Understanding the sources and dynamics of carbon burial in lake sediments is critical for reconstructing ecosystem evolution and assessing carbon sequestration potential under changing climate and anthropogenic pressures. However, systematic investigations of carbon burial in large shallow lakes in northern China under temperate and semi-arid climate remain scarce. Hulun Lake, the largest freshwater lake in northern China's drylands, provides a valuable archive for tracing carbon source changes due to its sensitivity to environmental variability. This study presents a comprehensive analysis of organic carbon (OC) burial dynamics in Hulun Lake through multi-proxy examination of sedimentary records since the 1850s. A total of 16 surface sediments in Lake Hulun showed heterogeneous OC distribution, with stronger terrestrial inputs (deduced from the predominance of long-chain n-alkanes) in the southeast and higher aquatic contributions (deduced from the predominance of mid/short-chain n-alkanes) in the central-western regions. Spatial differences were primarily driven by natural factors (e.g., precipitation gradients and water depth), with human activities intensifying OC burial in the northern region. Two sediment cores (northern S12 and southern S7) revealed spatiotemporal variations over the past century: the northern basin exhibited 2.34-fold higher OC burial rates (53.09 vs. 22.69 g/(m2 & sdot;a)) and greater terrestrial dominance (60-65% pre-1930s), while the southern basin showed lower burial rates and a stronger influence of aquatic sources. Since the 1930s, aquatic productivity has increased in both areas, and anthropogenic eutrophication post-1980s has further increased algal-derived OC (up to 23%), particularly in the north.

Lake ecosystems in arid and semi-arid regions play a pivotal role in deciphering how climatic dynamics and associated catchment processes modulate lake functioning. However, research on the responses of lake ecosystems in northeast China to large-scale climate oscillations since the deglaciation remains scarce. Here, we present a high-resolution paleolimnological record from Hulun Lake, the largest freshwater lake in northern China, derived from subfossil diatom assemblages and multiple geochemical and physical proxies, to examine how the lake ecosystem responded to East Asian Monsoon variability and local environmental changes since -17.0 cal kyr BP. The diatom record demonstrates that the lake ecosystem exhibited a highly sensitive and long-term response to post-deglacial climatic changes, predominantly mediated by climate-driven hydrological shifts and catchment processes. During Heinrich Event 1 (H1; 17.0-15.0 cal kyr BP), diatom abundance was generally low, with early community shifts toward benthic Fragilaria taxa and heavily silicified Aulacoseira granulata, which reflect the water level, likely triggered by enhanced meltwater inflow. Between 15.0 cal kyr BP and 11.0 cal kyr BP, rising temperatures coincided with increased lake levels and nutrient availability. A. granulata showed a transient increase, whereas cold-tolerant Fragilaria species reached peak abundances during the Younger Dryas (12.9-11.7 cal kyr BP). At the onset of the Holocene (-11.7 cal kyr BP), warming climate facilitated the extensive proliferation of A. granulata, while cold-water Fragilaria taxa declined sharply. During the mid-to-late Holocene, lake productivity increased, evidenced by elevated diatom concentrations, associated with nutrientrich conditions (TN, TOC). Redundancy analysis (RDA) emphasizes the strong indirect effect (temperature) of Holocene climate change on diatom community composition via hydrological and catchment-mediated pathways. Collectively, diatom variations in Hulun Lake over the past -17,000 years were shaped by climatic changes, which mediated shifts in lake productivity, water level, and trophic status, among which water level and trophic status are the primary driving factors. Our findings demonstrate that climate exerted an overarching control on the lake ecosystem, providing critical insights into the linkages between large-scale monsoonal variability and lake functioning in semi-arid northern China.

Lakes are known to play a crucial role in the world-wide carbon cycling due to the efficient organic carbon burial as well as large amount of CO2 emissions to the atmosphere. Despite the increasing importance of understanding these processes in the context of global warming and escalating human activities, the carbon source-sink dynamics of lakes remain elusive. In this study, we compared two approaches, a mass balance approach and the CO2 emission-carbon burial balance method to investigate the role of lake as carbon source or sink in Hulun Lake (the largest lake in northeastern China) from June 2015 to May 2016. Both approaches converged on the same conclusion that Hulun Lake was a great carbon source. With the overall mass balance calculations, total carbon input was 112.4x103 t during our study period, with the largest input was from the inlet rivers (107.5x103 t). The total carbon output was 448.2x103 t, and the CO2 emission accounted for about 99% of the output. The net carbon budget was -289x103 t, suggesting that Hulun Lake was a great carbon source. Furthermore, the total C-CO2 emission was three times higher than sediment carbon accumulation, stressing Hulun Lake was an important carbon source. The carbon source function mainly results from low primary production, long lake water residence time, high allochthonous carbon inputs (carbon derived from external terrestrial and atmospheric sources) and intensive human activities (e.g., grazing intensity up to 2.0 livestock units/ha, approaching the maximum stocking rate for Inner Mongolian grasslands). While further research is necessary to generalize these findings, our results provide compelling evidence for the significant role of lakes in the carbon cycle, and highlighting the importance of considering both carbon burial and carbon emission in assessments of the carbon sink-source function.

Hulun Lake, one of the largest inland lakes in the grassland region of northern China, has undergone distinct ecological changes over the past century due to both natural climatic shifts and human activities. Despite its ecological significance, the long-term drivers behind these changes are still not fully understood, especially the interactions between climate and anthropogenic influences on lake dynamics. To fill this gap, we analyzed sediment core from Hulun Lake, examining subfossil diatom assemblages, geochemical indicators, and sediment characteristics to reconstruct environmental changes and uncover the mechanisms driving them. Our findings reveal a shift from predominantly planktonic to periphytic/benthic diatom communities, associated with changes in nutrient levels and hydrological conditions. Key indicators, such as total phosphorus (TP) and sand content, showed strong correlations with diatom community composition, indicating that nutrient influx and water level fluctuations play crucial roles in lake ecosystem dynamics. Before 1935 AD, Hulun Lake’s ecology was primarily driven by natural climatic variations, supporting eutrophic species in stable, nutrient-rich conditions. From 1935 to 1970 AD, nutrient levels rose gradually, with parts of human impact. However, since 1970 AD, as human activities decrease and the warming and drying trend of rising temperature, reduced precipitation has led to a significant drop in the lake water level and a shrinking water area, which of them have significantly influenced nutrient dynamics and diatom composition. This study underscores the combined effects of climate change and human activities in driving the ecological evolution of Hulun Lake, providing valuable insights for the future conservation and management of similar semi-arid lake ecosystems.

The middle and lower reaches of the Yangtze River, a primary region for freshwater lakes in China, have undergone significant transformations throughout the Holocene. These changes, driven by factors such as sea-level rise, climate change, and human activities, have led to the progressive elevation of water levels in this area. As a result, a floodplain has emerged, characterized by the formation of numerous shallow lakes along the river course. However, the pattern of water-level changes in the main channel of the Yangtze River during the Holocene remains unclear. This gap in knowledge poses challenges for understanding sediment transport dynamics, the interactions between the river and its adjacent lakes, and the prevention and control of flood disasters in the Yangtze River basin. To shed light on these issues, our study compiled data on the surface elevation and water depth of 81 lakes in the mid-lower reaches of the Yangtze River basin. Additionally, we analyzed historical water-level records from the 1900s to the 1970s at eight gauging stations from Shashi to Jiangyin along the river’s main stream. Our findings reveal that, particularly along the Jingjiang section, the basal elevation of most lakes is lower than the Yangtze River’s water level during the dry season. Conversely, the water level of the main stream exceeds that of both the floodplain and the lakes enclosed by the Jingjiang embankment. In the tidal reach, especially within the Taihu Lake basin, the basal elevation of lakes typically falls below sea level. Meanwhile, lakes located along the section from Chenglingji to Wuhu exhibit basal elevations that correspond with the Yangtze River’s annual average and dry season water levels. Given the widespread presence of lakes along the middle and lower reaches of the Yangtze River, our study introduces a new proxy for reconstructing the mean water level of the mid-lower Yangtze River in the Holocene. By analyzing sediments from Nanyi Lake and Chenyao Lake in the lower Yangtze River, we attempted to reconstruct the water level of the Yangtze River’s main channel since 8 ka BP.

The freshwater lakes in the middle and lower reaches of the Yangtze River (MLYR) have been affected by a multitude of factors, including climate change and human activities, and are currently facing a range of aquatic ecological environment problems. In order to establish restoration goals and paths, it is essential to have a scientific understanding of the historical process and pattern of long-term degradation of the lake ecological environment. This study focused on Shengjin Lake, a representative Yangtze River-connected lake in MLYR. Based on the analysis results of cellulose carbon isotopes (delta C-13(cellulose)) in modern aquatic macrophytes, the response characteristics of aquatic macrophytes delta C-13(cellulose) to lake environment evolution were revealed by high-resolution multi-proxy (delta C-13(cellulose) of plant residues and geochemistry indices) analysis of a sediment core. The study also reconstructed the ecological environment evolution process of Shengjin Lake over the past two hundred years. The primary research findings are as follows: Firstly, the results of the modern process survey demonstrated that the delta C-13(cellulose) of different modern species exhibited considerable variation. The submerged plants exhibited an enrichment of C-13, while the emergent plants exhibited an enrichment of C-12. Secondly, a comprehensive modern process investigation, coupled with palaeo-limnological records and literature data, led to the conclusion that the large plant residues of sediments were primarily derived from submerged plants. Concurrently, statistical analysis indicated that the content of total organic carbon in lakes was the primary factor influencing the changes in sediment delta C-13(cellulose). The composition of delta C-13(cellulose) may be indicative of changes in lake primary productivity. Finally, the paleo-limnological record revealed that the ecological environment of Shengjin Lake has undergone significant changes over the past two hundred years. In particular, since the 1970 s, the delta C-13(cellulose) has been significantly enriched by C-12, and the geochemical indexes of elements have shown an increasing trend (p < 0.01). This suggests that the ecological environment of Shengjin Lake is gradually deteriorating as a consequence of human activities such as enclosure aquaculture and the construction of Huangpen Sluice, which have occurred in the context of climate warming and regional wind speed decrease in recent decades. This study presents new indicators and evidence for the reconstruction of the evolutionary process of the nutrient environment of lakes in MLYR. Moreover, it provides a foundation for the protection and restoration of lakes.

长江中下游地区是我国淡水湖泊主要分布区域之一.全新世以来受海平面上升、气候变化以及人类活动的影响,长江中下游水位抬升,形成了泛滥平原地貌,沿江发育了典型的浅水湖泊.但全新世长江干流水位变化的模式还不清晰,影响了对长江流域泥沙输移、河湖关系的深入理解以及对洪水灾害的防治.本研究收集了研究区81个湖泊的水位、水深等资料,以及长江干流沙市至江阴8个站点1900s～1970s期间的水位数据.对比发现,荆江河段内大部分湖泊湖底高程低于旱季水位,受人类筑堤等影响干流水位高于堤内平原、湖泊;感潮河段内湖泊尤其是太湖流域湖泊湖底高程基本低于海平面;城陵矶至芜湖河段内湖泊湖底高程约束在附近长江多年平均水位和旱季水位之间.基于此,本研究提出利用长江中下游广泛存在的沿江湖泊沉积物高程来重建全新世年平均水位的方法,并利用长江下游的南漪湖、陈瑶湖进行了8ka以来长江干流水位的重建.

Sea level changes during the Mid-Holocene directly influenced the Neolithic culture in the Yangtze River Delta region (YRD). However, the high-resolution sea level change characteristics for this period remain unclear. In this study, we performed a high-resolution palynological analysis, including pollen, Dinoflagellate cysts, and Foraminiferal organic linings, using a high-resolution sediment core from Shanglin Lake, in the North of Ningshao Plain (the south of Hangzhou Bay). 11 accelerator mass spectrometry 14C(AMS) datings indicate the age of the sediments range from 8 cal ka B.P. to 5.6 cal ka B.P. The results show that during the Mid-Holocene, Shanglin Lake evolved from an estuary – subtidal lagoon – semi-enclosed bay – semi-enclosed lagoon – semi-enclosed bay – enclosed lagoon to a modern freshwater lake. There was a period of no, or minimal, eustatic sea-level rise between 7733 and 7585 cal yr B.P. The Mid-Holocene high sea level comes in 7253–7082 cal yr BP. Between 7000 cal yr BP and 5502 cal yr BP, the sea level is close to modern value. The sea level change during this period had a significant impact on the local Neolithic human activity.

At present, East Taihu Lake has been profoundly affected by human interventions. However, the earlier limnological conditions such as the occurrence of temporal nodes and the cause of eutrophication remain unclear due to the short temporal range covered by the instrumental record. The stable carbon isotope ratio of plant residue α-cellulose (δ13Ccellulose) is a sensitive proxy indicator of palaeoproductivity, but this proxy index is rarely used in Chinese lakes. In order to test whether δ13Ccellulose can be used as a lake ecological environment changes indicator, we investigated the relationship between the δ13Ccellulose and several geochemical proxies from a ∼ 30 cm core extending 100 years obtained from a shallow lake: East Taihu Lake, China. Here, the changes in δ13Ccellulose of plant residues in sediments from East Taihu Lake were coupled analysis with geochemistry indexes to identify the response of δ13Ccellulose from plant residues to the past environmental changes. Combined with the results of C/N ratios, δ13Ccellulose and other related studies, the big plant residues in the sediments of East Taihu Lake may be derived from autochthonous aquatic macrophytes. In addition, the δ13Ccellulose showed a significant negative correlation with total organic carbon, probably indicating the changes of primary productivity of the lake. The δ13Ccellulose and geochemical proxy records revealed that the environmental changes in East Taihu Lake have undergone three distinct periods. The first period (1900s-1960s) represented a natural state without intensive human disturbance. The acceleration of lake eutrophication from the middle period (1960s-1995s) was a consequence of intensive local human activities. The late stage (1995s-2010s) represented a minor decline in nutrient levels after the implementation of ecological protection and restoration. By comparing the results with historical documents and measurements from East Taihu Lake, we inferred that anthropogenic pressures were the primary cause of the changes in the aquatic macrophyte communities and environments. This study provides a unique approach to the ecological environment evolution of East Taihu Lake. At present, Taihu Lake still suffers from annual cyanobacterial blooms due to economic growth (urbanization and industrialization). There is an urgent need for interventions to reduce nutrient inputs in order to enhance ecosystem resilience. Finally, the results of study of East Taihu Lake in China reveal the potential of combining δ13Ccellulose and other geochemical proxies to study palaeoenvironmental change, which provides new perspectives for understanding lake ecological environmental change in lakes.

The southeastern coastal areas of China represent one of the most populous and economically developed regions in China, but they are often severely affected by flood hazards. Therefore, studying the phenomenon and mechanisms behind extreme rainfall changes in this region is of great significance for economic and social development. In this study, we present high-resolution pollen and grain-size records from the Shanglin Lake located in Zhejiang, eastern China, based which changes in the frequency of paleo-flood events were reconstructed and the climatic context was inferred. Our pollen records show that the content of evergreen broadleaf trees gradually increased during 8000-7000 cal. yr BP, reflecting the gradually increasing temperature in the growing season. The content of Altingia increased substantially during the periods of 7960-7860, 7600-7500, and 7200-7100 cal. yr BP, especially in the first and last periods, indicating the prevalence of an El Nin similar to o-like condition in the study area during the early mid-Holocene warm period. Grain-size record shows that the prolonged El Nin similar to o condition facilitated a significant increase in flood frequency. Our results suggest that, similar to that of today, the early mid-Holocene warm climate was the most important factor controlling extreme hydroclimatic changes in the middle and lower reaches of the Yangtze River.

The ecological environment of grassland lakes is closely related to water security and human health in both arid and semiarid regions. The protection of freshwater and wetland ecological environments in grasslands promotes the stable and healthy development of ecosystems in arid and semiarid areas. In the present study, we investi-gated the long-term eco-environmental evolution of a typical grassland lake: Wulanpao Lake, located in the Hulun Lake Basin of northern China. This region represents the junction of areas subject to monsoons and those that are not and is arid or semiarid. We used the biological indicator of subfossil Cladocera, geochemical indices, and grain size from a well-dated sediment core. The ecological environment of Wulanpao Lake was influenced by climate change, consistent with a low trophic status, and the site developed aquatic vegetation between the 1860s and 1970s. However, the observed shift from predominantly littoral to planktonic Cladocera species was accompanied by ecological turnover (changes in the sedimentary environment and increases in trophic status and organic matter) when human activities began to impact the lake environment in the 1970s. This research provides an empirical foundation for managers and policymakers to protect similar grassland freshwater eco-environments.

As universal and supervirulent pollutants, understanding the potential sources of polycyclic aromatic hydrocarbons (PAHs) in lakes is critical for formulating pollutant control policies that will ensure the ecological safety of aquatic environments. Geographic heterogeneity of PAHs in lake sediments from China nationwide was investigated to indicate north-south dissimilarities in PAH levels and sources and propose specific PAH control strategies. Geographic PAH patterns showed that higher concentrations were found in the south compared to the north due to higher energy consumption and more intense industrial activities. Furthermore, the primary contributors in the south were high molecular weight (HMW) PAHs, whereas low molecular weight (LMW) PAHs were dominant in the north. The results of forward source apportionment based on the PAH emission method (EM) were consistent with the backward method using the positive matrix factorization (PMF) model, which verified the feasibility of the combined methods. Petroleum from transport was the dominant PAH source in the south, and purifying gasoline and diesel, promoting new energy vehicles and direct injection engines might effectively reduce PAH emission. Domestic coal was the main PAH source in the north, thereby adding active substance in coal and using cleaner energy could reduce PAH release.

Polycyclic aromatic hydrocarbons (PAHs) are of concern globally because of their carcinogenic, teratogenic, mutagenic, and bio-accumulative effects. Northern China is one of the regions in China with a high density of lakes; however, the lake aquatic environment is becoming seriously deteriorated, especially from PAH pollution due to the intensification of human activities during the past 100 years. Therefore, the spatial distribution and historical changes in PAHs in lake sediments from northern China were analyzed to indicate their response to anthropogenic emissions and pollution reduction actions. The ω(PAHs) in lake sediments ranged from 18.2 to 1205.0 ng·g-1, and low molecular weight PAHs were the dominant compounds. PAH concentrations increased from the 1950s to a peak level in the 2000s, which was induced mainly by increased energy consumption and rapid economy development, with PAH levels decreasing subsequently in the last 10 years due to craft improvement of wastewater treatment plants and the promotion of new energy policies. Spatially, PAHs pollution in Northeast and North China was more serious than that in Northwest China due to the higher level of economic development and energy consumption. Source apportionment results revealed that historical PAH emissions transferred from biomass combustion to a mixture of coal and petroleum combustion. In addition, the results of ecological risk assessment showed that the synthetic sediment quality index (SeQI) of northern China ranged from 36 to 75, and North and Northeast China posed higher ecological risk than that in Northwest China, with phenanthrene (Phe), acenaphthylene (Ace), acenaphthylene (Acy), and dibenzo(a,h)anthracene (DahA) as the main risk contributors.

A 150 cm long peat core was collected from a subalpine peatland (above sea level 1790 m) in Luoxiao Mountains,Hunan Province, China. Based on the analysis of AMS 14C dating, loss on ignition, total carbon, total nitrogen, grain size, humification, and pollen data, the environment change was reconstructed focusing on the intervals of the Younger Dryas (YD) event, the 4.2 ka event, and modern time. The pollen record indicates that deciduous broad-leaved trees occupied most parts of the study region and subtropical trees also grew at the lower elevation areas during the deglaciation. The percentages of Quercus (D) reached the highest during the YD, suggesting lowered temperatures than that of the pre-YD. Comparing with modern pollen assemblages, the relative abundance of Tsuga was lower during the 4.2 ka event, suggesting that the temperature were lower than that of the present. Regional comparisons of multiple proxy data in eastern China revealed that the climate was wet in northern China during the YD, which was probably related to the weakening evaporation effect and the strengthening Okhotsk High under low-temperature conditions. During the YD, the climate in the area dominated by the Indian monsoon was relatively dry in the southern part of eastern China. Meanwhile, in the East Asian monsoon-affected region, the climate was relatively wet during the YD in the southern part of eastern China, which was related to the weakening of the East Asian monsoon, El Ni??o conditions, and the West Pacific Subtropical High.

Shengjin Lake, which serves as an important National Nature Reserve, is suffering from chemical pollution due to rapid industrial and agricultural development in the circumjacent basin. Therefore, 168 anthropogenic toxic chemicals were determined to examine their spatial distribution and identify priority pollutants using a ranking system based on occurrence(O), persistence(P), bioaccumulation(B), ecological risk(E), and human health risk(H). Ecosystem and human health risks were also assessed. The spatial distribution of pollutants indicated that higher concentrations occur in the upper lake area compared to the middle and lower lake areas because of Jiang Dam. According to the derived priority pollutant list, phthalate esters(PAEs), organochlorine pesticides(OCPs), and heavy metals(HMs) are high-priority pollutants; polychlorinated biphenyls(PCBs), polycyclic aromatic hydrocarbons(PAHs), and volatile organic compounds(VOCs) are medium-priority pollutants; and antibiotics(ANTs) are low-priority pollutants. The ecology risk quotient(RQ) of the high-priority pollutants ranged from 4.3 to 15.9, indicating severe ecology risk to the aquatic organism, and higher risks were found in the upper lake areas. Additionally, the human health risk assessment revealed negligible carcinogenic risks associated with high-priority pollutants. The comprehensive ranking system established in this study can be applied to other lake basins by altering the measured concentrations to screen for priority pollutants, offering a scientific foundation for identifying priority control pollutants for watershed management.

通过测试南漪湖2008年、2014年和2015年沉积物柱芯中的环境放射性核素210 Pbex和137 Cs,辅以相互印证的210 Pb CRS计年模式和137 Cs定年时标方法,定量估算了南漪湖过去百余年间的沉积速率变化;基于遥感目视解译方法获得了南漪湖1985—2016年湖泊面积时空变化,结合构建的湖泊泥沙输移模型,定量估算了南漪湖出湖河流的年均泥沙输移量;基于此,进一步分析了湖泊沉积速率和泥沙输移通量与湖泊面积变化之间的相关关系.结果表明:南漪湖同一湖区不同年份沉积物柱芯剖面中210 Pbex和137 Cs比活度分布特征相近,210 Pbex比活度遵循随深度增加而减小的趋势,137 Cs则在24和16 cm左右分别记录了1954年首次沉降和1963年最大沉降蓄积峰值;南漪湖沉积速率整体呈现波动变化趋势,在20世纪50年代前后沉积速率出现极大值,随后至采样年份该沉积速率呈缓慢上升趋势,这种变化可能与不同历史时期的自然因素和人类活动密切相关;过去31年间,南漪湖湖泊面积整体上呈缩小趋势,减少了57.37 km2,主要集中于西北、东北和东南部等区域,湖泊周边过度围垦是影响湖泊面积变化的主导性因素;南漪湖出湖河流的年均泥沙输移量约为1904.60 t∕a,湖泊沉积速率和泥沙输移通量受湖泊面积变化影响较大,随着湖泊面积的增加,湖泊沉积速率和泥沙输移通量分别呈指数降低和线性增加的趋势.

Owing to the intensification of human activities, urban lakes serving as important freshwater resources are becoming seriously deteriorated, especially due to persistent toxic substance (PTS) pollution. Therefore, the spatial distribution and sediment record of PTS in urban lake sediments in the middle Yangtze River Basin were investigated to indicate its response to anthropogenic emission and pollution reduction actions. Spatial distribution of typical PTSs (polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) included) showed that pollutants were concentrated in the southeast and center of the urban lake due to riverine inputs suffering from both petrochemical and municipal wastewaters. The sedimentary record of PAH concentrations indicated an increase from the 1960s to a peak level in the 2000s, which was induced mainly by increased PAH emissions, with PAH levels decreasing subsequently due to craft improvement of wastewater treatment plants (WWTPs). Source apportionment results revealed that historical PAH emissions transferred from petrogenic sources to a mixture of energy combustion and petrochemical industry. Furthermore, OCP and PCB pollutions reached peak levels in 1980s, which is consistent with their historical usage for agricultural and industrial production. From the synthetic sediment quality index (SeQI) analysis, sediment quality in nearly half of sites was poor, while the sediment record suggested that sediment quality had turned better since 2000s maybe due to the WWTP improvement. Furthermore, significant correlations (p < 0.05) between PTS levels and the ratio of PAH emissions to the number of WWTPs documented the PTS levels in response to the surrounding anthropogenic pollution and WWTPs in urban lakes.

Recent work at the early Shang period type site in Panlongcheng, Hubei Province, China, provides a new understanding of changes in the landscape and water environment over time. In the past few decades, the research at this site has obtained important results and shown progress in many aspects, but few scholars have discussed the geomorphological environment of Panlongcheng, especially the water environment. Researchers have long believed that the present-day environment and landscape of Panlongcheng are no different than during the early Shang period. However, recent archaeological discoveries indicate that there may still be some cultural remains underwater. Therefore, we used a combination of underwater surveys, drilling and digital mapping to expand our knowledge of the landscape of Panlongcheng during the early Shang period. This included mapping the lake basin using single-beam echo sounders and drilling to preliminarily observe the stratum and collect samples from underwater. We also conducted radiocarbon dating on the samples collected from the bottom of the lake. The results suggest that there might not have been a lake during the early Shang period. Therefore, the landscape and environment of Panlongcheng and other related issues should be reexamined. In addition, we hope the methods used in this study can provide a reference for related archaeological work in shallow water areas in inland China.

At present, most lakes in the world are facing the threat of eutrophication, especially mesotrophic lakes, which are in a critical period of ecosystem transformation. However, how the internal biological composition and structure of these lakes change accordingly has not yet been explored extensively. Here, a paleolimnological evaluation of subfossil Cladocera was initiated to study ecological and hydrological environmental changes in Nanyi Lake, which is a large (203 km(2)) shallow freshwater lake in the lower reaches of the Yangtze River Basin, China. In this study, subfossil Cladocera data combined with several geochemical proxies from three well-dated sediment cores were obtained. Both the sedimentary subfossil Cladocera and the modern Cladocera in the water column indicated that Bosminidae was the dominant species in Nanyi Lake. We observed that the changes in the density of Bosminidae and Cladocera had strong ties to changes in the cultivated land area, which could cause the obvious alteration of the sedimentation rate around the lake. In addition, the ratio of planktonic species to littoral species (P/L ratio) in Nanyi Lake responded to the occurrence of several extreme hydrological phenomena, such as flooding corresponding to a high P/L ratio and drought corresponding to a low P/L ratio, during the past 200 years. The analysis of Cladocera assemblages and the geochemical indices of the three cores in Nanyi Lake indicated increases in trophy and water levels, especially since the modern 1970s.

Lakes in arid and semi-arid regions are experiencing dramatic variations in water level and volume, which has caused severe ecological and social problems. Long-term study of the lake dynamics in arid/semi-arid regions could provide particular insights into the mechanisms driving lake variations, while hydro-meteorological data were usually limited in these regions, especially before the instrumental period. In the present study, we focused on a typical great lake - Hulun Lake in semi-arid region in northern China, simulated the hydrological processes from 1904 to 2016 using SWAT model, CRUNCEP7 reanalysis data, and sparse records of lake level during 1900s-1950s, and investigated the mechanisms driving the dramatic variations of the lake at the hundred-year time scale. Results illustrated that the simplified Penman equation by Valiantzas (2006) could reproduce the evaporation dynamics of Hulun Lake, with monthly R2 being 0.93-0.95. The long-term simulation since 1904 reproduced runoff dynamics, which were consistent with the dramatic variations of lake level over hundred years. The largest water level increase (~5.0 m in 1950s) and decrease (~4.5 m in 2000s) during 1904-2016 were jointly affected by river runoff, lake evaporation, and precipitation into the lake. Both the positive/negative phase and the multi-decadal trend of PDO clearly influenced the hydrological cycle of Hunlun Lake, especially for the period of 1904-1950 with low lake levels. Overall, the present study provided a methodology for investigating the hundred-year hydrological processes for lakes in semi-arid regions in northeastern Asia.