1,720,970 research outputs found
Distributions of total alkalinity in surface waters of the northern South China Sea during summer
No full textTotal alkalinity (TA) is an important parameter in the carbon cycle and the carbonate system. The Taiwan Strait and the northern South China Sea (nSCS) are very complex marginal oceanic areas under the influence of Kuroshio intrusion and river plumes. It is important to understand the distribution of TA in a complex environment. In this study, we used the data of three summer cruises to the South China Sea (2019), southern Taiwan Strait (2020), and Pearl River shelf (2020) to analyze the spatial distribution of TA at nSCS.
The results of this study found that Sigma-\uce\ub8 of 20.5 kg m-3 in the surface water on the nSCS can be used as the boundary between the surface water of the Western Pacific Ocean and the Pearl River plume. When Sigma-\uce\ub8 is greater than 20.5 kg m-3, the average NTA was 2302.7\uc2\ub110.9 \uce\ubcmol kg-1, which is consistent with the TA characteristics of the western Pacific seawater (NTA=2301\uc2\ub19 \uce\ubcmol kg-1). This study uses polynomial regression analysis to further sort out the relationship between salinity, total alkalinity, and depth in the vertical water layer. Using the salinity and depth to simulate the total alkalinity, the relationship between the salinity and depth of the nSCS and the total alkalinity is obtained. The difference between the simulated and the measured TA values is less than 0.3%. When Sigma-\uce\ub8 in the surface seawater was lower than 20.5 kg m-3, the NTA value began to rise significantly. In this study, two sets of two-end-member model between the Pearl River water and seawater were simulated. The result shows that evaporation and precipitation might affect seawater and river water before their mixing and further change corresponding salinity, total alkalinity, and Sigma-\uce\ub8 to deviate from the range of simulation results. On the Sigma-\uce\ub8 vs. NTA graph, a few data points may only be the result of the mixture between seawater and rainwater.
The results of this study show that the TA distribution of surface water in the nSCS in summer is mainly controlled by three factors: surface water from the western Pacific Ocean, freshwater of the Pearl River, and evaporation and precipitation. It is necessary to consider the sequence of these three factors during the entire mixing process. Therefore, it is necessary to refer to meteorological information when interpreting data to understand the effects of evaporation and rainfall on the mixing process
Development of an Automated Spectrophotometric pH measuring System and the Assessment of pH Electrode calibration in Coastal Oceans
No full textThe ocean has absorbed 1/3 of anthropogenic carbon dioxide (CO2) since the Industrial Revolution, leading to a decreasing trend of seawater pH, so-called \ue2Ocean Acidification\ue2. Since 1993, the spectrophotometric pH analysis provides an exact method to measure seawater pH. However, the pH samples from estuaries and coastal oceans are generally characterized by high dissolved organic matter concentration, which can bias the spectrophotometric method. Therefore, the glass electrode calibrated by the spectrophotometric method is recommended for pH measurements. This study developed an automatic pH measuring system with a microfluid cell (Automatic Modular Microfluid Optical spectrophotometer; AMMO spectrophotometer) and further simulated spectrophotometric pH electrode calibration by CO2SYS.
The precision and accuracy of the AMMO spectrophotometer are examined in six ways. The precision is mainly influenced by absorbance, temperature, and dye perturbation, and their influences on pH are \uc2\ub10.0011, \uc2\ub10.0021, and \uc2\ub10.0007 pH unit, respectively. The overall precision of a seawater sample is better than 0.002 pH unit. The accuracy is comparable to a Cary 50 spectrophotometer (-0.0013 pH unit), and the overall accuracy is ~0.006 pH unit (uncertainty of tris buffers).
This is the first study that applied simulations through CO2SYS to evaluated electrode intercept potential (E0). We also assessed the uncertainties of E0 by comparing the experimental and the simulation results. The results showed that E0 might decrease with increasing salinity when salinity 15. Ignoring the salinity effect on E0 may lead to uncertainty in pH accuracy as large as 0.20 pH unit (S: 0 ~ 34). Furthermore, in low salinity and high TA environments, the bias of pH measurements obtained by spectrophotometrically calibrated electrodes may increase to ~0.20 pH unit. We suggest using seawater with similar TA and DIC as the samples to calibrate the pH electrode with the spectrophotometric method
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Physioecological studies on Thalassia hemprichii growth in lagoon of Dongsha Island
No full textSeagrass, a submerged marine vascular plant that inhabits sandy coastal water, is a blue-carbon plant of the ecosystem. Dongsha Atoll is located 450 kilometers from Taiwan in the South China Sea, and there are seagrass beds in and around the lagoon of Dongsha Island. The thickness of substrates or sediments was about 10 times in inner lagoon than outer lagoon, and the density of the seagrass Thalassia hemprichii in the lagoon was higher than that outside the lagoon, and the plants appeared to be shorter in aboveground, and the total biomass per unit area above ground and underground were higher than that outside the lagoon. The results of the elemental analysis indicated that the carbon content was higher in the lagoon than outside the lagoon, and the nitrogen and sulfur content were same. The total carbon per unit area of Thalassia in the lagoon was 2.5 times that outside the lagoon, and the fixed amount of CO2 converted to CO2 was about 420 g/m2 in the lagoon while only 150 g/m2 outside the lagoon. The PSII activity determined using chlorophyll a fluorescence and the chlorophyll and carotenoids concentrations were similar for Thalassia in the lagoon and the outside lagoon, reflecting a similar photosynthetic activity in the lagoon and outside lagoon. Therefore, a higher areal CO2 fixation amount in the lagoon is resulted from large biomass due to higher plant density. Since leaf detritus can accumulate in the lagoon due to slow water flow, it facilitates both aerobic and anaerobic metabolisms and in turn, influences carbon flux in the waters and CO2 availability, next, total alkalinity (TA), pCO2, and H2CO3 in pore water were analyzed. Dissolved inorganic carbon (DIC) were analyzed. The results showed that TA, pCO2, and H2CO3 in the lagoon were 1,717 \uc2\ub5mol/kg, 2,407 \uc2\ub5mol/kg, 109 \uc2\ub5atm, and 2 \uc2\ub5mol/kg, respectively, which TA was higher than that outside lagoon while others were lower than outside lagoon. It implied that aerobic and anaerobic metabolisms in the lagoon was higher than outside lagoon and the transport of CO2 from roots to shoots can be enhanced for photosynthesis. The present findings demonstrated that Thalassia can adapt to Dongsha Island lagoon via higher rhizome distribution ability to build up a higher plant density per unit area in the thicker sediments with normal photosynthetic efficiency and thus higher areal carbon sequestration
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Reconciliation of pH<sub>25</sub> and pH<sub>insitu</sub> acidification rates of the surface oceans: A simple conversion using only in situ temperature
No full textDispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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