A system for species concentration spatial reconstruction for an exhaust system includes an emitter, a detector, and a controller. The emitter is coupled to a first portion of the exhaust system and tuned to a specific wavelength of a species to be measured. The detector is coupled to a second portion of the exhaust system opposite to the first portion such that the detector is positioned to detect a beam attenuation of a beam from the emitter. The controller is configured to receive a plurality of beam attenuation measurements from the detector and to generate a cross-sectional species concentration map based on the plurality of beam attenuation measurements.