Characteristics of Environmentally Persistent Free Radicals in PM2.5 and the Influence of Air Pollutants in Shihezi, Northwestern China

Abstract

Environmentally persistent free radicals (EPFRs) are a kind of hazardous substance that exist stably in the atmosphere for a long time. EPFRs combined with fine particulate matter (PM2.5) can enter the human respiratory tract through respiration, causing oxidative stress and DNA damage, and they are also closely related to lung cancer. In this study, the inhalation risk for EPFRs in PM2.5 and factors influencing this risk were assessed using the equivalent number of cigarette tar EPFRs. The daily inhalation exposure for EPFRs in PM2.5 was estimated to be equivalent to 0.66–8.40 cigarette tar EPFRs per day. The concentration level and species characteristics were investigated using electron paramagnetic resonance spectroscopy. The concentration of EPFRs in the study ranged from 1.353–4.653 × 1013 spins/g, and the types of EPFRs were mainly oxygen- or carbon-centered semiquinone-type radicals. Our study showed that there is a strong correlation between the concentrations of EPFRs and conventional pollutants, except for sulfur dioxide. The major factors influencing EPFR concentration in the atmosphere were temperature and wind speed; the higher the temperature and wind speed, the lower the concentration of EPFRs. The findings of this study provide an important basis for further research on the formation mechanism and health effects of EPFRs.

Residential Wood Burning and Vehicle Emissions as Major Sources of Environmentally Persistent Free Radicals in Fairbanks, Alaska

“…Therefore, Fairbanks primarily has nonextreme air quality, but may be a concern for public health after prolonged temperature inversion in which we observe higher concentration of EPFRs (see Section 3.2). As shown in Table 1, this value in Fairbanks is comparable to that in Irvine, CA, 62 but lower than those in highly polluted Chinese cities including Shihezi, 12 Xi'an, 11 and Beijing. 5 EPFRs with a semiquinone type structure are known to be redox active, which means that they can induce the formation of ROS upon inhalation and respiratory deposition to lung lining fluid, causing oxidative stress and adverse health effects.…”

“…62 In contrast, a study in Xi'an 11 observed a positive correlation of EPFR v with ozone in the summer, and an annual a positive correlation between EPFR m and O 3 was observed in Shihezi. 12 A weak correlation between EPFR m and O 3 is observed (Figure S6e), which indicates that EPFRs are not efficiently quenched by heterogeneous reactions with O 3 .…”

“…11 We observe weak correlation of EPFR m with SO 2 (Figure S6d), which is consistent with the study in Shihezi, China which also observed very weak correlation. 12 Generally, O 3 is formed as a result of photochemical processes of NO x and VOC, but these processes are slow during high-latitude winter, so most regional O 3 should be transported from other regions during winter. 39 In Fairbanks we observe a low mixing ratio of O 3 , with an average of 10 ± 7 ppb over the course of the campaign, significantly reduced from the regional background of 30−40 ppb.…”

Toxicity Decreases with the Decay of Environmentally Persistent Free Radicals in Particulate Matter from Incomplete Solid Fuel Burning

“…The g-values of solid fuel-burning EPFRs decrease (from ∼2.0037 to ∼2.0030) when exposed to air (Table S3), and exhibit greater variation than those of atmospheric EPFRs. − The shift in g-values suggests that carbon-centered radicals with adjacent oxygen atoms exhibit greater reactivity than carbon-centered radicals . However, the line widths either remain unchanged or increase slightly (Table S4), suggesting the formation of more complex structures, such as delocalized electrons and multiple radicals .…”

Analysis and Optimized Design of Rigid–Flexible Coupling Characteristics of Crab Apple Picking Machines and Crab Apple Trees

“…Branch vibratory picking requires picking each branch individually, which can be time-consuming and inefficient, requiring a significant amount of human resources [18][19][20][21][22]. On the other hand, canopy vibratory picking involves directly vibrating the crown of the tree, increasing the chances of contact between the shaking rod and the fruit [23][24][25][26][27][28][29][30]. However, this method also poses a higher risk of fruit damage and potential harm to the fruit tree itself.…”