Raman spectroscopy speciation of natural and anthropogenic solid phases in river and estuarine sediments with appreciable amount of clay and organic matter

Abstract

A new methodology is proposed in order to perform direct Raman measurements in sediments with high content in clay and organic matter with a reduced pre-treatment.Following this method, different compounds were found within the samples, some of them were assigned as natural compounds (clay, iron oxide, pyrite, aragonite, calcite, silicates and quartz) and the others were included in the group that comes from the human activity (titanium oxide, phthalocyanine blue, phthalocyanine green, gypsum, calcium arsenate, lead oxide, zinc oxide, sodium sulfide and iron hydroxioxide).The study of the presence of these polluting agents and their differentiation from the compounds that belong to the sediments as natural compounds is fundamental in order to understand the mobility/retention processes of the pollutants, and thus, their bioavailability. Also the speciation studies of solid phase downstream a wastewater treatment plant can be the basis to diagnose the adequate functioning of the facility.This work shows the applicability of Raman spectroscopy to perform speciation studies in the solid phases of natural and anthropogenic compounds present in river and estuarine sediments with appreciable content in clay and organic matter. The differentiation between natural and anthropogenic compounds is of fundamental interest because the potential toxicity of a metal (i.e. arsenic) in a natural compound (i.e. arsenopyrite) is not the same as in a newly formed synthetic compound in the river system due to an anthropogenic input (i.e. calcium arsenate). This illustrates the importance of the analysis of solid phases present in sediments because most of the polluting agents can be found in a different molecular configuration than the natural one.

Soil Chemical Insights Provided through Vibrational Spectroscopy

“…calcite, hematite, and gypsum). Similarly, solvent extraction enabled applicability of Raman spectroscopy to perform speciation studies in the solid phases of natural and anthropogenic compounds present in river and estuarine sediments with appreciable clay and OM contents (Villanueva et al, 2008).…”

Raman counting: a new method to determine provenance of silt

“…Grains as small as a few microns can be theoretically determined if the objective 9100 is used with uncovered slides. Although the Raman-counting technique becomes impractical for very fine silt, it can still be used to determine minerals in clay-rich muds (Villanueva et al 2008).…”

Recent advances in linear and non‐linear Raman spectroscopy. Part III

“…For all three mobile instruments, satisfactory results were obtained for sandstones, mortars, limestones and marbles. Another study originating from the same laboratory [231] concentrated on the Raman spectroscopic speciation of natural and anthropogenic solid phases in river and estuarine sediments with appreciable amount of clay and organic matter. The study of various pollutant agents and their differentiation from the compounds that belong to the sediments as natural compounds was performed in order to understand the mobility/retention processes of the pollutants, and thus their bioavailability.…”