铬污染人工湿地薏米对铬的积累和分布

Accumulation and distribution of chromium in Coix lacryma-jobi in constructed wetland treated with domestic sewage

关键词:  铬, 薏米, 亚细胞水平, 人工湿地, 转运系数

Key words:  chromium, Coix lacryma-jobi, subcellular, constructed wetland, transfer coefficient

摘要:

通过桶栽构筑微型垂直流人工湿地, 在生活污水中添加不同浓度的Cr⁶⁺(0、20、40 mg ·L^-1,用K₂Cr₂O₇配置),研究了在铬(Cr)污染条件下薏米不同器官和亚细胞水平对铬的积累及分布。结果表明:薏米根茎叶铬含量均随铬处理浓度的提高和处理时间的延长而显著增加,根部铬含量最高,其次是叶片,茎部铬含量最低。随着铬处理浓度的增加和时间的延长,细胞壁和液泡中的铬含量大幅上升,但细胞器中铬含量上升幅度较低,根部细胞壁、细胞器、可溶部分及液泡铬含量均显著大于茎、叶相关细胞组分,根、茎、叶亚细胞水平铬含量分布均依次为细胞壁>液泡>细胞器。其中,细胞壁铬含量极显著大于液泡以及其他细胞器,薏米根部把大部分铬隔离在细胞壁中,从而降低了地上部分对铬的吸收,导致地上部分干重、鲜重的受抑制程度均低于根系,表明根部细胞壁是降低铬在薏米体内积累的重要屏障, 也是薏米在低浓度铬胁迫下能够存活的根本保证。

Abstract:

Vertical ow wetland microcosms(VFWM)treated with domestic sewage were set up to study the accumulation and distribution of chromium(Cr)in organs(roots, stems and leaves)and subcellular compounds of Coix lacryma-jobi 0, 20, 40 mg·L^-1 of K₂Cr₂O₇ were added into domestic sewage, respectively. The results showed that the content of Cr in the plants was increased significantly with the prolong of Cr⁶⁺ stress and the increase of Cr⁶⁺ concentration, and the Cr content in the root was the highest, followed by leaves and stems. Cr concentrations in cell walls and vacuoles were increased significantly with Cr⁶⁺ exposure, but Cr content in organelles was lower than that of cell walls and vacuoles. Cr concentrations in cell walls, organelles and vacuoles of the roots were significantly higher than those of stems and leaves. The distributions of Cr concentration from the highest to the lowest were cell walls, vacuoles and cellorgans. Under Cr stress, most Cr was fixated on the cell walls of the roots, thereby limited further transportation of Cr to stems and leaves and reduced the toxicity of Cr to shoots. C. lacryma-jobi can absorb Cr effectively in the wastewater. Cell wall was one of the important physiological mechanisms for chromium detoxification in C. lacryma-jobi.