Abstract
The speciation of toxic metals of Co, Cr, Cu, Mn, Pb, Zn, Ni and As in Kwanar – Doya Shooting site of the Nigerian Army, Military Training, Base Camp, Kachia, Kaduna State, Nigeria was investigated. The soil physico-chemical parameters, total metal content and sequential extraction methods were determined in duplicates using standard methods. The pH ranged from 3.93–4.51, showing the high acidity of the soil and electro -conductivity gave a mean value of 0.11 ms / cm showing the poor nutrient value of the soil). While the mean total metals values were Zinc: 28.94 mg/kg, Nickel: 13.45mg/kg, Manganese: 78: 12 mg/kg, Lead: 40.6 mg/kg, Arsenic: 305 mg/kg, Chromium: 49.32 mg/kg, Cobalt: 162:50 mg/kg and copper: 7.3 mg/kg. All the metals were above the W.H.O permissible limit for toxic metals in soils except Zinc and Nickel. The sequential partitioning and distribution and variation of toxic metals in the various fractions of the Nigerian Defence Academy Shooting Range soil were in the following order: Cobalt: Residual > Bound to carbonate > Exchangeable > Organic > Fe – Mn Oxide Arsenic: Fe – Mn Oxide > Bound to carbonate > Residual > Organic > Chromium: Bound to carbonate > Exchangeable > Fe – Mn Oxide > Organic > Residual. Nickel: Fe – Mn Oxide > Exchangeable > Bound to carbonate > Residual > Organic. Manganese: Residual > Fe – Mn Oxide > Bound to carbonate > Organic > Exchangeable. Lead: Residual > Organic > Bound to carbonate > Exchangeable > Fe – Mn Oxide. Zinc: Fe – Mn Oxide > Residual > Organic > Bound to carbonate > Exchangeable. Copper: Residual > Fe – Mn Oxide > Exchangeable > Bound to carbonate > Organic. The Toxic metals speciation of the soil samples indicate that the toxic metals were predominately in the non-residual fractions suggestive of input by anthropogenic sources and human activities due to military exercise and are readily available for plant uptake. This could pose serious health risk to the military personnel using the training period. Thus phyto-remediation technique which is cheap and non-destructive is recommended to be applied to remedy the affected toxic metals in the soil for its continual use as a military training ground and also preserve the soil fertility for continued agricultural use of the area when there is no military operation.
Highlights
Heavy metals are present in the environment and most of them are essential for animals and plants
Soil samples were collected from the Kwanar –Doya Shooting site in the Nigerian Army Base Camp military shooting range, Kachia Local Government, Kaduna State
This study has revealed that the soil sample obtained from the Kwanar-Doya shooting site of the Nigerian Army Military Training Ground, camp highland, Kachia, Kaduna State was acidic and had little nutrients in the soil
Summary
Heavy metals are present in the environment and most of them are essential for animals and plants. There is always a natural background level of metals originating from the parent rocks and these metals can occur in high concentration but in an inert form which, can be converted to mobile and dangerous forms due to changing environmental conditions or changes in soil properties and this could lead to a “chemical time bomb” [2]. Heavy metals such as copper, nickel, chromium, and zinc are used in all kinds of practical objects and building materials without the users understanding its harmful risk. A heavy metal is not toxic per se; it is only considered toxic when its concentration exceeds a certain threshold (it is the dose that makes the effect) [5]
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