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431.
Roberto Sommariva Tim S. Bates Daniel Bon Daniel M. Brookes Joost A. de Gouw Jessica B. Gilman Scott C. Herndon William C. Kuster Brian M. Lerner Paul S. Monks Hans D. Osthoff Alex E. Parker James M. Roberts Sara C. Tucker Carsten Warneke Eric J. Williams Mark S. Zahniser Steven S. Brown 《Journal of Atmospheric Chemistry》2011,68(4):331-362
Measurements of total peroxy radicals (HO2?+?RO2) and nitrate radical (NO3) were made on the NOAA research vessel R/V?Brown along the U.S. Gulf Coast during the TexAQS 2006 field campaign. The measurements were modelled using a constrained box-model based upon the Master Chemical Mechanism (MCM). The agreement between modelled and measured HO2?+?RO2 was typically within ??40% and, in the unpolluted regions, within 30%. The analysis of the model results suggests that the MCM might underestimate the concentrations of some acyl peroxy radicals and other small peroxy radicals. The model underestimated the measurements of NO3 by 60?C70%, possibly because of rapid heterogeneous uptake of N2O5. The MCM model results were used to estimate the composition of the peroxy radical pool and to quantify the role of DMS, isoprene and alkenes in the formation of RO2 in the different regions. The measurements of HO2?+?RO2 and NO3 were also used to calculate the gas-phase budget of NO3 and quantify the importance of organic peroxy radicals as NO3 sinks. RO2 accounted, on average, for 12?C28% of the total gas-phase NO3 losses in the unpolluted regions and for 1?C2% of the total gas-phase NO3 losses in the polluted regions. 相似文献
432.
Quentin A. Parker A. Acker D. J. Frew M. Hartley A. E. J. Peyaud F. Ochsenbein S. Phillipps D. Russeil S. F. Beaulieu M. Cohen J. Köppen B. Miszalski D. H. Morgan R. A. H. Morris M. J. Pierce A. E. Vaughan 《Monthly notices of the Royal Astronomical Society》2006,373(1):79-94
We present the Macquarie/AAO/Strasbourg Hα Planetary Nebula Catalogue (MASH) of over 900 true, likely and possible new Galactic planetary nebulae (PNe) discovered from the AAO/UKST Hα survey of the southern Galactic plane. The combination of depth, resolution, uniformity and areal coverage of the Hα survey has opened up a hitherto unexplored region of parameter space permitting the detection of this significant new PN sample. Away from the Galactic bulge the new PNe are typically more evolved, of larger angular extent, of lower surface brightness and more obscured (i.e. extinguished) than those in most previous surveys. We have also doubled the number of PNe in the Galactic bulge itself and although most are compact, we have also found more evolved examples. The MASH catalogue represents the culmination of a seven-year programme of identification and confirmatory spectroscopy. A key strength is that the entire sample has been derived from the same, uniform observational data. The 60 per cent increase in known Galactic PNe represents the largest ever incremental sample of such discoveries and will have a significant impact on many aspects of PN research. This is especially important for studies at the faint end of the PN luminosity function which was previously poorly represented. 相似文献
433.
Heavy metal levels in surface sediments from Tamaki Estuary demonstrate significant up estuary increases in Cu, Pb, Zn, Cd
and mud concentrations. Increased metal levels towards the head of the estuary are linked to local catchment sources reflecting
the historical development, industrialisation and urbanisation of catchment areas surrounding the upper estuary. The relatively
narrow constriction in the middle estuary (Panmure area), makes it susceptible to accumulation of upper estuary pollutants,
since the constriction reduces circulation and extends the time required for fine waterborne sediments in the upper estuary
to exchange with fresh coastal water. As a result fine fraction sediments trapped in the upper estuary facilitate capture
and retention of pollutants at the head of the estuary. The increase in sandy mud poor sediments towards the mouth of the
estuary is associated with generally low metal concentrations. The estuary’s geomorphic shape with a mid estuary constriction,
sediment texture and mineralogy and catchment history are significant factors in understanding the overall spatial distribution
of contaminants in the estuary. Bulk concentration values for Cu, Pb, Zn, and Cd in all the studied surface samples occur
below ANZECC ISQG-H toxicity values. Cd and Cu concentrations are also below the ISQG-L toxicity levels for these elements.
However, Pb and Zn concentrations do exceed the ISQG-L values in some of the surface bulk samples in the upper estuary proximal
to long established sources of catchment pollution. 相似文献