Wang He, Jia Yongfeng, Wang Shaofeng, Zhu Huijie, Wu Xing
Key Laboratory of Terrestrial Ecological Process, Institute of Applied Ecology, Chinese Academy of Sciences, No. 72 Wenhua Road, Shenyang, China.
J Hazard Mater. 2009 Aug 15;167(1-3):641-6. doi: 10.1016/j.jhazmat.2009.01.012. Epub 2009 Jan 16.
The bioavailability of heavy metals strongly depends on their speciation in the environment. The effect of different chemical speciations of cadmium ions (i.e. adsorbed on different oxide minerals) on its bioavailability to wetland plant Phragmites australis was studied. Goethite, magnetite, gibbsite, alumina, and manganese oxide were chosen as representatives of metal (hydr)oxides commonly present in sediment. The cultivar system with Hoagland solution as nutrition supply, and single metal oxide with adsorbed Cd as contaminant was applied to study Cd accumulation by P. australis. The bioaccumulation degree in root after the 45-day treatment followed the order: Al(OH)(3)>Al(2)O(3)>Fe(3)O(4)>MnO(2)>FeOOH. The concentration of Cd in stem and leaf followed a similar order although it was considerably lower than that in root. Low-molecular-weight organic acids (LMWOAs), acetic acid, malic acid and citric acid were used to evaluate the desorbability of Cd from different oxides, which can be indicative of Cd-oxide bonding strength and Cd bioavailability. Desorption of Cd by acetic acid and malic acid followed the order: Al(OH)(3)>Fe(3)O(4)>Al(2)O(3)>FeOOH>MnO(2), while by citric acid: Al(OH)(3)> or =Al(2)O(3)>Fe(3)O(4)>FeOOH>MnO(2). This was consistent with the Cd accumulation degree in the plant. Cd adsorbed on Al(OH)(3) was the most easily desorbable species and most bioavailable to P. australis among the oxide minerals, whereas MnO(2) adsorbed Cd was least desorbable by LMWOAs hence constituted the least bioavailable Cd species adsorbed on the oxide minerals.
重金属的生物有效性在很大程度上取决于它们在环境中的形态。研究了镉离子不同化学形态（即吸附在不同氧化物矿物上）对湿地植物芦苇生物有效性的影响。选择针铁矿、磁铁矿、三水铝石、氧化铝和氧化锰作为沉积物中常见金属（氢）氧化物的代表。采用以霍格兰溶液为营养供应的栽培系统，以吸附镉的单一金属氧化物为污染物，研究芦苇对镉的积累。处理45天后，根部的生物积累程度顺序为：Al(OH)(3)>Al(2)O(3)>Fe(3)O(4)>MnO(2)>FeOOH。茎和叶中镉的浓度顺序相似，尽管其浓度远低于根部。使用低分子量有机酸（LMWOAs）、乙酸、苹果酸和柠檬酸来评估镉从不同氧化物中的解吸能力，这可以指示镉与氧化物的结合强度和镉的生物有效性。乙酸和苹果酸对镉的解吸顺序为：Al(OH)(3)>Fe(3)O(4)>Al(2)O(3)>FeOOH>MnO(2)，而柠檬酸的解吸顺序为：Al(OH)(3)> 或 =Al(2)O(3)>Fe(3)O(4)>FeOOH>MnO(2)。这与植物中镉的积累程度一致。在氧化物矿物中，吸附在Al(OH)(3)上的镉是最容易解吸的物种，对芦苇的生物有效性最高，而MnO(2)吸附的镉最难被LMWOAs解吸，因此是吸附在氧化物矿物上生物有效性最低的镉物种。
