[Sub-cloud secondary evaporation effect of precipitation isotope in Shaanxi-Gansu-Ningxia region, China]. / é™•ç”˜å®åœ°åŒºé™æ°´åŒä½ç´ äº‘ä¸‹äºŒæ¬¡è’¸å‘æ•ˆåº”.

During atmospheric precipitation, the evaporation of raindrops falling from the bottom of cloud layer to the ground and passing through unsaturated air, a process was called sub-cloud secondary evaporation, which will change the isotopic composition of precipitation. Using the hydrogen and oxygen stable isotope method to understand the temporal and spatial variation of secondary evaporation effect under clouds and its causes is important to understand regional water cycle process. Based on hourly meteorological data of 187 meteorological stations in Shaanxi-Gansu-Ningxia region from March 2018 to February 2019, the spatial and temporal variations of evaporation surplus ratio (f) and precipitation excess deuterium variation (Δd) were analyzed using the improved Ste-wart model, and the relationships between f and meteorological elements and Δd were examined. The results showed that, at the hourly scale, the minimum values of f and Δd in all provinces of the region appeared in the daytime, and the maximum values appeared in the night, indicating that the secondary evaporation effect under the cloud was more obvious in the daytime. At the monthly scale, the monthly variation trend of f and Δd in each province was relatively consistent, with the minimum value appearing in the summer half year, and the maximum value appearing in the winter half year, indicating that the second evaporation effect under cloud was more significant in the summer half year. From the spatial perspective, the spatial variation of f and Δd values in the region was consistent with that at the seasonal scale. In spring, the eastern and western regions were larger while the central part was smaller. In summer, the northwest region was smaller, and other regions were larger. In autumn, it decreased from south to north. In winter, the central and southern regions were smaller, and the western and northeast regions were larger. The spatial differences of secondary evaporation effects under clouds in different seasons was significant. The slopes of the linear relationship between f and Δd in Shaanxi, Gansu and Ningxia provinces were all less than 1‰·%-1, which may be caused by the arid and semi-arid climate in this area. When air temperature was higher and the relative humidity, vapor pressure, precipitation and raindrop diameter were smaller, the value of Δd was smaller, and the secondary evaporation effect under the cloud was more obvious.

[Characteristics of Stable Isotopes and Moisture Sources of Two Typical Precipitation Events in Lanzhou City].

To better understand the isotope variations on a short time scale, this study focused on a long-term rainfall event with light precipitation (June 26-27) and a short-term one with heavy precipitation (July 28) in Lanzhou City in the summer of 2019. Combined with HYSPLIT model, samples collected during a continuous precipitation event every 10 min and 30 min were analyzed to explore the characteristics and mechanism of stable hydrogen and oxygen isotopes in precipitation. The results indicate that the effect of sub-cloud secondary evaporation makes the slope of the sequential meteoric water line (SMWL) smaller at the beginning of the rainfall event. Most of the continuous sampling points are distributed above the global meteoric water line (GMWL) and local meteoric water line (LMWL). Moreover, the deuterium excess is larger than the local average annual deuterium (8.13), indicating that the samples have experienced moisture recycling to a certain extent. During two consecutive days (June 26-27) of rainfall, the variations in oxygen isotope δ18O did not follow the effect of precipitation amount; the precipitation δ18O of the first day was "L" shaped, and it fluctuated the next day. On July 28, δ18O steadily decreased, and the range of δ18O exceeded 9‰. On June 26, the moisture transport path was short at the height of 500 m and on June 27 local evaporation was the main pathway. On July 28, with a relatively stable air mass, the moisture source of the entire precipitation event did not change significantly, neither did the isotope value. Therefore, for a single precipitation event on a short time scale, the difference in moisture sources is one of the reasons for isotope variations.

[Water sources of riparian plants based on stable hydrogen and oxygen isotopes in Lanzhou section of the Yellow River, China].

As plant species for riparian ecological restoration in northern China, Tamarix ramosissima and Salix matsudana play an important role in river protection, flood control, regional climate regulation, and landscape construction of riparian vegetation. Two sampling sites were selected in the riparian zones along the Lanzhou section of Yellow River, where plant xylems and potential water sources were collected. The direct comparison method, Bayesian mixture model MixSIAR and the proportional similarity index (PS index) were used to determine the proportions of water utilization for each potential water source and the relationship of two species in water utilization. The results showed that shallow soil (0-30 cm) was the main water source during growing season, with utilization ratio being 28.3% for T. ramosissima and 24.4% for S. matsudana. For T. ramosissima, river water had the lowest contribution (16.6%), and for S. matsudana, groundwater contributed the least (17.9%). In the months with low soil moisture, plants increased the utilization ratios of river water and groundwater. The PS index at the sampling site S1 and S2 was 91.0% and 87.7%, respectively. On a monthly basis, the index in May was the highest, indicating an inter-month divergence in water use relationship. At the floodplain, there were even utilization ratios for each potential water source, which is an optimal strategy to obtain water from each potential source to the maximum extent. Our results provided theoretical basis for riparian tourism development along the Lanzhou section of the Yellow River and plant water management in environment protection in the Yellow River Basin.

Studies on structures and activities of initial Maillard reaction products by electrospray ionisation mass spectrometry combined with liquid chromatography in processing of red ginseng.

Electrospray ionisation-mass spectrometry (ESI-MS) was applied to analyse the water-soluble extract of red ginseng (RG). Several new compounds were produced from the Maillard reaction during the steaming and drying process for preparing RG. Both the tandem electrospray ionisation (ESI-MS(n)) and Fourier transform ion cyclotron resonant mass spectrometric (FT-ICR-MS) data of these products proved that they were the initial Maillard reaction products (MRPs) of maltose with glutamic acid/aspartic acid, which were specific components in RG. In addition, their anti-diabetic and antioxidant activities were examined in vitro. The anti-diabetic activities were evaluated by studying the α-glucosidase inhibition using ultrafiltration LC-MS/MS techniques, while the antioxidant activities were investigated by UPLC-ESI-MS method. The results demonstrated that four initial MRPs in RG were identified as α-glucosidase inhibitors, and showed marked scavenging effect on the hydroxyl radical ((·)OH). Based on these studies, the processing method of RG was improved to generate more active compounds.

[Change of the content of chemical constituents and anti-oxidative action of the decoction of radix ginseng combined with Flos Lonicerae, radix Polygoni Multiflori and Radix Astragali].

Ginsenosides in the decoction of Radix Ginseng, Radix Ginseng with Flos Lonicerae, Radix Polygoni Multiflori or Radix Astragali have been investigated by high performance liquid chromatography (HPLC) and electrospray ionization mass spectrometric method (ESI-MS). Change of the content of ginsenosides was nonlinear in diverse combinative proportion of Radix Ginseng with Flos Lonicerae, while the stripping of ginsenosides was promoted by a small amount of Radix Polygoni Multiflori. In the combinative decoction of Radix Ginseng with Radix Astragali, ginsenosides contents were increased compared to single decoction of Radix Ginseng. Besides, ferric reducing antioxidant power (FRAP) method was developed for determination of the total antioxidative activity of n-butanol and water-soluble extracts from the decoction. The experimental results showed that antioxidative activity was better in the combinative decoction than that in single decoction, and the FRAP values of n-butanol extract were also greater compared with that of water extract.