Abstract:
To assess toxicity effects of cadmium on water spinach (Ipomoea aquatica), evaluate the cadmium accumulation in cadmium contaminated water at various concentrations under long-term cultivation and assess cadmium accumulation under shock loading contamination. The cultivation units were 45-L plastic bowls (diameter 60 cm x height 24 cm). Installed under transparent plastic roof to prevent rain. There were 4 replications in each cadmium concentration. The effluent of domestic wastewater treatment plant which contained sufficient nutrients for plant growth was mixed with cadmium chloride at various cadmium concentrations. The toxicity test conducted for 30 days revealed that cadmium concentration 7.6 mg/L had no toxicity effects on water spinach while concentration of 59.1 mg/L had chlorosis and plant die-off. The long-term cultivation showed that there was natural die-off and reduction of yield, as observed in control plots without cadmium addition. At cadmium concentration within 0.053 mg/L, normal yields were found while concentration of 0.446 mg/L had plant die-off since 40th day of cultivation. For low cadmium in water, i.e. within 0.053 mg/L, cadmium accumulated in roots higher than in leaves and stems, which were not much different. The accumulated level exceed European Commission (EU) standard for vegetable. Based on dietary intake rate of World Health Organization, water spinach grown in cadmium concentration of 0.005 mg/L can be consumed at the rate of 1,700 g/week. For high cadmium in water, i.e. 0.135-0.446 mg/L, cadmium accumulated highest in roots, stems and leaves respectively, and much higher than EU standard. Under shock loading of plant in cadmium concentration 0.148 mg/L for a short period, it was found that cultivation duration of 1 day reduction in cadmium contamination in plant to be within EU standard.
