Production of polyhydroxyalkanoate during treatment of tomato cannery wastewater.

Polyhydroxyalkanoate (PHA) production was achieved using tomato cannery waste coupled with a mixed microbial culture during wastewater treatment. The two-stage PHA production process comprised a sequencing batch reactor (SBR), operating under a periodic feast-famine regime, to accomplish simultaneously wastewater treatment and selection of PHA-accumulating microbes, followed by a batch reactor for the production of PHA-rich biomass. The SBRs were efficient at removing soluble carbon (84%), ammonia (100%), and phosphorus (76%). Meanwhile, PHA-accumulating microbes were enriched under the SBR operating conditions, and PHA content on a cell-weight basis was within the range 7 to 11% in nonfiltered wastewater and 2 to 8% in filtered wastewater. Subsequently, batch studies were implemented with varying loading rates, ranging from 0.4 to 3.2 food-to-microorganism ratios. A maximum 20% PHA content on a cell-weight basis was obtained. Based on the experimental results, a PHA biosynthesis-degradation kinetic model was developed to (1) aid in the design of a pilot- or full-scale PHA production process coupled with wastewater treatment and (2) determine optimal conditions for harvest of PHA-rich biomass.     

Estimation of actinic flux and photolysis rate constant of NO2 from aerosol size data

Aerosol mass measurements made using Andersen cascade impactor at different locations in an urban area were used to study the variation in power-law exponent in the Junge-type number distribution. The discrete mass size data were inverted by modified Twomey algorithm to obtain continuous mass size distribution from which number distributions were derived. These were used for evaluating actinic fluxes and hence NO₂ photolysis rate constants employing a radiative transfer model with delta-Eddington approximation.Results of the spatial variation of Junge power-law exponent over the urban region are presented. The relative magnitude of photolysis rate constants over regions with differing aerosol emission characteristics are illustrated. Parametric studies indicated the importance of considering fractional elemental carbon content of the aerosols in the atmosphere. Results of a limited validation study of the model are also presented using quartz crystal microbalance impactor data at one of the sites.     

Carbonaceous aerosol in urban and rural European atmospheres: estimation of secondary organic carbon concentrations

Aerosol samples from urban, rural and coastal areas in Europe were analysed for carbonaceous content by a thermaloptical transmission method. The fraction of particulate organic carbon with a secondary origin in gas/particle conversion of volatile organic compounds was estimated from the minimum ratio between particulate organic and black carbon, which occurred during periods of reduced photochemical activity. Values calculated by this method ranged from a minimum of 17%, in Birmingham, UK, during winter, to a maximum of 78% at a rural coastal area, in Portugal, with air masses transported directly from the ocean. A clear seasonal dependence was observed at both rural and urban environments, with minimum secondary organic carbon production during winter.     

Hatching asynchrony reduces the duration, not the magnitude, of peak load in breeding green-rumped parrotlets (Forpus passerinus)

The peak load reduction hypothesis suggests that hatching asynchrony in altricial birds is adaptive because it reduces parental workload during the most energetically costly time in brood rearing. By staggering the ages of their offspring, parents may ensure that all nestlings do not reach maximum energy demand simultaneously. To test the hypothesis, we used the doubly labeled water technique to measure the energy expenditure of green-rumped parrotlets (Forpus passerinus) that reared experimentally manipulated synchronous and asynchronous broods. Peak metabolic rates of the two experimental groups did not differ, but parents of asynchronous broods metabolized significantly less energy than did parents of synchronous broods throughout the first half of the brood-rearing period. Our results suggest that hatching asynchrony in parrotlets substantially shortens the temporal duration of high brood energy demand, but does not reduce the magnitude of peak energy demand. Received: 16 July 1998 / Accepted after revision: 13 December 1998     

Atmospheric Change and the Diversity of Aquatic Invertebrates: Are We Missing the Boat?

The response of natural systems to atmospheric change may depend critically on species diversity and on the genetic diversity (variability) found within their respective populations. Yet, most surveys of aquatic invertebrates account for neither. This may be of particular concern for benthic populations in running waters because of the considerable variability and the fragmentary nature of these habitats (e.g. isolated watersheds). In such habitats, species with limited genetic variability and/or limited dispersal capabilities (genetically differentiated populations) may be unable to track rapid environmental change, and may be more susceptible to climatic perturbations. We present a conceptual framework to illustrate some of the potential problems of ignoring population genetics when considering the impacts of global atmospheric change. We then review a simple method to assess population genetic structure and we evaluate available data on the genetic structure of North American stream invertebrates. These data indicate that benthic taxa often consist of genetically differentiated local populations, or even previously unknown species. Accordingly, our limited knowledge of population structure among benthic invertebrates may result in the unwitting loss of genetic and/or species diversity. Enhanced taxonomic research incorporating molecular techniques is clearly warranted. Conservation strategies based on the preservation and remediation of a diversity of aquatic habitats are likely to be our best means of ensuring species and genetic diversity of invertebrate taxa.     

An experimental study of nightime air-pollutant transport over complex terrain in Athens

The Thriassion plain is a heavily industrialized area to the west of the Athens basin, separated from it by Mount Aegaleo, a 468-m high ridge about 15 km long. Three field experiments were performed to determine the possibility of air pollutant transport into the Athens basin. Sulphur hexafluoride (SF₆) was released from one of the stacks of the Hellenic Oil Refineries, situated in the eastern part of the Thriassion plain, together with several releases of tetroons. These experiments revealed two mechanisms of air mass transport from the Thriassion plain, a daytime mechanism, when the air mass is transported along the Mount Aegaleo ridge and through the passage between Mount Aegaleo and Mount Parnitha to the north, and a nighttime mechanism, when transport occurs over Mount Aegaleo. SF₆ was released only during the night and although in all three occassions it reached the western suburbs of Athens, it did so by different simultaneous mechanisms. Furthermore its advection-diffusion once in the basin showed large variability, whose cause was the details of the flow field as it developed under the influence of the thermal stratification. The experiments demonstrate the complexity of the diffusion of air pollutants in complex terrain and the influence of both the details of the flow field and the stratification in determining the local ground-level concentrations. They also point out the need for simultaneous modelling of both factors, for the correct computation of pollution levels.     

Sea lagoons in Hong Kong for the disposal of pulverized fuel ash (PFA)

The design of lagoons for the dewatering and retention of ash from pulverised coal burned in a power plant in Hong Kong is described. To reduce pollution of nearby oyster beds the sea water used to convey the ash as a slurry is decanted and returned to the power plant for discharge into deep water.     

Collaborative Science, Policy Development and Program Implementation in the Transboundary Georgia Basin/Puget Sound Ecosystem

The transboundary Georgia Basin Puget Sound ecosystem is situated in the southwest corner of British Columbia and northwest comer of Washington State. While bountiful and beautiful, this international region is facing significant threats to its marine and freshwater resources, air quality, habitats and species. These environmental challenges are compounded by rapid population growth and attendant uiban sprawl. As ecosystem stresses amplified and partnerships formed around possible solutions, it became increasingly clear that the shared sustainability challenges in the Georgia Basin and Puget Sound required shared solutions. Federal, state and provincial institutional arrangements were made between jurisdictions, which formalized small scale interest in transboundary management of this ecosystem. Formal agreements, however, can only do so much to further management of an ecosystem that spans international boarders. A transboundary regional research meeting, the 2003 GB/PS Research Conference, opened the doors for large-scale informal cross-boarder cooperation and management. In addition to cooperation, continued efforts to stem toxic pollution, contain urban growth, and protect and restore ecosystems, require a commitment from scientists, educators and policy makers to better integrate research and science with decision-making.Former Director of Planning and of Special Projects in the British Columbia Ministry of Municipal Affairs.