[Spatial Variation of Surface Ozone Concentration During the Warm Season and Its Meteorological Driving Factors in China].

The concentration of surface ozone (O3) in China increased consistently from 2015 to 2018, and became an important air pollutant, followed by particulate matter. This study uses real-time O3 and meteorological data, obtained in 337 cities in China during the warm seasons (April to September) of 2015 to 2018, to determine the spatial variation of surface O3 and its meteorological driving factors in major cities in China, via trend analysis, spatial autocorrelation, hotspot analysis, and multi-scale geographically weighted regression (MGWR) modeling. The results show that: ① during the warm season, O3 concentrations showed a significant growth trend (P<0.05), with an average growth rate of 0.28 µg·(m3·a)-1, while more than 55% of urban O3 concentrations increased by 0.50 µg·m-3 annually. ② There were significant regional differences in O3 concentration. High values (>60 µg·m-3) were distributed over east China, north China, central China, and northwest China, while low values (<20 µg·m-3) were distributed over south China and southwest China. ③ The spatial agglomeration of O3 concentration has been enhanced year by year, with hotspots mainly distributed over east China and central China. In contrast, there are cold spots in northeast China, southwest China, and southern China. ④Analysis of the MGWR model indicated that temperature, wind speed, cloud coverage, and precipitation all have a significant effect on the distribution of O3, although there are also discrepancies in driving factor priorities between the different regions. Temperature was the main meteorological driving factor of O3 variation during the warm season in China, and its impact on O3 concentration was significantly higher in north China, northwest China, and northeast China than in other regions; overall, there was a significant positive correlation between O3 concentration and temperature, except in Guangxi, Yunnan, and Jiangxi. O3 concentration was negatively correlated with wind speed in most regions of south China, east China, and central China, and positively correlated with wind speed in north China and northeast China. O3 concentration was significantly negatively correlated with cloud cover, except in Liaoning, Shandong, Hebei, Gansu, Guangdong, and some areas in southwest China. O3 concentration was significantly negatively correlated with precipitation, except in the northwest and southwest regions.

[Characteristics of Heavy Metal Pollution and Ecological Risk Evaluation of Indoor Dust from Urban and Rural Areas in Taiyuan City During the Heating Season].

The presence of heavy metals in indoor dust is a world-wide concern owing to its negative impact on humans. In this study, we collected indoor dust samples from urban and rural residential areas during the heating season in Taiyuan City. We then identified the concentrations of 11 heavy metals (Cd, Co, Cr, Pb, Mn, Ni, Cu, Zn, V, As, and Hg) using inductively coupled plasma-mass spectrometry. Based on the concentrations, we categorized the pollution levels of indoor dust using the geo-accumulation index and the pollution load index. We further identified the sources of heavy metals using the enrichment factor and principal component analysis. Finally, we evaluated the potential ecological risks of heavy metals via the potential ecological index. The results illustrated that ① with the exception of Co, Mn, and V, the mean concentrations of Cd, Cr, Cu, Ni, Pb, As, Zn, and Hg in indoor dust were higher than the soil background values of Shanxi Province. There was a significant difference (P<0.05) in the concentrations of Co, Cr, Cu, Mn, Ni, and Hg between the urban and rural areas. ② Overall, the pollution degree of heavy metals in indoor dust was identified as moderate in the urban area of Taiyuan City, but slight in the rural area. The indoor dust sample in the urban area was not contaminated by Co, Mn, and V. However, it was slightly polluted by As, Ni, and Hg. In addition, it was close to moderately polluted by Cd, Cr, Cu, Pb, and Zn. In the rural area, the pollution degrees of all the metals, except for Hg and V, in indoor dust were lower than those in the urban area. ③ The As, Cd, Cu, Pb, Zn, and Hg in indoor dust for both urban and rural areas might have mainly originated from anthropogenic sources. The pollution sources were mainly transportation and industry in the urban area and coal combustion and indoor smoking in the rural area. The Co, Cr, Mn, Ni, and V in indoor dust in Taiyuan City might have mainly originated from natural sources. ④ The ecological risk of heavy metal pollution in indoor dust for both the urban and rural areas of Taiyuan City was relatively high, with integrated ecological risk indexes of 359.43 and 471.02 in the urban and rural areas, respectively. In addition, Cd and Hg were the largest contributors.