Heavy metals bioavailability

Sloan, J. J., Dowdy, R. H., Dolan, M. S., Linden, D. R. (1997). Long-term effects of biosolids applications on heavy metal bioavailability in agricultural soils. J. Environ. Qual. 26,966-974. 

The U.S. EPA has proposed the concept of Water Effect Ratio (WER) to take into account the effect of the above mentioned factors on heavy metal bioavailability/toxicity in environmental samples (U.S. EPA, 1982, 1984, 1994). EPA water quality criteria for metals have often ignored the local water quality conditions. Thus, WER is the ratio of the LC50 derived from testing the toxicity of a metal to fish or invertebrates in site water to the LC50 derived from testing the toxicity of the same metal to the same test organism (fish or invertebrate) in laboratory water. 

Lu HL. Low molecular weight organic acids in mangrove wetlands and their impact on heavy metals bioavailability. Xiamen University Doctoral thesis, 2006. 

The behavior of elements (toxicity, bioavailability, and distribution) in the environment depends strongly on their chemical forms and type of binding and cannot be reliably predicted on the basis of the total concentration. In order to assess the mobility and reactivity of heavy metal (HM) species in solid samples (soils and sediments), batch sequential extraction procedures are used. HM are fractionated into operationally defined forms under the action of selective leaching reagents. 

Corbisier, R, van der Lelie, D., Borremans, B., Provoost, A., de Lorenzo, V., Brown, N., Lloyd, J.R., Hobman, J.L., Csoregi, E., Johansson, G., and Mattiasson, B., Whole cell- and protein-based biosensors for the detection of bioavailable heavy metals in environmental samples, Anal Chim Acta, 387 (3), 235-244, 1999. 

Evaluating the use of composts for reduction of the bioavailability and phytoavailability of lead and other heavy metals in contaminated soils... 

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. 

In addition, dissolved organic carbon (DOC) is also an important soil solution solute affecting speciation and bioavailability of many trace elements in soil solution. Many trace elements and heavy metals complex with dissolved organic carbon. This is especially important in arid and semi-arid environments since high soil pH increases the solubility of organic molecules and accordingly increases concentrations of dissolved organic carbon in soil solution. 

Chemical remediation refers to the application of various minerals or chemicals to adsorb, bind, precipitate or co-precipitate trace elements and heavy metals in soils and waters thereby reducing their bioavailability, toxicity, and mobility. In situ immobilization refers to the treatment of contaminants in place without having to excavate the soils or waste, often resulting in substantial cost savings. However, in situ immobilization or extraction by these physicochemical techniques can be expensive and are often only appropriate for small areas where rapid and complete decontamination is required. 

Brown G.E. Jr., Foster A.L., Ostergren J.D. Mineral surfaces and bioavailability of heavy metals A molecular-scale perspective. Proc Natl Acad Sci 1999 96 3388-3395. 

Han F.X., Kingery W.L., Selim H.M. Accumulation, redistribution, transport and bioavailability of heavy metals in waste-amended soils. In Trace Elements in Soil Bioavailability, Fluxes and Transfer, Iskander IK, Kirkham MB, eds. Boca Raton, FL CRC Press, 2001c. 

Phytate (myo-inositol hexaphosphate Fig. 15.3, structure 33) is found in many food species and can be considered as a phytochemical. Its role in the plant is primarily as a phosphate store in seeds, but it is found in other tissues as well, for example, tubers (Harland et al., 2004). Phytate and its hydrolysis products are anti-nutrients that chelate metal ions and thus reduce their bioavailability (Persson et al., 1998 House, 1999). This is particularly a problem with cereal grains, but pre-processing can improve mineral absorption from these foods (Agte and Joshi, 1997). There is some concern that high phytate foods could also contain higher levels of toxic heavy metals caused by natural accumulation. Plants also contain phytate-degrading enzymes that can also influence metal ion bioavailability (Viveros et al., 2000). 

Bryan, G.W. and W.J. Langston. 1992. Bioavailability, accumulation and effects of heavy metals in sediments with special reference to United Kingdom estuaries a review. Environ. Pollut. 76 89-131. 

Heavy metals in the environment, especially their accumulation in soils, is a serious environmental problem which the whole world faces (Du et al. 2005). The farmland soils are an important media of the ecological cycle of Cadmium, and its harm to human health can t be neglected (Wu et al. 2004). Heavy metal migration, transformation and toxicity to plants in soil are directly influenced by the quantity proportions of various forms (Zhu et al. 2002). The toxicity of water-extractable and adsorbed and exchangeable metals are the greatest, and residual metals is the lowest (Liu etal. 2002). Different forms have different bioavailability thus their influences on the environment and human health are different. It is critical to have a good understanding of Cadmium forms in soil. This paper describes the Cadmium forms in the acid soils of eastern China. 

The amount of organic matters not only determines the nutrition of the soils, but also form complex compound with heavy metals to influence metal migration and bioavailability (Liu et al. 2002). From table 1, we can found that extractable Cd contents, especially occluded Cd onto Fe-Mn oxides and organically bounded Cd has a prominent positive correlation with organic matters (a =0.05,n =30, F =0.361), (Fig. 2). Organic matters are one of the major factors which influence Cd... 

Table 5 also reveals that the mean concentration of Pb in brown rice and leaves of 19 vegetable species from acid rain affected areas and non-affected areas are almost the same. On the other hand, the ratio is close to 1. This result indicated that acid rain does not influence the biological accumulation of Pb in brown rice and leaves of vegetables species sampled in Taiwan. Some studies have indicated that concentration of Pb in the crops was only affected when the concentration of Pb in the soils is higher than 500 mg/kg (Kabata-Pendias and Pendias, 1992). Sloan et al. (1997) also indicated that the relative bioavailability of biosolids-applied heavy metals in agricultural soils was Cd Zn >Ni >Cu Cr >Pb, for the soils 15 years after biosolids application. It is quite consistent with the results achieved by research of Chen et al. (1998). Thus, the phyto-availability of heavy metals caused by acid deposition followed the trend Cd >Zn >Cu Pb. 

Sevenson claims that MAECTITE technology converts heavy metals and radionuclides in soil, groundwater, solid waste, debris, sludges, and other material into nonleachable forms that are stable over geological time spans. They also claim that the technology limits the bioavailability of lead in treated soil and can result in volume reduction with limited mass increase during treatment. 

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