Posts Tagged 'methods'



Increasing seawater alkalinity using fly ash to restore the pH and the effect of temperature on seawater flue gas desulfurization

Wet type flue gas desulfurization (FGD) using lime or limestone is popular because of its operational simplicity and the availability of lime and limestone. Seawater FGD (SWFGD) utilizes the alkalinity of seawater, and its efficiency varies depending on the seawater alkalinity. This study examined the effects of temperature, gas/water ratio, and total alkalinity of the absorbing solution on the removal efficiency of SO2 from flue gas by seawater. In addition, this study showed the possibility of increasing the total alkalinity of seawater using fly ash from coal power plants. The experimental results showed a 8% increase in removal efficiency, while temperature decreased by 10 °C from 25 °C under the conditions of a gas/water ratio of 100 and a resultant pH of 3. The increase in removal efficiency with increasing alkalinity was measured as 0.27%/ppm of bicarbonate alkalinity. This study showed that fly ash has the ability to increase the total alkalinity of seawater. The pH restoration experiment was conducted using fly ash and limestone. The conceptual design processes of SWFGD using NaOH, fly ash, and limestone for a 400 MW coal power plant were developed, and the material balance was calculated using ASPEN Plus software.

Continue reading ‘Increasing seawater alkalinity using fly ash to restore the pH and the effect of temperature on seawater flue gas desulfurization’

Tampa Bay ocean and coastal acidification monitoring quality assurance project plan

Coastal acidification caused by eutrophication, freshwater inflow, and upwelling is already affecting many estuaries worldwide and can be exacerbated by ocean acidification that is caused by increasing carbon dioxide in the atmosphere. Effective management, mitigation, and (or) adaptation to the effects of coastal and ocean acidification require careful monitoring of the resulting changes in seawater chemistry. Local, regional, and national agencies and institutions organizing acidification-monitoring and research efforts work toward standardizing data collection and reporting protocols so that data can be shared and compared across regions and synthesized into national assessments. This document describes a Quality Assurance Project Plan for the collection and reporting of seawater chemical and physical data using standardized methods and published best practices relevant for monitoring coastal and ocean acidification. The plan specifically addresses procedures for a joint partnership, the Tampa Bay Ocean and Coastal Acidification Monitoring project, conducted by the U.S. Geological Survey, the U.S. Environmental Protection Agency, and the Tampa Bay Estuary Program in the Tampa Bay estuary, Florida. The plan describes recommended procedures for project organization, sampling process design and methods, data-quality objectives and criteria, data validation and management procedures, and project deliverables.

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A low-cost lab-on-a-chip device for marine pH quantification by colorimetry

Highlights

• A Lab-on-a-chip device for marine pH quantification by colorimetry was developed.
• It integrates a microfluidic system and a coupling optical-electronics readout in a single device.
• It uses only 9.6 µL of meta-Cresol Purple for the marine pH quantification.
• The marine pH quantification was similar to commercial equipment with a maximum standard deviation of 0.00208 pH units.
• It can be used as a portable device for in-situ real-time monitoring of seawater pH, helping in the analysis of species’ distribution in aquatic habitats.

Abstract

This paper presents a novel lab-on-a-chip for seawater pH measurement that features in-situ, autonomous, long-term and low-cost measurements. It comprises a poly(dimethylsiloxane) microfluidic system and an integrated low-cost optical-electronic system that uses light emitting diodes as light source and photodiodes as the detectors. The pH measurement is based on the colorimetric method, by optical absorption, using the meta-Cresol Purple (mCP) as indicator dye. Only 9.6 µL of this mCP is needed to perform the pH measurement. Under the developed optimized conditions presented here, e.g., microfluidic channels geometry, indicator dye and seawater volumes, the device has a resolution of 0.002 pH units for the 7.500 to 8.200 seawater pH units range, with a significantly reduction of the optical path length to 5 mm and a total detection time of about 8 min. The lab-on-a-chip features high sensitivity, linearity and reproducibility. This approach will allow, in the future, the lab-on-a-chip to be moored in a submerged base, located in the depth of the ocean due to its inherent pressure independent operability, in opposition to conventional electrochemical methodologies.

Continue reading ‘A low-cost lab-on-a-chip device for marine pH quantification by colorimetry’

Calibration of the pH-δ11B and temperature-Mg/Li proxies in the long-lived high-latitude crustose coralline red alga Clathromorphum compactum via controlled laboratory experiments

A solid understanding of global oceanic change throughout Holocene time is needed to contextualize and interpret recent observations of rapid warming (Moore, 2016), ocean acidification (Popova et al., 2014Qi et al., 2017), increasing meltwater input (Halfar et al., 2013Notz and Stroeve, 2016) and circulation changes (Liu et al., 2017Rahmstorf et al., 2015Yang et al., 2016) in the Arctic and subarctic Oceans. Precisely reconstructing acidification and temperature variations throughout the Holocene will provide a vital context for interpreting current environmental changes and future climate projections in the region. However, existing paleoenvironmental reconstructions are sparse and uncertain, largely owing to limited availability of high fidelity paleoceanographic archives, such as marine carbonates, in high latitude waters. Coralline algae of the genus Clathromorphum have emerged as key candidates for reconstructing high-latitude environmental variability at annual to sub-annual resolution. Here, we present the first empirical calibrations of boron isotope-pH and Mg/Li-temperature relationships within the long-lived, crustose coralline red alga Clathromorphum compactum. Calibration experiments were performed in triplicate, growing wild-collected specimens for four months at three controlled temperatures (6.4 – 12.4 oC) and four pCO2 conditions (352 – 3230 ppm), to test the effects of these environmental parameters on the isotopic and elemental composition of the algal skeleton.We find that boron isotopes within the skeleton of C. compactum (δ11Bcc) are well correlated with δ11B of seawater borate (δ11Βborate), defining the following equation: δ11Βcc (2σ) = 1.46 (0.06) δ11Βborate + 6.91 (0.72). This equation can be used to reconstruct δ11Βborate of the coralline alga’s ambient seawater, from which past seawater pH can be calculated. We also identified a strong correlation between skeletal Mg/Li ratio and seawater temperature, defined by the equation: Mg/Li (2σ) = 0.17 (0.02) temperature (oC) + 1.02 (0.16). Therefore, despite the strong biological control that this species appears to exert on calcification site pH (elevated 1.0-1.6 pH units above seawater pH, inferred from δ11Bcc > δ11Βborate), and the apparent relationship between skeletal extension rate and skeletal Li/Ca and Mg/Ca, the δ11Bcc and Mg/Li ratios of the coralline alga’s skeleton strongly and significantly respond to ambient seawater pH and temperature, respectively. These results support the use of δ11B and Mg/Li within C. compactum for pH and temperature reconstructions of northern high-latitude oceans.

Continue reading ‘Calibration of the pH-δ11B and temperature-Mg/Li proxies in the long-lived high-latitude crustose coralline red alga Clathromorphum compactum via controlled laboratory experiments’

Studentized bootstrap model-averaged tail area intervals

In many scientific studies, the underlying data-generating process is unknown and multiple statistical models are considered to describe it. For example, in a factorial experiment we might consider models involving just main effects, as well as those that include interactions. Model-averaging is a commonly-used statistical technique to allow for model uncertainty in parameter estimation. In the frequentist setting, the model-averaged estimate of a parameter is a weighted mean of the estimates from the individual models, with the weights typically being based on an information criterion, cross-validation, or bootstrapping. One approach to building a model-averaged confidence interval is to use a Wald interval, based on the model-averaged estimate and its standard error. This has been the default method in many application areas, particularly those in the life sciences. The MA-Wald interval, however, assumes that the studentized model-averaged estimate has a normal distribution, which can be far from true in practice due to the random, data-driven model weights. Recently, the model-averaged tail area Wald interval (MATA-Wald) has been proposed as an alternative to the MA-Wald interval, which only assumes that the studentized estimate from each model has a N(0, 1) or t-distribution, when that model is true. This alternative to the MA-Wald interval has been shown to have better coverage in simulation studies. However, when we have a response variable that is skewed, even these relaxed assumptions may not be valid, and use of these intervals might therefore result in poor coverage. We propose a new interval (MATA-SBoot) which uses a parametric bootstrap approach to estimate the distribution of the studentized estimate for each model, when that model is true. This method only requires that the studentized estimate from each model is approximately pivotal, an assumption that will often be true in practice, even for skewed data. We illustrate use of this new interval in the analysis of a three-factor marine global change experiment in which the response variable is assumed to have a lognormal distribution. We also perform a simulation study, based on the example, to compare the lower and upper error rates of this interval with those for existing methods. The results suggest that the MATA-SBoot interval can provide better error rates than existing intervals when we have skewed data, particularly for the upper error rate when the sample size is small.

Continue reading ‘Studentized bootstrap model-averaged tail area intervals’

Accurate determination of total alkalinity in estuarine waters for acidification studies

Highlights
• This work studies the best way to determine alkalinity in estuarine waters.

• The usefulness of some available stability constants of the CO2 system were tested.

• A mixing of two existing sets of stability constants gave the optimum results.

• Non-linear least square regression was the best approach to determine alkalinity.

Abstract
One of the effects of the atmospheric CO2 increase is the ocean acidification. Over the past 20 years, accurate measurements of the seawater carbonate system have become a high priority because this is the main system controlling seawater acidity. However, this phenomenon has not been widely studied in estuaries, even if they are among the most productive natural habitats in the world, lodging some of the highest biotic diversity and production. Due to that lack of information, this work aims to develop and discuss new strategies for the determination of total alkalinity (TA), one of the most measured parameters in the study of acidification, in estuarine waters in the wide range of salinities that can be found in these systems. For that purpose, a new set of stability constants for the carbonate system was established and compared with those most widely used up to date. For the determination of TA, different approaches were studied for the data treatment of the potentiometric titration data.

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Detecting the calcium carbonate saturation state under the stress of ocean acidification using saturometry technique

CO2-induced ocean acidification lowers the degree of carbonate saturation state of the seawater, which affects calcification of marine organisms and influences the marine carbonate cycle, thus have negative impacts on the entire marine biogeochemical system. This study seeks to develop a rapid technique to detect carbonate saturation state of seawater based on conductivity changes. A series of batch and flow-through experiments were conducted using various CaCO3 materials. Results show that the conductivity ratios of seawater with and without carbonate addition increase generally with decreasing carbonate saturation states (Ω). The relationship between conductivity ratio and log10Ω apparently follows a linear trend when Ω < 1. It suggests that conductivity measurements can be used to indicate carbonate saturation state of seawater. It is expected to be deployed on CTD instrument to produce depth profiles of seawater carbonate saturation state and will be of great help to future studies on ocean acidification.

Continue reading ‘Detecting the calcium carbonate saturation state under the stress of ocean acidification using saturometry technique’


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Ocean acidification in the IPCC AR5 WG II

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