Evaluation of vetiver grass for radiocesium absorption ability

Abstract

Plantlets of the Surat Thani and Ratchaburi ecotypes of vetiver grass (Chrysopogon zizanioides L. (Roberty). were hydroponically cultured in ¹³⁴Cs solutions to investigate their ¹³⁴Cs uptake ability. After 5 d of culture in ¹³⁴Cs solutions, the Surat Thani plantlets were still fresh and healthy without any evidence of toxicity symptoms, while the Ratchaburi plantlets were rather dry with some brown leaves. The information from the radiographic images and photo-stimulated luminescence (PSL) signals as well as the specific activity of cesium indicated that the Surat Thani plantlets cultured in ¹³⁴Cs solutions were significantly superior to the Ratchaburi vetiver plantlets with regard to ¹³⁴Cs absorption ability. The increase in the amount of ¹³⁴Cs in the vetiver plantlets with the level of ¹³⁴Cs in the culture solution was clearly demonstrated from the PSL signal, as the relationship between the PSL per square millimeter values and ¹³⁴Cs solution concentrations was linear. The data also indicated that both studied vetiver ecotypes accumulated more ¹³⁴Cs in the roots than in shoots; therefore, vetiver might be suitable for phytostabilization of radiocesium-polluted soil. The Surat Thani vetiver plantlets were cultured in ¹³⁴Cs solution with a concentration of 5 MBq/L for different periods. The results of the radiographic image, PSL signals and the radioactivity levels in the vetiver samples strongly indicated that vetiver could absorb a greater amount of ¹³⁴Cs when the period of culture was longer. After vetiver culture periods of 3 d, 6 d, 9 d, 12 d, 15 d and 18 d, the activity of ¹³⁴Cs in the cultured solutions declined to 98.0%, 93.2%, 88.6%, 78.1%, 70.7% and 65.5%, respectively. These values indicated that vetiver could remediate ¹³⁴Cs in the cultured solution by 2.0%, 6.8%, 11.4%, 21.9%, 29.3% and 34.5% for the respective durations.