Assessment of soil pH and heavy metal concentrations in agricultural land impacted with Medical Waste Incinerator (MWI) Flue Ash (FA) in Abia State, Nigeria

Abstract

This study focused on the effect of heavy metals being introduced into soils through medical waste incinerator flue ash by collecting soil samples at different depths and distances to determine soil pH, Cu, Zn, Cr, Cd, Pb and Mn contents using standard methods and multivariate tools for data summary. Mean soil pH values ranged: 5.2 – 6.2 > 4.8 of control due to flue ash as a liming agent and farming practices respectively, with low pH that encourages mobility and absorption of heavy metals in ecosystems. Heavy metals in incinerator site(mgkg^-1) ranged:2.00105 ± 0.00-2.09050 ±0.00; 4.0011±0.00-12.3250±0.00; 6.0405±0.01-8.0150±0.01; 4.0150±0.00-7.0805±0.07; 0.2100±0.01-1.0950±0.01; 0.00±0.00-0.001100±0.00; 0.0305±0.01-0.1150±0.00 for Cu, Zn , Mn, Cr, Cd and Pb respectively, with control 0.55 ± 0.01-1.25 ± 0.01;1.25 ± 0.01-1.45 ± 0.01; 13.15 ± 0.07-14.15 ± 0.07; 0.02 ± 0.01; 0.00 ± 0.01-0.03 ± 0.01; .54 ±0.01-.54 ± 0.01 for Cu, Zn , Mn, Cr, Cd and Pb respectively .Metals were in order of: Cd≤ Cu ≤Pb≤ Cr≤Mn≤ Zn(LSD0.05). Result revealed that Cr, Cd and Pb were below the limits for agricultural soil by FAO, and were higher at 50-100m and decrease farther from incinerator. Negative correlation exists between Cr and Zn; Zn and Cu due to farming practices, Mn, Cd recorded positive correlation due to incinerator flue ash. Factor 1 loaded Cu positively, Cr, Pb, Mn, and Zn negatively loaded. Factor 2, exception of Cr, Cd, Pb, and Mn loaded negatively due to flue gas and lithogenic respectively, C/PI indicated soil being slightly, moderately to severely contaminated respectively. I_-geo indicated uncontaminated to moderately contaminated, showing that heavy metal contaminations of soils is minor.

Keywords: Element, Incineration, Flue Smoke, Soil Acidity, multivariate analysis