ISSN 0012-4966, Doklady Biological Sciences, 2009, Vol. 425, pp. 180–182. © Pleiades Publishing, Ltd., 2009. Original Russian Text © E.V. Lazareva, S.A. Ostroumov, 2009, published in Doklady Akademii Nauk, 2009, Vol. 425, No. 6, pp. 843–845.
GENERAL BIOLOGY
Accelerated Decrease in Surfactant Concentration in the Water of a Microcosm in the Presence of Plants: Innovations for Phytotechnology E. V. Lazareva and S. A. Ostroumov Presented by Academician G.V. Dobrovol’sky September 26, 2008 Received October 1, 2008
DOI: 10.1134/S0012496609020276
Surfactants are an important group of membranotropic pollutants [1, 2]. Higher plants, including aquatic ones, form the basis for phytotechnologies used to purify and remediate natural environment polluted with various agents [3]. Aquatic plants (macrophytes) can serve as water-purifying factors; they constitute an important component of the natural system of water purification, which had been analyzed in [1, 2] and other studies. We previously determined the parameters of allowable long-term exposure to the surfactant sodium dodecylsulphate (SDS) of several aquatic plant species, including the macrophyte OST1, which is viewed as the basis for phytotechnology of purification of waters containing this alkyl sulphate. At the beginning, evidence had to be obtained that changes in water chemical composition and a decrease in the pollutant concentration actually occurred in the presence of the macrophyte. Measurement of the water surface tension makes it possible to trace the fate of a surfactant added into water. The working hypothesis was that the macrophyte promotes a decrease in the surfactant concentration in water, and the following events occur after the addition of surfactant into experimental microcosms. First, surfactant causes an immediate decrease in water surface tension. The subsequent decrease in the concentration of the added surfactant leads to a gradual restoration of the normal surface tension (the surface tension reduced by the surfactant is restored to the level typical of pure water). Thus, with decreasing concentration of the added surfactant, the surface tension should grow up gradually to the level characteristic of pure water. In this study, we verified the hypothesis that, in the presence of macrophytes, the initial sharp decrease in
Moscow State University, Moscow, 119991 Russia
water surface tension caused by addition of the surfactant sodium dodecylsulfate was followed by gradual restoration of surface tension. MATERIALS AND METHODS We used the macrophytes that proved suitable in previous experiments and displayed a high viability and resistance to surfactants (these plants will be described in detail elsewhere). Plastic flasks 1.5 l in volume each containing 1 l of settled tap water were used. In each of flasks 2, 3, 4, and 4A, 3 ml of a 2-g/l SDS solution was added. Thus, 6 mg of SDS solution was added to each flask. (SDS added at a lower concentration (0.4 mg/l) caused no noticeable changes because of the detection limit of the method). The temperature at the beginning of the experiment was 23°C. Live phytomass of the macrophyte OST1 (3 g of wet biomass) was added into the flasks 4 and 4A along with SDS. The flask 5 contained OST1 phytomass but no SDS was added. The flasks were kept at room temperature and were periodically illuminated with daylight lamps (8 h per day). After a certain time, water from the flasks was sampled to measure the surface tension by Wilhelmy’s method (the method of plate detachment [4]). This method is widely used to determine the surface tension of water containing various impurities [4]. Table 1 shows the results of these measurements after different periods of exposure (up to 646 h). RESULTS AND DISCUSSION Our measurements demonstrated that the surface tension of water in the microcosm with the OST1 macrophyte restored to the level close to that of pure water within less than three days. As soon as after 46-h incubation of the system containing plant phytomass, the surface tension increased significantly and reached that of distilled water, whereas in the control flasks (without plant phyto-
180
ACCELERATED DECREASE IN SURFACTANT CONCENTRATION
181
Table 1. The effect of macrophyte OST1 on changes in the surface tension of SDS solutions (mN/m) ExperiExposure time, h (temperature, °C, is indicated in parentheses) ment Experimental variant 0.3 (24) 0.8 (24) 1.3 (24) 22.3 (24) 46 (23) 70 (23) 142 (24) 238 (24) 406 (24) 646 (25) number 1 2 3 4 4A 5
Control (H2Odist) SDS SDS SDS + OST1 SDS + OST1 OST1 (– SDS)
72.18 68.59 68.59 68.59 69.24 72.18
72.18 69.24 69.24 69.89 69.89 72.18
72.18 68.92 68.92 69.57 69.24 72.18
72.18 68.92 68.92 69.57 69.24 72.18
72.28 68.70 68.70 71.30 71.63 72.28
72.28 69.02 69.35 71.16 72.28 72.28
72.18 68.70 69.24 71.92 71.92 72.18
72.18 69.89 70.22 72.18 72.18 72.18
72.18 72.19 72.19 72.49 72.49 72.18
71.97 71.85 71.84 72.29 72.29 72.29
Table 2. Plants (aquatic and terrestrial macrophytes) studied in experimental systems containing pollutants Plant species
Pollutant
Source
Individual surfactant preparations (surfactants) Fagopyrum esculentum Moench SDS, sulphanole; TX100, TDTMA [1, 6] Cucumis sativus L. SDS, TDTMA, ethonium [1, 6] Lepidium sativum L. TX100 [1, 6] Sinapis alba L. SDS, sulphanole [1, 6] Zea mays L. SDS [1, 6] Elodea canadensis Mchk., SDS [3]; a.m. Potamogeton crispus L., SDS [3]; a.m. Najas guadelupensis L. SDS [3]; a.m. Fontinalis antipyretica L., SDS [3]; a.m. Salvinia natans L., SDS [3]; a.m. Salvinia auriculata Aubl. SDS [3]; a.m. Individual preparations (pesticides and others) Lontrel [1, 6] Fagopyrum esculentum Moench Sinapis alba L. DNOC [1, 6] Cucumis sativus L. Lontrel [1, 6] Myriophyllum aquaticum (Vell.) Verdc. Perchlorate a. m.; new data (obtained in collaboration with S. McCutcheon, V.A. Nzengung, and D.D. Yifru) Mixed preparations Oryza sativa L. PLD, FLD [1, 6] Fagopyrum esculentum Moench PLD, FLD [1, 6] Cucumis sativus L. FLD [1, 6] Pistia stratiotes L. FLD [1, 6]; a.m. Fontinalis antipyretica L. PLD a.m.; new data (obtained in collaboration with E.A. Solomonova) Note: TX100, Triton X100; TDTMA, tetradecyltrimethylammonium bromide; PLD, powder laundry detergent; FLD, foam-producing liquid detergent; a.m., aquatic macrophytes; DNOC, dinitroothocresol (2, 4-dinitro-6-methylphenol).
mass), the surface tension (68.7 mN/m) remained similar to that recorded immediately after surfactant addition (68.59 mN/m). In flasks without plant phytomass, restoration of the surface tension was much longer (about 17 days) (Table 1). DOKLADY BIOLOGICAL SCIENCES
Vol. 425
2009
Our results demonstrated an accelerated restoration of the normal surface tension characteristic of pure water in systems containing SDS in the presence of the phytomass of the OST1 macrophyte. This is consistent with the assumption that the macrophyte accelerates surfactant disappearance from water.
182
LAZAREVA, OSTROUMOV
This is additional evidence for the importance of plants for water self-purification, which agrees with the previous concept of a multifunctional role of the biota in water self-purification [5–9]. Completely understanding the role of organisms in purification and functioning of aquatic ecosystems is important for comprehensive analysis of the biosphere [10, 11], including the notions on the biosphere apparatus [12] and the role of organisms in environmental stabilization. Studying these issues remains in the list of priority tasks of ecology [13] and contribute to developing new technologies for water purification, sustainable use of aquatic and aquatic–biological resources, ecologization of economy, and the major spheres of the functioning of society [14, 15], which are prerequisites for sustainable development. Thus, we have demonstrated that, in the presence of aquatic macrophytes, a decrease in the concentration of a synthetic surfactant in the water is accelerated. This suggests that the use of aquatic macrophytes is promising for the development of the phytotechnology of water purification. For several years, we have been performing experiments providing information on the parameters of plant resistance to pollutants and the factors important for the development of innovational ecotechnologies. Our first studies were performed on terrestrial plants, and then we continued with aquatic macrophytes (Table 2). This line of investigations promotes the development of phytoremediation methods and phytotechnologies required for water purification from synthetic surfactants, which are dangerous environmental pollutants contained in various waste waters [1, 6]. The above experiments contribute to understanding the influence of plants on pollutants, such as synthetic surfactants, occurring in water. We earlier suggested, in 2001, that the “relatively high resistance of plants to synthetic surfactants may be helpful in phytoremediation” ([1], p. 157). The results of this study support this conclusion.
ACKNOWLEDGMENTS E.A. Solomonova participated in this study as a postgraduate. We are grateful to our colleagues from Moscow State University for the assistance in the experiments. REFERENCES 1. Ostroumov, S.A., Biologicheskie effecty pri vozdeistvii poverkhnostno-aktivnykh veshchestv na organizmy (Biological Effects of Surfactants), Moscow: MAKS, 2001. 2. Ostroumov, S.A., Dokl. Biol. Sci., 2004, vol. 396, no. 1, pp. 206–211 [Dokl. Akad. Nauk, 2004, vol. 396, no. 1, pp. 136–141. 3. Solomonova, E.A. and Ostroumov, S.A., Vodn. Khozyaistvo Rossii, 2006, no. 6, pp. 32–39. 4. Shchukin, E.D., Kolloidnaya khimiya (Dispersiology), Moscow: Vysshaya Shkola, 2006. 5. Ostroumov, S.A., Riv. Biol., 1998, vol. 91, no. 2, pp. 221–232. 6. Ostroumov, S.A., Biological Effects of Surfactants, Boca Raton: CRC, 2006. 7. Ostroumov, S.A., Hydrobiologia, 2002, vol. 469, nos. 1–3, pp. 117–129. 8. Ostroumov, S.A., Hydrobiologia, 2002, vol. 469, nos. 1–3, pp. 203–204. 9. Ostroumov, S.A., Riv. Biol., 2004, vol. 97, pp. 39–50. 10. Dobrovol’skii, G.V., Ekol. Khimiya, 2007, vol. 16, no. 3, pp. 135–143. 11. Dobrovol’skii, G.V., Voda: Tekhnologiya i Ekologiya, 2007, no. 1, pp. 63–68. 12. Kapitsa, A.P., Environ. Ecology Safety Life Activ., 2007, no. 1 (37), pp. 68–71. 13. Ostroumov, S.A., Dodson, S., Hamilton, D., et al., Riv. Biol., 2003, vol. 96, pp. 327–332. 14. Yablokov, A.V. and Ostroumov, S.A., Conservation of Living Nature and Resources: Problems, Trends, Prospects, Berlin: Springer, 1991. 15. Yablokov, A.V. and Ostroumov, S.A., Urovni okhrany zhivoi prirody (Levels of Living Nature Protection), Moscow: Nauka, 1985.
DOKLADY BIOLOGICAL SCIENCES
Vol. 425
2009
