Negative Air Ion emitting capacity of five indoor ornamental plants and their effect on air particle concentration of airborne particulate matter

<bold>Objective</bold> The impact of indoor air quality on human health is becoming increasingly evident，especially in modern urban environments where health risks are exacerbated by air pollution and the use of confined spaces.Negative Air Ion（NAI），as a kind of natural air purification factor，has multiple benefits such as improving air quality，enhancing human immune regulation and relieving psychological stress.The release of NAI and adsorption of airborne particulate matter by different indoor plants are affected by their leaf surface area，leaf morphology，their own biological habits and environmental factors，showing different trends and characteristics.Therefore，screening indoor ornamental plants with efficient NAI releasing and particulate matter purifying abilities，and investigating the correlation between NAI concentration and different meteorological factors can provide reference for people to make scientific selection of indoor ornamental plants and rational planning and layout，thus providing a healthier indoor respiratory environment. <bold>Method</bold> In April and July 2024，10 rainy days and 10 sunny days were selected for the experiment，and five commonly used indoor ornamental plants，namely，<italic>Chlorophytum comosum</italic> ‘Variegatum’，<italic>Epipremnum aureum</italic>，<italic>Spathiphyllum kochii</italic>，<italic>Philodendron tabei</italic> ‘con-go’ and <italic>Aloe vera</italic>，were used for the experiment，and the indoor anion concentration，PM_2.5 concentration，PM₁₀ concentration，temperature and relative humidity were measured in different weather conditions and with different plants，respectively.The ability of the five plants to release negative ions in different weather conditions and reduce the concentration of airborne particles were evaluated comparatively，and the influencing factors of the release of negative ions by different plants were analyzed. <bold>Result</bold> NAI concentrations were higher on sunny days than on rainy days，PM_2.5 and PM₁₀ concentrations were lower than on rainy days.On sunny days，the average values of NAI released by five kinds of indoor ornamental plants were，in descending order，<italic>Spathiphyllum kochii</italic> &gt; <italic>Chlorophytum comosum</italic> ‘Variegatum’ &gt; <italic>Epipremnum aureum</italic> &gt; <italic>Aloe vera</italic> &gt; <italic>Philodendron tabei</italic> ‘con-go’；on rainy and cloudy days，the average values of NAI released by five kinds of indoor ornamental plants were，in descending order，<italic>Spathiphyllum kochii</italic> &gt;<italic>Epipremnum aureum</italic> &gt; <italic>Philodendron tabei</italic> ‘con-go’ &gt; <italic>Aloe vera</italic> &gt; <italic>Chlorophytum comosum</italic> ‘Variegatum’.The <italic>Philodendrontabei</italic> ‘con-go’ exhibits the strongest ability to reduce PM_2.5 and PM₁₀concentrations，followed by the <italic>Spathiphyllum kochii</italic> on sunny days and the <italic>Aloe vera</italic> on rainy days，while the <italic>Epipremnum aureum</italic> shows the least effectiveness.Different plants exhibit varying effects on enhancing indoor NAI concentrations and reducing airborne particulate matter concentrations at different time periods.Studies have shown there is a significant positive correlation between the concentration of negative ions and temperature，while a significant negative correlation exists between the concentration of negative ions and relative humidity.Among the plants，the <italic>Chlorophytum comosum</italic> ‘Variegatum’<italic/>and <italic>Aloe vera</italic> demonstrate more pronounced responses to changes in temperature and humidity. <bold>Conclusion</bold> When the objective is to increase the concentration of NAI indoors，<italic>Spathiphyllum kochii</italic> is preferentially recommended as an indoor ornamental plant.Secondly，<italic>Chlorophytum comosum</italic> ‘Variegatum’<italic/>is recommended on sunny days，and <italic>Epipremnum aureum</italic> is recommended on rainy days.When the goal is to purify indoor airborne particulate matter，<italic>Philodendron tabei</italic> ‘con-go’ is preferentially recommended as an indoor ornamental plant.Secondly，<italic>Spathiphyllum kochii</italic> is recommended on sunny days，and <italic>Aloe vera</italic> is recommended on rainy days.Moreover，increasing the indoor temperature and reducing the relative humidity are conducive to the release of NAI by indoor ornamental plants.Especially when using the two plants，<italic>Chlorophytum comosum</italic> ‘Variegatum’ and <italic>Aloe vera</italic>，it is necessary to strengthen the regulation of indoor temperature and humidity to enhance their ability to release NAI.