Research progress of atmospheric aerosol iron over the Southern Ocean and the Antarctic
Iron(Fe)is an important marine micronutrient,which is considered as one of the key factors affect-ing the growth of marine phytoplankton and carbon output.The Southern Ocean accounts for 20％of the global ocean area,is the world's largest"high nutrient,low chlorophyll"sea area,playing an irreplaceable role in global biogeochemical processes.Due to perennial iron deficiency,macronutrients(such as nitrogen,phospho-rus,and silica)in the Southern Ocean are high but primary productivity is relatively low.Therefore,new bioac-tive iron sources can alleviate the limitation of iron deficiency in the Southern Ocean,thus improving marine pro-ductivity,promoting the absorption of atmospheric CO2 and indirectly affecting global climate change.On the basis of summarizing the research progress on aerosol iron over the Southern Ocean and the Antarctic in recent years,this article focuses on the following parts:(1)Discuss the chemical forms,the concentration distribution of atmospheric aerosol iron,fractional iron solubility and the factors affecting solubility.Total iron can be divid-ed into bioactive iron and insoluble iron,and bioactive iron includes two forms:soluble iron and unstable iron.During field observations,the concentration of atmospheric aerosol iron ranged from 0.1 to 150 ng·m-3.The mass concentration of total iron has obvious seasonal variations,with the peak in austral summer(mainly in Jan-uary and February),and the lowest in austral winter.The main oxidation states of iron include the Fe(Ⅱ)and Fe(Ⅲ),which have significant concentration differences and are affected by seasonal variation.The fractional iron solubility ranges from 0.01％to 90％,which is affected by the atmospheric aging process(includes acid dis-solution,organic complexation,photo-reductive dissolution and cloud processing)and the characteristics of aerosol iron(such as particle size,specific surface area)and air mass sources.(2)Summarize sources of iron in aerosols,including mineral dust sources,anthropogenic emissions(biomass burning and fossil fuel burning),and local sources in the Antarctic.Among them,mineral dust sources are the main source of iron in the atmo-sphere,providing natural iron nutrients for the Southern Ocean,and contributing up to(33±15)％to the annual net production of phytoplankton communities in the Southern Ocean.Compared with mineral dust iron,anthro-pogenic aerosol iron is the more important source for dissolved iron,due to its high solubility and is thought to be more bioavailable.With the intensification of human activities and the development of industry,the contribu-tion of anthropogenic emissions of atmospheric dissolved iron in the Southern Ocean is becoming increasingly important.With the accelerated melting of sea ice leading to the expansion of the open sea ice-free area,the dust iron source from the Antarctic continent needs more attention.(3)Explore the deposition flux of atmospheric aerosol iron and evaluate the response of the Southern Ocean to the atmospheric deposition process.The atmo-spheric deposition process includes dry and wet deposition and the range of the total iron deposition flux is 1.3 1x 10-6～297.33×10-6 g·m-2·a-1.The feedback of the Southern Ocean to atmospheric deposition of aerosol iron is quite sensitive,experiments such as"iron fertilization"confirmed that the change of soluble iron significantly af-fected the growth of marine phytoplankton,and then affected the annual net production of phytoplankton com-munities.The significant increase of soluble iron in aerosols caused by the Australian wildfires and stimulated phytoplankton rapid growth in the ocean,resulting in the algal bloom phenomenon.In addition,this paper also puts forward some suggestions based on the current research status of aerosol iron over the Southern Ocean and the Antarctic,in order to provide a basic reference for further research on atmospheric aerosol iron over the Southern Ocean and the Antarctic in the future.
万方数据
维普
