[Analysis of Water Chemistry Characteristics and Hydraulic Relationships of Different Water Bodies in Typical Mountain-oasis Systems in the Northwest Inland Area].

Kaidu River basin is a typical mountain oasis ecosystem in the northwest inland. Its hydrochemical environment information is of great significance to understand the regional hydrological process and optimize the allocation of water resources. Based on the collection of samples of various water bodies in mountainous and oasis areas in different seasons in 2020, this study analyzed the water chemical characteristics and hydraulic links in this region. The results showed that:① the water body in the study area was slightly alkaline as a whole, and the pH and TDS values showed the spatial changes of low in the oasis area and high in the mountain area; HCO3- and Ca2+ were the main anions and cations. The regional hydrochemical type was mostly HCO3--Ca2+, and the hydrochemical type of groundwater in the oasis area was more complex than that in the mountainous area. Regional hydrochemical changes were mainly controlled by rock weathering and human disturbance. ② The δ18O and δD values of the river water showed the seasonal changes of dilution in summer and enrichment in spring, whereas groundwater was depleted in winter and spring and enriched in autumn. Precipitation and glacial water did not change significantly within a year. In space, the δ18O and δD values of river water and groundwater showed the law of enrichment in the oasis area and dilution in the mountainous area. ③ The relationship between surface water and groundwater in the study area was close, and the transformation was frequent in summer. The relationship between surface water and groundwater in the oasis area was closer than that in the mountainous area. Groundwater in the oasis area was recharged by groundwater in the previous period, river water, and precipitation, and the recharge rate was usually groundwater in the previous period>river water>precipitation.

[Distribution characteristics of soil water and nutrients in pear orchard and their relationship with yields in loess hilly region]. / é»„åœŸä¸˜é™µåŒºé¦™æ¢¨å›­åœŸå£¤æ°´åˆ†ã€å »åˆ†åˆ†å¸ƒç‰¹å¾åŠå ¶ä¸Žäº§é‡çš„å ³ç³».

We analyzed soil water, nutrients, and yields in three different slope sites in the sloping farmland under Yuluxiang pear planted in the loess hilly region of Western Shanxi, across the growth periods and different soil depths. The results showed that: 1) The yield of pear was in the order of high slope site > middle slope site > low slope site. In high slope site, the yield was significantly correlated with soil water content (SWC), soil organic matter (SOM), available potassium (AK), with AK showing the most significant effect. The yield of pear in middle and low slope sites was significantly correlated with SWC, SOM, and total nitrogen (TN), with SWC having the most significant effect on yield. The contents of SWC, SOM, available phosphorus (AP) and TN in high slope site were higher than in middle and low slope sites, while AK was the highest in middle slope site. 2) Among different soil depths, soil nutrient contents were the highest within 0-20 cm soil layer, but the lowest within 20-40 cm soil layer. The SWC was significantly lower within 0-20 cm than the other soil layers and was the highest within 20-40 cm soil layer. 3) Among different growth periods, the contents of SOM, AP, and TN were the highest in flowering period, the SWC was the highest in fruiting period, and AK content was the highest in maturing period. It was suggested that in the future management of pear water and fertilizer in the region, more K fertilizer should be applied in the high slope sites in the flowering period, while N and P compound fertilizer should be applied in the fruiting period, to enhance irrigation in middle and low slope sites to decrease the limitation of water with 300 m3·hm-2. Our results could provide theoretical support and data refe-rence for planting precision irrigation and scientific fertilization of pear planted in loess hilly areas.

[Ecological security characteristics of main irrigated agricultural areas on the Loess Plateau based on remote sensing information]. / åŸºäºŽé¥æ„Ÿä¿¡æ¯çš„é»„åœŸé«˜åŽŸä¸»è¦çŒæº‰å†œä¸šåˆ†å¸ƒåŒºç”Ÿæ€å®‰å ¨ç‰¹å¾.

Ecological security is an important guarantee for the sustainable development of regional economy and society. We analyzed the change characteristics of fraction vegetation coverage (FVC) and remote sensing ecological index (RSEI) of four irrigated agriculture regions of the Loess Plateau (Yinchuan Plain, Hetao Plain, Fenhe River Valley and Weihe River Plain) based on the remote sensing data from 2000 to 2018. The results showed that the FVC decreased in the study area from 2000 to 2018. The variation trend of FVC differed among the four irrigated agricultural distribution areas. The RSEI of the whole area showed an overall downward trend, the RSEI of Yinchuan Plain (down 0.06) and Weihe River Plain (down 0.07) decreased significantly, and the RSEI of Hetao Plain remained stable. The RSEI of Fenhe River Valley showed an increased trend. The ecological stability of Yinchuan Plain and Fenhe River Valley was relatively low, the ecological environment of Hetao Plain was relatively stable, and the ecological environment of Weihe River Plain continued to degrade. The results were important for regional ecological environment protection and agricultural sustainable development.

[Orographic Influences on the Spatial Distribution of PM2.5 on the Fen-Wei Plain].

Topography not only has an effect on the spatial distribution of pollutants by restricting populations and industrial activities, but also affects the formation, transmission, accumulation, diffusion, and sedimentation of PM2.5. Topography is, therefore, an essential variable for understanding the spatial distribution of PM2.5, especially in basin areas. Based on gridded data and both natural and human indexes, this paper examines orographic effects on the distribution of PM2.5 on the Fen-Wei Plain based on the change point method, regression, the geographical detector method, and bivariate spatial autocorrelation. The results indicate that:① The relief amplitude of the plain is generally lower in its central part than at its edge, which is similar to the attitudinal distribution in this region; ② The distribution of PM2.5 is negatively related to relief amplitude, with high concentrations in central area and lower concentrations at the edge; ③ Based on the geographical detector analysis, PM2.5 patterns in this region are shaped by human factors including population, gross domestic product(GDP), and energy consumption, as well as natural factors including meteorological conditions and vegetation; and ④ Topography has a significant effect on both human and natural factors; an increase of relief amplitude is associated with a decrease in population, GDP, and energy consumption based on power function. Accordingly, temperature goes down linearly; precipitation, relative moisture, and wind speed increase linearly; and the vegetation index increases based on a logarithmic function.