Effect of cd and as in soil on growth availability to plant

Effect of cd and as in soil on growth availability to plant

Symposium no. 60 Paper no. 1873 Presentation: poster 1873-1 Effect of cadmium and arsenic in soils on growth and availability to vegetables KIM Won-Il (1), JUNG Goo-Bok (1), LEE Jong-Sik (1), KIM Jin-Ho (1), YUN Sun-Gang (1) and PARK Ro-Dong (2) (1) National Institute of Agricultural Science and Technology (NIAST), Suwon, 441- 707, KOREA (2) Chonnam National University, Kwangju, 500-757, KOREA Abstract To find the adverse effect of cadmium (Cd) and arsenic (As) on the growth of major vegetables in Korea, phytotoxicity and absorption of Cd and As were investigated with chinese cabbage, radish, and lettuce grown at the different concentration of upland soils. Cd phytotoxicity was shown by growth retardation and leaf chlorosis of chinese cabbage and lettuce at the early growing season whereas As phytotoxicity was shown by growth retardation of radish and lettuce. The threshold Cd concentrations of growth damage resulting from the significant reduction (5%) of growth and yield of chinese cabbage and lettuce were 50-100 mg kg -1 and 10-25 mg kg -1 , respectively. The growth of radish and lettuce were significantly reduced at the 10-15 mg kg -1 and 10-25 mg kg -1 of As treated soils, respectively. However, there was no significant reduction of radish yield under 100 mg kg -1 of Cd treated soils and chinese cabbage yield under 30 mg kg -1 of As treated soils. As the concentrations of Cd and As in soils were increased, the contents of Cd and As in agricultural products were significantly increased, basically. The contents of Cd in edible part of Chinese cabbage, radish and lettuce grown at the 5 mg kg -1 Cd treated soils were 0.13, 0.18 and 3.37 mg kg -1 FW, respectively. Total absorbed Cd for each vegetable tends to occur in the following order, chinese cabbage > radish > lettuce at the high Cd treated soils whereas lettuce absorbed more Cd than chinese cabbage and radish at the low concentration of Cd. In case of As, the contents of As in edible part of chinese cabbage, radish and lettuce grown at the 6 mg kg -1 Cd treated soils were 0.19, 0.03 and 0.04 mg kg -1 FW, respectively. Total absorbed As for each vegetable tends to occur in the order of chinese cabbage > radish > lettuce. The acceptable Cd and As amount in vegetables were calculated with 0.06 and 0.12 mg kg -1 FW based on the WHO’s provisional tolerable intake of 7 µg Cd/d and 150 µg As/d, respectively. Therefore, we can estimate the acceptable Cd and As content in the upland soil for each vegetable and more detailed study is needed considering any other factors. Keywords: cadmium, arsenic, vegetables, phytotoxicity, upland soils Introduction Due to heavy industrialization and urbanization for the last few decades, heavy metal concentrations in the cultivating soils have gradually increased. The increase of contaminants in agricultural ecosystem has become a social issue worldwide as it is related with public health. Generally, heavy metals accumulate slowly but continuously in agricultural fields and may damage crops and livestock even humans through food KIM ET AL. 17 th WCSS, 14-21 August 2002, Thailand 1873-2 chain. International agencies, such as the Food and Agriculture Organization (FAO) and the World Health Organization (WHO), are currently advocating compliance to permission criteria of pollutants in agricultural products (Kabata-Pendias and Pendias. 1984; Fergusson. 1990; FAO. 1989). Arsenic (As) is not essential for plant growth. Because of chemical similarities to P, As is able to replace P in many cell reaction and shows many harmful toxicity to plants including wilting of new-cycle leaves and retardation of root and top growth (Aller et al., 1990). Lee et al. (1986, 1987) extensively reviewed that the behavior of As in paddy fields and the effects of absorbed As on physiological and ecological aspects of rice plant. Cadmium (Cd) is not essential for plant growth, too. Cd is chemically similar to Zn, an essential element. Cd is readily taken up by the roots and translocated through the plant and accumulated when it presents in available form. Cd is very toxic to plant at low concentration with reduced photosynthetic rate and plant growth. Symptoms include chlorosis, necrosis and wilting. Kim et al., (1983) establelished the threshold level of Cd for damage of rice plant growth. Muramoto et al., (1990) also reported that root and shoot weights of rice were reduced 32% and 21% by 100 mg kg -1 Cd. However, the studies on the effect of vegetable growth by As and Cd were limited (John, 1972; Sadana and Singh, 1987). Therefore, this study was carried out to find the adverse effect of As and Cd on the growth of chinese cabbage, radish and lettuce and to establelish the critical level of elements in chinese cabbage, radish and lettuce. Materials and Methods A silty loam soil with low concentrations of As and Cd was used in the experiment. Physico-chemical properties of the soil were measured by the standard methods of soil chemical analysis (NIAST, 1988) and were shown in Table 1. Soil was treated with Na 2 HAsO 4 , to 3, 6, 10, 15, 30 mg kg -1 of As soil and CdCl 2 ·2½H 2 O, to 5, 10, 25, 50, 100 mg kg -1 of Cd soil. As and Cd were measured by inductively coupled plasma emission spectroscopy (ICP, GBC Integra XMP). Chinese cabbage (Brassica ampestris L.), radish (Raphanus sativus L.), and lettuce (Lactuca sativa L.) were selected. Chinese cabbage and radish were seeded at the early May while lettuce in the middle of May. All of crops were harvested at the early July, dried, and ground. Fertilizers were applied to the standard methods of Rural Development Administration in Korea (1989). Total contents of As and Cd in vegetables were assayed by ICP after wet-acid (HNO 3 : H 2 SO 4 : HClO 4 = 10: 1: 4) digestion (NIAST, 1988). Experimental data were analyzed using super ANOVA (Abacus Concepts Inc. CA, 1989) for probability level of F-test. Table 1 Physico-chermical properties of soil used. Extractable cation (cmol (+) kg -1 ) pH OM (g kg -1 ) Avail P 2 O 5 (mg kg -1 ) KCaMg Clay (%) As* (mg kg -1 ) Cd** (mg kg -1 ) 5.3 24.0 92 0.2 4.3 0.9 12 0.21 0.10 * 1N-HCl soluble Arsenic ** 0.1N-HCl soluble cadmium KIM ET AL. 17 th WCSS, 14-21 August 2002, Thailand 1873-3 Results and Discussion Damage symptom of vegetables by As and Cd As phytotoxicity was shown by growth retardation of radish and lettuce whereas Cd phytotoxicity was shown by growth retardation and leaf chlorosis of Chinese cabbage and lettuce at the early growing season (Table 2). Relative yields (%) of the edible part of chinese cabbage, radish, and lettuce grown at the 0, 3, 6, 10, 15, and 30 mg kg -1 As treated soils were shown in Figure 1. The growth of radish and lettuce were significantly reduced at the 10-15 mg kg -1 and 10-25 mg kg -1 of As treated soils, respectively. However, there was no significant reduction of chinese cabbage yield under 30 mg kg -1 of As treated soils. As at 30 mg kg -1 soils was associated with 20% of reduction in both radish and lettuce yield. However, chinese cabbage did not affect in fresh weight at the 30 mg kg -1 As treated soils. It concluded that As concentration appearing toxicity was widely varied with plant species. Lee et al., (1986, 1987) widely identified the symptom of As toxicity in rice plants. They reported that rice yields significantly decreased with increasing soil As levels and the critical As levels in soils were estimated to be 6.79 mg kg -1 for loam and 2.75 mg kg -1 for sandy loam. Aller et al. (1990) investigated the rice appear to be more sensitive than other plants in experiments with toxic levels of As. Peterson et al. (1981) also reported that phytotoxicity of As is strongly affected by the form in which it occurs in soil. Arsenite is more toxic than arsenate. Therefore, it seemed that more As sensitive rice related with the reduced paddy soil condition. Table 2 Phytotoxicity of chinese cabbage, radish, and lettuce on the As and Cd treated soils. Contaminants As Cd Observed symptom Radish, Lettuce : growth retardation Chinese cabbage : chlorosis in seedling leaves Soil 10 mg kg -1 4 mg kg -1 Phytotoxicity Conc.* Solution 0.001 mg L -1 0.1 mg L -1 Phytotoxicity symptom* Wilting of new-cycle leaves, Retardation of root and top growth Chlorosis, necrosis, wilting, Reduction in growth *: Screening benchmark concentration for the phytotoxicity of heavy metals collected by the East Tennessee Technology Park Technical Information Office (Efroymsom, 1997) In Cd, chlorosis on the edge of chinese cabbage leaves was shown at the 100 mg kg -1 Cd concentration in soil during early growing season (Figure 2). As chinese cabbage was grown, chlorosis disappeared. However, chinese cabbage fresh weight reductions rose from less than 50% at the same plot (Figures 3and 4). In lettuce, 80% reduction in the yield after 8 weeks of growth from seed in soil to which 25 mg kg -1 Cd treated soil was shown. The threshold Cd concentrations of growth damage resulting from the significant reduction (5%) of growth and yield of chinese cabbage and lettuce were 50-100 mg kg -1 and 10-25 mg kg -1 , respectively. However, Cd at 100 mg kg -1 soil did not affect the radish growth. John et al. (1972) reported the effect of Cd on radish growth with 30 different surface soils. Root weight and shoot weight was reduced by an average of 67% and 47% by the addition of 100 mg kg -1 Cd, respectively. Sadana and Singh (1987) investigated the effects of Cd added to a loamy sand soil on lettuce. KIM ET AL. 17 th WCSS, 14-21 August 2002, Thailand 1873-4 Lettuce growth reduced 23% by the addition of 4 mg kg -1 Cd. It concluded that radish was more resistant to Cd than lettuce. 拒 Figure 1 Relative yield of the edible part of Chinese cabbage, radish, and lettuce grown at the different As treated soils. Figure 2 Growth damage of Chinese cabbage at the 100 mg kg -1 Cd concentration in soil during early growing season. KIM ET AL. 17 th WCSS, 14-21 August 2002, Thailand 1873-5 Figure 3 Growth retardation of lettuce at various concentrations of Cd in soil. Figure 4 Relative yield of the edible part of chinese cabbage, radish, and lettuce grown at the Cd treated soils. Contents of As and Cd in edible part of chinese cabbage, radish, and lettuce The contents of As and Cd in agricultural products were significantly increased as the concentrations of As and Cd in soils were increased, basically. Table 3 shows that the contents of As in edible part of chinese cabbage, radish and lettuce grown at the 0, 3, 6, 10, 15, and 30 mg kg -1 of As treated soils. The contents of As in the edible parts of chinese cabbage, radish and lettuce were significantly (5%) increased at the 6, 10, and 0 20 40 60 80 100 120 control 5 10 25 50 100 Cd conc.(m g /k g soil) Relative yield(% ) C. Cabbage Radish Lettuc e KIM ET AL. 17 th WCSS, 14-21 August 2002, Thailand 1873-6 30 mg kg -1 As treated soils, respectively. Total absorbed As for each vegetable tends to occur in the order of chinese cabbage > radish > lettuce (Table 4). Lee et al. (1986) reported that As contents in brown rice were 0.41 and 0.52 mg kg -1 FW at the 10 mg kg -1 As treated loam and sandy loam soils, respectively. The contents of As in edible part of chinese cabbage, radish and lettuce were 0.19, 0.03, and 0.05 mg kg -1 FW at the 10 mg kg -1 As treated soils, respectively. Kabata-Pendias and Pendias (1984) reported that there was a linear relationship between As content of vegetation and soluble As concentration in soils and plants take up As passively with the water flow. Therefore, it seems that rice plants accumulate more As than other vegetables due to higher water demand. Table 3 Concentrations of As in chinese cabbage, radish, and lettuce grown at the different As concentrations in soil. As conc. (mg kg -1 F.W.) Chinese cabbage Radish Lettuce As conc. (mg kg -1 ) Leaves roots leaves Control 0.12a* 0.012a 0.00a 3 0.15a 0.020ab - 6 0.19b 0.029ab 0.04a 10 0.19b 0.032b 0.05a 15 0.23c 0.057c 0.08a 30 0.22c 0.071d 0.25b *: within columns, means followed by the same letter are not significantly different at the 0.05 probability level using the F-test Table 4 Total As uptake in each plant of chinese cabbage, radish, and lettuce grown in soils of different As concentrations. Absorbed As conc. (µg plant -1 ) As conc. (mg kg -1 ) Chinese cabbage Radish Lettuce Control 302 5.1 0 3 322 8.6 - 6 462 10.6 1.5 10 482 14.3 1.9 15 550 20.5 2.9 30 530 20.7 7.1 Table 5 shows that the contents of Cd in edible part of chinese cabbage, radish and lettuce grown at the 0, 5, 10, 25, 50, and 100 mg kg -1 of Cd treated soils. The contents of Cd in edible part of chinese cabbage, radish and lettuce were significantly (5%) increased at the 5, 25, and 25 mg kg -1 Cd treated soils, respectively. Total absorbed Cd for each vegetable tends to occur in the following order, chinese cabbage > radish > lettuce at the high Cd treated soils whereas lettuce absorbed more Cd than chinese cabbage and radish at the low concentration of Cd (Table 6). Kim and Kim (1980) reported that Cd content in brown rice was 0.35 mg kg -1 FW at the 5 mg kg -1 Cd treated soil. The contents of Cd in edible part of chinese cabbage, radish and lettuce were 0.13, KIM ET AL. 17 th WCSS, 14-21 August 2002, Thailand 1873-7 0.04, and 3,37 mg kg -1 FW at the 5 mg kg -1 Cd treated soils, respectively (Table 5). With these results, rice plants accumulate more Cd than chinese cabbage and radish while less Cd than lettuce. Because of the difficulty in obtaining comparable data from different studies, it is best to give qualitative estimates for the uptake of the heavy metals by plants. Fergusson (1990) reported that relative uptake of As was high for chinese cabbage and medium for radish whereas relative uptake of Cd was medium-low for chinese cabbage, low-medium for radish and high for lettuce. These results were agreed with above orders, chinese cabbage > radish > lettuce for As and chinese cabbage > radish > lettuce for Cd. Table 5 Concentrations of Cd in Chinese cabbage, radish, and lettuce grown at the different Cd concentrations in soil. Cd conc. (mg kg -1 F.W.) Chinese cabbage Radish Lettuce Cd conc. (mg kg -1 ) leaves roots Leaves roots leaves roots Control 0.02a* 0.03a 0.05a 0.04a 0.17a 0.10a 5 0.13a 0.45a 0.15a 0.08ab 3.37b 3.20a 10 0.22a 0.93a 0.53a 0.16ab 3.78b 5.96a 25 0.59b 2.96b 1.59b 0.29b 11.32c 15.5b 50 1.03c 4.37bc 3.07c 0.67c 14.29c 12.9b 100 2.56d 6.09c 5.20d 1.08c 20.04d 45.4c *: within columns, means followed by the same letter are not significantly different at the 0.05 probability level using the F-test Table 6 Total Cd uptake in each plant of Chinese cabbage, radish, and lettuce grown in soils of different Cd concentrations. Absorbed Cd conc. (µg plant -1 ) Cd conc. (mg kg -1 ) Chinese cabbage Radish Lettuce Control192011 5 99 52 191 10 147 108 240 25 491 269 125 50 833 525 53 100 1,333 837 125 Both PTWI (provisional tolerable weekly intake) and MPL (maximum permissible level) values were proposed by the FAO/WHO joint codex commission for food safety. Table 7 shows the theoretical acceptable As and Cd concentrations in the upland soils with absorption curve. The acceptable As concentrations of upland soils for chinese cabbage, radish, and lettuce would be 4.2, 39.9, and 7.0 mg kg -1 , respectively. It means that the cultivation soil for chinese cabbage and lettuce must consider the concentration of As because of 6.0 mg kg -1 of concern level and 15 mg kg -1 of countermeasure level for soil contamination designated by ‘Soil Environment Conservation Law’ in Korea (1996). In case of Cd, the acceptable concentrations of upland soils for chinese cabbage, radish, and lettuce would be 2.3, 5.9, and 0.3 mg kg -1 , respectively. Therefore, the KIM ET AL. 17 th WCSS, 14-21 August 2002, Thailand 1873-8 cultivation soil for chinese cabbage and lettuce must consider the concentration of Cd, too. Table 7 Theoretical acceptable Cd and As concentration in the upland soils their absorption curve with chinese cabbage, radish, and lettuce. Index As Cd PTWI (µg kg -1 body weight)* 15 7 MPL (mg kg -1 FW)** 0.12 0.06 Chinese cabbage 4.2 2.3 Radish 39.9 5.9 Acceptable As and Cd concentraton in soils (mg kg -1 soil) Lettuce 7.0 0.3 Concern level (mg kg soil -1 )*** 6 1.5 Countermeasure level (mg kg soil -1 )*** 15 4.0 * Provisional Tolerable Weekly Intake proposed by the FAO/WHO joint codex commission. ** Maximum Permissible Levels of pollutants in food by the FAO/WHO joint codex commission. *** Concern and countermeasure levels of heavy metals for soil contamination in the agricultural soils designated by ‘Soil Environment Conservation Law’ in Korea (Minister of Environment, 1996) Conclusion Phytotoxicity and absorption of Cd and As were investigated with chinese cabbage, radish, and lettuce grown at the different concentration of upland soils. Growth retardation of radish and lettuce was shown on the As treated soils whereas growth retardation and leaf chlorosis of chinese cabbage and lettuce was shown at the early growing season on the Cd treated soils. The threshold Cd concentrations of growth damage resulting from the significant reduction (5%) of growth and yield of chinese cabbage and lettuce were 50-100 mg kg -1 and 10-25 mg kg -1 , respectively. The growth of radish and lettuce were significantly reduced at the 10-15 mg kg -1 and 10-25 mg kg -1 of As treated soils, respectively. However, there was no significant reduction of radish yield under 100 mg kg -1 of Cd treated soils and chinese cabbage yield under 30 mg kg -1 of As treated soils. As the concentrations of Cd and As in soils were increased, the contents of Cd and As in agricultural products were significantly increased, basically. The contents of Cd in the edible parts of chinese cabbage, radish and lettuce grown at the 5 mg kg -1 Cd treated soils were 0.13, 0.18 and 3.37 mg kg -1 FW, respectively. Total absorbed Cd for each vegetable tends to occur in the following order, chinese cabbage > radish > lettuce at the high Cd treated soils whereas lettuce absorbed more Cd than chinese cabbage and radish at the low concentration of Cd. In case of As, the contents of As in edible part of chinese cabbage, radish and lettuce grown at the 6 mg kg -1 Cd treated soils were 0.19, 0.03 and 0.04 mg kg -1 FW, respectively. Total absorbed As for each vegetable tends to occur in the order of chinese cabbage > radish > lettuce. References Aller, A.J., J.L., Bernal, M.J. del Nozal and L. Deban. 1990. Effects of selected trace elements on plant growth. J. Sci. Food Agric. 51:447-479. Efroymsom, R.A., M.E. Will, G.W. Suter II and A.C. Wooten. 1997. 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