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Environmental problems. Grażyna Bystrzejewska-Piotrowska and Mariusz Jeruzalski, Renata Nowacka, Agata Drożdż Warsaw Uniwersity, Isotopic Laboratory, Poland. ENVIRONMENTAL PROBLEMS. I The problems of bioremediation by plants and fungi of contaminated soils by radionuclides.
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Environmental problems Grażyna Bystrzejewska-Piotrowska and Mariusz Jeruzalski, Renata Nowacka, Agata Drożdż Warsaw Uniwersity, Isotopic Laboratory, Poland
ENVIRONMENTAL PROBLEMS • I The problems of bioremediation by plants and fungi of contaminated soils by radionuclides. • II How can we measure and evaluate the bioaccumulation of radionuclides by plants and fungi? • Do you belive that Transfer Factor (TF) and /or Discrimination Factor (DF) are distinguishable indicators for estimation of soil composition and / or for bioaccumulation of radionuclides by living organisms ? • What indicator is distinguishable for estimation of radionuclides translocation from roots to stem in plants or from stipe to cap in mushrooms ?
Ad I. We all know that environment is contaminated by pollutants, among others by radiunuclides: 137Cs, 90Sr, or radioisotopes of uranium. One of the methods of contaminated soil remediation is biological remediation with using plants or fungi. There are the following terms of the radionuclides bioaccumulation: • solubility of radionuclides, • bioavailability of radionuclides in soils, • pH as an important agent of bioavailability, for example 4-5 for cesium uptake (Urban and Bystrzejewska, 2003), • the influence of plant roots on the soils via the change of soils pH, and via phytochelatation, • the cooperation of plant roots with microorganisms and with fungi in the uptake of radionuclides by plants.
Which of the plants are the phytoaccumulators ? • The plants which prefer the accumulation of polutant in above-ground part of plant, not in roots. • The plants in which the concentration of radionuclides in above-ground part of plant is 1000-fold greater as their concentration in the soil. • Generally the big plants in which the total amount of radionuclides is very high. • The plants with fast growth, high transport of radionuclides to the shoot, and increased radionuclides tolerance.
The concept of using hyperaccumulator plants to take up and remove heavy metals from contaminated soils was first discovered by Chaney (1983). Hyperaccumulators take up large quantity of toxic metals through their roots and transport them to stems or leaves. For example, it was shown that Allium cepa takes up cesium from the fallout and from the soil and is a 137Cs-reservoir, from which it is being released to the unpolluted soil (Bystrzejewska and Urban, 2004). Additionally, this plant accumulated the part of cesium in the dry senile leaves. The high accumulation of cesium we also observed in leaves of small plants of cress (Lepidium sativum) after both root and foliar treatments (Bystrzejewska and Urban, 2003).
Ad. II. Such agent as Transfer Factor is a very good indicator giving information about the composition of the soil. The same species of plants and fungi, but living in other environmental conditions, have the different TF. However, TF does not identify the ability of plants and fungi for bioaccumulation of radionuclides. Although it is often used by scientists who are not biologists.
The good indicator for valuation of the ability of the plants and mushrooms for uptake of radionuclides from the soil is for example the 137Cs/40K Discrimination Factor. The DF is not the same for all radionuclides. The 137Cs/40K DF was defined as follows: A(137Cs)plant ------------------- A(40K)plant DF = ---------------------- A(137Cs)soil ------------------- A(40K)soil This is a formula presented by Zhu and Smolders (2000), which referred to plant to substrate DF. The letter A symbolizes (respectively) cesium and potassium activities in the samples.
It is also a good agent for identifying the constant for translocation from lower to upper parts of fungi and plants. The 137Cs/40K DF, characterising each species, was defined as follows: A(137Cs)cap ---------------- A(40K) cap DF= ----------------------- A(137Cs)stipe ----------------- A(40K)stipe
If unfortunately, a dirty bomb with 137Cs explodes we will not use the plants with the highest Transfer Factor but first of all the plants with the optimal 137Cs to 40K Discrimination Factor.
Now I would like to present the following illustrations. For example, we have been investigating the accumulation of 137Cs in croton plants depending on the concentration CsCl in medium (soil). Figure 1. 137Cs accumulation in croton plants and its distribution among shoot and roots CsCl concentration the whole plant shoot roots (mM) (kBq) ( % of total) 0.03 2.12 44.8 55.2 0.3 22.09 17.2 82.75 3 0.72 65.5 34.7 5 0.27 66.7 33.3 Mariusz Jeruzalski 2004
Conclusions: • Croton is the plant to accumulate the most of 137Cs with relatively high concentration – 0.3 mM CsCl and then with 0.03 mM and minimal with 3 and 5 mM. • With the concentration of 0.3 mM CsCl the roots as the parts of the plant accumulated the most that is 80 % of the whole 137Cs taken by the plant.
Figure 2. Mariusz Jeruzalski 2004
Conclusions: • Transfer Factor was the highest with the concentrations of 0.3 mM Cs Cl and it amounted to over 9, lower with the concentration of 0.03 amounting to 1. TF was unfavourable for the phytoremediation with the higher concentration of CsCl. • Only by 0.3 mM CsCl concentration was this factor for 137Cs transfer from soil to shoot over 3 and only this concentration is appropiate for using croton plants for bioremediation.
Figure 3. Mariusz Jeruzalski 2004 With the concentration of 0.3 mM CsCl TF shows special ability of youngleaves for bioaccumulation of radionuclides.
In the following research we have been investigating the influence of 0.3 mM CsCl traced additionally by radiocesium on the growth and cesium accumulation by three species of C-4 plants: corn (Zea mays), Polish and Australian millet (Panicum).
Figure 4. The relation fresh weight / dry weight in corn and the Polish and Australish millet This concentration of CsCl had no impact on fresh and dry weight of the whole plant and the tissues compared with control plants. Renata Nowacka 2004
The investigated plants accumulated 137Cs in variable degree (Fig. 5.) Figure 5. Renata Nowacka 2004
The corn and Polish millet have accumulated in the shoot similar quantity of 137Cs (Fig.6). Figure 6. Renata Nowacka 2004 Very high accumulation of 137Cs has been recognized in corn roots; relatively small – in Polish millet and total absence in Australian millet.
Figure 7. Renata Nowacka 2004 The 137Cs accumulation ratio between the shoot and the roots was 0.32 for the corn, 3,07 for the Polish millet, and 100 for Australian millet (Fig.7).
Conclusions: Among the investigated plants the corn turned out to be the best bioaccummulator of cesium but millet plants were not efficient. However, for the purposes of bioremediation of cesium, the plants which accumulate Cs mainly in the shoot, are the best. From this point of view among the tested plants Australian millet accumulating Cs exclusively in the shoot, turned out to be the most effective. The next plant is Polish millet accummulating Cs in its shoot 3 times more than in its roots. Consequently, the corn is the least useful for phytoremediation purposes.
Figure 8. Renata Nowacka 2004 Similar information was obtained by Transer Factor of cesium from soil to the shoot and from soil to roots (Fig. 8.).
Figure 9. 137Cs Transfer Factor for heather plants (Calluna vulgaris) CsCl concentration 137Cs in roots/137Cs in soil (mM) 0.030.78 0.30.80 Agata Drożdż 2004 The researches conducted on heather plants (Calluna vulgaris) show relatively high TF from soil to roots(Fig.9.) with the following Cs concentration : 0.3 and 0.03 mM CsCl which was about 0.8.
The distribution of 137Cs in parts of plant strongly depended on CsCl concentration (Fig.10). Figure 10. The distribution of137Cs in parts of heather plants. CsCl concentration 137Cs in shoot 137Cs in roots (mM)( % ) 0.03 12.7 87.3 0.3 76.05 23.95 Agata Drożdż 2004 With the concentration of 0.3 the activity of 137Cs was higher in the shoot and with the concentration of 0.03 was relatively higher in the roots.
Figure 11. The 137Cs/40K discrimination factor (DF) in heather plants. CsCl concentration 137Cs/40K in roots DF = --------------------------- 137Cs/40K in soil 0.030.59 0.31.26 Agata Drożdż 2004 Also the coefficient - DF 137Cs to 40K in roots and 137Cs to 40K in soil was differentiated with the two concentrations and amounted with 0.3 CsCl to 1.26 and with 0.03 to 0.59.
All these examples confirm complexity and difficulty of plant assessment for bioaccumulation and consequently, phytoremediation.
REFERENCES Bystrzejewska-Piotrowska G, Urban PL (2003) Accumulation of cesium in leaves of Lepidium sativum and its influence on photosynthesis and transpiration. Acta Biol Cracov (Bot) 45/2:131-137. Bystrzejewska-Piotrowska G, Urban PL, Stęborowski R (2003) Discrimination between 137Cs and 40K in the fruiting body of wild edible mushrooms. Nukleonika 48/3:155-157. Bystrzejewska-Piotrowska G and Urban PL (2004) Accumulation and translocation of cesium-137 in onion plants (Allium cepa).Environ Exp Bot 51:3-7. Chaney RL (1983) Plant uptake of inorganic waste constituents. In Land treatment of hazardous wastes pp 50-76 eds JF Parr, PB Marsh and JS Kla, Noyes Data Corp., Park Ridge, NJ. Urban PL and Bystrzejewska-Piotrowska G (2003) Comparative analysis of cesium and potassium uptake in onion Allium cepa L. Czech. J. Phys. 53: A91-A96. Zhu YG, Smolders E (2000) Plant uptake of radiocesium: a review of mechanisms, regulation and application. J. Exp Bot 51:1635-1645.
