Fractionation and Prediction of Copper, Lead, and Zinc Uptake by Two Leaf Vegetables from Their Geochemical Fractions in Urban Garden Fields in Northern Nigeria

• Published in: Communications in Soil Science and Plant Analysis 2010-01, Vol.41 (5-8), p.1028-1041
• Main Authors: Agbenin, John O, Welp, Gerphard, Danko, M
• Format: Article
• Language: English
• Subjects: adsorption; Agronomy. Soil science and plant productions; Amaranthus caudatus; Bioconcentration; Biological and medical sciences; Copper; crop production; crop yield; exchangeable cations; Fractionation; Fundamental and applied biological sciences. Psychology; green leafy vegetables; heavy metals; home gardens; iron; Lactuca sativa; lead; lettuce; magnesium; Metals; nutrient availability; nutrient uptake; phytotoxicity; quantitative analysis; roots; Soil and water pollution; soil nutrient dynamics; soil organic matter; soil pollution; Soil science; urban areas; urban gardens; vegetables; Zinc
• ISSN: 0010-3624; 1532-2416; 1532-4133
• DOI: 10.1080/00103621003648168

The bioavailability and mobility of heavy metals in soil are strongly influenced by the chemical or geochemical species of the metals in soils. We determined the geochemical fractions of copper (Cu), lead (Pb), and zinc (Zn) in garden soils, using the seven-step Zeien and Bruemmer fractionation scheme in relation to metal uptake by two leaf vegetables (lettuce, Latuca sativa, and amaranthus, Amaranthus caudatus). Our objective was to develop predictive models for assessing the lability of these metals from the soil metal fractions. The sums of fractions of Cu, Pb, and Zn did not differ by more than 10% from the “pseudo” total concentrations of the metals determined independently by aqua regia digestion. The general distribution of Cu and Pb among the soil fractions was in the order organic-matter-bound > Fe(o) and Fe(c) > Mn(ox) > exchangeable > residual > mobile, except for Cu, where residual and the exchangeable were reversed. Zinc was fairly evenly distributed among organic matter (20%), Fe(o) (22%), Fe(c) (20%), and residual (21%). Averaged across sites, Cu, Pb, and Zn concentrations in the lettuce were almost twice as great as the concentrations in amaranthus even though they were raised in the same fields. The variance in Cu, Pb, and Zn uptake by amaranthus was predicted up to 51-99% from soluble, exchangeable, organic matter, and Fe(o)-bound fractions; the variance in metal uptake by lettuce was best predicted from Fe(c)- and Fe(o)-bound fractions up to 76-90%. Our results indicated differential accessibility to metal fractions by lettuce and amaranthus grown in the same field.