Variation Characteristics And Controlling Factors Of Carbon Source And Sink In Changjiang Estuary And Its Adjacent Sea Area

The ocean,as the world's largest carbon pool,absorbs 30% of the total anthropogenic CO₂ emissions each year,which has a crucial impact on controlling the continued rise in global atmospheric CO₂.While the continental margin of the shelf is only 7% of the global ocean area,but each year can absorb 200 to 500 million tons of carbon,accounting for 10% to 30% of the global net carbon sink net flux,is an important part of the study of marine carbon cycle.With the rapid rise of coastal cities,under the disturbance and impact of human activities,the biogeochemical processes in coastal waters are undergoing unpredictable changes and need to be re-investigated and evaluated.Therefore,this paper studies the temporal and spatial changes of carbon sinks in the Yangtze River estuary and adjacent waters,and further discusses the key process of controlling the exchange of CO₂ fluxes between sea and air,and obtains a series of new cognitive and Results.From the survey data of March 2016,the Yangtze River estuary and the adjacent sea area in the late winter as a whole showed CO₂ carbon sinks,the sea-air CO₂ exchange flux of-4.43 ± 7.41 mmol / m2 / d.The winter survey area is mainly affected by the three water masses in the Yangtze River,the warm current of the Yangtze River and the Yellow Sea,which is the main reason for the obvious regional differences in the sea and sea CO₂ fluxes in the Yangtze River estuary.?29.26 mmol / m2 / d?in the runoff area of the Yangtze River,and the dilute water area in the Yangtze River is almost balanced with the atmosphere?-1.10 ± 3.11 mmol / m2 / d?,the Huangdonghai mixed water area and the Taiwan warm zone?-7.54 ± 6.73 mmol / m2 / d?,?-12.11 ± 9.96 mmol / m2 / d?,respectively.At the end of winter,the effect of biological activity on sea surface pCO₂ was negligible.Under the condition of obvious change of vertical structure of water in coastal waters,the distribution of sea surface pCO₂ was only controlled by the horizontal mixing between water masses and vertical mixing The effect of sea surface pCO₂ is weak.Therefore,based on the analysis of the control factors of the end of the winter of 2016,the inversion of the sea surface pCO₂ is established.Based on the inversion results of the sea surface salinity?SSS?The interannual variation of the differential pressure is related to the runoff of the Yangtze River,but there are still other biological earth processes.From the survey data of July 2016,the Yangtze River estuary and adjacent waters in the summer are the main source of atmospheric CO₂,and the sea CO₂ exchange flux is 16.69 ± 37.18 mmol / m2 / d.Due to the positive flood period,the entire survey area is almost occupied by the Yangtze River dilution water.However,different regions of the Yangtze River estuary and adjacent waters in summer still show significant differences in carbon source sinks.?30 ° 32 ° N,122 ° 123 ° E?,which is mainly composed of fresh water input,suspended matter decomposition and biological respiration,has a strong source of atmospheric CO₂,The sea gas CO₂ flux is 37.27 ± 36.55 mmol / m2 / d,and the sea surface pCO₂ partial pressure range is 269 1605?atm.?30 ° 32 ° N,123 ° 124 ° E?,and its biogeochemical behavior is very different from that of the former.With the increase of water transmittance,The photosynthesis of phytoplankton was stronger under the condition of high temperature and high nutrient level.Therefore,the whole sea CO₂ was-12.11 ± 4.99 mmol / m2 / d,pCO₂ partial pressure range of 240 507?atm.In addition,the effect of upwelling mechanism on the sea surface pCO₂ is different from that of Zhejiang and Fujian.The submarine sea area upstream of the Yangtze River estuary may be higher than the core area under the influence of the turbidity of the water.From the overall survey results,in the range of 2 ° to the sea,the sea surface pCO₂ there is a great fluctuation?240 1605?atm?,which also fully reflects the shelf edge of the sea than the open ocean much more complex biological earth Chemical process.Based on the historical data of the Yangtze River estuary in August 2003,January 2006,July 2007 and March 2008,the temporal and spatial changes of carbon source sinks in the Yangtze River estuary and its adjacent waters were analyzed and discussed.From the results,the distribution trend of carbon source and sink in the Yangtze River estuary and its adjacent waters is consistent,but its source and sink intensity has obvious change.In the winter,the northern part of the Yangtze River estuary and the East China Sea continental shelf area showed a trend of carbon sequestration,which could be about 5.99 and 20.87 thousand tons of carbon per year respectively.The effect of carbon eutrophication on the coastal waters of the Yangtze River Carbon sinks have weakened,the annual absorption of 2.64 kilotons of carbon will be reduced;but overall,the Yangtze River estuary in winter appears to enhance the carbon absorption capacity,which affected by the Taiwan warm current East China Sea continental shelf area is the main contributor.In the summer,due to the interference of human activities such as the Three Gorges Dam,the Yangtze River runoff showed an increasing trend,and the carbon source / sink intensity of the coastal waters and offshore waters of the Yangtze River estuary were significantly improved.The coastal waters were released more than 84.63 And the offshore sea area will be more fixed 11.2 thousand tons of carbon per year.Although the absorptive capacity of offshore waters is greatly enhanced by the effect of eutrophication,the sea area of the Yangtze River estuary west of 124 ° is still showing CO₂ release Ability to enhance the trend.