PM2.5: global progress in controlling the motor vehicle contribution

It is well established that ambient particles in the size range of 2.5 microns or less case a wide variety of adverse health effects. According to a recent study from the World Health Organization, in 2010 these effects resulted in approximately 3.2million premature deaths with vehicles being one of the significant contributors. Diesel vehicle particulate emissions which are virtually all smaller than 2.5 microns raise additional special concerns due to their carcinogenicity and high ratio of black carbon （BC） to organic carbon; black carbon has recently been found to be the second most important contributor to climate change after carbon dioxide. Other pollutants emitted by diesels and other vehicles such as the oxides of nitrogen and volatile organic compounds also contribute to ambient particulate matter smaller than 2.5 microns in size （PM2.5） after undergoing secondary transformations in the atrno- sphere. Technologies have dramatically reduce vehicle been developed that can emissions when clean, low sulfur fuels are available and these technologies are being phased in throughout the industrialized world resulting in a global decrease in particulate matter （PM） and BC emissions from vehicles. However the vehicle population is growing rapidly in the developing world, leading to increases in emissions in many countries. Unless these rapidly industrializing countries move to state of the art vehicles and clean fuels, global PM, BC and NOx emissions from road vehicles will start to turn up over the next 10 to 15 years.     

Living within constraints: irreversible chemical build-up and seasonal temperature-mediated die-off in a highly acidic (H2SO4) annual seaweed (Desmarestia viridis)

Seaweeds exhibit a number of adaptations to cope with strong selective pressures imposed by shallow marine environments. The exceptional ability of the annual, brown seaweed Desmarestia viridis, to produce and store high concentrations of sulfuric acid (H₂SO₄) in intracellular vacuoles, makes it a particularly compelling model for studies of causes and consequences of acid production in seaweeds. We used two laboratory experiments, as well as measurements of intracellular pH of sporophytes and sea salinity and temperature over an entire growth season at one site in Newfoundland and Labrador (Canada), to test hypotheses about effects of salinity and temperature on acid production and die-off in D. viridis. We show that the acid is continuously and irreversibly accumulated (resulting in an intracellular pH as low as 0.53) as the seaweed grows from recruit to adult (March–June) and that this build-up inevitably culminates into dramatic mass releases of acid and die-offs. Progressive, synchronous death among individuals is under the predominant control of sea temperature (death systematically occurred around 12 °C in both laboratory and field), which suggests the evolution of a life-history strategy in which death occurs at a time when individuals reach a size that may correspond to reproductive maturity. The seaweed exhibits a low tolerance to changes in salinity (death was inevitable below 29 psu), which likely imposes severe limitations on its distribution range throughout its existence as a sporophyte. Our findings suggest that major phenological events and survival in D. viridis are intimately linked to synergistic effects of oceanographic controls, which either impair the ability of the seaweed to retain the acid in its tissues (seasonal sea warming), or contribute to dissipating the acid that is released to the environment (wave and current action). They also provide novel insights into the ecophysiological and evolutionary constraints within which marine organisms adapt.     

Mapping risk for nest predation on a barrier island

Barrier islands and coastal beach systems provide nesting habitat for marine and estuarine turtles. Densely settled coastal areas may subsidize nest predators. Our purpose was to inform conservation by providing a greater understanding of habitat-based risk factors for nest predation, for an estuarine turtle. We expected that habitat conditions at predated nests would differ from random locations at two spatial extents. We developed and validated an island-wide model for the distribution of predated Diamondback terrapin nests using locations of 198 predated nests collected during exhaustive searches at Fisherman Island National Wildlife Refuge, USA. We used aerial photographs to identify all areas of possible nesting habitat and searched each and surrounding environments for nests, collecting location and random-point microhabitat data. We built models for the probability of finding a predated nest using an equal number of random points and validated them with a reserve set (N?=?67). Five variables in 9 a priori models were used and the best selected model (AIC weight 0.98) reflected positive associations with sand patches near marshes and roadways. Model validation had an average capture rate of predated nests of 84.14 % (26.17–97.38 %, Q1 77.53 %, median 88.07 %, Q3 95.08 %). Microhabitat selection results suggest that nests placed at the edges of sand patches adjacent to upland shrub/forest and marsh systems are vulnerable to predation. Forests and marshes provide cover and alternative resources for predators and roadways provide access; a suggestion is to focus nest protection efforts on the edges of dunes, near dense vegetation and roads.     

Radio (<Superscript>14</Superscript>C)- and fluorescent-doubly labeled silica nanoparticles for biological and environmental toxicity assessment

A new and efficient synthetic route to fluorescent and ¹⁴C-double-labeled silica-based nanoparticles (NPs) is described. The synthesis has been carried out using the “oil-in-water” micro-emulsion technique. Fluorescent and radioactive labeling have been achieved entrapping labeled poly(ethylene glycol) (PEG) molecules in the NPs. The produced particles have been analyzed by means of scanning electron microscopy, photon correlation spectroscopy, confocal microscopy, scintillation counting and oxidation/combustion experiments. Fluorescence quenching experiments confirm that the label is entrapped in the particles. The results presented suggest that the silica matrix does not block the β-radiations emitted from the labeled PEG molecules entrapped in the NPs.     

Phototransformation of oxamyl in aqueous solution

The photolysis of the N methyl carbamate pesticide oxamyl (Z isomer) has been studied in aqueous solution. Continuous irradiation at mainly λ = 254 and λ > 290 nm has been performed to characterise the pesticide photochemical behaviour in water at pH = 6.0. Upon monochromatic irradiation, the phototransformation quantum yield was evaluated to be roughly constant, with a value of 0.54 ± 0.08. Upon polychromatic irradiation, a photochemical efficiency has been estimated to be 0.5 ± 0.1 by using phenol as a reference compound. Two main degradation products were identified: the isomer (E) of oxamyl and the nitrile derivative (N,N-dimethyl-2-nitrilo-acetamide). The photolysis of the oximino derivative, an hydrolysis product of oxamyl, was also studied. Upon irradiation at 254 nm, the quantum yield of phototransformation was found to be 0.28. A unique photoproduct was detected: it corresponds to the (E) isomer of the oximino derivative. For prolonged irradiations, a photostationary state was reached between the oximino and its (E) isomer. From kinetics data, the removal of oxamyl and of the oximino derivative during a UV disinfection step used in drinking water production was calculated to be 45 and 13%, respectively.     

Regeneration status of mangrove forests in Mida Creek,Kenya: a compromised or secured future?

The structure and regeneration patterns of Mida Creek mangrove vegetation were studied along belt transects at 2 forest sites of Mida Creek (3 degrees 20'S, 40 degrees 00'E): Uyombo and Kirepwe. Based on the species importance values, the dominant mangrove tree species in Mida were Ceriops tagal (Perr.) C. B. Robinson and Rhizophora mucronata Lamk. Tree density varied from 1197 trees ha(-1) at Kirepwe to 1585 trees ha(-1) at Uyombo and mean tree height was higher at the former site compared to the latter. The size-class structure at both localities of Mida showed the presence of more small trees than large ones. Spatial distribution pattern of adults and juveniles varied greatly between sites and they showed a close to uniform pattern (Morisita's Index I0 < 1) for trees, but a tendency to random distribution (I0 = 1) for juveniles. The present paper shows that unmanaged but exploited mangroves do not necessarily disappear, but change qualitatively from locally preferred R. mucronata to the less preferred C. tagal. Whereas the effects of this change on the ecological function of the mangrove cannot be estimated yet, the economical function of the mangrove has evidently weakened.     

Prioritizing Pacific Salmon Stocks for Conservation

Over 300 native stocks of Pacific salmon, steelhead, and coastal cutthroat trout (Oncorhynchus spp.) are at risk of extinction in the Pacific Northwest. With only limited resources available for conservation and recovery, prioritization of these stocks may become necessary if meaningful measures are to be implemented. We propose criteria by which prioritization may be guided. First, we rank stocks for risk of extinction, either by population viability analysis or by a set of surrogate measures. Then we rank stocks for biological consequences of extinction, using sets of questions designed to establish the genetic and evolutionary consequences and the ecological consequences if a stock were to become extinct. Together, these rankings allow stocks to be prioritized for a range of possible actions, with those stocks at highest risk and bearing the greatest biological consequences of extinction receiving attention first. Application of the prioritization process to 20 Pacific anadromous salmonid stocks worked as intended, although data limitations are considerable. The process is most likely to work successfully when applied to many stocks on which data exist, when several experts carry out the prioritization, and when the results are peer reviewed.     

Impact of Lime and Ash Applications on Soil Solution Chemistry of an Acidified Podzolic Soil

Soil solution samples were taken from two sites (Horröd and Hasslöv) in the south part of Sweden to evaluate how soil solution chemistry responded to different treatmentswith dolomite and wood ash. At Horröd, samples were taken four years after application of wood ash, 4.28 ton ha^-1 and dolomite, 3.25 ton ha^-1. At Hasslöv dolomite, 3.45 ton ha^-1 and 8.75 ton ha^-1 was applied and samples were taken 15 yr later. It was found that treatment with dolomite at one site (Hasslöv) resulted in higher pH values (<2 pH units) and higher nitrification. It was also found at this site that the total Al and the inorganic Al concentrations decreased with dolomite treatment. The Ca, Mg, DOC, Fe, SO₄ ^2- and Cl^- concentrations, mainly in the topsoil, were found to be higher at both sites, following dolomite treatment; Ca and Mg concentrations were 2–8 times higher (<820 M) than in controls (<70 M). Wood ash was found to have less impact. The PO₄ concentration in the O2 horizon at Hasslöv decreased due to dolomite-treatment. ANOVA (Analyse of Variance) and PLS (Partial Least Square) were used to evaluate the data from the two sites.     

Phenanthrene sorption to structurally modified humic acids

Several studies emphasize the importance of soil organic matter characteristics in hydrophobic contaminant sorption and outline the strong dependence of sorption on organic matter aromaticity. In this study, the role of organic matter aromaticity in phenanthrene sorption was investigated using humic acids (HAs) from compost, peat, and soil that were structurally modified by bleaching, hydrolysis, oximation, and subcritical water extraction. The HAs were characterized with cross polarization magic angle spinning carbon-13 nuclear magnetic resonance (CPMAS 13C NMR) spectroscopy and used in batch equilibrations with phenanthrene. Bleaching substantially reduced the aromaticity of the samples whereas the other treatments increased the relative aromaticity. Phenanthrene sorption increased, even though there was a substantial reduction in sorbent aromaticity with some samples. The HAs that exhibited comparable CPMAS 13C NMR spectra and aromaticity did not behave similarly with respect to phenanthrene sorption. When the sorption data (K(oc) values) were correlated to sample aromaticity, the correlation coefficients (r2) did not exceed 0.39. Comparisons with the atomic H to C ratio provided slightly better r2 values (up to 0.54). This study demonstrates that macroscopic sorbent characteristics could not explain the observed phenanthrene sorption coefficients, aliphatic structural components of HAs can contribute appreciably to phenanthrene sorption, and organic matter physical conformation may regulate access to organic matter structures. Therefore, the use of only macroscopic sorbent properties, such as aromaticity, to predict and rationalize sorption values cannot solely be used to explain the behavior of organic contaminants in soil environments.     

Effects of oxide coating and selected cations on nitrate reduction by iron metal

Under anoxic conditions, zerovalent iron (Fe(0)) reduces nitrate to ammonium and magnetite (Fe3O4) is produced at near-neutral pH. Nitrate removal was most rapid at low pH (2-4); however, the formation of a black oxide film at pH 5 to 8 temporarily halted or slowed the reaction unless the system was augmented with Fe(2+), Cu(2+), or Al(3+). Bathing the corroding Fe(0) in a Fe(2+) solution greatly enhanced nitrate reduction at near-neutral pH and coincided with the formation of a black precipitate. X-ray diffractometry and scanning electron microscopy confirmed that both the black precipitate and black oxide coating on the iron surface were magnetite. In this system, ferrous iron was determined to be a partial contributor to nitrate removal, but nitrate reduction was not observed in the absence of Fe(0). Nitrate removal was also enhanced by augmenting the Fe(0)-H2O system with Fe(3+), Cu(2+), or Al(3+) but not Ca(2+), Mg(2+), or Zn(2+). Our research indicates that a magnetite coating is not a hindrance to nitrate reduction by Fe(0), provided sufficient aqueous Fe(2+) is present in the system.