Scattered literature is harnessed to critically review the possible sources, chemistry, potential biohazards and best available remedial strategies for a number of heavy metals (lead, chromium, arsenic, zinc, cadmium, copper, mercury and nickel) commonly found in contaminated soils. The principles, advantages and disadvantages of immobilization, soil washing and phytoremediation techniques which are frequently listed among the best demonstrated available technologies for cleaning up heavy metal contaminated sites are presented. Remediation of heavy metal contaminated soils is necessary to reduce the associated risks, make the land resource available for agricultural production, enhance food security and scale down land tenure problems arising from changes in the land use pattern.

Changes in heavy metal speciation and uptake by maize in a soil before and after washing with chelating organic acids, citric acid, tartaric acid and ethylenediaminetetraacetic acid were assessed. A sandy loam was collected from the vicinity of the Benue industrial layout, Makurdi, Nigeria and spiked with a quinternary mixture of nickel, copper, zinc, cadmium and lead nitrates to achieve higher levels of contamination. Batch soil washing experiments performed on 1.0 g portions of the spiked soil using 0.05 M chelating agents at a solid:liquid ratio of 1:25 showed that washing efficiencies varied in the order: ethylenediaminetetraacetic acid> citric acid> tartaric acid with metal extraction yields typically following the sequence, copper> nickel> zinc> cadmium> lead. Sequential extractions proposed by the European Communities Bureau of Reference method used to assess the redistribution of heavy metal forms in the soil showed that apparent metal mobilities were reduced upon soil washing. Citric acid removed most of the metals hitherto associated with the exchangeable and reducible fractions; tartaric acid, the exchangeable metal pools; and ethylenediaminetetraacetic acid, the non-residual metal pools. Heavy metal assay of harvested biomass of maize grown on unwashed and washed soil samples indicated that metal transfer coefficients, decreased in the order of treatment: ethylenediaminetetraacetic acid

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Environmental contamination is one of the serious challenge facing humanity and other life forms on our planet today. contamination occurs when contaminating substances exceeds their natural levels or when natural resources are use at a rate higher than nature’s capacity to restore itself. This study determines the levels of mineral element and potential toxic metals namely: P, K, Mg, Mn, Si, Fe, Zn, Cd, Pb and Al in agricultural soil around mechanic village Wukari-Nigeria. by means of MP-AES (4210 MP-AES Agilent technologies) while their pollution indices by means of geo-accumulation index and contamination factor. The results reveals that the mean ± standard deviation abundance of mineral and heavy metals in the soil was: Fe (20723.64±153.71), Al (3753.80±30.54) K (368.13±2.17), Mg (298.05±3.88), Mn (231.97±0.74), P (221.22±5.47), Zn (184.83±0.47), Pb (86.29±0.31), Si (64.27±0.43) and Cd (1.33±0.06). There was generally a significant difference between the concentration in the test and control sample (P < 0.05). While pollution indices show moderate to very high contamination of the soil by zinc, lead and cadmium signalling higher potential risk in terms of mobility on acidification since the organic content is moderate and soil texture being sandy-loam usually characterise with moderate capacity to immobilize heavy metals. Lead contamination can result in neurological and hematological dysfunctions, renal and hepatic damages as well as reproductive disorders in the humans while cadmium is known to have effect on kidney.

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Aim: In a bid to reduce the environmental impact from the use of herbicides, chitosan was used for the synthesis of copper nanoparticles and the controlled release formulations (CRFs) of pendimethalin copper-chitosan nanoparticles (Pend-CuCtsNPs). Methodology: The synthesized nanoparticles were characterized using UV-visible spectroscopy, Fourier Transform Infra-Red (FT-IR), Powder X-ray diffraction (PXRD), Transmission electron microscopy (TEM) and Energy-dispersive x-ray (EDX). Average crystalline size of the nanoparticles was estimated from the Debye-Scherrer's equation. Results: The yield of the synthesized CuCtsNPs increased linearly with the weight of the starting material with percentage yield of 93.8% for the 0.8% chitosan matrix. Encapsulation efficiency of the nano-formulation fell within 57.5 and 92.7%. The aqueous release studies of Pend-CuCtsNPs, monitored for 96 hours in a batch release mode were carried out in three different pH media and percentage herbicide released for all composites showed that the release in pH 5.5 (acidic) medium was higher and the lowest release was recorded for pH 7.0 (neutral) medium. There was a