沙尘和人为影响下胶州湾大气微量元素溶解-沉降特征与源解析

Nowadays, natural change and anthropogenic activity are increasingly enhanced, which have resulted in serious atmospheric pollution phenomena such as sand storm and dust-haze. In addition, these atmospheric pollutants can be transported into the sea via atmospheric deposition, hence making significant effects on marine ecosystem. For that reason, this research project focuses on a typical semi-enclosed bay: Jiaozhou Bay, which is significantly influenced by both natural change and anthropogenic activities in China. We plan to analyze the particle size distribution, solubility as well as bio-availability of atmospheric trace elements based on one-year’s sampling of atmospheric total suspended particle and size-fractionated aerosol samples. Besides, dry and wet deposition samples are also collected to calculate the dry and wet deposition fluxes of trace elements into Jiaozhou Bay, as well as to study on their seasonal patterns. Then, we use atmospheric dry deposition model to indirectly estimate the dry deposition velocity of each trace element, analyzing the influencing mechanism of particle size and meteorological factors on dry deposition velocity. Moreover, based on the comparison of river and point source input loads, we would like to evaluate the percentage of atmospheric deposition in the total external loadings of trace elements into Jiaozhou Bay. In the end, we plan to analyze the sources and their relative contributions to these trace elements quantificationally by means of combination of statistical analysis, receptor models and airmass backward trajectory model. This project could not only provide data support for systematically evaluating the effects of atmospheric deposition of trace element on typical gulf ecosystem, but also further deepen the understanding of biogeochemical cycle process of trace elements in marginal seas.

当前，自然变化和日益增强的人类活动引发了以沙尘暴和灰霾为代表的严重大气污染问题；同时，这些污染物质又可通过沉降的方式输送入海，并对近海生态系统产生重要影响。基于此，本项目聚焦我国受自然变化和人类活动影响显著的典型海湾——胶州湾，通过采集一年的大气总悬浮颗粒物和分粒级气溶胶样品，分析大气微量元素的粒径分布特征和溶解度，评价其生物有效性。同时，同步收集干、湿沉降样品，估算大气微量元素沉降入海的通量，分析其季节变化特征，并运用大气干沉降模型间接估算各微量元素的干沉降速率，剖析粒径和气象因素对其的影响机制。通过与河流和点源排污负荷对比，评价大气沉降在胶州湾微量元素外源输入中的地位；最后，综合运用统计分析、受体模型和气团后向轨迹模型，量化解析大气微量元素的来源及相对贡献。本项目的开展可为评价大气微量元素沉降对典型海湾生态系统的影响提供数据支持，同时有助于进一步加深对元素生物地球化学循环过程的认识。

大气沉降是陆源矿物尘土和人为源污染物向海洋传输的重要方式之一，气溶胶中的微量元素尤其是重金属元素会严重危害自然环境和人体健康。本研究采集了胶州湾的大气总悬浮颗粒物和分粒级气溶胶样品，聚焦大气微量元素浓度和沉降通量及其季节变化特征和影响因素，微量元素粒径和化学形态分布，溶解度及生物有效性特征以及来源开展系统性研究，主要结论如下：1）胶州湾大气总态微量元素的浓度在世界近海区域处于较高水平，溶解态微量元素的浓度和干沉降通量处于中等水平，且呈现明显的季节变化特征，表明胶州湾的大气微量元素污染较重，亟待开展治理；2）源排放强度（采暖、沙尘）和气象条件（降水量、季风）以及气团的远距离传输是大气微量元素浓度和沉降通量季节变化的主控因素；3）粒径分析结果表明，Al、Fe、Co、Cu、Sr、Ti、Ba均主要集中在＞5.8 μm的粗粒径范围内，而Mn、Zn、Pb、Ni、Cd、Cr、V、Mo、Sn则主要存在于粒径＜2.1 μm的细粒径颗粒物中；化学形态分析表明，多数元素的赋存形态主要为可溶态与可交换态（F1）和碳酸盐态、可氧化态与可还原态（F2），即此类微量元素的生物有效性较高，沉降入海后易于被海洋生物利用或对其产生较大影响；4）胶州湾大气Al、Fe、Mn、Co、Zn具有较高的干沉降速率，而Se、Pb、Cd、Cr的干沉降速率较低，且呈现一定的季节变化，可能主要受控于粒径大小；5）人为源污染元素如V、Zn、Ni、Cu、Co的溶解度相对较高（＞35%），而地壳源元素Al、Fe的溶解度较低（＜4%），颗粒物负载量、元素总态浓度大小以及大气酸化过程（pH）等均对其有重要影响；6）结合河流输入和点源排污，尽管整体上大气沉降在胶州湾微量元素总外源输入中的占比较低，但部分元素如溶解态Zn和Si的大气输入对胶州湾海水的贡献不容忽视。源解析结果表明，Al、Fe、Sr、Ti等元素主要源自于矿物沙尘，Zn、Pb、Cd等来自于多种人为源排放，而V、Ni则主要为船舶航运排放。本研究对深入认识元素的生物地球化学循环意义重大。