Fractionation and mobility of cadmium and zinc in urban vegetable gardens of Kano, Northern Nigeria

Abstract

Metal fractionation provides information on mobility and stability of various metal species which can be used to evaluate the movement of such metals in soils. The effect of wastewater irrigation on the fractions, spatial distribution, and mobility of cadmium (Cd) and zinc (Zn) was investigated in five urban gardens in Kano, Nigeria. Concentration of total Zn in the surface soils (0-20 cm) ranged from 121 to 207 mg kg(- 1) while Cd concentration was 0.3-2.0 mg kg(- 1). Speciation of both heavy metals into seven operationally defined fractions indicated that the most reactive forms extracted with ammonium nitrate and ammonium acetate, also considered as the bioavailable fractions, accounted for 29-42% of total Cd and 22-54% of total Zn, respectively. The weakly bound fractions of Cd and Zn reached up to 50% of the total Cd and Zn concentrations in the soils. Such high proportions of labile Cd and Zn fractions are indicative of anthropogenic origins, arising from the application of wastewater for irrigation and municipal biosolids for soil fertility improvement. Thus, given the predominance of sandy soil textures, high concentrations of labile Cd and Zn in these garden soils represent a potential hazard for the redistribution and translocation of these metals into the food chain and aquifer.

Plant uptake of metals, transfer factors and prediction model for two contaminated regions of Kosovo

“…Extractability by EDTA follows this order in Drenas region: Cd > Pb > Cu > Ni > Zn >> Cr, and in Mitrovice region: Cd > Pb > Cu > Zn > Ni >> Cr. Similar results have been reported in other studies ( Takáč et al, 2009; Abdu et al, 2012; Nannoni et al, 2011; Ashraf et al, 2012; Zogaj et al, 2014).…”

“…Ammonium nitrate is used to assess the mobile form of heavy metals in soil ( Gryschko et al, 2005; Sabienë et al, 2004; Abdu et al, 2012). In Germany, exchangeable (mobile) soil metals are estimated by a 1M NH 4 NO 3 extraction procedure ( BBodSchV , 1999; DIN ISO 19730:2009 , 2009).…”

Spatial Distribution and Migration of Cadmium in Contaminated Soils Associated with a Geochemical Anomaly: A Case Study in Southwestern China

“…In all soil profiles, the reducible fraction was the main form of Cd, consistent with conclusions of some scholars [35,[43][44]. The ratio between the reducible fraction and total Cd ranged from 24.5% to 83.6%.…”

Vertical distribution of heavy metals in wastewater-irrigated vegetable garden soils of three West African cities

“…Even though the cities of Bobo Dioulasso and Sikasso are less populated and industrialized compared to Kano, HM may as well be accumulated in the profiles of these urban garden soils owing to the quality of irrigation water, high inputs of mineral fertilizers (Diogo et al 2010;Predotova et al 2010a) and pesticide application. While recent reports stressed the importance of HM loads in irrigation water and soils used for urban vegetable production in Kano (Binns et al 2003;Abdu et al 2010), to our knowledge comparative studies of heavy metal pollution of urban vegetable gardens across West African cities are missing.…”