Distribution, Flux And Release Rate Of Nitric Oxide In The Yellow Sea, Bohai Sea And Jiaozhou Bay

Nitric oxide （NO） is a small gaseous molecule and free radical, which receivesextensive attention. NO plays an important role in atmosphere, soil and organism, thegeneration and function mechanism of which has certain research. NO, as animportant intermediate in the marine nitrogen cycle, not only affects the organisms inseawater, but also affects the atmosphere, thereby affecting the climate andenvironment. The study of NO in marine has the important significance onunderstanding of marine ecosystems and the marine nitrogen cycle.In the study, we observed the distribution characteristics of the NO concentration,the changes of time and space, the release rate of the Yellow Sea, Bohai Sea and thetypical Gulf of Jiaozhou Bay and the relationship between NO and environmentalfactors （temperature, salinity, nutrients, light intensity, etc.） and the main ecologicalfactors of Chl-a, which is helpful for understanding of the influence factors of thedistribution of NO and the role in the biogeochemical cycling of nitrogen. The mainconclusions are as follows:（1）The spatial and temporal distribution and variation of NO in the Yellow Sea,Bohai Sea of China were researched in June2010. The average NO concentrationin the surface water of Yellow Sea and Bohai Sea was （163±38） pmol·L^-1insummer and the average concentration of NO was （155±44） pmol·L^-1in bottomseawater. The NO concentration was gradually reduced from the inshore to theoffshore. The NO concentration of Bohai Sea was higher than that of the YellowSea in general, which might be mainly due to China’s eastern coastal humanactivities impacting the ecological environment of the coastal waters. Diurnalvariation studies had shown that the maximum concentration of NO in a day wasat13:00, and then gradually reduced to reach the minimum value, at22:00, whichwas related to light intensity. The NO release rate of Yellow Sea and Bohai Sea during the day was about1.40×10^-11mol （L·s）^-1. The Yellow Sea and Bohaiwere the source of atmospheric NO in summer. We estimated the NO air-sea fluxin the Yellow Sea and Bohai was0.750×10^-15mol·(cm^-2·s^-1) in summer, the areaof TheYellow Sea and Bohai Sea was4.57×10¹¹m². The total nitrogen flux （N）was1.51×10³tN. There were complex relationships between NO concentrationand environmental parameters, correlations of which were not significant, whichmay be related to the complexity of the source, consumption and unstability ofNO.（2） The distribution, the temporal and spatial variation and the process of producingof NO were studied in the surface waters of Jiaozhou Bay, adjacent waters and thesurrounding rivers in March2010to November2011. The NO concentration ofthe surface seawater in Jiaozhou Bay showed obvious seasonal variations. Thehighest was in autumn and the lowest was in spring. The highest surfaceconcentration of NO was in September, with an average of （575.6±134.4）pmol/L. The NO concentration in surface waters in March was the lowest, whoseaverage was （2.6±4.4） pmol/L. In the horizontal distribution of the whole year,the concentration distribution of NO in surface seawater of the Bay showed thefollowing characteristis: the concentrations of NO in the bay were higher than thatin the mouth of the Jiaozhou bay, and the latter was higher than that outside thebay, showing a decreasing trend. There were significant seasonal variations aboutthe NO concentration distribution in surface water of the estuary. In April2011,The NO concentration in surface water ranged from92.4to312.7pmol/L in thesurrounding main rivers of the Jiaozhou Bay, an average of （149.2±22.7） pmol/Land in September the range was108.6³76.4pmol/L, an average of （267.3±45.2） pmol/L. The maximum of289.2pmol/L was in the Yanghe riverdownstream and the minimum of92.4pmol/L was in the upper reaches of theBaisha river. It was maybe because the rivers were impacted by the surroundingresidents and factory. The NO release rate in surface waters of the Jiaozhou Baywas （3.31±1.26）×10^-11mol/（L·s）^-1in daytime in the Autumn of2011, whichwas higher than the release rate of the Yellow Sea and Bohai Sea in Summer, which was maybe due to the higher content of nitrite. The NO formation rateinduced by light of Jiaozhou Bay in autumn was6.2nmol m^-2d^-1and NOphotoproduction of the Jiaozhou Bay was3.3×10³g of NO-N. The deckexperiment of addition of nutrients to seawater showed that the adding of nutrientsin seawater affected the process of NO. The NO concentration first increased, andthen decreased and the performance of the Chl-a content was just opposite.