scholarly journals Aragonite is calcite’s best friend at the seafloor

2021 ◽  
Author(s):  
Olivier Sulpis ◽  
Priyanka Agrawal ◽  
Mariette Wolthers ◽  
Guy Munhoven ◽  
Matthew Walker ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Reactive Transport ◽  
Transport Model ◽  
Deep Ocean ◽  
Diffusive Transport ◽  
Carbonate Production ◽  
Calcium Carbonates ◽  
Calcite Dissolution ◽  
Calcium Carbonate Dissolution

Abstract In the open ocean, calcium carbonates are mainly found in two mineral forms. Calcite, the least soluble, is widespread at the seafloor, while aragonite, the more soluble, is rarely preserved in marine sediments. Despite its greater solubility, research has shown that aragonite, which could contribute between 10 and 90% to pelagic calcium carbonate production, is able to reach the deep-ocean. If large quantities of aragonite settle and dissolve at the seafloor, this represents a large source of alkalinity that buffers the deep ocean and favours the preservation of less soluble calcite, acting as a deep-sea, carbonate version of galvanization. Here, we investigate the role of aragonite dissolution on the early diagenesis of calcite-rich sediments using a novel 3D, micrometric-scale reactive-transport model combined with 3D, X-ray tomography structures of natural aragonite and calcite shells. Results highlight the important role of diffusive transport in benthic calcium carbonate dissolution, in agreement with recent work. We show that, locally, aragonite fluxes to the seafloor could be sufficient to suppress calcite dissolution in the top layer of the seabed, possibly causing calcite recrystallization. As aragonite producers are particularly vulnerable to ocean acidification, the proposed galvanizing effect of aragonite could be weakened in the future, indirectly boosting calcite dissolution further.

The role of the viscous sublayer in calcium carbonate dissolution

2020 ◽  
Vol 201 ◽  
pp. 20-30
Author(s):  
Christopher M. Fellows ◽  
Ali A. Al-Hamzah ◽  
Gaheishi A.H. Al-Dowis ◽  
Michael G. Evans ◽  
Mohammed Mahmoodur Rahman
Keyword(s):  
Calcium Carbonate ◽  
Viscous Sublayer ◽  
Carbonate Dissolution ◽  
Calcium Carbonate Dissolution

scholarly journals Seasonality of Water Chemistry, Carbonate Production, and Biometric Features of Two Species ofCharain a Shallow Clear Water Lake

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Andrzej Pukacz ◽  
Mariusz Pełechaty ◽  
Marcin Frankowski ◽  
Artur Kowalski ◽  
Kinga Zwijacz-Koszałka
Keyword(s):  
Calcium Carbonate ◽  
Morphological Variability ◽  
Chemical Properties ◽  
Dry Weight ◽  
Dry Mass ◽  
Carbonate Production ◽  
Lake Ecosystems ◽  
Calcium Carbonates ◽  
Physical Chemical ◽  
Biometric Features

The objective of this study was to analyze the temporal variability of biometric features and the carbonate production of two charophytes:Chara polyacanthaA. Braun andChara rudisA. Braun against the background of the physical-chemical properties of water. The investigation was carried out in a small, mid-forest Lake Jasne (western Poland). It is a polymictic, mesotrophic, hardwater ecosystem dominated by charophyte vegetation. Each month, 10 individuals of each species were characterized in terms of morphometric features, fresh and dry weight, and the percentage of calcium carbonate. Additionally, physical-chemical parameters of the water were studied. The results of physical-chemical analyses indicated similar habitat conditions for both species. Despite smaller dry weightC. polyacanthawas characterized by greater morphological variability and higher rates of growth and percentage share of calcium carbonate in dry mass thanC. rudis. The percentage of calcium carbonates in dry mass did not differ significantly between the species and exceeded 60%, reaching the maximum (76% inC. polyacantha) in July and August. For both species, distinct correlations between the structure of biomass and morphological features were found. The obtained results show the great importance of charophyte vegetation in carbon cycling and functioning of lake ecosystems.

Calcium Carbonate Production through Direct Mineral Carbon Dioxide Sequestration

2014 ◽  
Vol 699 ◽  
pp. 1020-1025 ◽  
Author(s):  
Amin Azdarpour ◽  
Radzuan Junin ◽  
Mohammad Asadullah ◽  
Hossein Hamidi ◽  
Muhammad Manan ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Particle Size ◽  
Calcium Carbonate ◽  
Reaction Temperature ◽  
Carbon Dioxide Sequestration ◽  
Solution Concentration ◽  
Ammonia Solution ◽  
Carbonate Production ◽  
Calcium Carbonates ◽  
Fgd Gypsum

Mineral carbon dioxide sequestration provides a leakage free and permanent method of CO2 disposal to produce environmentally benign and stable solid carbonates. FGD gypsum as a source of calcium was proposed as the potential feedstock in this study. The purpose of this laboratory study was to investigate the effects of reaction parameters such as CO2 pressure, reaction temperature, particle size, and ammonia solution concentration on calcium carbonate purity through Merseburg process. Increasing the reaction temperature as well as the pressure was very effective in improving the calcium carbonate purity. High purity calcium carbonate was produced when reaction temperature and CO2 was increased to 400 °C and 70 bar, resulting in 93% and 94% purity, respectively. Experimental results showed that reducing particle size was also effective in enhancing the calcium carbonate purity in which the smallest particles produced higher purity calcium carbonates rather than larger particles. The role of ammonia solution on calcium carbonate purity was found to be beneficial in improving the calcium carbonate purity in which increasing the ammonia solution increased calcium carbonate purity significantly in all experiments.

scholarly journals The role of alkalinity generation in controlling the fluxes of CO<sub>2</sub> during exposure and inundation on tidal flats

2012 ◽  
Vol 9 (10) ◽  
pp. 4087-4097 ◽  
Author(s):  
P. A. Faber ◽  
A. J. Kessler ◽  
J. K. Bull ◽  
I. D. McKelvie ◽  
F. J. R. Meysman ◽  
...  
Keyword(s):  
Reactive Transport ◽  
Field Data ◽  
Transport Model ◽  
Dissolved Inorganic Carbon ◽  
High Tide ◽  
Co2 Flux ◽  
Tidal Flats ◽  
Model Simulations ◽  
Reduced Sulfur

Abstract. Dissolved inorganic carbon (DIC), gaseous CO2 and alkalinity fluxes from intertidal sediments were investigated during periods of exposure and inundation, using laboratory core incubations, previously published field data and reactive transport model simulations. In the incubations and previous field data, it was found that during periods of alkalinity production (attributed to the accumulation of reduced sulfur species within the sediment), the flux of DIC out of the sediment was greater during inundation than the gaseous CO2 flux during exposure by a factor of up to 1.8. This finding was supported by computational simulations which indicated that large amounts of sulfate reduction and reduced sulfur burial (FeS) induce an alkalinity flux from the sediment during high tide conditions. Model simulations also found that the amount of reactive Fe in the sediment was a major driver of net alkalinity production. Our finding that CO2 fluxes can be significantly lower than total metabolism during exposure has implications for how total metabolism is quantified on tidal flats.

scholarly journals The role of alkalinity generation in controlling the fluxes of CO<sub>2</sub> during exposure and inundation on tidal flats

2012 ◽  
Vol 9 (5) ◽  
pp. 5445-5469 ◽  
Author(s):  
P. A. Faber ◽  
A. J. Kessler ◽  
J. K. Bull ◽  
I. D. McKelvie ◽  
F. J. R. Meysman ◽  
...  
Keyword(s):  
Reactive Transport ◽  
Field Data ◽  
Inorganic Carbon ◽  
Transport Model ◽  
Dissolved Inorganic Carbon ◽  
High Tide ◽  
Tidal Flats ◽  
Computational Simulations ◽  
Intertidal Sediments

Abstract. Dissolved inorganic carbon, CO2 and alkalinity fluxes from intertidal sediments were investigated during periods of exposure and inundation, using laboratory core incubations, field data and reactive transport model simulations. In the incubations and field data, it was found that during periods of alkalinity production, the flux of dissolved inorganic carbon (DIC) out of the sediment was significantly greater during inundation periods. This alkalinity production was attributed to the accumulation of reduced sulfur species within the sediment. This finding was supported by computational simulations which indicated that large amounts of sulfate reduction and reduced solute burial (FeS) induce an alkalinity flux from the sediment during high tide conditions. As the fate of sulfide is controlled by Fe, the sensitivity of alkalinity flux to Fe concentrations was investigated, and it was found that amount of reactive Fe in the sediment was a major driver of net alkalinity production. The finding the CO2 fluxes can be significantly lower than total metabolism during exposure has implications for how total metabolism is quantified on tidal flats.

A new potential of calcium carbonate production induced by Bacillus sphaericus in batch fermentation

2018 ◽  
Vol 10 (9) ◽  
Author(s):  
Nuraiffa Syazwi Adzami ◽  
◽  
Miskiah Fadzilah Ghazali ◽  
Amira Hidayati Ramli ◽  
Husnul Azan Tajarudin ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Batch Fermentation ◽  
Bacillus Sphaericus ◽  
Carbonate Production

scholarly journals The role of bacterial urease activity on the uniformity of carbonate precipitation profiles of bio-treated coarse sand specimens

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Charalampos Konstantinou ◽  
Yuze Wang ◽  
Giovanna Biscontin ◽  
Kenichi Soga
Keyword(s):  
Calcium Carbonate ◽  
Calcium Chloride ◽  
Urease Activity ◽  
Coarse Sand ◽  
Carbonate Precipitation ◽  
Population Densities ◽  
Carbonate Cements ◽  
Microbially Induced Carbonate Precipitation

AbstractProtocols for microbially induced carbonate precipitation (MICP) have been extensively studied in the literature to optimise the process with regard to the amount of injected chemicals, the ratio of urea to calcium chloride, the method of injection and injection intervals, and the population of the bacteria, usually using fine- to medium-grained poorly graded sands. This study assesses the effect of varying urease activities, which have not been studied systematically, and population densities of the bacteria on the uniformity of cementation in very coarse sands (considered poor candidates for treatment). A procedure for producing bacteria with the desired urease activities was developed and qPCR tests were conducted to measure the counts of the RNA of the Ure-C genes. Sand biocementaton experiments followed, showing that slower rates of MICP reactions promote more effective and uniform cementation. Lowering urease activity, in particular, results in progressively more uniformly cemented samples and it is proven to be effective enough when its value is less than 10 mmol/L/h. The work presented highlights the importance of urease activity in controlling the quality and quantity of calcium carbonate cements.

scholarly journals The key role of contact time in elucidating the mechanisms of enhanced decontamination by Fe0/MnO2/sand systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Viet Cao ◽  
Ghinwa Alyoussef ◽  
Nadège Gatcha-Bandjun ◽  
Willis Gwenzi ◽  
Chicgoua Noubactep
Keyword(s):  
Contact Time ◽  
Diffusive Transport ◽  
Iron Hydroxides ◽  
Iron Corrosion ◽  
Short Term ◽  
Batch Studies ◽  
Water Decontamination ◽  
Co Precipitation

AbstractMetallic iron (Fe0) has shown outstanding performances for water decontamination and its efficiency has been improved by the presence of sand (Fe0/sand) and manganese oxide (Fe0/MnOx). In this study, a ternary Fe0/MnOx/sand system is characterized for its discoloration efficiency of methylene blue (MB) in quiescent batch studies for 7, 18, 25 and 47 days. The objective was to understand the fundamental mechanisms of water treatment in Fe0/H2O systems using MB as an operational tracer of reactivity. The premise was that, in the short term, both MnO2 and sand delay MB discoloration by avoiding the availability of free iron corrosion products (FeCPs). Results clearly demonstrate no monotonous increase in MB discoloration with increasing contact time. As a rule, the extent of MB discoloration is influenced by the diffusive transport of MB from the solution to the aggregates at the bottom of the vessels (test-tubes). The presence of MnOx and sand enabled the long-term generation of iron hydroxides for MB discoloration by adsorption and co-precipitation. Results clearly reveal the complexity of the Fe0/MnOx/sand system, while establishing that both MnOx and sand improve the efficiency of Fe0/H2O systems in the long-term. This study establishes the mechanisms of the promotion of water decontamination by amending Fe0-based systems with reactive MnOx.

Sign in / Sign up

Export Citation Format

Share Document