Concentration in soil

As mentioned earlier, there is an inverse relationship between water volumes and oxygen concentration in soil. As soils dry, conditions become more aerobic and oxygen diffusion rates become higher. The wet-dry or anaerobic-aerobic alternation, either temporal or spatial, leads to higher corrosion rates than would be obtained within a constant environment. Oxygen-concentration-cell formation is enhanced. This same fluctuation in water and air relations also leads to greater variation in biological activity within the soil. 

House dust. Houses are enclosed spaces and tend to accumulate dust from the outside. There are also internal sources of house dust. The concentration ratio [MJhouse dust/[M]soil has a mean of 0.33 (standard deviation = 0.09) for the ten elements Mn, Fe, La, Sm, Hf, Th, V, Al, Sc and Ce suggesting that around 33% of house dust is soil (93). The concentration ratio for the two surface dusts, [M]house dust/[M]street dust is >1 for the elements Cu, Co, As, Sb, Zn, Cd, Au, Cl and C suggesting these elements also have an internal component. All of these elements, as well as Pb and Br, are enriched in house dust relative to their concentrations in soil. Lead and bromine originate mainly from outside the house, and probably from street dust and motor vehicle emissions and, in the case of lead, from paint. When the concentrations of lead in house dust are very high this generally signifies an internal source of lead paint, especially in older houses. 

Rao PS, Davidson JM. 1979. Adsorption and movement of selected pesticides at high concentrations in soils. Water Res 13 375-380. 

Carey AE, Douglas P, Tai H, et al. 1979a. Pesticide residue concentrations in soils of five United States cities, 1971-Urban Soils Monitoring Program. Pestic Monit J 13 17-22. 

In marked contrast to hydrophobic compounds, more polar ones tend to be less adsorbed and to reach relatively high concentrations in soil water. Phenoxyalkanoic acids such as 2,4-D and MCPA are good examples (Figure 4.3). Their half-lives in soil are measured in weeks rather than years, and they are more mobile than OC insecticides in soils. When first applied they are lost only slowly. After a lag period of a... 

As water moves through the soil pores in response to water potential gradients, it moves with it the solutes dissolved in soil solution. In a rhizosphere context, water moves radially toward the root to replace water taken up by the roots for transpiration. The flux of solute due to water movement (7 .) is simply the product of the rate of water flow at that point and the concentration in soil solution ... 

Assuming proper soil surface preparation (i.e., smooth with no soil clods or crop debris) and test substance application, the diameter of the soil probe does not generally impact observed pesticide residue concentrations in soil or associated variability. Nevertheless, a minimum diameter of 5 cm for the upper soil probe is recommended to improve sampling under less than ideal conditions. Increasingly, researchers are using probes having diameters >5 cm with good results under a variety of field conditions. 

When a single organic compound is present in the soil matrix as NAPL, its concentration in soil air (Ca) can be directly calculated from the vapor pressure of this compound (P°) and the Ideal Gas Law ... 

Lead at a lightly contaminated brownfield site has a concentration in soil of 600 mg/kg to a depth of 1 ft. The cleanup standard has been set at 400 mg/kg. Indian mustard, Bmssica juncea, will be planted, fertilized, and harvested three times each year for phytoextraction. Using small doses of EDTA, it is possible to achieve concentrations in the plant of 5000 mg/kg (dry weight basis), and harvestable densities of 2.721 (3 short tons) dry matter per crop. Estimate the time required for cleanup ... 

Density of OCP flux OCP concentration in soil from atmosphere, surface layer, in mkg/kg g/km2 per year of dry mass... 

Nouchi I, Hosono T, Aoki K, Minami K. Seasonal variation in methane flux from rice paddies associated with methane concentration in soil water, rice biomass and temperature, and its modeling. Plant Soil. 1994 161 195-208. 

FUN Tool. Depending on the complexity of the scenario, the 2FUN Tool calculates the concentration in soil, water, vegetables (leaf and root), cereals, fruits, animal products (milk and beef), and fish. 

Strong correlations occur between concentrations of trace elements in Californian soils. Nickel concentrations in soils are strongly correlated with Cr (r = 0.95) Cu contents are also significantly correlated with Co (r = 0.81). Strong correlations between Ni and Cr and between Cu and Co are observed as well (Marrett et al., 1992). This strong correlation between trace elements indicates that these elements associate in parent materials and suggests similar physical-chemical processes governing soil formation (Bradford et al., 1996). 

Northern Californian soils have higher concentrations of Cr, Co, Cu and Ni than southern California since there are volcanic ultramafic rocks in northern California. Ultramafic rocks are mostly serpentine, a magnesium silicate with associated high amounts of Ni and Cr. Soils formed on serpentine parent materials contain high to extremely high Ni and Cr concentrations in soils. Soil parent material is a factor mostly controlling trace element concentrations in soils. 

In eight contaminated soils with pH 7.05-8.20 from eastern and southern Australia, soluble Zn, Cu and Cd concentrations in soil pore water are 0.19-422, 36-4840, and 7.2-4260 pM, respectively (Nolan et al., 2003). 

Trace element speciation in soil solution is affected by total metal concentrations in soils. Free Cu2+ activity increases with total Cu content in soils from Quebec and New York (Sauve et al., 1997). Total free Cu activity in soils could be predicted from total Cu content and soil pH ... 

---