Hypercrosslinked pyrrole was synthesized via the Friedel-Crafts reaction and then carbonized to obtain urchin-like nitrogen-doped carbon (UNC). Ultrasmall iron oxide nanoparticles were then supported on UNC, and the composite was used to prepare an electrochemical sensor for detecting uric acid (UA) in human urine. Fe_xO_y/UNC was characterized and analyzed via scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy. A glassy carbon electrode (GCE) modified with Fe_xO_y/UNC was used as an electrochemical sensor to effectively identify UA. The electrochemical behavior of the Fe_xO_y/UNC-based UA sensor was studied using differential pulse stripping voltammetry, and the optimal conditions were determined by changing the amount of Fe_xO_y/UNC, pH of the buffer solution, deposition potential, and deposition time. Under optimal conditions, the Fe_xO_y/UNC-based electrochemical sensor detected UA in the range of 2-200 μM, where the limit of detection (LOD) for UA was 0.29 μM. Anti-interference experiments were performed, and the sensor was applied to the actual analysis of human urine samples. Urea, glucose, ascorbic acid, and many cations and anions present at 100-fold concentrations relative to UA did not strongly interfere with the response of the sensor to UA. The Fe_xO_y/UNC electrochemical sensor has high sensitivity and selectivity for uric acid in human urine samples and can be used for actual clinical testing of UA in urine.

Ozone formation is closely tied to emissions of precursors, meteorological conditions, and atmospheric chemistry. In June 2024, Xuzhou City, located at the intersection of Jiangsu, Shandong, Henan, and Anhui provinces in East China, experienced a series of ozone pollution events. The continuous pollution episodes were characterized by consistently high levels of ozone, with daytime peaks reaching 130 ppb. By combining observations of atmospheric oxidation and the use of the Observation-Based Model model, it was determined that the pollution was the result of a “heatwave-ozone” co-occurring extreme event triggered by elevated temperatures, low humidity, and intense radiation. The heatwave led to increased emissions of VOCs from both natural and human-related sources, with more pronounced contribution from Bio-alkenes and OVOCs. This, in turn, resulted in higher levels of oxidizing agents and ozone formation potential, exacerbating the co-occurrence of heatwaves and ozone extremes. Sensitivity tests on enhanced controls showed that reducing NOx had a significant adverse effect on ozone levels, whereas reducing VOCs had positive benefits, particularly for controlling alkenes. Despite ongoing reductions in anthropogenic VOCs, the elevated temperatures led to an increase in natural VOCs emissions. On average, a 1°C temperature decrease could reduce the reactivity ratio of VOCs to NOx (VOC^R/NOx^R) by 0.12, thereby enhancing the advantages of emission reductions. Therefore, implementing measures to alleviate extreme heatwaves, such as limiting high-energy consumption and inducing artificial rainfall, can simultaneously reduce the intensity and reactivity of VOC emissions, aiding in the effective implementation of ozone pollution control policies.

Formaldehyde (HCHO) is a tracer of volatile organic compounds (VOCs), and its concentration has gradually decreased with the reduction in VOC emissions in recent years, which puts forward higher requirements for the detection of trace HCHO. Therefore, a quantum cascade laser (QCL) with a central excitation wavelength of 5.68 μm was applied to detect the trace HCHO under an effective absorption optical pathlength of 67 m. An improved, dual-incidence multi-pass cell, with a simple structure and easy adjustment, was designed to further improve the absorption optical pathlength of the gas. The instrument detection sensitivity of 28 pptv (1σ) was achieved within a 40 s response time. The experimental results show that the developed HCHO detection system is almost unaffected by the cross interference of common atmospheric gases and the change of ambient humidity. Additionally, the instrument was successfully deployed in a field campaign, and it delivered results that correlated well with those of a commercial instrument based on continuous wave cavity ring-down spectroscopy (R² = 0.967), which indicates that the instrument has a good ability to monitor ambient trace HCHO in unattended continuous operation for long periods of time.