The objective of this study is to clarify the effects of the thickness of soil dressing, the percolation patterns of plowsole and subsoil on reducing cadmium （Cd） uptake, and growth and yields of rice plants. Six st...The objective of this study is to clarify the effects of the thickness of soil dressing, the percolation patterns of plowsole and subsoil on reducing cadmium （Cd） uptake, and growth and yields of rice plants. Six stratified paddy field models, three patterns of soil dressing layer and two percolation patterns were used for the experiments. These models had 12.5 cm, 15.0 cm and 25.0 cm thickness of soil dressing layer and 15 cm thickness of underlying polluted soil layer, whose Cd concentration was about 1.81 mg·kg^-1. As a result Cd concentration of brown rice was lower than 0.04 mg·kg^-1 for the models with the close system percolation, while that in the open system percolation models were lower than 0.17 mg.kgl.When the thickness of soil dressing became lower, Cd concentrations with the open system percolation models showed significantly higher values than those of the other models （5% of significant level）. But any significant difference was not found in the growth and yield among these models. As above mentioned, it was found that Cd concentration in rice grains was affected by the thickness of soil dressing and percolation patterns.展开更多
Cadmium(Cd), a common toxic heavy metal in soil, has relatively high bioavailability, which seriously threatens agricultural products. In this study, 8 different soils with contrasting soil properties were collected f...Cadmium(Cd), a common toxic heavy metal in soil, has relatively high bioavailability, which seriously threatens agricultural products. In this study, 8 different soils with contrasting soil properties were collected from different regions in China to investigate the Cd transfer coefficient from soil to Chinese cabbage(Brassica chinensis L.) and the threshold levels of Cd in soils for production of Chinese cabbage according to the food safety standard for Cd. Exogenous Cd(0–4 mg kg^(-1)) was added to the soils and equilibrated for 2 weeks before Chinese cabbage was grown under greenhouse conditions. The influence of soil properties on the relationship between soil and cabbage Cd concentrations was investigated. The results showed that Cd concentration in the edible part of Chinese cabbage increased linearly with soil Cd concentration in 5 soils, but showed a curvilinear pattern with a plateau at the highest dose of exogenous Cd in the other 3 soils. The Cd transfer coefficient from soil to plant varied significantly among the different soils and decreased with increasing soil p H from 4.7 to 7.5. However, further increase in soil pH to > 8.0 resulted in a significant decrease in the Cd transfer coefficient. According to the measured Cd transfer coefficient and by reference to the National Food Safety Standards of China, the safety threshold of Cd concentration in soil was predicted to be between 0.12 and 1.7 mg kg^(-1) for the tested soils. The predicted threshold values were higher than the current soil quality standard for Cd in 5 soils, but lower than the standard in the other 3 soils. Regression analysis showed a significant positive relationship between the predicted soil Cd safety threshold value and soil p H in combination with soil organic matter or clay content.展开更多
文摘The objective of this study is to clarify the effects of the thickness of soil dressing, the percolation patterns of plowsole and subsoil on reducing cadmium （Cd） uptake, and growth and yields of rice plants. Six stratified paddy field models, three patterns of soil dressing layer and two percolation patterns were used for the experiments. These models had 12.5 cm, 15.0 cm and 25.0 cm thickness of soil dressing layer and 15 cm thickness of underlying polluted soil layer, whose Cd concentration was about 1.81 mg·kg^-1. As a result Cd concentration of brown rice was lower than 0.04 mg·kg^-1 for the models with the close system percolation, while that in the open system percolation models were lower than 0.17 mg.kgl.When the thickness of soil dressing became lower, Cd concentrations with the open system percolation models showed significantly higher values than those of the other models （5% of significant level）. But any significant difference was not found in the growth and yield among these models. As above mentioned, it was found that Cd concentration in rice grains was affected by the thickness of soil dressing and percolation patterns.
基金supported by the Special Fund for Environment-Scientific Research in the Public Interest of China (No. 201409041)the Special Fund for Agro-Scientific Research in the Public Interest of China (No. 201403015)the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institute, China
文摘Cadmium(Cd), a common toxic heavy metal in soil, has relatively high bioavailability, which seriously threatens agricultural products. In this study, 8 different soils with contrasting soil properties were collected from different regions in China to investigate the Cd transfer coefficient from soil to Chinese cabbage(Brassica chinensis L.) and the threshold levels of Cd in soils for production of Chinese cabbage according to the food safety standard for Cd. Exogenous Cd(0–4 mg kg^(-1)) was added to the soils and equilibrated for 2 weeks before Chinese cabbage was grown under greenhouse conditions. The influence of soil properties on the relationship between soil and cabbage Cd concentrations was investigated. The results showed that Cd concentration in the edible part of Chinese cabbage increased linearly with soil Cd concentration in 5 soils, but showed a curvilinear pattern with a plateau at the highest dose of exogenous Cd in the other 3 soils. The Cd transfer coefficient from soil to plant varied significantly among the different soils and decreased with increasing soil p H from 4.7 to 7.5. However, further increase in soil pH to > 8.0 resulted in a significant decrease in the Cd transfer coefficient. According to the measured Cd transfer coefficient and by reference to the National Food Safety Standards of China, the safety threshold of Cd concentration in soil was predicted to be between 0.12 and 1.7 mg kg^(-1) for the tested soils. The predicted threshold values were higher than the current soil quality standard for Cd in 5 soils, but lower than the standard in the other 3 soils. Regression analysis showed a significant positive relationship between the predicted soil Cd safety threshold value and soil p H in combination with soil organic matter or clay content.
