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    湛江高桥红树林沉积物理化性质与金属元素的空间分布

    Spatial distribution of physicochemical properties and metal concentration in mangrove sediments from Gaoqiao in Zhanjiang, Guangdong of Southern China.

    • 摘要: 以广东湛江国家级红树林自然保护区高桥核心区为研究区,在2 条垂直于海岸的样线A 和样线B 上,根据潮 汐淹没时间各选择3 个样点进行沉积柱取样,用于解析沉积物理化性质与金属元素空间分布特征。结果表明:沉 积物为粉鄄砂型质地,其中黏粒、粉粒和砂粒含量分别为(134)%、(3912)%和(4816)%;有机质含量范围为 0.2% ~3.7%,pH 值为2.5 ~7.3,交换性盐基总量为1.4 ~16.4 cmol/ kg,总氮含量0.01% ~0.2%,总磷含量130 ~ 435 mg/ kg;A、B 样线的沉积物粒度、pH 值、盐基总量、有机质含量、总氮含量、总磷含量等理化性质差异不显著。沉 积物中11 种金属的含量从高到低分别为Al(4.5% ~ 19.2%)、Fe(1.0% ~ 4.7%)、Mn(50.4 ~ 163.4 mg/ kg)、Cr (24.4 ~43.0 mg/ kg)、Zn(14.4 ~52.1 mg/ kg)、Pb(11.3 ~ 34.9 mg/ kg)、Ni(3.5 ~ 19.4 mg/ kg)、Co(3.0 ~ 7.7 mg/ kg)、Cu(1.4 ~9.6 mg/ kg)、As(1.4 ~5.8 mg/ kg)、Mg(0.2 ~0.9 mg/ kg),除Co、Cu、As、Fe 平均含量差异不显著外, 其他金属元素间差异显著;A 样线上Cr、Cu、Mn 含量显著高于B 样线,其他金属的含量差异不显著。沉积物基本理 化性质呈现明显的空间分布差异,低潮位沉积物的含砂量、pH 值更高;垂向梯度上,细颗粒(黏粒、粉粒)含量、pH 值、盐基总量、有机质含量、总磷含量、总氮含量均以表层值最高,自表层向下逐渐降低,而含砂量则相反。金属含 量表现为更低潮位点的金属含量低,但也因金属元素而异,潮位因素对不同金属分布的影响存在差异;各样点金属 含量垂向上均以表层最高,随着深度增加而降低。相关性分析表明:有机质与pH 值、含砂量负相关,而与细颗粒含 量正相关;金属元素含量除了与含砂量显著负相关、与pH 值之间相关性不显著外,其与盐基总量,有机质、黏粒、粉 粒含量均呈显著正相关关系;金属元素含量之间的相关性均达到极显著水平,反映了其相互伴生和同源的特征。

       

      Abstract: Taking Gaoqiao mangrove of Zhanjiang Mangrove National Nature Reserve as the study area, six sediment cores were sampled along two sample lines A and B, which were perpendicular to the coastline, and spatial distribution features of physicochemical properties and enrichment pattern of metal trace in sediment cores were analyzed. The content of metals, including major metals (Al, Fe and Mg) and trace metals (As, Co, Cr, Cu, Mn, Ni, Pb and Zn) and their possible relationships with physicochemical properties (particle size, pH, exchangeable base cations, total nitrogen, total phosphorus, and organic matter) in core sediment samples were evaluated. Analysis of physicochemical properties revealed that an overall predominance of silt and sand in the study area, the concentration of clay, silt and sand of sediment were (134)%,(3912)% and (4816)%, respectively, organic matters varied from 0.2% to 3.7%, 2.5 -7.3 for pH value, 1.4 -16.4 cmol/ kg for exchangeable base cations, 0.01% -0.2% for total nitrogen, and 130 - 435 mg/ kg for total phosphorus. The sediment quality parameters including grain size, pH value, exchangeable base cations, organic matter, total nitrogen and phosphorus were not significant (P 0.05) between A and B sample lines. The metal concentrations in sediment obtained in this study decreased in the following order,Al (4.5% -19.2%), Fe (1.0% -4.7%), Mn (50.4 -163.4 mg/ kg), Cr (24.4 -43.0 mg/ kg), Zn (14.4 -52.1 mg/ kg), Pb (11.3 -34.9 mg/ kg), Ni (3.5 -19.4 mg/ kg), Co (3.0 - 7.7 mg/ kg), Cu (1.4 - 9.6 mg/ kg), As (1.4 - 5.8 mg/ kg), Mg (0.2 - 0.9 mg/ kg). The difference was significant (P 0.05) among contents of metals excluding Co, Cu, As and Fe. The concentrations of Cr, Cu and Mn on line A were much higher than on line B. Spatial distribution varied markedly in physicochemical properties. The sand content and pH value increased with increasing distance from the seawall. Organic matter, total nitrogen and total phosphorus were affected by mangrove community type and hydrodynamics. Physicochemical properties varied obviously in vertical direction, parameters of physicochemical properties ( not including sand content in surface layer) were the highest, and decreased gradually from top to bottom layer. With increasing distance from the seawall, the metal concentration in core sediment decreased gradually with the tidal level but varied with metals; therefore, tidal level was not the solo factor affecting metal distribution in horizontal level. Similar to the trends of physicochemical properties, hierarchical variation in metal concentration was presented in a vertical direction: concentrations of metals were the highest in surface layer, and decreased gradually from top to bottom layer. Correlation analysis showed that organic matters were positively correlated with finer particles (P 0.01), but negatively correlated with pH value and sand content (P 0.01). A significantly negative correlation was detected between metal content and sand content, and metal concentration had no correlation with pH value. The metal concentration was positively correlated with exchangeable base cations, organic matter and fine particles (P 0.01). The associated or homologous features were detected according to the significant correlation among the metals.

       

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