Procedure for Organic Matter Removal from Peat Samples for XRD Mineral Analysis

Abstract

Ombrotrophic peatlands are recognized archives of past atmospheric mineral dust deposition. Net dust deposition rates, grain size, mineral hosts and source areas are typically inferred from down-core elemental data. Although elemental analysis can be time efficient and data rich, there are some inherent limitations. X-ray diffraction (XRD) analysis allows direct identification of mineral phases in environmental samples but few studies have applied this method to peat samples and a well-developed protocol for extracting the inorganic fraction of highly organic samples (>95%) is lacking. We tested and compared different levels of pretreatment: no pre-treatment, thermal combustion (300, 350, 400, 450, 500 and 550°C) and chemical oxidation (H 2 O 2 and Na 2 S 2 O 8 ) using a homogenised highly organic (>98%) composite peat sample. Subsequently, minerals were identified by XRD. The results show that combustion is preferred to chemical oxidation because it most efficiently removes organic matter (OM), an important pre-requisite for identifying mineral phases by XRD analysis. Thermally induced phase transitions can be anticipated when temperature is the only factor to take into consideration. Based on the data required in this study the recommended combustion temperature is 500°C which efficiently removes OM while preserving a majority of common dust minerals.

Holocene atmospheric dust deposition in NW Spain

“…In that profile, sand content and ash were highly correlated ( r = 0.71, n = 249). Sjöström et al (2018) also lend support to our assumption as they found that the bulk mineralogy of peat samples ashed at 500°C was dominated by commonly occurring atmospheric dust minerals (primary minerals, such as quartz and feldspar, and secondary minerals, such as clay minerals). The geology of the area where TPD is located is mainly composed of plutonic and metamorphic rocks, implying that the mineralogy of the soils is dominated by quartz, feldspar and muscovite, with some minor contributions of plagioclase, biotite and trace abundances of minerals such as zircon, apatite or monazite.…”

Mechanism and Investment Analysis of Recycling Gasoline Solvent with Mineral Powder for Asphalt Cleaning

“…There are three primary aims for this research: (1) verify the feasibility of using mineral powder to absorb asphalt; (2) explore the absorbance efficiency and mechanism of using mineral powder to absorb asphalt; (3) assess the environmental impacts and financial investment of using mineral powder. In order to address these problems, this study focused on the dissolving process and utilized XRD (BRUKER AXS GMBH, Karlsruhe, Germany) with D8 Advance specification to study samples' crystal compositions [27]. XRF (Malvern Panalytical, Almelo, Netherland) method with Zetium specification was adopted to integrate the contents and compositions of samples [28].…”

14 kyr of atmospheric mineral dust deposition in north-eastern China: A record of palaeoclimatic and palaeoenvironmental changes in the Chinese dust source regions

“…X-ray diffraction (XRD) analyses were performed at NIGLAS, using a Malvern Panalytical XRD system (X’Pert 3 Powder) to determine the mineralogy of the ash fraction of selected samples ( n = 30). Combustion of peat samples at temperature greater than 450°C has been shown to be the most effective method for removing organic matter for XRD analyses, with minimal alteration of the mineralogy, except for clays (Sjöström et al, 2019). Prior to analysis, the samples were washed with water to remove the soluble salts (Sjöström et al, 2019).…”

“…Combustion of peat samples at temperature greater than 450°C has been shown to be the most effective method for removing organic matter for XRD analyses, with minimal altera-tion of the mineralogy, except for clays (Sjöström et al, 2019). Prior to analysis, the samples were washed with water to remove the soluble salts (Sjöström et al, 2019). The step scanning size was from 10° to 70° with a step size of 0.02° and counting time of 2 s per steps.…”