scholarly journals Cyanobacterial Potential for Restoration of Loess Surfaces through Artificially Induced Biocrusts

2020 ◽  
Vol 11 (1) ◽  
pp. 66
Author(s):  
Tamara Palanački Malešević ◽  
Tamara Dulić ◽  
Igor Obreht ◽  
Zorana Trivunović ◽  
Rastko Marković ◽  
...  
Keyword(s):  
Vascular Plant ◽  
Water Systems ◽  
Dust Particles ◽  
Wind Speeds ◽  
Positive Effects ◽  
Loess Particles ◽  
Combating Desertification ◽  
Aeolian Sediment ◽  
Loess Sediment ◽  
Highly Porous

Loess is a highly porous and easily erosive aeolian sediment covering approximately 10% of the Earth’s surface. The weak vegetation cover and high wind speeds in many of these regions make loess sediment the main source of dust in the atmosphere. Dust particles deteriorate air quality and affect soils, crops, water systems, and animal and human health. The commonly used method for combating desertification is revegetation. However, planting various vascular plant species in loess landscapes did not show any long-lasting positive effects. This study aims to assess the potential of cyanobacterial strains for the restoration of exposed loess surfaces through the assisted development of biological loess crusts (BLCs). Isolated cyanobacterial loess strains were screened for the traits (toxicity, biomass and polysaccharide production) desirable for their use in restoration purposes. By simulating semi-arid environmental conditions in specially designed chambers, the potential of cyanobacterial loess strains for assisted development of BLCs and the mechanisms of loess stabilization have been evaluated by chlorophyll a accumulation and microscopic examination. It was confirmed that cyanobacteria have the ability to interact with loess particles resulting in BLC formation, which keeps the particles immobilized and the sediment below the particles stabilized.

Microscale pattern of vascular plant distribution in two high arctic plant communities

1984 ◽  
Vol 62 (10) ◽  
pp. 2033-2042 ◽  
Author(s):  
E. H. Sohlberg ◽  
L. C. Bliss
Keyword(s):  
Distribution Pattern ◽  
Vascular Plants ◽  
Vascular Plant ◽  
Extreme Environments ◽  
Niche Differentiation ◽  
Bare Soil ◽  
High Arctic ◽  
Plant Distribution ◽  
Wind Speeds ◽  
Point Quadrat

Microscale pattern is of crucial importance in determining the distribution of vascular plants in the extreme environments of the High Arctic. Point-quadrat analysis of the distribution of the vascular plants in a mesic cryptogam–herb meadow and a xeric Puccinellia barren found a nonrandom distribution of vascular species. Most species were found growing in moss turfs versus crustose lichen or bare soil surfaces in the meadow and in desiccation cracks in the barren. Two species showed an opposite distribution pattern in the meadow indicating that incipient niche differentiation occurs in the High Arctic. Quadrat sampling showed that seed distribution was random in the meadow and only slightly skewed toward cracks in the barren. Microsites appeared to be crucial to the seedling establishment and adult distribution pattern for Papaver radicatum but less important for Ranunculus sabinei. Microclimate analyses showed that soil temperatures were higher, wind speeds were lower, soil moisture content was greater, and nitrate levels were higher in the microsites usually preferred by plants.

scholarly journals Measurements of dust deposition velocity in a wind-tunnel experiment

2014 ◽  
Vol 14 (7) ◽  
pp. 9439-9474 ◽  
Author(s):  
J. Zhang ◽  
Y. Shao ◽  
N. Huang
Keyword(s):  
Wind Tunnel ◽  
Deposition Velocity ◽  
Wind Tunnel Experiment ◽  
Dust Particles ◽  
Dust Deposition ◽  
Wind Speeds ◽  
Deposition Velocities ◽  
Development And Validation ◽  
Single Instrument ◽  
Entire Dataset

Abstract. In this study, we present the results of a wind-tunnel experiment on dust deposition. A new method is proposed to derive dust deposition velocity from the PDA (Particle Dynamics Analysis) particle-velocity and particle-size measurements. This method has the advantage that the motions of individual dust particles are directly observed and all relevant data for computing dust deposition velocity is collected using a single instrument, and therefore the measurement uncertainties are reduced. The method is used in the wind-tunnel experiment to measure the dust deposition velocities for different particle sizes, wind speeds and surface conditions. For a sticky-smooth wood surface and a water surface, the observed dust deposition velocities are compared with the predictions using a dust deposition scheme, and the entire dataset is compared with the data found in the literature. From the wind-tunnel experiments, a relatively reliable dataset of dust deposition velocity is obtained, which is of considerable value for the development and validation of dust deposition schemes.

Aeolian processes on Venus: Probabilistic study on threshold speeds

2021 ◽  
Author(s):  
Ananyo Bhattacharya
Keyword(s):  
Wind Shear ◽  
Experimental Models ◽  
Dust Particles ◽  
Wind Speeds ◽  
Probabilistic Study ◽  
Dust Lifting ◽  
Entrainment Process ◽  
Haze Formation ◽  
Topography Data

<p>Dust particles and haze formation on the surface of Venus have been observed and studied using several independent techniques onboard Venus lander missions. A possibility of mineral haze formation in highlands is supported by observations of high reflectivity and low emissivity features from Pioneer Venus Orbiter and Magellan radar experiments, while Venera 13 and 14 spectrophotometer analysis yields appreciable aerosol extinction at the same altitudes. In this work, we present threshold parameters for dust lifting from 1 μm to 1 cm sized dust particles over the globe using emissivity and surface topography data provided by Magellan radar. The threshold wind speeds have been derived using theoretical and experimental models and compared with the in-situ measurements reported earlier. Haze formation is less likely to occur solely due to wind shear by micron and submicron sized particles. The entrainment process and properties of the boundary layer also contribute to variation in threshold wind speeds and particle transport.</p>

scholarly journals Anthropogenic fire, vegetation structure and ethnobotanical uses in an alpine shrubland of Nepal’s Himalaya

2020 ◽  
Vol 29 (3) ◽  
pp. 201
Author(s):  
Asha Paudel ◽  
Scott H. Markwith ◽  
Katie Konchar ◽  
Mani Shrestha ◽  
Suresh K. Ghimire
Keyword(s):  
Species Richness ◽  
Indicator Species ◽  
Vascular Plant ◽  
Elevational Gradient ◽  
Plant Species Richness ◽  
Anthropogenic Fire ◽  
Positive Effects ◽  
Central Nepal ◽  
Ethnobotanical Uses ◽  
The Himalaya

Alpine vegetation of the Himalaya is used as food, medicine or fodder, and is commonly managed with fire by agropastoralists. Prescribed fire can have positive effects on rangeland biodiversity, but studies evaluating its effects in alpine shrublands are scarce. Our objective was to examine the effects of anthropogenic fire on biophysical characteristics, species richness, abundance and composition in an alpine shrubland with socioeconomic value to local peoples in Langtang National Park in central Nepal. We surveyed biophysical variables, vascular plant species richness and composition along three transects at ascending elevations, and conducted interviews with local people and park officials on the use of fire in the region. We found 69 species of vascular plants in 89 plots; species richness was greater in burned plots and with increasing elevation, with 13 species unique to burned plots. We identified 14 indicator species in both burned and unburned plots; eight of them were Himalayan endemics. In burned plots, the indicator species were predominantly grasses and perennial forbs with ethnobotanical uses. This is the first detailed study on alpine shrubland anthropogenic fire in the Nepalese Himalaya. Burning may, at least temporarily, replace woody with more palatable herbaceous species, and weaken the elevational gradient of the shrubland.

scholarly journals Measurements of dust deposition velocity in a wind-tunnel experiment

2014 ◽  
Vol 14 (17) ◽  
pp. 8869-8882 ◽  
Author(s):  
J. Zhang ◽  
Y. Shao ◽  
N. Huang
Keyword(s):  
Wind Tunnel ◽  
Deposition Velocity ◽  
Wind Tunnel Experiment ◽  
Dust Particles ◽  
Dust Deposition ◽  
Data Set ◽  
Wind Speeds ◽  
Deposition Velocities ◽  
Development And Validation ◽  
Single Instrument

Abstract. In this study, we present the results of a wind-tunnel experiment on dust deposition. A new method is proposed to derive dust deposition velocity from PDA (particle dynamics analysis) particle-velocity and particle-size measurements. This method has the advantage that the motions of individual dust particles are directly observed and all relevant data for computing dust deposition velocity is collected using a single instrument, and thus the measurement uncertainties are reduced. The method is used in the wind-tunnel experiment to measure dust deposition velocities for different particle sizes, wind speeds and surface conditions. For sticky-smooth wood and water surfaces, the observed dust deposition velocities are compared with the predictions using a dust deposition scheme, and the entire data set is compared with the data found in the literature. From the wind-tunnel experiments, a relatively reliable data set of dust deposition velocities is obtained, which is valuable for the development and validation of dust deposition schemes.

scholarly journals The mineral dust cycle in EMAC 2.40: sensitivity to the spectral resolution and the dust emission scheme

2011 ◽  
Vol 11 (10) ◽  
pp. 27285-27325
Author(s):  
G. Gläser ◽  
A. Kerkweg ◽  
H. Wernli
Keyword(s):  
Atmospheric Chemistry ◽  
Mineral Dust ◽  
Dust Emission ◽  
Dust Particles ◽  
Global Maximum ◽  
Polar Regions ◽  
Model Resolution ◽  
Dust Source ◽  
Wind Speeds ◽  
Grid Points

Abstract. This first detailed analysis of the mineral dust cycle in the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model system investigates the performance of two dust emission schemes, following the approach of Balkanski et al. (2004) and Tegen et al. (2002), respectively, and the influence of the horizontal model resolution. Here the spectral resolutions T42, T63, T85, and T106 are investigated. A basic sulphur chemistry, enabling the coating of insoluble dust particles to make them soluble, is employed in order to realistically describe the scavenging and wet deposition of mineral dust. Independent of the dust emission scheme the five-year simulations with the horizontal resolutions T42 and T63 produce unrealistically high emissions at some grid points in the Tarim Basin in Central Asia, leading to very high dust loads in polar regions. In these coarse resolutions dust source grid points in the basin and elevated grid points of the Himalayas with high wind speeds can not be distinguished, causing this overestimation. In T85 and T106 these regions are well separated and considerably less dust is emitted there. With the chosen model setup, the dust emission scheme by Balkanski et al. (2004) places the global maximum of emissions in the Thar Desert in India. This is unrealistic as the Sahara Desert is known to be the largest dust source in the world. This is the main deficiency of this scheme compared to the one by Tegen et al. (2002), which produces very reasonable distributed emissions and dust loads in simulations with resolutions T85 and T106. For future climate simulations with EMAC that focus on mineral dust, we recommend to use the dust emission scheme by Tegen et al. (2002), and a model resolution of at least T85. Simulations of two selected episodes and comparison to observational data sets show that in this model configuration EMAC is able to realistically simulate also intense, episodic events of dust emission and long-range transport.

scholarly journals The relationships between biodiversity and ecosystem services and the effects of grazing cessation in semi-natural grasslands

Web Ecology ◽  
2018 ◽  
Vol 18 (1) ◽  
pp. 55-65 ◽  
Author(s):  
Sølvi Wehn ◽  
Knut Anders Hovstad ◽  
Line Johansen
Keyword(s):  
Species Richness ◽  
Ecosystem Services ◽  
Plant Species ◽  
Vascular Plant ◽  
Plant Species Richness ◽  
Positive Effects ◽  
Control Climate ◽  
Vascular Plant Species ◽  
Natural Grasslands ◽  
Natural Grassland

Abstract. Land use change can affect biodiversity, and this has an impact on ecosystem services (ESs), but the relationships between biodiversity and ESs are complex and poorly understood. Biodiversity is declining due to the abandonment of extensively grazed semi-natural grasslands. We therefore aim to explore relationships between biodiversity and ESs provided by extensively managed semi-natural grasslands. Focusing on vascular plant species richness, as well as the ESs fodder quantity, quality, and stability, allergy control, climate regulation, nutrient cycling, pollination, and aesthetic appreciation, we carried out botanical field surveys of 28 paired extensively grazed and abandoned semi-natural grassland plots, with four subplots of 4 m2 in each plot. The management of the semi-natural grasslands is and has been at low intensity. We calculated the influence of abandonment on the ES indicators, measured the correlation between the biodiversity measure of vascular plant species richness and ES indicators, and finally determined how the relationships between plant species richness and the ES indicators were affected by the cessation of the extensive management. ES indicators are often, but not always, positively correlated with species richness. Cessation of extensive grazing has both negative and positive effects on ES indicators but the relationships between species richness and ES indicators are often different in extensively managed and abandoned semi-natural grasslands. The relationships between species richness and ES indicators are less pronounced in the extensively managed semi-natural grassland than for the abandoned. One possible reason for this outcome is high functional redundancy in the extensively managed semi-natural grasslands.

La-Ce-Y-W Cathodes Application for High Temperature Electrostatic Precipitator

2010 ◽  
Vol 113-116 ◽  
pp. 437-441 ◽  
Author(s):  
Zhong Zhu Gu ◽  
Jian Can Yang ◽  
Xiao Li Xi ◽  
Zuo Ren Nie ◽  
Jin Jin Xu
Keyword(s):  
Electron Emission ◽  
Flue Gas ◽  
Electrostatic Precipitator ◽  
Average Diameter ◽  
Dust Particles ◽  
Effective Work ◽  
Effective Work Function ◽  
Positive Effects ◽  
Precipitation Efficiency ◽  
Microstructure Of The Material

La-Y-Ce-W cathode was prepared by powder metallurgy. XRD, OM, SEM and EDS were applied to analyze the microstructure of the material. La, Ce and Y concentrate on the tungstate particles and exist as Rare Earth (RE) tungstate. The average diameter of the particles is about 30µm. The electron emission properties were measured with self-designed electron emitter surveyor. Its effective work function was 2.76eV at 1300°C. The precipitation efficiency of an electrostatic precipitator (ESP) installed with the cathode was investigated in a certain flue gas condition. It was found that it can trap over 95% dust particles with diameter bigger than 1µm. As to dust particles with diameter smaller than 0.1µm, the efficiency is lower than 85%. Increasing collection voltages showed greater positive effects on the precipitation efficiency of smaller particles than that of larger particles.

Saturn's E, G and F rings: modulated by the plasma sheet

1984 ◽  
Vol 75 ◽  
pp. 597
Author(s):  
E. Grün ◽  
G.E. Morfill ◽  
T.V. Johnson ◽  
G.H. Schwehm
Keyword(s):  
Solar Wind ◽  
Direct Contact ◽  
Transport Processes ◽  
Time Variable ◽  
Dust Particles ◽  
Spatial Diffusion ◽  
Drag Forces ◽  
Orbit Perturbation ◽  
Time Variations ◽  
F Ring

ABSTRACTSaturn's broad E ring, the narrow G ring and the structured and apparently time variable F ring(s), contain many micron and sub-micron sized particles, which make up the “visible” component. These rings (or ring systems) are in direct contact with magnetospheric plasma. Fluctuations in the plasma density and/or mean energy, due to magnetospheric and solar wind processes, may induce stochastic charge variations on the dust particles, which in turn lead to an orbit perturbation and spatial diffusion. It is suggested that the extent of the E ring and the braided, kinky structure of certain portions of the F rings as well as possible time variations are a result of plasma induced electromagnetic perturbations and drag forces. The G ring, in this scenario, requires some form of shepherding and should be akin to the F ring in structure. Sputtering of micron-sized dust particles in the E ring by magnetospheric ions yields lifetimes of 102to 104years. This effect as well as the plasma induced transport processes require an active source for the E ring, probably Enceladus.

Analytical Electron Microscopy Characterization of Electric Arc Furnace Dust

1981 ◽  
Vol 39 ◽  
pp. 134-135
Author(s):  
J. R. Porter ◽  
J. I. Goldstein ◽  
D. B. Williams
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Electric Arc Furnace ◽  
Electric Arc ◽  
Dust Particles ◽  
Particle Analysis ◽  
Arc Furnace ◽  
Analytical Electron ◽  
Residual Elements ◽  
Industry Practice

Alloy scrap metal is increasingly being used in electric arc furnace (EAF) steelmaking and the alloying elements are also found in the resulting dust. A comprehensive characterization program of EAF dust has been undertaken in collaboration with the steel industry and AISI. Samples have been collected from the furnaces of 28 steel companies representing the broad spectrum of industry practice. The program aims to develop an understanding of the mechanisms of formation so that procedures to recover residual elements or recycle the dust can be established. The multi-phase, multi-component dust particles are amenable to individual particle analysis using modern analytical electron microscopy (AEM) methods.Particles are ultrasonically dispersed and subsequently supported on carbon coated formvar films on berylium grids for microscopy. The specimens require careful treatment to prevent agglomeration during preparation which occurs as a result of the combined effects of the fine particle size and particle magnetism. A number of approaches to inhibit agglomeration are currently being evaluated including dispersal in easily sublimable organic solids and size fractioning by centrifugation.

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