Charlemagne Akpovo

Discrimination of bacteria from Jamaican bauxite soils using laser-induced breakdown spectroscopy

Soil bacteria are sensitive to ecological change and can be assessed to gauge anthropogenic influences and ecosystem health. In recent years, there has been a significant increase in the focus on new technologies that can be applied to the evaluation of soil quality. Laser-induced breakdown spectroscopy (LIBS) is a promising technique that has been used for the investigation and characterization of explosives, solids, liquids, gases, biological and environmental samples. In this study, bacteria from un-mined and a chronosequence of reclaimed bauxite soils were isolated on Luria–Bertani agar media. Polymerase chain reaction amplification of the bacterial 16S rDNA, sequencing, and phylogenetic analysis were applied to each isolated soil bacteria from the sample sites resulting in the identification and classification of the organisms. Femtosecond LIBS performed on the isolated bacteria showed atomic and ionic emission lines in the spectrum containing inorganic elements such as sodium (Na), magnesium (Mg), potassium (K), zinc (Zn), and calcium (Ca). Principal component analysis and partial least squares regression analysis were performed on the acquired bacterial spectra demonstrating that LIBS has the potential to differentiate and discriminate among bacteria in the un-mined and reclaimed chronosequence of bauxite soils.

Regional discrimination of oysters using laser-induced breakdown spectroscopy

It is well known that eastern oysters (Crassostrea virginica) are bio-indicators and can be used to determine the elemental composition of an estuarine system. Laser-induced breakdown spectroscopy (LIBS) has been successfully used for the detect of trace elements in various environmental matrices. In this work, LIBS was used to characterize oysters collected from a total of six sites in two different coastal estuarine reserves – Grand Bay, Mississippi (4 sites) and Apalachicola Bay, Florida (2 sites). Multiple ionic and neutral elemental species of Al, C, Ca, Cu, Fe, K, Mg, Na, Si, Sr, and Zn were observed through LIBS spectral analysis of the harvested oysters. Principal component analysis, discriminant function analysis, and hierarchical cluster analysis were applied to a data matrix of identified elemental lines resulting in intra- and inter-site clustering of the oysters according to their geographical origin.

Plasma Dynamics in Double-Pulse LIBS on Dicarboxylic Acids Using Combined 532 nm Nd:YAG and Carbon Dioxide Laser Pulses

Laser-induced breakdown spectroscopy (LIBS) was used as a method to monitor the evolution of C, hydrogen-α, carbon–carbon, and carbon–nitrogen spectral emissions from atmospheric recombination in a specific set of organic materials. Ablated samples were composed of a series of linear chain dicarboxylic acids with two to seven C atoms. Accumulated pulses of a focused neodymium-doped yttrium aluminum garnet (Nd:YAG) Q-switched laser beam operated at 532 nm generate a plasma in air at the sample surface. In this work, a dual-pulse LIBS technique was used to improve signal strength by enhancing the nanosecond LIBS plasma with CO2 transverse-excited breakdown in atmosphere laser pulses with an operating wavelength of 10.6 μm. Through a time-resolved analysis, we demonstrate the correlation between the signal strength of selected emissions and the number of C atoms in the linear chain. We also illustrate the effects that these constraints, along with the presence of a chiral C in the chain, have on the peak intensities of the individual lines with respect to each other by comparing the increase or nonexistence of certain spectral lines as we increase the number of C atoms in the linear chain.

Single and Dual Pulse LIBS and Its Application to Metal Detection in Coastal Estuarine Ecosystems

Oyster tissues normally contain some trace elements, and can accumulate others as contaminants. Dual pulse Laser Induced Breakdown Spectroscopy (LIBS) can be used to examine trace elements and their ionic forms in different environmental samples.