Enhanced Weathering and Erosion of a Cohesive Shore Platform Following the Experimental Removal of Mussels

The organisms inhabiting intertidal platforms can affect their weathering and erosion rates. Research on biotic influences on platform integrity has traditionally emphasized the role of bioeroders (i.e., organisms that scrap or bore into platforms via mechanical and chemical means). Yet, recent studies illustrate that covers of sessile organisms on the surfaces of intertidal platforms can have bioprotective effects by reducing the efficacy of physical weathering and erosion agents. Eroding cliffs fronted by cohesive shore platforms are a pervasive feature along the continental Argentinean coastline (37–52°S). In this study, we investigated how mussel (Brachidontes rodriguezii) cover mediates weathering and erosion of a cohesive, consolidated silt platform at Playa Copacabana (5 km north of Miramar, Buenos Aires Province; 38° 14′ S, 57° 46′ W). By means of mussel removal experiments, we found that mussel cover attenuates variations in platform surface temperatures, enhances moisture retention during low tide, reduces rates of salt crystallization within the pores of the platform material, and attenuates hydrodynamic forcing on the platform surface. Mussel removal also led to a 10% decrease in surface hardness and a 2-mm reduction in platform height after 5 months. Collectively, our findings indicate that mussel beds limit substrate breakdown via heating-cooling, wetting-drying, and salt crystallization and provide some of the first experimental field evidence for the direct impacts of biotic cover on platform erosion. As intertidal platforms protect the cliffs behind from the hydraulic impact of waves, which may be enhanced with future sea-level rise, we posit that the protection of platforms by mussels indirectly moderates coastline retreat, especially on soft cohesive shores.

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Sewage sludge as a precursor of adsorbents/catalysts for environmental applications

Water Practice & Technology ◽

10.2166/wpt.2007.019 ◽

2007 ◽

Vol 2 (1) ◽

Author(s):

A. Ros ◽

C. Canals-Batlle ◽

M.A. Lillo-Ródenas ◽

E. Fuente ◽

M. A. Montes-Morán ◽

...

Keyword(s):

Sewage Sludge ◽

Room Temperature ◽

Waste Water Treatment ◽

Textural Properties ◽

Active Species ◽

Elemental Sulphur ◽

Gaseous Emissions ◽

Removal Experiments ◽

Catalytically Active

This paper focuses on the valorisation of solid residues obtained from the thermal treatment of sewage sludge. In particular, sewage sludge samples were collected from two waste water treatment plants (WWTPs) with different sludge line basic operations. After drying, sludges were heated up to 700 °C in appropriate ovens under diluted air (gasification) and inert (pyrolysis) atmospheres. The solids obtained, as well as the dried (raw) sludges, were characterised to determine their textural properties and chemical composition, including the speciation of their inorganic fraction. All the materials under study were employed as adsorbents/catalysts in H2S removal experiments at room temperature. It was found that, depending on the particular sludge characteristics, outstanding results can be achieved both in terms of retention capacities and selectivity. Some of the solids outperform commercially available sorbents specially designed for gaseous emissions control. In these adsorbents/catalysts, H2S is selectively oxidised to elemental sulphur most likely due to the presence of inorganic, catalytically active species. The role of the carbon-enriched part on these solids is also remarked.

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Biomonitoring of Heavy Metals: The Unexplored Role of Marine Sessile Taxa

Applied Sciences ◽

10.3390/app11020580 ◽

2021 ◽

Vol 11 (2) ◽

pp. 580

Author(s):

Camilla Roveta ◽

Anna Annibaldi ◽

Afghan Afghan ◽

Barbara Calcinai ◽

Cristina Gioia Di Camillo ◽

...

Keyword(s):

Heavy Metals ◽

Current Knowledge ◽

Marine Species ◽

Shallow Waters ◽

Anthropogenic Inputs ◽

Current Review ◽

European Water ◽

To Receive ◽

Sessile Organisms

Coastal areas are known to receive significant anthropogenic inputs, mainly deriving from metropolitan areas, industries, and activities related to tourism. Among these inputs, some trace elements are listed as priority pollutants in the European Water Framework Directive, due to their ability to bioaccumulate in organisms. Many studies have been conducted on heavy metals (HMs) accumulation and on their possible effects on different edible marine species. While the most studied sessile organisms are bivalves, in the current review, we focus our attention on other sessile taxa (sponges, cnidarians, bryozoans, polychaetes, cirripeds, and tunicates), proposed as bioindicators in coastal shallow waters. Although their potential as bioindicator tools has been repeatedly highlighted in the literature, these organisms are still poorly investigated and considered for monitoring. In this context, we analyze the available literature about this topic, in order to summarize the current knowledge and identify possible applications of these organisms in a bioremediation scenario.

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Has erosion globally increased? Long-term erosion rates as a function of climate derived from the impact crater inventory

10.5194/esurf-2018-59 ◽

2018 ◽

Author(s):

Stefan Hergarten ◽

Thomas Kenkmann

Keyword(s):

Time Scale ◽

Impact Crater ◽

Regional Effect ◽

Tropical Zone ◽

Erosion Rates ◽

Continental Scale ◽

River Loads ◽

The Impact

Abstract. Worldwide erosion rates seem to have increased strongly since the beginning of the Quaternary, but there is still discussion about the role of glaciation as a potential driver and even whether the increase is real at all or an artefact due to losses in the long-term sedimentary record. In this study we derive estimates of average erosion rates on the time scale of some tens of million years from the terrestrial impact crater inventory. This approach is completely independent from all other methods to infer erosion rates such as river loads, preserved sediments, cosmogenic nuclides and thermochronometry. Our approach yields average erosion rates as a function of present-day topography and climate. The results confirm that topography accounts for the main part of the huge variation of erosion on Earth, but also identifies a significant systematic dependence on climate in contrast to several previous studies. We found a fivefold increase in erosional efficacy from the cold regimes to the tropical zone and that temperate and arid climates are very similar in this context. Combining our results to a worldwide mean erosion rate we found that erosion rates on the time scale of some tens of million years are at least as high as present-day rates and suggest that glaciation has a rather regional effect with a limited impact at the continental scale.

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The role of freezing-thaw cycling in rock samples topography evolution and rock cliff retreat

10.5194/egusphere-egu21-8304 ◽

2021 ◽

Author(s):

Li Fei ◽

Marc-Henri Derron ◽

Tiggi Choanji ◽

Michel Jaboyedoff ◽

Chunwei Sun ◽

...

Keyword(s):

Freezing Point ◽

Meteorological Data ◽

Test Chamber ◽

Monitoring Program ◽

Dynamic Environment ◽

Rock Properties ◽

Rock Surface ◽

Physical Weathering ◽

Rock Samples

Freezing-thaw weathering is recognized as one of the most significant factors in the fatigue of rock mass in areas where the temperature periodically fluctuates around the freezing point.&#160; A one-year monthly SfM monitoring program from December 19, 2019, to January 7, 2021, was done to detect rockfall activity on a rockslide cliff composed of marl-sandstone at La Cornalle, Switzerland. More than one hundred rockfall events were detected during this period with the volumes varied from 0.005m3 to 4.85m3.&#160; We texture all the rockfalls on the 3D SfM model. It is shown that most of them are mainly located in three areas: &#160;the top of the cliff, the foot of the cliff, and the medium-left part of the cliff. The common feature of these three parts is that the layers are more or less overhanging with dense fractures around them. At the same time, the meteorological data collected by a weather station on site is correlated with the rockfall events to figure out the relationship between each other. Actually, about 30% of total rockfall volume fell during winter on this site. The triggering factor of rockfall during winter is related to freezing-thaw cycling. This kind of weathering can be understood as an interplay between rock properties and its dynamic environment. In order to make clear the role of freezing-thaw played on the rockfall generation, an on-site 24h monitoring measurement program that consists of two crack meters, one rock thermal sensor, and thermal camera monitoring is installed in January 2021. Those datasets will help to understand how the crack grows with the changing temperature. In addition, freezing-thaw cycling laboratory experiments for the rock samples taken from different areas of the cliff will be done with an environmental test chamber. The topography of the rock samples before and after the experiments will be acquired by a 3D handheld scanner. This work will benefit to reveal the rock surface evolution during the freezing-thaw cycling in a dynamic environment with varied humidity and number of cycles.&#160; In conclusion, the combination of on-site measurements and laboratory freezing-thaw experiments will provide a good basis for a better understanding of the rockfall triggering mechanism led by physical weathering.

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The role of erosion in the morphometry of composite volcanoes

10.5194/egusphere-egu21-14500 ◽

2021 ◽

Author(s):

Roos van Wees ◽

Pierre-Yves Tournigand ◽

Daniel O’Hara ◽

Pablo Grosse ◽

Gabor Kereszturi ◽

...

Keyword(s):

Fractal Dimension ◽

Age Determination ◽

Morphometric Parameters ◽

Physical Weathering ◽

Erosion Rates ◽

Erosion Processes ◽

Digital Elevation ◽

Shape Complexity ◽

Geochronological Constraints ◽

Natural Composite

Volcanoes are extremely dynamic landforms. They grow by the accumulation of eruptive products and intrusions and degrade by a range of erosion processes such as superficial runoff, chemical and physical weathering, fluvial and glacial incision, and mass movements. In this study, we aim at documenting and quantifying the morphology of natural composite volcanoes using a range of morphometric indices, to better understand the factors that control erosion rates and patterns.In addition to standard morphometric indices, including edifice ellipticity and irregularity, computed by the MORVOLC algorithm, a fractal dimension tool is developed to quantitatively report the shape complexity of stratovolcanoes. A convex hull approach is used to derive minimal erosion volumes and estimate erosion rates, considering available geochronological constraints. Morphometric parameters are derived from digital elevation models (DEMs) for a few exemplary stratovolcanoes of contrasted ages from the same volcanic region. To analyse the potential bias induced by the selected DEMs and the identification of the volcanic edifice outline, we also conduct a sensitivity analysis. The morphometric parameters are similarly extracted using the freely and globally available ALOS 30m (AW3D30), SRTM 30m (SRTMGL1), and ASTER 30m (GDEM 003), and compared to values obtained with the TanDEM-X 12m. The subjective user-drawn edifice outlines are compared to outlines generated by available algorithms, i.e. NETVOLC and MBOA, and their impact on the accuracy of morphometric indexes is quantified. &#160;Our results highlight that erosion increases edifice irregularity and fractal dimension. Preliminary trends between volcano fractal dimension, eroded volume, and age suggest that fractal analysis has the potential to be used as a relative age determination tool. The proposed morphometric characterisation paves the way for a comparison between natural volcanoes and controlled lab experiments reproducing the degradation of pristine volcanic cones by surface runoff to be developed later in our project. &#160;

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Mechanistic Observations on the Role of the Stannous Ion in Caries Lesion De- and Remineralization

Caries Research ◽

10.1159/000446849 ◽

2016 ◽

Vol 50 (4) ◽

pp. 378-382 ◽

Cited By ~ 4

Author(s):

Frank Lippert

Keyword(s):

Factorial Design ◽

Surface Hardness ◽

Acid Resistance ◽

Design Studies ◽

Mineral Distribution ◽

Caries Lesion ◽

Stannous Ion ◽

Ph Dependent

Two mechanistic, laboratory, factorial design studies were conducted to investigate the effect of the stannous ion (Sn2+) in the absence or presence of fluoride on caries lesion de- and remineralization. Study I was concerned with determining changes in mineral distribution of subsurface lesions, whereas study II investigated changes in surface hardness of surface-softened lesions as a function of pH. Study I showed that Sn2+ modulates the effects of fluoride by preventing lamination. Study II revealed that the effect of Sn2+ on rehardening is pH dependent. Neither study demonstrated synergy between Sn2+ and fluoride, yet interactions were observed. Sn2+ does interfere with remineralization to some extent although it provided acid resistance. The role of Sn2+ in the caries process is complex.

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Long-term erosion rates as a function of climate derived from the impact crater inventory

Earth Surface Dynamics ◽

10.5194/esurf-7-459-2019 ◽

2019 ◽

Vol 7 (2) ◽

pp. 459-473 ◽

Cited By ~ 2

Author(s):

Stefan Hergarten ◽

Thomas Kenkmann

Keyword(s):

Impact Crater ◽

Fold Increase ◽

Regional Effect ◽

Tropical Zone ◽

Erosion Rates ◽

Continental Scale ◽

River Loads ◽

The Impact

Abstract. Worldwide erosion rates seem to have increased strongly since the beginning of the Quaternary, but there is still discussion about the role of glaciation as a potential driver and even whether the increase is real at all or an artifact due to losses in the long-term sedimentary record. In this study we derive estimates of average erosion rates on the timescale of some tens of millions of years from the terrestrial impact crater inventory. This approach is completely independent from all other methods to infer erosion rates such as river loads, preserved sediments, cosmogenic nuclides, and thermochronometry. Our approach yields average erosion rates as a function of present-day topography and climate. The results confirm that topography accounts for the main part of the huge variation in erosion on Earth, but also identifies a significant systematic dependence on climate in contrast to several previous studies. We found a 5-fold increase in erosional efficacy from the cold regimes to the tropical zone and that temperate and arid climates are very similar in this context. Combining our results into a worldwide mean erosion rate, we found that erosion rates on the timescale of some tens of millions of years are at least as high as present-day rates and suggest that glaciation has a rather regional effect with a limited impact at the continental scale.

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Arctic–alpine blockfields in the northern Swedish Scandes: late Quaternary – not Neogene

Earth Surface Dynamics ◽

10.5194/esurf-2-383-2014 ◽

2014 ◽

Vol 2 (2) ◽

pp. 383-401 ◽

Cited By ~ 10

Author(s):

B. W. Goodfellow ◽

A. P. Stroeven ◽

D. Fabel ◽

O. Fredin ◽

M.-H. Derron ◽

...

Keyword(s):

Chemical Weathering ◽

Late Quaternary ◽

Time Frame ◽

Temporal Variations ◽

Early Pleistocene ◽

Slope Position ◽

Physical Weathering ◽

Weathering Processes ◽

Erosion Rates ◽

Surrounding Landscape

Abstract. Autochthonous blockfield mantles may indicate alpine surfaces that have not been glacially eroded. These surfaces may therefore serve as markers against which to determine Quaternary erosion volumes in adjacent glacially eroded sectors. To explore these potential utilities, chemical weathering features, erosion rates, and regolith residence durations of mountain blockfields are investigated in the northern Swedish Scandes. This is done, firstly, by assessing the intensity of regolith chemical weathering along altitudinal transects descending from three blockfield-mantled summits. Clay / silt ratios, secondary mineral assemblages, and imaging of chemical etching of primary mineral grains in fine matrix are each used for this purpose. Secondly, erosion rates and regolith residence durations of two of the summits are inferred from concentrations of in situ-produced cosmogenic 10Be and 26Al in quartz at the blockfield surfaces. An interpretative model is adopted that includes temporal variations in nuclide production rates through surface burial by glacial ice and glacial isostasy-induced elevation changes of the blockfield surfaces. Together, our data indicate that these blockfields are not derived from remnants of intensely weathered Neogene weathering profiles, as is commonly considered. Evidence for this interpretation includes minor chemical weathering in each of the three examined blockfields, despite consistent variability according to slope position. In addition, average erosion rates of ~16.2 and ~6.7 mm ka−1, calculated for the two blockfield-mantled summits, are low but of sufficient magnitude to remove present blockfield mantles, of up to a few metres in thickness, within a late Quaternary time frame. Hence, blockfield mantles appear to be replenished by regolith formation through, primarily physical, weathering processes that have operated during the Quaternary. The persistence of autochthonous blockfields over multiple glacial–interglacial cycles confirms their importance as key markers of surfaces that were not glacially eroded through, at least, the late Quaternary. However, presently blockfield-mantled surfaces may potentially be subjected to large spatial variations in erosion rates, and their Neogene regolith mantles may have been comprehensively eroded during the late Pliocene and early Pleistocene. Their role as markers by which to estimate glacial erosion volumes in surrounding landscape elements therefore remains uncertain.

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The role of impacts on Archaean tectonics

Geology ◽

10.1130/g46533.1 ◽

2019 ◽

Vol 48 (2) ◽

pp. 174-178 ◽

Cited By ~ 9

Author(s):

C. O’Neill ◽

S. Marchi ◽

W. Bottke ◽

R. Fu

Keyword(s):

System Response ◽

Lithospheric Thickness ◽

Tectonic Processes ◽

Field Evidence ◽

Impact Flux ◽

Impact Indicators ◽

Tectonic System ◽

The Impact ◽

Pilbara Craton

Abstract Field evidence from the Pilbara craton (Australia) and Kaapvaal craton (South Africa) indicate that modern tectonic processes may have been operating at ca. 3.2 Ga, a time also associated with a high density of preserved Archaean impact indicators. Recent work has suggested a causative association between large impacts and tectonic processes for the Hadean. However, impact flux estimates and spherule bed characteristics suggest impactor diameters of <100 km at ca. 3.5 Ga, and it is unclear whether such impacts could perturb the global tectonic system. In this work, we develop numerical simulations of global tectonism with impacting effects, and simulate the evolution of these models throughout the Archaean for given impact fluxes. We demonstrate that moderate-size (∼70 km diameter) impactors are capable of initiating short-lived subduction, and that the system response is sensitive to impactor size, proximity to other impacts, and also lithospheric thickness gradients. Large lithospheric thickness gradients may have first appeared at ca. 3.5–3.2 Ga as cratonic roots, and we postulate an association between Earth’s thermal maturation, cratonic root stability, and the onset of widespread sporadic tectonism driven by the impact flux at this time.

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