遵义市湘江河表层沉积物中重金属赋存形态及潜在生态风险

Speciation and Ecological Risk of Heavy Metals in Surface Sediments of Xiangjiang River in Zunyi City

    摘要
  • 摘要: 遵义市湘江河流经主城区，沿岸人口密度大，流域内生活污水和工农业活动产生的重金属汇入湘江河，为了解该河段的重金属污染分布特征及评价潜在生态风险，采用改进的BCR连续提取法提取并分析遵义市主城区湘江河8个表层沉积物样本中9种重金属元素的赋存形态，分别使用电感耦合等离子体原子发射光谱法测定w（Cu）、w（Zn）、w（Pb）、w（Cd）、w（Cr）、w（Mn）和w（Ni），原子荧光光度法测定w（As）和w（Hg）.结果表明：①w（Cu）、w（Zn）、w（Pb）、w（Cd）、w（Cr）、w（Mn）、w（Ni）、w（As）和w（Hg）的平均值分别为64.89、313.75、75.93、1.44、93.95、1507.98、33.74、13.50和0.68 mg/kg，除w（As）外，其他重金属的平均值均高于贵州沉积物重金属背景值.②w（Cu）、w（Zn）、w（Pb）、w（Cd）、w（Mn）和w（Hg）在不同采样点间的变异系数分别为54.91%、93.33%、78.73%、85.00%、106.46%和93.44%，受人为活动的干扰较大.Cu与Cr、Zn与Pb、Cd与Pb之间存在极显著正相关关系（P < 0.01），其污染来源可能具有同源性.③重金属的赋存形态在不同采样点间的空间分布差异较大，Cu、Pb、Cr、Ni、As和Hg的主要赋存形态为残渣态，占比分别为52.72%、59.31%、84.39%、79.09%、89.14%和99.87%；Mn以酸提取态为主，占比为61.58%；Cd以可氧化态为主，占比为50.19%.次生相与原生相分布比值法（RSP）评价结果显示，Cr、Ni、As和Hg对湘江河水环境产生潜在生态危害的风险较低，Mn和Cd的生态危害风险较高.

     

    Abstract: The Xiangjiang River flows through the main urban area with high densities of population in Zunyi City. Heavy metals from domestic sewage, industrial and agricultural activities in the watershed flow into the Xiangjiang River. In order to explore the distribution characteristics of heavy metal pollution and to evaluate potential ecological risks, a modified BCR sequential extraction procedure was used to analyze the speciation distributions of Cu, Zn, Pb, Cd, Cr, Mn, Ni, As, and Hg in eight surface sediment samplings from the Xiangjiang River in Zunyi City. The w(Cu), w(Zn), w(Pb), w(Cd), w(Cr), w(Mn) and w(Ni) were analyzed by using inductively coupled plasma atom emission spectrometry (ICP-AES). The w(As) and w(Hg) were measured by the atomic fluorophotometer. The results showed that:(1) The average w(Cu), w(Zn), w(Pb), w(Cd), w(Cr), w(Mn), w(Ni), w(As), and w(Hg) were 64.89, 313.75, 75.93, 1.44, 93.95, 1507.98, 33.74, 13.50 and 0.68 mg/kg, respectively. All average concentrations of heavy metals exceeded the background levels in Guizhou Province, except fo As. (2) The coefficients of variation of w(Cu), w(Zn), w(Pb), w(Cd), w(Mn), and w(Hg) in different sampling sites were 54.91%, 93.33%, 78.73%, 85.00%, 106.46% and 93.44%, respectively, which was greatly influenced by human activities. There were significant positive correlations between Cu and Cr, Zn and Pb, Cd and Pb (P < 0.01). The heavy metals might come from the same source of pollution. (3) There were significant differences in speciation distribution of heavy metals between different sampling sites. The analysis of chemical speciation indicated that Cu, Pb, Cr, Ni, As, and Hg were mainly dominated by the residual fraction, and their average ratios in the total heavy metals were 52.72%, 59.31%, 84.39%, 79.09%, 89.14% and 99.87%, respectively. Mn mainly existed in acid-soluble extraction, the average ratio of which was 61.58%. Cd was mainly constituted of oxidizable fraction, the average ratio of which was 50.19%. The results of ratio of secondary phase to primary phase (RSP) assessment showed that Cr, Ni, As, and Hg showed lower potential ecological risk, while Mn and Cd showed higher potential ecological risk.

     

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