Microbial degradation of chlorinated dioxins

Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) were introduced into the biosphere on a large scale as by-products from the manufacture of chlorinated phenols and the incineration of wastes. Due to their high toxicity they have been the subject of great public and scientific scrutiny. The evidence in the literature suggests that PCDD/F compounds are subject to biodegradation in the environment as part of the natural chlorine cycle. Lower chlorinated dioxins can be degraded by aerobic bacteria from the genera of Sphingomonas, Pseudomonas and Burkholderia. Most studies have evaluated the cometabolism of monochlorinated dioxins with unsubstituted dioxin as the primary substrate. The degradation is usually initiated by unique angular dioxygenases that attack the ring adjacent to the ether oxygen. Chlorinated dioxins can also be attacked cometabolically under aerobic conditions by white-rot fungi that utilize extracellular lignin degrading peroxidases. Recently, bacteria that can grow on monochlorinated dibenzo-p-dioxins as a sole source of carbon and energy have also been characterized (Pseudomonas veronii). Higher chlorinated dioxins are known to be reductively dechlorinated in anaerobic sediments. Similar to PCB and chlorinated benzenes, halorespiring bacteria from the genus Dehalococcoides are implicated in the dechlorination reactions. Anaerobic sediments have been shown to convert tetrachloro- to octachlorodibenzo-p-dioxins to lower chlorinated dioxins including monochlorinated congeners. Taken as a whole, these findings indicate that biodegradation is likely to contribute to the natural attenuation processes affecting PCDD/F compounds.     

Inorganic nanoparticles enhance the production of reactive oxygen species (ROS) during the autoxidation of L-3,4-dihydroxyphenylalanine (L-dopa)

Public concerns over the toxicity of nanoparticles (NPs) are growing due to the rapid development of nanotechnology. An important mechanism of nanotoxicity is oxidative stress resulting from reactive oxygen species (ROS). In this study, the chemical production of ROS by inorganic NPs oxidizing the mammalian phenolic compound, l-3,4-dihydroxyphenylalanine (l-dopa) was evaluated using a ROS sensitive dye, 2′,7′-diclorodihydrofluorescin (DCFH). CeO₂, Fe₂O₃ and Fe⁰ NPs enhanced ROS production during the autoxidation of l-dopa by more than four-fold in reactions that were dependent on O₂. This is the first report of chemical ROS production due to interaction of phenolic compounds with NPs. Mn₂O₃ oxidized DCFH in a reaction that did not require O₂ or l-dopa, suggesting a direct redox reaction between the Mn₂O₃ and the dye. CeO₂, Mn₂O₃ and to a lesser extent Fe⁰ formed clear electron paramagnetic resonance (EPR) signature for hydroxyl radicals when incubated in aerobic aqueous suspensions with spin traps. The results indicate that NPs can generate ROS via chemical reactions with medium components and biomolecules susceptible to oxidation, such as l-dopa. NPs were reactive whereas micron-sized particles were not. The combined assay with l-dopa and DCFH is a method proposed to screen for chemical ROS production by NPs.     

Anaerobic biodegradability and methanogenic toxicity of key constituents in copper chemical mechanical planarization effluents of the semiconductor industry

Copper chemical mechanical planarization (CMP) effluents can account for 30-40% of the water discharge in semiconductor manufacturing. CMP effluents contain high concentrations of soluble copper and a complex mixture of organic constituents. The aim of this study is to perform a preliminary assessment of the treatability of CMP effluents in anaerobic sulfidogenic bioreactors inoculated with anaerobic granular sludge by testing individual compounds expected in the CMP effluents. Of all the compounds tested (copper (II), benzotriazoles, polyethylene glycol (M(n) 300), polyethylene glycol (M(n) 860) monooleate, perfluoro-1-octane sulfonate, citric acid, oxalic acid and isopropanol) only copper was found to be inhibitory to methanogenic activity at the concentrations tested. Most of the organic compounds tested were biodegradable with the exception of perfluoro-1-octane sulfonate and benzotriazoles under sulfate reducing conditions and with the exception of the same compounds as well as Triton X-100 under methanogenic conditions. The susceptibility of key components in CMP effluents to anaerobic biodegradation combined with their low microbial inhibition suggest that CMP effluents should be amenable to biological treatment in sulfate reducing bioreactors.     

Container contamination as a possible source of a diarrhoea outbreak in Abou Shouk camp, Darfur province, Sudan

Diarrhoea is one of the five major causes of death in an emergency setting and one of the three main causes of death in children (Curtis and Cairncross, 2003). In June 2004, an outbreak of shigellosis was confirmed in Abou Shouk camp in the Northern Darfur province of Sudan. As water testing showed no contamination, it was assumed that post-collection contamination was happening. The decision was taken to launch a programme of mass disinfection of all water containers in order to break the contamination cycle. Diarrhoea figures from the clinics showed a fall in cases following the cleaning campaign. It is extremely difficult to obtain good and statistically rigorous data in an emergency setting, the priority being to intervene rapidly to prevent further cases of diarrhoea. However, the results do appear to indicate that the disinfection programme has had an impact on the prevalence of bloody and watery diarrhoea.     

Using Satellite Fire Detection to Calibrate Components of the Fire Weather Index System in Malaysia and Indonesia

Vegetation fires have become an increasing problem in tropical environments as a consequence of socioeconomic pressures and subsequent land-use change. In response, fire management systems are being developed. This study set out to determine the relationships between two aspects of the fire problems in western Indonesia and Malaysia, and two components of the Canadian Forest Fire Weather Index System. The study resulted in a new method for calibrating components of fire danger rating systems based on satellite fire detection (hotspot) data. Once the climate was accounted for, a problematic number of fires were related to high levels of the Fine Fuel Moisture Code. The relationship between climate, Fine Fuel Moisture Code, and hotspot occurrence was used to calibrate Fire Occurrence Potential classes where low accounted for 3% of the fires from 1994 to 2000, moderate accounted for 25%, high 26%, and extreme 38%. Further problems arise when there are large clusters of fires burning that may consume valuable land or produce local smoke pollution. Once the climate was taken into account, the hotspot load (number and size of clusters of hotspots) was related to the Fire Weather Index. The relationship between climate, Fire Weather Index, and hotspot load was used to calibrate Fire Load Potential classes. Low Fire Load Potential conditions (75% of an average year) corresponded with 24% of the hotspot clusters, which had an average size of 30% of the largest cluster. In contrast, extreme Fire Load Potential conditions (1% of an average year) corresponded with 30% of the hotspot clusters, which had an average size of 58% of the maximum. Both Fire Occurrence Potential and Fire Load Potential calibrations were successfully validated with data from 2001. This study showed that when ground measurements are not available, fire statistics derived from satellite fire detection archives can be reliably used for calibration. More importantly, as a result of this work, Malaysia and Indonesia have two new sources of information to initiate fire prevention and suppression activities.     

Development of the Indonesian and Malaysian Fire Danger Rating Systems

Forest and land fires in Southeast Asia have many social, economic, and environmental impacts. Tropical peatland fires affect global carbon dynamics, and haze from peat fires has serious negative impacts on the regional economy and human health. To mitigate these fire-related problems, forest and land management agencies require an early warning system to assist them in implementing fire prevention and management plans before fire problems begin. Fire Danger Rating Systems (FDRS) were developed for Indonesia and Malaysia to provide early warning of the potential for serious fire and haze events. In particular, they identify time periods when fires can readily start and spread to become uncontrolled fires and time periods when smoke from smouldering fires will cause an unacceptably high level of haze. The FDRS were developed by adapting components of the Canadian Forest Fire Danger Rating System, including the Canadian Forest Fire Weather Index (FWI) System and the Canadian Forest Fire Behavior Prediction (FBP) System, to local vegetation, climate, and fire regime conditions. A smoke potential indicator was developed using the Drought Code (DC) of the FWI System. Historical air quality analysis showed that the occurrence of severe haze events increased substantially when DC was above 400. An ignition potential indicator was developed using the Fine Fuel Moisture Code (FFMC) of the FWI System. Historical hot spot analysis, grass moisture, and grass ignition studies showed that fire occurrence and the ability for grass fires to start and spread dramatically increased when FFMC > 82. The Initial Spread Index (ISI) of the FWI System was used to develop a difficulty of control indicator for grassland fires, a fuel type that can exhibit high rates of spread and fire intensity. This ISI-based indicator was developed using the grass fuel model of the FBP System, along with a standard grass fuel load and curing level estimated from previous Indonesian studies. Very high fire intensity is expected in grasslands when ISI ≥ 6. To provide early warning, the FDRS identifies classes of increasing fire danger as the FFMC, DC, and ISI approach these key threshold values. The Indonesian FDRS is now operated nationally at the Indonesian Meteorological and Geophysical Agency. The Malaysian Meteorological Service operates the Malaysian FDRS and displays regional outputs for the Association of Southeast Asian Nations. The FDRS are being used by forestry, agriculture, environment, and fire and rescue agencies to develop and implement fire prevention, detection, and suppression plans.     

ASPECTS OF THE UNDERWATER LIGHT FIELD OF EIGHT CENTRAL NEW YORK LAKES1

ABSTRACT: The underwater light field of eight central New York lakes, which represent a wide range of trophic state, was characterized through paired measurements of Sechi disc transparency (SD, m) and diffuse light attenuation (K_d, m^?1). A total of 90 paired measurements are included in the data base. Substantial variability in the K_d SD product with time within individual systems, and amongst systems, was observed, which indicates differences in the relative contributions of absorption and scattering to attenuation. More than 50 percent of the temporal variability in K_d was attributable to attendant variations in chlorophyll a (C, mg m^?3) in only two of the lakes. Estimates of the adsorption (a, m^?1) and scattering (b, m^?1) coefficients based on paired K_d and SD measurements compared well with more precise determinations available for one of the lakes. Determinations of a and b for the eight lakes, from SD and K_d measurements, indicated great system-specificity and temporal variability in these characteristics. The temporal variability in relative contributions of a and b to K_d is consistent with covariation of different attenuating components and the lack of correlation between C and K_d in most of the study lakes.     

The world conservation strategy: Environmental education and local initiative

Summary In the spring of 1981, Tufts University and the International Union for the Conservation of Nature began teaching the World Conservation Strategy to environmentalists working at the local level. The fourteen-week course that they offered was the first of a series of initiatives to increase public awareness of the need for local action toward the solution of global environmental problems. The success of the first course has encouraged other groups to adapt it to their own social and ecological settings, but there is a pressing need for even more public education. While several aids to teaching the World Conservation Strategy are now being developed to give local conservation educators access to the Strategy, the initiative for bringing the World Conservation Strategy to the public should continue to come from these local leaders. Frank Thibodeau is an environmental biologist and policy analyst with MA and PhD degrees from Tufts University. He is currently a Research Associate in the Department of Urban and Environmental Policy at Tufts, preparing a book on the World Conservation Strategy as a foundation for local environmental initiative under the auspicies of IUCN and the World Wildlife Fund. In addition to his writing and teaching related to the Strategy, he maintains an active research program examining the development of national and international strategies for the preservation of genetic diversity. Hermann H. Field, an urban planner and Fellow of the American Institute of Architects, was director of the Planning Office of the Tufts-New England Medical Center in downtown Boston for 12 years. In 1972 he initiated and then directed a new graduate department of Urban and Environmental Policy at Tufts University. Since 1978 he has been Professor Emeritus in Environmental Planning there. In addition to continued involvement in his department he is active on a range of levels in conservation from the local to the international, including membership on IUCN's Commission on Environmental Planning.     

Dissolution of 226Radium from pipe-scale deposits in a public water supply

This study was undertaken to determine if dissolution of 226Radium from pipe-scale deposits contributes to enhanced waterborne 226Radium concentrations at the point of use. Water samples were collected from residential water customers of a small rural Iowa town. Sites were evenly divided between new and old water main connections. Daily samples were collected from the point-of-entry water. Point-of-use 226Radium concentrations ranged from 0.4 to 12.9 pCi L-1 (0.01 to 0.5 Bq L-1). The mean 226 Radium concentration for homes connected to old water mains was significantly higher than the mean 226Radium concentration of homes connected to new water mains, mean(standard deviation) equal 8.3(1.1) and 5.3(0.8) pCi L-1 [0.3(1.1) and 0.2(0.8) Bq L-1], respectively. 226Radium concentrations of the point-of-entry water ranged from 5.0 pCi L-1 to 10.3 pCi L-1 (0.2 Bq L-1 to 0.4 Bq L-1). This study indicates considerable variability of 226Radium exposure from drinking water among residents of the same water supply and has implications for regulatory compliance and exposure assessment in epidemiologic studies.