Polycyclic aromatic hydrocarbons and amino acids in meteorites and ice samples from LaPaz Icefield,Antarctica

Abstract— –We have analyzed ice samples and meteorites from the LaPaz region of Antarctica to investigate the composition of polycyclic aromatic hydrocarbons (PAHs) and amino acids with the goal to understand whether or not there is a compositional relationship between the two reservoirs. Four LL5 ordinary chondrites (OCs) and one CK carbonaceous chondrite were collected as part of the 2003/2004 ANSMET season. Ice samples collected from directly underneath the meteorites were extracted. In addition, exhaust particles from the snowmobiles used during the expedition were collected to investigate possible contributions from this source. The meteorite samples, the particulate matter and solid‐state extracts of the ice samples and the exhaust filters were subjected to two‐step laser mass spectrometry (L2MS) to investigate the PAH composition. For amino acids analysis, the meteorites were extracted with water and acid hydrolyzed, and the extracts were analyzed with offline OPA/NAC derivatization combined with liquid chromatography with UV fluorescence detection and time of flight mass spectrometry (LC‐FD/ToF‐MS). PAHs in the particulate matter of the ice were found to be qualitatively similar to the meteorite samples, indicating that micron‐sized grains of the meteorite may be embedded in the ice samples. The concentration levels of dissolved PAHs in all the ice samples were found to be below the detection limit of the L2MS. The PAH composition of the snowmobile exhaust is significantly different to the one in particulate matter, making it an unlikely source of contamination for Antarctic meteorites. The amino acids glycine, β‐alanine and γ‐amino‐n‐butyric acid that were detected at concentrations of 3 to 19 parts per billion (ppb) are probably indigenous to the Antarctic meteorites. Some of the LaPaz ice samples were also found to contain amino acids at concentration levels of 1 to 33 parts per trillion (ppt), in particular α‐aminoisobutyric acid (AIB), an abundant non‐protein amino acid of extraterrestrial origin found in some carbonaceous chondrites. We hypothesize that this amino acid could have been extracted from Antarctic micrometeorites and the particulate matter of the meteorites during the concentration procedure of the ice samples.     

Probabilistic risk assessment of contaminant transport in groundwater and vapour intrusion following remediation of a contaminant source

Community-scale simulations were performed to investigate the risk to groundwater and indoor air receptors downgradient of a contaminated site following the remediation of a long-term source. Six suites of Monte Carlo simulations were performed using a numerical model that accounted for groundwater flow, reactive solute transport, soil gas flow, and vapour intrusion in buildings. The model was applied to a three-dimensional, community-scale (250 m × 1000 m × 14 m) domain containing heterogeneous, spatially correlated distributions of the hydraulic conductivity, fraction of organic carbon, and biodegradation rate constant, which were varied between realizations. Analysis considered results from both individual realizations as well as the suite of Monte Carlo simulations expressed through several novel, integrated parameters, such as the probability of exceeding a regulatory standard in either groundwater or indoor air. Results showed that exceedance probabilities varied considerably with the consideration of biodegradation in the saturated zone, and were less sensitive to changes in the variance of hydraulic conductivity or the incorporation of heterogeneous distributions of organic carbon at this spatial scale. A sharp gradient in exceedance probability existed at the lateral edges of the plumes due to variability in lateral dispersion, which defined a narrow region of exceedance uncertainty. Differences in exceedance probability between realizations (i.e., due to heterogeneity uncertainty) were similar to differences attributed to changes in the variance of hydraulic conductivity or fraction of organic carbon. Simulated clean-up times, defined by reaching an acceptable exceedance probability, were found to be on the order of decades to centuries in these community-scale domains. Results also showed that the choice of the acceptable exceedance probability level (e.g., 1 vs. 5 %) would likely affect clean up times on the order of decades. Moreover, in the scenarios examined here, the risk of exceeding indoor air standards was greater than that of exceeding groundwater standards at all times and places. Overall, simulations of coupled transport processes combined with novel spatial and temporal quantification metrics for Monte Carlo analyses, provide practical tools for assessing risk in wider communities when considering site remediation.     

Mid-Mountain Clouds at Whistler During the Vancouver 2010 Winter Olympics and Paralympics

A comprehensive study of mid-mountain clouds and their impacts on the Vancouver 2010 Winter Olympics and Paralympics is presented. Mid-mountain clouds were frequently present on the Whistler alpine venue, as identified in an extensive archive of webcam images over a 45-day period from February 5 to March 21, 2010. These clouds posed serious forecast challenges and had significant impacts on some Olympic and Paralympic alpine skiing competitions. Under fair weather conditions, a diurnal upslope (anabatic) flow can work in concert with a diurnal temperature inversion aloft to produce a localized phenomenon known as “Harvey’s Cloud” at Whistler. Two detailed case studies in this paper suggest that mid-mountain clouds can also develop in the area as a result of a moist valley flow interacting with a downslope flow descending from the mountaintop. A southerly inflow through the Sea-to-Sky corridor can be channeled by the local topography into a westerly upslope flow toward Whistler Mountain, resulting in orographic clouds on the alpine venue. Under favorable circumstances, these clouds are trapped to the mid-mountain zone by the leeward subsidence of an elevated southerly flow. The presence of the downslope subsidence was manifested by a distinguished dry layer observed on the top of the mid-mountain clouds in both cases. It is the subsidence-induced adiabatic warming that imposes a strong buoyant suppression to trap the mid-mountain cloud. On the other hand, the subsidence-induced dry layer has the potential to trigger evaporative instability to periodically breakup the mid-mountain cloud.     

Shoreline features of Titan's Ontario Lacus from Cassini/VIMS observations

We analyze observations of Titan's south polar lake Ontario Lacus obtained by Cassini's Visual and Infrared Mapping Spectrometer during the 38th flyby of Titan (T38; 2007 December 5). These near-closest-approach observations have the highest signal-to-noise, the finest spatial resolution, and the least atmospheric influence of any near-infrared lake observation to date. We use the large, spatially flat, and low-albedo interior of Ontario Lacus as a calibration target allowing us to derive an analytical atmospheric correction for emission angle. The dark lake interior is surrounded by two separate annuli that follow the lake interior's contours. The inner annulus is uniformly dark, but not so much as the interior lake, and is generally 5-10 kilometers wide at the lake's southeastern margin. We propose that it represents wet lakebed sediments exposed by either tidal sloshing of the lake or seasonal methane loss leading to lower lake-volume. The exterior annulus is bright and shows a spectrum consistent with a relatively low water-ice content relative to the rest of Titan. It may represent fine-grained condensate deposits from a past era of higher lake level. Together, the annuli seem to indicate that the lake level for Ontario Lacus has changed over time. This hypothesis can be tested with observations scheduled for future Titan flybys.     

Metal-line system survey: characterizing the low-redshift IGM

The low-redshift IGM probes the last ten billion years of metal enrichment from galactic feedback processes. We present preliminary results from a survey of intergalactic metal-line absorption systems in archival HST STIS, GHRS, and FUSE spectra of ≈50 z?2 UV-bright objects. We summarize the detailed analysis of one sightline (PKS1302–102, z _QSO =0.2784) with which we set the methodology for the larger survey. We use simple CLOUDY models to constrain the ionizing mechanism(s) and metallicities for the metal-line systems. For about 15 sightlines, including PKS1302–102, we have a complementary galaxy survey, and we look for correlations between galaxies and absorption systems in order to understand the large-scale distribution of the metal-enriched IGM.     

An AzTEC 1.1 mm survey of the GOODS-N field – II. Multiwavelength identifications and redshift distribution

We present results from a multiwavelength study of 29 sources (false detection probabilities <5 per cent) from a survey of the Great Observatories Origins Deep Survey-North (GOODS-N) field at 1.1 mm using the Astronomical Thermal Emission Camera (AzTEC). Comparing with existing 850 μm Submillimetre Common-User Bolometer Array (SCUBA) studies in the field, we examine differences in the source populations selected at the two wavelengths. The AzTEC observations uniformly cover the entire survey field to a 1σ depth of ∼1 mJy. Searching deep 1.4 GHz Very Large Array (VLA) and Spitzer 3–24 μm catalogues, we identify robust counterparts for 21 1.1 mm sources, and tentative associations for the remaining objects. The redshift distribution of AzTEC sources is inferred from available spectroscopic and photometric redshifts. We find a median redshift of   z = 2.7  , somewhat higher than   z = 2.0  for  850 μm  selected sources in the same field, and our lowest redshift identification lies at a spectroscopic redshift   z = 1.1460  . We measure the 850 μm to 1.1 mm colour of our sources and do not find evidence for '850 μm dropouts', which can be explained by the low signal-to-noise ratio of the observations. We also combine these observed colours with spectroscopic redshifts to derive the range of dust temperatures T , and dust emissivity indices β for the sample, concluding that existing estimates   T ∼ 30 K  and  β∼ 1.75  are consistent with these new data.     

Cometary glycine detected in samples returned by Stardust

Abstract— Our previous analysis of cometary samples returned to Earth by NASA's Stardust spacecraft showed several amines and amino acids, but the origin of these compounds could not be firmly established. Here, we present the stable carbon isotopic ratios of glycine and ε‐amino‐n‐caproic acid (EACA), the two most abundant amino acids identified in Stardust‐returned foil samples measured by gas chromatography‐mass spectrometry coupled with isotope ratio mass spectrometry. The δ¹³C value for glycine of +29 ± 6‰ strongly suggests an extraterrestrial origin for glycine, while the δ¹³C value for EACA of ?25 ± 2‰ indicates terrestrial contamination by Nylon‐6 during curation. This represents the first detection of a cometary amino acid.     

Wildfire occurrence patterns in ecoregions of New South Wales and Australian Capital Territory,Australia

Natural Hazards - Wildfire occurrence is regulated by many factors such as climate, vegetation, topography and ignition source. The effects of these factors vary across space. In this study,...