This technical note describes a study on the effect of different dispersing agents and the quantity of same on the grain-size distribution and in particular the percentage of clay size. The results confirm that the existing practice of using 100 mL of standard dispersing agent, viz. sodium hexametaphosphate and sodium carbonate solution, is suitable for marine clays also. The clay size fraction in a marine soil exists in the form of flocs, and hence a dispersing agent is imperative in determining the percentage of clay size fraction. This paper shows that the clay size fraction can vary significantly (4 to 45%) for the marine clays depending upon the dispersing agent used. It also brings out the importance of the need for using an initially moist sample for grain-size analysis in the case of marine clays. Initial air/oven drying before testing induces irreversible aggregation.
Mycosporine-like amino acids (MAAs) are a group of about 20 structurally related water-soluble compounds, widely distributed among freshwater and marine organisms. To provide a better assessment of the diversity and concentration of MAAs in aquatic environments a high-performance liquid chromatography (HPLC) method of analysis based on reverse-phase C18 column and trifluoroacetic acid and an ammonium-containing mobile phase was developed. The improvements with respect to previous methods and the extraction and...
There are still a wide range of concerns about air quality in the vicinity of Ground Zero. Many commercial and residential spaces have yet to be re-occupied. In only a few cases has any sort of inspection or testing been done to determine if they are safe to occupy. The greatest concerns are asbestos and the very irritating concrete dust that spread throughout lower Manhattan during the collapse and the days following.
In Lower Manhattan buildings, whether occupied or not, the potential for problems is not over...
Introduction:
In this process, vacuum extraction is used to remove contaminants from soils. After condensation, contaminants are mixed with a semiconductor catalyst such (e.g., titanium dioxide), and fed through a reactor which is illuminated by sunlight. Ultraviolet light activates the catalyst, which results in the formation of reactive chemicals known as `radicals`. These radicals are powerful oxidizers that break down the contaminants into non-toxic by-products such as carbon dioxide and water.
A big...
Abstract
The risk of sulphate attack and ettringite formation by gypsum pollution is the main reason to limit the use of recycled aggregate in concrete. French standards exclude any possibility of use of recycled aggregate in concrete, restricting the sulphate content of aggregate to 0.15% by mass.
Mortars prepared with various types of cement and recycled aggregates more or less polluted by gypsum were studied with the aim to appraise if a threshold of sulphate content exists for the recycled aggregates over...
Introduction:
As for in situ solidification/stabilization (S/S), ex situ S/S contaminants are physically bound or enclosed within a stabilized mass (solidification), or chemical reactions are induced between the stabilizing agent and contaminants to reduce their mobility (stabilization). Ex situ S/S, however, typically requires disposal of the resultant materials. Under CERCLA material can be replaced on site.
There are many innovations in the stabilization and solidification technology. Most of the innovations...
Introduction
Bioventing is a promising new technology that stimulates the natural in situ biodegradation of any aerobically degradable compounds in soil by providing oxygen to existing soil microorganisms. In contrast to soil vapor vacuum extraction, bioventing uses low air flow rates to provide only enough oxygen to sustain microbial activity. Oxygen is most commonly supplied through direct air injection into residual contamination in soil. In addition to degradation of adsorbed fuel residuals, volatile compounds...
Introduction
Fracturing is an enhancement technology designed to increase the efficiency of other in situ technologies in difficult soil conditions. The fracturing extends and enlarges existing fissures and introduces new fractures, primarily in the horizontal direction. When fracturing has been completed, the formation is then subjected to vapor extraction, either by applying a vacuum to all wells or by extracting from selected wells, while other wells are capped or used for passive air inlet or forced air...
Introduction
An EU Directive is forcing waste disposal sites, such as refuse tips and landfills, to upgrade their anti-leaching precautions. This is especially the case in Sweden. Here, in its home market, Trelleborg is able to provide these sites with an environmentally friendly, seam-weldable rubber membrane to meet the stringent new requirements.
An EU Directive came is now in force that strengthened the environmen-tal requirements for refuse disposal sites. Sweden`s refuse tips have for many years been...
Predictive modeling may be usefelected to represent the system (e.g., SVE treatment, incinerator, etc.), and site and contaminant informaul in estimating emissions from a site or treatment system. An appropriate theoretical model is stion is used to estimate gross emissions. Because many variables affect emission rates, this approach is limited by the representativeness of the model and by the input used. This approach is usually used as a screening-level or pre-design evaluation. Site-specific data to support...
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