Levels and mobility of Cu, Pb and Cd in citrus orchards of two contrasting ages in north-central region of Nigeria

Widespread contamination of cultivated lands with heavy metals increase human exposure to contaminated agricultural products. The study investigated soil levels and transfer of Cu, Pb and Cd into leaves and barks of different citrus species in 35- and 11-year old orchards in north-central region of Nigeria. Heavy metals concentrations in soils were below permissible limits but greater than background concentrations (Cu = 2.27 mg kg-1, Pb = 0.25 mg kg-1 and Cd = 3.9 mg kg-1). Geo-accumulation index (Igeo) indicated that the 35-year orchard (orchard I) soil was uncontaminated with Cu (Cu-Igeo = -0.43), uncontaminated to moderately contaminated with Pb (Pb-Igeo < 0.39) and moderately contaminated with Cd (Cd-Igeo = 1.65). The 11-year old orchard (orchard II) soil was uncontaminated to moderately contaminated (Igeo for Cu, Pb and Cd was ≤ 1). Bioavailability of the heavy metals soil of orchards I and II were ≥ 30%. Levels of Cd and Pb in bark and leaf tissues were above the maximum permissible limits whereas Cu concentration was within the recommended nutritional status (10 - 50 mg kg-1) for fruit trees. Soil-to-tissue transfer (bioaccumulation) of all heavy metals into the citrus species was ≥ 1.0 and higher in orchard II. High concentration of heavy metals in the leaves and barks of the different citrus species is related to their high bioaccumulation factors despite the relatively low soil concentration of heavy metals in the orchards

Surrogate approach to determine heavy metal loads in a moss species – Barbula lambaranensis

AbstractBiomonitoring using a moss species Barbula lambaranensis is an economical method for continuous assessment of atmospheric metal pollution. However, frequent measurement of common heavy metals such as Zn, Cd, Cr, Pb, Cu and Ni in moss can be costly for monitoring large areas. Thus, the aim of the study was to use the surrogate approach to reduce the number of heavy metals required for monitoring. The study found that the Zn load in moss was higher; Pb, Cu and Ni loads were moderate; while Cd and Cr were relatively lower across the study sites. Further, the following surrogates were identified based on PCA: Cu for Cr; Pb for Cd, Cu and Ni; and Cu and Pb for Zn. Quantitative relationships between surrogate loads and the loads of other heavy metals were developed by performing Multiple Linear Regression on a data set constructed using a four level full factorial design. The equations had a relative prediction error and standard error of cross validation below 25% and 1.5%, respectively, indicating that the equations are accurate. However, the cross validated coefficient of determination is relatively low suggesting that the precision of prediction using the equations is low, possibly due to the influence of factors such as climatic conditions on bioaccumulation of heavy metals by moss. Nevertheless, the developed equations can be useful for preliminary investigations

Thuja occidentalis and Duranta repens as indicators of urban air pollution in industrialized areas of southwest Nigeria

This paper assessed biochemical parameters in leaves of selected ornamental species growing in urban areas of southwest Nigeria to obtain the air pollution tolerance index (APTI) and anticipated performance index (API) for classification into tolerant and sensitive species against air pollution. Four sites and three ornamental species (Polyalthia longifolia, Thuja occidentalis and Duranta repens) common to the sites were used for this study. Results showed significant variations in biochemical variables, hence biochemical parameters cannot be used solely to categorize the species. APTI values obtained suggested that P.  longifolia    is tolerant species to air pollutants while T. occidentalis and D. repens are sensitive species that can be used as bioindicators of air pollutants. The API value revealed P. longifolia and T. occidentalis to be poor performer and very poor performer respectively while D. repens cannot be recommended for greenbelt development. Therefore, T. occidentalis and D. repens, can be recommended as bioindicators of poor urban air quality

Soil Fertility Status under Different Tree Cropping System in a Southwestern Zone of Nigeria

Tree cropping has been known to bring about changes in edaphic component among other components of the ecosystem through their interactions with the soil and soil faunas. Premised on this, this study assessed the effects of sole cropping of teak and intercropping of cocoa and kola on the soil fertility status. The study was carried out using stratified-randomed sampling technique for the study plots in all the sampling sites. Three sampling sites consisting of four (4)-4oo m2 sampling plots each were established in which vegetation and some soil parameters were assessed. Results analysis showed that the synergistic interaction of leaves decomposition of cocoa and kola improved the organic matter content of the soil under the cocoa/kola site. Considerable improvement in soil fertility was enjoyed in the cocoa/kola site due to the large girth sizes and basal area of trees present in the cocoa/kola site while soil under the sole cropping of teak was impoverished. The degradation effects was due to the high rate of nutrient uptake of the teak, organic matter content was high in the forest site (9.12%) and cocoa/kola site (7.34) while the least was in the teak site (3.04%). A very strong correlation existed between organic matter content and some vegetation parameters

Eco-distribution of Vitellaria paradoxa (G.F. Gaertn) in Kwara State, Nigeria

The conservation status of Vitellaria paradoxa in Kwara state was studied. The frequency ranged from 20% at Offa and Ilofa to100% at Jebba and Kaiama, as the shea tree occurred twice in the ten sampling points at Offa and Ilofa, but occurred in all sampled sites at Jebba and Kaiama. The highest tree mean density of 34 trees/ha was noted at Kaiama and the lowest at Offa 4 trees/ha. The overall mean densities of the species was 13.33 trees/ha. These show that Vitellaria paradoxa trees were more conserved towards the Northern part of the state than the Southern part. The majority of the trees were between (21-30 cm) diameter class, which indicated that they were saplings and very few were around (<10 cm) diameter class. The results showed low population of seedlings in the state, especially at the Northern part of the state. This might be due to trees’ removal for farming activities, uncontrolled incessant bush burning and trampling by grazing live stocks in the areas

Assessment of metallic pollution status of surface water and aquatic macrophytes of earthen dams in Ilorin, north-central of Nigeria as indicators of environmental health

The functional quality of an aquatic ecosystem is a reflection of the health of the environment. Therefore, the present study evaluates the trace metal contamination (Pb, Cd, Ni and Mn) of water and aquatic macrophytes in Asa, Agba, Unilorin and Sobi (Moro) earthen dams, north-central Nigeria to evaluate the level of anthropogenic impact on the immediate environment. The concentrations of trace metals in samples of water and available macrophytes from the earthen dams were determined by Atomic Absorption Spectrophotometry. Trace metal contamination of surface water in the earthen dams was assessed using metal index (MPI) and metal pollution index (HPI). The biological accumulation factor of trace metals in the aquatic macrophytes was extrapolated from trace metal concentrations in the water and macrophyte samples. The results of the MPI revealed gross metal contamination of the surface water by Pb and Cd (>6.0 for both metals) in the four earthen dams; while Agba and Sobi dams were slightly contaminated by Ni (MPIs = 1.43 and 1.14 respectively). All the earthen dams were considered safe from Mn contamination (MPI  100), but Asa dam (HPI = 2682.4) was the most contaminated. The biological accumulation factor of Mn in the macrophytes indicated Ceratophyllum demersum, Pycreus lanceolatus and Pistia stratiotes as moderate accumulators of Mn, and can be used as bioindicators in monitoring Mn pollution of aquatic ecosystem. The obtained results in this study showed that the earthen dams are polluted by Pb, Cd and Ni which pose human health risks to the inhabitants through drinking water

Growth Response of Three Leafy Vegetables to the Allelopathic Effect of <i>Vitellaria paradoxa</i>

<p>This study was conducted to evaluate the growth response of three leafy vegetables (<em>Celosia argentea</em>, <em>Amaranthus cruentus </em>and <em>Amaranthus hypochodriacus</em>) to the leaf extract of <em>Vitellaria paradoxa.</em> Forty-five (45) experimental plastic containers were filled with 5 kg of loamy soil each and randomly allocated to the following regimes: control, 20 g, 40 g, 60 g and 80 g of powdered leaves of <em>V. paradoxa</em>, in three (3) replicates for each test crop respectively.<em> </em>It was observed that the response of the three leafy vegetables, grown within different composition of <em>V. paradoxa</em> leaves, are concentration dependent with respect to the studied growth parameters (plant height, leaf number, leaf area, stem girth). This indicated that <em>V. paradoxa </em>has allelopathic potential on the studied vegetables and therefore it could be used for natural weed control.</p

Growth Response of Three Leafy Vegetables to the Allelopathic Effect of &lt;i&gt;Vitellaria paradoxa&lt;/i&gt;

This study was conducted to evaluate the growth response of three leafy vegetables (Celosia argentea, Amaranthus cruentus and Amaranthus hypochodriacus) to the leaf extract of Vitellaria paradoxa. Forty-five (45) experimental plastic containers were filled with 5 kg of loamy soil each and randomly allocated to the following regimes: control, 20 g, 40 g, 60 g and 80 g of powdered leaves of V. paradoxa, in three (3) replicates for each test crop respectively. It was observed that the response of the three leafy vegetables, grown within different composition of V. paradoxa leaves, are concentration dependent with respect to the studied growth parameters (plant height, leaf number, leaf area, stem girth). This indicated that V. paradoxa has allelopathic potential on the studied vegetables and therefore it could be used for natural weed control

Transfer of metals from crude oil impacted soils to some native wetland species, the Niger-delta, Nigeria: Implications for phytoremediation potentials

In this study, wetland species growing naturally in the surrounding of two crude oil facilities were sampled and screened for their phytoremediation potentials for zinc, lead, nickel, chromium and cadmium in soil. Concentrations of metals in the root and shoot samples of the wetland species alongside the rhizosphere soil were determined. Metal accumulation in wetland species exceeded the permissible limits, but it was still within phytotoxic thresholds except for chromium. The use of a bioconcentration factor and a transfer factor to screen the wetland species for phytoremediation potentials identified six out of the eight studied species as multi-elemental phytostabilizers of metals in soil. In addition, five of the eight wetland species displayed potentials for phytoextraction of metal, though there was no multi-elemental phytoextractor among the wetland species. Paspalum vaginatum, Andropogon tectorum and Kyllinga squamata portend potential abilities to phytoextract nickel. In addition, Setaria longiseta and Pteridium aquilinum also showed strong potential to phytoextract lead and cadmium respectively from soil. This screening assessment is hoped to be useful in the applications of a cost-effective green technology to remediate heavy metals in contaminated soil