Soil uptake

Since we do not expect the amount of hydrogen released to change very significantly in the next few decades, we currently have no reason to expect serious consequences from changes in the soil uptake rate. This is rather speculative, however, and further research is urgently required. 

The value of CF for lead is lower than for most metals and is typically within the range 10 — 10. Much higher values had been estimated from earlier studies, which ignored the importance of direct atmospheric deposition as a pathway for contamination. The direct input from the air to leaves of plants is often as great, or greater than soil uptake. This pathway may be described by another transfer factor, termed the Air Accumulation Factor (AAF), where... 

Snover A. K. and Quay P. D. (2000) Hydrogen and carbon kinetic isotope effects during soil uptake of atmospheric methane. Global Biogeochem. Cycles. 14, 25-39. 

Using the methods described by the CDC and the EPA, a preliminary evaluation of the need for clean-up at a given site can be readily conducted. In Case I, we followed the CDC assessment procedure but updated a few of their values. Specifically, in these calculations we used [a] a soil uptake of 100 mg/day (ages 2-6), and negligible soil ingestion for the rest of the lifetime [b] 0% oral, and 1% dermal bloavallabllIty ... 

The U.S. could, for instance, substantially offset its electricity, transportation, and industrial emissions by reporting carbon absorption due to agricultural soil uptake as well as forest growth. Europeans, however, are skeptical about measurement and verification of such sinks. They also argue that they are being penalized... 

The ocean acts as both a source and sink for CH3Br the net oceanic flux to the atmosphere is negative, estimated as —21 Ggyr-1 (Table 2.17). Oceanic uptake of CH3Br is currently estimated at 77Ggyr . Combined with atmospheric OH reaction and photolysis (86Ggyr ) and soil uptake (46.8Ggyr-1), this leads to a total estimated... 

Vapor-phase sorption onto the same dry Woodbum soil is illustrated in Figure 3.16 where soil uptake is expressed as a function of the relative pressure-equilibrium partial pressure/saturated vapor pressure. The data indicate a BET adsorption process. Increasing relative humidity decreases the adsorption (Fig. 3.17) of dichlorobenzene ultimately resulting in a linear isotherm. It is concluded that at low humidities adsorption on the mineral surfaces is involved. Increasing availability of water reduces the availability of these sites until sorption is due to partitioning into the SOM. It will be demonstrated that the converse of this relation is important in assessing the potential for evaporative loss from soils. 

To give an overview of mathematical models used to describe rhizosphere processes, including transport of ions in soil, uptake by plant root, root exudation and chemical equilibrium and non-equilibrium sorption. 

Claassen, N., 1990. Fundamentals of sod-plant interactions as derived from nutrient diffusion in soil, uptake kinetics and morphology of roots. Proceedings of the Fourteenth International Congress of Soil Science, Kyoto, Japan, vol. 11, pp. 118-123. 

Particularly on PET fibers, cotton, and various blends, ttie data in Table IS on soil uptake (SAD) and soil left after ten of soiling and wadiing (GAD) were recorded by Byme with dirt formed from fatty matter and Aist or only from dust. 

Temp, of heat-setting "C Crystallinity % BW % Fatty soil uptake AW... 

Soil uptake (55 Tg yr i) represents a major loss process for H2 and contributes 80% of the total destruction. H2 oxidation by OH in the troposphere contributes the remainder. The global burden of H2 in the atmosphere is 136 Tg. Its overall lifetime in the atmosphere is 1.9 years (Hauglustaine and Ehhalt 2002). H2 is rather well mixed in the free troposphere. However, its distribution shows a significant seasonal variation (Fig. 2.90) in the lower troposphere where soil uptake dominates. This loss process shows a strong temporal variability and is maximal during summer. 

The main sink (besides soil uptake) of molecular hydrogen is the relatively slow reaction with OH ks.3 = 7.7 at 298 K) ... 

Hartley 46) speculated that a solvent action of the oily constituents of the organic matter might be important for soil uptake. Swoboda and Thomas 98) expressed a similar view in their study of parathion on soil. The chromatographic sorption model of Lambert (59) is compatible with the idea of solute partitioning between soil organic matter and water. 

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