白令海峡与北冰洋太平洋扇区表层沉积物中典型痕量金属环境基线值及生态风险

Trace metals are important components of the Arctic ecosystem. Many trace metals act as a catalyst in the marine organisms, which will motive, adjust or inhibit the biochemical reaction. Trace metals have become the key issue of the international joint research program GEOTRACES. After long-distance transmission through the atmosphere, rivers and ocean currents, trace metals have transferred into the Arctic Ocean and accumulated into the sediments by adsorption, flocculation and bioaccumulation. Due to the complex depositional environment and feedback to the rapid global climate change in Arctic, trace metals in the sediments will re-enter into the Arctic Ocean marine ecosystem by flocculation, bioaccumulation and food chain amplification. Sediment has become the most important “sink” and “source” of trace metals in Arctic Ocean. In this study, 71 surface sediment samples have been collected from the Pacific sector of the Arctic Ocean and the Bering Strait. The concentration levels of trace metals represented by Arsenic, Cadmium, Cobalt, Chromium, Copper, Mercury, Palladium, Lead, Platinum, Selenium and Zinc will be analyzed. The environmental baseline values of typical trace metals will be explored. The relationship among the depositional environment, characteristics of the overlying water, and the distribution of the trace metals will be studied. In the end, several methods will be used to evaluate the potential ecological risk of the typical trace metals considering the influence caused by the depositional environment and overlying water. It will be a great scientific significance on disclosing the environmental baseline value and ecological risk of typical trace metals of sediments in the study area.

痕量金属是北冰洋生态系统的重要组分，许多痕量金属在海洋生物体中起催化剂作用，激发、调控或抑制生化反应的进行，是国际重大联合研究GEOTRACES计划的关键主题。痕量金属主要通过大气、河流及洋流等长距离传输进入北冰洋太平洋扇区，通过吸附、絮凝、生物积累等过程，转移到沉积物中，由于该区域复杂的沉积条件及对全球气候快速变化的响应,沉积物中的痕量金属通过絮凝、沉淀、解吸附等重新进入水体和生物体,并通过生物富集和食物链放大等过程影响海洋环境，沉积物已成为最重要的汇和源。课题采集白令海峡及北冰洋太平洋扇区表层沉积物样品71个，分析As、Cd、Co、Cr、Cu、Hg、Pd、Pb、Pt、Se、Zn等为代表的多种痕量金属浓度水平及空间差异，探究其环境基线值；分析沉积环境及上覆水环境要素对其生物有效性的影响方式与程度，运用多种方法评估其生态风险。对揭示该区域沉积物痕量金属环境基线值及生态风险趋势具有科学意义

为了系统全面地考察白令海峡与北冰洋太平洋扇区（包括楚科奇海、波弗特海与加拿大海盆）痕量金属和铂系贵金属的污染程度和影响因素，以及它们对环境的潜在生态风险，本研究采集了白令海峡与北冰洋太平洋扇区表层沉积物样品进行了分析；测定分析了具有典型意义的24种痕量金属、生源性因子Cd、TOC、THg、MeHg及铂族元素（Pt、Pd和Rh）的浓度分布，我们发现As、Cr、Zn的浓度与北极其他海域相当或者略低，Cd在目标区域整体浓度水平较高，As、Co、Cu、Cr、Ni、Pb、Hg、MeHg在目标区域可能存在异常累积，多数分布于北冰洋深海盆；Cd的浓度分布与TOC的分布基本一致，两者呈现明显的正相关，而白令海陆架上的TOC从西向东递减，导致Cd靠近阿拉斯加一侧浓度降低；MeHg与TOC呈线性相关。总之，Cd、THg、MeHg表现出与As、Co、Cr、Cu、Ni、Pb、Zn明显不同的空间分布，其中Cd在白令海峡两侧陆架区浓度水平均较高，深海浓度很低；THg在白令海存在异常累积，深海浓度亦很低；MeHg则只在南楚科奇海域含量较大。Pt、Pd和Rh的浓度范围分别是0.67-8.73ng/g、0.83-13.31ng/g和0.04-1.54 ng/g，平均值分别为2.87 ng/g、4.83 ng/g和0.37 ng/g。初步探索了其来源及分布模式，发现 Pt、Pd、Rh在沉积物中的累积主要来自于沉积岩石中铂系贵金属的贡献，且沉积环境并不影响其分布。运用相对频率累积法与标准化方法对基线进行确认，得出金属元素As、Cr、Cu、Zn、Co、Pb的基线值分别为14.53±3.61 mg/kg、53.43±10.03 mg/kg、17.22±7.75 mg/kg、80.59±20.05 mg/kg、11.79±5.56 mg/kg、11.30±2.55 mg/kg。而Hg、Cd、Ni的基线值分别为0.037 mg/kg、0.23 mg/kg、 68 mg/kg。使用层次分析法（AHP）对目标区域进行生态风险评价，结果表明，研究区域内风险等级最高的为Ni，有93.9％的样品中显示Ni为中等风险，其次为铜（54.5％）和锌（27.3％）。