Fractionation and bioaccumulation of copper and zinc in wetland soils of the Niger Delta determined by the oil palm

Abstract

The concentration, mobility, bioavailability, distribution and associations of two essential micronutrient elements (copper and zinc) to the oil palm in wetland soils of the Niger delta region of Nigeria was assessed by means of chemical fractionation analysis. The water soluble and plant available fractions were introduced into the sequential extraction scheme. Also assessed were the bioaccumulation (concentration and distribution) of these metals in the leaves and fruits of the oil palm of various ages found around the soil profiles. Copper was obtained more in the amorphous Fe -oxide fraction (151.05 mg kg), but evenly distributed in the exchangeable component (16.16%) with a maximum value of 126.6 mg kg À 1 . The water soluble and plant available fractions had 16.15 and 7.54% distribution of Cu respectively. Zinc had 2.35 and 30.42% distribution in the water soluble and plant available fractions respectively. The lowest mean amount of Cu (1.33 mg kg À 1 ) was determined in the leaves of palms of ages 15 -32 years. Palms greater than 60 years had the highest mean concentration of copper (3.91 mg kg À 1 ) in the leaves while the endosperm (kernel) of palms between 2 and 10 years had concentration of 9.07 mg kg À 1 . The fibrous oily mesocarp had the highest amount (16.78 mg kg À 1 ) of copper in the older palms (460 years). Similarly, Zn was dominant in the older palms with a mean concentration of 187.14 mg kg À 1 obtained in the endosperm (kernel). The bioaccumulation pattern of both metals by the palms irrespective of age and the fractionation analysis revealed sufficient bioavailable and reserved amounts of Zn and Cu in the wetland soils.

Differential speciation and availability of copper in soils derived from different parent materials in Imo State, southeastern Nigeria

“…The highest mean value of 6.389 mgkg-1 equivalent to 46.63% of the total copper concentration was observed in the soils derived from alluvium while the lowest mean value of 2.231 mg kg -1 equivalent to 45.42% of the total Copper concentration was recorded in the soils derived from the Imo clay shale. A comparison with the other copper fractions showed that the Fe-Mn bound copper was the most dominant fraction which is consistent with the reports of Kabat-Pendias and Pendias (2001) and that of Oviasogie et al (2011) for alluvial soils of the Niger Delta, Nigeria. Kabata-Pendias (2011) had reported that the greatest amounts of adsorbed Cu have always been found in Fe and Mn oxides (hematite, goethite, birnessite), amorphous Fe and Al hydroxides, and clays (Kabata-Pendias, 2011) which could be due to adsorption mechanism of copper onto metal oxides.…”

“…The specifically sorbed/carbonate Cu content of the soils based on their parent materials was in a decreasing order of alluvium > coastal plain sands > Imo clay shale > false bedded sandstones. The values obtained for the soils of the alluvium and falsebedded sandstones were similar to those the reported by Oviasogie et al (2011) in the wetland (Alluvium) soils of the Niger Delta, Nigeria and those reported by Yu et al (2004) for some Inceptisols derived from sandstones in China, respectively. The results further showed decreasing concentration of the specifically sorbed/carbonate with depth in the soil derived from the alluvium but the distribution in the other soils did not follow any well-defined pattern.…”

“…Apart from the 1.125 mg kg -1 residual Cu contained in the surface of the soil derived from the False-bedded sandstones, residual Cu was not detectable in the soils. The results were similar tothose of Oviasogie et al (2011) in the wetland (H20) 0.23 -0.13 -0.30 0.03 0.06 0.04 W-S-water soluble, Avail. P-available phosphorus, ECECeffective cation exchange capacity, OM -organic matter, *-Significant at 5% probability level, **-significant at 1% probability level (Alluvium) soils of the Niger Delta, Nigeria but far below mean value of 30.03 mg kg -1 reported by Fathi et al (2014) in some soils of Iran.…”

“…Generally, the concentrations of copper fractions differed in each of the soil profiles. The fractions decreased in the order; Coastal Plain Sands: F4 > F3 > F2 > F5 > F1 > F6 Alluvium: F4 > F3 > F5 > F2 > F1 > F6 False Bedded Sandstones: F4 > F3 > F1 > F2 > F6 > F5 Imo Clay Shale: F4 > F3 > F2 > F1 > F5 -F6 This clearly shows the dominance of the Fe-Mn oxide bound Cu in the soils which is consistent with the report of Oviasogie et al (2011) in the wetland (Alluvium) soils of the Niger Delta, Nigeria.…”

“…Parent materials tend to govern the initial status of copper fractions in soils (Melo, 2006). It has been reported that soils derived from alluvium are richer in organic matter bound copper than soils derived from coastal plain sands (Ideriah et al, 2013;Oviasogie et al, 2011) Also, higher concentration of water soluble copper has been observed in soils derived from sandstones relative to soils derived from highly weathered quaternary red earths (Yu et al, 2004). An evaluation of total metal levels following a strong acid digestion of soil may be useful as a general indicator of contamination, but it provides little indication of metal's bioavailability, mobility, and reactivity in soils (Baltrenaite et al, 2009).…”