Ash fall impact on vegetation: a remote sensing approach of the Oldoinyo Lengai 2007–08 eruption

Schutter, Ann De; Kervyn, Matthieu; Canters, Frank; Bosshard-Stadlin, Sonja A.; Songo, M.; Mattsson, Hannes B.

doi:10.1186/s13617-015-0032-z

Cited by 37 publications

(25 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Ashes used in this study were collected from Oldoinyo Lengai volcano which is located Tanzania, the Rift Valley at 2˚45'S, 35˚55'E and 2000 m above the Serengeti plains [35] [37]. Several samples of ashes were randomly collected from various places on top, medium and bottom of the mountain.…”

Section: Materials Collection and Preparationmentioning

confidence: 99%

“…Hence this current study aiming to investigate the removal of H 2 S and NH 3 from biogas using Oldoinyo Lengai volcanic ash (OLA) at ambient temperature conditions. The Oldoinyo Lengai is the only active natrocarbonatite volcano and it is a unique source of alkaline ash in the world; the OLA is abundant and readily available [35] [36] [37] [38]. The experiment was conducted on-site at The Banana investment company Ltd, Arusha, Tanzania where characteristics of H 2 S and NH 3 removal from biogas stream were determined at natural variation of biogas composition.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Oldoinyo Lengai Volcanic Ash for Removal of Hydrogen Sulfide and Ammonia from Biogas

Kandola¹,

Pogrebnoi²,

Pogrebnaya³

2018

MSCE

View full text Add to dashboard Cite

Oldoinyo Lengai mountain located in Northern Tanzania is the only active natrocarbonatite volcano with unusually alkali-rich natrocarbonatites which are not found elsewhere in the world. Volcanic ash formed earlier during eruptions was collected from different sites along the mountain, and its potency to adsorb hydrogen sulfide (H 2 S) and ammonia (NH 3) from biogas was investigated. The samples were calcinated at different temperatures (550˚C-850˚C) and were characterized by X-ray florescent, scanning electron microscopy and X-ray diffraction techniques. The on-site adsorption experiments were conducted at the biogas digester at ambient conditions. The calcinated ash was packed into the reactor bed, biogas allowed to pass through the adsorbent, and the inlet and outlet concentrations of H 2 S and NH 3 were measured. The height of the site where the adsorbent was taken from, calcination temperature, biogas flowrate and mass of the adsorbent were variable parameters and found to influence greatly on the efficiency of H 2 S and NH 3 removal. The efficiency is increased with calcination temperature raise and mass of adsorbent and decreased with flowrate increase. The samples collected from the top site of the mountain and calcinated at 850˚C exhibited the best sorption performance.

show abstract

Section: Materials Collection and Preparationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Oldoinyo Lengai Volcanic Ash for Removal of Hydrogen Sulfide and Ammonia from Biogas

Kandola¹,

Pogrebnoi²,

Pogrebnaya³

2018

MSCE

View full text Add to dashboard Cite

show abstract

“…An alternative modeling approach to tackle the question of vegetation colonization on lava flows would be to characterize and model the change in NDVI values for a recent lava surface relative to a climax vegetation representative for the environment and climate in which the lava flow was emplaced, as is often done for studies assessing vegetation recovery after forest fires (Gouveia et al ., ; Hope et al ., ). The reference point can be the NDVI value of the area before the lava was emplaced, for flows of the last decades (see De Schutter et al ., ), or existing pristine vegetation – area not impacted by lava emplacement in the last century – in similar environmental conditions to the lava flow surface. Although this would deserve further study, we expect that such an approach might be challenging for volcanoes with high density and frequency of lava flows and large gradients of vegetation with elevation and slope orientation.…”

Section: Discussionmentioning

confidence: 99%

Dating lava flows of tropical volcanoes by means of spatial modeling of vegetation recovery

Bakelants

Solana

et al. 2017

Earth Surf Processes Landf

Self Cite

View full text Add to dashboard Cite

The age of past lava flows is crucial information for evaluating the hazards and risks posed by effusive volcanoes, but traditional dating methods are expensive and time‐consuming. This study proposes an alternative statistical dating method based on remote sensing observations of tropical volcanoes by exploiting the relationship between lava flow age and vegetation cover. First, the factors controlling vegetation density on lava flows, represented by the normalized difference vegetation index (NDVI), were investigated. These factors were then integrated into pixel‐based multi‐variable regression models of lava flow age to derive lava flow age maps. The method was tested at a pixel scale on three tropical African volcanoes with considerable recent effusive activity: Nyamuragira (Democratic Republic of Congo), Mt Cameroon (Cameroon) and Karthala (the Comoros). Due to different climatic and topographic conditions, the parameters of the spatial modeling are volcano‐specific. Validation suggests that the obtained statistical models are robust and can thus be applied for estimating the age of unmodified undated lava flow surfaces for these volcanoes. When the models are applied to fully vegetated lava flows, the results should be interpreted with caution due to the saturation of NDVI. In order to improve the accuracy of the models, when available, spatial data on temperature and precipitation should be included to directly represent climatic variation. Copyright © 2017 John Wiley & Sons, Ltd.

show abstract

“…Because the initial status is often unknown, a positive slope may be thought to represent either a recovery from drought (Vicente‐Serrano et al, ), greening trends as a function of both climatic and nonclimatic factors (Xiao & Moody, ), a response to other disturbances such as fire events (Diaz‐Delgado, Salvador, & Pons, ; Gouveia, Bastos, Trigo, & DaCamara, ; Riaño et al, ), or a permanent land‐use change generating higher primary productivity than the previous situation, such as afforestation (Li, ; Vasallo, Dieguez, Garbulsky, Jobbágy, & Paruelo, ). A negative slope, on the other hand, might represent a downwards trend due to either a long‐lasting drought (Anyamba & Tucker, ), more abrupt shocks such as volcanic ash fallout (de Schutter et al, ), or permanent disturbances such as land use change, for example, resulting in a decrease of irrigated areas (Gumma et al, ). Both phases and regime shifts are confounded in the same process when NDVI changes are depicted by a linear trend.…”

Section: Introductionmentioning

confidence: 99%

Phases or regimes? Revisiting NDVI trends as proxies for land degradation

et al. 2018

View full text Add to dashboard Cite

One of the main challenges in land degradation assessment is that a rigorous and systematic approach to addressing its complex dynamics is still missing. The development and application of operative tools at regional and global scales remain a challenge. Land degradation is usually defined as a long‐term decline in ecosystem function and productivity. Due to its temporal and spatial resolution as well as data availability, the use of time series of spectral vegetation indexes obtained from satellite sensors has become frequent in recent studies in this field. Slope of linear trends of the normalized difference vegetation index is usually considered an accurate indicator and is widely used as a proxy for land degradation. Yet this method is built on a number of simplifying conceptual and methodological assumptions that prevent capturing more complex dynamics, such as cyclic or periodic behaviors. Our aim was to examine the limitations associated with using linear normalized difference vegetation index trends as proxies for land degradation by comparing outcomes with an alternative methodological procedure based on wavelet autoregressive methods. We explored these issues in 5 case studies from Africa and South America. We observed that trend explained a marginal portion of total temporal variability, whereas monotonic functions, such as linear trends, were unable to capture dynamics that were non‐unidirectional, resulting in misinterpretation of actual trends. Wavelet autoregressive method results were encouraging as a step towards the application of more accurate methods to provide sound scientific information of land degradation and restoration.

show abstract

Ash fall impact on vegetation: a remote sensing approach of the Oldoinyo Lengai 2007–08 eruption

Cited by 37 publications

References 51 publications

Oldoinyo Lengai Volcanic Ash for Removal of Hydrogen Sulfide and Ammonia from Biogas

Oldoinyo Lengai Volcanic Ash for Removal of Hydrogen Sulfide and Ammonia from Biogas

Dating lava flows of tropical volcanoes by means of spatial modeling of vegetation recovery

Phases or regimes? Revisiting NDVI trends as proxies for land degradation

Contact Info

Product

Resources

About