The COVID-19 pandemic has raised awareness about various environmental issues, including PM 2.5 pollution. Here, PM 2.5 pollution during the COVID-19 lockdown was traced and analyzed to clarify the sources and factors influencing PM 2.5 in Guangzhou, with an emphasis on heavy pollution. The lockdown led to large reductions in industrial and traffic emissions, which significantly reduced PM 2.5 concentrations in Guangzhou. Interestingly, the trend of PM 2.5 concentrations was not consistent with traffic and industrial emissions, as minimum concentrations were observed in the fourth period (3/01-3/31, 22.45 μg•m −3 ) of the lockdown. However, the concentrations of other gaseous pollutants, e.g., SO 2 , NO 2 and CO, were correlated with industrial and traffic emissions, and the lowest values were noticed in the second period (1/24-2/03) of the lockdown. Meteorological correlation analysis revealed that the decreased PM 2.5 concentrations during COVID-19 can be mainly attributed to decreased industrial and traffic emissions rather than meteorological conditions. When meteorological factors were included in the PM 2.5 composition and backward trajectory analyses, we found that long-distance transportation and secondary pollution offset the reduction of primary emissions in the second and third stages of the pandemic. Notably, industrial PM 2.5 emissions from western, southern and southeastern Guangzhou play an important role in the formation of heavy pollution events. Our results not only verify the importance of controlling traffic and industrial emissions, but also provide targets for further improvements in PM 2.5 pollution.

Lead is known to have toxic effects on the cardiovascular system. Owing to its high concentration, transmission range, and absorption efficiency in organisms, inhalation of fine particulate matter (PM2.5)-bound lead (PM2.5-Pb) may cause significant cardiovascular damage. However, the contribution and adverse effects of PM2.5-Pb on workers and residents in non-ferrous metal smelting areas are not fully understood. In this work, the concentration and chemical speciation of PM2.5-Pb were analyzed to determine its pollution characteristics at a typical non-ferrous metal smelting site. A panel study conducted among factory workers revealed that PM2.5-Pb exposure makes an important contribution to the human absorption of Pb. Although the chemical speciation of PM2.5-Pb suggested poor water solubility, a high bioavailability was observed in mice (tissue average value: 50.1%, range: 31.1–71.1%) subjected to inhalation exposure for 8 weeks. Based on the bioavailability data, the relationship between PM2.5-Pb exposure and cardiovascular damage was evaluated in animal simulation experiments. Finally, a damage threshold and cardiovascular-specific risk assessment model were established for the non-ferrous metal smelting area. Our project not only accurately estimates the risk of PM2.5-bound heavy metals on the cardiovascular system but also offers a scientific basis for future prevention and therapy of PM2.5-Pb-related diseases.

A flexible wearable temperature sensor is a novel electronic sensor that can monitor real-time changes in human body temperature in a variety of application scenarios and is regarded as the "crown jewel" of information collection technology. Although flexible strain sensors based on hydrogels have excellent self-healing effects and mechanical durability, their widespread application is still limited by external power sources. Herein, a novel self-energizing hydrogel was developed by embellishing cellulose nanocrystals (CNC) with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The resultant thermoelectrically conductive CNC was then employed as a booster for poly(vinyl alcohol) (PVA)/borax hydrogels. The obtained hydrogels exhibit remarkable self-healing performance (92.57%) and exceptional stretchability (989.60%). Additionally, the hydrogel was capable of accurately and reliably identifying human motion. Most importantly, it exhibits excellent thermoelectric performance, capable of generating stable and reproducible voltages. It shows a large Seebeck coefficient of 1.31 mV k −1 at ambient temperatures. When subjected to a temperature difference of 25 K, the output voltage reaches 31.72 mV. CNC-PEDOT:PSS/PVA conductive hydrogel is multifunctional with self-healing, self-powering, and temperature sensing, which has the potential to be used for the preparation of intelligent wearable temperature-sensing devices.

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