Uptake kinetics of 99Tc in common duckweed.
نویسندگان
چکیده
The uptake of the nuclear waste product technetium-99 was studied in common duckweed (Lemna minor). In addition to measurements, a model involving two compartments in duckweed with different chemical forms of technetium was derived. The model was tested by chemical speciation, i.e. differentiating between reduced Tc-compounds and Tc(VII)O(4)(-). The TcO(4)(-) concentrations measured were in good agreement with those predicted by the model. Two processes determine technetium uptake: (1) transport of Tc(VII)O(4)(-) across the cell membrane, and (2) reduction of Tc(VII). The TcO(4)(-) concentration in duckweed reaches a steady state within 2 h while reduced Tc-compounds are stored, as a result of absence of release or re-oxidation processes. Bioaccumulation kinetic properties were derived by varying 99Tc concentration, temperature, nutrient concentrations, and light intensity. The reduction of technetium in duckweed was highly correlated with light intensity and temperature. At 25 degrees C the maximum reduction rate was observed at light intensities above 200 µmol m(-2) s(-1) while half of the maximum transformation rate was reached at 41 µmol m(-2) s(-1). Transport of TcO(4)(-) over the cell membrane requires about 9.4 kJ mol(-1), indicating an active transport mechanism. However, this mechanism behaved as first-order kinetics instead of Michaelis-Menten kinetics between 1x10(-14) and 2.5x10(-5) mol l(-1) TcO(4)(-). Tc uptake could not be inhibited by 10(-3) mol l(-1) nitrate, phosphate, sulphate or chloride.
منابع مشابه
Influence of salinity and eutrophication on bioaccumulation of 99technetium in duckweed.
This study concerns the bioaccumulation of the long-lived nuclear waste product 99Tc in duckweed (Lemna minor L.). 99Tc was present as the oxyanion TcO4-, being the main chemical form of technetium in aerobic water systems. In contrast with terrestrial plants, bioaccumulation in duckweed proved to be independent of the nitrate concentration in the medium. However, uptake is controlled by electr...
متن کاملSoil availability, plant uptake and soil to plant transfer of 99Tc--a review.
The fission yield of 99Tc from 239Pu and 235U is similar to that of 137Cs or 90Sr and it is therefore an important component of nuclear weapons fall-out, nuclear waste and releases from nuclear facilities. There is particular current interest in 99Tc transfer from soil to plants for: (a) environmental impact assessments for terrestrial nuclear waste repositories, and (b) assessments of the pote...
متن کاملUptake and transformation of phenols by duckweed (Lemna gibba)
Phenol and its derivatives are common constituents of numerous natural and synthetic chemicals including pesticides. As a consequence of anthropological activities, a portion of them may reach various water bodies as contaminants which will have a great impact on the aquatic environment including biota. Aquatic plants are known to be one of the major habitants and food for many species and henc...
متن کاملSorption/desorption of radioactive contaminants by sediment from the Kara Sea.
To understand the long term impact of the disposal of radioactive waste on the Kara Sea, partition coefficients (Kd) for several important radionuclides, the mineralogy of the sediment, and the relationship of Kd to liquid-to-solid ratio were quantified. Sediment was obtained from four locations in the Kara Sea area. Slow sorption kinetics were observed for 85Sr, 232U, 125I and 99Tc, whilst sor...
متن کاملControl of euglenophyte bloom and fish production enhancement using duckweed and lime
Euglenophyte bloom is a common problem in most of the aquaculture ponds in Bangladesh. In the present study we conducted an experiment to control euglenophyte bloom for achieving better fish production using duckweed (Lemna minor) and lime. The experiment was carried out using four treatments, i.e., ponds were supplied with duckweed (T1), lime treatment (T2), both duckweed and lime (...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Environmental and experimental botany
دوره 44 1 شماره
صفحات -
تاریخ انتشار 2000