Atmospheric Negative Ion Concentration at Parks Configured with Different Plants

  Objective  Concentration of negative ions in atmosphere at parks configured with different plants was studied with a public health concern.

  Method  The South Arena at Minjiang Park in Fuzhou was selected for a year-long, fixed-point monitoring from September 2017 till August 2018 at 30 sampling locations, where 8 types of plants, along with one as control, were configured. The diurnal concentration as well as the daily, monthly, seasonal variations on both positive and negative ion concentrations in the atmosphere at the surroundings of the various plantations were collected for the analysis and evaluation using the forest air ion index method.

  Result  (1) The diurnal variation curves on negative ion concentration generally showed a Ⅴ or U shape, and the averaged magnitudes ranked evergreen broad-leaved forest > deciduous broad-leaved forest > bamboo forest > mixed forest > palm grove > lawn > evergreen coniferous forest > bushes > control. (2) Weather conditions significantly affected the daily variations on negative ion concentration associated with plant configuration. (3) On a monthly basis, the negative ion concentration varied in a U shape curve. Whereas, the annual averages relating to the plant type decreased in the order of bamboo forest > deciduous broad-leaved forest > evergreen broad-leaved forest > palm grove > mixed forest > evergreen coniferous forest > bushes > lawn > control. (4) With respect to the seasons, the negative ion concentration at a specific plant community was the highest in autumn followed by summer, while no significant difference in spring and winter. (5) The air quality at different plant communities ranked in the order of bamboo forest > deciduous broad-leaved forest > evergreen broad-leaved forest > palm grove > mixed forest > evergreen coniferous forest > bushes > lawn > control.

  Conclusion  Negative ion concentration in the air at park was the highest between 7:00 a.m. and 9:00 a.m. in a day, which would be the most desirable times for outdoor activities. During that period, the areas planted with evergreen broad-leaved, deciduous broad-leaved or evergreen coniferous trees as well as the mixed and bamboo forests were having greater than 3 000 negative ions·cm^-3 with an excellent air quality evaluation index.