Experimental and modeling studies on solute transport and extraction by a single root /
The fate of ¹⁴C-TNT (2,4,6-trinitrotoluene) in the soil/plant system was studied using onion plants that had developed only a single root. The single root grew exponentially and the rate of water uptake increased linearly with time. TNT concentrations in the root increased and then appeared to maint...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2001.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=725911951&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The fate of ¹⁴C-TNT (2,4,6-trinitrotoluene) in the soil/plant system was studied using onion plants that had developed only a single root. The single root grew exponentially and the rate of water uptake increased linearly with time. TNT concentrations in the root increased and then appeared to maintain a steady state, but in the leaf increased linearly with time. TNT concentration in the rhizosphere increased gradually, but in the bulk soil decreased slowly, reaching a steady state in the end. More TNT movement through mass flow than TNT uptake by the root induced TNT accumulation in the rhizosphere. The distribution of TNT in the soil-root system was 60-85% in the soil solid phase, 7-11% in the soil liquid phase, < 1% in the soil air phase, < 1% in the root compartment, and < 0.01% in the leaf compartment. The uptake of ¹⁴C-TNT was also examined in hydroponics. Of the total TNT (5 [u]M concentration), 75% was in the roots, 4.4% in the leaves, and 21% in the external solution at 2 days. Percent of distribution in roots was lower with higher concentration in external solution, but in leaves was comparable at all concentrations (5-500 [u]M). In soil, the maximum RCF (root concentration factor) value for TNT was around 20 in the single root system, and in hydroponics was more than 85 in CHE (constant hydroponic experiment) at 5 [u]M. The maximum RCF values in the hydroponic system were greater with lower solution concentration. Those RCF values did not match well with predicted values (= 1.7-3.5) derived in the literature from equations using log K[ow] ([log]₁₀ octanol-water partition coefficient). The maximum TSCF (transpiration stream concentration factor) in the single root system was 0.18, which is lower than prior reported values (= 0.43-0.78). For the NHE, the range of values was 0.31 to 0.56, increasing with higher external concentration. For phytotoxicity tested in hydroponics and wet paper method, 500 [u]M was toxic to onion plant, 50 [u]M was non-toxic for plant growth but limited the transpiration rate, and 5 [u]M was non-toxic. The mathematical model presented in this study focused on investigation of the fate of TNT in the single root system in soil. All modeling output closely matched with the data from an actual experiment. Additionally, the model was used to extrapolate beyond the experimental time period and also to provide information on the likely value of various parameters that could not be measured experimentally. |
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| Item Description: | Vita. "Major Subject: Civil Engineering". |
| Physical Description: | xvi, 142 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 134-142). |