Daily PM_2.5 and water-soluble inorganic ions (NH₄⁺, SO₄²⁻, NO₃⁻, Cl⁻, Ca²⁺, Na⁺, K⁺, Mg²⁺) were collected at the Hongshan Air Monitoring Station at the China University of Geosciences (Wuhan) (30°31′N, 114°23′E), Wuhan, from 1 January to 30 December 2013. A total of 52 effective PM_2.5 samples were collected using medium flow membrane filter samplers, and the anionic and cationic ions were determined by ion chromatography and ICP, respectively. The results showed that the average mass concentration of the eight ions was 40.96 µg/m³, which accounted for 62% of the entire mass concentration. In addition, the order of the ion concentrations was SO₄²⁻ > NO₃⁻ > NH₄⁺ > Cl⁻ >K⁺ > Ca²⁺ > Na⁺ > Mg²⁺. The secondary inorganic species SO₄²⁻, NO₃⁻ and NH₄⁺ were the major components of water-soluble ions in PM_2.5, with a concentration of 92% of the total ions of PM_2.5, and the total concentrations of the three ions in the four seasons in descending order as follows: winter, spring, autumn, and summer. NH₄⁺ had a significant correlation with SO₄²⁻ and NO₃⁻, and the highest correlation coefficients were 0.943 and 0.923 (in winter), while the minimum coefficients were 0.683 and 0.610 (in summer). The main particles were (NH₄)₂SO₄ and NH₄NO₃ in PM_2.5. The charge of the water-soluble ions was nearly balanced in PM_2.5, and the pertinence coefficients of water-soluble anions and cations were more than 0.9. The highest pertinence coefficients were in the spring (0.9887), and the minimum was in summer (0.9459). That is, there were more complicated ions in PM_2.5 in the summer. The mean value of NO₃⁻/SO₄²⁻ was 0.64, indicating that stationary sources of PM_2.5 had a greater contribution in Wuhan.

Exponential industrialization and rapid urbanization have resulted in contamination of soil by metals from anthropogenic sources in Dongguan, China. The aims of this research were to determine the concentration and distribution of various metals (arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn)) in soils and identify their potential health risks for local residents. A total of 106 soil samples were collected from the vicinity of industrial sites in Dongguan. Two types of samples were collected from each site: topsoil (0–20 cm, TS) and shallow soil (20–50 cm, SS). Results showed that the soils were contaminated by metals and pollution was mainly focused on TS. The geoaccumulation index (I_geo) and pollution indexes (PI) implied that there was a slight increase in the concentrations of Cd, Cu, Hg, Ni, and Pb, but the metal pollution caused by industrial activities was less severe, and elements of As and Cr exhibited non-pollution level. The risk assessment results suggested that there was a potential health risk associated with As and Cr exposure for residents because the carcinogenic risks of As and Cr via corresponding exposure pathways exceeded the safety limit of 10⁻⁶ (the acceptable level of carcinogenic risk for humans). Furthermore, oral ingestion and inhalation of soil particles are the main exposure pathways for As and Cr to enter the human body. This study may provide basic information of metal pollution control and human health protection in the vicinity of industrial regions.