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新疆博斯腾湖水体颗粒和溶解有机碳的季节变化及其来源初探 总被引：5，自引：2，他引：3
在博斯腾湖选取了13个点位,于2012年5、8、10月测定表层和底层水体中的颗粒有机碳、溶解有机碳、颗粒有机氮和叶绿素a含量.结果显示颗粒和溶解有机碳在表层水体中的浓度与底层相近.博斯腾湖水体中颗粒有机碳的季节变化十分明显,其平均浓度从春季(0.64 mg/L)到夏季(0.71 mg/L)变化不大,但在秋季变化十分显著(浓度达1.58 mg/L).其中西北湖区和湖心区颗粒有机碳的季节变化最明显,东部湖区颗粒有机碳的季节变化相对较小.博斯腾湖水体的颗粒有机碳在春、秋两季主要来自外源输入,在夏季受水体中浮游生物的影响较大.博斯腾湖水体中溶解有机碳也具有一定的季节变化,夏季浓度(平均为9.3 mg/L)略低于春、秋两季(平均为10.3 mg/L).溶解有机碳在河口区的季节变化最强,其夏季浓度明显偏低,主要是由于开都河河水的稀释作用.总体上,博斯腾湖水体中溶解有机碳浓度的变化主要受外部因素的影响. 相似文献
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CEVSA模型是一个基于生理生态过程模拟植物-土壤-大气系统能量交换和水碳氮耦合循环及其对环境变化响应和适应的机理模型,在区域和全球尺度上得到广泛应用.尽管该模型在大尺度上已经应用大量的植被生产力,碳储量和叶面积测定以及遥感反演数据进行了验证,但还缺乏在冠层和景观尺度上对模型的机理过程(如对光合,呼吸和蒸散过程及其导致的水碳通量变化)模拟的检验.以近年来生态系统机理过程研究的最新进展为基础,对模型进行改进,应用一个亚热带针叶林水碳通量连续观测数据对模型模拟结果进行检验,并分析机理模拟与涡度相关观测得到的水碳通量与环境条件关系的差异.模型模拟的主要水碳通量季节变化特征均与观测值一致.对蒸散和土壤水分的模拟结果与观测值相近,分别解释了观测值90%和86%的变异性,但是模拟值系统偏低.模拟的年总光合碳固定(GPP)和生态系统呼吸(Re)接近于观测值,并且能够分别解释其观测值79%和88%的变异性.尽管净生态系统生产力(NEP)的模拟值(394 gC/m2)也与观测值(387.15 gC/m2)接近,但是它仅能解释观测值31%的变异性.与观测值相比,模拟的NEP在冬季偏低而在夏季偏高.通过与温度、水汽压差的相关分析表明,在严重的高温和缺水胁迫条件下,模型没有准确模拟生态系统光合和呼吸过程.结果证明CEVSA模型对水碳循环的模拟与植被冠层尺度水碳通量测定结果一致,但仍然需要对极端温度和水分胁迫效应的模拟作进一步的ChinaFLUX. 相似文献
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贵州省草海表层水体和沉积物间隙水中汞的含量和形态分布初步研究 总被引：10，自引：1，他引：9
运用金汞齐-冷原子荧光光谱法(CVAFS)和气相色谱技术(GC),对贵州省草海不同水文季节(枯水期和丰水期)表层水中汞的各种赋存形态,包括总汞(HgT)、溶解态汞(HgD)、活性汞(HgR)、颗粒态汞(HgP)、总甲基汞(MeHgT)、溶解态甲基汞(MeHgD)和颗粒态甲基汞(MeHgP)以及沉积物间隙水剖面中的溶解态总汞和甲基汞含量进行了测定.结果显示:草海表层水体总汞浓度为1.7-9.0ng/L,活性汞浓度为0.06-1.4ng/L,总甲基汞浓度为0.11-0.67ng/L.沉积物间隙水中溶解态汞浓度为8.6-39.6ng/L,溶解态甲基汞浓度为0.11-4.9ng/L.实验数据表明,草海湖水以溶解态汞为主,其占总汞的比例为枯水期87%,丰水期51%,溶解态汞与总汞呈显著相关(丰水期P<0.01;枯水期P<0.05),颗粒态汞与总汞也呈显著相关(丰水期P<0.01;枯水期P<0.05).溶解态甲基汞与总甲基汞呈显著相关(丰水期P<0.01;枯水期P<0.05),表明溶解态甲基汞控制总甲基汞的分布.沉积物间隙水溶解态汞与溶解态甲基汞浓度明显高于上覆水体,表明沉积物为草海湖水中汞的一个重要来源. 相似文献
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氨氮是地表水常见污染物,尤其在农业区域,氮类化肥的不合理施用会导致周边水体氮浓度迅速升高并保持较高水平.然而,当前对高氮水平下沉水植物腐败和附着氮循环微生物的影响尚不清楚.以轮叶黑藻(Hydrilla verticillata)为研究用沉水植物,在实验室内模拟水体内8和16 mg/L氮浓度下轮叶黑藻腐解过程中营养盐释放及残体表面微生物氮循环功能基因丰度的变化.研究发现水体两种氮浓度下轮叶黑藻腐解过程中残体腐解及营养盐释放速率无显著差异;与对照相比,植物腐败初期水体内碳、磷浓度迅速增加,而溶解氧浓度及氧化还原电位迅速降低,随着时间的推移上述水质指标逐步恢复至初期状态(第146天);水体荧光溶解性有机质主要包括紫外类富里酸、可见类富里酸、色氨酸类蛋白质和酪氨酸类蛋白质等类型.在5个氮循环相关基因中,氮负荷增加对轮叶黑藻残体生物膜内amo A、napA和narG的丰度有显著影响.冗余分析表明氮循环基因丰度受水体总氮浓度的影响较小,与植物总有机碳含量和水体化学需氧量及溶解氧浓度存在相关性.研究结果表明虽然当前氮水平对植物腐败过程影响不大、对氮循环基因丰度有一定影响,但是对该水生植被(尤其是植物腐败初期)和农业退水排放的管理仍需加强,以降低其对水体的影响. 相似文献
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CFC-11是评估全球海洋环流模式的一个重要工具,海水中溶解的CFC-11被用来分析全球海洋模式的通风模拟.本文在中国气象局国家气候中心发展的40层全球海洋环流模式(MOM4_L40)增加了示踪物CFC-11模块,然后利用该模式研究了CFC-11在全球海洋中的分布,并评估了模式的通风能力.对CFC-11的海表浓度、柱总含量以及大洋剖面的垂直浓度分布和渗透深度进行了分析,结果表明,与观测相比,模式较好地再现了CFC-11在海洋表面的水平分布特征,CFC-11主要储存区位于西北大西洋、副热带北太平洋及南大洋,其浓度分布与温度分布梯度相反.沿三个大洋的5个剖面的CFC-11垂直分布模拟也与观测基本吻合.模式模拟的CFC-11分布情况与全球平均经向流函数吻合,在南大洋模拟效果更加接近观测值,深海模拟效果较好,渗透深度接近观测.同时,模拟与观测相比也存在偏差.比如在北大西洋主要的存储区域,模式低估了CFC-11的吸收,这与高纬的CFC-11向低纬过度输送有关,可能是受温盐环流和强迫资料的影响.总体来说,MOM_L40模式模拟大洋吸收的CFC-11总量是理想的,通过模拟被动示踪物CFC-11很好地再现了海洋的通风能力. 相似文献
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河流及水库等水生态系统中的溶解性无机碳(DIC)是全球碳循环与大气、陆地和海洋之间碳相互作用的重要组成部分.以澜沧江云南段上游天然河段及下游梯级水库群形成的连续体为研究对象,分析了河库连续体表层水体中水化学特征、溶解性无机碳浓度及其碳同位素时空分布特征.研究结果表明:河库连续体水体中溶解无机碳(DIC)及其同位素(δ13 C DIC)组成特征总体表现为:DIC浓度丰水期较低,枯水期较高,平均值分别为2.59±0.44和3.30±0.37 mmol/L;δ13 C DIC值丰水期偏负、枯水期偏正,平均值分别为-8.52‰±0.38‰和-6.95‰±0.53‰,与自然河流的季节变化特征相似.水体DIC来源主要包括土壤及水体有机质分解生成的CO 2、碳酸盐风化和水气界面CO 2的交换过程.澜沧江河库连续体中DIC浓度及δ13 C DIC组成的时空异质性特征与流域岩性、土壤生物地球化学过程以及微生物活动强度等均有较大关系.当前,澜沧江梯级水库群建库时间短,梯级联合运行下调度复杂,水文条件多变,梯级水库对河流重要生源要素——碳累积影响方面的“水库效应”还不明显. 相似文献
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四川盆地东北部三叠系飞仙关组天然气具有较高的H2S和CO2含量,这是川东北发育热化学硫酸盐还原作用(TSR)的重要依据之一.然而天然气中的CO2显著少于TSR所应有的数量,与H2S相比,CO2显著亏损;同时天然气中CO2在碳同位素组成上并不具有与TSR有关的有机碳的特征,这是一个长期困惑人们的地质现象.根据川东北飞仙关组天然气中CO2的含量及同位素组成,定量计算了TSR来源的有机碳和海相碳酸盐来源的无机碳对天然气中CO2的贡献值,以及这两种来源碳对深埋藏过程从高温流体中沉淀的方解石中碳的贡献值,表明与TSR有关的有机碳源对天然气CO2的贡献值只有约2%,而有机碳源对从高温热流体中沉淀的自生方解石的贡献值高达43%,说明川东北飞仙关组与TSR有关的有机来源的CO2主要进入了自生方解石中,目前天然气中的CO2主要来源于海相碳酸盐的溶解.与之有关的解释是,在TSR发生的相对高温和高PCO2分压的环境中,方解石以沉淀为主,而在TSR发生过后的盆地快速抬升过程中,由于温度大幅度降低,流体对碳酸盐欠饱和而导致溶解作用发生和次生孔隙形成,这是倒退溶解模式的结果.因此,燕山期的构造抬升是川东北飞仙关组碳酸盐在埋藏过程中发生溶... 相似文献
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2013年9月龟井台水氡观测值出现大幅度下降,为了分析其原因,将SD-3B测氡仪与FD-125型两套仪器测得的氡值变化趋势进行对比分析,结合SD-3B测氡仪历年观测资料,对于这一异常现象进行分析,排除各种外界干扰因素以后,认为近期水氡超幅度异常变化是由于降雨骤增地下水动力系统条件改变引起的平衡态转换所致。井水位在-8 m处是临界点。当干旱少雨致使外来渗入补给水不足时,出现井水位低于-8 m,此时很少地表水渗入,观测井水也少有外渗流出,溶解在井水中的氡富集度较高,水氡背景值就在一个较高值的范围内变化。当降水增加致使地下水渗入增加,井水位上升,同时观测井水向外流出,造成地下水动力系统条件改变,氡值就会出现突发性的下降,在井水位高于-8 m后,由于大量渗入的地表水稀释和观测井水向外流出带走大量溶解氡,这一状态下氡浓度会较低,水氡观测背景值在一个较低值范围内变化。 相似文献
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Phosphate behaviour in natural estuarine systems can be studied by performing field measurements and by undertaking laboratory simulation experiments. Thus, in this paper we describe the use of a dynamic automated estuarine simulator to characterize the geochemical reactivity of phosphate in varying salinity gradients in order to study possible mechanisms of phosphate removal from the dissolved phase (e.g. formation of some kind of apatite) and how changes in pH and salinity values influence this removal. Six laboratory assays, representing various salinity and pH gradients (average pH values between 7 and 8), were carried out. The geochemical equilibrium model MINTEQA2 was employed to characterize removal of phosphate. Among the minerals from which dissolved phosphate can originate, it seems that hydroxyapatite is by far the mineral that shows the greatest saturation indexes in the experiments. Thus, there is evidence that a type of calcium phosphate (hydroxyapatite) is involved in phosphate removal in the assays. Phosphate removal by Ca2+ occurs sharply at salinity values of 1–2, whereas by Fe3+ it is relatively gradual, at least until a salinity value of 7. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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不同溶解氧水平下湖泊底泥-水界面磷交换影响因素分析 总被引：15，自引：2，他引：13
在实验室控制条件下,研究了玄武湖底泥在饱和溶解氧、75%、50%、25%、0%溶解氧水平下底泥-水界面磷交换,探讨了溶解氧对底泥-水界面磷交换的影响途径.结果表明:(1)上覆水溶解氧与玄武湖底泥溶解性磷酸盐、溶解性总磷释放速率呈开口向上的抛物线关系;(2)上覆水溶解氧水平可以决定磷在底泥-水界面交换中的转换方向,而且还影响间隙水中溶解氧扩散深度,25%、50%、75%和饱和溶解氧水平下溶解氧最大扩散深度分别为0.974cm、1.377cm、1.687cm和1.948cm,溶解氧在间隙水中最大扩散深度影响底泥-水界面的磷交换;(3)溶解氧可通过影响底泥-水界面处电位、藻类聚磷作用以及pH来影响底泥-水界面的磷交换. 相似文献
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Pollutants are carried by sediment-laden flow dissolved in water or adsorbed on sediment particles. A transient three-dimensional model based on a compressible VOF(volume of fluid) method was developed to simulate the transport of dissolved and particulate pollutants.VOF is a numerical technique for acquiring and tracking the free surface of water flow.Local scouring,deposition and re-suspension were simulated and the processes of adsorption and desorption of pollutants on suspended sediment were analyzed.A series of experiments and numerical simulations were performed to study the transportation and dispersion of pollutants in the flow around a non-submerged spur dyke in a straight flume of rectangular shape.The simulation results agreed well with the experimental results.A certain volume of pollutants solution was released into the flow at upstream of the spur dyke.The concentration reduced with time.The concentration reduction was slower in the circumfluence zone than in the main flow.The ratio of adsorption to desorption coefficients was different for pollutants on suspended sediment with different diameter.The peak concentration of dissolved pollutants increased with the ratio of the adsorption to the desorption coefficients.The angle of the spur dyke affected the peak concentration around the dyke.The effect of the angle on dissolved pollutants decreased with the ratio of adsorption to desorption coefficients.The adsorption and desorption coefficients,as well as the saturated adsorption capacity had no effect on the concentration of particulate pollutants. 相似文献
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Broad‐Scale Evidence That pH Influences the Balance Between Microbial Iron and Sulfate Reduction 
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下载免费PDF全文 Understanding basic controls on aquifer microbiology is essential to managing water resources and predicting impacts of future environmental change. Previous theoretical and laboratory studies indicate that pH can influence interactions between microorganisms that reduce ferric iron and sulfate. In this study, we test the environmental relevance of this relationship by examining broad‐scale geochemical data from anoxic zones of aquifers. We isolated data from the U.S. Geological Survey National Water Information System for 19 principal aquifer systems. We then removed samples with chemical compositions inconsistent with iron‐ and sulfate‐reducing environments and evaluated the relationships between pH and other geochemical parameters using Spearman's rho rank correlation tests. Overall, iron concentration and the iron‐sulfide concentration ratio of groundwater share a statistically significant negative correlation with pH (P < 0.0001). These relationships indicate that the significance of iron reduction relative to sulfate reduction tends to increase with decreasing pH. Moreover, thermodynamic calculations show that, as the pH of groundwater decreases, iron reduction becomes increasingly favorable relative to sulfate reduction. Hence, the relative significance of each microbial reaction may vary in response to thermodynamic controls on microbial activity. Our findings demonstrate that trends in groundwater geochemistry across different regional aquifer systems are consistent with pH as a control on interactions between microbial iron and sulfate reduction. Environmental changes that perturb groundwater pH can affect water quality by altering the balance between these microbial reactions. 相似文献
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The Harsit Stream flowing into the Black Sea is an important watershed in the northeastern part of Turkey. The monthly averages of dissolved oxygen, carbonaceous biochemical oxygen demand, temperature, pH, total suspended solids, total phosphorus and total nitrogen were obtained for the water samples taken from the Tekke, Akcakale and Haciemin sites of the Harsit Stream. Water quality parameters were analyzed and evaluated according to the WHO standards and the Turkish Water Pollution Control Regulation. Initially, the variations in the dissolved oxygen profile were determined from dissolved oxygen, temperature and carbonaceous biochemical oxygen demand measurements by using the point source Streeter‐Phelps equation. Critical dissolved oxygen deficit values were calculated for the monthly average from January–December 2005, which are below the limit value (4 mg L–1) excluding April (7.26 mg L–1) and May (5.98 mg L–1) in the Harsit Stream, resulting in it having second class water quality in terms of dissolved oxygen concentration, temperature, pH and biochemical oxygen demand. It is also seen that the minimum dissolved oxygen limit value (8 mg L–1), which is a desired quantity for drinking water, is under the limit value for all months in the case of the water mixture. In particular, during the summer months, the consumption speed of oxygen is greater than the production speed of oxygen with increasing temperature and decreasing discharge, and negative values (anoxia) of dissolved oxygen sag are seen. These situations call for significant precautions and treatment criteria. 相似文献
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Wastewater with high ammonia concentrations is produced by many industries, e.g. in the production of fertilizer and explosives and in the agricultural and food industry. A direct discharge into rivers and lakes has to be avoided: Oxidation of ammonia requires 4.56 g DO/g NH+4-N and results in a decrease of dissolved oxygen concentration. Moreover, nitrate stimulates the proliferation of algae, with regard to the eutrophication of natural waters. For municipal wastewater with an ammonia concentration less than 50 mg/L NH+4-N nitrification is a standard process. However, the removal of higher loaded industrial effluents still poses many questions. Recently, lab-scale and pilot-scale investigations show remarkable advances in the increase in nitrification efficiency and in the stabilization of the process. But because of changing flowrates and concentrations, the aid of advanced control algorithms is necessary. Some of the most important variables of biochemical reactors can be determined only with difficulty, at times only with off-line measurements. Model-aided measurement approaches try to determine these variables indirectly from easily measured variables. An experimentally-proved reactor model is required. Therefore, a dynamic model of nitrification in ideally mixed reactors is proposed based on mass balances for the components ammonia. nitrite, nitrate. dissolved oxygen DO, carbon dioxide, pH. nitrosomonas and nitrobacter. The biological reaction rates consider oxygen limitation and substrate inhibition. The process model presented is tested by lab scale experiments using an aerated stirred tank reactor and a fluidized bed reactor. Conformity between the predictions of the model and the observed data was positive. It has been shown that the nitrite oxidation by nitrobacter is the most sensible step in nitrification. 相似文献
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井孔水温对远场巨震同震响应及其机制的数模研究 总被引：2，自引：0，他引：2
热量的流动必然伴随着温度的改变, 地震活动期间的井孔水温同震响应也服从热力学的基本规律。 本文以汶川8.0级地震和日本9.0级地震为例, 以海口ZK26井水温同震响应的观测数据为基础, 运用热力学传导方程的数值模拟方法, 研究了同震响应过程中井孔水温度变化与热量传导之间的关系及相关的热力学机制问题.通过正演的方法, 得出沿井深方向不同时刻水温同震响应变化的数值模拟曲线, 水温数值模拟曲线与实际测量数据一致. 研究结果表明, 井孔中水温同震响应方式(上升、 下降或不变), 与水温传感器的位置、 热源的位置和分布、 传感器与热源之间的相对空间等因素有关。 相似文献
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Distribution of chlorophyll-a off the Changjiang River and its dynamic cause interpretation 总被引：1，自引：1，他引：1
ZHU Jianrong State Key Laboratory of Estuarine Coastal Research East China Normal University Shanghai China 《中国科学D辑(英文版)》2005,48(7)
Red tide,also called harmful algal bloom interna-tionally,is a disaster abnormal phenomenon of oceanecology with an explosive breed or dense assemble ofone or several phytoplanktons in a specific ocean en-vironment condition,colors the seawater,influencesand harms ocean living things.The formation of redtide is controlled mainly by a complex interplay ofbiological,physical and chemical processes,but themost main cause influencing the occurrence of red tideis the seawater eutrophication,i.e.,the… 相似文献