Vertical and horizontal variabilities of ammonia in an agricultural area of Southeast China

Ammonia (NH₃) plays a crucial role in the global nitrogen cycle, the increased NH₃ emissions from agricultural activities impacting air, soil, water quality, and human health. Accurately estimating both the vertical and horizontal transport distances of NH₃ are important for effective pollution control. Therefore, we used a helium-filled balloon mounted sampler to analyze the vertical profiles of NH₃ emissions and their seasonal variations in an agricultural area of southeast China. The annual mean concentration of NH₃ in this area was 6.49 ± 0.39 μg m⁻³. Vertical measurements revealed a gradual and steady decrease with increasing height, though no significant variation detected between different heights. Seasonal variations showed that the highest concentration occurred in summer (9.98 ± 0.11 μg m⁻³) and the lowest in winter (4.65 ± 0.02 μg m⁻³). Concentrations in summer significantly higher than those in the other three seasons. NH₃ concentrations during the fertilizer application period were much higher than those in the non-fertilizer application time. We also monitored the horizontal transport distance of NH₃ after fertilization. It is indicated that NH₃ concentrations emitted from agricultural activities decreased exponentially with horizontal transport distance and could only be transported over short distances, up to 250 m. Therefore, local emissions are the dominant source of atmospheric NH₃. Abetments such as enhanced-efficiency fertilizer could reduce agriculture NH₃ emission to promote air quality.