developing countries

Many of the reasons behind the anthropogenic contamination problems in rural environments of developing countries lie in changes in the traditional way of life and the ignorance on the toxic potential of introduced manufactured products. A generalization trend exists within the international community suggesting that water in developing countries is of poor quality. However, the water quality is rarely analytically determined. Existing potabilization solutions may be prohibitively expensive for the rural populations. Therefore, efficient and affordable technologies are still needed to ameliorate the water quality. In the recent two decades,elemental iron has shown the capacity to remove all possible contaminants (including viruses) from the groundwater. This paper presents a concept to scale down the conventional iron barrier technology to meet the requirements of small communities and households in rural environments worldwide.researc

Multivariate Statistical Evaluation of Major and Trace Elements in Shatt Al-Arab Sediments, Southern Iraq

River sediments are normally the final pathway of both natural and anthropogenic components derived or produced to the environment. As such, it is important to study these components systematically (i.e. their distribution, levels, and sources). Multivariate statistical techniques such as Principal Component Analysis (PCA) and Agglomerative Hierarchal Cluster Analysis (AHCA) as well as pollution analysis such as Enrichment Factor (EF) analysis were used to analyze the data and identify possible sources of sediment’s components in Shatt Al-Arab at Basra Governorate. The results of PCA and AHCA were compatible, defining four groups of elements; each group has a specific sourcing (a) Mg, Mo, and As show a general enrichment having mean EF values of 8.34, 12.41, and 7.01 respectively, indicating that  Shatt Al-Arab is polluted in these metals, and they are mainly of anthropogenic sources; (b) P, Cl, V, Br, Th, Cu, and Ba have mean EF values of 4.18, 3.52, 1.31, 18.85, 1.67, 2.44, and 0.54 respectively indicating that Shatt Al-Arab is unpolluted in Cl, V, Th, Cu, and Ba; minimally polluted in P, and significantly polluted with Br; (c) Al, Ni, Rb, Nb, Ga, Ti, Y, Mn, and Fe have the lowest mean EF of 1.29, 1.50, 1.07, 0.67, 1.60, 1.67, 0.91, 1.43, and 1.40 respectively; therefore, Shatt Al-Arab can be considered unpolluted in these elements; (d) Pb, Sr, Cr, Zn, and U have mean EF of 0.74, 2.38, 2.78, 2.92, and 0.80 respectively indicating that Shatt Al-Arab is unpolluted in these elements. Hence, AHCA and PCA findings are compatible with EF analysis, strongly confirming the suggested sources of elements. Keywords: Pollution, Sediments, Multivariate Analysis, Pollution Index, Shatt Al-Arab, Basr

Preliminary Assessment of Shatt Al-Arab Riverine Environment, Basra Governorate, Southern Iraq

Environmental investigation has been done for 16 selected sites at Basra Governorate, Southern Iraq (eight sites at Shatt Al-Arab River, four irrigation canals branching from Shatt Al-Arab, three marshlands, and Arabian Gulf). These sites represent distinct land uses: urban, agricultural, marshes, and marine. Water samples have been analyzed for major anions and cations (Na, K, Ca, Mg, Cl, F, Br, NO3, PO4, and SO4) as well as for heavy metals (Li, Be, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Pb, and U) in an effort to make a preliminary assessment for Shatt Al-Arab riverine environment (i.e. contaminants’ distribution, level, and sourcing) and to examine the water suitability for drinking and irrigation purposes. Analyses revealed that Shatt Al-Arab water quality does not comply with drinking or irrigation standards. High population rate, major oil and gas production plants, power generating plants, and agricultural activities at Basra governorate indicate anthropogenic sources of some pollutants as we evidenced in this study. Keywords: Environmental Geochemistry, Water Quality, Pollution, Irrigation, Shatt Al-Arab, Basr

Testing the Suitability of Zerovalent Iron Materials for Reactive Walls

Zerovalent iron (ZVI) has been proposed as reactive material in permeable in situ walls for contaminated groundwater. An economically feasible ZVI-based reactive wall requires cheap but efficient iron materials. From an uranium treatability study and results of iron dissolution in 0.002 M EDTA by five selected ZVI materials, it is shown that current research and field implementation is not based on a rational selection of application-specific iron metal sources. An experimental procedure is proposed which could enable a better material characterization. This procedure consists of mixing ZVI materials and reactive additives, including contaminant releasing materials (CRMs), in long-term batch experiments and characterizing the contaminant concentration over the time.Keywords: iron, redox reactions, uranium water, treatmentresearc

Integrierte Datenauswertung Hydrogeologie

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The effect of gluconic acid secretion by phosphate-solubilizing Pseudomonas putida bacteria on dissolution of pyromorphite Pb_{5}(PO_{4})_{3}Cl and Pb remobilization

The purpose of this study was to investigate the effect of bacterially produced gluconic acid on the dissolution of pyromorphite and Pb remobilization. Pyromorphite Pb_5(PO_4)_3Cl is formed as a product of the phosphate-induced treatment of Pb-contaminated sites. This very stable mineral greatly decreases the bioavailability of Pb. In this study, bacterial and abiotic batch experiments on the dissolution of pyromorphite were carried out. In the microbial experiments, the mineral was dissolved in the presence of the phosphate solubilizing soil bacterium, Pseudomonas putida. The bacterial growth medium was supplemented with glucose, which under natural conditions can be supplied to microbes via symbiosis with plants. P. putida acquired P from pyromorphite and enhanced its dissolution. Elevated Pb concentrations were observed in the suspensions with bacteria. The bacterial secretion of 16.5 mM gluconic acid played a significant role in Pb remobilization; the pH of the solution dropped down from an initial 7.4 to 3.5. In the abiotic experiments, pyromorphite was dissolved at several concentrations of gluconic acid and at an acidic to neutral pH range. Both acidification and formation of stable Ph-gluconate ligands enhanced the dissolution of pyromorphite and caused Pb remobilization

Pb remobilization by bacterially mediated dissolution of pyromorphite Pb_{5}(PO_{4})_{3}Cl in presence of phosphate-solubilizing Pseudomonas putida

Remediation of lead (Pb)-contaminated sites with phosphate amendments is one of the best studied and cost-effective methods for in situ immobilization. In this treatment, a very stable mineral, pyromorphite Pb(5)(PO(4))(3)Cl, is formed. Several studies propose to improve this treatment method with the addition of phosphate-solubilizing bacteria (PSB). The effect of bacteria on solubilization of pyromorphite is unknown. In this study, the effect of the soil microorganisms on the stability of pyromorphite Pb(5)(PO(4))(3)Cl has been investigated in a set of batch solution experiments. The mineral was reacted with Pseudomonas putida, a common soil microorganism. Dissolution of pyromorphite was enhanced by the presence of P. putida, resulting in an elevated Pb concentration in the solution. This occurred even when the bacteria were provided with an additional source of phosphate in the solution. Pyromorphite has been shown to be a potential source of nutrient phosphorus for common soil bacteria. Thus, the use of PSB in remediation treatments of Pb contaminated sites may have adverse long-term impacts on Pb immobilization. Conscious phosphate management is suggested for long-term sustainability of the in situ Pb immobilization by pyromorphite formation

Estimating Groundwater Recharge in the Semiarid Al-Khazir Gomal Basin, North Iraq

The mean annual recharge of Al-Khazir Gomal Basin was estimated as a basis for decision makers regarding the renewability and sustainability of groundwater. For this purpose, two approaches were used: hydrograph analysis and water table fluctuation (WTF). The long-term mean daily stream-flow records of Al-Khazir River (1969–1981) were used to estimate groundwater discharge by base-flow hydrograph separation and displacement recession curve methods. Four base-flow separation methods were used; one is the graphical separation method, and three are automated separation methods included in the web-based Hydrograph Analysis Tool. The annual recharge estimated by WTF was 111.6 mm/y, and the average annual recharge estimated by the four base-flow separation methods was 125.8 mm/y. Estimating recharge by the water table fluctuation method does not incorporate spatial variability contained in the whole watershed, because the specific yield did not represent the entire basin. However, the hydrograph analysis method can give a comprehensive estimation of the net integrated recharge for the entire watershed, which includes different recharge mechanisms. The displacement recession curve method deviates a lot (>30 mm/y) from the other methods, which indicates that this method may not be suitable to apply in such large watersheds