Microcosm studies of microbial degradation in a coal tar distillate plume

Investigation of a groundwater plume containing up to 24 g l(-1) phenolic compounds suggested that over a period of nearly 50 years, little degradation had occurred despite the presence of a microbial community and electron acceptors within the core of the plume. In order to study the effect of contaminant concentration on degradation behaviour, laboratory microcosm experiments were performed under aerobic and anaerobic conditions at four different concentrations obtained by diluting contaminated with uncontaminated groundwater. The microcosms contained groundwater with total phenols at ca. 200, 250, 660 and 5000 mg l(-1), and aquifer sediment that had been acclimatised within the plume for several months. The microcosms were operated for a period of 390-400 days along with sterile controls to ascertain whether degradation was microbially mediated or abiotic. Under aerobic conditions, degradation only occurred at concentrations up to 660 mg l(-1) total phenols. At phenol concentrations below 250 mg l(-1) a benzoquinone intermediate, thought to originate from the degradation of 2,5-dimethylphenol, was isolated and identified. This suggested an unusual degradative pathway for this compound; its aerobic degradation more commonly proceeding via catecholic intermediates. Under anaerobic conditions, degradation only occurred in the most dilute microcosm (total phenols 195 mg l(-1)) with a loss of p-cresol accompanied by a nonstoichiometric decrease in nitrate and sulphate. By inference, iron(III) from the sediment may also have been used as a terminal electron acceptor, in which case the amount of biologically available iron released was calculated as 1.07 mg Fe(III)/g of sediment. The study shows that natural attenuation is likely to be stimulated by dilution of the plume.     

A preliminary investigation of the environmental impact of a thermal power plant in relation to PCB contamination

Purpose

The most significant application of polychlorinated biphenyls (PCBs) is in transformers and capacitors. Therefore, power plants are important suspected sources for entry of PCBs into the environment. In this context, the levels and distribution of PCBs in sediment, soil, ash, and sludge samples were investigated around Seyitömer thermal power plant, Kütahya, Turkey. Moreover, identity and contribution of PCB mixtures were predicted using the chemical mass balance (CMB) receptor model.

Methods

United States Environmental Protection Agency methods were applied during sample preparation, extraction (3540C), cleanup (3660B, 3665A, 3630C), and analysis (8082A).

Results

ΣPCB concentrations in the region ranged from not detected to 385 ng/g dry weight, with relatively higher contamination in sediments in comparison to soil, sludge, and ash samples collected from around the power plant. Congener profiles of the sediment and soil samples show penta-, hexa-, and hepta-chlorobiphenyls as the major homolog groups. The results from the CMB model indicate that PCB contamination is largely due to Clophen A60/A40 and Aroclor 1254/1254(late)/1260 release into the sediment and sludge samples around the thermal power plant.

Conclusions

Since there are no other sources of PCBs in the region and the identity of PCB sources estimated by the CMB model mirrors PCB mixtures contained in transformers formerly used in the plant, the environmental contamination observed especially in sediments is attributed to the power plant. Release of PCBs over time, as indicated by the significant concentrations observed even in surface samples, emphasizes the importance of the need for better environmental management.

     

The influence of subsurface thermal structure on the diving behavior of northern fur seals (<Emphasis Type="Italic">Callorhinus ursinus</Emphasis>) during the breeding season

In the heterogeneous marine environment, predators can increase foraging success by targeting physical oceanographic features, which often aggregate prey. For northern fur seals (Callorhinus ursinus), two prevalent oceanographic features characterize foraging areas during summer in the Bering Sea: a stable thermocline and a subsurface “cold pool”. The objective of this study was to examine the influence of these features on foraging behavior by equipping fur seals from St. Paul Island (Alaska, USA) with time-depth recorders that also measured water temperature. Foraging bout variables (e.g., mean dive depth and percent time diving in a bout) were compared with respect to subsurface thermal characteristics (thermocline presence and strength and cold pool presence). Over 74% of bouts occurred in association with strong thermoclines (temperature change > 5°C). Few differences were found for dive behavior in relation to the presence of a thermocline and the cold pool, but for epipelagic bouts, a strong thermocline resulted in increased bottom times, number of dive wiggles, and percent time diving when compared to moderate thermoclines. There was also a positive relationship between mean dive depth and thermocline depth. The combination of increasing foraging effort in areas with strong thermoclines and diving to depths closely related to the thermocline indicates this feature is important foraging habitat for northern fur seals and may act to concentrate prey and increase foraging success. By recognizing the environmental features northern fur seals use to find prey, managers will be better equipped to identify and protect foraging habitat that is important to northern fur seals, and possibly other marine predators in the Bering Sea.     

Insights into aqueous carbofuran removal by modified and non-modified rice husk biochars

Biochar has been considered as a potential sorbent for removal of frequently detected pesticides in water. In the present study, modified and non-modified rice husk biochars were used for aqueous carbofuran removal. Rice husk biochars were produced at 300, 500, and 700 °C in slow pyrolysis and further exposed to steam activation. Biochars were physicochemically characterized using proximate, ultimate, FTIR methods and used to examine equilibrium and dynamic adsorption of carbofuran. Increasing pyrolysis temperature led to a decrease of biochar yield and increase of porosity, surface area, and adsorption capacities which were further enhanced by steam activation. Carbofuran adsorption was pH-dependant, and the maximum (161 mg g^?1) occurred in the vicinity of pH 5, on steam-activated biochar produced at 700 °C. Freundlich model best fitted the sorption equilibrium data. Both chemisorption and physisorption interactions on heterogeneous adsorbent surface may involve in carbofuran adsorption. Langmuir kinetics could be applied to describe carbofuran adsorption in a fixed bed. A higher carbofuran volume was treated in a column bed by a steam-activated biochar versus non-activated biochars. Overall, steam-activated rice husk biochar can be highlighted as a promising low-cost sustainable material for aqueous carbofuran removal.     

Soil organic carbon dynamics of croplands in European Russia: estimates from the “model of humus balance”

The Model of Humus Balance was used to estimate the influence of climate effects and changing agricultural practices on carbon (C) levels in soddy–podzolic soils in the Russian Federation for the years 2000–2050. The model was linked with a spatial database containing soil, climate and farming management layers for identification of spatial change of C sequestration potential. Analysis of relationships between C, soil texture and climate indicated that compared with a business-as-usual scenario, adaptation measures could increase the number of polygons storing soil organic carbon (SOC) by 2010–2020. The rate of possible C loss is sensitive to the different climate scenarios, with a maximum potential for SOC accumulation expected in 2030–2040, thereafter decreasing to 2050. The effect is most pronounced for the arid part of the study area under the emission scenario with the highest rate of increase in atmospheric CO₂ concentration, supporting findings from the dynamic SOC model, RothC. C sequestration during the study period was permanent for clay and clay loam soils with a C content of more than 2%, suggesting that C sequestration should be focused on highly fertile, fine-textured soils. We also show that spatial heterogeneity of soil texture can be a source of uncertainty for estimates of SOC dynamics at the regional scale. Figures in color are available at     

An observational pressure vessel for studying the behaviour of planktonic animals

A design for a pressure vessel, suitable for continuous observation of small planktonic animals at moderate hydrostatic pressures is presented. The long side windows are 3/4 inch (ca. 19 mm) armourplate glass, and smaller windows are provided at each end. The dimensions of the inner working chamber are approximately 16 × 2 × 1 3/4 inches (ca. 0.41×0.05×0.045 m). Internal pressures up to 800 psi (55 bar) have been used successfully during testing. The entire apparatus is placed in a water jacket to provide precise temperature regulation.     

A comparative analysis of the photobiology of zooxanthellae and zoochlorellae symbiotic with the temperate clonal anemone <Emphasis Type="Italic">Anthopleura elegantissima</Emphasis> (Brandt). III. Seasonal effects of natural light and temperature on photosynthesis and respiration

The sea anemone Anthopleura elegantissima hosts two phylogenetically different symbiotic microalgae, a dinoflagellate Symbiodinium (zooxanthellae, ZX) and a chlorophyte (zoochlorellae, ZC). The photosynthetic productivity (P), respiration (R), and contribution of algal carbon translocated to the host (CZAR) in response to a year’s seasonal ambient changes of natural light and temperature are documented for both ZX- and ZC-bearing anemones. Light and temperature both affect photosynthesis, respiration, and CZAR, as well as various algal parameters; while there are evident seasonal differences, for the most part the relative effects on P, R, and CZAR by the two environmental variables cannot be determined. Net photosynthesis (P_n) of both ZX and ZC was significantly higher during spring and summer. During these seasons, the P_n of ZX was always greater than that of ZC. Regardless of algal symbiont, anemone respiration (R) was significantly higher during the spring and summer. The annual net carbon fixation rate of anemones with ZX and ZC was 325 and 276 mg C anemone⁻¹ year⁻¹, respectively, which translates to annual net community productivity rates of 92 and 60 g C m⁻¹ year⁻¹ for anemones with ZX or ZC, respectively. CZAR did not show a clear relationship with season; however the CZAR for ZX was always significantly greater than for ZC. Lower ZX growth rates, coupled with higher photosynthetic rates and higher CZAR estimates, compared to ZC, suggest that if A. elegantissima is simply carbon limited, ZX-bearing anemones should be the dominant symbiont in the field. However ZC-bearing anemones persist in low light and reduced temperature microhabitats, therefore more than the translocation of carbon from ZC must be involved. Given that global climate change will increase water temperatures, the potential for latitudinal range shifts of both ZC and ZX (S. californium and muscatinei) might be used as biological indicators of thermal shifts in the littoral zone of the Pacific Northwest.     

Concentration of atmospheric pollutants in the gaseous emissions of medical waste incinerators

The purpose of this paper is to quantify the production of medical waste from a general hospital and to evaluate the atmospheric pollutant concentrations in gaseous emissions associated with its incineration. A 3.8 kg (bed.day)-1 production of medical waste was estimated for 1998; its incineration is related with an ash production of 0.3-0.4 kg (bed.day)-1. The concentrations of atmospheric pollutants were estimated using emission factors, comparing the effluents with and without control of atmospheric pollutants. The calculated concentrations were compared with the emission limits established by Portuguese legislation. The results indicate that, if there is no control of atmospheric pollutants, their concentrations exceed the established limits. This is observed even if correct operation and maintenance procedures are used. The emission concentrations of dioxins are higher than the Portuguese emission limit, which is particularly worrying due to the high toxicity of some of these compounds. Generally, it is possible to reduce pollutant concentrations if appropriate control equipment is used. The conclusions obtained clearly justify the great concern regarding air pollution associated with medical waste incinerators currently operating in Portugal.     

Non-aqueous-phase-liquid breakthrough during evaporative drying of clay barriers

In this study, an attempt has been made to model a real field scenario, whereby an initially almost saturated clay liner in a waste site is gradually drying, due to evaporation at its lower boundary. A detailed conceptual model that deals with the penetration and breakthrough of non-aqueous-phase-liquid (NAPL) in clay liners is introduced. Water content of clay samples was monitored during ambient evaporation through apertures at the base of sample holders. Clay drying rate served as the primary parameter for the NAPL breakthrough study. The interconnection between drying rates, structural damage formation (cracks and suction) and NAPL penetration is especially addressed. The processes taking place in the clay samples during drying appear to be associated with the capillary effects between the different fluid phases in the vicinity of either the NAPL-clay or the clay-air boundaries. A conceptual model of NAPL penetration and breakthrough of the clay layer has been considered, based on both indirect and direct observations of structural damages produced on either clay boundaries. A mutual interaction between these two boundaries is suggested and discussed. NAPL breakthrough is suggested to take place through cracks initiated on the upper soil surface.