Factor soil depth profile

Cooper et al. (1994) have reported re-suspension studies on soils contaminated with plutonium during nuclear weapons tests by use of a mechanical dust-raising apparatus. Airborne dust was analysed in terms of mass and Am activities for particle sizes less than 7 pm. The AMAD was determined as 4.8-6 pm for re-suspended soil. Also, surface soil was characterised in the laboratory by means of sieving and microparticle classification, yielding mass and "Am activity distribution with respect to size. Data indicate the granularity of plutonium contamination at both major and minor trial sites. Depth profile analyses for undisturbed areas demonstrate that most (74% on average) of the americium and plutonium activity is found in the top 10 mm of soil. Plutonium and americium activities were found to be enhanced in the inhalable fraction over their values in the total soil, and the enhancement factors were similar in re-suspended dust and surface soil. Observed enhancement factors ranged from 3.7 to 32.5. 

Water leaves the field either as surface mnoff, carrying pesticides dissolved in the water or sorbed to soil particles suspended in water, or as water draining through the soil profile, carrying dissolved pesticides to deeper depths. The distribution of water between drainage and mnoff is dependent on the amount of water appHed to the field, the physical and chemical properties of the soil, and the cultural practices imposed on the field. These factors also impact the retention and transformation processes affecting the pesticide. 

The soil was loose and contained abundant spores with more genera above 0.4 m (Table 4, Fig. 6), and became denser due to the abrupt increasing in clay concentration below 0.4 m of SL profile (Chen et al. 2002a), which restrained the penetration of spores with leaching of soil water. Consequently, the quantity of spores decreased with depth (Table 4) and the genus became monotonous (Fig. 6). The loose/stiff quality of soil is then a critical factor controlling the penetration of spores. 

A typical field site, varying in area from about 1 to 10 ha, may include several soil series. The model parameter values may be different not only for each of these soil series, but may also vary considerably within a single series. Such variability in a number of soil hydraulic properties (e.g., soil hydraulic conductivity, soil water flux, etc.) has been widely reported in the literature ( 5 - 1 ). The model parameter values for a given location in the field may also vary with profile depth depending upon soil horizonation as well as a function of the soil and environmental factors (e.g., soil aeration, temperature, etc.). Since soil and environmental factors undergo dynamic changes with time, model parameters are also expected to exhibit temporal variability. At present, only limited data are available to characterize such spatial and temporal variability in pesticide sorption and degradation parameters required in several simulation models. 

Sods are a complex and usually heterogeneous matrix. Soil profile changes with depth typically within the first meter there are marked changes in type, composition, texture, moisture, and organic matter. In addition, there are usually changes in factors such as porosity and the proportion of organic matter of plant origin (for example leaf litter) within the first centimeter. 

For short-term or undrained loading analysis (( ) = 0) the factor N is zero and the factor N c is selected from Figure 10.43 for the anticipated relative embedment depth D/B and soil cohesion (a distance B above the anchor) in the soft rupture zone. The soil cohesion can be measured in place with a field vane or cone penetrometer or determined from laboratory tests on core samples such as the unconfined compression or triaxial CU test. If soil strength data are not available, the strength profile can be estimated using d CTot = 0.30, where the vertical effective stress (o J is estimated using a buoyant unit weight of 4 kN/m. ... 

Because of the diversity of nitrogenous compounds in soil organic matter, and their close associations with the biomass, it would be surprising if the distribution of N, both qualitatively and quantitatively, did not vary between different soils or indeed the same soil with increasing depth down the profile. Surprisingly, however, little is known of the factors vhich influence the distribution of nitrogenous compounds in soils and siabstantial variations in the distribution pattern have been reported. 

Another key factor in the drill path is the depth of the drill profile. The profile must be deep enough to ensure any obstacles are cleared by the desired distance. Also, a minimum depth for the drill path is required to ensure that no drilling fluid breakout occurs. For mini-HDD operations this depth is typically 3 feet or more, but this depends on the site-specific soil conditions. Normally, the bore profile arcs down from the entry point, then straightens out before it finally arcs back up to the exit point. 

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