Water vapour mixing ratio profiles over Hornsund, Arctic. Intercomparison of lidar and AIRS results

Since October 2009, a ground-based Raman lidar system has been deployed to perform a regular, night-time, vertical sounding of a water vapour content in the lower and middle troposphere above Polish Polar Station at Hornsund (77.00°N, 15.55°E, 10 m a.s.l.) in the Arctic. The water vapour mixing ratio profiles were obtained for the atmosphere up to 6 km altitude, based on analysis of inelastic Raman backscattering signals from nitrogen molecules (at 387 nm) and water vapour particles (at 407 nm), calibrated with the data from a local Vaisala’s automatic meteorological station. The results obtained for winter seasons in the years 2009–2012 are in a good general agreement with the results obtained from the atmospheric infrared sounder (AIRS) on the Aqua satellite.     

Investigation of the 16-year and 18-year ZTD Time Series Derived from GPS Data Processing

The GPS system can play an important role in activities related to the monitoring of climate. Long time series, coherent strategy, and very high quality of tropospheric parameter Zenith Tropospheric Delay (ZTD) estimated on the basis of GPS data analysis allows to investigate its usefulness for climate research as a direct GPS product. This paper presents results of analysis of 16-year time series derived from EUREF Permanent Network (EPN) reprocessing performed by the Military University of Technology. For 58 stations Lomb-Scargle periodograms were performed in order to obtain information about the oscillations in ZTD time series. Seasonal components and linear trend were estimated using Least Square Estimation (LSE) and Mann—Kendall trend test was used to confirm the presence of a linear trend designated by LSE method. In order to verify the impact of the length of time series on trend value, comparison between 16 and 18 years were performed.     

Evaluating the sulfur isotopic composition of biodegraded petroleum: The case of the Western Canada Sedimentary Basin

The sulfur isotopic composition (δ³⁴S) of petroleum is believed to be affected mainly by sulfur incorporation reactions into the sedimentary organic matter during the early diagenesis. However, secondary processes could affect the original δ³⁴S of oil under the effect of thermal maturity or of the microbial activity of biodegraded reservoirs. In this study, the different processes that may affect the δ³⁴S of in-reservoir oils were assessed based on the sulfur content and isotopes of a series of oil and core samples coming from various reservoirs of the Lower Cretaceous Mannville Group, Western Canada Sedimentary Basin (WCSB). Based on the molecular study, these samples appear to have reached various levels of maturity and biodegradation, ranging from 0 to 6.5 on the biodegradation scale of Peters and Moldowan. In addition, mixing of organic matter coming from different source rocks was identified based on the comparison with extensive correlation studies performed in the WCSB.Investigation of the δ³⁴S shows a trend that seems a priori correlated to the level of biodegradation. However, a careful interpretation of molecular and sulfur isotope data leads to the conclusion that the observed δ³⁴S variations have rather to be ascribed to contributions of oils generated by various source rocks. Alternatively, variations of δ³⁴S could neither be related to maturity differences nor to kinetic effects during organic sulfur compounds biodegradation. In the case of some specific core samples showing a common origin based on biomarker study, δ³⁴S variations might not be related to different sources but to secondary sulfur incorporation/exchange processes occurring within the reservoir. These processes would involve reduced sulfur species from bacterial sulfate reduction formed in situ or migrated into Mannville reservoirs. This hypothesis is supported by laboratory experiments showing sulfur exchange/incorporation under plausible conditions for shallow reservoirs.     

Molecular and isotopic fractionation of light hydrocarbons between oil and gas phases

Oil-gas phase equilibria is likely to represent one of the main causes of observed compositional heterogeneities in fields. Our research has been focused mainly on the light C₁₄-hydrocarbons fraction and can be divided into two parts. The first part was performed with a fluid mixture of a Middle East crude oil and a synthetic gas, and includes PVT experiments, high resolution-gas chromatography (HR-GC) and ¹³C gas chromatography-combustion-isotopic ratio mass spectrometry (GC-C-IR-MS) analyses. Our observations show that under a given set of PT conditions there is a preferential separation of aromatics into the oil phase and isoalkanes into the gas phase. Moreover, the data from ¹³C GC-C-IRMS suggest a small isotopic fractionation between the two phases, with the gas being relatively isotopically lighter. The second part is theoretical, and uses Equation of State (EOS) calculations which successfully simulate the previous experiment.     

Cerium and Ytrium in apatite as records of magmatic processes: Insight into fractional crystallization,magma mingling and fluid saturation

Apatite is a versatile mineral crystallizing at different stages of silicic magma evolution. Its composition may record that of magma, but could also be affected by interaction with fluids. The focus of this study is the well-recognized magma mingling process that was previously detected using plagioclase composition and in this study complementary record is sought in apatite. The apatite was analysed in two dioritic enclaves (primitive and hybrid) and host quartz monzonite, which is an igneous rock emplaced at ca. 340 Ma in mylonitized Góry Sowie gneisses (NE Bohemian Massif). The apatite was analysed in-situ by microprobe that allowed for chemical characterization of different apatite populations in quartz monzonite and analyses of thin acicular apatite in the enclaves. Apatite population in the quartz monzonite was chemically distinct from that in both enclave types and characterized by higher Y and lower Ce contents, such values are usually typical for peraluminous magmas. As such, the apatite transfer from felsic to mafic magma should be well recorded in apatite composition, which was not the case. Monzonite apatite composition was not commonly observed in the hybrid enclave despite massive plagioclase transfer and only rare resorbed cores with low Ce and Y contents were present. However, such low Ce and Y cores crystalized at the latest stage of apatite crystallization in the quartz monzonite, whereas the plagioclase transfer was an early episode. Therefore, we conclude that apatite transfer was limited during mingling and the apatite composition in the quartz monzonite is best explained by an early Cl-Ce-rich fluid removal and then fractional crystallization, while apatite in the primitive enclave is affected only by fractional crystallization. Altogether, Ce and Y composition of apatite is a valuable tool to record diverse magmatic processes such as fluid removal and precipitation from fluid in addition to fractionation of different REE phases and should be further explored.     

The usability of the undifferenced positioning techniques in establishing regional geodetic control networks: a case study in Poland

Recently undifferenced Precise Point Positioning (PPP) technique has become a subject of interest not only among researchers, but also satellite positioning practitioners like surveyors and engineers. Along with the development of precise clocks and orbits products, and the improvement of models mitigating interfering phenomena like atmospheric refraction, PPP has become an alternative to relative positioning in many field applications. This study concerns the usability of Undifferenced Positioning techniques in establishing geodetic control networks. Satellite observations from 13 stations equipped with high-end receivers and survey grade commercial receivers were processed using the NAvigation Package for Earth Observation Satellites -NAPEOS v. 3.3.1. In the study the standard PPP (float) and Undifferenced Network solution with clocks/orbits fixed strategies of post-processing were carried out using various observing intervals (30 min., 1 h, 2 h, 4 h, daily). The high accuracy results obtained with PPP and UD Network solution predisposes these strategies for the use in surveying tasks requiring even centimeter positioning accuracy.     

Geomorphic and hydrological controls on groundwater dolocrete formation in the semi-arid Hamersley Basin,northwest Australia

Groundwater dolocretes may exert an important geomorphic control on landscape evolution within sub-humid to arid regions. However, the geomorphic and hydrogeological settings of dolocrete remain poorly described. The hydrochemical conditions of dolomite precipitation in groundwater environments are also not well known. Classic models of dolocrete formation explain dolomite precipitation from highly evolved groundwaters at the terminus of major drainage but do not explain dolocrete distributed in regionally elevated landscapes, upgradient of major drainage. This study investigated the mineralogy, micromorphology and stable carbon and oxygen isotope compositions of three dolocrete profiles within a regionally elevated sub-basin of the Hamersley Ranges in the Pilbara region of northwest Australia. We sought to establish the environmental and hydrochemical conditions and present a model for dolocrete formation. We found that dolocrete formed within zones of emerging groundwater under saline-evaporitic conditions within internally draining sub-basins, most likely during the Late Miocene and Pliocene. Saline-evaporitic conditions were indicated by: (i) the mineralogy, dominated by dolomite, palygorskite and smectite; (ii) desiccation features and the presence of phreatic and vadose cements, indicative of a shallow fluctuating water table, and; (iii) dolomite δ¹⁸O values (median = –5.88 ‰). Dolomite precipitation was promoted by evaporation and carbon dioxide degassing from shallow magnesium (Mg)-rich groundwater. These factors appear to have been the major drivers of dolocrete development without a requirement for significant down-dip hydrochemical modification. Primary dolomite precipitation was possible due to the presence of microbial extracellular polymeric substances (EPS). EPS provided negatively charged nucleation sites, which bound Mg²⁺, overcoming kinetic effects. High microbial activity within groundwater systems suggest these processes may be important for dolocrete formation worldwide and that groundwater dolocretes may be more pervasive in landscapes than currently recognized. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.     

How selection and weighting of astrometric observations influence the impact probability. The case of asteroid (99942) Apophis

The aim of this paper is to show that in the case of a low probability of asteroid collision with the Earth, the appropriate selection and weighting of the data are crucial for the impact investigation and for analysing the impact possibilities using extensive numerical simulations. By means of the Monte Carlo special method, a large number of 'clone' orbits have been generated. A full range of orbital elements in the six-dimensional parameter space, that is, in the entire confidence region allowed by the observational material, has been examined. On the basis of 1000 astrometric observations of (99942) Apophis, the best solutions for the geocentric encounter distance of  6.065 ± 0.081 R_⊕  (without perturbations by asteroids) or  6.064 ± 0.095 R_⊕  (including perturbations by the four largest asteroids) were derived for the close encounter with the Earth on 2029 April 13. The present uncertainties allow for special configurations ('keyholes') during this encounter that may lead to very close encounters in future approaches of Apophis. Two groups of keyholes are connected with the close encounter with the Earth in 2036 (within the minimal distance of  5.7736−5.7763 R_⊕  on 2029 April 13) and 2037 (within the minimal distance of  6.3359–6.3488 R_⊕  ). The nominal orbits for our most accurate models run almost exactly in the middle of these two impact keyhole groups. A very small keyhole for the impact in 2076 has been found between these groups at the minimal distance of 5.97347   R_⊕  . This keyhole is close to the nominal orbit. The present observations are not sufficiently accurate to eliminate definitely the possibility of impact with the Earth in 2036 and for many years after.