Performance comparison of tin oxide anodes to commercially available dimensionally stable anodes

Dimensionally stable anodes (DSAs) demonstrate potential for the electrochemical treatment of industrial waste streams and disinfection of effluent. Oxidation by laboratory-prepared tin oxide DSAs was compared with that of commercially available ruthenium oxide, iridium oxide, and mixed metal oxide DSAs, using hexanol as a probe molecule. The performance of the four anodes was similar in two-chamber reactors, in which the anode cell was separated from the cathode cell by a Nafion membrane, which allows transmission of current between the chambers, but not passage of chemical constituents. The anodes were then evaluated in single-cell reactors, which are more representative of potential treatment and disinfection applications. However, in the single-cell reactors, the tin oxide anodes were significantly more effective at oxidation and generated higher quality cyclic voltammograms than the other DSAs. These results suggest that tin oxide anodes have greater potential than the three commercially available DSAs tested for industrial waste stream treatment and effluent disinfection.     

Benthic Macroinvertebrate Responses to Increasing Levels of Cattle Grazing in Blue Ridge Mountain Streams, Virginia, USA

The relationship between benthic macroinvertebrate assemblages and cattle density was assessed from fall 2002 through spring 2004 in five small streams that represented a gradient of cattle grazing intensity. All study stream reaches were in pasture with no woody riparian vegetation, but varied in the intensity of cattle grazing (0 cattle ha⁻¹ at site 1 to 2.85 cattle ha⁻¹ at site 5). Regression analysis indicated highly significant and strong macroinvertebrate metric responses to cattle density during most sampling periods. The majority of metrics responded negatively to increased grazing, while a few (total taxa richness, number of sensitive taxa, and % collector filterers) increased along the gradient before declining at the most heavily grazed sites. Total number of sensitive taxa and % Coleoptera had the strongest relationship with cattle density throughout the study period. During some sampling periods, nearly 80% of the variation in these metrics was explained by cattle density. The elmid beetle, Oulimnius, had a particularly strong negative response to the grazing gradient. Study site groupings based on taxa composition, using detrended correspondence analysis (DCA), indicated that benthic samples collected from the reference site and light rotational grazing site were more similar in macroinvertebrate taxa composition than samples collected from the intermediate grazing and heavy grazing sites. Our findings demonstrate that biological integrity, as measured by benthic macroinvertebrate metrics and assemblage composition, is highly related to cattle density in small streams in the Blue Ridge mountains, Virginia, USA. This suggests that the degree of agricultural intensity should be given consideration in stream assessments, as well as land use planning and regulatory decisions.     

A survey of DNA methylation across social insect species, life stages, and castes reveals abundant and caste-associated methylation in a primitively social wasp

DNA methylation plays an important role in the epigenetic control of developmental and behavioral plasticity, with connections to the generation of striking phenotypic differences between castes (larger, reproductive queens and smaller, non-reproductive workers) in honeybees and ants. Here, we provide the first comparative investigation of caste- and life stage-associated DNA methylation in several species of bees and vespid wasps displaying different levels of social organization. Our results reveal moderate levels of DNA methylation in most bees and wasps, with no clear relationship to the level of sociality. Strikingly, primitively social Polistes dominula paper wasps show unusually high overall DNA methylation and caste-related differences in site-specific methylation. These results suggest DNA methylation may play a role in the regulation of behavioral and physiological differences in primitively social species with more flexible caste differences.     

Relation between PAH and black carbon contents in size fractions of Norwegian harbor sediments

Distributions of total organic carbon (TOC), black carbon (BC), and polycyclic aromatic hydrocarbons (PAH) were investigated in different particle size fractions for four Norwegian harbor sediments. The total PAH (16-EPA) concentrations ranged from 2 to 113 mg/kg dry weight with the greatest fraction of PAH mass in the sand fraction for three of the four sediments. TOC contents ranged from 0.84% to 14.2% and BC contents from 0.085% to 1.7%. This corresponds to organic carbon (OC = TOC - BC) contents in the range of 0.81-14% and BC:TOC ratios of 1.3-18.1%. PAH isomer ratios suggested that the PAH in all four sediments were of pyrogenic origin. Furthermore, stronger correlations between PAH versus BC (r2 = 0.85) than versus OC (r2 = 0.15) were found. For all size fractions and bulk sediments, the PAH-to-BC ratios for the total PAHs were on average 6+/-3 mg PAH/g BC. These results suggest that PAH distributions were dominated by the presence of BC, rather than OC. As sorption to BC is much stronger than sorption to OC, this may result in significantly lower dissolved concentrations of PAH than expected on the basis of organic carbon partitioning alone.     

Clusters of community exposure to coastal flooding hazards based on storm and sea level rise scenarios—implications for adaptation networks in the San Francisco Bay region

Regional Environmental Change - Sea level is projected to rise over the coming decades, further increasing the extent of flooding hazards in coastal communities. Efforts to address potential...     

In their words: How Detroit residents perceive the effects of their physical environment

Abstract

This article examines results from in-depth interviews conducted with parents of children with asthma living in an urban environment. We examine themes from the in-depth interviews related to participants' perceptions of the influence of their physical environment on their mental and physical health, and the actions that they take in an effort to protect their health within this context. The findings from this study suggest several implications for understanding the interface between the physical environment of urban communities and residents' health, as well as for the policy and practice of risk assessment strategies.     

Association of body mass with price of bushmeat in Nigeria and Cameroon

Spatially extensive patterns of bushmeat extraction (and the processes underlying these patterns) have not been explored. We used data from a large sample (n= 87) of bushmeat trading points in urban and rural localities in Nigeria and Cameroon to explore extraction patterns at a regional level. In 7,594 sample days, we observed 61,267 transactions involving whole carcasses. Rural and urban trading points differed in species for sale and in meat condition (fresh or smoked). Carcass price was principally associated with body mass, with little evidence that taxonomic group (primate, rodent, ungulate, or mammalian carnivore) affected price. Moreover, meat condition was not consistently associated with price. However, some individual species were more expensive throughout the region than would be expected for their size. Prices were weakly positively correlated with human settlement size and were highest in urban areas. Supply did not increase proportionally as human settlement size increased, such that per capita supply was significantly lower in urban centers than in rural areas. Policy options, including banning hunting of more vulnerable species (those that have low reproductive rates), may help to conserve some species consumed as bushmeat because carcass prices indicate that faster breeding, and therefore the more sustainable species, may be substituted and readily accepted by consumers.     

Mobilization of trace metals and inorganic compounds during resuspension of anoxic sediments from Trepangier Bayou, Louisiana

The release of trace metals (Mn, Ni, Co, Cu, Zn, Pb, and Cd) and inorganic compounds (As) from initially anoxic Trepangier Bayou sediments, Louisiana and the sources of the released metals were investigated. After 1 to 2 d aeration, significant amounts of trace metals (Mn, Zn, Cd, Ni, and Co) were released to the aqueous phase with increased acidity, primarily due to the oxidation of acid-volatile sulfide and ferrous iron and iron sulfide minerals. The addition of a bacterial inhibitor, NaN,, to the Trepangier sediment during resuspension inhibited metal release, suggesting that microbial catalysis can regulate metal mobilization during sediment resuspension. In a well buffered system, oxidation of iron sulfides alone did not appear to induce trace metal release. Moreover, when Trepangier sediment was resuspended in anoxic conditions at neutral pH, <1% of the trace metal content was released, whereas a significant release of metal was observed under acidic anoxic conditions. Although oxidation of iron sulfide minerals is an essential prerequisite for the release of Zn, Co, Cd, and Ni, carbonates and oxides also play a role. The trace metals and inorganic compounds investigated could be classified into three groups according to their release characteristics: (i) Mn, Zn, Cd, Ni, and Co; (ii) Fe, Pb, and As; and (iii) Cu. The groupings appeared to depend on the sources of compounds and their relative affinity, after oxidation, to iron oxyhydroxides or organic matter.