Soils high-level

Sample Concentration (Purge and Trap Medium and High Level Soil)... 

Approximate detection limit in high-level soil and sludges. 

The phenoxy-herbicide, 2,4-D, has been successfully bioremediated in a soil contaminated with such a high level of the compound (710 ppm) that it... 

Phytoremediation is also being developed for dealing with soils contaminated with high levels of selenium in California again B.juncea seems to be particularly effective in accumulating the contaminant from soil, and all plants tested were more effective at removing selenate than selenite (92). This is an interesting contrast to bacterial systems, where selenite reduction is more commonly found than selenate reduction. 

Preventive Measures. The intake uptake biokinetic model (lUBK) projects the impact of lead in the environment on blood lead. This model assumes conservatively high levels of intake and cannot account for chemical speciation, thus over-predictions of blood lead levels often occur. Nonetheless, because of the allegations of the impact of blood lead and neurobehavioral development, blood lead levels in children are being reduced adrninistratively to below 10 //g/dL. In order to do so, soil leads are being reduced to a level of between 500—1000 ppm where remediation is required. 

Information on the toxic effects of molybdenum in humans is scarce. A high incidence of gout was reported in a locale in Armenia where the soil contained exceptionally high levels of both molybdenum and copper (15). However, the significance of the suggested correlation is questionable because of the lack of information on the study population and the absence of a control group. 

A variety of shale-protective muds are available which contain high levels of potassium ions (10). The reaction of potassium ions with clay, well known to soil scientists, results in potassium fixation and formation of a less water-sensitive clay. Potassium chloride, potassium hydroxide, potassium carbonate [584-08-7] (99), tetrapotassium pyrophosphate [7320-34-5] (100), and possibly the potassium salts of organic acids, such as potassium acetate [127-08-2] (101) and formate, have all been used as the potassium source. Potassium chloride is generally preferred because of its low cost and availabihty. 

Photosynthesis and gas exchange of leaves are affected by many stresses including drought, flooding, salinity, chilling, high temperature, soil compaction and inadequate nutrition. Many, but not all, of these stresses have symptoms in common. For example, stomatal conductance and the rate of assimilation of CO2 per unit leaf area often decrease when stress occurs. Further, it is possible that several of the stresses may exert their effects, in part, by increasing the levels of the hormone abscisic acid (ABA) in the leaf epidermis. This hormone is known to close stomata when applied to leaves. 

Fulthorpe RR, AN Rhodes, JM Tiedje (1998) High levels of endemicity of 3-chlorobenzoate-degrading soil bacteria. Appl Environ Microbiol 64 1620-1627. 

Sanchez MA, M Vasquez, B Gonzalez (2004) A previously unexposed forest soil microbial community degrades high levels of the pollutant 2,4,6-trichlorophenol. Appl Environ Microbiol 70 7567-7570. 

Sometimes it is impossible to effectively design out waste, and safe means have to be found to dispose of it. Many industrial processes produce relatively high levels of waste in a finely divided or dispersed form, such as ash, contaminated soil, treatment sludges, and so forth. This contaminated material is difficult to handle and process. A common approach to tackling this problem is to stabihse and sohdify the waste using a binder that immobilises contaminants within a hard matrix. This does not destroy the contaminants, but keeps them from moving into the surroimding environment. 

Figure 9 Proposed role of organic acid metabolism (citrate) in genotypical differences of rice in adaptation to high levels of soil bicarbonate tmd low Zn availability. (Adapted t rora Ref. 233.)...

---