Accumulation of Copper, Zinc, Cadmium and Lead and Distribution within Organs of Cotton Cultivars, Grown in Metal -Contaminated Soil

43 Bulgarian Journal of Agricultural Science, 12 (2006), 43-49 National Centre for Agrarian Sciences Accumulation of Copper, Zinc, Cadmium and Lead and Distribution within Organs of Cotton Cultivars, Grown in Metal -Contaminated Soil V. DELIBALTOVA and B. YANKOV Agricultural University, Agricultural Faculty, Department of Crop Science, BG-4000 Plovdiv, Bulgaria Abstract DELIBALTOVA, V. and B.YANKOV, 2006. Accumulation of copper, zinc, cadmium and lead and distribution within organs of cotton cultivars, grown in metal -contaminated soil. Bulg. J.Agric.Sci., 12: 43-49 The purpose of the research was to establish the accumulation of five Bulgarian cotton cultivars to different concentrations of heavy metals in the soil, as well as the distribution of copper, zinc, cadmium and lead in the plants organs. In order to accomplish our purpose, we set pot experiments with the cultivars Beli izvor, Ogosta, Chirpan 603, Chirpan 539 and Avanguard. The trial was carried out in 6 variants with 3 replications. These concentrations of heavy metals were - 0, 1.5, 2.5, 3.5, 5 and 10 times above the maximum permissible concentrations. The results showed that, heavy metals concentrations in the soil, that were higher than 5 times above the maximum permissible concentrations, were lethal to some cotton cultivars. The main part of the absorbed quantities of heavy metals were fixed and accumulated in the root system of the cotton plants. In concentrations of Cu, Zn, Cd and Pb in the soil up to 3.5 times above the maximum permissible concentrations, the Bulgarian cotton cultivars did not exhibit tendency towards accumulation of high quantities of heavy metals in the fibre and the seeds. Key words: accumulation, cotton, cultivars, concentrations of heavy metals Introduction The heavy metal pollution of soils is a current environmental problem (Alntara et al., 2002). These metals are a potential risk for human health when transferred from plant products to the human diet. On entering from the soil into the plants, in higher doses the heavy metals cause changes in the running of the plants vegetative and generative processes, by reducing the agricultural plants productivity (Shilev et al., 2003b; Zheljazkov and Nielsen, 1996). The increase of the heavy metals contents above the maximum permissible concentrations in the agricultural produce strongly impedes and limits its

44 selling. Differences of species and cultivars were found on entrance and localization of the heavy metals in the plants organs (Angelova et al., 2004b; Andonov and Georgieva, 2001). Higher concentrations were ascertained in maize, leguminous and ethereal-oil crops (Angelova et al., 2004d). In general, the heavy metals distribution in the plants decreases in the following direction: roots > stems > leaves > fruits (Angelova et al., 2004c; Yankov and Tahsin, 2001; Shilev et al., 2003a). Watson et al. (1985) have found that the contents of Cd in the cotton leaves was higher compared to that in the seeds. According to Malewar and Dudde (1995), cotton was more resistant to increased contents of zinc in the soil than sorghum. Angelova et al. (2004a) ascertained high resistance of cotton to pollution. The purpose of the research was to establish the accumulation of 5 Bulgarian cotton cultivars to different concentrations of heavy metals in the soil, as well as the distribution of Cu, Zn, Cd and Pb in the plants organs. Material and Methods V. Delibaltova and B. Yankov In 1999 and 2000 pot experiments were conducted with the cotton cultivars Beli izvor, Ogosta, Chirpan 603, Chirpan 539 and Avanguard. The soil was taken from the arable layer of the experimental base of the Agricultural University in Plovdiv, Bulgaria. The experiment was held on a former meadow-swampy slightly saline soil, sandy-clayey. The soil reaction was neutral to alkaline (ph - 7.0-7.5) and the humus content was high (4-6%)The soil preparation included cleaning, sifting through a sieve with diameter of the openings 2 mm and treatment, by means of sprayer, with a working solution, containing nitrogen and the heavy metals - Cu, Zn, Cd and Pb in the form of Cu(N0 3, Zn(N0 3, Cd(N0 3, Pb(N0 3. In all variants of the trial, together with the solution we introduced once 100 mg N in the form of Ca(N0 3, then the soil was homogenized and prepared for analysis by means of treatment with aqua regia, ensuring practically the complete extraction of the heavy metals. The trial was carried out in 6 variants with 3 replications. Variant 1 - control Variant 2 Cu 405 mg/kg ; Zn 540 mg/kg ; Cd 3 mg/kg and Pb 120 metals were 1.5 times above the maximum Variant 3 Cu 675 mg/kg ; Zn 900 mg/kg ; Cd 5 mg/kg and Pb 200 metals were 2.5 times above the maximum Variant 4 Cu 945 mg/kg ; Zn 1260 mg/kg ; Cd 7 mg/kg and Pb 280 metals were 3.5 times above the maximum Variant 5 Cu 1350 mg/kg; Zn 1800 mg/kg; Cd 10 mg/kg and Pb 400 metals were 5 times above the maximum Variant 6 Cu 2700 mg/kg; Zn 3600 mg/kg; Cd 20 mg/kg and Pb 800 metals were 10 times above the maximum 9000 g of absolutely dry soil at volume density 1.15 were introduced in vessels * Maximum permissible concentrations Cu - 270 mg/kg, Zn - 360 mg/kg, Cd - 2 mg/kg, Pb - 80 mg/kg.

Accumulation of Copper, Zinc, Cadmium and Lead and Distribution Within Organs... 45 with volume 10 liters, that were preliminarily weighed with drainage (sieved fine gravel). The moisture content was registered daily and 70±75% of the maximum water-holding capacity was maintained through the experiment by weighing each pot followed by adjustment with tap water. In order to achieve dynamic equilibrium of the heavy metals with the soil s absorbing complex, the sowing was carried out thirty days after the preparation of the vessels (Vassilev et al., 1998). After germination we left one plant in each vessel. Weeding, loosening and irrigation were carried out during the vegetation. The irrigation complied with the plants needs during the separate phenophases. In all variants of the studied cotton cultivars the heavy metals contents (Cu, Zn, Cd and Pb) in the roots, stems, leaves, fibres and seeds was determined after the method of the dry mineralization, described by Angelova (1998). For the purpose of determining the quantity dependence between the studied indicators, the experimental data was processed according to the Anova Method of dispersion analysis, and the differences between the variants were determined by means of the Dunkan s Multiple Range Test (1995). Results and Discussion The obtained results for the contents of Cu, Zn, Cd and Pb in the organs of cotton plants, grown at different levels of heavy metals in the soil, showed that soil concentrations of heavy metals 5 and 10 times above the maximum permissible concentrations did not allow the cotton seeds to germinate and to form plants, i.e. these doses were lethal for the cotton plants (data not shown). The increase of the quantity of Cu, Zn, Cd and Pb in the soil up to 3.5 times above the maximum permissible concentrations lead to an increase of their contents in the cotton plants organs. Most considerable changes occurred in the roots. The main part of the absorbed quantities were fixed and accumulated in them (Table 1). The considerably higher contents of heavy metals in the roots, compared to the other plants organs, was explained with the fact that, on penetration in the plasma, inactivation and precipitation of considerable quantities of heavy metals has taken place in result of the formation of little mobile compounds with the organic substance. Cultivar differences were found. The cultivar Beli izvor accumulated the highest quantity of Cu and Zn, and the cultivar Avanguard Pb. The lowest were the concentrations of Cu and Zn in the roots of cultivar Chirpan 539. The contents of heavy metals in the stems of the cotton plants (Table 2) was considerably different compared to that in the roots. On increasing their quantity in the soil - 3.5 times above the maximum permissible concentrations, the contents of Cu, Zn, Cd and Pb was respectively 9, 2, 3 and 5 times lower in the stems, compared to the roots. The lowest quantity of Zn was accumulated in cultivar Chirpan 539, and the highest in cultivar Beli izvor. The leaves are a basic metabolic organ, in which all cells are active, while the stem is mainly a transportation organ. The higher quantity of heavy metals in the leaves of the plants from the control (V 1 ), compared to the stems, was due to the fact that the absorbed water and soluble nutritious substances were included in the synthesis of assimilative substances, necessary for formation of new biomass and for obtaining energy for maintaining the plants

46 V. Delibaltova and B. Yankov Table 1 Contents of Cu, Zn, Cd and Pb (mg/kg) in the roots of cotton cultivars Variants Cultivars Cu Zn Cd Pb V 1 (control) Beli izvor 0.5 a 2.1 b 0.05 b 0.7 c Cu - 20.4 mg/kg Ogosta 0.5 a 2.0 b 0.05 b 0.6 b Zn - 57.1 mg/kg Chirpan 603 0.6 a b 2.1 b 0.04 a 0.5 a Cd - 1.75 mg/kg Chirpan 539 0.7 b c 1.9 b 0.05 b 0.6 b Pb - 14.8 mg/kg Avanguard 0.8 c 1.4 a 0.04 a 0.6 b LSD 5 % 0.12 0.31 0.01 0.07 V 2 Beli izvor 25.2 c 41.6 b 0.26 b 2.10 a Cu - 405 mg/kg Ogosta 20.3 a 35.1 a 0.21 a 2.13 a b Zn - 540 mg/kg Chirpan 603 24.1 c 46.1 c 0.20 a 2.27 c Cd - 3 mg/kg Chirpan 539 19.5 a 35.8 a 0.18 a 2.23 b c Pb - 120 mg/kg Avanguard 22.6 b 35.8 a 0.19 a 2.30 c LSD 5 % 1.83 1.32 0.05 0.13 V 3 Beli izvor 45.4 c 116 d 0.88 d 21.7 a Cu - 675 mg/kg Ogosta 36.5 a 108 c 0.71 b 22.1 a Zn - 900 mg/kg Chirpan 603 43.4 c 119 d 0.68 b 23.5 b Cd - 5 mg/kg Chirpan 539 34.6 a 95 a 0.62 а 23.1 b Pb - 200 mg/kg Avanguard 40.7 b 100 b 0.75 c 23.8 b LSD 5 % 2.55 4.44 0.03 1.01 V 4 Beli izvor 186 d 215 e 2.20 b c 36.1 d Cu - 945 mg/kg Ogosta 160 b 209 d 1.60 a 25.1 a Zn - 1260 mg/kg Chirpan 603 173 c 180 b 1.90 a b 31.9 c Cd - 7 mg/kg Chirpan 539 146 a 169 a 1.60 a 28.3 b Pb - 280 mg/kg Avanguard 162 b 200 c 2.30 c 40.3 e LSD 5 % 4.09 4.41 0.35 2.46 vital processes. A part of the heavy metals were fixed in the leaves. On increasing the contents of the heavy metals in the soil (the variants V 2, V 3 and V 4 ), their variation in the leaves was different compared to than in the cotton roots and stems. The contents of Cu varied within small limits and in variant V 4 was about 2 2.5 times higher compared to the control. The variation of the quantity of Zn and Cd in the leaves was significantly higher compared to Cu. The values read in the variants V 2, V 3 and V 4 were higher in the leaves compared to the stems. In variant V 4 the quantity of Pb in the leaves was about 3-4 times higher compared to the control, and the read values were almost alike those in the stems.

Accumulation of Copper, Zinc, Cadmium and Lead and Distribution Within Organs... 47 Table 2 Contents of Cu, Zn, Cd and Pb ( mg /kg ) in the stems and leaves of cotton cultivars Variants Cultivars Cu Zn Cd Pb stems leaves stems leaves stems leaves stems leaves V 1 (control) Beli izvor 0.7 a 6.0 d 2.5 b c 15.9 e 0.02 a 0.20 b 0.6 a 1.95 b Cu - 20.4 mg/kg Ogosta 0.9 a 5.6 c 2.8 d 13.7 c 0.03 a 0.16 a b 0.6 a 1.45 a Zn - 57.1 mg/kg Chirpan 603 0.7 a 5.2 b 2.6 c d 15.1 d 0.03 a 0.16 a b 0.5 a 1.41 a Cd - 1.75 mg/kg Chirpan 539 0.8 a 4.6 a 2.3 a b 12.1 a 0.03 a 0.11 a 0.5 a 1.42 a Pb - 14.8 mg/kg Avanguard 0.9 a 5.9 c d 2.1 a 13.1 b 0.03 a 0.15 a b 0.6 a 1.39 a LSD 5 % 0.31 0.38 0.28 0.37 0.22 0.06 0.34 0.09 V 2 Beli izvor 8.20 c 7.0 b 30.3 c 47.1 a 0.14 c d 0.34 c d 1.40 c 2.06 a b Cu - 405 mg/kg Ogosta 6.85 a 6.4 a 27.1 b 60.4 c 0.11 a 0.31 b 1.20 b 2.30 c Zn - 540 mg/kg Chirpan 603 7.25 b 6.8 b 36.2 d 46.1 a 0.12 a b 0.27 a 1.50 d 1.95 a Cd - 3 mg/kg Chirpan 539 8.15 c 8.2 c 24.7 a 57.5 b 0.13 b c 0.31 b 0.95 a 2.15 b c Pb - 120 mg/kg Avanguard 9.11 d 8.5 d 26.6 b 66.6 d 0.15 d 0.36 d 1.45 c d 2.20 b c LSD 5 % 0.47 0.35 0.94 2.20 0.22 0.03 0.09 0.21 V 3 Beli izvor 13.5 c 8.2 b 51.1 c 108 b 0.26 b 0.65 c 2.4 c 3.6 b Cu - 675 mg/kg Ogosta 11.3 a 7.5 a 46.5 b 114 c 0.21 a 0.59 b 2.1 a b 3.7 b c Zn - 900 mg/kg Chirpan 603 12.0 b 7.9 b 58.3 d 107 a 0.21 a 0.52 a 2.5 c 3.4 a Cd - 5 mg/kg Chirpan 539 12.4 b 9.2 c 43.2 a 104 a b 0.24 b 0.57 b 1.9 a 3.7 b c Pb - 200 mg/kg Avanguard 13.1 c 9.9 d 44.3 a 125 d 0.25 b 0.64 c 2.3 b c 3.8 c LSD 5 % 0.66 0.37 1.67 4.57 0.03 0.06 0.28 0.22 V 4 Beli izvor 21.0 c 10.0 a 191 d. 262 d 0.87 b 1.28 b 6.50 b 6.2 b Cu - 945 mg/kg Ogosta 14.7 a 12.0 a b 171 c 257 c 0.60 a 0.99 a 5.40 a 5.7 a Zn - 1260 mg/kg Chirpan 603 21.7 c 13.4 b c 154 b 252 b 0.80 b 1.05 a 8.16 d 7.5 c Cd - 7 mg/kg Chirpan 539 15.7 a b 10.1 a 145 a. 219 a. 0.65 a 0.96 a 5.20 a 5.9 a b Pb - 280 mg/kg Avanguard 17.4 b 14.8 c 172 c 286 e. 0.68 a 1.30 b 7.30 c 8.2 d. LSD 5 % 2.20 2.52 4.25 5.17 0.13 0.09 0.44 0.41 Cultivar differences were observed. The highest quantities of Zn and Pb were accumulated in the leaves of cultivar Avanguard, and the lowest contents of Cu, Zn, Cd and Pb was found in cultivar Chirpan 539. Comparatively the lowest variations in the contents of the heavy metals (Cu, Zn, Cd and Pb) were observed in seeds and fibre (Table 3), which showed that at high concentrations the cotton plants did not exhibit tendency towards accumulation of high quantities of heavy metals in these organs. We did not observe significant cultivar differences in the heavy metals accumulation in the plants reproductive organs. Conclusion On the grounds of the carried out vessel trial with cotton cultivars, grown on soils, polluted with different concentrations of heavy metals, we made the following more important conclusions: Heavy metals concentrations in the soil, that were higher than 5 times above

48 V. Delibaltova and B. Yankov Table 3 Contents of Cu, Zn, Cd and Pb (mg /kg) in the seeds and figre of cotton cultivars Variants Cultivars Cu Zn Cd Pb seeds fibre seeds fibre seeds fibre seeds fibre V 1 (control) Beli izvor 7.0 a 1.8 a 32.4 a b 8.9 a 0.06 a b 0.05 a 0.35 a 1.25 a Cu - 20.4 mg/kg Ogosta 6.7 a 1.8 a 38.6 c 9.5 b 0.06 a b 0.10 b 0.45 b 1.20 a Zn - 57.1 mg/kg Chirpan 603 7.8 b 1.7 a 29.7 a 9.7 b c 0.05 a 0.09 b 0.45 b 1.35 b Cd - 1.75 mg/kg Chirpan 539 6.6 a 1.6 a 32.8 b 9.8 b c 0.05 a 0.09 b 0.55 c 1.57 c Pb - 14.8 mg/kg Avanguard 6.8 a 2.1 b 34.8 b 10.1 c 0.07 b 0.08 b 0.40 a b 1.52 c LSD 5 % 0.98 0.29 3.49 0.47 0.02 0.03 0.11 0.11 V 2 Beli izvor 7.4 b 2.5 b 55.0 b 16.1 a 0.14 a b 0.20 a b 0.6 a 2.0 b Cu - 405 mg/kg Ogosta 7.6 b c 2.9 c 51.4 a 18.6 b c 0.14 a b 0.20 a b 0.8 b 2.0 b Zn - 540 mg/kg Chirpan 603 6.8 a 1.9 a 58.8 c 19.7 c 0.13 a 0.22 b 0.6 a 1.8 a Cd - 3 mg/kg Chirpan 539 7.8 c 2.2 a b 57.6 c 17.2 a b 0.15 b c 0.18 a 0.8 b 1.9 a b Pb - 120 mg/kg Avanguard 7.5 b c 2.4 b 54.6 b 19.9 c 0.16 a 0.19 a 0.7 a b 1.8 a LSD 5 % 0.40 0.41 1.64 2.08 0.02 0.02 0.19 0.13 V 3 Beli izvor 8.9 b 2.7 b 64.7 b 22.2 a 0.24 b 0.31 b 0.76 a 2.1 a b Cu - 675 mg/kg Ogosta 8.8 b 3.1 c 62.5 a 25.9 b 0.24 b 0.32 b c 0.84 c 2.1 a b Zn - 900 mg/kg Chirpan 603 7.8 a 2.2 a 67.2 c 27.6 c 0.22 a 0.33 c 0.78 a b 2.0 a Cd - 5 mg/kg Chirpan 539 9.0 b 2.4 a b 65.8 b c 24.8 b 0.25 b 0.29 a 0.83 c 2.1 a b Pb - 200 mg/kg Avanguard 8.7 b 2.6 b 62.2 a 25.8 b 0.25 b 0.29 a 0.81 b c 2.2 b LSD 5 % 0.94 0.44 2.68 1.73 0.02 0.02 0.05 0.13 V 4 Beli izvor 10.9 c 3.10 b c 79.3 c 32.3 a 0.40 c 0.38 b c 0.89 a 2.2 a Cu - 945 mg/kg Ogosta 11.2 d 3.30 c 72.3 a 34.8 b 0.40 c 0.37 b c 0.90 a 2.3 a Zn - 1260 mg/kg Chirpan 603 11.3 d 2.67 a 75.1 b 39.5 d 0.35 b 0.39 c 0.90 a 2.4 a Cd - 7 mg/kg Chirpan 539 10.6 b 2.90 a b 74.6 b 37.0 c 0.30 a 0.36 a b 0.93 b 2.2 a Pb - 280 mg/kg Avanguard 10.2 a 2.80 a b 84.8 d 30.6 a 0.30 a 0.34 a 0.90 a 2.8 b LSD 5 % 0.22 0.37 2.02 2.17 0.04 0.03 0.02 0.48 the maximum permissible concentrations, were lethal to cotton. They did not allow the seeds to germinate and to form plants. The main part of the absorbed quantities of heavy metals were fixed and accumulated in the root system of the cotton plants. In concentrations of Cu, Zn, Cd and Pb in the soil up to 3.5 times above the maximum permissible concentrations, the Bulgarian cotton cultivars did not exhibit tendency towards accumulation of high quantities of heavy metals in the fibre and the seeds. Cultivar differences were observed in the accumulation of heavy metals in the separate plant organs. Cultivar Avanguard accumulated higher quantities of Zn and Pb in the leaves of the plants, compared to the other cultivars. Cultivar Beli izvor exhibited stronger tendency towards accumulation of Cu and Zn in the roots and stems.

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