Ge Y, Murray P, Hendershot W H
Department of Natural Resource Sciences, Macdonald Campus, McGill University, Ste-Anne-de-Bellevue, Québec, Canada H9X 3V9.
Environ Pollut. 2000 Jan;107(1):137-44. doi: 10.1016/s0269-7491(99)00119-0.
Urban soils often contain concentrations of trace metals that exceed regulatory levels. However, the threat posed by trace metals to human health and the environment is thought to be dependent on their speciation in the soil solution rather than the total concentration. Three inactive railway yards in Montréal, Québec, were sampled to investigate the speciation and bioavailability of Cd, Cu, Ni, Pb and Zn. Soil solutions were obtained by centrifuging saturated soil pastes. In the soil solutions, up to 59% of the dissolved Cd was in its free ionic form. For Cu, Pb and Zn, organic complexes were the predominant species. Over 40% of Ni was present as inorganic complexes if the solution pH exceeded 8.1. Multiple regression analyses showed that pH and total metals in soil were significantly correlated with the activities of free metal ions, except for Cd(2+), which only had a weak correlation with soil pH. Free, dissolved and total soil metals were tested for their ability to predict metal uptake by plants in the field. However, none of these metal pools were satisfactory predictors. The results indicated that in these urban soils, trace metals were mainly in stable forms and bioavailability was extremely low.
城市土壤中痕量金属的含量常常超过监管水平。然而，痕量金属对人类健康和环境构成的威胁被认为取决于它们在土壤溶液中的形态，而非总浓度。对魁北克省蒙特利尔市的三个废弃铁路调车场进行了采样，以研究镉、铜、镍、铅和锌的形态及生物有效性。通过对饱和土壤糊剂进行离心来获取土壤溶液。在土壤溶液中，高达59%的溶解态镉呈游离离子形式。对于铜、铅和锌而言，有机络合物是主要形态。如果溶液pH值超过8.1，超过40%的镍以无机络合物形式存在。多元回归分析表明，土壤中的pH值和总金属含量与游离金属离子的活性显著相关，但镉离子（Cd(2+)）除外，它与土壤pH值的相关性较弱。对土壤中的游离态、溶解态和总金属进行了测试，以评估它们预测田间植物对金属吸收的能力。然而，这些金属库均不是理想的预测指标。结果表明，在这些城市土壤中，痕量金属主要以稳定形态存在，生物有效性极低。
