Contents lists available at ScienceDirect Ecotoxicology and Environmental Safety journal homepage: www.elsevier.com/locate/ecoenv Cow manure-loaded biochar changes Cd fractionation and phytotoxicity potential for wheat in a natural acidic contaminated soil Ibrahim Mohamed a,b,c,d, ⁎ , Maha Ali c , Nevin Ahmed e , Mohamed H.H. Abbas c , Mohamed Abdelsalam c , Ahmed Azab f , David Raleve d , Chen Fang a,b, ⁎ a Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Science, Wuhan 430074, China b China Program of International Plant Nutrition Institute, Wuhan 430074, China c Soils and Water Department, Faculty of Agriculture, Benha University, Moshtohor, Toukh, Kalyoubia 13736, Egypt d Graduate University, Chinese Academy of Sciences, Beijing 100049, China e Plant Protection Department, Faculty of Agriculture, Benha University, Moshtohor, Toukh, Kalyoubia 13736, Egypt f Agriculture Engineering Research Institute, Agricultural Research Center, Giza, 256, Cairo, Egypt ARTICLE INFO Keywords: Cadmium Fractionation Accumulation Biohcar Contaminated soils ABSTRACT The current study aims to investigate the implications of amending a soil contaminated with Cd with peanut residues biochar (BP) solely or in combination with cow manure (CMPB) at different rates on phytotoxicity of Cd for wheat plants and its distribution in a mine contaminated soil. Soil pH and EC increased progressively in soils amended with either PB or CMPB. Exchangeable Cd was decreased while its non-exchangeable fractions were increased. Dry weights of wheat straw, roots and grains increased when soils amended with either PB or CMPB, especially at the higher application rate. Such increases were correlated significantly with the extractable soil- Cd. Concentrations of Cd in roots were higher than those in straw; whereas, the concentrations in grains seemed to be the lowest. Generally, values of bio-concentration and translocation factors did not exceed “1” and de- creased with application of either PB or CMPB. In conclusion, enriching biochar with cow manure is a re- commended strategy to reduce Cd uptake and translocation to straw and seeds. Moreover, Concentrations of Cd did not exceed the permissible levels in grains when soils amended with the highest rate of CMPB. 1. Introduction Contamination of agricultural soils with heavy metals is one of the important issues worldwide (Kumarathilaka et al., 2018). These metals are brought to soils through the movement, discharge, and dispersion of the effluents and wastes of coal combustion, mining and smelting ac- tivities (Yun et al., 2016). Shockingly, these contaminants are non-de- gradable (Bolan et al., 2014); and their toxicity depends mainly on their availability in the soil (Mohamed et al., 2015) rather than their total contents (Abbas and Abdelhafez, 2013). The high presence of Cd in soils has negative implications on the ecosystem e.g. plant growth, animals and human health (Hussain et al., 2015; Naeem et al., 2016; Rizwan et al., 2016). Remediation of contaminated soils can be conducted by ex-situ techniques (Younis et al., 2015), but many of these methods (excavation, landfilling and soil washing) are not appreciated because of their high costs and environmental disturbance (Efroymson et al., 2004). Thus, using organic residues may provide a suitable alternative for remediating soils contaminated with heavy metals (Abbas et al., 2017; Kumarathilaka et al., 2018). Incorporation of organic amend- ments in soils has received growing interests because of their cost-ef- fective and eco-friendly influences on soil properties such as structure, fertility and quality (Park et al., 2011; Houben et al., 2012; Mohamed et al., 2015). Moreover, such amendments decrease the availability of heavy metals in soil due to sorption, oxidation/reduction, precipitation processes and formation of stable complexes with the functional groups of the organic amendment such as phenolic, carboxylic and hydroxylic (Rehman et al., 2016; Yousaf et al., 2016). The binding capacity of heavy metals with the organic amendment is usually influenced by many factors, including soil type, pH, ionic strength, organic matter, redox potential, cation exchange capacity and metal properties (Ali et al., 2017; Yue et al., 2017). It is worthy to mention that sensible concentrations of the bound heavy metals with the organic amendment may return back to soils during the decomposition process of the or- ganic matter (Yue et al., 2017). Thus, selecting the appropriate https://doi.org/10.1016/j.ecoenv.2018.06.065 Received 1 April 2018; Received in revised form 16 June 2018; Accepted 20 June 2018 ⁎ Corresponding authors at: Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Science, Wuhan 430074, China. E-mail addresses: Ibrahim.ali@fagr.bu.edu.eg (I. Mohamed), fchen@ipni.ac.cn (C. Fang). Ecotoxicology and Environmental Safety 162 (2018) 348–353 0147-6513/ © 2018 Published by Elsevier Inc. T