Source and Quality of Groundwater Surrounding the Qinghai Lake, NE Qinghai-Tibet Plateau

Response of phytoplankton composition to environmental stressors under humidification in three alpine lakes on the Qinghai-Tibet Plateau, China

Owning to their extreme environmental conditions, lakes on the Qinghai-Tibet Plateau have typically displayed a simplistic food web structure, rendering them more vulnerable to climate change compared to lakes in plains. Phytoplankton, undergoing a changing aquatic environment, play a crucial role in the material cycle and energy flow of the food chain, particularly important for the unique fish species of the Tibetan Plateau. To identify the changing environment indexes and determine the response of phytoplankton composition to the environment change in alpine lakes, three lakes-Lake Qinghai, Lake Keluke and Lake Tuosu-were selected as study areas. Seasonal sampling surveys were conducted in spring and summer annually from 2018 to 2020. Our findings revealed there were significant changes in physicochemical parameters and phytoplankton in the three lakes. Bacillariophyta was the predominant phytoplankton in Lake Qinghai from 2018 to 2020, with the genera Synedra sp., Navicula sp., Cymbella sp. and Achnanthidium sp. predominated alternately. Lake Keluke alternated between being dominated by Bacillariophyta and cyanobacteria during the same period. Dolichospermum sp., a cyanobacteria, was prevalent in the summer of 2018 and 2019 and in the spring of 2020. In Lake Tuosu, Bacillariophyta was the predominant phytoplankton from 2018 to 2020, except in the summer of 2019, which was dominated by cyanobacteria. Synedra sp., Oscillatoria sp., Pseudoanabaena sp., Chromulina sp. and Achnanthidium sp. appeared successively as the dominant genera. Analysis revealed that all three lakes exhibited higher phytoplankton abundance in 2018 that in 2019 and 2020. Concurrently, they experienced higher average temperatures in 2018 than in the subsequent years. The cyanobacteria, Bacillariophyta, Chlorophyta and overall phytoplankton increased with temperature and decreased with salinity and NH4-N. Besides, the ratios of cyanobacteria, and the ratios of Bacillariophyta accounted in total phytoplankton increased with temperature. These findings suggest that cyanobacteria and phytoplankton abundance, especially Bacillariophyta, may have an increase tendency in the three alpine lakes under warm and wet climate.

Research progress on the content and distribution of rare earth elements in rivers and lakes in China

This study reviewed the content and distribution of rare earth elements (REE) in rivers and lakes in China based on the online literature. The sequence distribution of REE presented the decreasing trends in the order: of Ce > La > Nd > Pr > Sm > Gb > Dy>Er > Yb > Eu > Lu > Ho > Tb > Tm in rivers water. Pearl River and the Jiulong River constitute a significant sediments REE reservoir with an average value mean of 229.6 mg/kg and 266.86 mg/kg, respectively; both have higher concentrations than the global river average (174.8 mg/kg) and higher than the local soil background (Chinese soil background). The Liaohe River is one of China's most polluted rivers, with REE distribution ranging from 106.61 to 174.71 g/L (average 144.59 g/L in water). The total concentrations of dissolved REE in rivers near REE mining areas in China are higher than in other rivers. Increasing anthropogenic inputs to natural systems may permanently alter the natural signatures of REE. The distribution characteristics of REE in Chinese lakes (sediments) varied greatly, and the mean enrichment factor (EF) was sorted as follows: Ce > La > Nd > Pr > Sm > Gd > Dy>Er > Yb > Eu > Ho > Tb > Tm > Lu, where Ce was the most abundant followed by La, Nd, and Pr, and these four elements account for 85.39 % of the total concentration of REE. The REE in the sediments obtained from Poyang Lake and Dongting Lake had an average concentration respectively of 254.0 μg/g and 197.95 μg/g; both are considerably higher than the average upper continental crust (146.4 μg/g) and higher than in other lakes in China and around the world. The distribution and accumulation of LREE in most lake sediments result from the joint action of human activities and natural processes. It concluded that mining tailings were the primary cause of REE pollution in sediments, and industrial and agricultural activities are mainly responsible for water contamination.