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A study of heavy metal distribution in Singapore
Author
Chen, Fan
Supervisor
Teo, Khay Chuan
Abstract
This study has been undertaken to determine the general concentration level of some heavy metals in soils and sediments. The objective of this work was to determine the presence of and to measure the extent of heavy metal pollution in Singapore. Speculation of these metals in some selected samples was also conducted.
Collected samples were acid-leached and assisted by microwave digestion. In order to optimize the microwave digestion conditions, orthogonal array experimental design was employed. Five variables, pressure (A), ratio of HCI: HNO3 (B), volume of HF added (C), microwave energy level (D) and digestion time (E), were investigated. Each variable has been assigned for three levels, namely low. medium and high. In the experimental assignment L27313 matrix was used. The concentrations of the twelve elements, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Ti and Zn have been detected by ICP-AES. The best combination setting for the five parameters used in microwave digestion has been settled after the ANOVA analysis. The parameters for the microwave digestion system used in this study were pressure set at 80 psi, power setting at 100%, digestion time over 20 minutes, 1ml HF (49%) to be added to 14 ml 3:1 of HCI (36%) : HNO3(68%) mixed acid.
A total of twenty-six of roadside soil samples, fifty-four field soil samples, twelve sediment samples, thirteen industrial soils and twenty-five residential soil samples were collected stored and analysed over a 20-month period. The lead concentration in roadside soil samples was carefully studied. Its horizontal distribution, vertical distribution along roadside, and correlation with traffic volumes were investigated.
For field, industrial and residential soils and sediments, concentration levels of twelve heavy metals in the selected samples were anaylsed by ICP-AES. The concentration of Ca, Cd, Cr, Cu, Fe, Mn, Mg, Ni, Pb, Ti, Zn were found to be low in the field and residential samples. The results can be helpful for assessing the background or baseline heavy metal distribution in Singapore environment.
In order to evaluate the mobility of some metals, microwave assisted sequential extraction process was adopted for heavy specification study. Eight metals, Ca, Cu, Fe, Mn, Mg, Pb, Ti, and Zn in five fractions were evaluated in unpolluted sediments and polluted industrial soils.
The results present some of the original data on the heavy metal speculation of soil and sediment samples in Singapore. It was found that in sediments. metals are mainly bound to residue lithogeneous fraction. In solid, metal contents found in the first four fractions increased significantly, which indicates that the metals are highly mobile and might pose higher potential risk to human being than that in the sediments.
Collected samples were acid-leached and assisted by microwave digestion. In order to optimize the microwave digestion conditions, orthogonal array experimental design was employed. Five variables, pressure (A), ratio of HCI: HNO3 (B), volume of HF added (C), microwave energy level (D) and digestion time (E), were investigated. Each variable has been assigned for three levels, namely low. medium and high. In the experimental assignment L27313 matrix was used. The concentrations of the twelve elements, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Ti and Zn have been detected by ICP-AES. The best combination setting for the five parameters used in microwave digestion has been settled after the ANOVA analysis. The parameters for the microwave digestion system used in this study were pressure set at 80 psi, power setting at 100%, digestion time over 20 minutes, 1ml HF (49%) to be added to 14 ml 3:1 of HCI (36%) : HNO3(68%) mixed acid.
A total of twenty-six of roadside soil samples, fifty-four field soil samples, twelve sediment samples, thirteen industrial soils and twenty-five residential soil samples were collected stored and analysed over a 20-month period. The lead concentration in roadside soil samples was carefully studied. Its horizontal distribution, vertical distribution along roadside, and correlation with traffic volumes were investigated.
For field, industrial and residential soils and sediments, concentration levels of twelve heavy metals in the selected samples were anaylsed by ICP-AES. The concentration of Ca, Cd, Cr, Cu, Fe, Mn, Mg, Ni, Pb, Ti, Zn were found to be low in the field and residential samples. The results can be helpful for assessing the background or baseline heavy metal distribution in Singapore environment.
In order to evaluate the mobility of some metals, microwave assisted sequential extraction process was adopted for heavy specification study. Eight metals, Ca, Cu, Fe, Mn, Mg, Pb, Ti, and Zn in five fractions were evaluated in unpolluted sediments and polluted industrial soils.
The results present some of the original data on the heavy metal speculation of soil and sediment samples in Singapore. It was found that in sediments. metals are mainly bound to residue lithogeneous fraction. In solid, metal contents found in the first four fractions increased significantly, which indicates that the metals are highly mobile and might pose higher potential risk to human being than that in the sediments.
Date Issued
1999
Call Number
S592.6.H43 Che
Date Submitted
1999