Department of Soil Science, Faculty of Agriculture, Ahmadu Bello University, PMB 1044, Zaria, Nigeria.
Environ Monit Assess. 2012 Apr;184(4):2057-66. doi: 10.1007/s10661-011-2099-2. Epub 2011 May 21.
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.
金属形态分析提供了有关各种金属物种迁移性和稳定性的信息，可用于评估这些金属在土壤中的迁移情况。本研究调查了尼日利亚卡诺市 5 个城市花园中污水灌溉对镉 (Cd) 和锌 (Zn) 形态、空间分布和迁移性的影响。表层土壤（0-20cm）中总 Zn 浓度范围为 121-207mgkg-1，而 Cd 浓度为 0.3-2.0mgkg-1。将这两种重金属分为 7 种操作定义的形态，结果表明，用硝酸铵和乙酸铵提取的最易反应形态（也被认为是生物有效形态）分别占总 Cd 的 29-42%和总 Zn 的 22-54%。Cd 和 Zn 的弱结合形态分别达到土壤中总 Cd 和 Zn 浓度的 50%。如此高比例的 Cd 和 Zn 可利用形态表明，这些形态是人为来源的，来自于污水灌溉和城市生物固体用于提高土壤肥力。因此，鉴于沙质土壤质地占主导地位，这些花园土壤中高浓度的 Cd 和 Zn 易利用形态可能会导致这些金属重新分布和转移到食物链和含水层中，存在潜在危害。
