A laser absorption spectroscopy chamber system based on closed dynamic chamber method for multi-point synchronous monitoring ammonia emissions

Abstract

This study reports on the field testing of a newly and originally designed laser absorption spectroscopy chamber (LASC) system based on closed dynamic chamber method, which is well suited for multi-point synchronous measurement of ammonia emissions in field multiple plot experiment. Main design feature of the LASC system is individual multi-reflection cells for each chamber, achieving the synchronous in-situ monitoring ammonia emissions of all the chambers. Two movable covers for automated opening and closing of the chamber, and the highly transparent chamber walls made of acrylic plate minimize the disturbance of the chamber deployment on the ammonia transport process in the chamber. Controlled field assessment experiment was conducted to evaluate the applicability and reliability of the LASC system. The results indicated that the optimum time length of chamber closure for monitoring ammonia emission is 3 min, and the appropriate time length of chamber ventilation is 17 to 37 min. The LASC system has higher accuracy for measuring ammonia emission rate and reliability for comparatively measuring ammonia emissions from different treatments than the traditional chamber methods.

Keywords: Ammonia emission; Closed dynamic chamber method; Multi-point synchronous in-situ real-time measurement; Multiple plot experiment; Tunable diode laser absorption spectroscopy technique.