Fine particles (PM_2.5) in the atmosphere, especially PM_2.5 bounded with trace metals, pose potentially adverse human health risks. This study aimed to characterize the trace elements in PM_2.5 in a suburban area of Hanoi from November 2019 to December 2020. The study area represented a mixture of industrial, agricultural, and residential areas. The results revealed that PM_2.5 mass was highest in winter due to the stable meteorological conditions, which disfavor the particulate matter dispersion in the atmosphere. Fe, Mg, Zn, K, and Al were the most abundant elements in PM_2.5, accounting for 29.6, 19.0, 16.3, 15.8, and 11.3% of the total concentration of metals, respectively. PM_2.5-bound trace metals were highest in winter, followed by autumn and spring. Principal component analysis with multiple linear regression (PCA/MLR) illustrated that crustal dust, pesticide, and industrial emissions contributed to 73.6% of the total contribution sources, while vehicle exhaust mixed with coal combustion accounted for 64.1% of the total contribution sources. The health risk assessments suggested that As (HQ = 4.7) and Cd (HQ = 3.1) had non-carcinogenic risks for adults. The cumulative carcinogenic risk of elements was within the acceptable range for both children and adults. Notably, the source of As should be paid attention to as the As high concentration exceeding the safe level for non-carcinogenic risks in the study area.

This study investigated the airborne concentration of PM₁₀ and 20 trace elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Na, Pb, Ti, V, Zn) in residential, industry, traffic road, coal mining, thermal power plant area of Bac Giang province. The average PM₁₀ concentration was highest at coal site, followed by traffic 1 sites, industrial sites and traffic 2 sites, the residential sites, and lowest at the power plant site located in mountain area. While Al, Ca, Fe, K, Mg, Na were the most abundant elements in all sampling sites, accounting for 73–96% of total obtained elements, the concentration of As, Cd, Cr, Cu, Mn, Ni, Pb, V, and Zn occupied from 2.9 to 23.2%. Noticeably, the concentrations of Cd were from 7 to 65 times higher than the concentration limit for Cd (0.1 ng/m³) according the World Health Organization (WHO). Although, the Hazard Index (HI values) of all metals were found to be within the safe level for both children and adults, the Carcinogenic Risk (CR) of Cr and As in all sites were closed to the acceptable levels for children, implying a potential carcinogenic risks of these metals.

The aim of the present study was to investigate the electrochemical formation of active chlorine and its subsequent use for the degradation of the pesticide fenobucarb. Initially, the process of electrochemical active chlorine production was investigated using an electrochemical flow-cell with a Ti/RuO₂ plate electrode. The contribution of four main factors (chloride concentration, current density, the retention time of chloride in the cell (flow rate), and initial pH of inlet solution) to form active chlorine was determined by a central composite design (CCD). The influence of the four variables was statistically significant, and the contributions of flow rate, chloride concentration, pH, and current density were found to be 37.2%, 33.59%, 18.28%, and 10.93%, respectively. A mathematical model was established to predict and optimize the operating conditions for fenobucarb removal in the NaCl electrolysis process. The main transformation products (seven compound structures) were detected by liquid chromatography coupled with high-resolution mass spectrometry (LC–HRMS). The results of the model and transformation products indicated that fenobucarb was degraded due to direct oxidation on the electrode surface, and indirectly by active chlorine and other radicals present during the NaCl electrolysis process.