Abstract
The negative air ions (NAI) in a forest play an important and positive role in promoting the health of people using the forest for recreation. The purpose of this study was to explore the environmental characteristics that can effectively represent high concentrations of NAI in mountain forests to help the recreational users to seek out sites with high NAI concentrations for personal health reasons. In order to achieve this goal, we selected the mountain forest of Taibai Mountain National Forest Park, Shaanxi Province, China, as the research object and adopted an orthogonal experimental design with three factors and three levels to study the effects of terrain, altitude, and forest canopy density on the forest NAI concentrations. The results show that obvious peak–valley fluctuation occurs during 6:31 a.m. to 18:30 p.m., with the highest concentration of NAI at 8:00 a.m. (Average: 163 ions/cm3) and the lowest at 16:00 p.m. (Average: 626 ions/cm3). The altitude (p < 0.01) and canopy density (p < 0.05) were found to significantly affect NAI concentrations. The combination of site conditions in the mountain forest observed to have the highest NAI concentrations was valley topography, low altitude, and high canopy density. In addition, the highest NAI concentration was between 14:00 p.m. and 16:00 p.m., under this combination, which was thus identified as the most suitable time for health-promotion activities in mountain forests. The results provide insights into the NAI concentration characteristics and variations, along with identifying important environmental factors for the selection of health-promotion activities in mountain forests.
Highlights
Negative air ions (NAI) is a generic term for the negatively charged gas molecules and ions in the air [1]
Dividing the sampling day into three periods, we found that the average mountain forest NAI concentration trajectory is first steady, increases, and decreases
We found that the NAI concentration in the mountain forest environment with the same canopy density was significantly different at different altitudes
Summary
Negative air ions (NAI) is a generic term for the negatively charged gas molecules and ions in the air [1]. NAI are mainly generated by pathways involving cosmic rays [9], radiation (emitted by the radon element of minerals) [10], solar ultraviolet radiation [11], lightning [12], water shearing forces (the Lenard effect) [3] and plants [13]. Factors such as vegetation cover, flowing water bodies, and air humidity can be considered as important influencers of the anion content [14]. Health and wellness programs involving NAI-based forests have become
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