International Journal of Research and Scientific Innovation (IJRSI) | Volume VII, Issue VI, June 2020 | ISSN 2321–2705

Analytical Method for Comparison of Suitable Wet Digestion Methods for Heavy Metal Analysis in Soil around a Cement Industry

Adedeji S. Asher^1*, Kakulu E.Samuel2,  Dauda S. Mary²

¹Chemistry Unit, Mathematics Programme, National Mathematical Centre, P. M. B. 118, Abuja, Nigeria
²Chemistry Department, Faculty of Applied and Natural Sciences, University of Abuja, P. M. B. 117, Abuja, Nigeria
*Correspondence Author

Abstract: -The approach of determination of precision and use of statistical analysis was applied in order to determine the suitable acid mixture for digestion of soil sample for heavy metal analysis in this work. Four different acid mixtures (HNO₃ (60%v/v), HNO₃:H₂SO₄ (2:9), HNO₃/HCl (1:3), HNO₃/HCl/H₂SO₄ (5:1:1),  were compared over nine selected heavy metals (Pb, Cr, Cd, Ni, Zn, Fe, Mn, Co and Cu), and soil near a cement factory were analyzed . The precision for each of the metal  in each of the acid mixture, the recovery  and analysis of variance were applied to determined the most suitable acid mixture for digestion. From  the results it was deduced that the t-calculated for 6 metals  (Cd (0.577), Co (1.165),  Mn (0.380), Cu (0.545),  Ni (1.449) and Zn (1.424) (Cd, Co, Mn, Ni, Cu and Zn) were not significantly different for methods HCl:HNO₃ (3:1) and HNO₃:HCl:H₂SO₄ (5:1:1),  except for Fe, Cr and Pb with significant difference. he heavy metal precision results, shows that method  HNO₃:HCl:H₂SO₄ (5:1:1) , had 7 metals with higher precisions which includes Fe and Cr, while  HCl:HNO₃ (3:1)  had 5 metals with higher precision but does not include Fe and Cr. The statistical analysis revealed that method  HNO₃:HCl:H₂SO₄ (5:1:1) was the most efficient digestion method for the soil heavy metal analysis as it had given a significant high recovery (p < 0.05) for most of the metals under review. Accuracy of the acid mixture selected (HNO₃:HCl:H₂SO₄ (5:1:1)) was evaluated by the analysis of experimental reference material (ERM CC-141) loam soil obtained from the European Commission, Joint Research Centre (JRC), Belgium. The ERM analysis presented good recoveries for most of the metals ranging from 86.4 to 111.0 %.  The determined concentrations were in good agreement with the certified values from the ERM CC-141.

I INTRODUCTION

Metal pollution of the soil including agricultural soils arising from industrial activities, vehicular emissions, and waste disposal sites are well documented (Schuhmacher et al., 2004). Heavy metals are considered to be one of the main sources of pollution in the environment, because of their significant effect on the ecological quality (Sastre et al, 2002).
Heavy metals can be regarded as a group of inorganic chemical, and those most commonly found at contaminated sites are Lead, Chromium , Arsenic, Zinc, Cadmium, Copper, Mercury, and Nickel (Sofani, 2014).