课6溶解气体海洋化学省公开课一等奖全国示范课微课金奖PPT课件.pptx

,Click to edit Master title style,Click to edit Master text styles,Second Level,Third Level,Fourth Level,Fifth Level,*,*,*,第五章 海水中气体,海水中除含有大量无机物和有机物以外，还溶解一些气体，如,O,2,，,CO,2,，,N,2,等。研究这些溶解气体起源和分布对了解海洋中各种物理和化学过程起着主要作用。,第1页,氧是海洋学中研究得最早、最广泛一个气体，它在深海中分布与海水运动相关，经过氧分布特征能够了解海水物理过程，如水团划分和年纪以及运动速度等。,海水中溶解氧含量与海洋生物活动相关，海洋植物光合作用放出氧气，呼吸作用消耗氧气。,“保守气体”或非活性气体：不参加海水化学和生物反应，如氮、氢和其它惰性气体。有利于深入了解空,海界面物理过程，以及深入了解氦经由海底放射核素输入过程。,微量气体，如甲烷和一氧化碳等，气体全球性循环过程。,放射性气体，如,3,H,222,Rn,3,He,，可用来研究海,空界面气体交换，同时也是海水运动中有用气体指示剂。,第2页,海水中所溶解气体主要来自大气、海底火山活动、海水中发生化学反应和其它过程（比如生物过程尤其是光合作用和呼吸作用、有机物分解和放射性蜕变，以及地球化学过程等）。,水循环、风化作用、光合作用、生物腐败分解、波浪和海流等很多海洋学和海洋化学过程都与大气相关。,大气与海洋相比有相同之处，比如二者都是流体，它们大多数成份逗留时间比地球寿命短等。,第3页,Dissolved Gases Other than CO,2,Composition of the Atmosphere,Dissolution of Gases in Seawater,Air-Sea Exchange,Nonreactive Gases in Seawater,Oxygen in the Oceans,Other Nonconservative Gases,Chemical,Oceanography,第4页,Sources of Gases to the Oceans,1.,Atmosphere,(N,2,O,2,),2.,Volcanic Activity,(H,2,S),3.,Chemical Processes,Biological Activity,(NO,3,N,2,O),Radioactive Decay,(,226,Ra,222,Rn),Chemical,Oceanography,第5页,Composition of the Atmosphere,N,2,0.7808,O,2,0.2095,Ar0.00934,CO,2,0.00033,Ne1.8 x 10,-5,He5.2 x 10,-6,Kr1.1 x 10,-6,Xe8.7 x 10,-8,Pollutants(O,3,SO,2,NO,2,CH,4,CO),Chemical,Oceanography,GasMole Fraction,第6页,大气中温室气体,第7页,Measurement Methods,1.Equilibrating or stripping with an inert gas and measure by G.C.,M.S.,or I.R.(N,2,CH,4,CO,2,Ar,etc.).,2.Direct measurement in solution(O,2,by Winkler Method).,Mn,2+,+2 OH,-,Mn(OH),2,Mn(OH),2,+O,2,MnO(OH),2,MnO(OH),2,+4H,+,+3I,-,Mn,2+,+I,3,-,+3H,2,O,I,3,-,+2S,2,O,3,2-,2 I-+S,4,O,6,2-,Chemical,Oceanography,第8页,Basic Concepts,Daltons Law,P,T,=P,N2,+P,O2,+P,Ar,+P,H2O,Ideal Gas Law,P,G,=n,G,RT/V,G,R=82.05,cm,3,atm mol,-1,deg,-1,Henrys Law,P,G,=K,G,GG =P,G,/K,G,P,G,(soln)=P,G,(air),Chemical,Oceanography,第9页,第10页,Solubility of Gases in Seawater,G=k P,G,=(1/K,G,)P,G,P,G,(atm)=P,G,(solution),ln G=a,0,+a,1,S,ln G=b,0,+b,1,/T+b,2,ln T,ln G=A,1,+A,2,(100/T)+A,3,ln(T/100)+SB,1,+B,2,(T/100)+B,3,(T/100)2,Chemical,Oceanography,第11页,Effect of Salinity on Solubility,GasWater Seawater,He2.2 nM 1.8 nM,Ne10 7.9,Kr5.8 4.0,Xe0.9 0.2,N,2,823,M616,M,O,2,456349,Ar 22 17,CO,2,23 20,Chemical,Oceanography,第12页,Effect of Temperature on Solubility,Gas0,o,C 25,o,C,He1.8 nM1.7 nM,Ne7.96.6,Kr4.02.3,Xe0.60.4,N,2,616,M383,M,O,2,349206,Ar1710,CO,2,20 9,Chemical,Oceanography,第13页,Effect of Temperature,Chemical,Oceanography,第14页,第15页,第16页,Causes of Deviations from Expected Solubility,1.Departures from Standard Atmosphere,2.Dissolution of Air Bubbles,3.Air Injection,4.Differential(,微分，微分,)Heat and Gas Exchange,5.Mixing of Waters of Different Temperatures,6.Radiogenic,（放射性，无线电广播）,or Primordial,（原始）,Addition,Chemical,Oceanography,第17页,Role of Bubbles,Chemical,Oceanography,第18页,Effect of Mixing Water of Different Temperature,Chemical,Oceanography,第19页,Gas Saturation Anomalies,Chemical,Oceanography,第20页,Helium in Deep Waters,Chemical,Oceanography,第21页,He from Hydrothermal Vents,Chemical,Oceanography,第22页,Helium in Deep Waters,Chemical,Oceanography,第23页,Flux,（流量，通量）,of Gas Across the Air-Sea Interface,Chemical,Oceanography,第24页,Double Layer Gas Flux Model,Chemical,Oceanography,第25页,Flux of Gas Across the Air-Sea Interface,Flux=dC/dt=D(dC/dz),Flux=(D/K,)P,G,(air)-P,G,(soln),Flux=k P,G,(air)-P,G,(soln)=k,P,G,k is exit coefficient,is boundary layer thickness,K is Henrys Law constant,D is diffusion coefficient,Chemical,Oceanography,第26页,影响气体交换原因,温度,气体溶解度,风速,季节等,第27页,温度影响,大气与海洋间气体交换主要决定于气体在两相中分压差。当海水温度升高或降低都会使水体中气体分压发生改变，因而引发气体在两相间交换。,Downing,等人,(1955),发觉：,CO2,交换速率随温度升高而直线增加，,25,海水交换速率大约是,5,两倍。,第28页,气体溶解度影响,不一样气体在海水中溶解度各不相同。所以，对于某一恒定分压差，各种气体进人海洋扩散通量相差悬殊，比如,O,2,CO,2,和,N,2,通量比率是,2,：,70,：,1,。,第29页,风速影响,Downing,等人,(1955),研究了空气和水之间交换速率。他们指出：风速在,0-3ms,-1,时，交换速率几乎保持恒定（在液体表面上方,5 cm,处测量）。而风速在,3-13,米秒时，交换速率快速增加。,第30页,季节影响,进入或逸出海洋表层气体体积随季节性改变是相当大。,Redfield(1948),曾预计，在秋季和冬季平均约有,3010,4,cm,3,O,2,进入美国缅因湾海洋表层，在春季和夏季却以对应体积从海洋表面逸出。其中大约,2/5,是光合作用产生氧，其余是因为在温暖水中氧溶解度降低而逸出。,第31页,Diffusion Coefficients(10,5,cm,2,s,-1,),GasMW0,o,C24,o,C,He42.04.0,Ne201.42.8,N,2,281.12.1,O,2,321.22.3,Ar400.81.5,CO,2,441.01.9,N,2,O441.02.0,Kr840.71.4,Xe1310.71.4,Rn2220.71.4,Chemical,Oceanography,第32页,Boundry Layer Thickness,Chemical,Oceanography,第33页,Exit Coefficient as Function of Wind Speed,Chemical,Oceanography,第34页,第35页,nitrogen,:most common dissolved gas in seawater(accounts for 50%of the dissolved gas in water),major source is diffusion from the atmosphere,is extremely important for protein and amino acid,（氨基酸）,production by organisms,but is only available when fixed(oxidized)into a form like ammonia,（氨基，氨水）,-then it can be converted into nitrate,（硝酸盐,硝酸钾）,The principal gases dissolved in seawater are oxygen and nitrogen.,Nitrogen is conservative(like the 11 major elements;concentration changes by mixing only),第36页,Oxygen in the Oceans,Chemical,Oceanography,第37页,Oxygen in Surface Waters,Chemical,Oceanography,第38页,Effect of Photosynthesis on O,2,Chemical,Oceanography,第39页,第40页,Effect of Upwelling on O,2,Chemical,Oceanography,第41页,Oxygen in Atlantic Ocean Waters,Chemical,Oceanography,第42页,Oxygen Distribution-Atlantic,第43页,Oxygen in Pacific Ocean Waters,Chemical,Oceanography,第44页,Oxygen in Indian Ocean Waters,Chemical,Oceanography,第45页,Apparent Oxygen Utilization,Chemical,Oceanography,AOU=O,2,Calc -O,2,Meas,AOU 0 O,2,is being used,AOU 0 O,2,is being produced,第46页,AOU in Deep Ocean Waters,Chemical,Oceanography,第47页,AOU in Pacific Waters,Chemical,Oceanography,第48页,Modeling O,2,Profiles,Chemical,Oceanography,第49页,Oxygen Utilization Rates,Chemical,Oceanography,第50页,oxygen,:,major source,of dissolved oxygen,is the photosynthetic activity,of plants living in the surface layer of the ocean,seawater can hold only a small fraction of the oxygen that is produced,so,excess oxygen is diffused into the atmosphere,(ocean provides 50%of the atmospheres oxygen content),the,amount of dissolved oxygen can be increased by turbulence,(water movement)caused by waves and surface winds,dissolved oxygen declines rapidly as depth increases,because the rate of photosynthesis is slowed by decreasing light intensity,thermoclines can also decrease the level of oxygen,due to the high level of bacterial respiration at this depth,but below the thermocline,the amount of dissolved oxygen may increase again since oxygen solubility is increased by colder waters and there are fewer organisms living in deep waters(and most have lower metabolic rates),第51页,Carbon Monoxide Saturation,Chemical,Oceanography,第52页,Hydrogen in the Oceans,Chemical,Oceanography,第53页,Methane in the Oceans,Chemical,Oceanography,第54页,Methane in Coastal Waters,Chemical,Oceanography,第55页,N,2,O and O,2,in Arabian Sea,Chemical,Oceanography,第56页,Carbon Monoxide,Chemical,Oceanography,第57页,carbon dioxide,:can enter seawater in two ways:,from the atmosphere(oceans contain 60 times more carbon dioxide than the atmosphere because it is extremely soluble in seawater),from the breakdown of organic materials(is a common constituent of shells and sediments),is present as dissolved carbon dioxide,bicarbonate,（重碳酸盐）,and carbonate,（碳酸盐）,dissolved CO,2,reacts with water form carbonic acid(H,2,CO,3,)which then dissociates to form bicarbonate and carbonate-this dissociation forms a buffering system which maintains seawaters pH at about 8.00.5;CO,2,can also react with carbonate to for bicarbonate,CO,2,concentrations increase with depth because it is used during photosynthesis and released during respiration and because its solubility in water increases with pressure,the concentration of carbon dioxide in seawater is relatively constant;this provides seawaters buffering,（,减震,阻尼,隔离,）,capacity,第58页,