Changes in negative air ions concentration under different light intensities and development of a model to relate light intensity to directional change

Abstract

The purpose of this research was to determine changes in negative air ion (NAI) concentrations produced by plants grown under different light intensities. NAI concentrations were observed and analyzed in an outdoor green space with five plant species ( Aloe arborescens, Clivia miniata, Chlorophytum comosum, Opuntia brunnescens, Crassula portulacea) and A. arborescens was then grown under controlled-light conditions in an enclosed space for the subsequent light intensity experiment. (1) Two peaks in NAI concentration were observed over the course of 24 h in the outdoor green space: one occurred between 9:00 and 10:00 AM; the other was at approximately 8:00 PM. (2) Among the five plant species, A. arborescens produced the highest levels of NAI and responded most effectively to light with an increase in NAI generation. Accordingly, it was chosen as the model plant for studies on the changes in NAI concentration under different light intensities. (3) In enclosed-space experiments, isolated from sunlight and under controlled-light conditions, the concentrations of NAI varied with changes in light intensities. (4) Using regression analysis, a logistic model was developed showing that changes in NAI concentrations as a function of illumination intensity followed an exponential relationship.