Uptakes, of trace elements

Plants show different abilities of uptake of trace elements. Lettuce and rape usually have a higher capacity for the uptake of trace elements than do cereal plants. Grant and Bailey (1997) reported that flax tended to... 

Despite the quantitative variability of salts and silicate dust particles in the plants of Arid ecosystems, we can easily discern a trend towards the selective uptake of trace elements. The calculation of coefficient of biogeochemical uptake (Cb) shows the rates of exposure to heavy metals in biogeochemical food webs. One can see that the elements contained in the plant species of both Steppe and Desert ecosystems are in equal measure susceptible to the influence of environmental factors. The most extensively absorbed are Sr, Cu, Mo, and Zn. Their values of Cb are more than unit. The group of other elements, like Ti, Zr, and V, are poorly taken up, with their values of Cb often dropping below 0.1 (see Figures 4 and 5). 

Dreesen, D. R. Marples, M. L. 1979. Uptake of trace elements and radionuclides from uranium mill tailings by four-wing Saltbush (Atripliex canescens) and Alkali Sacaton (Sporobolus air-oides). Proc. Second Symposium on Uranium Mill Tailings Management, Fort Collins, CO, USA, 19-20 November 1979, 127-143. 

Many fertilisers for the treatment of deficiencies of trace elements are added to the leaves. In addition, uptake of trace elements from aerial sources through the leaves may have a significant impact on plant contamination, especially of elements such as Fe, Mn, Zn and Cu. Anthropogenic aerosols have been reported to bring about foliar deposition of Pb to a great extent (Streit and Stumm, 1993). Zieve and Peterson (1984) have reported the assimilation of diemethyl selenide through leaves of terrestrial plants. Roberts et al. (1975) found a significant absorption of foliar-applied Zn, Fe, Cd and Mg. 

L. Samspe-Petersen, E. H. Larsen, P. B. Larsen, P. Braun. Uptake of trace elements and PAHs by fruit and vegetables from contaminated soils, Env. Sci. Technol, 36 (2002), 3057-3063. 

The uptake of trace metals from the soil by plants and animals can be studied with high sensitivity by radiotracer techniques. In these applications, it is important that the chemical form of the radiotracer is identical with that of the trace element to be studied. For example, in agriculture, the uptake of trace elements necessary for plant growth can be investigated. Essential trace elements, such as Se, are of special interest. By use of radioactively labelled selenium compounds the transfer of this element from soil to plants and animals can be measured. For the investigation of the transfer of radionuclides (radioecology), addition of tracers is, in general, not needed. 

Finally, finely divided hydrous oxides of iron, aluminum, manganese, and silicon are the dominant sorbents in nature because they are common in soils and rivers, where they tend to coat other particles. This is the reason why numerous laboratory researchers have been studying the uptake of trace elements by adsorption on hydrous oxides (Dzomback and Morel, 1990). Partition coefficients (concentration in solid/concentration in the solution) for a number of trace elements and a great variety of surfaces have been determined. The comparison of these experimental with natural values should give information on the nature of the material on which trace elements adsorb in namral systems and allow quantitative modeling. 

Finally, one should not end this section without mentioning the uptake of trace elements by hving biomass. This process can be of quantitative importance in river systems of low velocity or draining lakes or stagnant water bodies. For example, a study in the St. Lawrence river (Quemerais and Lum, 1997) has shown that an... 

Despite the quantitative variability of salts and silicate dust particles in the plants of Arid ecosystems, we can easily discern a trend towards the selective uptake of trace elements. The calculation of coefficient of biogeochemical uptake (Cb) shows that the elements contained in the plant species of both Steppe and Desert ecosystems are in equal measure susceptible to the influence of environmental factors. The most... 

If one assumes that other elements are transported by the atmosphere from urban centers in a manner similar to that of lead, and are subsequently deposited on the ocean surface and mixed vertically at a rate similar to that of lead, then the expected increase in ocean water concentrations of other elements can be calculated (Table 4). The most probable values show increases of 30% (Table 1) for several of the elements, although higher concentrations may exist. The values of the most probable increases suggest that trace elements in the surface layers bear little relationship to the concentration of elements found in organisms. The uptake of trace elements by the marine biota, however, does depend upon the chemical state of the elements, and we shall discuss this further in the later sections. 

Extensive progress has been made in our understanding of the mechanisms and external factors which control the uptake of trace elements by plants under various conditions. However, prediction of the phy-toavailabUity of trace elements - and espe-... 

To study how living species interact with the environment, ecology, one can use radioactive tracers to follow the uptake of a trace metal (e.g. cobalt) from the soil by plants, and by animals after having eaten the plant. In agriculture, this is useful in studying the uptake of trace elements necessary for plant growth. For exan >le, it has been found that sheep need plants containing selenium in order to combat white muscle disease. The... 

Aerosol work has also profited from micro-PIXE, as single particle analysis has become feasible. Accurate correlation between the chemical composition of such particles and their size and shape provides information about the sources of the particles and about the transformations that take place during atmospheric transport. In other environmental studies, micro-PIXE has been used to measure the uptake of trace elements in plants, roots, and trees. In parti cular, tree rings, which also record time information, have been analyzed in several laboratories. 

Mitchell [296] has published data for the trace-element contents of red clover and ryegrass grown on 15 different soils in north-east Scotland and the variations in the levels of copper, manganese, molybdenum, nickel and zinc are less than sevenfold. The variation in copper and zinc levels in both plant species is actually less than twofold and it is clear that plants have some capacity to regulate their uptake of trace elements and that the main effect is to damp down the consequences of variation in concentration in soil solutions, so that the range of uptake of most elements is restricted. Availability in soil appears to be as much a plant function as a physico-chemical soil property. 

Dowdy and Larson [343] studied the uptake of trace elements by seven vegetable crops (carrot, lettuce, peas, potatoes, radishes, sweet corn and tomatoes) from sludge-treated soil in field conditions and concluded that, in general, metals accumulate in vegetative tissue. Among the crops studied, lettuce was exceptional in the extent to which uptake was increased on contaminated soil, and about fourfold, sevenfold and tenfold increases in plant cadmium, copper and zinc respectively, were observed on adding 450 tonnes sludge/ha. 

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