Plant uptake, modeling

Often, the availability of the pollutants is not a limiting parameter under such conditions. Therefore, complementary approaches using pot and column experiments and field experiments, where the availability of the trace elements is an important parameter, should be performed to quantify the potential beneficial effect of AM presence or inoculation in polluted soils, and to provide useful data to include in plant uptake models. 

TBA), and 1,4-dioxane (Aitchison et al. 2000) in addition to the results of a recently published mechanistic plant uptake model (Trapp, 2007). 

In summary, phytovolatilization from both leaves and stems has been reported. However, the importance of phytovolatilization depends on both the properties of the chemical contaminant and the plant of interest. While phytovolatilization has been incorporated into several mechanistic plant uptake models such as that of Trapp (2007), additional experimental data collected under a variety of field settings are needed before the general significance of this process can be adequately assessed. 

Marschner H. Mineral Nutrition of Higher Plants, Academic Press, London, 1995. S. A. Barber and J. H. Cushman, Nitrogen uptake model for agricultural crops, Moiieling Waste Water Renovation—Land Treatment (I. Iskander, ed.), Wiley In-terScience, New York, 1981. pp. 382-404. 

R. B. Jackson and M. M. Caldwell, Integrating resource heterogeneity and plant plasticity modelling nitrate and phosphate uptake in a patchy soil environment. J. Ecol. 84 891 (1996). 

Figure 3. The general nitrogen model for illustrating the bio geochemical cycling in Forest ecosystems. Explanations for the fluxes 1, ammonia volatilization 2, forest fertilization 3, N2-fixation 4, denitrification 5, nitrate respiration 6, nitrification 7, immobilization 8, mineralization 9, assimilatory and dissimilatory nitrate reduction to ammonium 10, leaching 11, plant uptake 12, deposition N input 13, residue composition, exudation 14, soil erosion 15, ammonium fixation and release by clay minerals 16, biomass combustion 17, forest harvesting 18, litterfall (Bashkin, 2002).

Flutson, J.L. and Wagner, R.J. (1992) Leaching Estimation and Chemistry Model. A Process Based Model of Water and Solute Movement, transformation, Plant Uptake and Chemical Reactions in the Unsaturated Zone. Version 3. Dept, of Soil, Crop and Atmospheric Sciences, Series No. 92-3, Cornell University, Ithica, New York. 

Chiou, C. T., G. Sheng, and M. Manes, A partition-limited model for the plant uptake of organic contaminants from soil and water , Environ. Sci. Technol., 35, 1437-1444 (2001). 

Sabljic, A., H. Glisten, J. Schonherr, and M. Riederer. 1990. Modeling Plant Uptake of Airborne Organic Chemicals. 1. Plant Cuticle/Water Partitioning and Molecular Connectivity. Environ. Sci. Technol. 24, 1321-1326. 

Wagenet, R.J. and J.L. Hutson (1989). LEACHM Leaching estimation model - a process based model for water and soute movement, transformation, plant uptake and chemical reactions in the unsaturated zone. Continuum Vol. 2. Water Resources Institute, Cornell University Ithaca, NY. 

This model assumes irreversible first-order kinetics for nitrification, denitrification, mineralization, immobilization, and plant uptake. It takes the following form, in which sinks and sources are aggregated ... 

Tillotson et al. (1980) Nitrification and urea hydrolysis by first-order kinetics NH3 volatilization by first-order kinetics from (NH4)2C03 formed from urea hydrolysis NH sorption by linear partition model NH and NOy plant uptake involving diffusion to roots. 

Behrendt, H., Bruggemann, R. (1993) Modelling the fate of organic chemicals in the soil plant environment model study of root uptake of pesticides. Chemosphere 27, 2325-2332. 

Sabljic, A., Glisten, H., Schonherr, J., and Riederer, M., Modeling plant uptake of airborne organic chemicals. Plant cuticle/water partitioning and molecular connectivity, Environ. Sci. Tech., 24, 1321-1326, 1990. 

While this equation was obtained for compounds that are somewhat more volatile than the PCDD/Fs, it is consistent with theoretical models of plant uptake of SOCs40 43 and it would seem reasonable to extrapolate it to the PCDD/Fs. 

In a first series of experiments Avena sativa, which had been a weed in rye fields before it became a so called secondary crop, Triticum aestivum and Vida faba L. roots or whole plants as model systems were incubated in presence of BOA [179]. All the three species were able to absorb the substance when 100 pM were applied. With 500 pM BOA Vicia faba failed in taking up and root tips were killed by the compound as indicated by blackening during the course of incubation. The cereals were still able to absorb BOA, Triticum aestivum without and Avena sativa with a lag phase of 10 - 15 h. In Avena sativa the uptake seems to be an active process, which succumbs under oxygen deficiency and, as ascertained by incubations in presence of only IpM BOA, takes place against the concentration gradient (Schulz and Wieland, unpublished). 

Hutson JL, Wagenet RJ. LEACHM Leaching estimation and chemistry model. A process-based model of water and solute movement, transformations, plant uptake and chemical reactions in the unsaturated zone. Version 3. Ithaca, NY Department of Soil, Crop and Atmospheric Sciences. Research series no. 92-3, Cornell University, 1992. 

Plant uptake. Pesticide uptake by plants has not been considered in most modeling efforts. This is primarily due to an almost total lack of quantitative experimental information available to the modeler, and the presumption that the absolute mass of pesticide absorbed by the plant is small compared to the mass remaining in the system. Due to these considerations, modelers have apparently assumed that any inaccuracy in simulation of pesticide fate that results from not considering plant uptake is within the "noise" of inaccuracies produced by other assumptions about the physical, chemical, and biological processes operating in the system. While this assumption is unproven for pesticide absorption, it clearly cannot be accepted for water absorption by the plant (the U(z,t) term in Equation 4). Plant extraction of water greatly influences water flux, which affects pesticide... 

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