Adsorption of Pb,Cd, Cu,Zn, and Ni to titanium dioxide nanoparticles: effect of particle size,solid concentration,and exhaustion

Purpose  

Adsorption of metals (Pb, Cd, Cu, Ni, Zn) to TiO₂ nanoparticles and bulk particles was examined for use as a contaminant removal substrate as a function of particle size, sorbent concentration, and exhaustion.     

Degradation of bisphenol A using UV and UV/H2O2 processes

Bisphenol A (BPA; 4-[2-(4-hydroxyphenyl)propan-2-yl]phenol) is a substance typically used in the plastic industry. It is used in the production of epoxy resins, polycarbonate, or fire retardants or as a stabilizer and an antioxidant in numerous types of plastics. Bisphenol A is introduced into the environment via municipal and industrial wastewater. Because of its hydrophobic properties, BPA has the potential for sorption on activated sludge during the biological wastewater treatment processes. This study investigated the degradation of BPA by means of UV-radiation and in the UV/H2O2 process with the presence and absence of hydrocarbonate ions (HCO3(-)) as hydroxyl radicals (OH*) scavengers. The calculated value of quantum yield was equal to 0.18, and the value of BPA rate constant with hydroxyl radicals was equal to 3.3 x 10(9) M(-1) s(-1).     

Temporal trends in polychlorinated dibenzo-p-dioxins and dibenzofurans, dioxin-like PCBs, and polybrominated diphenyl ethers in Niagara river suspended sediments

Archived suspended sediment samples collected over the period 1980-2002 at Niagara-on-the-Lake in the Niagara river were analyzed to assess temporal trends in contaminants associated with historical industrial activities in the watershed (PCDDs/PCDFs, DLPCBs), compared to more modern industrial chemicals (PBDEs). The temporal trends for PCDDs/PCDFs and DLPCBs were generally similar, and showed a general trend toward decreasing concentrations, which was presumably due to implementation of control measures in the Niagara river watershed, including the remediation of hazardous waste facilities. The temporal trend in PBDEs contrasted with those of PCDDs/PCDFs and DLPCBs. Prior to 1988, PBDEs (sum of 16 congeners including deca-BDE) were generally detected at low-ppb concentrations, but showed a trend toward increasing concentrations over the period 1980-1988. After 1988, PBDE concentrations in the Niagara river showed a more rapidly increasing trend to a maximum of approximately 35 ng/g in 1995, with deca-BDE as the predominant congener detected. Samples collected over the period February 2003 to March 2004 at the head and mouth of the Niagara river were also analyzed for PBDEs; in all cases PBDE concentrations were higher at the mouth of the river at the outflow to Lake Ontario, indicating the Niagara river watershed is a source of PBDE contamination to Lake Ontario. However, PBDE concentrations in suspended sediments of the Niagara river were comparable to, or lower than, concentrations in bottom sediments in other industrialized/urbanized areas of the world. Based on these comparisons of global PBDE bottom sediment concentrations, the Niagara river watershed does not appear to be a significant local source of PBDEs to Lake Ontario, and concentrations in suspended sediments appear to be indicative of general PBDE contamination from a contamination of local, regional, and continental sources.     

Simultaneous optimization of dense non-aqueous phase liquid (DNAPL) source and contaminant plume remediation

A framework is developed for simultaneous, optimal design of groundwater contaminant source removal and plume remediation strategies. The framework allows for varying degrees of effort and cost to be dedicated to source removal versus plume remediation. We have accounted for the presence of physical heterogeneity in the DNAPL source, since source heterogeneity controls mass release into the plume and the efficiency of source removal efforts. We considered high and low estimates of capital and operating costs for chemical flushing removal of the source, since these are expected to vary form site to site. Using the lower chemical flushing cost estimates, it is found that the optimal allocation of funds to source removal or plume remediation is sensitive to the degree of heterogeneity in the source. When the time elapsed between the source release and the implementation of remediation was varied, it was found that, except for the longest elapsed time (50,000 days), a combination of partial source removal and plume remediation was most efficient. When first-order, dissolved contaminant degradation was allowed, source removal was found to be unnecessary for the cases where the degradation rate exceeded intermediate values of the first-order rate constant. Finally, it was found that source removal became more necessary as the degree of aquifer heterogeneity increased.     

Remote sensing-based neural network mapping of tsunami damage in Aceh, Indonesia

In addition to the loss of human life, the tsunami event of 26 December 2004 caused extensive damage to coastal areas. The scale of the disaster was such that remote sensing may be the only way to determine its effects on the landscape. This paper presents the results of a neural network-based mapping of part of the region of Aceh, Sumatra. Before-and-after satellite imagery, combined with a novel neural network methodology, enabled a characterisation of landscape change. The neural network technique used a threshold of acceptance for identification, in combination with a bootstrapped identification method for identifying problem pixels. Map analysis allowed identification of urban areas that were inaccessible by road, and which aid agencies could therefore only reach by air or sea. The methods used provide a rapid and effective mapping ability and would be a useful tool for aid agencies, insurance underwriters and environmental monitoring.     

Sequestration of aristolochic acids by the pipevine swallowtail, Battus philenor (L.): evidence and ecological implications

Summary. It has long been assumed that the North American pipevine swallowtail, Battus philenor (L.) (Papilionidae, Troidini), is protected from natural enemies by aristolochic acids sequestered from its Aristolochia food plants. This study confirmed that populations of B. philenor from Virginia and east Texas sequester these compounds. A comparison of the aristolochic acid profiles of the Virginia butterflies and their A. macrophylla food plants revealed several differences. The aristolochic acid fraction of the foliage was dominated by aristolochic acids I and II, whereas the insects had a much lower proportion of aristolochic acid II and contained, in addition, substantial amounts of aristolochic acids Ia and IVa, which were not detected in the plants. The eggs, larval integument, osmeterial glands, pupal cuticle, and adults (wings and bodies) all contained aristolochic acids. These findings help explain the abundant ecological data indicating that both immature and adult B. philenor are unpalatable and protected from natural enemies. Received 7 April 2000; accepted 31 May 2000     

Mass Mortality and Population Declines of Anurans at an Upland Site in Western Panama

I report an episode of anuran mortality and decline in the Reserva Forestal Fortuna, Chiriquí, Panama. The symptoms of decline at this site include population reductions, the presence of dead or dying adults, and tadpole abnormalities. Streamside anurans were abundant and diverse in 1993–1995, were restricted to a few streams in December 1996–January 1997, and then became rare throughout the reserve in July–August 1997. Between December 1996 and January 1997, I found 54 dead or dying frogs belonging to 10 species, and 12% of tadpoles had abnormalities of the oral disc. In July–August 1997 I monitored nine streams 37 times and captured only six individuals, whereas 13 terrestrial surveys along five trails resulted in 18 captured individuals. No dead or dying animals were found during those two months, but 11% of tadpoles had mouthpart abnormalities. Necropsies revealed that 18 of 18 dead anurans had a fungal infection of the skin; because this fungus was the only infection shared among all dead frogs, I suggest that it killed them and contributed to the decline of these populations. The presence of mouthpart abnormalities during a period of adult mortality suggests that this symptom may also be linked to the fungus infection. Clinical signs of decline in the anurans of Fortuna are similar to those found in the anurans of Monteverde and Las Tablas, Costa Rica, and I hypothesize that this pathogen was involved in the declines at all three sites.     

Clearing the smog? Public responses to air-quality information

Recent perspectives on public responses to environmental and risk communication have emphasised the interpretation, judgement and 'sense-making' that takes place when lay audiences receive information and advice. In this paper we consider the public reception given to air-quality information in the UK as one example of a government information and communication initiative. Drawing on elements of a wider research project undertaken in the city of Birmingham in the UK, involving a survey and in-depth interviews with members of the public, it examines the extent of awareness and use of information services, attitudes towards information and the role of information in behaviour change. The objective of the paper is to assess in practical terms the impact of air-quality information available through the media and other sources, as well as to provide empirical evidence with which to reflect on debates over the practice of environmental communication and the stimulation of pro-environmental behaviour. Conclusions are drawn which point to both problems with air quality information provision and the possibilities of more effective and appropriate interventions through local-level initiatives.     

Soil vs. canopy seed storage and plant species coexistence in species-rich Australian shrublands

The fire-prone shrublands of southwestern Australia are renowned for their high plant species diversity and prominence of canopy seed storage (serotiny). We compared species richness, abundance, and life history attributes for soil and canopy seed banks in relation to extant vegetation among four sites with different substrate conditions and high species turnover (50-80%) to identify whether this unusual community-level organization of seed storage might contribute to maintenance of high species richness. Soil seed bank (SSB) densities were low to moderate (233-1435 seeds/m2) compared with densities for other Mediterranean-type vegetation and were lowest for sites with highest canopy seed bank (CSB) species richness and lowest nutrient availability, but not richness or abundance of resprouters. Annuals were infrequent in the lowest nutrient sites, but there was no evidence that small SSB size was due to low seed inputs or a trade-off between seed production/storage and seed size in response to low nutrient availability. Sorensen's similarity between SSB and extant vegetation was 26-43% but increased to 54-57% when the CSB was included, representing levels higher than reported for most other ecosystems. Resprouting species were well represented in both the SSB and CSB, and there was no evidence for lower seed production in resprouters than in non-sprouters overall. The SSB and CSB held no species in common and were characterized by markedly different seed dispersal attributes, with winged or small seeds in the CSB and seeds dispersed by ants, birds, and wind (though none with wings) in the SSB. There was no evidence of spatial differentiation in the distribution of seeds of SSB species between vegetated and open microsites that might facilitate species coexistence, but most woody non-sprouters showed aggregation at scales of 1-2 m, implying limited seed dispersal. High similarity between overall seed bank (SSB + CSB) and extant species composition, high number of resprouting species, and seed dispersal processes before (SSB) and after fire (CSB) leading to differential spatial aggregation of post-fire recruits from the two seed bank types may buffer species composition against rapid change and provide a mechanism for maintaining species coexistence at the local scale.     

A meta-BACI approach for evaluating management intervention on chronic wasting disease in mule deer.

Advances in acquiring and analyzing the spatial attributes of data have greatly enhanced the potential utility of wildlife disease surveillance data for addressing problems of ecological or economic importance. We present an approach for using wildlife disease surveillance data to identify areas for (or of) intervention, to spatially delineate paired treatment and control areas, and then to analyze these nonrandomly selected sites in a meta-analysis framework via before-after-control impact (BACI) estimates of effect size. We apply these methods to evaluate the effectiveness of attempts to reduce chronic wasting disease (CWD) prevalence through intensive localized culling of mule deer (Odocoileus hemionus) in north-central Colorado, USA. Areas where surveillance data revealed high prevalence or case clusters were targeted by state wildlife management agency personnel for focal scale (on average <17 km2) culling, primarily via agency sharpshooters. Each area of sustained culling that we could also identify as unique by cluster analysis was considered a potential treatment area. Treatment areas, along with spatially paired control areas that we constructed post hoc in a case-control design (collectively called "management evaluation sites"), were then delineated using home range estimators. Using meta-BACI analysis of CWD prevalence data for all management evaluation sites, the mean effect size (change of prevalence on treatment areas minus change in prevalence on their paired control areas) was 0.03 (SE = 0.03); mean effect size on treatment areas was not greater than on paired control areas. Excluding cull samples from prevalence estimates or allowing for an equal or greater two-year lag in system responses to management did not change this outcome. We concluded that management benefits were not evident, although whether this represented true ineffectiveness or was a result of lack of data or insufficient duration of treatment could not be discerned. Based on our observations, we offer recommendations for designing a management experiment with 80% power to detect a 0.10 drop in prevalence over a 6-12-year period.