贝类养殖对海洋环境中有机胺的影响

Mariculture in China often leads to eutrophication of coastal water, and dissolved organic nitrogen (DON) is one of the main N sources. Amines, a type of important constituents of DON in seawater, are strongly related to marine biological activities. Their release to the atmosphere can largely affect concentrations of atmospheric amines. Our previous study shows that the concentrations of atmospheric amines over marginal seas of China were 1-3 orders of magnitude larger than the concentrations reported in other marine atmospheres. We hypothesise that it may be related to the high-density and large-scale mariculture along the offshore. But as so far, the molecular composition and concentrations of amines in the mariculture environment are still unknown. High concentrations of Na+ in the seawater lead to amines to be accurately measured only using a few specific instruments. This project selects the shellfish culture in Qin huangdao as the study area by considering that the shellfish culture is the largest culture groups of China. The CRD-IC method is developed using a (Dionex) Carbonate Removal Device (CRD-200) combined with an ion chromatography(IC) in order to detect the concentrations of amines in seawater. The composition, concentrations, seasonal variations of amines and their contributions to the DON in the shellfish culture environment will be investigated in terms of the influences of the physical parameters, chemical parameters and the growth of the shellfish at different stages. In addition, the air-sea exchange flux of amines will be estimated in the mariculture environment. The project will improve understanding of nitrogen cycling in the mariculture environment.

海水养殖的自身污染加剧了近海水体富营养化，其中可溶性有机氮（DON）是主要污染物之一。有机胺作为DON的重要组成部分，与海洋生物活动密切相关，并影响大气中有机胺的浓度。我们的研究显示我国近海大气中有机胺浓度是世界其他海域的1-3个数量级。我们猜测这可能与我国近海大规模、高密度的海水养殖有关。但目前对海水养殖环境中有机胺的组成及浓度尚不明确。同时高浓度Na+使海水中有机胺只能用特定仪器准确检测。鉴于贝类养殖是我国第一大养殖类群，本项目选取秦皇岛贝类养殖区为研究区域，通过建立（戴安）碳酸根去除装置与离子色谱（CRD-IC）相结合的新方法来检测海水中有机胺浓度，认识贝类养殖环境中有机胺的组成、浓度变化特征及对DON的贡献。揭示海洋环境中理化参数、贝类生长的不同阶段对有机胺的影响。通过计算有机胺的海气交换通量，揭示贝类养殖对近海大气中有机胺的影响。本项目将为认识海水养殖环境中氮循环提供理论依据。

海洋是大气中有机胺的重要来源，但海洋环境中有机胺的形成机制尚不明确。本项目分析了近岸及近海海域动物及大型藻类体内有机胺前体物的浓度特征，及降解这些前体物的优势细菌；探索了近海大气中气态及颗粒态有机胺的浓度特征、转化机制及影响因素。主要研究结果如下：.（1）通过对海洋鱼、虾、贝类、浒苔等大型藻类体内有机胺前体物分析，发现生物体内含有大量的氧化三甲胺（TMAO）和甜菜碱（GBT）等有机胺前体物。鱼类主要以TMAO为主，浒苔等大型藻类、贝、虾类主要以GBT为主，猜测虾、贝类体内GBT有可能从浮游植物等微藻食物中获取，待后续研究继续验证；.（2）通过对秦皇岛养殖区和浒苔爆发区海水中细菌鉴定发现，HIMB11（玫瑰杆菌的一种）可能是把TMAO和GBT降解为TMA和DMA 的主要优势细菌；.（3）发现黄渤海域海水表层盐度或叶绿素浓度与大气颗粒物中DMA+或TMA+呈正相关关系；.（4）2018年4 -5月通过采用在线离子色谱（AIM-IC）对黄海-东海-南海大气中有机胺观测，发现当氨气（NH3）<0.６µg m-3，气态DMA可以竞争过NH3形成颗粒态DMA+；但是在强SO2烟羽中，DMA由气态转换成颗粒物，且不受NH3控制，且低温高湿度促进以上过程的发生；发现大气颗粒物中TMA+与NH4+存在显著负相关关系，推测TMA+通过液液萃取被NH4+替代，释放出TMA； .（5）2019年12月通过采用AIM-IC对黄渤海大气中有机胺观测，发现气态TMA浓度是世界其他海域的1-17倍，颗粒态DMA+、TMA+的浓度是世界其他海域的1-3个数量级。温度与气态DMA、TMA呈极显著正相关关系，该航次风速较高（最高达12 m s-1）。推测海水中可能有大量的有机胺，此外，温度、风速升高会显著促进海气交换，导致大气中气态和颗粒态有机胺浓度的增加。以上成果为进一步认识海洋环境中有机胺的形成机制提供理论依据。