红树林湿地植物中Pd的累积特征

铂族元素(PGEs)中的钯(Pd)作为汽车尾气催化转换器(VECs)的催化剂被广泛应用,Pd在世界各国环境中的含量水平迅速增长,并进入食物链,其潜在威胁日益增大。本文以海南省东寨港红树林湿地为研究区,采集红树植物和沉积物样品,利用微波消解、ICP-MS测定其中的Pd。研究表明,在水平维度上,红树植物叶Pd的含量沿河口到外海方向呈现出递减趋势,说明了Pd的陆源性输入;沿光滩到林内方向,呈现出林内光滩林缘的特点。在垂直维度上,红树植物叶Pd的含量呈底部向顶部递减。相对于茎,红树植物叶Pd的含量明显偏低,说明红树植物主要通过根部从沉积物中吸收Pd并累积。对于不同年龄阶段的红树植物,茎Pd的含量为成熟幼龄老龄,叶Pd的含量为老龄成熟幼龄。红树植物叶Pd的含量季节变化明显,干季高于湿季。相对于国内外植物,东寨港红树植物Pd的含量属较低水平。本研究有助于阐明红树林湿地植物Pd的累积特征,同时对于红树林湿地的环境保护具有重要的科学意义。

Accumulation Characteristics of Pd in Mangrove Wetland Plants

Palladium (Pd), a member of the platinum group elements (PGEs), is widely used as the catalyst in automobile exhaust catalytic converters (VECs). The concentration of Pd in the environment worldwide increases rapidly and its potential threat is increasing by entering the food chain. In this paper, the mangrove wetland in the Dongzhai Harbor, Hainan Province, was taken as the research area to collect samples of mangrove plants. The Pd content was determined by the method of microwave digestion and ICP-MS. The results showed that Pd contents of mangrove leaves decreased horizontally from the estuary to the offshore, indicating that Pd in mangrove leaves came mainly from terrestrial origins, from the mudflat to the mangrove, showed the characteristics of interior forest > mudflat > forest margin. The vertical concentrations of Pd in mangrove leaves decreased from bottom to top. Compared with the stem, the concentrations of Pd in leaves of mangrove plants were significantly lower, indicating that mangrove plants absorbed and accumulated Pd from sediments mainly through roots. For mangrove plants of different ages, concentrations of Pd in stems and leaves followed the trend of mature > young > old and the trend of old > mature > young, respectively. The seasonal variation of Pd contents in mangrove leaves was significant, higher in the dry season than in the wet season. Compared with domestic and foreign plants, the concentrations of Pd in mangrove plants in the Dongzhai Harbor were lower. This study elucidated the accumulation characteristics of Pd in mangrove wetlands, and had important scientific significance in the environmental protection of mangrove wetlands.