Podar Dorina, Ramsey Michael H
Centre for Environmental Research, Department of Biology and Environmental Science, School of Life Sciences, University of Sussex, Falmer, Brighton, East Sussex BN1 9QJ, UK.
Sci Total Environ. 2005 Jul 15;347(1-3):53-63. doi: 10.1016/j.scitotenv.2004.11.024.
An eight-fold underestimate of the potential Cd exposure to humans via ingestion of lettuce grown in moderately alkaline soil has been measured experimentally. Current models of Cd uptake by leafy vegetables, which are used in risk assessment (e.g. CLEA in UK) predict higher concentration factors in acid than in alkaline soils. Experimental evidence shows that Cd uptake, although it decreases with increasing pH from acid to neutral soils, increases again in alkaline soils, confirming recent finding from other workers. The concentration of Zn in the soil also significantly affects the uptake of Cd, although this is not included in the current prediction models either. The effect of Zn on the uptake of Cd by plants is greater in slightly alkaline soils (pH 7.7) than in slightly acidic or neutral soils. High concentrations of Zn in soil (1000 mg/kg), which are often associated with elevated Cd levels, further increase the Cd concentration factor to values 12 times higher than that predicted by the CLEA model. This is due in part to the effect of the high soil Zn on reducing the above-ground biomass of the plants.
通过食用在中度碱性土壤中种植的生菜，对人类潜在镉暴露量的低估已通过实验测定为八倍。目前用于风险评估的叶类蔬菜镉吸收模型（如英国的CLEA）预测，酸性土壤中的浓缩系数高于碱性土壤。实验证据表明，镉的吸收量虽然从酸性土壤到中性土壤随pH值升高而降低，但在碱性土壤中又会增加，这证实了其他研究人员最近的发现。土壤中锌的浓度也会显著影响镉的吸收，尽管目前的预测模型中也未包含这一点。锌对植物吸收镉的影响在微碱性土壤（pH 7.7）中比在微酸性或中性土壤中更大。土壤中高浓度的锌（1000毫克/千克）通常与镉含量升高有关，这进一步将镉浓缩系数提高到比CLEA模型预测值高12倍的值。这部分是由于高土壤锌对降低植物地上生物量的影响。
