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

Anatomical Response of &lt;i&gt;Amaranthus hybridus&lt;/i&gt; Linn. as Influenced by Pharmaceutical Effluents

Anatomical studies were carried out on the leaves, stems and roots of Amaranthus hybridus subjected to irrigation of 10%, 20%, 30% and 40% concentrations of pharmaceutical effluents to identify the responses of this plant to the treatment. Leaf structures of A. hybridus showed no significant change due to the effect of the effluents. Significant reduction was observed in the trichome density and number of epidermal cells at the adaxial surface as from the 20% effluent concentration upward (