南海大气沉降及其生态环境效应

Atmospheric deposition and its eco-environmental effects on the South China Sea

海–气界面的物质和能量交换是导致全球气候和生态环境变化的重要原因。作为我国和西北太平洋最大的陆架边缘海,南海的大气沉降在其外源输入中占有重要地位。随着南海周边国家经济社会的持续快速发展,人为源污染物通过大气沉降向海洋的输送日益增强,势必会对南海生态环境产生不可忽视的影响。基于近30年来南海生源要素、微痕量元素以及新污染物微塑料大气沉降的研究报道,本文系统总结归纳了南海大气干湿沉降物浓度、干湿沉降通量及其影响因素,并对其生态环境效应进行了分析。结果表明:(1)南海大气颗粒物浓度相较我国东部近海要低,且基本没有酸雨的沉降,但受东南亚生物质燃烧和我国化石燃料燃烧排放影响,南海大气碳质气溶胶浓度和沉降量处于较高水平;(2)南海大气干湿沉降营养盐中均以氮占绝对主导地位,且各形态氮的比例在不同海域存在较大差异,沉降物的营养盐结构严重失衡;(3)气溶胶中人为源金属元素的溶解度较高,多数成分以湿沉降为主,大气微塑料多以纤维形态存在,气象条件(降水量、风速等)、源排放强度是控制大气成分浓度和沉降通量的主要因素;(4)大气氮沉降约占南海表层氮输入总量的20%,大气氮的输入会加重海域的低氧和酸化,且营养物质沉降对浮游植物的爆发性增殖有重要作用,大气沉降会对南海这一寡营养生态系统产生多重复杂影响,这与海域水文条件、初始营养状况、浮游植物类群以及大气成分和沉降特征等密切相关。今后应注重在研究的深度和广度上持续发力,聚焦各类大气成分尤其是有机态氮磷和新污染物干湿沉降的精准化常态化监测,从多学科交叉角度深入探明生源要素和微痕量元素大气沉降与南海生态系统之间的影响与反馈机制。大气沉降是南海生物地球化学循环的重要一环,对南海生态环境的影响是一把“双刃剑”。随着未来南海陆源物质大气沉降作用的持续增强,这一影响必将更趋复杂和深远。

The material and energy exchange at the air-sea interface is an important cause of global climate and ecological environment change.As the largest shelf margin sea in China and the Northwest Pacific Ocean,atmospheric deposition plays an important role in the exogenous input of the South China Sea.With the continuous and rapid economic and social development of the surrounding countries in the South China Sea,the transport of anthropogenic pollutants to ocean through atmospheric deposition is increasingly enhanced,which is bound to have a non-negligible impact on the ecological environment of the South China Sea.Based on the research reports of atmospheric deposition of biogenic elements,micro-trace elements and new pollutants microplastics in the South China Sea in the past nearly 30 years,this paper systematically summarized the concentrations,fluxes and influencing factors of atmospheric dry and wet deposition in the South China Sea,and analyzed the eco-environmental effects of atmospheric deposition in the South China Sea.The results show that 1)The concentration of atmospheric particulates in the South China Sea is lower than that in the east coast of China,and there is almost no acid rain deposition.However,the atmospheric carbonaceous aerosol component concentration and deposition in the South China Sea are at a high level due to the influence of biomass burning in Southeast Asia and fossil fuel combustion emissions in China.2)Nitrogen is the dominant nutrient in the atmospheric dry and wet deposition in the South China Sea,and the proportion of nitrogen species varies greatly in different sea areas,resulting in strong imbalance of nutrient structure in atmospheric deposition.3)The solubility of anthropogenic metal elements in aerosols is high,and most of them in the form of wet deposition.Aerosol microplastics mostly exist in the form of fiber.Meteorological conditions(precipitation,wind speed,etc.)and source emission intensity are the main factors controlling atmospheric component concentration and deposition flux.4)Atmospheric nitrogen deposition accounts for about 20%of the total nitrogen input in the sea surface of South China Sea.The addition of nitrogen will aggravate the hypoxia and acidification of the offshore,and nutrient deposition plays an important role in the explosive proliferation of phytoplankton.Atmospheric deposition will have multiple and complex impacts on South China Sea,an oligotrophic ecosystem,which is closely related to hydrologic conditions,initial nutrient status,phytoplankton groups,atmospheric composition and deposition characteristics.In the future,it is suggested that the researchers should pay more attentions to the depth and breadth of the research,focus on the precise and regular monitoring of the dry and wet deposition of various atmospheric components,especially organic nitrogen and phosphorus species and new pollutants,and fully explore the influence and feedback mechanism between the atmospheric deposition of biogenic elements and micro-trace elements and the South China Sea ecosystem from the perspective of interdisciplinarity.Atmospheric deposition is an important part of biogeochemical cycle in the South China Sea,and its impact on the ecological environment is a"double-edged sword".With the continuous enhancement of atmospheric deposition of terrigenous species in the South China Sea in the future,this effect will become more complex and far-reaching.