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不同潮位本土与外来红树植物根系和沉积物重金属的分布和富集特征

Distribution and enrichment characteristics of heavy metals in root and sediments of native and exotic mangrove plants at different tidal levels

  • 摘要: 为比较不同潮位下本土与外来红树植物根系对重金属吸收能力的差异,本研究以本土红树海莲(Bruguiera sexangula (Lour.) Poiret)与外来红树无瓣海桑(Sonneratia apetala Buchanan-Hamilton)为研究对象,测定了两树种在低潮位(LT)、中潮位(MT)和高潮位(HT)下根系、根际和非根际沉积物的理化性质及其Cr、Hg、Cd、Zn的含量;测定了根系的富集系数(BCF)、综合富集系数(CEF)、生理指标(根系活力、根表铁膜)并对沉积物进行了污染评价。结果显示:受树种、潮汐和根际效应影响,两树种沉积物的重金属、有机碳(SOC)、有机质(SOM)含量和酸度均为LT>MT>HT,无瓣海桑沉积物重金属含量较海莲高,其中海莲的根际沉积物重金属含量较非根际沉积物高,无瓣海桑则相反;海莲根系中的重金属含量、BCF、CEF整体高于无瓣海桑,根系活力与铁膜含量与沉积物重金属含量密切相关。综上,二者虽不属于超富集植物,但3个潮位下的两树种根系对沉积物中重金属均有一定的吸收能力,本土红树植物海莲根系富集重金属能力整体强于外来红树植物无瓣海桑。

     

    Abstract: To investigate species-specific differences in heavy metal accumulation under varying tidal regimes, the native mangrove Bruguiera sexangula (Lour.) Poiret and the exotic species Sonneratia apetala Buchanan-Hamilton were selected for comparative analysis. Concentrations of Cr, Hg, Cd, and Zn were quantified in roots, rhizosphere sediments, and non-rhizosphere sediments at low (LT), middle (MT), and high (HT) tidal zones. Parameters evaluated included bioconcentration factor (BCF), comprehensive enrichment factor (CEF), root physiological indices (root activity and iron plaque formation), and sediment contamination profiles. Results revealed that sediment characteristics, including heavy metal content, soil organic carbon (SOC), soil organic matter (SOM), and acidity, followed the gradient LT>MT>HT. Sediments surrounding S. apetala exhibited higher overall heavy metal concentrations than those associated with B. sexangula. In B. sexangula, heavy metal concentrations were elevated in rhizosphere sediments relative to non-rhizosphere sediments, whereas the inverse pattern was observed in S. apetala. Across tidal levels, both BCF and CEF values were higher in B. sexangula roots, accompanied by greater root activity and iron plaque deposition, which were positively correlated with sediment heavy metal content. Although neither species functioned as a hyperaccumulator, both demonstrated capacity for root-mediated uptake of heavy metals across tidal zones. Notably, B. sexangula exhibited a more pronounced accumulation potential than S. apetala, highlighting its ecological value for intertidal heavy metal remediation.

     

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