Environment mobile chemicals

Degradable Plastics and the Environment, Mobil Chemical Company, 1988. 

In the biosphere, vanadium can be considered to be of two forms, one of which is highly mobile, whereas the other is a virtually immobile form. These are closely connected to the oxidation state of vanadium, where the mobile chemically reactive form conforms more or less, but certainly not exclusively, to the V(V) oxidation state. This is the state that vanadium will predominantly have in gas effluents in ash from oil, coal, and gas burners in some minerals and in surface water. Vana-dium(IV) complexes of the types found in minerals will often be relatively immobile but, if subjected to an oxidative environment, can enter the mobile phase in the V(V) oxidation state. Sequestered forms of vanadium can be transported by mechanical processes such as by movements of suspended materials in creeks and rivers, where translocation from terrestrial to lake or marine environments accounts for a high percentage of the movement of vanadium. This procedure does not release the vanadium into the environment in the sense that release from the substrate does rather, the vanadium is simply redeposited as the sediments settle. However, because of the high surface area of the suspended materials, vanadium can efficiently be removed from the suspended material by chemical reactions and enter into the environment as active species by this process. 

Release of 2-acetylaminofluorene to the environment from artificial sources is probably not significant since less than 20 lb year of this compound are consumed in the United States. If released to soil, 2-acetylaminofluorene is expected to have low mobility. Chemical hydrolysis, oxidation, and volatilization are not expected to be significant. If released to water, 2-acetylaminofluorene may undergo direct photolysis and is expected to strongly... 

The actual secondary mineral products formed are determined by the relative rates of these weathering reactions at the surface of the particular primary mineral, by the relative rates of crystallization of possible metastable and stable secondary minerals, and by the extent to which the soil environment allows mobile chemical components to be lost by leaching. ... 

Although the laboratory experimental evidence is considerable, there have been to date no comprehensive field-scale studies of pesticide movement under natural conditions. In fact, until 10 years ago there were virtually no studies of water or mobile chemical transport in the natural field environment. 

Environment Agency Chemical Business Association Exxon Mobil Simon Storage... 

From polarization curves the protectiveness of a passive film in a certain environment can be estimated from the passive current density in figure C2.8.4 which reflects the layer s resistance to ion transport tlirough the film, and chemical dissolution of the film. It is clear that a variety of factors can influence ion transport tlirough the film, such as the film s chemical composition, stmcture, number of grain boundaries and the extent of flaws and pores. The protectiveness and stability of passive films has, for instance, been based on percolation arguments [67, 681, stmctural arguments [69], ion/defect mobility [56, 57] and charge distribution [70, 71]. 

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. 

Adsorption — An important physico-chemical phenomenon used in treatment of hazardous wastes or in predicting the behavior of hazardous materials in natural systems is adsorption. Adsorption is the concentration or accumulation of substances at a surface or interface between media. Hazardous materials are often removed from water or air by adsorption onto activated carbon. Adsorption of organic hazardous materials onto soils or sediments is an important factor affecting their mobility in the environment. Adsorption may be predicted by use of a number of equations most commonly relating the concentration of a chemical at the surface or interface to the concentration in air or in solution, at equilibrium. These equations may be solved graphically using laboratory data to plot "isotherms." The most common application of adsorption is for the removal of organic compounds from water by activated carbon. 

Research into the aquatic chemistry of plutonium has produced information showing how this radioelement is mobilized and transported in the environment. Field studies revealed that the sorption of plutonium onto sediments is an equilibrium process which influences the concentration in natural waters. This equilibrium process is modified by the oxidation state of the soluble plutonium and by the presence of dissolved organic carbon (DOC). Higher concentrations of fallout plutonium in natural waters are associated with higher DOC. Laboratory experiments confirm the correlation. In waters low in DOC oxidized plutonium, Pu(V), is the dominant oxidation state while reduced plutonium, Pu(III+IV), is more prevalent where high concentrations of DOC exist. Laboratory and field experiments have provided some information on the possible chemical processes which lead to changes in the oxidation state of plutonium and to its complexation by natural ligands. 

Wiesner MR, MC Grant, SR Hutchins (1996) Reduced permeability in groundwater remediation systems role of mobilized colloids and injected chemicals. Environ Sci Technol 30 3184-3191. 

Partition processes determine how a substance is distributed among the liquid, solid, and gas phases and determine the chemical form or species of a substance. Partitioning usually does not affect the toxic properties of the substance. Partitioning can, however, affect the mobility of the waste, its compatibility with the injection zone, or other factors that influence fate in the deep-well environment. The major partition processes are as follows ... 

Finally, the third major input information required is external (i.e., extrinsic to the compound itself) the environmental physical conditions (see Fig. 2). Temperature and water regimes are often the most determinant factors which affect the mobility of chemicals in the environment by accelerating volatilization or sorption processes. Solar radiation is also crucial in the chemicals fate since it is strongly related to photodegradation and volatilization processes as well. 

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