An integrated toolkit using multiple methods for determining the potential sources of iron and manganese in groundwater: a case study from the lower Kelantan River Basin, Malaysia

摘要

The application of thin-section petrography, field emission scanning electron microscopy and energy dispersive X-ray analysis (FESEM-EDX), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermo-analysis, and laser Raman spectral analysis methods can be combined to characterize iron-ores and distinguish clay minerals in alluvial soils. The integrated methodology developed for this work provides the basis for a generic mineral characterization toolkit. Five main alluvial soil types have been defined in the upper layer of the lower Kelantan Basin, Malaysia: sand with low clay content, clay sand, sandy clay, mottled clay, and mud-sand. The soils contain significant concentrations of iron oxy-hydroxide, kaolinite, chlorite, and subordinate illite. FTIR spectroscopy showed that goethite in these soils is typical characterized by the presence of the band between 521 and 373 cm(-1). Goethite and hematite show ranges of 851-612 cm(-1) and 612-392 cm(-1), respectively, and goethite twin bands between 3560 and 3738 cm(-1). In other samples, the FTIR spectroscopy indicates strong goethite bending vibrations between 3567-3725 cm(-1) and 612-832 cm(-1), while hematite bands are between 392 and 532 cm(-1). Bulk powder XRD analyses indicate goethite is the main iron-bearing mineral, while XRD clay mineral analyses show the presence of chlorite with minor concentrations of illite. Thermal analyses showed the endothermic dehydroxylation peak of goethite occurs between 486 and 502 degrees C in most of the samples. The difference in the dehydroxylation endothermic peak of goethite can be attributed to the nature of nanocrystalline pedogenic goethite. The presence of exothermic peaks in some samples is ascribed to the goethite-hematite transformation phase. The main iron-bearing mineral phases identified using the Raman laser spectra method are hematite coatings on quartz. In the Si-O-nb, Si-O-b-Si, and cations stretching region, Raman bands are observed between similar to 800 and 1150 cm(-1), 800 and 600 cm(-1), and 600 cm(-1), a frequency which is usually known in the Raman shift for di-octahedral Kaolinite (Al-4[Si4O10] (OH)(8)). Previous studies have been based on assumptions regarding drainage basin mineral composition in the absence of data. This work shows that the sources of transition metals contamination in groundwater can be from local, shallow sources and that collection of data for aquifer media mineral composition is essential for the understanding of the source and fate of soluble metals.