摘要:大气沉降作为陆源物质输送入海的重要途径之一，已成为国际上大气科学、海洋科学与环境科学交叉研究的热点之一。大气中的生源要素沉降入海后可能会对海洋生态系统产生重要影响。基于此，选择我国北方的一个典型海湾--胶州湾，采集了为期一年（2015年6月至2016年5月）的气溶胶总悬浮颗粒物（TSP，Total Suspended Particulate）和干沉降样品，测定了其中活性硅酸盐（SiO₃-Si，Reactive Silicate）的含量，在此基础上分析了大气中SiO₃-Si的浓度、干沉降通量和干沉降速率（V_d，Dry Deposition Velocity），并初步评估了其沉降入海的生态效应。结果表明：胶州湾大气TSP中SiO₃-Si的年均浓度为（1.98±1.22）nmol/m³，呈夏秋季低，冬春季高的显著季节分布特征。大气SiO₃-Si浓度由青岛沿岸至黄、东海呈明显下降梯度，结合相关性分析，表明亚洲沙尘的远距离传输和矿物尘土再悬浮是中国东部陆架边缘海大气SiO₃-Si的主要来源。胶州湾气溶胶SiO₃-Si干沉降通量为8.48 mmol m^-2 a^-1，沉降负荷达87.8 t/a，显著高于同期湿沉降，可占胶州湾SiO₃-Si外源输入（包括干湿沉降和河流输入）的10.3%，表明干沉降是胶州湾SiO₃-Si的重要输入源之一。干沉降中较低的Si：N摩尔比（0.16±0.22）暗示大气干沉降可能是导致较长时间以来胶州湾水体Si限制的一个重要潜在因素，根据Redfield比值估算干沉降带来的SiO₃-Si输入可以支持674 mg C m^-2 a^-1的新生产力，可占胶州湾新生产力的5.3%，表明大气SiO₃-Si的干沉降会对胶州湾生态系统产生一定影响。本研究系统解析了胶州湾大气SiO₃-Si的干沉降特征，首次评估了气溶胶SiO₃-Si的干沉降负荷在胶州湾外源输入中的重要性，对深入理解近海Si的生物地球化学循环过程具有重要意义。



Abstract:As one of the important routes for terrigenous matters entering marine ecosystem, atmospheric deposition has been one of the focuses of the interdisciplinary research in the atmospheric sciences, marine sciences, and environmental sciences internationally. In addition, atmospheric deposition is also a crucial manner to eliminate natural and anthropogenic pollutants from the atmosphere. Biogenic elements, including carbon, nitrogen, phosphorus, and silicon, etc., are the essential elements for the growth of marine phytoplankton. Thus, their inputs via atmospheric dry and wet depositions are likely to exert profound effects on the marine ecosystem. Study on the atmospheric deposition in the eutrophic China marginal seas is very important. As is well known, Jiaozhou Bay is a typical bay suffered from both the natural and anthropogenic emissions. It is an ideal area for explaining the potential effects from atmospheric deposition of biogenic elements on the marine ecosystem. In this study, based on one-year sampling for collecting the total suspended particulates (TSP) in the atmosphere and dry deposition samples between June 2015 and May 2016 at a shore-based site along Jiaozhou Bay, the contents of reactive silicate (SiO₃-Si) were determined for analyzing the concentration, dry deposition flux, and the dry deposition velocity (V_d) of SiO₃-Si. In addition, the potential ecological effects of SiO₃-Si dry deposition on the Jiaozhou Bay were preliminarily assessed. The results showed that the average concentration of SiO₃-Si was (1.98 ±1.22) nmol/m³ during the sampling period, with an obvious seasonal pattern of the higher values mainly occurred in winter and spring and the lower concentrations appeared in summer and autumn. The concentrations of SiO₃-Si showed a distinct trend of decrease from Qingdao coastal region to the Yellow Sea and East China Sea. The correlation analysis indicated that the long-range transport of Asian dusts and the resuspended of mineral dusts were the dominating source of atmospheric SiO₃-Si in Jiaozhou Bay and even in the entire China marginal seas. The estimated dry deposition flux of SiO₃-Si was 8.48 mmol m^-2 a^-1 with a deposition loading of 87.8 t/a, which was significantly larger than the reported values by wet deposition. In addition, the dry deposition loading accounted for 10.3% of the total exogenous inputs (including dry and wet deposition as well as riverine input) of SiO₃-Si surrounding Jiaozhou Bay, revealing the dry deposition was a non-negligible input source of SiO₃-Si for Jiaozhou Bay. The lower Si ∶ N molar ratios (0.16±0.22) in dry deposition samples suggested that atmospheric dry deposition was likely to be one of the potential factors leading to Si-limitation for phytoplankton growth in Jiaozhou Bay for a long time. Further, according to the Redfield ratio (C ∶ Si=106 ∶ 16), the new productivity supported by SiO₃-Si input via dry deposition was calculated to be 674 mg C m^-2 a^-1, which accounted for 5.3% of the total new productivity of Jiaozhou Bay, suggesting the impacts from dry deposition of SiO₃-Si. This study systematically analyzed the dry deposition characteristics of aerosol SiO₃-Si, evaluated the importance of atmospheric SiO₃-Si dry deposition loading for the total exogenous input of SiO₃-Si in Jiaozhou Bay. The results are of great significance for understanding the biogeochemical cycling process of Si in the marginal seas.





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