An inversion model for estimating the negative air ion concentration using MODIS images of the Daxing'anling region

Temporal dynamics and relationship between negative air ions and environmental factors in subtropical forests, China

Negative air ions (NAIs) in forest air contribute to air purification, improve respiratory system function, enhance immunity, reduce fatigue, and alleviate stress and anxiety. However, NAIs are easily influenced by meteorological factors, air quality factors, and radiation factors, and the mechanisms of these influences remain unclear. To investigate the dynamic changes of NAIs and their driving factors, this study focuses on the long-term monitoring of NAIs in the Yunzhong Mountain forest of the South Asian subtropical region in China. Using linear mixed models, structural equation models, and other ecological niche models, the study explores the characteristics of the dynamic changes in NAIs and their responses to meteorological factors, air quality factors, and radiation factors in the Yunzhong Mountain forest. The results showed that: (1) The seasonal variation of NAIs in the Yunzhong Mountain forest followed the pattern of summer > autumn > winter > spring. In terms of monthly dynamics, the highest concentrations of NAIs occurred in August. Regarding daily dynamics, the concentration of NAIs gradually increased from early morning, reaching its peak at 8:00 AM, after which it declined, reaching the lowest concentrations between 11:00 AM and 12:00 PM. (2) Correlation analysis showed that the concentrations of NAIs were significantly negatively correlated with NO2, air temperature (AT), PM1, PM2.5, and PM10, and significantly positively correlated with air humidity (AH). However, generalized linear mixed analysis indicated that PM2.5, O3, NO2, and air pressure (AP) had significant negative effects on the seasonal, monthly, and daily concentrations of NAIs, while air humidity and temperature exhibited significant positive effects. Moreover, air quality factors had a greater impact than meteorological factors on seasonal and monthly concentrations, whereas meteorological factors had a more pronounced influence on daily negative air ion concentrations. (3) The latent variable of air quality factors had a direct negative effect on the concentration of NAIs, with O3, PM1, and PM2.5 exerting significant indirect negative effects through the air quality factors. The latent variable of meteorological factors had a significant positive effect on the concentration of NAIs. Additionally, radiation factors did not have a direct significant effect on negative air ions, but radiation factors (ultraviolet radiation and net radiation) produced significant indirect positive effects on NAIs through meteorological factors and air quality. The concentration of NAIs in the Yunzhong Mountain forest is highest between 7:00 and 8:00 AM during July and August in the summer, making it the most suitable time for outdoor activities. Meteorological factors, air quality, and radiation factors all influence the NAIs in Yunzhong Mountain. Even in the absence of direct effects, these factors can have indirect impacts through other variables.

Exurban and suburban forests have superior healthcare benefits beyond downtown forests

Forests in urban areas provide great healthcare benefits to citizens, but it is less well known whether this benefit is related to different geographical spaces. We selected exurban forest, suburban forest, downtown forest, and urban control in Guangzhou, China to analyze the change characteristics of negative air ion concentration (NAIC), air oxygen content (AOC), and human comfort index (HCI). Based on Criteria Importance Through Intercriteria Correlation (CRITIC) method, the urban forest comprehensive healthcare index (UFCHI) was established. Finally, the evaluation criteria for UFCHI were identified by cluster analysis. The results demonstrated that (1) The NAIC in exurban forest (2,713 ± 1,573 ions/cm3) and suburban forest (2,147 ± 923 ions/cm3) was evidently better than downtown forest (1,130 ± 255 ions/cm3) and urban control (531 ± 162 ions/cm3). (2) The AOC was in the order of exurban forest (21.17 ± 0.38%) > suburban forest (21.13 ± 0.30%) > downtown forest (21.10 ± 0.16%) > urban control (20.98 ± 0.12%). (3) The HCI in urban control (5.56 ± 2.32) and downtown forest (5.15 ± 1.80) is higher than suburban forest (4.02 ± 1.53) and exurban forest (3.71 ± 1.48). (4) The UFCHI in exurban forest (1.000), suburban forest (0.790), and downtown forest (0.378) were beneficial to human health to some extent, while urban control (0.000) was at Level IV, having no healthcare benefit. Except in winter, the UFCHI in exurban forest and suburban forest were all at Level II and above; while downtown forest and urban control were all at Level III and below at all seasons. Overall, urban forests in the exurbs and suburbs have better healthcare benefits than those in the downtowns. Furthermore, it is recommended that urban residents visit exurban and suburban forests for forest therapy in spring, summer, and autumn.

Effects of negative air ions (NAIs) on Leishmania major: A novel tool for treatment of zoonotic cutaneous leishmaniasis (ZCL)

Background

Cutaneous leishmaniasis (CL) is a Neglected Tropical Disease (NTD) that causes high morbidity in the tropics and sub-tropics. Despite the remarkable advancements in the treatment of CL, the available therapeutics are far from ideal and also cause serious adverse side effects. Negative air ions (NAIs) generators are widely available for domestic and industrial uses. Several studies have reported on positive effects of NAIs therapy on human health as a non-pharmaceutical treatment for respiratory disease, allergy, or stress-related health conditions, including infectious diseases. To our knowledge, no studies have examined the effectiveness of the NAIs therapy against Leishmania parasites. The aims of this study were to investigate the effect of NAIs therapy on Leishmania major (L. major) the causative agent of CL in in vitro and in a murine model.

Methodology/Principal findings

In vitro anti-leishmanial effects of NAIs therapy were measured by parasitological methods. NAIs therapy was assessed in vivo in L. major infected BALB/c mice by measuring the footpad (FP) lesion size and parasite load using metric caliper tool and qPCR, respectively. Immune responses in treated and non-treated mice were assessed by measuring the levels of IFN-γ, IL-4, NO and arginase activity. In vitro NAIs therapy significantly decreased the viability of Leishmania promastigotes and of amastigotes cultured in macrophages, but did not affect the host cells. NAIs therapy of L. major infected BALB/c mice resulted in reduced FP lesion size, diminished parasite burden, and importantly decreased induction of IL-4 and arginase activity in the presence of NAIs. In contrast IFN-γ and NO levels were significantly enhanced. NAIs therapy significantly diminished the progression of disease compared to the control group, but was less effective than amphotericin B treatment.

Conclusions

Our study shows that NAIs treatment was effective in vitro and in Leishmania-infected mice, elicited a T-helper 1 (Th1) response and increased efficient cellular immunity, resulting in a diminished parasite load. Therefore, NAIs therapy can be considered as a useful and safe tool that can contribute to clearing L. major infections without inducing toxicity in host cells. The applications and mechanisms of NAIs therapy warrant further investigation especially in humans suffering from CL.

Study of the Vertical Structures, Thermal Comfort, Negative Air Ions, and Human Physiological Stress of Forest Walking Spaces in Summer

Forest walking is a popular, healthy, and light outdoor activity. The potential comprehensive relationships between the vertical structures, thermal comfort, negative air ions (NAI), and human physiological stress in forest walking spaces have not been determined. We performed an experiment in the Baishuihe National Nature Reserve, Sichuan Province, China. Thirty-two college students recruited as subjects completed a forest walk (approximately one kilometer) on the same trail divided into three vertical structure type subsections, namely: A (dense herb and shrub layers with a sparse tree layer), B (dense tree, herb and shrub layers), and C (dense tree and herb layers with a sparse shrub layer). When the subjects passed preset environmental measurement points, staff measured climatic indexes (air temperature, relative humidity, wind velocity, surface temperature and global radiation) and NAI levels, and these data were input into the Rayman model to form a comprehensive thermal comfort index, the physiologically equivalent temperature (PET). PET and NAI differences and dynamic data among the subsections were analyzed. The subjects’ brain waves, heart rates (HRs), and walking speed (S) were digitally recorded. We selected brain wave θ, γ and β-high/α rates, neuroemotional indexes (stress and relaxation) and HR as physiological indicators, and S as an auxiliary indicator. The correlations between PET and NAI with physiological and auxiliary indexes were analyzed. Forest type C showed the lowest PETs and highest NAIs along with the most stable dynamic changes. PET was negatively correlated with HR and positively correlated with γ (12 channels). NAI was positively correlated with S and relaxation and negatively correlated with γ (two channels) and the β-high/α ratio (five channels). These comprehensive relationships suggest that dense tree, sparse shrub, and high-coverage herb layers combined with optimal temporal conditions (before noon or after a light rain) form the best thermal comfort and NAI conditions conducive to reducing human physiological pressures during summer daytime forest walking. These results provide theoretical references for forest walking and spatial regulation.

Effects of Different Site Conditions on the Concentration of Negative Air Ions in Mountain Forest Based on an Orthogonal Experimental Study

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.