The southern Sindh province of Pakistan adjoins the Arabian Sea coast where drinking water quality is deteriorating due to dumping of industrial and urban waste and use of agrochemicals and yet has limited fresh water resources. The study assessed the drinking water quality of canal, shallow pumps, dug wells, and water supply schemes from the administrative districts of Thatta, Badin, and Thar by measuring physical, chemical, and biological (total coliform) quality parameters. All four water bodies (dug wells, shallow pumps canal water, and water supply schemes) exceeded WHO MPL for turbidity (24%, 28%, 96%, 69%), coliform (96%, 77%, 92%, 81%), and electrical conductivity (100%, 99%, 44%, 63%), respectively. However, the turbidity was lower in underground water, i.e., 24% and 28% in dug wells and shallow pumps as compared to open water, i.e., 96% and 69% in canal and water supply schemes, respectively. In dug wells and shallow pumps, limits for TDS, alkalinity, hardness, and sodium exceeded, respectively, by 63% and 33%; 59% and 70%, 40% and 27%, and 78% and 26%. Sodium was major problem in dug wells and shallow pumps of district Thar and considerable percent in shallow pumps of Badin. Iron was major problem in all water bodies of district Badin ranging from 50% to 69% and to some extent in open waters of Thatta. Other parameters as pH, copper, manganese, zinc, and phosphorus were within standard permissible limits of World Health Organization. Some common diseases found in the study area were gastroenteritis, diarrhea and vomiting, kidney, and skin problems.
Natural and chemically enhanced phytoextraction potentials of maize (Zea mays L.) and sesbania (Sesbania aculeata Willd.) were explored by growing them on two soils contaminated with heavy metals. The soils, Gujranwala (fine, loamy, mixed, hyperthermic Udic Haplustalf) and Pacca (fine, mixed, hyperthermic Ustollic Camborthid), were amended with varying amounts of ethylenediaminetetraacetic acid (EDTA) chelating agent, at 0, 1.25, 2.5, and 5.0 mM kg(-1) soil to enhance metal solubility. The EDTA was applied in two split applications at 46 and 60 days after sowing (DAS). The plants were harvested at 75 DAS. Addition of EDTA significantly increased the lead (Pb) and cadmium (Cd) concentrations in roots and shoots, uptake, bioconcentration factor, and phytoextraction rate over the control. Furthermore, addition of EDTA also significantly increased the soluble fractions of Pb and Cd in soil over the controls; the maximum increase of Pb and Cd was 13.1-fold and 3.1-fold, respectively, with addition of 5.0 mM EDTA kg(-1)soil. Similarly, the maximum Pb and Cd root and shoot concentrations, translocation, bioconcentration, and phytoextraction efficiency were observed at 5.0 mM EDTA kg(-1) soil. The results suggest that both crops can successfully be used for phytoremediation of metal-contaminated calcareous soils.
Laboratory batch and greenhouse pot experiments were conducted to determine the extraction efficiency of ethylenediaminetetraacetic acid (EDTA) for solubilizing lead (Pb) and cadmium (Cd) and to explore the natural and chemically induced Pb and Cd phytoextraction efficiencies of spinach and mustard after EDTA application. The EDTA was applied at 0, 1.25, 2.5, and 5.0 mM kg −1 soil in three replicates. Addition of EDTA increased significantly the soluble fraction Pb and Cd over the control and maximum increases for and were observed with the addition of 5.0 mM EDTA kg −1 in Gujranwala and Pacca soils, respectively. Similarly, addition of EDTA increased significantly the Pb and Cd concentrations in the plant shoots, soil solution, bioconcentration factor, and phytoextraction rate. Mustard exhibited better results than spinach when extracting Pb and Cd from both contaminated soils.
Iron (Fe) oxides control plant nutrient and contaminant redistribution in soils, but their phase identification and quantification is complicated by their low concentration and poor crystallinity and by the high detection limits of the current techniques. Cyclic voltammetry using a carbon paste electroactive electrode was tested to characterize soil iron oxides. Twenty-eight clays (,2 mm) from eight soils varying in parent material and pedological development were separated, and Fe phases were determined by x-ray diffraction (XRD) before and after preconcentration treatment with 5M sodium hydroxide (NaOH). Morphology of Fe phases was determined by electron microscopy, and total extractable Fe phases in soil were determined by citrate bicarbonate dithionite. The preconcentration treatment was effective in phase identification. Goethite and hematite were found, depending upon origin of the soil clays. The samples with less than 2% hematite needed preconcentration. Three percent goethite in clays was on the edge of the XRD limit. The electrochemical signals of re-oxidation of Fe 2+ released from reductive dissolution of free Fe oxides was quantitatively related to their content in the sample. Voltammetry effectively quantified goethite and hematite or both in a mixture with detection limit as low as 0.025 mg 100 21 mg in clay. The technique can be used for quick estimate of low content of Fe oxides in clays and can be adapted for free Fe estimation in soils.
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