Apparatus and method for determining concentration of gaseous component

A gaseous component concentration determination apparatus that emits laser beam into a gas, and detects a concentration of a target component in the gas based on the laser beam passing through the gas, the gaseous component concentration determination apparatus comprising:

• a laser emitter that emits first laser beam whose wavelength is a light absorption wavelength of the target component and second laser beam whose wavelength is a non-absorption wavelength of the target component, in an obliquely downward direction so as to be applied to a ground surface or a water surface;
• a photodetector that detects, in the case where a laser irradiation position on the ground surface or the water surface is switched between a first irradiation position and a second irradiation position by changing an orientation of the laser emitter about a horizontal axis or a height of the laser emitter, first scattered light resulting from scattering of the first laser beam at the first irradiation position, second scattered light resulting from scattering of the second laser beam at the first irradiation position, third scattered light resulting from scattering of the first laser beam at the second irradiation position, and fourth scattered light resulting from scattering of the second laser beam at the second irradiation position;
• and
• a concentration calculator that calculates the concentration of the target component between the first irradiation position and the second irradiation position, based on detection values of the first scattered light, the second scattered light, the third scattered light, and the fourth scattered light obtained by the photodetector.