Measurement of the vertical distributions of atmospheric pollutants using an uncrewed aerial vehicle platform in Xi'an, China.

Vertical observations of atmospheric pollutants play crucial roles in a comprehensive understanding of the distribution characteristics and transport of atmospheric pollutants. A hexacopter uncrewed aerial vehicle equipped with miniature monitors was employed to measure the vertical distribution of atmospheric pollutants within a height of 1000 m at a rural site in Xi'an, China, in 2021. The concentrations of carbon monoxide (CO) and particulate matter (PM) showed generally decreasing trends with increasing height. The ozone (O3) concentration showed a general increasing trend with height followed by a gradual decreasing trend. Vertical decrements of PM2.5 and CO from 0 to 1000 m were significantly (p < 0.05) lower on observation days during summer (14.0 ± 8.1 µg m-3 and 8.7 ± 6.6 ppb, respectively), compared with those in winter (78.3 ± 14.1 µg m-3 and 34.8 ± 17.3 ppb, respectively). The horizontal transport of PM and CO mostly occurred in the morning and at night during winter observations at an altitude of 400-500 m. During the winter haze, the PM and CO profile concentrations below 500 m increased substantially with the decrease in the height of the thermal inversion layer. Vertical O3 transportation was observed in the afternoon and evening during summer, and a ∼37.7% (11.6 ppb) increase in ground-level O3 was observed in relation to vertical transport from the upper atmosphere. The results provide insights into the vertical distribution and transport of atmospheric pollutants in rural areas near cities.

Microplastic Characteristics in Equus kiang (Tibetan Wild Ass) Feces and Soil on the Southern Tibetan Plateau, China.

Microplastics (MPs) are emerging pollutants, and limited research has focused on their exposure to terrestrial wildlife and transport mode on the remote Tibetan Plateau (TP). Therefore, we investigated MPs in the southern soil and feces of Equus kiang (Tibetan wild ass), a species peculiar to the TP, which is known as the "third pole." We found that MP median abundances were 102 and 4.01 particles/g of dry feces and soil, respectively. In both media, the MP morphology mainly comprised ∼50 µm slender fibrous particles. In total, 29 MP types were identified in the feces, compared to 26 types in the soil. Among them, the acrylate copolymer (35.9%) and polyurethane (24.9%) were predominant in the feces, while polyurethane (22.5%) and silicone (20.4%) were predominant in the soil. After ingesting MPs at one location, E. kiang may become a source of MP pollution when moving to other meadows on the TP. The potential MP transport flux of a herd of 20 kiangs has been estimated at 1736 particles m-2 a-1. A unique "source-sink-source" MP transport model comprising an "atmospheric deposition-vegetation-feces-atmosphere" cycle on the TP was observed based on atmospheric transport simulations and terrestrial food chain transfer processes. Owing to human settlements in south and East Asia adjacent to the TP, atmospheric long-distance transmission is an essential route for MPs to enter the TP.