Plateau Lake Research Articles

Climate and Nutrient-Driven Regime Shifts of Cyanobacterial Communities in Low-Latitude Plateau Lakes.

Cyanobacterial blooms that form in response to climate warming and nutrient enrichment in freshwater lakes have become a global environmental challenge. Historical legacy effects and the mechanisms underlying cyanobacterial community succession are not well understood, especially for plateau lakes that are important global freshwater resources. This study investigated the temporal dynamics of cyanobacterial communities over centuries in response to nutrient enrichment and climate warming in low-latitude plateau lakes using high-throughput DNA sequencing of sedimentary DNA combined with traditional paleolimnological analyses. Our results confirmed that nutrients and climate warming drive shifts in cyanobacterial communities over time. Cyanobacterial community turnover was pronounced with regime shifts toward new ecological states, occurring after exceeding a tipping point of aquatic total phosphorus (TP). The inferred species interactions, niche differentiation, and identity of keystone taxa significantly changed after crossing the aquatic TP ecological threshold, as demonstrated by network analysis of cyanobacterial taxa. Further, the contribution of aquatic TP to cyanobacterial community dynamics was greater than that of air temperature when lakes were in an oligotrophic state. In contrast, as the aquatic TP threshold was exceeded, the contribution to community dynamics by air temperature increased and potentially surpassed that of aquatic TP. Overall, these results provide new evidence for how past nutrient levels in lacustrine ecosystems influence contemporary cyanobacterial community responses to global warming in low-latitude plateau lakes.

Phytoplankton responses to solar UVR and its combination with nutrient enrichment in a plateau oligotrophic Lake Fuxian: a mesocosm experiment.

Multiple stressors associated with global change are influencing the phytoplankton taxonomic composition and biomass in plateau lakes, such as higher levels of ultraviolet radiation (UVR, 280-400nm) and the risk of eutrophication. Although the restrictive effects of high UVR on phytoplankton are generally recognized, the effects will be impacted by the UVR levels of seasonal changes and the nutrient status. In this study, in situ phytoplankton productivity was measured seasonally under full solar radiationand only visible light (photosynthetically active radiation, PAR) conditionsin the plateau oligotrophic Lake Fuxian, Southwest China. To determine the single effects of UVR and nutrient enrichment and their combined impact on phytoplankton communities, a mesocosm experiment (1month) was conducted outdoors during late summer (rainy season). The interactive experiment was designed with two radiation treatments (UVR + PAR and PAR) and four nutrient treatments (raw water, nitrogen addition, phosphorus addition, nitrogen and phosphorus addition). Our results suggested that the response of phytoplankton to UVR depended largely on nutrient availability, which was embodied in the no significant responses of phytoplankton productivity and total biomass to UVR in the oligotrophic raw water from Lake Fuxian, but the positive responses of total biomass to UVR in the nutrient enrichment treatment. Furthermore, the response of phytoplankton to UVR was also taxa dependent. Chlorophytes and dinoflagellates showed positive response to UVR, whereas chrysophytes were quite sensitive to UVR; diatoms had no significant response to UVR under all nutrient conditions, while the response of cyanobacteria to UVR was highly dependent on nutrient status. This study highlights that the increase in nutrient concentrations in oligotrophic lake not only directly promotes the growth of phytoplankton but also combines with low UVR during summer to benefit the growth of eutrophic taxa based on the non-negative effect of UVR on total phytoplankton biomass and the positive effect on eutrophic taxa.

Heavy metal contamination in surface sediments from lakes and their surrounding topsoils of China.

Due to rapid urbanization, industrialization, agricultural development, and mining activities, soil heavy metal pollution has become a severe issue in China. To explore the regional heavy metal ecological risk of lake sediment and surrounding topsoil, we analyzed 237 lakes, with 1797 lake sediment sampling points and 1164 surrounding topsoil sampling points. Lower mean concentrations were detected for most heavy metals in soils than sediment (except for Hg). Cd and Hg in sediments and soils showed a more significant variation, with the coefficient of variation exceeding 110%. Linear regressions and Pearson's correlation analyses demonstrated that sediments and soils exhibited significant positive correlations. The principal heavy metals exceeding the Agricultural Soil Control Standard (ASCS) in sediments and soils were As and Cd, respectively. The Yunnan-Guizhou Plateau Lake Region (YGPLR) was the most seriously affected, exceeding the ASCS for Cd. The lakes with the most severe pollution were located in YGPLR impacted by the high background concentration of heavy metals in soil and mineral development activities. The Eastern Plain Lake Region, the Southeast Lake Region, and the Northeast Plain and Mountain Lake Region showed a clear anthropogenic impact. Lakes in the Inner Mongolia-Xinjiang Lake Region and the Tibetan Plateau Lake Region were estimated to have relatively low ecological risks due to their sparse population and slight environmental disturbance. The impact of geochemical factors on the ecological risk of heavy metals in lake sediments is more substantial than that of human activities at the regional scale.

Plateau lake ecological response to environmental change during the last 60 years: a case study from freshwater Lake Yangzong, SW China

The effects of anthropogenic activity and climate change on lake ecosystems for nine large plateau lakes in Yunnan Province have recently received much attention; however, most studies have focused on the deepest lake sediments and ignored the lake sediments adjacent to the populated area. To evaluate the sedimentation rates and ecological changes, four 210Pb- and 137Cs-dated sediment cores were collected along the long axis of Yangzong Lake, a fault-controlled north-south strike lake located in Yunnan Plateau in July 2006 and July 2016, respectively. We combined a biological indicator (diatom assemblage) with geochemical indicators (total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP)) for core S0 in the southern part of the lake to examine the ecological changes in response to anthropogenic disturbances within the lake over the last 60 years. The results showed that the sedimentation rate in the southern part of the lake (S1) was significantly higher than that in the central (S2) and northern (S3) parts of the lake. Redundancy analysis (RDA) and Pearson correlation analysis identified significant correlations between TP and Aulacoseira granulata, Cyclotella ocellata, and Cyclotella rohomboideo-elliptica (correlation coefficients: − 0.66, − 0.63, and 0.81, respectively, p < 0.01). There was a clear shift in the diatom community from oligotrophic to eutrophic species becoming dominant after the 1990s, coinciding with the intensifying human activities around the lake. Furthermore, there were two periods of diatom absence in core S0, which was associated with two periods of rapid depositional events. These are likely associated with the intensification of industry, mining, road construction, and agriculture within the lake catchment. These findings highlight the sensitivity of freshwater ecosystems in the shallow-water area of a lake to human activities, with implications for future water quality in fault-controlled lakes.

Improve the Accuracy of Water Storage Estimation—A Case Study from Two Lakes in the Hohxil Region of North Tibetan Plateau

Lake water storage is essential information for lake research. Previous studies usually used bathymetric data to acquire underwater topography by interpolation method, and to therefore estimate water storage. However, due to the large area of Tibetan Plateau (TP) lakes, the method of bathymetry was challenging to cover the whole region of one lake, and the accuracy of the underwater topography, in which no bathymetric data covered, was low, which resulted in a comparatively large error of lake water storage estimation and its change. In this study, we used Shuttle Radar Topography Mission (SRTM) and in situ bathymetric data to establish the underwater topography of Hohxil Lake (HL) and Lexiewudan Lake (LL) in the Hohxil Region of North TP and estimate and analyzed the changes of lake level and water storage. The results showed HL and LL’s water storage was 5.12 km3 and 5.31 km3 in 2019, respectively, and their level increased by 0.5 m/y and 0.57 m/y during 2003−2018, respectively. They were consistent with those (0.5 m/y and 0.5 m/y) from altimetry data, and they were much more accurate than those results (0.077 m/y and 0.156 m/y) from bathymetric data. These findings indicated that this method could improve the accuracy of lake water storage and change estimation. We estimated water storage of two lakes by combining with multitemporal Landsat images, which had doubled since 1976. Our results suggested that the increasing precipitation may dominate the lake expansion by comparing with the change of temperature and precipitation and the increasing glacial meltwater contributed approximately 4.8% and 10.7% to lake expansion of HL and LL during 2000–2019 based on the glacier mass balance data, respectively.

Variation and potential influence factors of foliar pH in land-water ecozones of three small plateau lakes

Abstract Aims Foliar pH of terrestrial plants, a trait tightly associated with plant physiology and nutrient utilization, varies with plant functional types (PFTs) and environmental changes. However, it is yet unclear about the variation in foliar pH of aquatic plants, and the difference between aquatic and terrestrial plants. Methods Foliar pH, leaf carbon, nitrogen content of plants along the lakeshore zones and the environmental conditions (water or soil pH, water status) of the corresponding vegetation of three small plateau lakes were investigated, to determine the variation and potential influence factors of foliar pH at both PFT and community levels. Important Findings Foliar pH varied largely among aquatic plants, and across aquatic, helophytic and terrestrial plants. Floating-leaved macrophytes had more acidic foliage (pH = 4.21 ± 0.05) than emergent (5.71 ± 0.07) and submerged macrophytes (5.82 ± 0.06). Foliar pH of aquatic herbs (5.43 ± 0.10) was lower than that of helophytic (6.12 ± 0.07) and terrestrial herbs (5.74 ± 0.05). Terrestrial herbs had significantly higher foliar pH than woody plants. The variation in foliar pH across PFTs may be mainly ascribed to leaf structure, light utilization and nutrient characteristics. Consistent with the pattern on PFT level, aquatic communities had more acidic foliage than terrestrial communities, which was mainly shaped by species composition, water status and environmental pH. This study documented the first-time foliar pH of aquatic plants, and comparison of foliar pH among various plant types at a landscape scale. Our results provide bases for further exploration of the underlying mechanism and its ecological significance for wetland ecosystems.

Remote sensing estimation of water clarity for various lakes in China

Water clarity (expressed as Secchi disk depth (SDD)) reflects light transmission capacity of a water body and influences growth of aquatic plants, aquatic organisms, and primary productivity. Here, we calibrated and validated a general model based on Landsat series data for deriving SDD of various inland waters across China. The quality of remotely sensed reflectance products from different Landsat series images was assessed using in situ reflectance measurements. The results indicated that the products in the visible bands are the most robust and stable to estimate SDD for inland waters. Subsequently, a simple power function model based on red band was built using 887 pairs of in situ SDD measurements and concurrent Landsat images. The model was validated with an independent dataset of 246 SDD measurements, and the results showed that the mean relative error and normalized root mean square error were 34.2% and 55.4%, respectively. Finally, the model was applied to Landsat images acquired between 2016 and 2018 to investigate the SDD spatial distribution of all lakes with water area ≥ 10 km2 (total 641 lakes) in China. The estimation results demonstrated that the Eastern Plain Lake Zone and Northeast Plain Lake zone have relatively low SDD, with multiyear average SDD of 0.56±0.17 m and 0.47±0.29 m, respectively. The Yunnan‐Guizhou Plateau Lake Zone and Tibetan Plateau Lake Zone have relatively high SDD, with multiyear average SDD of 1.48 ± 0.86 m and 1.30 ± 0.83 m, respectively. The results indicated that the proposed model exhibits strong ability to accurately construct SDD coverage for various lakes.

The dynamics and release characteristics of microcystins in the plateau Lake Erhai, Southwest China.

Microcystins (MCs) have seriously polluted drinking water supplies and have caused great harm to aquatic organisms and humans. Understanding the dynamics of MC concentrations and its influencing factors is necessary for drinking water safety. Many previous studies on MC pollution focused on intracellular MCs rather than on extracellular MCs, which are more difficult to remove by water treatment. So far, the release characteristics of MCs and the relationships between intracellular and extracellular MCs are still unclear. To explore these questions, a survey was conducted at 18 sites across Lake Erhai from May 2014 to April 2015 as in Lake Erhai the frequency and coverage area of cyanobacterial blooms have been increasing. Variation of extracellular MCs lagged behind that of intracellular MCs. The highest value of intracellular MCs was 1.07μgL-1 in October 2014 and the highest extracellular MC concentration was 0.035μgL-1 in November 2014. Intracellular MCs were positively influenced by MC-producing cyanobacterial biomass, water temperature (WT), pH, and conductivity (Cond). The extracellular MCs showed little correlation with cyanobacterial abundances and intracellular MC concentrations, but showed significant negative correlations with WT, pH, and Cond. These results indicated that high biomass and high intracellular MC concentrations did not quickly lead to large releases of MCs, and that when cyanobacterial cells died and blooms disappeared, MCs were intensively released into the water, posing the greatest threat to drinking water supply.

Impacts of agricultural topdressing practices on cyanobacterial bloom phenology in an early eutrophic plateau Lake, China

Agricultural practices-induced pollution runoff has been widely acknowledged to be a significant source of nutrients fueling cyanobacterial bloom. The impact of topdressing activities on cyanobacterial bloom phenology (key parameters for depicting bloom process), however, has not been verified. Taking Lake Erhai, a typical eutrophic plateau lake, as an example, this study explored the spatio-temporal characteristics of phenological metrics and coverage extent for surface cyanobacterial bloom, based on phycocyanin pigment series retrieved from satellite and investigated the bloom responses to environmental forces. The results showed that higher intensity and earlier onset bloom with a larger coverage extent mainly occurred in the northern region. We identified three distinct cyanobacterial bloom growth patterns with large inter-annual variability in their bloom initiation timing (BIT). The earlier BIT is highly linked to elevated total nitrogen level and decreased wind speed. The bloom amplitude is mainly related to summer TN in 2003–2011, while associated with winter TN/TP ratio (TN, total nitrogen; TP, total phosphorus) during 2016–2019. Additionally, we found direct evidence linking agricultural topdressing and the BIT of a typical autumn bloom. After one week for the topdressing practice, the BITs lagged by approximately average 23 days, coinciding with high rainfall intensity. Our research demonstrates the topdressing activity should be reduced through agricultural planting adjustments. High TN and TP loss crops should be prohibited; planting adjustments should decrease high TP loss crop plantings in response to regional environmental forces.

Ecological Risk Assessment of Typical Plateau Lakes

Plateau lakes have significant ecological value. With economic development, lake pollution and ecological degradation have become increasingly prominent. There are many ecological risk assessment methods. This article combines four different ecological risk assessment methods including single-factor pollution index, geological accumulation index method, potential risk index method, and pollution load index method to analyze the heavy metal pollution in Yangzong seabed mud as comprehensively as possible. It shows that the results obtained by different ecological risk assessment methods are slightly different. The overall trends of the geological pollution index and the single-factor pollution index are similar. In terms of time, except for the two elements of mercury and cadmium, the contents of other heavy metals in 2019 are lower than in 2018, indicating that heavy metal pollution has decreased in 2019; from the perspective of spatial distribution, In 2018, the overall pollution level on the south side of Yangzonghai was higher than that in the central and northern regions of Yangzonghai . On the whole, whether it is the potential risk index or the appropriate pollution load index, the pollution level on the south side of Yangzonghai is higher than that in the central and northern areas of Yangzonghai, and the northern area has the least pollution.

基于生态系统敏感性与生态功能重要性的高原湖泊分区保护研究——以达里湖流域为例

基于生态系统敏感性与生态功能重要性的高原湖泊分区保护研究——以达里湖流域为例

Sewage Treatment System Planning for Dianchi Urban Wetland Park in Kunming

Dianchi Lake urban wetland park in Kunming is an important component of Dianchi lakeside wetlands, it is of great significance to the urban development and ecological protection of Kunming. To solve the problem of non-point source pollution of Dianchi Lake basin, the Dianchi Lake Pan-Asian International Urban Wetland Park is taken as an example, the rapid artificial infiltration treatment system and the comprehensive constructed wetland treatment system were designed for Dianchi Lake urban wetland park, and various design parameters and its influencing factors have been analyzed. After the deep treatment by the treatment system, the water quality reached the standards of landscape water. The planning of water system for Dianchi Lake urban wetland park provides a reference for designing plateau lake urban wetland parks.

Deep lake water balance by dual water isotopes in Yungui Plateau, southwest China

Stable isotopes of water (δ18O and δ2H) serve as a practical tool in the understanding of regional hydrological cycle, in particular, where the regional water cycle is stressed by both climate change and human activities. Lake water in southwest China is believed to play an important role in the local hydrology and possible modification of local climate. Water isotopes in lake systems are influenced by both the input water isotope and surface evaporation, such that they can be used as a natural tracer to evaluate these effects. Here we present a detailed water isotope balance study in a plateau lake – Fuxian Lake, the deepest and largest water body in Yungui Plateau, southwest China, with analogues of a steady state of water isotope equilibrium. The lake water isotopes are significantly enriched in heavy isotope due to evapoconcentration during the long residence time. We simulated the dual isotopes in the lake water using the Craig and Gordon model constrained by the observed water isotopes in lake water, river water, and atmospheric vapor. Results show consistent results for both δ18O and d-excess with values of −2.6‰ and −9.0‰ at the present relative humidity and E/I ratio. The test simulations also demonstrate how potential change in climate and/or lake water E/I ratio could impact lake water isotopes, and how the dual water isotope approach can unequivocally define the climatic and hydrological controls on lake water isotopes. These findings may be relevant for anticipating and detecting hydrological response to future climate change and water source management, e. g. inter - basin diversion projects. The results from this study highlight the potential of water isotopes in regional water cycle work, paleo climate reconstruction from lacustrine record, as well as human activity on water management.

Trophic niche and interspecific diet relationship of Gymnocypris in autumn from Langcuo Lake of Tibet, China.

Langcuo Lake is a typical plateau lake in the southern Tibet, with an altitude of 4300 m. Gymnocypris chui and Gymnocypris scleracanthus coexisted in this lake. In this study, we investigated the food composition and trophic niche of two Gymnocypris fishes in autumn by carbon and nitrogen stable isotopes technique in 2018. We further analyzed their interspecific diet relationship, including the diet similarity index and overlap coefficient. The results showed that G. chui mainly feed on ephemeroptera larvae, chironomidae larvae, periphytic algae, gammarus and plankton, while G. scleracanthus mainly feed on ephemeroptera larvae, periphytic algae, chironomidae larvae, gammarus and aquatic vascular plants. Two Gymnocypris fishes had trophic niche overlap. The δ13C range value (CR=1.60), δ15N range value (NR=1.89), and total area of convex hull (TA=1.80) of G. chui were lower than those of G. scleracanthus, with the difference values being 0.09, 0.57 and 1.29, respectively. The diet similarity index and overlap coefficient of those two species were higher, with a value of 94.2% and 91.5%, respectively. Our results suggested that the interspecific diet competition may be intense between the G. chui and G. scleracanthus in Langcuo Lake in autumn.

A Bigger Picture of how the Tibetan Lakes Have Changed Over the Past Decade Revealed by CryoSat‐2 Altimetry

AbstractTibetan lakes are an effective indicator of climate change as they are highly sensitive to and directly affected by climate change. The past decade has seen the seven warmest years on record globally. Such observations have prompted questions about lake changes over the Tibetan Plateau. The dense coverage of the CryoSat‐2 altimeter reveals large‐scale patterns in this climate change signal. We investigate lake level variations of more than 200 lakes using altimetry observations from CryoSat‐2 during the period 2010 to 2019. Combined with GRACE/GRACE‐FO, we evaluate the water storage change of lakes and terrestrial water storage (TWS). We find that most studied lakes generally went through three phases of change, that is, rising‐hiatus/decline‐rising, albeit lakes in the north Tibetan Plateau, show higher rising rates. Results also show that lake levels are widely affected by the 2015/16 El Niño event across the entire Inner Plateau via reduced precipitation. Above normal precipitation during 2016–2018, resulted in a sharp rise of ~1.22 m on average, accounting for 56% of the decadal lake level rise (mean/median: 2.19/1.85 m). TWS in the Inner Tibetan Plateau accumulated a net gain of 70.5 km3, which is dominated by the net gain of lake water storage (ca. 63.3 km3). The interannual TWS variation is found to be associated mainly with precipitation. In particular, extreme conditions such as the 2015/16 El Niño, had a profound negative impact on the TWS. The findings in this study shed new light on the response of Tibetan lakes to recent decadal environmental changes.

Dissolved inorganic carbon determines the abundance of microbial primary producers and primary production in Tibetan Plateau lakes.

Climate change globally accelerates the shrinkage of inland lakes, resulting in increases in both water salinity and dissolved inorganic carbon (DIC). The increases of salinity and DIC generate contrasting effects on microbial primary producers and primary production, however, their combined effects remain unclear in aquatic ecosystems. We hypothesized that increased DIC mitigates the constraints of enhanced salinity on microbial primary producers and primary production. To test this, we employed isotope labeling and molecular methods to explore primary production and four dominant types of microbial primary producers (form IA, IB, IC and ID) in lakes on the Tibetan Plateau. Results showed that DIC was positively correlated with the abundance of the form IAB and ID microbial primary producers and primary production (all P <0.001) and offset salinity constraints. Structural equation models elucidated that DIC substantially enhanced primary production by stimulating the abundance of form ID microbial primary producers. The abundance of form ID primary producers explained more variations (14.6%) of primary production than form IAB (6%) and physicochemical factors (6.8%). Diatoms (form ID) played a determinant role in primary production in the lakes by adapting to high DIC and high salinity. Our findings suggest that inland lakes may support higher primary productivity in future climate change scenarios.

Spatial distribution and ecological assessment of nickel in sediments of a typical small plateau lake from Yunnan Province, China.

Nickel (Ni) in small plateau lake sediments plays an important role in influencing the quality of lake ecosystems with a high degree of endemism and toxicity. This paper focuses on the spatial distribution and ecological risks of nickel in the sediments of Jianhu Lake, a small plateau lake in China, and the influence of pH and total organic carbon (TOC) on nickel concentrations. The results showed that average total nickel concentrations were 138.99 ± 57.57 mg/kg (n = 38) and 184.31 ± 92.12 mg/kg (n = 60) in surface sediments (0-10 cm top layer) and sediment cores (0-75 cm depth), respectively, and that the residual fraction was the main form of nickel. Simultaneously, through a semivariogram model, strong spatial dependence among pH, TOC, and the oxidizable fraction was revealed, whereas total nickel, exchangeable and the weak acid soluble fraction, reducible fraction, and residual fraction showed moderate spatial dependence. The vertical distribution revealed that nickel accumulated mainly in the bottom 5 cm (70-75 cm) of the sediment layer and that the pH was higher there, whereas TOC was concentrated mainly in the top 5 cm of sediment. Using geoaccumulation and a potential ecological risk index, moderate nickel pollution and moderate risk levels were found in most surface sediments, but moderate nickel pollution and high risk levels were observed in most sediment cores. In addition, pH and TOC were found to have a strong effect on the distribution and concentration of nickel and its fractions in the small plateau lake. In summary, nickel posed a certain degree of pollution and ecological risk, which deserves attention in the sediments of small plateau lakes.

Limited Contribution of Glacier Mass Loss to the Recent Increase in Tibetan Plateau Lake Volume

The Tibetan Plateau (TP) plays an essential role in the water supply to Asia’s large river systems and, as the largest and highest mountain plateau in the world, it drives the Asian monsoon and influences global atmospheric circulation patterns. The increase in TP lake volume since the mid-1990s is well documented, however the drivers of lake growth remain largely unexplained. In this study we investigate changes in lake and glacier volumes, together with changes in precipitation and evapotranspiration at basin scale. We calculate the contribution of glacier mass loss to the lake volume increase for the period 1994-2015. We demonstrate that glacier mass loss does have a limited contribution to the lake volume increase (19 ± 21 % for the whole TP). Glacier mass loss is thus insufficient to explain all of the lake volume gain, and despite large spread in various products that estimate precipitation and evaporation, we suggest that an increase in precipitation excess (precipitation - evapotranspiration) may be sufficient to explain the lake volume gain.

Hydrochemistry Differences and Causes of Tectonic Lakes and Glacial Lakes in Tibetan Plateau

The Tibetan Plateau has the largest lake cluster in China and in the world. In order to clarify the differences of lake hydrochemistry of Tibetan Plateau, water samples were collected from 32 lakes, including 22 tectonic lakes and 11 glacial lakes, along the Tibetan Plateau road, from September to October 2016. We detected and analyzed the major ion concentrations and characteristics of samples, and discuss the hydrochemistry type, controlling factors, and major ion sources of lake water. The results showed that, firstly, tectonic lake samples on the Tibetan Plateau have much higher physicochemical parameters and ion contents than glacial lakes, and Total Dissolved Solids (TDS) contents fluctuate from high to low latitudes. The variations of ion concentrations in the northern part of the Qiagui Co were more fluctuating and have two obvious peaks, while the variations in the southern part were moderate. The TDS of glacial lakes were low and leveling off in the upper and middle reaches of the basin, while higher and more variable in the lower reaches. Secondly, the tectonic lakes were mainly chloride saline lakes, with Na+ as the major cation, and SO42−, Cl− as the major anions. Glacial lakes were mainly carbonate and sulfate type lakes, Ca2+ and Mg2+ were the major cations, HCO3− was the major anion, and SO42− was the second. Thirdly, the hydrochemistry processes of the tectonic lakes were mainly controlled by evaporation-crystallization, and the ions mainly came from the evaporites of basin. Glacial lake water samples were mainly influenced by the weathering of basin rocks, with ion sources strongly influenced by the weathering of basin carbonates than evaporites, with calcite and dolomite being important sources of Ca2+, Mg2+, and HCO3−.

Study on the Release Potential of BPA and Steroid Estrogens in the Sediments of Erhai Lake, a Typical Plateau Lake of China.

On-site sampling analysis and laboratory-scale experiments were conducted to study the pollution status and release potential of EDCs in Erhai Lake. We found that nitrogen and phosphorus pollution in Erhai Lake sediment were both at a high level, as well as EDCs pollution. The concentrations of BPA, E2α, E1, E2β, EE2, and E3 were 36.84ng/g(DW), 13.04ng/g(DW), 128.97ng/g(DW), 52.57ng/g(DW), 18.48ng/g(DW) and 5.36ng/g(DW), respectively. The concentrations of E2α, E1, E2β and EE2 in the bottom water were higher than the surface water due to the impact of sediment release. The results of the 20days release test indicated that BPA release from the sediment had a greater correlation with the original concentration and the particle size of sediment, while the steroid EDCs had no obvious correlation with these two factors, probably due to the difference in hydrophobicity between them. Under hydraulic disturbance and aerobic conditions, the release process of EDCs was accompanied by a large amount of microbial degradation, and degradation amount > released amount. BPA was released quickly, 9.56% was released in 20days, but only 3.37% of steroid EDCs released. In comparison, the release process of steroids was longer and posed a greater threat to aquatic ecology.