Characteristics of the presence and migration patterns of DOM between ice and water in the cold and arid Daihai Lake.

Seasonal ice cover plays a crucial role in shaping the physical characteristics of lakes in cold and arid regions. Moreover, the ice significantly affects the level and quality of dissolved organic matter (DOM) in the water column. We utilized spectroscopy and mass spectrometry to analyze the molecular composition and distribution of DOM in ice cores and under-ice water in Daihai Lake. We identified the main environmental factors affecting DOM migration through structural equation modelling (SEM). The freezing process created a repulsive effect on DOM, with water samples demonstrating a greater DOM content than ice. The dominant part of the DOM in the ice cores was mainly comprised of protein-like materials (71.45 %), whereas water consisted of humus-like materials (54.81 %). The average molecular weight of the ice cover DOM (m/z = 396.77) was smaller than in the under-ice water (m/z = 405.42). While low-molecular and low-aromatic protein-like material tended to be trapped in the ice layer during ice formation, large-molecular and highly aromatic humic substances were more easily expelled into the water. Interestingly, condensed aromatic hydrocarbons were found to occur less frequently in the ice phase (11 %) compared to the aqueous phase (13 %). Both the lipid and protein/aliphatic compound structures exhibited slightly higher ratios in the ice (6 % and 8 %, respectively) than in water (1 % and 5 %, respectively). SEM between the ice cover environment and DOM indicated that the ice can influence the distribution pattern of DOM through the regulation of internal solute factors and other chemicals. The nature of the DOM and the rate of ice growth also play critical roles in determining the distribution mechanism of DOM for ice and water. The pollutant distribution characteristics and migration patterns between ice and water are essential for comprehending environmental water pollution and promoting pollution management and protection measures in cold region lakes.

Identifying spatial variability of water chemical characteristics and groundwater discharge in Hulun Lake integrated remote sensing data and chemical components.

The frozen period interaction of groundwater and lakes is crucial for hydrological properties and aquatic ecology in cold and arid regions. In this study, we investigate the spatial hydrochemical characteristics, influencing factors in the Hulun Lake basin. The hydrochemical type of lake water exhibits Na-HCO3-SO4-Cl, while river shows a primary classification of Na-Ca-HCO3. Groundwater in the eastern and western regions is characterized by Na-SO4-Cl and Na-HCO3, respectively. Silicic acid and ion exchange predominantly influence groundwater chemistry in the western region, whereas evaporation and concentration play a major role in the eastern region. Total dissolved solids, Cl-, and F- emerge as the primary influencing factors of hydrochemical components in the Hulun Lake basin. Ion content decreased from the southern to the northern region, with the lowest value occurring near the Urson River. The high-temperature water body is primarily distributed in the central and southern regions of the lake. Based on characteristic ions and partial characteristics of ice surface temperature, the potential groundwater discharge areas near the inlet of the Xinkai River, the central and southern region are determined. This study reveals the hydrochemical characteristics, vertical ice distribution, and provides a scientific foundation for water resource management in cold and arid regions.

Analysis of the distribution across media, migration, and related driving factors of fluoride in cold and arid lakes during the freezing period.

Fluoride pollution in water has become a global challenge. This challenge especially affects China as a country experiencing serious fluoride pollution. While the have been past studies on the spatial distribution of fluoride, there has been less attention on different forms of fluoride. This study collected 176 samples (60, 40, and 76 ice, water, and sediment samples, respectively) from Lake Ulansuhai during the freezing period. The occurrence and spatial distribution characteristics of fluoride in lake ice-water-sediment were explored using Kriging interpolation, Piper three-line diagram, and Gibbs diagram analysis methods. The migration and transformation of fluoride during the freezing period were revealed and the factors influencing fluoride concentration in the water body were discussed considering the hydrochemical characteristics of lake surface water. The results showed that the average fluoride concentrations in the upper ice, middle ice and lower ice were 0.18, 0.09, and 0.12 mg/L, respectively, decreasing from north to south in the lake. The average concentrations of fluoride in surface water and bottom water were 0.63 and 0.83 mg/L, respectively. The concentrations of fluoride in ice and water were within the World Health Organisation drinking water threshold of 1.50 mg/L and the Class III Chinese surface water standard (GB3838-2002). The average sediment total fluorine was 1344.38 ± 200 mg/kg, significantly exceeding the global average (321 mg/kg) and decreasing with depth. The contents of water soluble, exchangeable, Fe/Mn bound, organic bound, and residual fluorides were 40.22-47.18, 13.24-43.23, 49.52-160.48, and 71.59-173.03 mg/kg, respectively. There was a significant positive correlation between fluoride concentration in ice and that in water. The change in fluoride concentration in water was mainly due to specific climatic and geographical conditions, pH, hydrochemical characteristics and ice sealing. This study is of great significance for the management of high-fluorine lakes in arid and semi-arid areas.

[Distribution Characteristics of Microplastics in Ice Sheets and Its Response to Salinity and Chlorophyll a in the Lake Wuliangsuhai].

There are sparse reports on the distribution of microplastics in the ice sheets of freshwater lakes. In this study, the abundance, color, shape, and species of microplastics in the ice sheet of Lake Wuliangsuhai were characterized using field sampling and microscope observations. Fourier-transform infrared spectroscopy (FTIR) and correlation analysis were used to examine the distribution of microplastics contained in the lake and its relationships with salinity and chlorophyll a. The results show that the average abundance of microplastics in the Lake Wuliangsuhai ice sheet is 56.75-141 n·L-1, which is approximately 10-100 times higher than in the surface water of the Lake Wuliangsuhai. Fibers were the most common type of microplastics followed by fragments. Overall abundance showed a decreasing trend in the downstream horizontal direction and was positively correlated with salinity in the vertical direction. The abundance of microplastic in the surface ice and bottom ice was greater than in the middle of the ice and near bottom of the ice. There was no correlation between the abundance of microplastic and the concentration of chlorophyll a. In addition, due to the capturing effect of the ice, microplastic particles are temporarily stored in the ice sheet in winter, which are released into water in spring. This study provides baseline information to inform microplastic pollution control measures in Lake Wuliangsuhai.