Metals uptake

Soil. The first reported field trial of the use of hyperaccumulating plants to remove metals from a soil contaminated by sludge appHcations has been reported (103). The results were positive, but the rates of metal uptake suggest a time scale of decades for complete cleanup. Trials with higher biomass plants, such as B.juncea, are underway at several chromium and lead contaminated sites (88), but data are not yet available. 

Davis, J. S. and Leckie, J. O. (1978). Effect of adsorbed complexing ligands on trace metal uptake by hydrous oxides. Environ. Sci. Technol. 12, 1309-1315. 

Several factors can influence metal uptake by stream autotrophic biofllms in fluvial systems. These include chemical factors (pH, saUnity, phosphate concentration) which affect metal bioavailabiHty by either altering the speciation of the metal or by complexing it at the biotilm s matrix and cell surfaces [18, 40], and also other biological and physical factors. 

Overall the results reported in this review indicate that water scarcity might increase metal exposure (due to low dilution), metal uptake (due to higher retention under low flow), and metal toxicity and/or accumulation (depending on the dose and time of exposure), but also might cause opposite effects depending on the source of pollution. In addition, water scarcity will influence nutrient loads and will also modulate the fate and effects of metals. Thus, future studies addressing the role of environmental stress on the effects of toxicants at community scale are key to predict the impact of toxicants in the aquatic ecosystems. 

If the support is devoid of functional groups apt to interact with the metal precursor, there are not chemical forces facilitating the metal uptake. Under these conditions, metal uptake is driven by absorption forces and can still occur, but it is controlled by simple diffusion. This situation can favor an eggshell radial distribution of the metal precursor over a homogeneous one [31]. 

Scheme 2. Possible reaction for metal uptake by CFPs.

Nature of the most abundant comonomer. Nature of the groups devoted to metal uptake. Commercial ion-exchanger. 

M. J. Mench and S. Fargues, Metal uptake by iron-efficient and inefficient oats. Plant Soil 165 221 (1994). 

Verma, K.V., George, H.V., Singh, S.K., Singh, A., Juwarkar, A., and Singh, R.N., Modeling rhizofiltration Heavy-metal uptake by plant roots, Environmental Modeling and Assessment, 11, 387-394, 2006. 

Weis, J.S. and Weis, P., Metal uptake, transport and release by wetlands plants implication for phytoremediation and restoration, Environment International, 30 (5), 739-753, 2004. 

Rudd, T., Sterritt, R.M., and Lester, J.N., Mass balance of heavy metal uptake by encapsulated cultures of Klebsiella aerogenes, Microb Ecol, 9 (3), 261-272, 1983. 

Higher phytoextraction coefficients indicate higher metal uptake. The effectiveness of phytoextraction can be limited by the sorption of metals to soil particles and the low solubility of the metals however, metals can be solubilized through the addition of acids or chelating agents and so allow uptake of the contaminant by the plant. Ethylene diamine tetra-acetic acid (EDTA), citric acid, and ammonium nitrate have been reported to help in the solubilization of lead, uranium, and cesium... 

Baker A.J.M., Walker P.L. Ecophysiology of metal uptake by tolerant plants. In Heavy Metal Tolerance in Plants Evolutionary Aspects, A.J. Shaw, ed. Boca Raton, FL CRC Press. 1989. 

Latterell J.J. Dowdy R.H., Larson W.E. Correaltion of extrctable metals and metal uptake of snap beans grown on soil amended with sewage sludge. J Environ Qual 1978 7 425 140. 

Scanes, P. 1993. Trace metal uptake in cockles Anadara trapezium from Lake Macquarie, New South Wales. Mar. Ecol. Prog. Ser. 102 135-142. 

Greig, R.A. 1979. Trace metal uptake by three species of mollusks. Bull. Environ. Contam. Toxicol. 22 643-647. 

The different metal uptake by plants is accompanied by a different involvement of these trace metals and macronutrients in the biogeochemical cycles. A comparison of... 

The statistical estimation of heavy metal concentrations in the Spruce Forest ecosystems of the Boreal climatic zone is the subject of wide variation, with coefficient of variation from 36 to 330%. However, we can note the clear trend in biogeochemical peculiarities and relevant exposure to heavy metal uptakes by dominant plant species. 

Hudson, R. J. M. (1998). Which aqueous species control the rates of trace metal uptake by aquatic biota Observations and predictions of non-equilibrium effects, Sci. Total Environ., 219, 95-115. 

Fortin, C. and Campbell, P. G. C. (2001). Thiosulfate enhances silver uptake by a green alga role of anion transporters in metal uptake, Environ. Sci. Technol., 35, 2214-2218. 

Uptake of small organic metal complexes over transport systems of organic metabolites may be possible, for example, of small organic acids like citrate or amino acids. However, only few examples of such processes have been studied so far. Increased uptake of cadmium by an alga has been observed in the presence of citrate and has been attributed to accidental transport of the metal-citrate complex over a citrate transporter [212]. Transport systems of inorganic anions may also play a role in metal transport. Silver uptake by algae was enhanced in the presence of thiosulfate. In this case, the silver thiosulfate complex was transported over a sulfate uptake system [213]. It remains to be demonstrated how widespread these processes may be for metal uptake in the aquatic environment [12]. 

There is an abundant research on the interactions of HIOCs and metals with biological interphases, in which organic chemicals and metals are treated independently. However, few studies have considered the role of combinations of HIOCs with metals. There is a particular lack of mechanistic approaches. With regard to the metals, the FIAM has been very successful, but it remains to be shown under which conditions additional interactions, such as partitioning of hydrophobic complexes and uptake of specific complexes, are important for metal uptake and toxic effects. In particular, the role of hydrophobic complexes with both natural and pollutant compounds in natural waters has not yet been fully elucidated, since neither their abundance nor their behaviour at biological interphases are known in detail. 

The data were analysed using a kinetic model, proposed by Farringdon and Westall [30]. The equation for metal uptake in shrimp is as follows ... 

---