COASTAL ZONE; TSUNAMI; CONTAMINATION; THAILAND

In this work, LIBS technique has been used for detection of heavy metal especially iron, Fe in soil sample. As there are a large number of emission spectral lines due to Fe and other constituents in soil, this study is intended to identify emission spectral lines of Fe and finally to find best fit emission spectral lines for carrying out a qualitative and quantitative analysis. LIBS apparatus used in this work consists of a laser system (Neodymium Yttrium Aluminum Garnet, Nd-YAG: Quanta Ray; LAB SERIES; 1,064 nm; 500 mJ; 8 ns) and an optical multichannel analyzer (OMA) system consisting of a spectrograph (McPherson model 2061; 1,000 mm focal length; f/8.6 Czerny-Turner) and an intensified charge coupled device (ICCD) 1024x256 pixels (Andor I*Star). The soil sample was collected from Banda Aceh city, Aceh, Indonesia. For spectral data acquisition, the soil sample has been prepared by a pressing machine in the form of pellet. The laser beam was focused using a high density lens (f=+150 mm) and irradiated on the surface of the pellet for generating luminous plasma under 1 atmosphere of air surrounding. The plasma emission was collected by an optical fiber and then sent to the optical multichannel analyzer (OMA) system for acquisition of the emission spectra. It was found that there are many Fe emission lines both atomic lines (Fe I) and ionic lines (Fe II) appeared in all detection windows in the wavelength regions, ranging from 200 nm to 1000 nm. The emission lines of Fe with strong intensities occurs together with emission lines due to other atoms such as Mg, Ca, and Si. Thus, the identification of emission lines from Fe is complicated by presence of many other lines due to other major and minor elements in soil. Considering the features of the detected emission lines, several emission spectral lines of Fe I (atomic emission line), especially Fe I 404.58 nm occurring at visible range are potential to be good candidate of analytical lines in relation to detection heavy metal pollution, Fe, in soil sample.

INDUCED BREAKDOWN SPECTROSCOPY; QUANTITATIVE-ANALYSIS; PULSE; HELIUM; LIBS; CONFIGURATION; MICROANALYSIS; ENHANCEMENT; DEUTERIUM; NM

An experimental study is performed on the time-dependent intensity variations of Zn emission focusing on the triplet (Zn I 481.0 nm) and singlet (Zn I 636.2 nm) emission lines induced under three experimental conditions. A single nanosecond (ns) Nd:YAG laser in standard laser-induced breakdown spectroscopy(LIBS) setup is employed for the investigation of direct shock wave-induced emission characteristics with N-2 ambient gas at 0.4 kPa and the different effects of He ambient gas at 2 kPa. An additional two-laser system consisting of ns and picosecond (ps) lasers in an orthogonal setup is used to study the exclusive role of a He-assisted excitation (HAE) process for the generation of those two Zn emission lines. The results of this study consistently exhibit the dominant triplet emission over the singlet emission marked by initial maximum intensity ratios of 8 and 12 obtained from the experiments using a single-laser setup in N-2 and He ambient gases, respectively, indicating the significant contribution of the HAE mechanism to the enhanced and longer lasting Zn emission in He gas. The experiment using the special two-laser setup further demonstrates the exclusive role of the HAE process in the Zn emission featuring an even markedly higher triplet/singlet intensity ratio of 22. Thus, the results of this study suggest the possibly more general nature of dominant triplet emission phenomena previously found in laser-induced He and Ca emission spectra. (C) 2017 The Japan Society of Applied Physics