The hydrogen and oxygen isotopic compositions of precipitation in a forested watershed of the South Qinling Mts., China

A prospective study on vulvovaginal candidiasis: multicentre molecular epidemiology of pathogenic yeasts in China

BACKGROUND

Vulvovaginal candidiasis (VVC) is frequent in women of reproductive age, but very limited data are available on the epidemiology in cases of VVC in China.

OBJECTIVES

The current study has been conducted to reveal the prevalence, species distribution of yeast causing VVC and molecular genetics of Candida albicans in China.

METHODS

Vaginal swabs were collected from 543 VVC outpatients recruited in 12 hospitals in China between September 2017 and March 2018. They were preliminarily incubated on Sabouraud dextrose agar and then positive subjects of which were then transmitted to our institute for further identification. CHROMagar™ was used to isolate Candida species, and all isolates were finally identified by DNA sequencing. Multilocus sequence typing (MLST) was used to analyse phylogenetic relationships of the various C. albicans isolates.

RESULTS

Eleven different yeast species were identified in 543 isolates, among which C. albicans (84.7%) was the most frequent, followed by C. glabrata (8.7%). We obtained 117 unique diploid sequence types from 451 clinical C. albicans isolates and 92 isolates (20.4%) belonged to a New Clade. All the strains appearing in the New Clade were from northern China and they were isolated from non-recurrent VVC.

CONCLUSIONS

Our findings suggest that C. albicans are still the main cause of VVC in China and the majority of C. albicans isolates belongs to Clade 1 with DST 79 and DST 45 being two most common. Moreover, the New Clade revealed in our study seems to be specific to northern China.

Distribution of hydrogen and oxygen stable isotopes and pollution indicators in water during a monsoon transitional period in Min River Basin

Based on 197 monthly river water and groundwater samples and 30 event-scale precipitation samples, our study reports the distribution of hydrogen and oxygen isotopes and pollution indicators in Min River Basin. The variation of δ¹⁸O and d-excess indicate that the water source in the upper main course water is more variable and that in the middle-lower part is relatively stable. Comparison between plots of δ²H versus δ¹⁸O in the river water and precipitation reflect the dominant water source is different between river water in the upper and middle-lower parts. The electrical conductivity (EC) shows a similar spatial variation trend for main course water collected in four campaigns. The pollutant concentration change at the confluences of main tributaries shows that the inflow of Heishui River and Dadu River leads to decreased NO₃^- and Cl^-, while that of Xi River, Pu River and Fuhe River leads to a leap in NO₃^- and Cl^-. A significant positive correlation is observed between EC and δ¹⁸O, indicating the consistent control of water sources on isotope distribution and water quality. The relationship between elevation and δ¹⁸O in the main course river water suggests that the factors affecting isotope distribution vary spatially. "Altitude effect" can only be observed in October and November for the upper steepest plateau zone due to the spatial variation in the precipitation stored during the wet season. The "inverse altitude effect" is observed for the upper part during the wet season and for the middle-lower part during the whole study period, which can be explained by the contribution of tributaries with different discharge regimes. Our findings show that water source with different discharge regimes can serve as the leading factor controlling the stream component in multi-tributary river basins with large spatial span and may mask the influence of spatial distribution of precipitation.

Stable isotopic characteristics of precipitation related to the environmental controlling factors in Ningbo, East China

Hydrogen and oxygen stable isotopes (δ²H and δ¹⁸O) in precipitation were analysed from June 2018 to May 2020 in Ningbo and were influenced by the subtropical monsoon climate in East China. The δ²H and δ¹⁸O values of precipitation in Ningbo varied from -90.0 to 6.0‰ and from -13.5 to -1.6‰, respectively. The local meteoric water line (LMWL) in Ningbo was obtained as δ²H = 9.27 δ¹⁸O + 35.95 and had a larger slope and intercept compared to the global meteoric water line (GMWL) because its water vapour sources were oceans. The more negative δ¹⁸O values and lower deuterium excess (D-excess) of precipitation in summer were due to water vapour sources from the East China Sea, the South Sea and the Western Pacific, which are controlled by the southeasterly monsoon. In contrast, the less negative δ¹⁸O and higher D-excess of precipitation in winter were influenced by water vapour sources from the North Asian continent and North China transported by the northwesterly monsoon. The precipitation amount effect was significant in Ningbo, especially in summer. The inverse temperature effect was appeared in Ningbo, except winter. These two effects may be caused mainly by the monsoon climate rather than by the secondary evaporation effect.

Stable isotopes and chemical characteristics of precipitation in Hangzhou and Huzhou, East China

Atmospheric precipitation is a very important link in the water cycle. The characteristics of major ions (n = 341) and stable isotopes (δ²H, δ¹⁸O; n = 157) were analysed in Hangzhou and Huzhou, which are economically prosperous cities in East China. The δ²H and δ¹⁸O values of precipitation ranged from - 109.70 to 21.30‰ and from - 14.87 to - 0.95‰, respectively. Compared with the local meteoric water line (LMWL) of China, the slope and intercept of the LMWL were much higher in Hangzhou and Huzhou, which is related to the effects of the humid climate and less secondary evaporation. The δ²H and δ¹⁸O values were highest in spring because of the influence of air masses from the northern Asian continent and other nearby sources. In contrast, the air masses from the South China Sea and the western Pacific Ocean in the summer had the lowest δ²H and δ¹⁸O. The dominant ions in precipitation indicate that Ca²⁺, HCO₃^-, SO₄^2-, NH₄⁺ and NO₃^- are the main ions of precipitation in Hangzhou and Huzhou, and the dilution of precipitation leads to lower concentrations of ions in spring and summer, similar to the values found in most Chinese cities. The increase in motor vehicle use resulted in a lower [SO₄^2-]/[NO₃^-] ratio (1.64) of precipitation, indicating mixed acid rain in Hangzhou and Huzhou (HZS). Based on a combination of the correlation analysis, enrichment factors and source contributions, we determined that SO₄^2- and NO₃^- were introduced mainly from anthropogenic activities such as coal combustion and vehicle exhaust, accounting for 89% and 99%, respectively. The strong correlation between Cl^- and Na⁺, as well as Ca²⁺, Mg²⁺ and K⁺, indicates that these ions commonly have marine and crustal origins, respectively, and 40% of Mg²⁺ comes from a marine source.