COE Seminar
Title:Interactions and fractionations at the interface atmosphere-soil-water-plant-bacteria;
REE, Nd-Sr-Pb isotope evidence.
Speaker:Prof. Peter Stille
Affiliation:CNRS/Strasbourg University（France)
Date & Time: 14:10-15:10 on Thursday, Oct 5, 2006
Place:Chigaku-Seibutsu Kyotsu Kogishitsu
(Earth Science Biology LectureRoom, Faculty of Science)
Abstract:
The aim of the here presented studies was to experimentally evaluate the degree of trace element and especially REE-actinide enrichment in plants, to examine the influence of bacteria on the plant growth and the REE enrichments in plants, and to test the stability of municipal inicinerator bottom ash waste glasses in the presence of bacteria and plants. Data of two different laboratory experiments with and without bacteria and with and without corn plants are compared with data from a natural forested catchment.
In the first laboratory experiment we compared the stability of natural basaltic glasses and artificially produced waste glasses (vitrified nuclear and domestic waste) in solutions with and without bacteria (Pseudomonas aeruginosa). The preliminary data suggest that all the glasses appear to be more stable under the presence of this type of bacteria probably due to the formation of a protecting biofilm.
For the second experiment a soil has been mixed up with a <100m grain size fraction of the vitrified incinerator bottom ash. This soil has then been used as a substratum for plant growth and added to two different boxes where corn has been grown up with Pseudomonas aeruginosa and without bacteria. The results show that inoculated plant samples contain always about two times higher lanthanide and actinide element concentrations. Bacteria support the element transfer. Compared with the substratum, plants are light REE enriched. This enrichment is not bacteria induced but caused by plants metabolism. The vitrified bottom ash has to some extent been corroded by bacteria and plant activities as indicated by the presence of REE and Sr from the vitrified waste in the plants: 87Sr/86Sr and 143Nd/144Nd isotope ratios of plants and soil components allow the identification of corroded soil components and confirm that the bacteria accelerate the assimilation of elements from the vitrified bottom ash.
The LREE/HREE ratios of the corn plants (15 -50) are similar to those found in beech trees of a forested catchment (35-50) indicating that the small 30 days old corn plants reached already a degree of LREE enrichment comparable with that of trees which attained already full growth. The data from the catchment further indicate that the trees fully control the LREE depletion in the waters of the stream draining this catchment. Therefore, vegetation might be generally an important factor controlling LREE depletion in river water.