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Browsing Research Articles by Subject "Heavy metals"

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    Lead immobilization in simulated polluted soil by Douglas fir biochar-supported phosphate
    (Elsevier Chemosphere, 2021-12-16) Varco, Jac J.; Dygert, Andrew; Atsar, Felix S.; Solomon, Sabrina; Venkatesh, Rooban; Thirumalai, K.G.; Pittman Jr., Charles U.; Mlsna, Todd
    This study compared the lead (Pb2+) immobilization efficacy of biochar-supported phosphate to conventional in situ heavy metal immobilization methods (with lime, neat biochar and phosphate). The biochar-supported phosphate was obtained by treating Douglas fir biochar (BC) with anhydrous calcium chloride and potassium dihydrogen phosphate. The amount of Pb2+ immobilized was determined by comparing the concentration of ammonium nitrate extractable Pb2+ lead from lead-spiked soil (without amendment) to that of a 30 d incubation with (a) lead-spiked soil plus 5% (wt./wt.) biochar supported-phosphate, (b) lead-spiked soil plus 5% (wt./wt.) untreated Douglas fir biochar, (c) lead-spiked soil plus 5% (w/w) lime and (d) lead-spiked soil plus 5% (wt./wt.) potassium dihydrogen phosphate. The control (lead-spiked soil without amendment) produced the largest quantity (96.08 ± 9.22 mg L− 1 ) of NH4NO3-extractable Pb2+, while lead-spiked soil treated with 5% (wt./wt.) biochar-supported phosphate resulted in the lowest quantity of NH4NO3 extractable Pb2+ (0.3 ± 0.2 mg L− 1 ). The mechanism for immobilization of Pb2+ by BP occurs at pH < 7 through dissolution of hydroxyapatite embedded in BP during modification, followed by precipitation of insoluble Pb10(PO4)6(OH)2. The residual lead fraction in the lead-spiked soil increased by 20.9% following amendment with BP. These results indicate that biocharsupported phosphate is a candidate to reduce lead mobility (bioavailability) in polluted soil. This amendment may lower Pb2+ uptake into plants while minimizing the potential for water contamination due to Pb2+mobility.
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    Speciation of heavy metals in water from the Uganda side of Lake Victoria
    (Tailor and Francis, 2010-02) MBABAZI, JOLOCAM; TWINOMUHWEZI, H.; WASSWA, J.; NTALE, M.; MULONGO, G.; KWETEGYEKA, J.; SCHR DER, K.H.
    Different forms of copper Cu, zinc Zn, lead Pb and cadmium Cd in water from the Uganda side of Lake Victoria (25°C, pH 6.75–7.18), the second largest inland freshwater lake in the world, have been studied using ion-exchange, dialysis and atomic absorption spectrophotometry. The results indicate that heavy metals Cu, Zn, Pb and Cd are present mainly in the cationic form (80–83%). Small quantities of anionic (13–22%), non-ionic, dialyzable (4–8%), and non-ionic, non-dialyzable (< 1.3–4.4%) forms were also detected for all metals except Cd. The corresponding concentrations lay in the ranges: cationic, 0.06–0.99; anionic, < 0.001–0.25; non-ionic, dialyzable, < 0.001–0.08; non-ionic, non-dialyzable, < 0.001–0.06 µg ml−1 . The existence of the metals in non-ionic and nondialyzable forms is attributable to metal associations with high relative molecular mass (RMM) organic matters.