Abstract  Salmonella enterica serovar Typhimurium is a Gram-negative bacterium with a flexible respiratory capability. Under anaerobic conditions, S. enterica can utilize a range of terminal electron acceptors, including selenate, to sustain respiratory electron transport. The S. enterica selenate reductase is a membrane-bound enzyme encoded by the ynfEFGH-dmsD operon. The active enzyme is predicted to comprise at least three subunits where YnfE is a molybdenum-containing catalytic subunit. The YnfE protein is synthesized with an N-terminal twin-arginine signal peptide and biosynthesis of the enzyme is coordinated by a signal peptide binding chaperone called DmsD. In this work, the interaction between S. enterica DmsD and the YnfE signal peptide has been studied by chemical crosslinking. These experiments were complemented by genetic approaches, which identified the DmsD binding epitope within the YnfE signal peptide. YnfE signal peptide residues L24 and A28 were shown to be important for assembly of an active selenate reductase. Conversely, a random genetic screen identified the DmsD V16 residue as being important for signal peptide recognition and selenate reductase assembly.

Abstract  The article presents results of laboratory tests of removing boron and arsenium from non-ideal solutions using double-layered magnesium/aluminium hydroxides (Mg/Al Double-Layered Hydroxide – DLH) produced with nitrate-chloride method. In research, wastewater from an installation for flue gas desulfurization was examined. Double-layered hydroxides are perfect absorbents for anionic compounds. The research proved high effectiveness of preparation with reference to arsenium, as well as confirmed the effect of presence of sulfatic and arsenate ions on the effectiveness of boron removal. On the basis of research on absorption kinetics a theoretical dose of DLH/NO3-Cl/M preparation was calculated and compared with a dose that ensures emimination of boron below the limit standarized by the national regulations. Application of double-layered magnesium/aluminium hydroxides for boron elimination from industrial wastewater requires significantly higher doses of preparation than those calculated in model investigations. It is due to the priority of removal of multivalent ions, such as sulfatic, arsenate or phosphate ions, by DLH/NO3-Cl/M.

Abstract  Ammonia (NH3)-oxidizing bacteria (AOB) derive total energy for life from the multi-electron oxidation of NH3 to nitrite (NO2-). One obligate intermediate of this metabolism is hydroxylamine (NH2OH), which can be oxidized to the potent greenhouse agent nitrous oxide (N2O) by the AOB enzyme cytochrome (cyt) P460. We have now spectroscopically characterized a 6-coordinate (6c) {FeNO}7 intermediate on the NH2OH oxidation pathway of cyt P460. This species has two fates: it can either be oxidized to the {FeNO}6 that then undergoes attack by NH2OH to ultimately generate N2O, or it can lose its axial His ligand, thus generating a stable, off-pathway 5-coordinate (5c) {FeNO}7 species. We show that the wild type (WT) cyt P460 exhibits a slow nitric oxide (NO)-independent conversion (kHis-off = 2.90 × 10-3 s-1), whereas a cross-link-deficient Lys70Tyr cyt P460 mutant protein underwent His dissociation via both a NO-independent (kHis-off = 3.8 × 10-4 s-1) and a NO-dependent pathway [kHis-off(NO) = 790 M-1 s-1]. Eyring analyses of the NO-independent pathways for these two proteins revealed a significantly larger (ca. 27 cal mol-1 K-1) activation entropy (ΔS‡) in the cross-link-deficient mutant. Our results suggest that the Lys-heme cross-link confers rigidity to the positioning of the heme P460 cofactor to avoid the fast NO-dependent His dissociation pathway and subsequent formation of the off-pathway 5c {FeNO}7 species. The relevance of these findings to NO signaling proteins such as heme-nitric oxide/oxygen binding (H-NOX) is also discussed.

Abstract  While eutrophication is often attributed to contemporary nutrient pollution, there is growing evidence that past practices, like the accumulation of legacy sediment behind historic milldams, are also important. Given their prevalence, there is a critical need to understand how N flows through, and is retained in, legacy sediments to improve predictions and management of N transport from uplands to streams in the context of climatic variability and land-use change. Our goal was to determine how nitrate (NO3-) is cycled through the soil of a legacy-sediment-strewn stream before and after soil drying. We extracted 10.16 cm radius intact soil columns that extended 30 cm into each of the three significant soil horizons at Big Spring Run (BSR) in Lancaster, Pennsylvania: surface legacy sediment characterized by a newly developing mineral A horizon soil, mid-layer legacy sediment consisting of mineral B horizon soil and a dark, organic-rich, buried relict A horizon soil. Columns were first preincubated at field capacity and then isotopically labeled nitrate ((NO3-)-N-15) was added and allowed to drain to estimate retention. The columns were then air-dried and subsequently rewet with N-free water and allowed to drain to quantify the drought-induced loss of (NO3-)-N-15 from the different horizons. We found the highest initial N-15 retention in the mid-layer legacy sediment (17 +/- 4 %) and buried relict A soil (14 +/- 3 %) horizons, with significantly lower retention in the surface legacy sediment (6 +/- 1 %) horizon. As expected, rewetting dry soil resulted in N-15 losses in all horizons, with the greatest losses in the buried relict A horizon soil, followed by the mid-layer legacy sediment and surface legacy sediment horizons. The N-15 remaining in the soil following the post-drought leaching was highest in the mid-layer legacy sediment, intermediate in the surface legacy sediment, and lowest in the buried relict A horizon soil. Fluctuations in the water table at BSR which affect saturation of the buried relict A horizon soil could lead to great loses of NO3- from the soil, while vertical flow through the legacy-sediment-rich soil profile that originates in the surface has the potential to retain more NO3-. Restoration that seeks to reconnect the groundwater and surface water, which will decrease the number of drying-rewetting events imposed on the relict A horizon soils, could initially lead to increased losses of NO3- to nearby stream waters.

Abstract  Large-scale cyanobacteria bloom occurred in the summer of 2014 in the Guishi Reservoir that is an important drinking water source for Hezhou City. The dynamic change regularity, external pollution sources, and the phytoplankton community characteristics during the bloom were investigated to evaluate the eutrophication in the reservoir and to present effective prevention and control measures. The results showed that nitrogen and phosphorus concentrations increased year by year; water quality on some sites has been out of class II of national water quality standards; and the main pollution source was the agricultural non-point sources. Phytoplankton cell density was in the range of 8.60×106-5.36×108 cells·L-1 and chlorophyll a concentrations reached 74.48 μg·L-1 during the bloom. The dominant species was Microcystis wesenbergii whose density reached 5.36×108 cells·L-1. The cell density decreased over time and concentrated on the surface and at the depth of 2 m underwater. The total phytoplankton cell density was strongly correlated to total phosphorus, total nitrogen, nitrate nitrogen, and the permanganate index, and was inversely correlated to transparency. The water in the Guishi Reservoir was not polluted by microcystic toxins. Moreover, Guishi Reservoir is in a meso-eutrophic state; therefore, the prevention and control of the cyanobacteria bloom should focus on weather conditions and on reducing the input of nitrogen and phosphorus to keep the nutrient levels low. © 2017, Science Press. All right reserved.

Abstract  We analyzed a coal tar polluted aquifer of a former gasworks site in Thuringia (Germany) for the presence and function of aromatic compound-degrading bacteria (ACDB) by 16S rRNA Illumina sequencing, bamA clone library sequencing and cultivation attempts. The relative abundance of ACDB was highest close to the source of contamination. Up to 44% of total 16S rRNA sequences were affiliated to ACDB including genera such as Azoarcus, Georgfuchsia, Rhodoferax, Sulfuritalea (all Betaproteobacteria) and Pelotomaculum (Firmicutes). Sequencing of bamA, a functional gene marker for the anaerobic benzoyl-CoA pathway, allowed further insights into electron-accepting processes in the aquifer: bamA sequences of mainly nitrate-reducing Betaproteobacteria were abundant in all groundwater samples, whereas an additional sulfate-reducing and/or fermenting microbial community (Deltaproteobacteria, Firmicutes) was restricted to a highly contaminated, sulfate-depleted groundwater sampling well. By conducting growth experiments with groundwater as inoculum and nitrate as electron acceptor, organisms related to Azoarcus spp. were identified as key players in the degradation of toluene and ethylbenzene. An organism highly related to Georgfuchsia toluolica G5G6 was enriched with p-xylene, a particularly recalcitrant compound. The anaerobic degradation of p-xylene requires a metabolic trait that was not described for members of the genus Georgfuchsia before. In line with this, we were able to identify a putative 4-methylbenzoyl-CoA reductase gene cluster in the respective enrichment culture, which is possibly involved in the anaerobic degradation of p-xylene.

Abstract  The Cry1Ac toxin from Bacillus thuringiensis is used commercially as a bio-insecticide and is expressed in transgenic plants that are used for human and animal consumption. Although it was originally considered innocuous for mammals, the Cry1Ac toxin is not inert and has the ability to induce mucosal and systemic immunogenicity. Herein, we examined whether the Cry1Ac toxin promotes macrophage activation and explored the signalling pathways that may mediate this effect. Treatment of primary and RAW264.7 macrophages with the Cry1Ac toxin resulted in upregulation of the costimulatory molecules CD80, CD86 and ICOS-L and enhanced production of nitric oxide, the chemokine MCP-1 and the proinflammatory cytokines TNF-α and IL-6. Remarkably, the Cry1Ac toxin induced phosphorylation of the mitogen-activated protein kinases (MAPKs) ERK1/2, JNK and p38 and promoted nuclear translocation of nuclear factor-kappa B (NF-κB) p50 and p65. p38 and ERK1/2 MAPKs were involved in this effect, as indicated by the Cry1Ac-induced upregulation of CD80 and IL-6 and TNF-α abrogation by the p38 MAPK inhibitor SB203580. Furthermore, treatment the MEK1/2 kinase inhibitor PD98059 blocked increases in MCP-1 secretion and augmented Cry1Ac-induced ICOS-L upregulation. These data demonstrate the capacity of the Cry1Ac toxin to induce macrophage activation via the MAPK and NF-κB pathways.

Abstract  Study of uranium interstitial compositions of non-stoichiometric oxides UO2+x (x ∈ 0.1-0.02) in gas and condense phases has been presented, using various soft-ionization mass spectrometric methods such as ESI-, APCI-, and MALDI-MS at a wide dynamic temperature gradient (∈ 25-300 °C). Linearly polarized vibrational spectroscopy has been utilized in order to assign unambiguously, the vibrational frequencies of uranium non-stoichiometric oxides. Experimental design has involved xUO2.66·yUO2.33, xUO2.66·yUO2.33/SiO2, xUO2.66·yUO2.33/SiO2 (NaOH) and SiO2/x'NaOH·y'UO2(NO3)2·6H2O, multicomponent systems (x = 1, y ∈ 0.1-1.0 and x' = 1, y' ∈ 0.1-0.6) as well as phase transitions UO2(NO3)2·6H2O → {U4O9(UO2.25)} → U3O7(UO2.33) → U3O8(UO2.66) → {UO3}, thus ensuring a maximal representativeness to real environmental conditions, where diverse chemical, geochemical and biochemical reactions, including complexation and sorption onto minerals have occurred. Experimental factors such as UV-irradiation, pH, temperature, concentration levels, solvent types and ion strength have been taken into consideration, too. As far as uranium speciation represents a challenging analytical task in terms of chemical identification diverse coordination species, mechanistic aspects relating incorporation of oxygen into UO 2+x form the shown full methods validation significantly impacts the field of environmental radioanalytical chemistry. UO2 is the most commonly used fuel in nuclear reactors around the globe; however, a large non-stoichiometric range ∈ UO1.65-UO2.25 has occurred due to radiolysis of water on UO2 surface yielding to H2O2, OH(·), and more. Each of those compositions has different oxygen diffusion. And in this respect enormous effort has been concentrated to study the potential impact of hazardous radionuclide on the environment, encompassing from the reprocessing to the disposal stages of the fuel waste, including the waste itself, the processes in the waste containers, the clay around the containers, and geological processes. In a broader sense, thereby, this study contributes to field of environmental analysis highlighting the great ability of various soft-ionization MS methods, particularly, MALDI-MS one, for direct assay of complex multicomponent heterogeneous mixtures at fmol-attomol concentration ranges, along with it the great instrumental features allowing, not only meaningful quantitative, but also structural information of the analytes, thus making the method indispensable for environmental speciation of radionuclides, generally.

Abstract  Soil microorganisms play important roles in nitrogen cycling within forest ecosystems. Current research has revealed that a wider variety of microorganisms, with unexpected diversity in their functions and phylogenies, are involved in the nitrogen cycle than previously thought, including nitrogen-fixing bacteria, ammonia-oxidizing bacteria and archaea, heterotrophic nitrifying microorganisms, and anammox bacteria, as well as denitrifying bacteria, archaea, and fungi. However, the vast majority of this research has been focused in temperate regions, and relatively little is known regarding the ecology of nitrogen-cycling microorganisms within tropical and subtropical ecosystems. Tropical forests are characterized by relatively high precipitation, low annual temperature fluctuation, high heterogeneity in plant diversity, large amounts of plant litter, and unique soil chemistry. For these reasons, regulation of the nitrogen cycle in tropical forests may be very different from that of temperate ecosystems. This is of great importance because of growing concerns regarding the effect of land use change and chronic elevated nitrogen deposition on nitrogen-cycling processes in tropical forests. In the context of global change, it is crucial to understand how environmental factors and land use changes in tropical ecosystems influence the composition, abundance and activity of key players in the nitrogen cycle. In this review, we synthesize the limited currently available information regarding the microbial communities involved in nitrogen fixation, nitrification and denitrification, to provide deeper insight into the mechanisms regulating nitrogen cycling in tropical forest ecosystems. We also highlight the large gaps in our understanding of microbially mediated nitrogen processes in tropical forest soils and identify important areas for future research.

Abstract  We have discovered an unusual new chemiluminescence (CL) in the title system, which is different from other known CL by unusual combination of various in nature emitters, namely, electronically excited state of the Ce-3+* ion (lambda max=335 nm), singlet oxygen O-1(2) (emission near 1270 nm) and its dimer (O-1(2))(2) (lambda(max)=490, 645, 715 nm). The Ce3+* ions and oxygen emitters O-1(2) and (O-1(2))(2) are generated in the reaction of Ce4+ with water and hydrogen peroxide, respectively. CL is generated only in a heterogeneous system "(NH4)(2)Ce(NO3)(6)-C6H6-H2O" and completely absent in a homogeneous solution (NH4)2Ce(NO3)(6) in water containing benzene. This is due to the fact that the redox processes and CL in the "(NH4)(2)Ce(NO3)(6)-C6H6-H2O" system are induced by active surface of the (NH4)(2)Ce(NO3)(6) crystals. It is through the action of the active surface of the (NH4)(2)Ce(NO3)(6) crystals is carried out population of such a high energy level of 5d(1) excited state of Ce3+* ion (lambda(max)=353 nm, 3.7 eV). Discovered CL is the first example of an experimental registration of the Ce3+* ion emission in a chemical reaction, because formation of Ce3+* ion previously assumed to be in a great many works on the study of CL in reactions of Ce4+ compounds with various reducing agents, including the reaction with water, initiated by light or catalysts. Possible mechanism generation of new CL in the system under study has been proposed in the paper. (C) 2016 Elsevier B.V. All rights reserved

Abstract  It is well-known that the health effects of PM increase as particle size decreases: particularly, great concern has risen on the role of UltraFine Particles (UFPs). Starting from the knowledge that the main fraction of atmospheric aerosol in Rome is characterized by significant levels of PM2.5 (almost 75% of PM10 fraction is PM2.5), the paper is focused on submicron particles in such great urban area. The daytime/nighttime, work-/weekdays and cold/hot seasonal trends of submicron particles will be investigated and discussed along with NOx and total PAH drifts demonstrating the primary origin of UFPs from combustion processes. Furthermore, moving from these data, the total dose of submicron particles deposited in the respiratory system (i.e., head, tracheobronchial and alveolar regions in different lung lobes) has been estimated. Dosimeter estimates were performed with the Multiple-Path Particle Dosimetry model (MPPD v.2.1). The paper discusses the aerosol doses deposited in the respiratory system of individuals exposed in proximity of traffic. During traffic peak hours, about 6.6 × 10(10) particles are deposited into the respiratory system. Such dose is almost entirely made of UFPs. According to the greater dose estimated, right lung lobes are expected to be more susceptible to respiratory pathologies than left lobes.

Abstract  Currently, there is a lack of knowledge about GHG emissions, specifically N2O and CH4, in subtropical coastal freshwater wetland and mangroves in the southern hemisphere. In this study, we quantified the gas fluxes and substrate availability in a subtropical coastal wetland off the coast of southeast Queensland, Australia over a complete wet-dry seasonal cycle. Sites were selected along a salinity gradient ranging from marine (34 psu) in a mangrove forest to freshwater (0.05 psu) wetland, encompassing the range of tidal influence. Fluxes were quantified for CH4 (range -0.4-483 mg C-CH4 h(-1) m(-2)) and N2O (-5.5-126.4 mu g N-N2O h(-1) m(-2)), with the system acting as an overall source for CH4 and N2O (mean N2O and CH4 fluxes: 52.8 mu g N-N2O h(-1) m(-2) and 48.7 mg C-CH4 h(-1) m(-2), respectively). Significantly higher N2O fluxes were measured during the summer months (summer mean 64.2 +/- 22.2 mu g N-N2O h(-1) m(-2); winter mean 33.1 +/- 24.4 A mu g N-N2O h(-1) m(-2)) but not CH4 fluxes (summer mean 30.2 +/- 81.1 mg C-CH4 h(-1) m(-2); winter mean 37.4 +/- 79.6 mg C-CH4 h(-1) m(-2)). The changes with season are primarily driven by temperature and precipitation controls on the dissolved inorganic nitrogen (DIN) concentration. A significant spatial pattern was observed based on location within the study site, with highest fluxes observed in the freshwater tidal wetland and decreasing through the mangrove forest. The dissolved organic carbon (DOC) varied throughout the landscape and was correlated with higher CH4 fluxes, but this was a nonlinear trend. DIN availability was dominated by N-NH4 and correlated to changes in N2O fluxes throughout the landscape. Overall, we did not observe linear relationships between CH4 and N2O fluxes and salinity, oxygen or substrate availability along the fresh-marine continuum, suggesting that this ecosystem is a mosaic of processes and responses to environmental changes.

Abstract  The 2011 Richardson wildland mega-fire in the Athabasca Oil Sands Region (AOSR) in northern Alberta, Canada had large effects on air quality. At a receptor site in the center of the AOSR ambient PM2.5, O3, NO, NO2, SO2, NH3, HONO, HNO3, NH4(+) and NO3(-) were measured during the April-August 2011 period. Concentrations of NH3, HNO3, NO2, SO2 and O3 were also monitored across the AOSR with passive samplers, providing monthly summer and bi-monthly winter average values in 2010, 2011 and 2012. During the fire, hourly PM2.5 concentrations >450μgm(-3) were measured at the AMS 1 receptor site. The 24-h National Ambient Air Quality Standard (NAAQS) of 35μgm(-3) and the Canada Wide Standard (CWS) of 30μgm(-3) were exceeded on 13days in May and 7days in June. During the fire emission periods, sharp increases in NH3, HONO, HNO3, NH4(+), NO3(-) and total inorganic reactive N concentrations occurred, all closely correlated with the PM2.5 changes. There were large differences in the relative contribution of various N compounds to total inorganic N between the no-fire emission and fire emission periods. While in the absence of fires NO and NO2 dominated, their relative contribution during the fires was ~2 fold smaller, mainly due to increased NH3, NH4(+) and NO3(-). Concentrations of HONO and HNO3 also greatly increased during the fires, but their contribution to the total inorganic N pool was relatively small. Elevated NH3 and HNO3 concentrations affected large areas of northern Alberta during the Richardson Fire. While NH3 and HNO3 concentrations were not at levels considered toxic to plants, these gases contributed significantly to atmospheric N deposition. Generally, no significant changes in O3 and SO2 concentrations were detected and their ambient concentrations were below levels harmful to human health or sensitive vegetation.

Abstract  This study aimed to investigate the degradation of triclosan (TCS) in the presence of p-aminobenzoic acid (PABA) under simulated sunlight irradiation (λ ≥ 290 nm). The effect of PABA concentration, pH, dissolved organic matter (DOM), and DOM-hydrolytic Fe(III) species complexes on the photodegradation of TCS in the presence of PABA (TCS-PABA) was also studied. The photolysis of TCS-PABA obeyed pseudo-first-order kinetics well, and the degradation of TCS-PABA enhanced with increasing solution pH (from 3.0 to 11.0). The presence of PABA inhibited the degradation of TCS-PABA, and the weakest inhibitory effect was observed while the concentration of PABA was 5 mg L(-1). The addition of DOM (Suwannee River fulvic acid standard I [SRFA], Suwannee River HA standard II [SRHA], and Suwannee River natural organic matter [SRNOM]) showed different inhibition effects on TCS-PABA degradation. However, higher Fe(III) concentration at the DOM concentration of 5 mg L(-1) could favor the formation of DOM-hydrolytic Fe(III) species complexes, further accelerating the degradation of TCS-PABA. In comparison with deionized water (DI water), TCS-PABA could be better photodegraded in river water nearby the effluent of a wastewater treatment plant. This study provides useful information for understanding the natural behavior of TCS in the presence of other organic contaminants.

Abstract  Nitric oxide (NO), is arguably one of the most important small signaling molecules in biological systems. It regulates various biological responses in both physiological and pathological conditions, often time producing seemingly contradictory results. The details of the effects of NO are highly dependent on the level of NO that cells experience and the temporal aspect of when and how long cells are exposed to NO. Herein, we present a novel measurement system (CellNO trap) that allows real-time NO measurement via chemiluminescence detection from general adhesive cultured cells using standard cell culture media and reagents that does not perturb the cells under investigation. Highly controlled light-initiated NO releasing polymer SNAP-PDMS was used to characterize and validate the quantitative data nature of the device. The NO generation profile from the macrophage cell-line RAW264.7 stimulated by 100ng/ml LPS and 10ng/ml IFN-γ was recorded. Measured maximum NO flux from RAW264.7 varied between around 2.5-9pmol/10(6)cell/s under 100ng/ml LPS and 10ng/ml IFN-γ stimulation, and 24h cumulative NO varied between 157 and 406 nmol/10(6)cell depending on different culture conditions, indicating the conventional report of an average flux or maximum flux is not sufficient to represent the dynamic characters of NO. LPS and IFN-γ's synergistic effect to RAW264.7 NO generation was also directly observed with the CellNO trap. The real-time effect on the NO generation from RAW264.7 following the addition of arginine, nor-NOHA and L-NAME to the cultured cells is presented. There is great potential to further our understanding of the role NO plays in normal and pathological conditions clearly understanding the dynamic production of NO in response to different stimuli and conditions; use of CellNO trap makes it possible to quantitatively determine the precise NO release profile generated from cells in a continuous and real-time manner with chemiluminescence detection.

Abstract  The NO3-initiated reactions of CH3OCH3 and CH3OCH2CH3 have been investigated by the BHandHLYP method in conjunction with the 6-311G(d,p) basis set. Thermodynamic and kinetic data are further refined using the comparatively accurate CCSD(T) method. According to the values of reaction enthalpies (ΔHr,298(θ)) and reaction Gibbs free energies (ΔGr,298(θ)) from CH3OCH2CH3 with NO3 system, we find that H-abstraction pathway from the α-CH2 group is more exothermic. It is further confirmed by the calculated CH bond dissociation energy of CH3OCH2CH3 molecule. All the rate constants, computed through means of canonical variational transition state with small-curvature tunneling correction, are fitted to the three-parameter expressions k1=1.54×10(-23)T(3.34)exp(-1035.53/T) and k2=3.55×10(-26)T(4.31)exp(-281.24/T)cm(3)molecule(-1)s(-1) and branching ratios are computed over the temperature range 200-600K. The branching ratios are also discussed. The atmospheric lifetimes of CH3OCH3 and CH3OCH2CH3 determined by the NO3 radical are about 270 and 29days, respectively.

Abstract  High concentration of fine particles (PM2.5), the primary concern about air quality in China, is believed to closely relate to China's large consumption of coal. In order to quantitatively identify the contributions of coal combustion in different sectors to ambient PM2.5, we developed an emission inventory for the year 2013 using up-to-date information on energy consumption and emission controls, and we conducted standard and sensitivity simulations using the chemical transport model GEOS-Chem. According to the simulation, coal combustion contributes 22 mu gm(-3) (40 %) to the total PM2.5 concentration at national level (averaged in 74 major cities) and up to 37 mu gm(-3) (50 %) in the Sichuan Basin. Among major coal-burning sectors, industrial coal burning is the dominant contributor, with a national average contribution of 10 mu gm(-3) (17 %), followed by coal combustion in power plants and the domestic sector. The national average contribution due to coal combustion is estimated to be 18 mu gm(-3) (46 %) in summer and 28 mu gm(-3) (35 %) in winter. While the contribution of domestic coal burning shows an obvious reduction from winter to summer, contributions of coal combustion in power plants and the industrial sector remain at relatively constant levels throughout the year.

Abstract  In EU-28, temporary grasslands constitute more than 10% of the total arable land. Grassland tillage will return up to 400 kg N ha(-1) in residues that can lead to a pulse of N2O emissions. Here a novel application of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) was evaluated in a 28-d mesocosm experiment, where DMPP spraying prior to tillage was simulated. Above-ground parts of N-15-labelled clover residues were treated with DMPP and either placed at 10 cm depth to simulate ploughing (PL), or mixed with soil at 0-10 cm depth to simulate rotovation (RO). Earthworms (Lumbricus terrestris) were introduced to study their role in residue decomposition and N2O emissions. Fluxes and isotopic composition of N2O were determined with dynamic chambers using laser spectroscopy. A gradual increase in N-15-enrichment of N2O indicated that denitrification was the main source. DMPP reduced cumulative N2O emissions in PL from 241 to 146 mg Nm(-2); the reduction in RO was smaller, from 103 to 94 mg N m(-2), and not significant, possibly due to higher oxygen and soil NO3- availability. After 28 d incubation, on average > 90% of the earthworms were recovered, and in vivo N2O production from L. terrestris accounted for only 1-6% of residue-induced emissions. The guts were removed from worms to quantify DNA and mRNA of denitrifying genes (nirK, nirS, nosZ Glade I and II). It was found that earthworm in vivo N2O production rates were negatively correlated to mRNA of nosZ-I, but positively to nir/nos ratio, suggesting the active involvement of denitrifiers associated with ingested feed in these emissions. Earthworm body tissue was enriched with N-15, with no effect of DMPP. This showed that the worms had fed on the clover residues, and that DMPP did not interfere with feeding behavior or nitrogen assimilation. The observed effects show that DMPP treatment of clover residue before tillage has the potential to modify N2O emissions without adverse effects on residue decomposition or soil fauna. (C) 2016 Elsevier Ltd. All rights reerved.

Abstract  The reduction of polybrominated o- and p-nitrophenols with granular tin in concentrated aqueous HCl gave polybrominated aminophenols which were diazotized with sodium nitrite in concentrated sulfuric acid at 0 degrees C to obtain polybrominated o- and p-quinone diazides. Their thermolysis with elimination of nitrogen generated ketocarbenes which reacted with acetylacetone to form insertion products at the activated methylene group. Ketocarbenes generated from o- quinone diazides reacted with typical dipolarophiles such as acetonitrile, benzonitrile, styrene, and phenylacetylene to afford the corresponding [3 + 2]-cycloaddition products.

Abstract  In this study, we have investigated the photolysis of 2,4,4'-tribromophenylphenyl ether (BDE-28) in Triton X-100 (TX-100) solutions, and discussed the effect of anthraquinone-2,6-disulfonate (AQDS) on the photolysis of BDE-28. The effect of TX-100 on the photolysis of BDE-28 was mainly related to the concentration of TX-100. The fastest photolysis of BDE-28 was at 500 mg L-1 of the TX-100 solution, and the corresponding photolysis rate constant was 0.12 min-1. The direct photolysis rate of BDE-28 decreased from 0.17 min-1 to 0.08 min-1 and 0.12 min-1 when NaN3 and isopropanol were added, respectively. The effect of AQDS on the photolysis of BDE-28 was also mainly related to the concentration of AQDS. When the concentration of AQDS was 0.6 μM, it has a slight influence in promoting the photodegradation of BDE-28; as the AQDS concentrations increased, the suppressing effect was more obvious. AQDS can inhibit the photolysis of BDE-28. Photolysis kinetics and quenching reactions illustrated that BDE-28 can produce a photosensitization reaction in TX-100 solutions, and the effects of AQDS on the photolysis of BDE-28 were mainly dominated by inhibition. In addition to its light shielding effect, AQDS can also combine with BDE-28 and anti-oxidation to inhibit the photolysis of BDE-28. We found that the degradation pathway of BDE-28 was mainly based on de-bromination, and the ions at para positions were preferentially debrominated.

Abstract  Winter is recognized as an important time for microbial activity that influences biogeochemical cycles. The onset of the winter snowpack in temperate hardwood ecosystems has been and will continue to be delayed over the next century. The decline in snowpack results in more soil freeze-thaw events and lower winter soil temperatures. Understanding microbial responses to varying snowpack conditions is important to understanding the effect of climate change on forest ecosystems. To this end, we removed snow to simulate a thinner, more ephemeral snowpack at two sites in the northeastern US, Harvard Forest (MA) and Hubbard Brook Experimental Forest (NH). We then measured microbial and exoenzyme activity in soils following snowmelt and three additional time points across the growing season. We found that microbial and exoenzyme activity were both positively correlated with the depth and duration of the snowpack at each site. The depth and duration of soil frost were negatively correlated with microbial biomass, exoenzyme activity and respiration, but only at Harvard Forest and not at Hubbard Brook. At both sites the changes in microbial and exoenzyme activity were transient and did not persist into the growing season past tree leaf-out. While it is possible that reductions in the snowpack and changes to microbial activity in the early spring may lead to asynchrony in the phenology of microbial relative to plant activity, it is at present uncertain whether and over what time scale this asynchrony may affect other forest ecosystem processes.