Seasonal variations of aerosol residence time in the lower atmospheric boundary layer

During a one year period, from Jan. 2002 up to Dec. 2002, approximately 130 air samples were analyzed to determine the atmospheric air activity concentrations of short- and long-lived (222Rn) decay products 214Pb and 210Pb. The samples were taken by using a single-filter technique and gamma-spectrometry was applied to determine the activity concentrations. A seasonal fluctuation in the concentration of 214Pb and 210Pb in surface air was observed. The activity concentrations of both radionuclides were observed to be relatively higher during the winter/autumn season than in spring/summer season. The mean activity concentration of 214Pb and 210Pb within the whole year was found to be 1.4+/-0.27 Bq m(-3) and 1.2+/-0.15 mBq m(-3), respectively. Different 210Pb:214Pb activity ratios during the year varied between 1.78 x 10(-4) and 1.6 x 10(-3) with a mean value of 8.9 x 10(-4) +/- 7.6 x 10(-5). From the ratio between the activity concentrations of the radon decay products 214Pb and 210Pb a mean residence time (MRT) of aerosol particles in the atmosphere of about 10.5+/-0.91 d could be estimated. The seasonal variation pattern shows relatively higher values of MRT in spring/summer season than in winter/autumn season. The MRT data together with relative humidity (RH), air temperature (T) and wind speed (WS), were used for a comprehensive regression analysis of its seasonal variation in the atmospheric air.     

The integrated programme for commodities: An assessment of negotiations on minerals and metals

No agreement has yet emerged from the negotiations on mineral commodities held under the Integrated Programme for Commodities (IPC), and there is little, if any, prospect for one in the near future. This article examines the reasons for this standstill and the underlying assumptions on which the IPC is based. The following points are raised: the premise that problems of individual commodities are mutually exclusive and can be dealt with in a single framework of measures is shown to be doubtful; the principle of a commodity-by-commodity approach can no longer remain unchallenged; and structural flaws in the negotiating machinery are manifest. However, results of negotiations have not been entirely negative: the need for two-tier preparatory negotiations has been accepted and a case for a permanent consultative body, perhaps covering several commodities, has been made out. Lack of substantive reciprocity, hence political discord, remains the stumbling-block.     

Moderation of dust explosions

Inherent safety is a proactive approach to process safety in which hazards are removed or minimized so as to reduce risk without engineered (add-on) or procedural intervention. Four basic principles are available to attain an inherently safer design—minimization, substitution, moderation, and simplification. The subject of the current paper is the principle of moderation as it applies to the prevention and mitigation of dust explosions.

Moderation can be achieved by processing a material under less severe operating conditions or by processing the material in a less hazardous form. With respect to the latter approach, it may be possible to alter the composition of a dust by admixture of solid inertants, or to increase the dust particle size so as to decrease its reactivity. Additionally, avoidance of the formation of hybrid mixtures of explosible dusts and flammable gases is an application of moderation of the material hazard.

Several examples are given for each of the above three forms of moderation. The discussion on admixture of solid inertants includes examples from the following industrial applications: (i) refractory materials manufacturing, (ii) food processing, (iii) power generation, (iv) industrial recycling, and (v) foundry shell mold fabrication. The importance of particle size consideration is explained first from the perspective of engineering tools such as the Dow Fire & Explosion Index, and professional guidance on the definition of a dust and suitable particle sizes for explosibility testing. Industrial examples are then drawn from the following areas: (i) rubber recycling and textile manufacturing, (ii) industrial recycling, (iii) wood processing, (iv) dry additive handling (polyethylene facility), (v) polyethylene production, (vi) carbon block recycling, and (vii) coal mining. The concluding discussion on hybrid mixtures includes brief cases from the process safety literature.     

WASTE WATER DISPOSAL THROUGH A COASTAL AQUIFER1

ABSTRACT: Feasibility of disposing treated sewage in wells sunk into a partially confined coastal limestone aquifer at Waimanalo in the island of Oahu was investigated using an electric analog model. Electric analog modeling was preferred over digital modeling because of ease with which tides could be generated at the ocean boundary in the form of sinusoidal waves. The results of model operation showed that high permeability, low storativity, and the presence of ocean render the Waimanalo aquifer highly suitable for the disposal of waste water in deep wells. Since the quality of water in the aquifer is already unsuitable for municipal, industrial, or agricultural use, waste water injection will not result in any loss of fresh water supply source to the island. It is also believed that the cost of waste water disposal through the aquifer will be considerably less than that through an ocean outfall. During model development it was discovered that electric analog models can help prepare certain graphs which can be useful for aquifer analysis without any further use of the model.     

COMPARISON OF TWO AUTOREGRESSIVE MODELS FOR MONTHLY STREAM FLOW GENERATION1

ABSTRACT: Two autoregressive models for monthly stream flow generation are compared based on the reproduction of the historical record in terms of several important statistics such as the mean, standard deviation, skewness coefficient, correlation coefficient, and the reservoir storage components. In the comparison, both theoretical considerations and practical applications are employed to evaluate the performance of each model.     

Spore inhibition-based enzyme substrate assay for monitoring of aflatoxin M1 in milk

A spore germination-based concept and its transformation into a field level prototype for monitoring aflatoxin M₁ (AFM₁) in milk was developed. Initially, 15 strains of Bacillus spp. procured from different culture collection were screened for AFM₁ sensitivity using spot assay and marker strain showing inhibition at 0.5 ppb was selected based upon maximum zone of inhibition. The selected strain B. megaterium 2949 was further screened for different enzymes activities and subsequently its spores were produced to an extent of 73.13% ± 3.197% in newly developed sporulation medium containing beef extract (0.0075% ± 0.0004%), yeast extract (0.015% ± 0.001%), peptone (0.0375% ± 0.0016%), and sodium chloride (0.0375% ± 0.0018%). A spore germination-based concept/ assay was optimized by immobilizing spores in eppendorf with pretreated milk (80°C/15 min) containing germinant and chromogenic substrate followed by incubation at 37°C. The appearance of sky blue color within real time of 45 min indicated spores germination and release of specific marker enzyme such as acetyl esterase and its specific action on chromogenic substrate which demonstrates absence of AFM₁ in milk. However, if there was no color change, presence of AFM₁ at 0.5 ppb MRL was denoted by Codex. The developed concept on AFM₁ detection was validated and a correlation of 0.97 was established with AOAC approved Charm 6602 and ELISA at Codex MRL with minimal false positive and negative results. The cost effective test has potential application in dairy farms, manufacturing, and R&D units for routine monitoring of AFM₁ in milk.     

Risk analysis of an LPG storage facility in India

An assignment to carry out a hazard study and risk analysis of a gas processing complex has been described briefly, wherein well known procedures have been used to identify and investigate potential hazards. A method of avoiding unintentional overfilling of LPG storage tanks has been recommended, which utilizes the existing level control instruments.     

The CO2 abatement cost curve for the Thailand cement industry

The cement industry is one of the largest carbon dioxide (CO₂) emitters in the Thai industry. The cement sector accounted for about 20,633 kilotonnes (ktonnes) CO₂ emissions in 2005 in Thailand. A bottom-up CO₂ abatement cost curve (ACC) is constructed in this study for the Thai cement industry to determine the potentials and costs of CO₂ abatement, taking into account the costs and CO₂ abatement of different technologies. The period of 2010–2025 is chosen as the scenario period. We analyzed 41 CO₂ abatement technologies and measures for the cement industry. Using the bottom-up CO₂ ACC model, the cost-effective annual CO₂ abatement potential for the Thai cement industry during the 15 year scenario period (2010–2025) is equal to 3095 ktonnes CO₂/year. This is about 15% of the Thai cement industry’s total CO₂ emissions in 2005. The total technical annual CO₂ abatement potential is 3143 ktonnes CO₂/year, which is about 15.2% of the Thai cement industry’s total CO₂ emissions in 2005. We also conducted a sensitivity analysis for the discount rate parameter.