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1.
在巢湖西北半湖近岸带设置大型围隔研究秋季连续打捞蓝藻对湖泊温室气体通量的影响,应用YL-1000型大型仿生式水面蓝藻清除设备进行原位打捞蓝藻,通过便携式温室气体分析仪-静态箱法对大型围隔内水-气界面CH4、CO2通量特征及其影响因素进行观测.结果表明：对比未打捞区,蓝藻连续打捞下打捞区水体中叶绿素a（Chl.a）、悬浮物（SS）浓度不断下降,两者削减率分别为72%、85%,Chl.a、SS浓度分别下降到29.6±2.5 μg/L、12.5±1.2 mg/L,打捞对围隔内颗粒态物质去除效果十分明显;打捞过程中水体溶解性有机物（DOM）中微生物代谢类腐殖质（C1）、类蛋白（C3）显著下降趋势,打捞区C1、C3组分（0.18±0.02、0.06±0.01 RU）强度明显低于未打捞区（0.26±0.05、0.12±0.03 RU）,打捞能有效控制藻源性溶解性有机质释放.同时,打捞区水-气界面CH4通量呈显著下降趋势,未打捞区CH4通量平均值（17.473±1.514 nmol/（m2·s））为打捞区（7.004±4.163 nmol/（m2·s））近2倍,CH4通量与Chl.a、C1、C3组分均呈显著正相关,水体中藻源性溶解态有机质对CH4通量具有促进作用;打捞区CO2释放通量呈显著上升趋势,打捞区CO2吸收通量（-0.200±0.069 μmol/（m2·s））明显低于未打捞区（-0.344±0.017 μmol/（m2·s））,CO2通量与Chl.a、温度均呈显著负相关.秋季打捞对CH4、CO2综合日平均通量减排量值为0.275±0.076 mol/（m2·d）（以CO2当量计）.研究结果揭示了巢湖秋季连续打捞蓝藻过程对水-气界面温室气体具有显著减排作用,且能在一定程度上减缓蓝藻水华与湖泊富营养化、气候变暖之间的恶性循环,为湖泊碳循环和蓝藻水华灾害防控提供科学数据支撑和理论参考.  相似文献   

2.
内陆水域二氧化碳(CO2)排放是全球碳平衡的重要组成部分,全球CO2排放通量估算通常有很大不确定性,一方面源于CO2排放数据观测的时空离散性,另一方面也是缺少水文情景与CO2排放通量关联性的研究.本文观测了2018年洪泽湖不同水文情景表层水体CO2排放通量特征,并探讨其影响因素.结果表明,洪泽湖CO2排放通量为丰水期((106.9±73.4) mmol/(m2·d))>枯水期((18.7±13.6) mmol/(m2·d))>平水期((5.2±15.5) mmol/(m2·d)),且碳通量由丰(310.2~32.0 mmol/(m2·d))、枯(50.8~2.2 mmol/(m2·d))、平(-17.3~39.8 mmol/(m2·d))3种水文情景的交替表现出湖泊碳源到弱碳汇的转变,空间上CO2排放通量总体呈现北部成子湖区低、南部过水湖区高的分布趋势.洪泽湖CO2排放对水文情景响应敏感,特别是上游淮河流域来水量的改变,是主导该湖CO2排放时空分异的重要因子.丰水期湖泊接纳了淮河更多有机和无机碳的输入,外源碳基质的降解和矿化显著促进了水体CO2的生产与排放,同时氮、磷等营养物质的大量输入,加剧了水体营养化程度,进一步提高CO2排放量,间接反映出人类活动对洪泽湖CO2变化的深刻影响.平、枯水期随着上游淮河来水量的减少,驱动水体CO2排放的因素逐渐由外源输入转变为水体有机质的呼吸降解.此外,上游河口区DOM中陆源类腐殖质的累积与矿化能够促进CO2的排放,而内源有机质组分似乎并没有直接参与CO2的排放过程.研究结果揭示了水文情景交替对湖库CO2排放的重要影响,同时有必要进行高频观测以进一步明晰湖泊的碳通量变化及其控制因素.  相似文献   

3.
人为干扰和气候变化会改变湖泊水位状态,明确不同水位条件下湖泊沉积物有机碳矿化特征及其影响因素,对了解内陆水生态系统碳循环具有重要意义.为探究干旱区典型盐湖沉积物有机碳矿化速率对水位变化的响应,以巴里坤湖干涸湖底原状沉积物为研究对象,初步探究了0（T1）、-9（T2）、-23（T3）、-34（T4）和-45 cm（T5）水位处理对沉积物有机碳矿化速率的影响.结果表明,T1、T2和T3处理有机碳矿化速率在试验初期较高（0~10 d）,10 d后缓慢下降,T4和T5处理有机碳矿化速率呈先增加后降低趋势;T1（1.718 μmol/（m2·s））与T3（1.784 μmol/（m2·s））处理有机碳矿化速率不存在显著差异,T1处理有机碳矿化速率是T2、T4和T5处理的1.09、3.31和3.57倍,不同处理有机碳累积矿化量表现为T3 > T1 > T2 > T4 > T5.有机碳累积矿化量（Ct）占沉积物有机碳（C0）的比例（Ct/C0）介于0.012~0.044之间,沉积物有机碳潜在排放量（Ci）占C0的比例（Ci/C0）介于0.018~0.045之间;水位降低,沉积物有机碳矿化常数（k值）减小,T1处理k值最大（0.137 d）,T4处理最小（0.032 d）.线性方程Cr=0.008x+0.488能较好地模拟有机碳矿化速率（Cr）与水位（x）的关系;不同水位处理有机碳矿化速率与模拟柱中沉积物5 cm温度呈显著的指数函数关系,T4、T5处理有机碳矿化温度敏感系数（Q10）显著高于T1、T2和T3处理,即水位降低增加了巴里坤湖干涸湖底沉积物Q10.因此,就巴里坤湖干涸湖底沉积物而言,水位从0 cm降至-45 cm时有机碳矿化速率降低,Q10增加;反之水位上升则会促进有机碳矿化分解,Q10降低.水位持续下降抑制有机碳矿化可能是维持干旱区盐湖沉积物碳库稳定的机制之一.  相似文献   

4.
湖库淡水水域对温室气体排放的贡献不容小觑,然而观测时间的代表性不足以及缺乏对降雨因素的考虑制约了碳排放的准确估计.本研究以湖北宜昌境内官庄水库为例,选取强降雨多发的夏季时段,针对水气界面温室气体通量、水体表层和垂向剖面气体溶存浓度及环境因子开展了为期1周的原位高频观测,以探讨夏季降雨事件对水库温室气体通量变化的影响.结果表明,观测期内官庄水库水气界面CH4通量变化范围为0.007~0.077 mg/（m2·h）,CO2通量范围为5.48~57.57 mg/（m2·h）,白天和夜晚均表现为大气的碳源.小雨、中雨乃至暴雨天气条件下,CH4和CO2日均通量均较低,日通量倾向于受风速和温度调控.CH4和CO2通量变化趋势较为一致,观测期内日间排放量高于夜间排放量出现的次数更多,昼夜差异对降雨天气状况无明显响应,风速是CH4和CO2通量昼夜变化的主导因素.暴雨过程中,CH4-k600和CO2-k600与水气温差存在显著正相关,但水体垂向混合过程十分短暂.在平均雨强为3.8 mm/h的暴雨第I阶段,CH4-k600对风速和降雨的响应明显,而在雨强更大（8.5 mm/h）的第II阶段,CH4-k600与风速、降雨均未表现出相关性,通量箱在强降雨条件下的适用性可能存在雨强阈值.  相似文献   

5.
韩翠红  孙海龙  魏榆  鲍乾  晏浩 《湖泊科学》2020,32(6):1683-1694
耦联水生光合作用的碳酸盐风化碳汇是全球碳循环的重要组成部分,而生物碳泵效应是稳定碳酸盐风化碳汇的关键机制.河流筑坝后,生物碳泵效应的变化、控制因素及对水化学影响的研究甚少.本研究对2个喀斯特筑坝河流平寨水库和红枫湖进行系统采样,以研究河流筑坝后生物碳泵效应的变化、控制因素及对水化学的影响.研究结果表明,入库河流的水化学变化不明显,而2个水库的水化学则表现出显著的季节变化特征,具体表现为水库的水温和pH均呈现出夏季高、冬季低的变化特征,而电导率（EC）、HCO3-浓度和pCO2则表现出夏季低、冬季高的季节变化特征.以叶绿素a（Chl.a）浓度和溶解氧（DO）饱和度指代的生物碳泵效应则是在夏季最强、冬季最弱.生物碳泵效应利用溶解性无机碳（DIC）,形成有机质并释放出氧气,是造成夏季水库pH值和DO饱和度升高,电导率（EC）、HCO3-浓度和pCO2降低的主要因素.空间上,水库的Chl.a浓度及DO饱和度均大于河水,EC、HCO3-浓度和pCO2均小于河水,这表明河流筑坝后,由于水库的“湖泊化”导致水库的生物碳泵效应显著提高.通过对Chl.a与碳、氮和磷浓度及化学计量比的相关性分析发现,平寨水库和红枫湖的生物碳泵效应受到碳施肥的影响.平寨水库和红枫湖水库生物碳泵效应碳施肥机制的发现,表明在喀斯特地区,生物碳泵效应不仅受到氮磷元素的控制,也受到碳元素的控制,因此在富营养化湖泊治理时,也应考虑碳的影响.  相似文献   

6.
湖泊、河流等内陆水体是连接陆地生态系统和海洋的“长程碳环路”的重要节点,也是温室气体二氧化碳(CO2)排放源,在调节陆地、海洋间的碳迁移转换中发挥着重要作用。相对于自然水体,城市水体因面积小、水深浅且受监测方法限制,水-气界面碳通量经常被忽略。为探讨我国亚热带城市水体温室气体排放特征,本研究以湖南省长沙市典型城市水体,包括洋湖、西湖、松雅湖、月湖4个湖泊和湘江长沙段为研究对象,分别于2022年4和10月采用光化学反馈-腔增强吸收光谱法(OF-CEAS)和扩散模型法对水-气界面CO2通量进行对比测定。结果表明,长沙城市湖泊与河流春季为CO2排放源,秋季为吸收汇,河流水-气界面CO2通量呈显著季节差异。河湖之间CO2通量在春季表现为显著差异,秋季差异不显著。CO2通量与水体溶解氧、水体总氮浓度等呈显著正相关。2种方法的CO2通量对比测定在湖泊上显著相关,但对河流而言相关性不显著。研究揭示的城市湖泊与河流CO2气体的排放特征有利于深入探究城市水体碳的迁移转化,可对全面了解全球气候变化过程和河湖湿地温室气体减排和调控提供科学支撑。  相似文献   

7.
河流作为连接陆地和海洋碳库之间的通道,是全球内陆水体碳排放最主要的载体,在全球碳循环中发挥着至关重要的作用。全球河流水-气界面二氧化碳（CO2）脱气显著的时间异质性特征研究有助于深入理解其碳循环过程与机制,也为准确评估碳通量以及完善碳循环模型提供了科学支撑。本文系统梳理了国内外的相关研究成果,总结了目前河流CO2脱气通量在昼夜、季节以及多年尺度上的动态变化及其影响因素,指出其昼夜变化与季节变化存在一定的周期性,并对不同空间尺度上CO2脱气通量的时间差异进行讨论。同时分析当前研究中的不足,认为缺乏河流二氧化碳分压（pCO2）与CO2脱气系数（k）高分辨率且长期连续的直接测量,限制了河流CO2脱气通量时间尺度变化的周期性及相互之间关系的厘定,使得气候变化与人类活动对河流CO2脱气时间动态的影响仍然难以量化与预测。最后,根据目前存在的问题,展望了未来的研究重点,为全球河流水-气界面碳循环过程与机制、模型研究提供新的思路与方向,以及可以更准确地评估和预测未来河流碳排放的变化趋势。  相似文献   

8.
模型估算法是水-气界面甲烷（CH4）通量监测的主要方法.本研究选择6种不同的参数化模型方法估算了2015年6、8和10月两个亚热带河口养殖塘水-气界面CH4传输速率（kx）及其扩散通量,探讨了河口养殖塘kx及CH4扩散通量的变化特征和影响因子.结果表明：研究期间,不同模型估算下的kx及其扩散通量均值在闽江河口养殖塘变化范围分别为1.60±0.75~6.29±1.30 cm/h和9.19±2.67~30.64±6.28 μmol/（m2·h）,在九龙江河口养殖塘的变化范围分别为0.89±0.19~6.07±0.61 cm/h和3.18±0.48~21.03±2.13 μmol/（m2·h）;kx及其扩散通量在两个河口区均呈现随时间推移而升高的特征;整个养殖期间,养殖塘水-气界面平均CH4传输速率kx呈现闽江河口略高于九龙江河口（P>0.05）,但水-气界面平均CH4扩散通量呈现闽江河口显著高于九龙江河口的特征（P<0.05）;风速、水体溶解CH4浓度和盐度是调控河口区养殖塘水-气界面CH4扩散通量变化的重要因子;不同模型估算出的河口养殖塘水-气界面CH4传输速率kx存在差异,表明模型估算法获得的水-气界面CH4扩散通量存在一定的不确定性.  相似文献   

9.
邓焕广  张智博  刘涛  殷山红  董杰  张菊  姚昕 《湖泊科学》2019,31(4):1055-1063
为了解城市湖泊不同水生植被区水体温室气体的溶存浓度及其影响因素,于2015年4-11月按每月2次的频率采用顶空平衡法对聊城市铃铛湖典型植被区——菹草区、莲藕区和睡莲区表层水中CO2、CH4和N2O的溶存浓度进行监测,计算水中温室气体的饱和度和排放通量,并测定水温（T）、pH、溶解氧（DO）、叶绿素a及营养盐浓度等理化指标,以探究水体环境因子对温室气体溶存浓度的影响.结果表明,铃铛湖各植被区水体温室气体均处于过饱和状态,是大气温室气体的"源";莲藕区CH4浓度、饱和度和排放通量均显著高于菹草区,而各植被区N2O和CO2均无显著性差异;不同植被区湖水中DO、总氮（TN）、总磷（TP）和硝态氮（NO3--N）浓度具有显著差异,其中DO、TN和NO3--N浓度均表现为菹草区最高,莲藕区最低,而TP浓度则正好相反;各植被区温室气体浓度和水环境参数间的相关分析和多元回归分析的结果表明,水生植物可通过影响水体的理化性质对温室气体的产生和排放产生显著差异影响,在菹草区亚硝态氮（NO2--N）、NO3--N、T和DO是控制水体温室气体浓度的主要因子;睡莲区为TP和pH;莲藕区则为pH、NO2--N和DO.  相似文献   

10.
涡度相关技术的发展, 为准确获取区域尺度的CO2通量分布格局提供了数据基础. 但由于涡度相关技术自身的局限性, 需要利用模型模拟作为获取区域CO2通量的重要手段. 可是CO2通量和其他微气象变量之间的非线性关系给模拟CO2通量的时空动态变化带来了一定的困难.人工神经网络模型为模拟CO2通量与其他微气象变量的非线性关系提供了一种新的手段. 在ChinaFLUX三个不同类型(农田、森林、草地)生态系统中, 基于2003年6~8月的半小时涡度相关观测数据, 采用BP人工神经网络模型, 以能量通量(净辐射、潜热、显热和土壤热通量)以及温度(空气温度、土壤温度)和表层土壤水分作为输入变量, 模拟了CO2通量的动态变化. 结果表明, 人工神经网络模型具有较好的模拟结果, 其R2系数在0.75与0.866之间.RMSE在0.008 ?mol/m2与0.012 ?mol/m2之间, MAE在1.38 ?mol/m2与3.60 ?mol/m2之间, 其中农田和森林生态系统的模拟精度略高于草地生态系统.其次, 通过比较土壤水分要素是否参与模拟的结果表明, 在生长季期间, 不存在土壤水分胁迫的情况下, 土壤水分的参与并不能显著提供模型模拟的精度. 最后, 应用连接权重方法进行了神经网络模型不同输入变量的重要性分析, 指出神经网络模型不完全是一个黑箱模型, 也可以有效地揭示出某些机理性现象.该研究证明, 神经网络模型不仅可以有效地模拟CO2通量, 也可以揭示出一些机理现象, 为通过涡度相关观测与遥感反演技术的集成途径, 利用已获取的区域尺度能量通量数据, 模拟分析区域尺度的CO2通量分布格局提供了一种有效的方法.  相似文献   

11.
The atmospheric carbon dioxide (CO2) concentration has been consistently increasing each year throughout the world. Internal combustion (IC) engines are significant contributors to CO2 emissions. This study explores the possibility of employing effective biomass-based adsorbents to mitigate CO2 from a diesel engine exhaust. As a first step, two distinct agro-wastes, namely, i) corn cob and ii) sugarcane bagasse, are used to prepare inexpensive and efficient activated carbons. The two main steps in the activated carbon preparation are a) carbonization and b) activation. The derived activated carbons are subjected to discrete analytical techniques to examine their structural and textural characteristics, surface functional groups, and physical, chemical, and adsorptive properties. As a second step, the exhaust treatment chamber unit is filled with the adsorbents one by one and is connected to the exhaust of the constant pressure heat addition engine. A single-cylinder, four-stroke, naturally-aspirated, air-cooled, direct injection (DI) compression ignition (CI) engine is used in the experimental investigations. The essential findings show that ≈68 and 60% of CO2 emissions are adsorbed in the test engine by utilizing corn cob and sugarcane bagasse adsorbents, respectively. The results show that during the D100 and JME20 operations, the prospective adsorbents can curb more than 40% of overall CO2 emissions.  相似文献   

12.
The aim of this study was to assess whether acoustic emission (AE) could carry information on preferential sorption/desorption of CH4 or CO2 in coal. AE and expansion/contraction of two nearly identical cylindrical coal samples were continuously monitored during displacement sorption experiments. One sample was subjected to presorption of CH4, followed by sorption of CH4/CO2 mixture. With the other one, presorption of CO2 preceded sorption of the mixture. The results obtained are the following: first, AE and stain kinetics show that the affinity of the coal tested is higher for CO2 than for CH4; second, methane is preferentially desorbed after presorption of CH4 — sorption of mixture of CH4 and CO2; third, during displacement sorption, kinetics of AE and sample swelling/shrinkage bring out the importance of presorption and the sorbate used. It matters whether the coal is first exposed to CH4 or to CO2. The present study has demonstrated that injection of CO2 into the coal previously exposed to CH4 causes considerable swelling of the coal. On desorption after CH4/CO2 exchange sorption, initial shrinkage is followed by swelling of the coal. These results could have implications for the sequestration of CO2 in coal seams and CH4 recovery from coalbeds (ECBM). Swelling/shrinkage of the coal matrix should be included in models used to predict coal permeability and gas flow rates. They also show that the AE technique can give more insights into coal matrix-gas interactions.  相似文献   

13.
揋reenhouse effect?causing global warming has been an important issue of studying climate change. In the latest 100 years, the earth surface temperature has been increased by about 0.4℃—0.8℃[1,2]. And this has been becoming a hotspot of the world[3,4]  相似文献   

14.
In the Whitehall Forest of Georgia during the 1985-86 non-growing season soil CO2 varied with soil depth, varied spatially at constant depth, and varied temporally with changing environmental conditions. Variations with depth in the upper 1.4 m of the soil were of greater magnitude than temporal variations and spatial differences at 30 cm depth were of lesser magnitude. Mean soil CO2 in evergreen forest was higher (0.207 per cent) than in deciduous and mixed forest (0.157 per cent). There were no trends in soil CO2 along hillslopes or with changes in soil texture, bulk density, moisture content, or temperature. Soil CO2 did increase near trees possibly due to increased root densities and/or more numerous pockets of microbial activity. For CO2 at 30 cm depth, two variables–the mean daily temperature range in the month before measurement and actual evapotranspiration in the week before measurement (AET7)–explained 76 per cent of the variation in mean soil CO2. At the profile site, where soil CO2 was measured at five depths, 66 per cent of the variability in CO2 was explained by soil depth, AET7, and the average daily temperature range in the two months before measurement.  相似文献   

15.
This study investigated CO2 degassing and related carbon isotope fractionation effects in the Wiesent River that drains a catchment in the karst terrain of the Franconian Alb, Southern Germany. The river was investigated by physico‐chemical and stable isotope analyses of water and dissolved inorganic carbon during all seasons along 65‐km long downstream transects between source and mouth. Calculated pCO2 values at the source were 21 400 ± 2400 µatm. The pCO2 rapidly decreased in the river water and dropped to an average of 1240 ± 330 µatm near the mouth. About 90% of this decrease occurred within the first 6 km of the river. The river was supersaturated with respect to CO2 over its entire course and must have acted as a continuous year‐round CO2 source to the atmosphere. The average CO2 flux from the karst river was estimated with 450 mmol m?2 day?1 with higher fluxes up to 5680 mmol m?2 day?1 at the source. At the source, δ13CDIC values showed no seasonal variations with an average of ?14.2 ± 0.2‰. This indicated that groundwater retained high pCO2 mainly from soil CO2. The contribution of soil CO2 to dissolved inorganic carbon was estimated at 65% to 72%. The downstream CO2 loss caused a positive shift in δ13CDIC values of 2‰ between source and mouth because of the preferential loss of the 12C isotope during degassing. Considering the findings of this study and the fact that carbonate lithology covers a significant part of the earth's surface, CO2 evasion from karst regions might contribute notably to the annual carbon dioxide release from global freshwater systems. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

16.
Soils release more carbon, primarily as carbon dioxide (CO2), per annum than current global anthropogenic emissions. Soils emit CO2 through mineralization and decomposition of organic matter and respiration of roots and soil organisms. Given this, the evaluation of the effects of abiotic factors on microbial activity is of major importance when considering the mitigation of greenhouse gases emissions. Previous studies demonstrate that soil CO2 emission is significantly affected by temperature and soil water content. A limited number of studies have illustrated the importance of bulk density and soil surface characteristics as a result of exposure to rain on CO2 emission, however, none examine their relative importance. Therefore, this study investigated the effects of soil compaction and exposure of the soil surface to rainfall and their interaction on CO2 release. We conducted a factorial laboratory experiment with three soil types after sieving (clay, silt and sand soil), three different bulk densities (1·1 g cm–3, 1·3 g cm–3, 1·5 g cm–3) and three different exposures to rainfall (no rain, 30 minutes and 90 minutes of rainfall). The results demonstrated CO2 release varied significantly with bulk density, exposure to rain and time. The relationship between rain exposure and CO2 is positive: CO2 emission was 53% and 42% greater for the 90 minutes and 30 minutes rainfall exposure, respectively, compared to those not exposed to rain. Bulk density exhibited a negative relationship with CO2 emission: soil compacted to a bulk density of 1·1 g cm–3 emitted 32% more CO2 than soil compacted to 1·5 g cm–3. Furthermore we found that the magnitude of CO2 effluxes depended on the interaction of these two abiotic factors. Given these results, understanding the influence of soil compaction and raindrop impact on CO2 emission could lead to modified soil management practices which promote carbon sequestration. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

17.
A model for calculating CO2 flux in the wheat field and an algorithm for estimating CO2 flux in the mejonal scale were presented using the remote sensing data and supplementary micpo-met~orological data. First of all a-longertenn measurement wae carried out during winter wheat growing period in Yucheng Experimental Station udng the spectmradiometer system, the thermal infrared radiometer system, the Bowen-ratio device as well as the eddy-correlation device. Two kinds of issues concerning remote sensing and CO2 flux can be obtained. Based on the obeervations a remote sensing model was estabilished. Then when the NOAA-AVHRR passed over the experimental area simultaneous measurements were carried out with the satellites. A regional distribution image for CO2 flux over wheat canopy in North China (500×500 km2) was made using the supplementary ground data and NOAA-AVHRR remote sensing data which was calibrated by the synchronous observation. The sources and sinks for CO2 fluxes in the region can be seen obviously. Project supported by the National Natural Science Foundation of China (Grant Nos. 49671058, 49890330)  相似文献   

18.
本文介绍了国家气候中心发展的一个全球海洋碳循环环流模式,并分析评估了该模式的基本性能.该模式是在美国地球物理流体动力学实验室(GFDL,Geophysical Fluid Dynamics Laboratory)的全球海洋环流模式MOM4(Modular Ocean Model Version 4)基础上发展的一个垂直方向40层、包含生物地球化学过程的全球三维海洋碳循环环流模式,简称为MOM4_L40(Modular Ocean Model Version 4 With 40Levels).该模式在气候场强迫下长期积分1000年,结果分析表明,与观测相比,模式较好地模拟了海洋温度、盐度、总二氧化碳、总碱、总磷酸盐的表面和垂直分布特征.模拟的海洋总二氧化碳分布与观测基本相符,表层为低值区,其下为高值区,高值区域位于10°S—60°N之间,但2000m以上模拟值较观测偏小,2000m以下模拟值较观测偏大.总体来说,MOM4_L40模式是一个可信赖的海洋碳循环过程模拟研究工具.  相似文献   

19.
An understanding of the symbiotic water and gas exchange processes at the ecosystem scale is essential to the development of appropriate restoration plans of extracted peatlands. This paper presents ecosystem scale measurements of the atmospheric exchange of water and carbon dioxide (CO2) from a restored vacuum extracted peatland in eastern Québec, utilizing full‐scale micrometeorological measurements of both evaporation and CO2. The results indicate that the adopted restoration practices reduce the loss of water from the peat, but CO2 emissions are ～25% greater than an adjacent nonrestored comparison site. The blockage of drainage ditches and the existence of a mulch cover at the site keep the moisture conditions more or less constant. Consequently, the CO2 flux, which is predominantly soil respiration, is strongly controlled by peat temperature fluctuations. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

20.
In the shallow magma chambers of volcanoes, the CO2 content of most basaltic melts is above the solubility limit. This implies that the chamber contains gas bubbles, which rise through the magma and expand. Thus, the volume of the chamber, its gas volume fraction and the gas flux into the conduit change with time in a systematic manner as a function of the size and number of gas bubbles. Changes in gas flux and gas volume are calculated for a bubble size distribution and related to changes in eruption regimes. Fire fountain activity, only present during the first quarter of the eruption, requires that the bubbles are larger than a certain size, which depends on the gas flux and on the bubble content[1]. As the chamber degasses, it loses its largest gas bubbles and the gas flux decreases, eventually suppressing the fire fountaining activity. Ultimately, an eruption stops when the chamber contains only a few tiny bubbles. More generally, the evolution of basaltic eruptions is governed by a dimensionless number, τ * ≈ τgΔρaO2/(18μhc), where τ = a characteristic time for degassing; a0 = the initial bubble diameter; μ = the magma viscosity; and hc = the thickness of the degassing layer. Two eruptions of the Kilauea volcano, Mauna Ulu (1969–1971) and Puu O'o (1983—present), provide data on erupted gas volume and the inflation rate of the edifice, which help constrain the spatial distribution of bubbles in the magma chamber: bubbles come mainly from the bottom of the reservoir, either by in situ nucleation long before the eruption or within a vesiculated liquid. Although the gas flux at the roof of the chamber takes similar values for both eruptions, the duration of both the fire fountaining activity and the entire eruption was 6 times shorter at Mauna Ulu than during the Puu O'o eruption. The dimensionless analysis explains the difference by a degassing layer 6 times thinner in the former than the latter, due to a 2 year delay in starting the Mauna Ulu eruption compared to the Puu O'o eruption.  相似文献   

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