黄河流域硅酸盐风化的讨论（2）——流域耗水量对化学风化消耗大气CO2的贡献

由于流域人类活动对水资源的消耗,使河流下游径流量降低,因此研究流域化学风化时必须考虑耗水量的贡献。本文根据课题组2007年黄河流域的化学风化数据,结合流域耗水量,重新估算了黄河流域硅酸盐风化大气CO2的消耗量和消耗率,分别为19.92×109mol.a-1和26.50×103mol.km-2.a-1。黄河流域耗水量对硅酸盐风化消耗大气CO2的贡献已经达到了入海径流量所表征的数量级。针对黄河流域岩石分布类型复杂的特点,作者提出了分段考虑耗水量的计算方法,定量给出了黄河上、中、下游硅酸盐风化CO2的消耗量和消耗率。黄河流域硅酸盐风化CO2消耗率上游>中游>下游,消耗量中游>上游>下游。上、中游硅酸盐风化CO2的消耗量分别为下游的33和37倍左右。     

黄河流域硅酸盐风化的讨论

根据2007年6月和7月采集的黄河干流及部分支流水样和河床砂样品数据,对黄河流域硅酸盐化学风化进行了探讨。在充分评估黄河流域的K+,Na+来源的基础上,确定了硅酸盐风化的K+量,并通过选定的硅酸盐风化(K/Na)比值,得到了硅酸盐风化的Na+量;通过测定流域内不同岩石类型分布的河床砂样品,得到河床砂样品硅酸盐部分(Ca/Na)和(Mg/K)的比值,确定了钙镁硅酸盐风化的Ca2+,Mg2+量;并据此估算了流域硅酸盐化学风化的CO2消耗率。如果选用黄河入海多年径流量58.02×109km3/a进行计算,则得到全流域硅酸盐风化CO2消耗率约为26.22×103mol/km2/a。若选用2007年的平均径流量24.83×109km3/a进行计算,则黄河流域硅酸盐风化引起的CO2消耗率约为11.19×103mol/km2/a。     

黄河青藏高原亚流域主要支流化学风化CO_2消耗及DIC输运

Wang等提出了青藏高原亚流域是黄河水体中高DIC的主要来源,是黄河DIC输运通量主要贡献者的观点。然而青藏高原亚流域最大的三条支流—洮河、湟水和大通河均位于青藏高原与黄土高原的交界处,流域面积总和约占青藏高原亚流域的25%,主要支流化学风化对大气CO_2的消耗量,以及CO_2消耗主要来自于青藏高原部分还是主要与黄土分布相关值得关注。本文根据2015年8月对洮河、湟水和大通河及干流兰州站的调查采样,运用Forward模型分析河水主要离子来源,研究了各支流化学风化强度。结果表明:洮河、湟水和大通河三条支流的化学风化大气CO_2消耗量分别为54.85×108、33.77×108和50.04×108 mol·a-1,CO_2消耗率分别为21.96×104、22.01×104和33.08×104 mol/km2·a,并以碳酸岩风化消耗为主。三条支流CO_2消耗量占青藏高原亚流域的32.8%,DIC输运通量占31.9%,且主要来自与黄土有关的青藏高原与黄土高原交错地带以及黄土高原部分。     

夏威夷玄武岩的植物风化

含钙、镁硅酸盐矿物的风化是影响地质时期大气中ＣＯ２含量的一个重要过程。风化淅出的钙和镁在溶液中被搬运到海洋里,并在那里作为碳酸盐沉淀下来。不同地质时期化学风化作用受地壳运动引起的陆地面积、位置和地形的变化、全球气候的变化、岩石类型暴露的变化和生物进化...     

地下水灌溉回水对黄河流域化学风化CO_2消耗估算的影响

本文根据2012年6月和2013年5月采集的河南、宁夏和内蒙等引黄灌区地下水实测数据,并结合文献数据,探讨了引黄灌区地下水离子组成的分布特征。结果表明:因受蒸发作用和人为因素影响较小,深层地下水矿化度和HCO-3的浓度小于浅层水,但HCO-3占阴离子比例大于浅层水。因各灌区蒸发量、降雨量以及岩性的不同,浅层地下水化学组成和风化来源阳离子浓度在各灌区表现出较大的差异。HCO-3占阴离子的比例在河南灌区最高,内蒙灌区中部和宁夏灌区次之,内蒙灌区东西部最低。河南和内蒙灌区风化来源阳离子浓度相差不多,均大于宁夏灌区。灌区浅层地下水灌溉回水高估的黄河流域化学风化消耗CO2的量为23.3×108 mol/a。     

长江人海途程的化学质量转移 Ⅰ.主要溶解组分的来源与迁徙

本文阐明了长江下游水体中的主要溶解组分,主要是由蒸发岩和碳酸盐经化学风化作用所提供的。其中,SO_4部分由化石燃料燃烧后生成的SO_2在大气中氧化成SO_3,并随降雨生成H_2SO_4而进入河水,同时还分析了长江在入海过程中,各溶解组分的浓度受物理混合的影响以及可能发生的转移和溶出作用。     

大气中CO2含量的控制因素及其对气候的影响

碳是地球上最重要的生命元素,以不同的物质形态在各个圈层循环,引起大气中CO2含量的变化,百万年级别的CO2变化属于构造尺度,其主要控制因素是大陆化学风化对于CO2的消耗速率;次级时间尺度为10万a及以下,大气CO2通过生物泵作用从碳源到碳汇循环往复,调节着地球上的气候环境演化.人类出现以后,特别是工业革命以来,人为排放的CO2破坏了原有的自然碳循环,同时也成为新的碳循环的重要制衡因素.     

海底反风化作用与关键元素循环

海洋环境中的反风化作用是指硅与可溶性阳离子结合形成自生铝硅酸盐矿物(黏土),同时消耗海洋碱度并释放CO₂的过程。反风化假说提出半个多世纪以来,作为全球海洋碳、硅和关键元素循环以及海洋碱度的重要调控机制,越来越受到学术界的关注。反风化作用可发生在河口三角洲与边缘海、热液或深埋藏的成岩环境以及深海远洋等环境,但不同海洋环境中的反风化反应从发生时间尺度到反应限制因素都具有差异。反风化作用研究的主要方法包括自生硅酸盐矿物的直接观测、孔隙水与沉积物的化学分析、实验模拟和模型研究等,而反风化作用的程度量化、限制因子解析和对海洋关键元素循环的影响一直是反风化研究的关键问题。当前快速发展的非传统稳定(金属)同位素技术为反风化研究带来了新机遇。东亚大陆边缘发育世界特大河口三角洲、宽广陆架以及特色热液活动区,泥质沉积体系发育,界面交换活跃,是开展大陆边缘反风化研究的天然实验室。     

河流-河口-近海连续体碳循环研究进展

河流-河口-近海连续体(简称连续体)是连接陆地和大洋的过渡地带,也是目前全球碳收支估算的薄弱环节.这个复杂的海陆交互生态系统不仅可以通过光合作用、溶解作用吸收大气中的CO2,陆地和流域光合作用或化学风化作用固定的碳也可以被横向输送到陆架和大洋中.本文以国际上著名的切萨皮克湾以及长江-长江口-东海等为例,综述了连续体碳循...     

中国海洋碳循环生物地球化学过程研究的主要进展(1998-2002)

阐述了1998-2002年期间中国海洋碳循环及其生物地球化学过程研究的3个主要进展部分：（1）海-气二氧化碳通量过程；（2）海水中碳及其生物地球化学循环；（3）入海河流流域土壤和沉积物在海洋碳循环中的作用；海洋与陆家容纳了近一半人类排放的二氧化碳，另外的50%被释放到大气中，海洋在缓和二氧化碳温室效应方面的作用不言而喻的，海洋储有的碳主要以无机碳的碳酸盐（CO3^2-）和碳酸氢盐（HCO3^-）的形式存在。海洋生态系统通过生物泵的作用驱动大气CO2进入海洋，在表面混合层中，由于生物的光合作用，CO2不断被转化成有机碳和生物碳酸盐，并进一步从表层CO2向深层转移，形成了海洋碳循环的主要途径，海洋水体中碳循环过程受到河口与近海碳的形态，转化，分布，迁移和生物生产过程等影响，海洋生物泵明显影响着海洋对空气中CO2的容量，春季和冬季东中国海皆为大气二氧化碳的汇，夏季皆为二氧化碳的源，秋季渤海与北黄海为二氧化碳的汇，南黄海与东海是二氧化碳的源。入海河流流域土壤，非入海河流流域的土壤和海洋沉积物在碳的来源，分布，含量以其迁移循环中具有重要的作用。     

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.     

Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level.     

Deep-Sea Sediment Compression Curves: Some Controlling Factors, Spurious Overconsolidation, Predictions, and Geophysical Reproduction

Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations.     

INFORMATION FOR AUTHORS

<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology,     

Estimation of Sediment Properties during Benthic Impact Experiments

Sediment properties, such as water content and density, have been used to estimate the dry and wet weights, as well as the volume of sediment recovered and discharged, during benthic impact experiments conducted in the Pacific and Indian Oceans. The estimates show that the weights of dry (355-1332 t) and wet sediment (1651-4888 t) recovered during the experiments, are not only a function of the total duration and distance covered during the experiment, but also depend on water content and density of the sediment. Estimation of dry sediment and its volumetric ratio in the discharge, are key parameters for calculating the discharged volume. The estimated volume of wet sediment recovered (1427-4049 m 3 ) as well as discharged (2693-6951 m 3 ) during the experiments, provide important inputs to evaluate the sediment resettlement and migration. Using these estimates, the average depth of excavation on the seafloor, can also been calculated. However, the stages of sediment recovery and discharge are expressed differently in some of the experiments. In order to standardize these, different stages have been identified, and definitions of certain terms have been suggested, for use in the future. The methods of calculating different properties, as well as weight and volume of discharged sediment are described in the paper for use in other applications concerning deep-sea discharges.