Substantial increase in perfluorocarbons CF4 (PFC-14) and C2F6 (PFC-116) emissions in China.

The perfluorocarbons tetrafluoromethane (CF4, PFC-14) and hexafluoroethane (C2F6, PFC-116) are potent greenhouse gases with near-permanent atmospheric lifetimes relative to human timescales and global warming potentials thousands of times that of CO2. Using long-term atmospheric observations from a Chinese network and an inverse modeling approach (top-down method), we determined that CF4 emissions in China increased from 4.7 (4.2-5.0, 68% uncertainty interval) Gg y-1 in 2012 to 8.3 (7.7-8.9) Gg y-1 in 2021, and C2F6 emissions in China increased from 0.74 (0.66-0.80) Gg y-1 in 2011 to 1.32 (1.24-1.40) Gg y-1 in 2021, both increasing by approximately 78%. Combined emissions of CF4 and C2F6 in China reached 78 Mt CO2-eq in 2021. The absolute increase in emissions of each substance in China between 2011-2012 and 2017-2020 was similar to (for CF4), or greater than (for C2F6), the respective absolute increase in global emissions over the same period. Substantial CF4 and C2F6 emissions were identified in the less-populated western regions of China, probably due to emissions from the expanding aluminum industry in these resource-intensive regions. It is likely that the aluminum industry dominates CF4 emissions in China, while the aluminum and semiconductor industries both contribute to C2F6 emissions. Based on atmospheric observations, this study validates the emission magnitudes reported in national bottom-up inventories and provides insights into detailed spatial distributions and emission sources beyond what is reported in national bottom-up inventories.

Inverse Modeling Revealed Reversed Trends in HCFC-141b Emissions for China during 2018-2020.

Having the highest ozone-depleting potential among hydrochlorofluorocarbons (HCFCs), the production and consumption of HCFC-141b (1,1-dichloro-1-fluoroethane, CH3CCl2F) are controlled by the Montreal Protocol. A renewed rise in global HCFC-141b emissions was found during 2017-2020; however, the latest changes in emissions across China are unclear for this period. This study used the FLEXible PARTicle dispersion model and the Bayesian framework to quantify HCFC-141b emissions based on atmospheric measurements from more sites across China than those used in previous studies. Results show that the estimated HCFC-141b emissions during 2018-2020 were on average 19.4 (17.3-21.6) Gg year-1, which was 3.9 (0.9-7.0) Gg year-1 higher than those in 2017 (15.5 [13.4-17.6] Gg year-1), showing a renewed rise. The proportion of global emissions that could not be exactly traced in 2020 was reduced from about 70% reported in previous studies to 46% herein. This study reconciled the global emission rise of 3.0 ± 1.2 Gg year-1 (emissions in 2020 - emissions in 2017): China's HCFC-141b emissions changed by 4.3 ± 4.5 Gg year-1, and the combined emissions from North Korea, South Korea, western Japan, Australia, northwestern Europe, and the United States changed by -2.2 ± 2.6 Gg year-1, while those from other countries/regions changed by 0.9 ± 5.3 Gg year-1.

Re-evaluating the distribution and variation characteristics of haze in China using different distinguishing methods during recent years.

Haze is identified via different methods using hourly visibility, relative humidity (RH) and PM2.5 mass concentration observations collected from 2013 to 2018 at 502 stations in China. An inter-comparison of a new haze identification method (MGB) and other currently used methods (M80 and M90) is performed in this research. Compared with other methods, the MGB method has an advantage in the expression of fine particle pollution characteristics, especially in high humidity areas. The mean value of the correlation coefficient of the daily mean PM2.5 and daily haze hour obtained by MGB in China is 0.69 which is higher than the correlation coefficients of the daily mean PM2.5 and haze hour identified by the other two methods. Compared with M80, the haze identified by MGB and M90 is less influenced by daily or monthly variations of RH. Approximately 75% of haze occurs when the RH is exceeds 60% or the PM2.5 mass concentration is below 105 µg/m3 over China, no matter which haze identification method is used. Haze has obvious regional distribution characteristics and is relatively higher in Beijing-Tianjin-Hebei and its surrounding areas, and the middle and lower reaches of the Yangtze River. The 6-year mean annual total haze identified by the MGB method is 1167 h for mainland China. Compared with MGB, M80 underestimates the haze hour by -34%, and M90 produces a smaller positive overestimation by 18%. The annual total haze hour of China and its three major economic regions shows significant decreasing trends regardless of the identification method used. Daily variation of haze is obtained in this research via automatic visibility measurement. The daily cycles of haze hour identified by MGB and M90 are similar, whereas that identified by M80 behaves differently affected by daily variation of RH. Haze hour is high in winter and low in summer.

Analysis of geographical clustering of birth defects in Heshun county, Shanxi province.

Birth defects remain the leading cause of stillbirth and infant mortality in China, especially in rural areas. The objective of this research is to seek evidence of clustering of cases of birth defects within a highly endemic area and to identify the environmental and landscape characteristics associated with increased risk for birth defects in Heshun county. This study uses four years of data, 1998-2001, to identify clusters of birth defects in Heshun county. A spatial scan statistic was employed to examine the spatial and spatio-temporal clustering of birth defects in the study area. Statistically significant clusters with high relative risk (RR = 2.981, p = 0.008) were identified using a spatial scan statistic. The spatial cluster located in southeast Heshun county has a radius of 7.52 km and includes 27 villages and 27 cases, accounting for 21.25% of the total cases during the study period. The methodology applied in this study was useful for evaluating the spatial distribution of birth defects in Heshun county from 1998-2001. The identified areas may be critical to control birth defects and may provide important direction for further study and targeted interventions.

[Regional correlation analysis of birth defects in Heshun county, Shanxi Province].

OBJECTIVE: To study the regional correlation analysis of birth defects in Heshun county, Shanxi province from 1997 to 2001. METHODS: Exploratory data analysis, especially the parallel coordinate plot (PCP) method, and geographic information system were used to analysis the regional correlation of birth defects. In this paper, we selected 1997 to 2001 five groups variables of birth defects to plot the PCP. RESULTS: Yangguangzhan and Hengling have stronger positive correlation on the region. Liyang and Niuchuan have weak correlation. Yixing and Songyan have no correlation and other towns have no positive correlation on the region. CONCLUSION: The results indicate that this studied region has the regional correlation of birth defects.