Soils other factors

The most important factor influencing the uptake of strontium by plants is the Ca status of the soil, other factors include the pH and organic matter content. Lem-brechts et al. (1990) have investigated the relation between soil solution composition and 85Sr uptake by young lettuce plants. A close relationship was shown between the Sr concentrations in the plants and the Sr/Ca ratio in solution either in nutrient medium, or in soil solution. It was suggested that plants primarily withdraw their nutrients from the soil liquid phase. 

In addition to soil factors such as texture and structure controlling water movement within a given soil, other factors include temperature, water content, and salt composition and concentration. For example, the data in Figure 10.1 show that as temperature increases, hydraulic conductivity also increases, perhaps because of increasing water fluidity. Furthermore, hydraulic conductivity increases as water content increases. The data in Figure 10.2 demonstrate that as salt concentration increases, hydraulic conductivity also increases, a phenomenon linked to the electric double layer (Chapters 3 and 9). 

In MichaeUs-Menton kinetics, the order varies between first and zero with increasing concentration, and the equilibrium accumulation of residue increases rapidly as the annual rate of addition approaches the maximum decomposition rate for the soil. Other factors such as volatility, side reactions, etc., may lead to complex kinetics, and it is suggested that usable rate law expressions could be obtained empirically. 

Besides the composition of the soils, other factors have a major influence on the migration of radionuclides rainfall, the thickness of the soil layers, their permeability to water, and the nature of the layers underneath. For example, Cs is washed down quickly through layers of sand, but it will stay in layers of clay. Pu is sorbed by clay more strongly than by sand and may stay in soils for rather long times, if it is not dissolved by complexation or displaced by other compounds. 

In water several types of materials may affect the bioavailability, such as dissolved organic carbon (DOC), particulate organic carbon (POC), etc. In sediment and soil, other factors affect the bioavailability of organic compounds, such as the hydrophobicity of the contaminant, the contact time between contaminant and soil/sediment, the nature and amount of organic carbon and other soil/sediment characteristics, the behaviour of soil/sediment organisms, etc. [85]. Bioavailability may thus lead to an apparently lower BCF. 

Dividing the nitrate problem into topics is inevitably a somewhat arbitrary process, because of the interactions between the nitrogen fertilizer and the other factors . The various crops, for example, could arguably have come in this section rather than Section 2, while the structure of the soil, discussed in this Section,... 

Seismie analysis is carried out for all important engineering structures such as dams, bridges and nuclear power plants. For regions where these are to be located the likely expectations of an earthquake as well as the extent of its magnitude must be assessed on the basis of the seismic history and the earthquake records of the region (Figures 14.12 to Figure 14.16). Based on these and other factors such as soil stratification, site dependent response spectra are determined. These are the RRS for equipment mounted... 

The extent and severity of the damage attributable to acid depositions are difficult to estimate, since impacts vary according to soil type, plant species, atmospheric conditions, insect populations, and other factors that are not well understood. Nitrates in precipitation may actually increase forest growth in areas with nitrogen-deficient soils. 

The documentation of regional level terrestrial consequences of acid deposition is complicated. For example, forested ecosystems m eastern North America can he influenced by other factors such as high atmospheric ozone concentrations, drought, insect outbreaks and disease, sometimes from non-native sources. However there is a general consensus on some impacts of acidic depositon on both soils and forests m sensitive regions. 

Soil is distinguished by the complex nature of its composition and of its interaction with other environmental factors. No two soils are exactly alike, and extremes of structure, composition and corrosive activity are found in different soils. Climatic factors of rainfall, temperature, air movement and sunlight can cause marked alterations in soil properties which relate directly to the rates at which corrosion will take place on metals buried in these soils. 

No corrosion occurs in a completely dry environment. In soil, water is needed for ionisation of the oxidised state at the metal surface. Water is also needed for ionisation of soil electrolytes, thus completing the circuit for flow of a current maintaining corrosive activity. Apart from its participation in the fundamental corrosion process, water markedly influences most of the other factors relating to corrosion in soils. Its role in weathering and soil genesis has already been mentioned. 

As with other factors, no direct statements can be made relating the reaction of a soil to its corrosive properties. Extremely acid soils (pH 4 0 and lower) can cause rapid corrosion of bare metals of most types. This degree of acidity is not common, being limited to certain-bog soils and soils made acid by large accumulations of acidic plant materials such as needles in a coniferous forest. Most soils range from pH5 0 to pH8 0, and corrosion rates are apt to depend on many other environmental factors rather than soil reaction per se. The 45-year study of underground corrosion conducted by the United States Bureau of Standards included study of the effect of soils of varying pH on different metals, and extensive data were reported. 

Regulations and recommendations can be expressed in not-to-exceed levels in air, water, soil, or food that are usually based on levels that affect animals then they are adjusted to help protect people. Sometimes these not-to-exceed levels differ among federal organizations because of different exposure times (an 8-hour workday or a 24-hour day), the use of different animal studies, or other factors. 

Other factors are fretting and cavitation in a liqnid (impact of the liqnid). Corrosion can also occnr dne to electric cnrrents (stray cnrrents in soils). 

For this reason, process-based whole-farm simulators have been developed. The simulators comprise modules containing semiempirical equations and mechanistic models that account for soil type, crops grovm, climate, herd size, manure handling, and other factors for a variety of farms as well as modules that calculate GHG emissions, other types of... 

The second important point is that although factors that affect herbage production, such as climate, latitude and aspect, are outside the farmer s control, other factors, such as soil nutrient level and grazing management, can be controlled by the skilful farmer. 

Other factors affecting performance include the presence of toxic material, the redox potential, salinity of the groundwater, light intensity, hydraulic conductivity of the soil, and osmotic potential. The rate of biological treatment is higher for more permeable soils or aquifers. Bioremediation is not applicable to soils with very low permeability, because it would take a long time for the cleanup process unless many more wells were installed, thus raising the cost. 

The soil and plants employed on the cover are critical to success. A mixture of grasses native to the area is preferred to provide effective water removal from the cover in all years in spite of temporary changes in local conditions. Native grasses have already proven their ability to withstand local climate variations, insects, plant disease, periodic fire, and other factors. A mixture of native grasses assures an active vegetative cover during years when insects, plant disease, or other factors reduce the vigor of one or more species.11-38... 

Studies of the transfer of radiocerium into various plant parts via the soil-root pathway are summarized in Table 6. Other laboratory and field studies employing tracer radiocerium or nuclear weapons fallout simulants are summarized in Tables 7 and 8. In general, the cereal grains and vegetable pulp showed plant-to-soil concentration factors (radioactivity per gram of dry plant material/radioactivity per gram of... 

Table 6—Plant-to-soil concentration factors for li4Ce and other rare earth isotopesb...

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