Bioleaching of Heavy Metal Polluted Sediment: Influence of Temperature and Oxygen (Part 1)

The experiment was conducted to appraise the level of Cr, Pb, Cd, Ni, Zn, Cu, Fe and Mn contamination in 15 sediment samples of upstream of Turag river, at the Department of Agricultural Chemistry, Bangladesh Agricultural University, Mymensingh. The concentrations of Cr, Pb, Cd, Ni, Zn, Cu, Fe and Mn were 178.0, 18.3, 0.8, 155.4, 194.1, 54.8, 13679 and 5501.6 µg g-1 and the pH and EC ranged from 2.01-7.85 and 391-3910µS cm-1, respectively. Heavy metal concentrations were compared with geochemical background and standard values of previous report on the Turag and other rivers in Bangladesh. The average concentrations of Cr, Zn and Ni in sediments of the Turag are almost twice of the geochemical background i.e. average worldwide shale standard and continental upper crust. Cadmium is about three times higher than the geochemical background values. Chromium and Ni concentration exceeded the severe effect level (SEL), where as Cd, Zn and Cu exceeded toxicity reference values (TRV). The average Enrichment Factors (EFc) for Mn, Cd, Cr and Ni reflected moderate to extremely contaminated pollution. The pollution load index (PLI) varied from 1.65 to 3.21. The geoaccumulation index (Igeo) for Mn of 11 locations and Cd for a single location were greater than 2.0, and exhibited moderately to strongly polluted sediment quality. The Igeo for Zn in two locations and Ni in one location were greater than 1.0, indicated moderately polluted sediment quality. Sediment pollution load signaled alarming condition for city dwellers and aquatic ecosystem of the Turag river. Pollution sources to be sealed immediately and continuous monitoring on pollution prevention and cleanup operation is suggested.Progressive Agriculture 27 (2): 78-85, 2016

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pH Effect on Heavy Metal Release from a Polluted Sediment

Journal of Chemistry ◽

10.1155/2018/7597640 ◽

2018 ◽

Vol 2018 ◽

pp. 1-7 ◽

Cited By ~ 12

Author(s):

Yanhao Zhang ◽

Haohan Zhang ◽

Zhibin Zhang ◽

Chengying Liu ◽

Cuizhen Sun ◽

...

Keyword(s):

Heavy Metal ◽

Sequential Extraction ◽

River Water ◽

Ph Effect ◽

Residual Fraction ◽

Leaching Test ◽

Metal Release ◽

Polluted Sediment ◽

Leaching Solution ◽

Heavy Metal Release

The performance of Cd, Ni, and Cu release from river sediment at different pH was investigated by a leaching test using deionised water and river water as leachants. Visual MINTEQ geochemical software was used to model the experimental results to predict heavy metal release from sediments. The distribution and speciation of heavy metals in the sediments after leaching test were analyzed by Tessier sequential extraction. Leaching test results showed that the release amounts of Cd, Ni, and Cu are in the range of 10.2–27.3 mg·kg−1, 80.5–140.1 mg·kg−1, and 6.1–30.8 mg·kg−1, respectively, with deionised water as leachant at different pH. As far as the river water was used as the leaching solution in the test, the results show similar metal leaching contents and tendencies to that of the deionised water as leaching solution. The results of Tessier sequential extraction indicate that Cd of residual fraction easily forms obvious precipitate under the acidic condition, especially in the range of pH 0–4 with the residual of Cd over 50% of the total Cd in the sediment. The exchangeable content of Ni decreases with the increase of pH under the range of 0–5. The Fe-Mn oxide fraction of Cu in the sediments changes significantly from pH 0 to pH 9. Based on the effect of pH on the leaching of Cd, Ni, and Cu from the polluted sediment in the tests, more accurate information could be obtained to assess the risk related to metal release from sediments once it is exposed to the changed acid/alkali water conditions.

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