Assessment on ground-level nitrogen dioxide (NO₂) and ammonia (NH₃) at secondary forest of Mata Ayer and Kangar, Perlis

The current ground-level concentrations of nitrogen dioxide (NO₂) and ammonia (NH₃) within forests in Perlis are unknown and hardly investigated. The continual infrastructure development of Perlis and human activities may have played a major role in contributing to the decline of air quality in Perlis. Nitrogen-based trace gases may cause environmental effects while they are airborne or deposited on the ground. Due to the uncertainty of nitrogen trace gases level, this study was conducted to investigate the NO₂ and NH₃ concentrations within Mata Ayer secondary forest and Kangar. A portable gas monitor-sensor (Aeroqual Series 500) was used to assess the ground-level NO₂ and NH₃ concentrations, ambient air temperature, and relative humidity. The measurements were conducted in June 2015 between 9:30 am to 4:30 pm. The average NO₂ and NH₃ concentrations were 0.062 ppm and 0.040 ppm at the secondary forest of Mata Ayer and were found lower than Kangar (0.069 ppm and 0.125 ppm). The ambient air temperature and relative humidity in Kangar were found associated with NO₂ (r = −0.420 and r = 0.315) and NH₃ (r = −0.423 and r = 0.496). However, this was not the case at Mata Ayer secondary forest. The results indicated that human activities may have influenced the quality of ambient air in Perlis.