Coastal water source of short‐lived halocarbons in New England

Short‐lived halocarbon tracers were used to investigate marine influences on air quality in a coastal region of New England. Atmospheric measurements made at the University of New Hampshire\u27s Observing Station at Thompson Farm (TF) in Durham, New Hampshire, indicate that relatively large amounts of halocarbons are emitted from local estuarine and coastal oceanic regions. Bromine‐containing halocarbons of interest in this work include bromoform (CHBr3) and dibromomethane (CH2Br2). The mean mixing ratios of CHBr3 and CH2Br2 from 11 January to 5 March 2002 were 2.6 pptv and 1.6 pptv, and from 1 June to 31 August 2002 mean mixing ratios were 5.9 pptv and 1.4 pptv, respectively. The mean mixing ratio of CHBr3 was not only highest during summer, but both CHBr3 and CH2Br2 exhibited large variability in their atmospheric mixing ratios during this season. We attribute the greater variability to increased production combined with faster atmospheric removal rates. Other seasonal characteristics of CHBr3 and CH2Br2 in the atmosphere, as well as the impact of local meteorology on their distributions at this coastal site, are discussed. Tetrachloroethene (C2Cl4) and trichloroethene (C2HCl3) were used to identify time periods influenced by urban emissions. Additionally, measurements of CHBr3, CH2Br2, C2Cl4, methyl iodide (CH3I), and ethyl iodide (C2H5I) were made at TF and five sites throughout the nearby Great Bay estuarine area between 18 and 19 August 2003. These measurements were used to elucidate the effect of the tidal cycle on the distributions of these gases. The mean mixing ratios of CHBr3, CH2Br2, CH3I, and C2H5I were ∼82%, 46%, 14%, and 17% higher, respectively, near the coast compared to inland sites, providing evidence for a marine source of short‐lived halocarbons at TF. Correlation between the tidal cycle and atmospheric concentrations of marine tracers on the night of 18 August 2003 showed that the highest values for the brominated species occurred ∼2–3 hours after high tide. Emission fluxes of CHBr3, CH2Br2, CH3I, and C2H5I on this night were estimated to be 26 ± 57, 4.7 ± 5.4, 5.9 ± 4.6, and 0.065 ± 0.20 nmol m−2 h−1, respectively. Finally, the anthropogenic source strength of CHBr3 was calculated to determine its impact on atmospheric levels observed in this region. Although our results indicate that anthropogenic contributions could potentially range from 15 to 60% of the total dissolved CHBr3 in the Great Bay, based on the observed ratio of CH2Br2/CHBr3 and surface seawater measurements in the Gulf of Maine, it appears unlikely that anthropogenic activities are a significant source of CHBr3 in the region

Are biogenic emissions a significant source of summertime atmospheric toluene in the rural Northeastern United States?

Summertime atmospheric toluene enhancements at Thompson Farm in the rural northeastern United States were unexpected and resulted in a toluene/benzene seasonal pattern that was distinctly different from that of other anthropogenic volatile organic compounds. Consequently, three hydrocarbon sources were investigated for potential contributions to the enhancements during 2004–2006. These included: (1) increased warm season fuel evaporation coupled with changes in reformulated gasoline (RFG) content to meet US EPA summertime volatility standards, (2) local industrial emissions and (3) local vegetative emissions. The contribution of fuel evaporation emission to summer toluene mixing ratios was estimated to range from 16 to 30 pptv d−1, and did not fully account for the observed enhancements (20–50 pptv) in 2004–2006. Static chamber measurements of alfalfa, a crop at Thompson Farm, and dynamic branch enclosure measurements of loblolly pine trees in North Carolina suggested vegetative emissions of 5 and 12 pptv d−1 for crops and coniferous trees, respectively. Toluene emission rates from alfalfa are potentially much larger as these plants were only sampled at the end of the growing season. Measured biogenic fluxes were on the same order of magnitude as the influence from gasoline evaporation and industrial sources (regional industrial emissions estimated at 7 pptv d−1 and indicated that local vegetative emissions make a significant contribution to summertime toluene enhancements. Additional studies are needed to characterize the variability and factors controlling toluene emissions from alfalfa and other vegetation types throughout the growing season

A new prevalence study of multiple sclerosis in Orkney, Shetland and Aberdeen city

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Bromoform and dibromomethane measurements in the seacoast region of New Hampshire, 2002–2004

Atmospheric measurements of bromoform (CHBr3) and dibromomethane (CH2Br2) were conducted at two sites, Thompson Farm (TF) in Durham, New Hampshire (summer 2002–2004), and Appledore Island (AI), Maine (summer 2004). Elevated mixing ratios of CHBr3 were frequently observed at both sites, with maxima of 37.9 parts per trillion by volume (pptv) and 47.4 pptv for TF and AI, respectively. Average mixing ratios of CHBr3 and CH2Br2 at TF for all three summers ranged from 5.3–6.3 and 1.3–2.3 pptv, respectively. The average mixing ratios of both gases were higher at AI during 2004, consistent with AI\u27s proximity to sources of these bromocarbons. Strong negative vertical gradients in the atmosphere corroborated local sources of these gases at the surface. At AI, CHBr3 and CH2Br2 mixing ratios increased with wind speed via sea‐to‐air transfer from supersaturated coastal waters. Large enhancements of CHBr3 and CH2Br2 were observed at both sites from 10 to 14 August 2004, coinciding with the passage of Tropical Storm Bonnie. During this period, fluxes of CHBr3 and CH2Br2 were 52.4 ± 21.0 and 9.1 ± 3.1 nmol m−2 h−1, respectively. The average fluxes of CHBr3 and CH2Br2 during nonevent periods were 18.9 ± 12.3 and 2.6 ± 1.9 nmol m−2 h−1, respectively. Additionally, CHBr3 and CH2Br2 were used as marine tracers in case studies to (1) evaluate the impact of tropical storms on emissions and distributions of marine‐derived gases in the coastal region and (2) characterize the transport of air masses during pollution episodes in the northeastern United States

Volatile organic compounds in northern New England marine and continental environments during the ICARTT 2004 campaign

Volatile organic compound (VOC) measurements were made during the summer 2004 International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) at Thompson Farm (TF), a continental site 25 km from the New Hampshire coast, and Appledore Island (AI), a marine site 10 km off the Maine coast. The 24 h mean total hydroxyl radical (OH) reactivity (±1σ) for the suite of VOCs was 4.15 (±2.64) s−1 at TF and 2.57 (±1.10) s−1 at AI. The larger range of reactivity at TF was dominated by isoprene and the monoterpenes (mean combined reactivity = 2.01 (±2.57) s−1). The impact of local anthropogenic hydrocarbon sources such as liquefied petroleum gas (LPG) leakage and fossil fuel evaporation was evident at both sites. During the campaign, a propane flux of 9 (±2) × 109 molecules cm−2 s−1 was calculated from the linear regression of the mean 0100–0400 local time mixing ratios at TF. This is consistent with fluxes observed in 2003 at sites spread throughout the coastal area of New Hampshire indicating that LPG tank leakage is a major hydrocarbon source throughout the region. Net monoterpene fluxes during ICARTT at TF were 6 (±2), 1.8 (±0.4), 1.2 (±0.6), and 0.4 (±0.5) × 109 molecules cm−2 s−1 for α‐pinene, β‐pinene, camphene, and limonene, respectively. Comparison to estimated NO3 and O3 loss rates indicate that gross monoterpene emission rates were approximately double the observed net fluxes at TF and comparable to current monoterpene nighttime emission inventory estimates for the northeast

Efficient room temperature aqueous Sb2S3 synthesis for inorganic-organic sensitized solar cells with 5.1% efficiencies.

Sb2S3 sensitized solar cells are a promising alternative to devices employing organic dyes. The manufacture of Sb2S3 absorber layers is however slow and cumbersome. Here, we report the modified aqueous chemical bath synthesis of Sb2S3 absorber layers for sensitized solar cells. Our method is based on the hydrolysis of SbCl3 to complex antimony ions decelerating the reaction at ambient conditions, in contrast to the usual low temperature deposition protocol. This simplified deposition route allows the manufacture of sensitized mesoporous-TiO2 solar cells with power conversion efficiencies up to η = 5.1%. Photothermal deflection spectroscopy shows that the sub-bandgap trap-state density is lower in Sb2S3 films deposited with this method, compared to standard deposition protocols.Cambridge Trust, the Mott Fund for Physics of the Environment and Corpus Christi College Cambridge for funding. A.S. acknowledges funding from the Engineering and Physical Sciences Research Council (EPSRC).This is the final version. It first appeared at http://pubs.rsc.org/en/Content/ArticleLanding/2015/CC/c5cc01966d#!divAbstract

The Star Formation Rate Function of the Local Universe

We have derived the bivariate luminosity function for the far ultraviolet (1530Angstroms) and far infrared (60 microns). We used matched GALEX and IRAS data, and redshifts from NED and PSC-z. We have derived a total star formation luminosity function phi(L_{tot}), with L_{tot} = L_{FUV}+L_{FIR}. Using these, we determined the cosmic ``star formation rate'' function and density for the local universe. The total SFR function is fit very well by a log-normal distribution over five decades of luminosity. We find that the bivariate luminosity function phi(L_{FUV},L_{FIR}) shows a bimodal behavior, with L_{FIR} tracking L_{FUV} for L_{TOT}< 10^10 L_sun, and L_{FUV} saturating at 10^10 L_sun, while L_{TOT} L_{FIR} for higher luminosities. We also calculate the SFR density and compare it to other measurements.Comment: This paper will be published as part of the Galaxy Evolution Explorer (GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of papers will be available at http:/www.galex.caltech.edu/PUBLICATIONS/ after November 22, 200

GALEX Ultraviolet Photometry of Globular Clusters in M31

We present ultraviolet photometry for globular clusters (GCs) in M31 from 15 square deg of imaging using the Galaxy Evolution Explorer (GALEX). We detect 200 and 94 GCs with certainty in the near-ultraviolet (NUV; 1750 - 2750 Angstroms) and far-ultraviolet (FUV; 1350 - 1750 Angstroms) bandpasses, respectively. Our rate of detection is about 50% in the NUV and 23% in the FUV, to an approximate limiting V magnitude of 19. Out of six clusters with [Fe/H]>-1 seen in the NUV, none is detected in the FUV bandpass. Furthermore, we find no candidate metal-rich clusters with significant FUV flux, because of the contribution of blue horizontal-branch (HB) stars, such as NGC 6388 and NGC 6441, which are metal-rich Galactic GCs with hot HB stars. We show that our GALEX photometry follows the general color trends established in previous UV studies of GCs in M31 and the Galaxy. Comparing our data with Galactic GCs in the UV and with population synthesis models, we suggest that the age range of M31 and Galactic halo GCs are similar.Comment: This paper will be published as part of the Galaxy Evolution Explorer (GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of papers will be available at http://www.galex.caltech.edu/PUBLICATIONS/ after November 22, 200