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

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

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

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

Na2HAsO4, to 3, 6, 10, 15, 30 mg kg-1 of As soil and CdCl2·2½H2O, 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 (HNO3: H2SO4: HClO4 = 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)

(g kg-1)

Avail

P2O5

Clay (%)

As*

(mg kg-1)

Cd** (mg kg-1)

* 1N-HCl soluble Arsenic

** 0.1N-HCl soluble cadmium

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

Observed symptom Radish, Lettuce : growth

retardation

Chinese cabbage : chlorosis

in seedling leaves

Phytotoxicity

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

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

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,

0

20

40

60

80

100

120

Cd conc.(mg/kg soil)

C Cabbage Radish Lettuce

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.)

As conc

(mg kg-1)

*: 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

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,

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.)

Cd conc

(mg kg-1)

*: 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)

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

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

PTWI (µg kg-1

Acceptable As and Cd concentraton

in soils (mg kg-1 soil)

* 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

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