276 research outputs found
The relationship between successional vascular plant assemblages and associated microbial communities on coal mine spoil heaps
The aim of the study was to investigate the relationships between the vascular plant species and the associated soil microbial properties at various stages of vegetation development on unclaimed hard coal mine spoil heaps in Upper Silesia (south Poland). The spontaneous vegetation, soil chemistry as well as the activity and structure of microbial communities were recorded on this specific habitat. The colliery heaps were divided into four age classes and the plant species composition and cover abundance were recorded on established plots (2 m × 2 m). The soil microbial activity under the vegetation patches was assessed using fluorescein diacetate hydrolytic activity (FDHA) and the soil microbial biomass and community composition were determined by phospholipid fatty acid (PLFA) biomarkers. Total microbial biomass in soils from the older vegetation plots was significantly higher than those in soils from the younger plots. In all studied samples, microbial communities consisted primarily of bacteria with the dominance of Gram negative bacteria over Gram positive and aerobic microorganisms were more dominant than anaerobic ones. Statistical analysis revealed a correlation between the type of vegetation and microbial community structure
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Lidar Measurements of Canadian Forest Fire Smoke Episode Observed in July 2013 over Warsaw, Poland
This paper presents a preliminary study of aerosol optical properties of air-mass advected on 10th July 2013 from Canada above Warsaw, Poland, during the forest fire event that occurred in Quebec at the beginning of July 2013. The observations were conducted with use of the modern version of 8-channel PollyXT lidar capable of measuring at 3β+2α+2δ+VW and interpreted with available information from the MACC model, the CALIPSO and MODIS satellite sensors, the AERONET data products and the data gathered within the Poland-AOD network
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Near-range receiver unit of next generation PollyXT used with Koldeway aerosol Raman lidar in Arctic
The Near-range Aerosol Raman lidar (NARLa) receiver unit, that was designed to enhance the detection range of the NeXT generation PollyXT Aerosol-Depolarization-Raman (ADR) lidar of the University of Warsaw, was employed next the Koldeway Aerosol Raman Lidar (KARL) at the AWI-IPEV German-French station in Arctic during Spring 2015. Here we introduce shortly design of both lidars, the scheme of their installation next to each other, and preliminary results of observations aiming at arctic haze investigation by the lidars and the iCAP a set of particle counter and aethalometer installed under a tethered balloon
SAWA experiment ? properties of mineral dust aerosol as seen by synergic lidar and sun-photometer measurements
International audienceWe propose a method of retrieving basic information on mineral dust aerosol particles from synergic sun-photometer and multi-wavelength lidar measurements as well as from the observations of lidar light depolarisation. We use this method in a case study of mineral dust episode in Central Europe. Lidar signals are inversed with a modified Klett-Fernald algorithm. Aerosol optical depth measured with the sun-photometer allows to reduce uncertainties in the inversion procedure through which we estimate vertical profile of aerosol extinction. Next we assume that aerosol particles may be represented by ensemble of randomly oriented, identical spheroids. Having calculated vertical profiles of aerosol extinction coefficients for lidar wavelengths, we compute the profiles of local Angstrom exponent. We use laser beam depolarisation together with the calculated Angstrom exponents to estimate the shapes (aspect ratios) and sizes of the spheroids. Numerical calculations are performed with the transition matrix (T-matrix) algorithm by M. Mishchenko. The proposed method was first used during SAWA measurement campaign in Warsaw, spring 2005, to characterise the particles of desert dust, drifting over Poland with a southern-eastern wind (13?14 April). Observations and T-matrix calculations show that mode radii of spheroids representative for desert aerosols' particles are in the range of 0.15?0.3 ?m, while their aspect ratios are lower than 0.7 or larger than 1.7
Conventional Dendritic Cells Mount a Type I IFN Response against Candida spp. Requiring Novel Phagosomal TLR7-Mediated IFN-β Signaling
Individual Particle Characteristics, Optical Properties and Evolution of an Extreme Long‐Range Transported Biomass Burning Event in the European Arctic (Ny‐Ålesund, Svalbard Islands)
This paper reports an exceptional biomass burning (BB) advection event from Alaska registered at Ny‐Ålesund from 10 to 17 July 2015 with particular interest on the influence of the airborne particle characteristics on the optical properties of the aerosol during the event. To this purpose we considered two DEKATI 12‐stage aerosol samples spanning the entire advection and analyzed them by scanning electron microscopy techniques. Aerosol chemical data and microphysical properties were also evaluated in order to correlate any change of individual particle characteristics with the bulk properties of the aerosol. The results of individual particle analysis depict a complex event characterized by a first phase (P1) of massive input of BB carbonaceous particles (i.e., tar balls, popcorn refractory particles, and organic particles), and by a second phase (P2) dominated by inorganic salts. The peculiar feature of this BB event is the exceptionally large grain size of the subspherical organic particles at the beginning of the event with respect to the background. At these conditions a significant increase of the scattering efficiency may occur even for a small increase of the size parameter. Results of the simulation of the complex refractive indices (n‐ik) confirm this evaluation. Aerosol evolution during the event resulted from the combination of three distinct occurrences: (a) progressive rotation of air mass circulation toward non‐BB source areas, (b) development of a thick fog layer in the planetary boundary layer, and (c) sea salt spray direct advection of local/regional provenance
Variability in black carbon mass concentration in surface snow at Svalbard
Black carbon (BC) is a significant forcing agent in the Arctic, but substantial uncertainty remains to quantify its climate effects due to the complexity of the different mechanisms involved, in particular related to processes in the snowpack after deposition. In this study, we provide detailed and unique information on the evolution and variability in BC content in the upper surface snow layer during the spring period in Svalbard (Ny-Ålesund). A total of two different snow-sampling strategies were adopted during spring 2014 (from 1 April to 24 June) and during a specific period in 2015 (28 April to 1 May), providing the refractory BC (rBC) mass concentration variability on a seasonal variability with a daily resolution (hereafter seasonal/daily) and daily variability with an hourly sampling resolution (hereafter daily/hourly) timescales. The present work aims to identify which atmospheric variables could interact with and modify the mass concentration of BC in the upper snowpack, which is the snow layer where BC particles affects the snow albedo. Atmospheric, meteorological and snow-related physico-chemical parameters were considered in a multiple linear regression model to identify the factors that could explain the variations in BC mass concentrations during the observation period. Precipitation events were the main drivers of the BC variability during the seasonal experiment; however, in the high-resolution sampling, a negative association has been found. Snow metamorphism and the activation of local sources (Ny-Ålesund was a coal mine settlement) during the snowmelt periods appeared to play a non-negligible role. The statistical analysis suggests that the BC content in the snow is not directly associated to the atmospheric BC load
ACE-ASIA - Regional climatic and atmospheric chemical effects of Asian dust and pollution
Although continental-scale plumes of Asian dust and pollution reduce the amount of solar radiation reaching the earth's surface and perturb the chemistry of the atmosphere, our ability to quantify these effects has been limited by a lack of critical observations, particularly of layers above the surface. Comprehensive surface, airborne, shipboard, and satellite measurements of Asian aerosol chemical composition, size, optical properties, and radiative impacts were performed during the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) study. Measurements within a massive Chinese dust storm at numerous widely spaced sampling locations revealed the highly complex structure of the atmosphere, in which layers of dust, urban pollution, and biomass-burning smoke may be transported long distances as distinct entities or mixed together. The data allow a first-time assessment of the regional climatic and atmospheric chemical effects of a continental-scale mixture of dust and pollution. Our results show that radiative flux reductions during such episodes are sufficient to cause regional climate change
2014 iAREA campaign on aerosol in Spitsbergen – Part 2: Optical properties from Raman-lidar and in-situ observations at Ny-Ålesund
In this work multi wavelength Raman lidar data from Ny-Ålesund, Spitsbergen have been analysed for the spring 2014 Arctic haze season, as part of the iAREA campaign. Typical values and probability distributions for aerosol backscatter, extinction and depolarisation, the lidar ratio and the color ratio for 4 different altitude intervals within the troposphere are given. These quantities and their dependencies are analysed and the frequency of altitude-dependent observed aerosol events are given. A comparison with ground-based size distribution and chemical composition is performed. Hence the aim of this paper is to provide typical and statistically meaningful properties of Arctic aerosol, which may be used in climate models or to constrain the radiative forcing. We have found that the 2014 season was only moderately polluted with Arctic haze and that sea salt and sulphate were the most dominant aerosol species. Moreover the drying of an aerosol layer after cloud disintegration has been observed. Hardly any clear temporal evolution over the 4 week data set on Arctic haze is obvious with the exception of the extinction coefficient and the lidar ratio, which significantly decreased below 2 km altitude by end April. In altitudes between 2 and 5 km the haze season lasted longer and the aerosol properties were generally more homogeneous than closer to the surface. Above 5 km only few particles were found. The variability of the lidar ratio is discussed. It was found that knowledge of the aerosol’s size and shape does not determine the lidar ratio. Contrary to shape and lidar ratio, there is a clear correlation between size and backscatter: larger particles show a higher backscatter coefficient
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