Biodegradation kinetics of surfactants in seawater.

In this paper, a general kinetic model for degradation processes of surfactants is proposed. The model equation is v = K2S2 + K1S + K0, where v is the substrate consumption rate in the biodegradation process, S is the surfactant concentration in the medium and K2, K1, and K0 are kinetic constants. From this general expression, different simplified equations can be obtained (where K0 = 0; K2 and K0 = 0; K2 = 0; K2 and K1 = 0), which are representative of the process for different operating conditions. This model was tested by measuring the degradation of two different surfactants (Sodium dodecyl benzene sulfonate, LAS; and Sodium dodecyl sulfate, DSNa) under two different temperatures (5 and 20 degrees C). Values predicted by the model are close to experimental data obtained.     

Life-history parameters and vertical distribution of Maurolicus muelleri in Masfjorden in summer

Population characteristics, individual life-history variables, feeding and vertical distribution of the mesopelagic fish Müller's pearlside Maurolicus muelleri collected in 1990 in Masfjorden, western Norway, are reported as well as environmental variables from the fjord. Minimum size at maturity was far smaller than reported from previous investigations in the same region. Fecundity was size-dependent and total egg numbers were higher than reported from other investigations of M. muelleri world wide, while the number of maturing eggs was far lower than observed in the same region earlier. Food concentration in the fjord was an order of magnitude lower than previous early summer observations, and several factors indicated that feeding opportunities may have been low for a long period. Daily feeding rate (g prey g^-1 fish) decreased with increasing fish size. These observations fit well with a model of maximizing fitness by means of a flexible size at maturity. Minimum age at maturity seems to be achieved at the expense of fecundity. M. muelleri was concentrated in a 20 to 30 m deep sound scattering layer (SSL). The SSL stayed close to the surface during the night and at 100 to 180 m during the daytime. The vertical position of the SSL varied instantaneously with changes in surface light intensity, remaining at 10^-3 to 10^-4 mol m^-1 s^-1 at the top of the SSL. Stomach fullness was highest during the night; feeding intensity seems to have been peaked at dusk. Cladocerans were the main prey ranked by number, copepods by biomass. Intake of large copepods increased with fish size.     

Cadmium in the diet and body tissues of dunlins Calidris alpina, from the Bristol channel, UK

Cadmium levels were determined in sediments, sediment-dwelling invertebrates and in one of their predators, the dunlin, at five sites in the Bristol Channel. The highest sediment cadmium levels were found in the Taff Estuary and at Avonmouth. The highest invertebrate levels were found at Avonmouth and Swansea. In dunlins, the highest cadmium levels were found in the kidneys, followed by the liver, sternum and pectoral muscle. Adult males had higher levels than adult females. Although first year birds of both sexes had low levels, these increased throughout the course of the winter. There was no simple correlation between the amount of cadmium in the sediments, and that in invertebrates or birds, although the levels in both sediments and invertebrates reached a peak in mid-winter. The most contaminated birds were, however, found closest to a known point source of cadmium.     

Urban observatories opportunities for environmental monitoring: solid wastes

Towns concentrate around 50% of world-wide population and the trend is oriented to underscore an urban profile of population. In addition, towns have become important for their economic contribution to the Gross Internal Product. The negative side of towns is the environmental and social impacts as a result of productive and domestic activities, besides the lack of available data. In order to overcome these shortcomings, the United Nations has established a project of urban monitoring throughout the Global Network of Urban Observatories; Mexico joined the project in 2005. The Local Urban Observatory of Mexicali has the task to produce information about cities that is useful to design public policies. Some of this information deals with a set of environmental indicators in the United Nations Habitat Agenda, which includes solid wastes. Therefore, this paper deals with two main topics; firstly, from the Habitat Agenda, a comparative urban analysis of waste production and coverage of domestic waste collection services; secondly, from the Local Agenda, the identification and ranking of environmental problems according to public perception coming from people involved in the municipal planning and decision making process. Results will be used to develop local indicators and public environmental policies.     

Increase of the purification efficiency of biofilters by the use of a complementary ionisation step

The biofilter and the ionisation system are two oxidative treatment techniques for purification of waste gas streams with low concentrations of volatile organic compounds. In this paper, the authors present the investigations of an ionisation technique aimed at increasing the efficiency of the reduction of the odorant concentration in waste gas streams from biological waste treatment plants. The objective is to enable advanced odour emission reduction and to adjust the existing biofilters to stricter requirements. In a first step, the odorous substances which are major contributors to the overall odorant concentration are identified on basis of various emission data sets with the help of a method of life cycle impact assessment. Thereby limonene, alpha-pinene, ethyl butyrate and dimethyl disulphide were identified as crucial indicators. In a second step, experimental investigations using limonene as a model compound were conducted to gain an understanding of the ionisation process itself and at last for the evaluation of the system.     

Physical modelling of the composting environment: a review. Part 1: Reactor systems

In this paper, laboratory- and pilot-scale reactors used for investigation of the composting process are described and their characteristics and application reviewed. Reactor types were categorised by the present authors as fixed-temperature, self-heating, controlled temperature difference and controlled heat flux, depending upon the means of management of heat flux through vessel walls. The review indicated that fixed-temperature reactors have significant applications in studying reaction rates and other phenomena, but may self-heat to higher temperatures during the process. Self-heating laboratory-scale reactors, although inexpensive and uncomplicated, were shown to typically suffer from disproportionately large losses through the walls, even with substantial insulation present. At pilot scale, however, even moderately insulated self-heating reactors are able to reproduce wall losses similar to those reported for full-scale systems, and a simple technique for estimation of insulation requirements for self-heating reactors is presented. In contrast, controlled temperature difference and controlled heat flux laboratory reactors can provide spatial temperature differentials similar to those in full-scale systems, and can simulate full-scale wall losses. Surface area to volume ratios, a significant factor in terms of heat loss through vessel walls, were estimated by the present authors at 5.0-88.0m(2)/m(3) for experimental composting reactors and 0.4-3.8m(2)/m(3) for full-scale systems. Non-thermodynamic factors such as compression, sidewall airflow effects, channelling and mixing may affect simulation performance and are discussed. Further work to investigate wall effects in composting reactors, to obtain more data on horizontal temperature profiles and rates of biological heat production, to incorporate compressive effects into experimental reactors and to investigate experimental systems employing natural ventilation is suggested.     

Mathematical model for carbon dioxide evolution from the thermophilic composting of synthetic food wastes made of dog food

The impacts of the aeration and the agitation on the composting process of synthetic food wastes made of dog food were studied in a laboratory-scale reactor. Two major peaks of CO(2) evolution rate were observed. Each peak represented an independent stage of composting associated with the activities of thermophilic bacteria. CO(2) evolutions known to correlate well with microbial activities and reactor temperatures were fitted successfully to a modified Gompertz equation, which incorporated three biokinetic parameters, namely, CO(2) evolution potential, specific CO(2) evolution rate, and lag phase time. No parameters that describe the impact of operating variables are involved. The model is only valid for the specified experimental conditions and may look different with others. The effects of operating parameters such as aeration and agitation were studied statistically with multivariate regression technique. Contour plots were constructed using regression equations for the examination of the dependence of CO(2) evolution potentials on aeration and agitation. In the first stage, a maximum CO(2) evolution potential was found when the aeration rate and the agitation parameter were set at 1.75 l/kg solids-min and 0.35, respectively. In the second stage, a maximum existed when the aeration rate and the agitation parameter were set at 1.8 l/kg solids-min and 0.5, respectively. The methods presented here can also be applied for the optimization of large-scale composting facilities that are operated differently and take longer time.     

Transformation of ecological conditions of soil and humus substance formation in the urban environment

Ecological conditions of soil formation and specific features of humus substance formation are considered with regard to urban soils of different types formed in the following functional zones: the park zone, residential area, and sanitary protective zone of the Middle Ural Copper-Smelting Plant. The specificity of soil formation in Revda, a typical industrial city of the Middle Urals, is determined by the combined effect of urban and technogenic factors (urbogenesis and technogenesis), with the former being of primary importance. At a constant period of biological activity, the depth of humification is primarily a function of granulometric and chemical composition of urban soils.Translated from Ekologiya, No. 1, 2005, pp. 11–19.Original Russian Text Copyright © 2005 by Meshcheryakov, Prokopovich, Korkina.     

Application of the operating window concept to remediation‐option selection

An Erratum has been published for this article in Remediation 14(4) 2004, 141. The selection of remediation options for the management of unacceptable risks at contaminated sites is hindered by insufficient information on their performance under different site conditions. Therefore, there is a need to define “operating windows” for individual remediation options to summarize their performance under a variety of site conditions. The concept of the “operating window” has been applied as both a performance optimization tool and decision support tool in a number of different industries. Remediation‐option operating windows could be used as decision support tools during the “options appraisal” stage of the Model Procedures (CLR 11), proposed by the Environment Agency (EA) for England and Wales, to enhance the identification of “feasible remediation options” for “relevant pollutant linkages.” The development of remediation‐option operating windows involves: 1) the determination of relationships between site conditions (“critical variables”) and option performance parameters (e.g., contaminant degradation or removal rates) and 2) the identification of upper‐ and lower‐limit values (“operational limits”) for these variables that define the ranges of site conditions over which option performance is likely to be sufficient (the “operating window”) and insufficient (the “operating wall”) for managing risk. Some research has used case study data to determine relationships between critical variables and subsurface natural attenuation (NA) process rates. Despite the various challenges associated with the approach, these studies suggest that available case study data can be used to develop operating windows for monitored natural attenuation (MNA) and, indeed, other remediation options. It is envisaged that the development of remediation‐option operating windows will encourage the application of more innovative remediation options as opposed to excavation and disposal to landfill and/or on‐site containment, which remain the most commonly employed options in many countries. © 2004 Wiley Periodicals, Inc.     

Respiration rates of<Emphasis Type="Italic"> Beroe ovata</Emphasis> in the Black Sea

Metabolic rates of the ctenophore Beroe ovata within the length range from 0.4 mm (newly hatched larvae) to 60 mm were investigated. At 20° the respiration rates (Q, µg O₂ ind.^–1 h^–1) of individuals with wet weights (W, mg) less than or greater than 100 mg changed according to the equations Q=0.093W^0.62 and Q=0.016W^0.99, respectively. The weight-specific respiration rate of the juvenile ctenophores with wet body weights of 0.021–100 mg diminished approximately 20-fold (from 0.35 to 0.017 µg O₂ mg^–1 h^–1, respectively), but did not change within the range from 100 to 30,000 mg. The difference in the slope of the regression lines seems to be attributable to the ontogenetic changes in B. ovata metabolism. For the tested temperature range of 10–28°, the mean Q₁₀ coefficient was equal to 2.17±0.5. The basal metabolism of B. ovata narcotised by chloral hydrate was 4.5±0.9 times lower than total metabolism. Such a metabolic range is considered to be characteristic of aquatic invertebrates with high levels of locomotory activity.Communicated by O. Kinne, Oldendorf/Luhe