Dissolution experiments on dolerite quarry fines at low liquid to solid ratio:a source of calcium for MICP

Microbially induced calcite precipitation (MICP) is an emerging soil stabilisation technique consisting of the precipitation of the mineral calcite in the soil matrix. The components required for MICP are currently industry end products. In this study, the calcium release and reusability of calcium-rich silicate quarry fines, dolerite, were investigated in closed (batch reactor) and open (permeability test) systems at liquid-to-solid (L/S) mass ratios ≤ 1·5 for MICP applications. The large specific surface area and reactive surface area accelerated calcium release, achieving calcium concentrations between 10 and 23 mM for different settings. Dissolution in the batch reactor resulted in increased silt (&lt;0·006 mm) and clay fractions. X-ray fluorescence analysis indicated no significant depletion of calcium in the dolerite after dissolution. The study showed that dolerite quarry fines dissolution in distilled water at low L/S ratios is a rich source of calcium for MICP applications.</p

Cow urine as a source of nutrients for Microbial-Induced Calcite Precipitation in sandy soil

Microbial Induced Calcite Precipitation (MICP) via biostimulation of urea hydrolysis is a biogeochemical process in which soil indigenous ureolytic microorganisms catalyse the decomposition of urea into ammonium and carbonate ions which, in the presence of calcium, precipitate as calcium carbonate minerals. The environmental conditions created by urine in soil resemble those induced by MICP via urea hydrolysis. Thus, this study assesses the suitability of a waste product, cow urine, as a source of nutrients for MICP. Urea stability in fresh and sterilised urine were monitored for a month to cover the length of a potential MICP intervention. An experimental soil column set up was used to compare the soil response to the repeated application of fresh and sterilised cow urine, within pH of 7 and 9, and the chemical-based solution. Urea hydrolysis and the carbonate content in solution were monitored to assess the suitability of the proposed alternative. In addition, the nitrification process was monitored. Key findings indicated i) urea concentration and stability in fresh and sterilised cow urine are suitable for MICP application; ii) the soil response to treatments of cow urine within pH of 7 and 9 are similar to the chemical-based solution; and iii) increasing solution pH results in a faster activation of ureolytic microorganisms and higher carbonate content in solution. These results demonstrate that cow urine is a suitable substitute of the chemical-based MICP application

Dolerite fines used as a calcium source for microbially induced calcite precipitation reduce the environmental carbon cost in sandy soil

Microbial-Induced Calcite Precipitation (MICP) stimulates soil microbiota to induce a cementation of the soil matrix. Urea, calcium and simple carbon nutrients are supplied to produce carbonates via urea hydrolysis and induce the precipitation of the mineral calcite. Calcium chloride (CaCl2) is typically used as a source for calcium, but silicate rocks and other materials have been investigated as alternatives. Weathering of calcium-rich silicate rocks (e.g. basalt and dolerite) releases calcium, magnesium and iron; this process is associated with sequestration of atmospheric CO2 and formation of pedogenic carbonates. We investigated atmospheric carbon fluxes of a MICP treated sandy soil using CaCl2 and dolerite fines applied on the soil surface as sources for calcium. Soil-atmosphere carbon fluxes were monitored over two months and determined with an infrared gas analyser connected to a soil chamber. Soil inorganic carbon content and isotopic composition were determined with isotope-ratio mass spectrometry. In addition, soil-atmosphere CO2 fluxes during chemical weathering of dolerite fines were investigated in incubation experiments with gas chromatography. Larger CO2 emissions resulted from the application of dolerite fines (116 g CO2-C m-2) compared to CaCl2 (79 g CO2-C m-2) but larger inorganic carbon precipitation also occurred (172.8 g C m-2 and 76.9 g C m-2, respectively). Normalising to the emitted carbon to precipitated carbon, the environmental carbon cost was reduced with dolerite fines (0.67) compared to the traditional MICP treatment (1.01). The carbon isotopic signature indicated pedogenic carbonates (δ13Cav = 8.2±5.0‰) formed when dolerite was applied and carbon originating from urea (δ13Cav = 46.4±1.0‰) precipitated when CaCl2 was used. Dolerite fines had a large but short-lived (&lt;2 d) carbon sequestration potential, and results indicated peak CO2 emissions during MICP could be balanced optimizing the application of dolerite fines

Electrolyte effects on poly (acrylic acid)-based aircraft de-icing fluids

Poly (acrylic acid) [PAA]-based aircraft de-icing fluids are widely used commercially but are known to be subject to the formation of insoluble gel particles within wing structures. In this study, the rheological effects of the sodium chloride, potassium formate, and calcium acetate with commercially used PAA-based fluids are reported across the temperature range of −15 to 15 °C. Calcium ions have the potential to create gel particles, reflected in the shifts in the viscosity–temperature profile, while PAA aggregation is influenced by the concentrations and compositions of sodium and potassium salts in the water used for dilution. From the data presented, it is possible to create de-icing fluid formulations with the necessary rheological characteristics from stock solutions by dilution using available water sources, providing that the ion concentration is known

Measurement of air pressure with altitude

Article describes the measurement of air pressure with altitude