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Title: Analysis and distribution of heavy metals in soil.
Author: Abdulhalim, A. A.
Awarding Body: University College, Cardiff,
Current Institution: Cardiff University
Date of Award: 1979
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Abstract:
Nitric acid and a mixture of nitric, sulphuric and perchloric acids have been used for the total extraction of lead, nickel, cobalt and manganese from soil. The distribution of these metals in both deep peat soil and limestone brown earth soils as a function of depth has been determined. (a) Deep Peat Soil Ignition of this soil showed that it contained 88.5% organic matter. The soil was acidic, pH=3.5. It contained relatively high concentrations of lead and nickel near the surface, their concentrations decreasing with the depth. The profile distribution of manganese was the reverse ofthcdc, lead and nickel, Its concentration increased with depth. No systematic variation of cobalt with depth was found. Column chromatography using a: peat soil showed that the relative mobilities of the four metals in these columns were identical to that found in natural peat soil. The rate of migration was in the order: Mn2+> Co2+> Ni 2+ > Pb2+ Also the rate of migration of these metals increased when the metals were in 1M nitric acid solution rather than water. The large amounts of organic matter in the peat soil suggested that this controlled the mobility of the metals. Fractionation of the soil showed that it contained humin 39%, humic acid 37.9% and fulvic acid 23.1%. The results with humic acid columns showed that the humic acid was responsible for the distribution pattern and the order of metal migration was the same in peat columns. In the case of humin columns all the metals interacted with the humin and then eluted at the same rate, i. e. no separation was achieved.Humic acid solutions were titrated with sodium hydroxide in the absence and presence of known amounts of metal ions. The pH drop upon the addition of these metals is an indicator of the complex formation betw6en the metal ions and humic acid. The reduction of pH in the presence of various metal ions followed the order: for solutions of Pb2+> Ni2+> Co2+> Mn2+ pH less than 8. Ion exchange equilibrium studies were used to characterize the metal-fulvic acid complexes. The order of the relative stabilities of complexes formed between fulvic acid and the four divalent metal ions at pH 3.5 was: Pb2+> Ni 2+ > Co 2+ > Mn 2+ It is clear that humic acid results (both humic columns and potentiometric titration) are in agreement with fulvic acid results which are in turn in agreement with natural peat soil and peat columns. (b) Limestone Brown Earth Soil This soil was alkaline pH=8, and contained a low percentage of organic matter (12.6%) and appreciable amounts of calcium and magnesium carbonates. The distribution of lead, nickel, cobalt and-manganese in this soil showed little variation with depth. The concentration of Pb, Co and Mn decreased with depth, while Ni shows irregular distribution. This was quite different from the peat soil. Column chromatography ersing -: this soil showed that all the metals stayed at the top of the columns, even when the metal solutions which were passed through the columns were prepared in .M analar nitric acid. This is in agreement with the field situation which showed a strong binding between the four metals and the soil. Since this soil contained high amounts ofcarbonate, it would appear that in this case the carbonate is responsible for the distribution and accumulation of the heavy metals. E. P. R. studies showed the presence of Fe3+, Cut+, Mn2+ and V02+ in the humic acid, fulvic acid and their fractions.
Supervisor: Not available Sponsor: Not available
Qualification Name: Doctoral Thesis - University College, Cardiff. Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.446727  DOI: Not available
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