Search results for "Mineral"

A Laboratory Dust Generator Applying Vibration to Soil Sample: Mineralogical Study and Compositional Analyses

2020

International audience; A laboratory study was carried out using a vibrating system (SyGAVib) to produce aerosols from four soils collected in the central Tunisian region around Sfax. The aim of this device is to mimic dust emission by natural wind erosion. Using compositional analysis, the dust produced was compared to (i) dust generated in a wind tunnel by the same soils, (ii) fine sieved and (iii) original bulk soils, and (iv) naturally occurring aerosol samples collected in the same area. The relative quartz content strongly decreases from bulk to fine soils, and again from fine soils to both wind tunnel and vibration‐generated aerosols. Compositional data analysis (CoDA) clearly shows …

A comprehensive laboratory study on the immersion freezing behavior of illite NX particles: a comparison of 17 ice nucleation measurement techniques

2015

Immersion freezing is the most relevant heterogeneous ice nucleation mechanism through which ice crystals are formed in mixed-phase clouds. In recent years, an increasing number of laboratory experiments utilizing a variety of instruments have examined immersion freezing activity of atmospherically relevant ice-nucleating particles. However, an intercomparison of these laboratory results is a difficult task because investigators have used different ice nucleation (IN) measurement methods to produce these results. A remaining challenge is to explore the sensitivity and accuracy of these techniques and to understand how the IN results are potentially influenced or biased by experimental param…

Single-particle characterization of ice-nucleating particles and ice particle residuals sampled by three different techniques

2015

Abstract. In the present work, three different techniques to separate ice-nucleating particles (INPs) as well as ice particle residuals (IPRs) from non-ice-active particles are compared. The Ice Selective Inlet (ISI) and the Ice Counterflow Virtual Impactor (Ice-CVI) sample ice particles from mixed-phase clouds and allow after evaporation in the instrument for the analysis of the residuals. The Fast Ice Nucleus Chamber (FINCH) coupled with the Ice Nuclei Pumped Counterflow Virtual Impactor (IN-PCVI) provides ice-activating conditions to aerosol particles and extracts the activated particles for analysis. The instruments were run during a joint field campaign which took place in January and …

Microphysical and optical properties of Arctic mixed-phase clouds. The 9 April 2007 case study.

2009

Abstract. Airborne measurements in Arctic boundary-layer stratocumulus were carried out near Spitsbergen on 9 April 2007 during the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) campaign. A unique set of co-located observations is used to describe the cloud properties, including detailed in situ cloud microphysical and radiation measurements along with airborne and co-located spaceborne remote sensing data (Lidar on Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations [CALIPSO] and radar on CloudSat satellites). The CALIPSO profiles evidence a cloud top temperature which varies between −24°C and −21°C. The in situ cloud observations reveal that the attenua…

2016

Abstract. Historic records of α-dicarbonyls (glyoxal, methylglyoxal), carboxylic acids (C6–C12 dicarboxylic acids, pinic acid, p-hydroxybenzoic acid, phthalic acid, 4-methylphthalic acid), and ions (oxalate, formate, calcium) were determined with annual resolution in an ice core from Grenzgletscher in the southern Swiss Alps, covering the time period from 1942 to 1993. Chemical analysis of the organic compounds was conducted using ultra-high-performance liquid chromatography (UHPLC) coupled to electrospray ionization high-resolution mass spectrometry (ESI-HRMS) for dicarbonyls and long-chain carboxylic acids and ion chromatography for short-chain carboxylates. Long-term records of the carbo…

δ13C variations in tree rings as an indication of severe changes in the urban air quality

2002

Abstract Annual growth rings sampled from three free-standing trees (Platanus hybrida sp.), grew in the metropolitan area of Palermo (Italy) and covering a 118 years time span (1880–1998), have been studied for their 13C/12C carbon isotope ratios. It has been found that the 13C/12C tree ring record, during the study time interval, decreased of −3.6‰, from −26.4‰ in 1880 to −30‰ in 1998. Such a progressive depletion has been attributed to the addition of anthropogenic 13C depleted carbon dioxide to the local atmosphere. The observed 13C/12C decrease has been used to infer some possible pathways of atmospheric CO2 change in the study urban area.

State of mixing, shape factor, number size distribution, and hygroscopic growth of the Saharan anthropogenic and mineral dust aerosol at Tinfou, Moro…

2009

The Saharan Mineral Dust Experiment (SAMUM) was conducted in May and June 2006 in Tinfou, Morocco. A H-TDMA system and a H-DMA-APS system were used to obtain hygroscopic properties of mineral dust particles at 85% RH. Dynamic shape factors of 1.11, 1.19 and 1.25 were determined for the volume equivalent diameters 720, 840 and 960 nm, respectively. During a dust event, the hydrophobic number fraction of 250 and 350 nm particles increased significantly from 30 and 65% to 53 and 75%, respectively, indicating that mineral dust particles can be as small as 200 nm in diameter. Log-normal functions for mineral dust number size distributions were obtained from total particle number size distributio…

Spatial distribution of aerosol microphysical and optical properties and direct radiative effect from the China Aerosol Remote Sensing Network

2019

Multi-year observations of aerosol microphysical and optical properties, obtained through ground-based remote sensing at 50 China Aerosol Remote Sensing Network (CARSNET) sites, were used to characterize the aerosol climatology for representative remote, rural, and urban areas over China to assess effects on climate. The annual mean effective radii for total particles (ReffT) decreased from north to south and from rural to urban sites, and high total particle volumes were found at the urban sites. The aerosol optical depth at 440 nm (AOD440 nm) increased from remote and rural sites (0.12) to urban sites (0.79), and the extinction Ångström exponent (EAE440–870 nm) increased fro…

The June 2007 Saharan dust event in the central Mediterranean: Observations and radiative effects in marine, urban, and sub-urban environments

2011

Abstract A desert dust episode in June 2007 and its radiative effects on the energy budget have been studied at three Italian stations (Rome, Lecce and Lampedusa) with the aim of investigating the interactions with different conditions and aerosol types over the Mediterranean. The three sites are representative for urban (Rome), sub-urban/rural (Lecce), and marine (Lampedusa) environment, respectively in the central Mediterranean region. Measured ground-based column-averaged aerosol optical properties and aerosol extinction profiles were used to initialize the MODTRAN4 radiative transfer model. The radiative transfer model was used to estimate the shortwave aerosol radiative forcing ( ARF )…

Aerosol columnar properties retrieved from CIMEL radiometers during VELETA 2002

2008

During the 2002 summer, the VELETA 2002 field campaign has been carried out at the Sierra Nevada Massif, close to Granada in South-Eastern Spain. During the campaign, CIMEL CE-318 robotic radiometer has been one of the key instruments in the characterization of the atmospheric aerosol columnar properties. This kind of radiometers have been operated at Motril, a coastal location at sea level, Pitres (1200 m a.s.l.), located in the South slope of Sierra Nevada Massif, Las Sabinas (2200m a.s.l.), located on the north slope of the mountain range, and Armilla (680m a.s.l.), located in the valley. The principal feature of the locations is that they provide a strong altitudinal gradient. This work…