Occurrence and ecological risk of antiparasitic drugs in the Lhasa River on Qinghai-Xizang Plateau

The Lhasa River is the largest and most important tributary of the Yarlung Tsangpo River on the Tibetan Plateau, China. It is an important source of drinking water and irrigation for the inhabitants living in the watershed. Despite the increasing focus on water chemistry, the ecological risk assessment (ERA) caused by heavy metals to aquatic organisms in the Lhasa River has not been performed before. Based on the documented monitoring data for heavy metals, the species sensitivity distributions (SSDs) method was applied in this study. The potential ecological risks induced by eight major heavy metals (including arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), manganese (Mn), lead (Pb), and zinc (Zn)) in the Lhasa River to four typical categories of freshwater organisms, including insects, crustaceans, fish, and mollusks, were assessed in different water periods (e.g., high, normal, and low water-periods). Results suggested that the downstream part of the Lhasa River and the Meldromarchu and Tölungchu tributaries are the principal zones for the high aquatic ecological risks. For most of the monitoring sites, the ecological risks decreased in the following order: high-water period > normal-water period > low-water period. During the high-water period, Cu had the highest ecological risks for all selected species. For the insects, the ecological risks were quite low (< 1%) throughout the year. These results suggested that particular attention should be paid to the contamination of certain heavy metals (e.g., Cu and Cr) in the future water management in the Lhasa River.

The Lhasa River, as one of the major rivers on the Tibetan Plateau, is of great value for the study of climate and environmental changes on the Tibetan Plateau. In this paper, the grain size and the mineralogical and geochemical characteristics of the sediments from the Lhasa River were investigated. The results show the following: (1) The average grain size of the Lhasa River sediments is coarse (65.5% sand, 23.6% silt), and the sorting is overall poor; the skewness is mostly positive, and the kurtosis is wide, which reflects the obvious characteristics of river sand deposition. (2) The mineral composition of the Lhasa River sediments is dominated by quartz (38.4%), feldspar, and plagioclase feldspar, followed by clay minerals, and the content of carbonate minerals is relatively low; the content of clay minerals in the illite content is as high as 83.3%, while the chlorite content is slightly higher than kaolinite, and smectite content is very low. The chemical index of illite is less than 0.4, indicating that illite is mainly iron-rich magnesium illite. (3) The value of the chemical weathering index (CIA) of the sediments is low, implying that the sediments are in a weak–moderate chemical weathering state and dominated by physical weathering. Comprehensive analyses further revealed that the weathering process of the sediments in the Lhasa River was influenced by both climate and lithology, i.e., sediment composition is influenced not only by chemical weathering in a dry, cold climate but also by physical weathering of granites exposed over large areas. The results of this study can provide scientific references for further in-depth research on the environmental and climatic effects of the Tibetan Plateau.

Microplastics (MPs) are ubiquitous in the aquatic environment and have received widespread attention worldwide as emerging pollutants. Urbanization and anthropogenic activities are the main sources of MPs in rivers; however, the MPs in plateau rivers with less human activities are not well understood. In this study, the pollution of MPs in the surface water and shore sediment of the Lhasa River from the Qinghai-Tibet Plateau was investigated, and a risk assessment was conducted. The abundance of MPs in the surface water and shore sediment of Lhasa River were 0.63 n/L and 0.37 n/g, respectively. MPs in surface water were mainly dominated by films (43.23%) and fibers (31.12%) in shape, transparent (54.25%) in color, and 0-0.5mm (75.83%) in size, while MPs in the shore sediment were mainly fibers (43.69%) and fragments (36.53%), transparent (71.91%), and 0-0.5mm (60.18%). PP and PE were the predominant polymer types, accounting for 44.55% and 30.79% respectively in the surface water and 32.51% and 36.01% respectively in the shore sediment. More notably, the polymer pollution index (H) of MPs in the Lhasa River was at hazard level III due to the high risk caused by PVC, but the pollution load index (PLI) was low at hazard level I. This study reveals that the remote river in the Qinghai-Tibet Plateau are polluted by MPs, and their potential risks to the vulnerable ecosystem deserve attention.

Assessment of river health based on a novel multidimensional similarity cloud model in the Lhasa River, Qinghai-Tibet Plateau

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With the interaction of global change and human activities, the contradistinction between supply and demand of ecosystem services in the Qinghai-Tibet Plateau is becoming increasingly tense, which will have a profound impact on the ecological security of China and even Asia. Based on land cover data on the Qinghai-Tibet Plateau in 1990, 2005, and 2015, this paper estimated the supply capacity of ecosystem services using the value equivalent method, calculated the demand for ecosystem services using population density and economic density, established an ecosystem risk index based on the idea of an ecosystem service matrix to reveal the spatio-temporal pattern of the supply and demand of ecosystem services in the Qinghai-Tibet Plateau, and identified the potential ecological risk areas arising from the imbalance between supply and demand. The results showed that: (1) In terms of the spatio-temporal pattern of land use change, the desert area of the Qinghai-Tibet Plateau decreased the most with 26,238.9 km2, and other types of land use increased, of which construction land increased by 131.7%; (2) In terms of the supply and demand of ecosystem services, the Qinghai-Tibet Plateau was mainly dominated by low-level surplus areas, accounting for 64.0%, and the deficit in some areas has worsened significantly; and (3) In terms of division pattern of ecological risk areas, the Qinghai-Tibet Plateau presented characteristics of high risk in the east and low risk in the west. The high-risk area accounted for 1.1%, mainly distributed in the Huangshui Valley and the “One River and Two Tributaries” (Yarlung Zangbo River, Lhasa River, Nianchu River). The research results can provide reference for ecosystem management and policy formulation of the Qinghai-Tibet Plateau and have important significance for realizing the coupling and coordinated development of human–land relationship in Qinghai-Tibet Plateau.

Investigating river health and potential risks using a novel hybrid decision-making framework with multi-source data fusion in the Qinghai-Tibet Plateau

Patterns of bacterial and archaeal communities in sediments in response to dam construction and sewage discharge in Lhasa River

The Qinghai–Tibetan Plateau is one of the least hospitable areas for agriculture. Nevertheless, humans have long conducted agricultural activities on the Qinghai–Tibetan Plateau, although the amount and extent of historical cropland remains unclear. We focused on the Qinghai–Tibetan Plateau and selected the Tubo Kingdom (AD 633–842) and the Yuan Dynasty (AD 1271–1368) as study periods to explore the human–Earth relationship in high–cold plateau areas. First, we estimated the population size of the Tubo Kingdom and extracted the household data of the Yuan Dynasty from historical literature. Then, to estimate the total cropland area of the Qinghai–Tibetan Plateau, we proposed a comprehensive method for cropland estimation due to the specificity of historical literature. Finally, we obtained the Qinghai–Tibetan Plateau cropland cover by allocating the cropland area into 5'×5' grids. Finally, the main findings were as follows. (1) Total cropland area was 3.87 × 103 and 1.34 × 103 km2 during the Tubo Kingdom and Yuan Dynasty, respectively. (2) In the Tubo Kingdom, the fraction of cropland was highest in the Three-River Region (Yarlung Zangbo River, Lhasa River, and Nianchu River), with a gradual decline in the northeastward direction. During the Yuan Dynasty, cropland was concentrated in the Three-River Region and scattered in the valleys of the Nujiang and Lancang rivers. (3) Our reconstructions were highly consistent with regional development history, and addressed the gap in current global land cover datasets regarding the Qinghai–Tibetan Plateau. Thus, this study is vital to support prediction and simulation of regional and global environmental change.

A major tributary of the Yarlung Tsangpo River on the Tibetan Plateau, the Lhasa River, flows through Lhasa, one of the world's highest-altitude cities. Along with the fast urbanization and booming tourism industry in Lhasa, pollution of its aquatic environment receives growing concerns. This study quantified the spatiotemporal distributions and potential ecological risk of common antimicrobials in the lower reach of the Lhasa River for the first time and found untreated domestic wastewater to be a key source of pollution. Thirty-four antimicrobials were detected, with concentrations spanning 4 orders of magnitude (0.01–629 ng/L). Spatial variations of antimicrobials were observed, with tetracyclines and macrolides dominated at the upstream and downstream sites of Lhasa city, respectively, due to varying source inputs and different attenuation of antimicrobials. Although only a few antimicrobials pose medium–high ecological risk individually, the simultaneous occurrence of multiple antimicrobials may result in significant ecological toxicity. While the treated wastewater effluent and agricultural runoff combined contributed to 14.2 and 23.5% of the total antimicrobials in the Lhasa River during wet and dry seasons, respectively, the untreated domestic wastewater discharge accounted for the rest. These findings indicate the urgent need for improving the collection system and treatment technology of domestic wastewater in Lhasa.

Quantitative analysis of changes in Lhasa River runoff components was significant to local water resources management. This study constructed the spatial processes in hydrology (SPHY) model in the Lhasa River Basin and optimized the model’s parameters using the hydrograph partitioning curves (HPC) method. The Lhasa River Basin’s precipitation and temperature were forecasted for 2020 to 2100 using the statistical downscaling model (SDSM) and two scenarios from the fifth generation of the Canadian earth system model (CanESM5) dataset, shared socioeconomic pathways 1-2.6 (SSP1-2.6) and shared socioeconomic pathways 2-4.5 (SSP2-4.5). This study analyzed the potential changes in Lhasa River runoff and components based on the future climate. The results showed that the Lhasa River runoff from 2010 to 2019 was composed of snowmelt runoff, glacier melt runoff, rainfall runoff, and baseflow, with the proportions of 15.57, 6.19, 49.98, and 28.26%, respectively. From 2020 to 2100, under the SSP1-2.6 scenario, the precipitation and average temperature increased by 0.76mm and 0.08 °C per decade. Under the SSP2-4.5 scenario, the increasing rate was 3.57 mm and 0.25 °C per decade. Due to the temperature increase, snowmelt and glacier melt runoff showed a decreasing trend. The decline rate of total runoff was 0.31 m3/s per year under the SSP1-2.6 scenario due to the decrease in baseflow. Under the SSP2-4.5 scenario, total runoff and rainfall runoff showed a clear increasing trend at an average rate of 1.13 and 1.16 m3/s per year, respectively, related to the significant increase in precipitation. These conclusions suggested that climate change significantly impacted the Lhasa River’s total runoff and runoff components.

The interaction of surface erosion (e.g., fluvial incision) and tectonic uplift shapes the landform in the Tibetan Plateau. The Lhasa River flows toward the southwest across the central Gangdese Mountains in the southern Tibetan Plateau, characterized by a low-relief and high-elevation landscape. However, the evolution of low-relief topography and the establishment of the Lhasa River remain highly under debate. Here, we collected thermochronological ages reported in the Lhasa River drainage, using a 3D thermokinematic model to invert both late Cenozoic denudation and relief history of the Lhasa River drainage. Our results show that the Lhasa River drainage underwent four-phase denudation history, including two-stage rapid denudation at ∼25–16 Ma (with a rate of ∼0.42 km/Ma) and ∼16–12 Ma (with a rate of ∼0.72 km/Ma). In the latest Oligocene–early Miocene, uplift of the Gangdese Mountains triggered the rapid denudation and the formation of the current main drainage of the Lhasa River. In the middle Miocene, the second stage of the rapid denudation and the high relief were associated with intense incision of the Lhasa River, which is probably due to the enhanced Asian summer monsoon precipitation. This later rapid episode was consistent with the records of regional main drainage systems. After ∼12 Ma, the denudation rate decreases rapidly, and the relief of topography in the central Gangdese region was gradually subdued. This indicates that the fluvial erosion resulting from Asian monsoon precipitation increase significantly impacts on the topographic evolution in the central Gangdese region.

The species-area relationship (SAR) is a well-established, globally recognized ecological pattern, and research on SAR has expanded to include the phylogenetic diversity-area relationship (PDAR). However, this research has generally been limited to terrestrial systems. Using data on freshwater macroinvertebrates, the log–log form of the SAR and PDAR power models were compared between the Lhasa River and the Niyang River on the Tibetan Plateau in China. The study reveals that there is a significant difference in the slopes of SAR and PDAR between the two rivers, with the Lhasa River having a considerably higher slope. The beta diversity calculations in these two basins support this pattern, with the Lhasa River exhibiting significantly higher numbers of species and greater total phylogenetic beta diversity than the Niyang River. Regarding species replacement, the turnover component was the primary driver of both species and phylogenetic beta diversity in both rivers. These differences in the beta diversity components were mainly driven by dispersal constraints because spatial distance had a large effect on total beta diversity and turnover fractions. In addition, the nestedness component was more affected by climate and land cover, indicating that highland rivers are subject to the threats of anthropogenic disturbance and climate change. Therefore, spatial factors play a crucial role in determining the distribution of passively dispersed benthic organisms as the scale of change in rivers increases from local to regional effects.

Accumulation features of organochlorine pesticides and heavy metals in fish from high mountain lakes and Lhasa River in the Tibetan Plateau

The occurrence, distribution, and ecological risks of psychoactive substances (PSs) in Qinghai-Tibet Plateau (QTP) was investigated in this study. The surface water samples were collected in July in 2020 from five major water bodies, and 9 PSs were determined by liquid chromatography-mass spectrometry. The mean concentrations of the total PSs were 2.19–96.86 ng/L in lakes and 4.56–34.47 ng/L in rivers. Amphetamine (AMP) was the predominant contaminant both in lakes and rivers with a mean concentration of 12.21 ± 22.76 ng/L and 9.83 ± 6.14 ng/L, respectively. The compositions of PSs in lakes and rivers were significantly different. AMP, methadone (MTD), 3,4-methylenedioxyamphetamine (MDA), and ketamine (KET) were the most detected contaminants in lakes, while in rivers AMP, MDA, heroin (HER), and methamphetamine (METH) were the most detected ones. Concentrations of AMP and MTD, the two predominant drugs, varied spatially, with the decreasing concentration of AMP in the order of Huangshui River > Yamzhog Yumco Lake > Qinghai Lake > Lhasa River > Namco Lake, and of MTD in the order of Qinghai Lake > Namco Lake > Huangshui River > Yamzhog Yumco Lake. The risk quotients (RQs) of PSs ranged from 4.44 × 10−6 to 4.32 × 10−2, indicating a low risk of PSs in the aquatic ecosystem in QTP. Compared with other research in the world, the contamination of psychoactive substances in the Qinghai-Tibet Plateau was at relatively low levels with low ecological risks.