STUDIES ON THE CRITERIA OF CADMIUM POLLUTION IN GROWTH MEDIA OF VEGETABLE CROPS BASED ON THE HYGIENIC LIMIT OF CADMIUM IN FOOD

ABSTRACT

A pot experiment and a sandy culture experiment grown with three vegetable crops of Chinese cabbage (B. chinensis L. cv. Zao-Shu 5), winter greens (B. var. rosularis Tsen et Lee cv. Shang-Hai-Qing), and celery (A. graveolens L. var. dulce DC. cv. Qing-Qin) were conducted, respectively. The initial soil and four incubated soils with different extractable cadmium (Cd) levels (0.15, 0.89, 1.38, 1.84, and 2.30 mg Cd kg⁻¹ soil) were used for the pot experiment. Five treatments were designed (0, 0.0625, 0.125, 0.250, and 0.500 mg Cd L⁻¹) in nutrient solution in the sandy culture experiment. Each treatment in both pot and sandy culture experiments was trireplicated. The objectives of the study were to examine Cd accumulation in edible parts of selected vegetable crops, its correlation with Cd concentrations in vegetable garden soil or in nutrient solution, and to evaluate the criteria of Cd pollution in vegetable garden soil and in nutrient solution based on the hygienic limit of Cd in vegetables. Cadmium concentrations in edible parts of the three selected vegetable crops were as follows: 0.01–0.15 mg kg⁻¹ fresh weight for Chinese cabbage, 0.02–0.17 mg kg⁻¹ fresh weight for winter greens, and 0.02–0.24 mg kg⁻¹ fresh weight for celery in the pot experiment, and 0.1–0.4 mg kg⁻¹ fresh weight for Chinese cabbage, 0.1–1.4 mg kg⁻¹ fresh weight for winter greens, and 0.05–0.5 mg kg⁻¹ fresh weight for celery in the pot experiment (except no-Cd treatment). Cadmium accumulation in edible parts or roots of the vegetable crops increased with increasing of cadmium concentration in the medium (soil or nutrient solution); and cadmium concentrations in edible parts of the test vegetable crops were significantly linearly related to the Cd levels in the growth media (soil and nutrient solution). Based on the regression equations established and the limit of cadmium concentration in vegetable products, the thresholds of Cd concentration in the growth medium evaluated was as follows: 0.5 mg kg⁻¹ soil of extractable Cd for soil and 0.02 mg L⁻¹ for nutrient solution. The high capacity for cadmium accumulation in the edible parts of different vegetable crops together with the absence of visual symptoms implies a potential danger for humans.

ACKNOWLEDGMENT

The authors thank the National Natural Science Foundation of China for the financial support (No. 39925024).