Element bioavailability of trace

The book focuses on the biogeochemistry of trace elements in arid and semiarid zone soils and includes an introductory chapter on the nature and properties of arid zone soils. It presents an updated overview and a comprehensive coverage of the major aspects of trace elements and heavy metals that are of most concern in the world s arid and semi-arid soils. These include the content and distribution of trace elements in arid soils, their solution chemistry, their solid-phase chemistry, selective sequential dissolution techniques for trace elements in arid soils, the bioavailability of trace elements, and the pollution and remediation of contaminated arid soils. A comprehensive and focused case study on transfer fluxes of trace elements in Israeli arid and semi-arid soils is presented. The book concludes with a discussion of a quantitative global perspective on anthropogenic interferences in the natural trace elements distributions. The elements discussed in this book include Cd, Cu, Cr, Ni, Pb, Zn, Hg, As, Se, Co, B, Mo and others. This book is an excellent reference for students and professionals in the environmental, ecological, agricultural and geological sciences. 

Dissolved organic molecules have many acidic functions (hydroxol and carbonic groups) to complex trace elements and their compounds to form soluble chelates. This is one of the reasons why solubility and bioavailability of trace elements in the rhizosphere are higher than bulk soils. At the same time, many organic acids also directly dissolve trace elements and their compounds in soils. Plant-produced phytosiderophores facilitate elements, such as Fe and Zn, uptake by plants (Zhang et al., 1991 Romheld, 1991 Hopkins et al., 1998). However, Shenker et al. (2001) did not find significant uptake of the Cd-phytosiderophores complex by plant roots. 

BIOAVAILABILITY OF TRACE ELEMENTS IN ARID ZONE SOILS... 

Plant roots and root-induced chemical changes in the rhizosphere strongly affect the bioavailability of trace elements (Hinsinger, 1999). First, root-induced changes in the ionic equilibria influence the bioavailability of trace elements. The differential rates of plant uptake of water and ions in the soil solution result in a depletion or an accumulation of the ions in the... 

Table 7.3. Bioavailability of trace elements in arid and semi-arid soils...

The bioavailability of trace elements in soil-water-plant ecosystems of arid zones is largely determined by their partitioning between solution and solid-phase components. The redistribution and transformation of trace elements among solid-phase components under various biogeochemical conditions strongly adjust their lability and bioavailability. Soluble, exchangeable and organically bound forms are bioavailable to plants. The carbonate bound fraction represents a reservoir of potentially bio-available trace elements to plants. In paddy soils, the amorphous Fe/Al oxide fraction contributes to trace element availability as well. 

Patrick, 1977). In addition, the bioavailability of trace elements in arid soils contaminated with mine tailings increased with decreasing soil pH due to oxidation of sulfide minerals. 

The termination of sewage biosolids applications in arid soils often results in decreases in the bioavailability of trace elements. Webber and Beauchamp (1979) found a stronger statistical relationship of Cd uptake in com to the amount of Cd added in the most recent sludge application than to... 

Han and Banin (1997, 1999) and Han et al. (2001a) found that concentrations of bioavailable trace elements (Cu, Ni and Zn, as extracted by NH4NO3 at pH 7) in general, decreased with time in two Israeli arid soils contaminated with metal salts under the saturated paste, field capacity, and wetting-drying cycle moisture regimes for one year (Fig. 7.6). However, the bioavailability of trace elements was strongly dependent upon the nature of... 

In addition, plant growth rate also affects plant uptake and the bioavailability of trace elements. It was reported that the rate of As uptake by rice increased as the rate of plant growth increased (Onken and Hossner, 1995). 

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