Liao River Estuary Research Articles

Runoff variation alters estuarine sediment microbiome and nitrogen removal processes by affecting salinity

Runoff variations shape the dynamics of the estuarine environmental factors, profoundly influencing the nitrogen cycle in estuarine sediments. However, our understanding of how these changes regulate microbially-mediated nitrogen removal processes remains limited. In this study, the impacts of changes in environmental factors caused by normal and low runoffs on denitrification and anammox in sediments of the Liao River Estuary in China, were investigated, using continuous-flow experiments combined with 15N tracing techniques and molecular methods. Results indicated that denitrification was the main nitrogen removal process in estuarine sediments under both runoff conditions. Elevated salinity under low runoff condition increased the abundance of nitrifying bacteria (Nitrospina, Nitrosomonas and Nitrosomonadaceae), thereby promoting the coupled nitrification-denitrification nitrogen removal process. Furthermore, seawater intrusion under low runoff contributed to dilute nitrite concentrations, resulting in decreased denitrification rates in sediments. Overall, this study highlighted the impacts of runoff variations on biological nitrogen removal process through affecting environmental factors, gene abundance and microbial community in the estuary.

Identifying loss threshold and migration trajectory in the management of Suaeda salsa wetland under coastal squeeze

The coastal salt marsh wetland is mainly located in the tidal area where sea and land are intertwined, which has the functions of promoting silt and consolidating beach, wave reduction and disaster reduction, and is an ecological barrier against erosion in the coastal zone, which has important ecological value. Nevertheless, owing to the intricate nature of wetland species formation mechanisms and community distribution patterns, the impact of coastal squeeze on Suaeda salsa wetlands loss may not exhibit a linear relationship, necessitating further elucidation of the specific processes involved. Precisely understanding the extent to which coastal squeeze affects the threshold of loss in the Suaeda salsa wetland holds immense importance in safeguarding the distinctive red beach landscape. Furthermore, it represents a pivotal scientific challenge that necessitates resolution in the management of coastal wetlands for their protection and restoration. Hence, drawing upon the theoretical framework concerning the impact of coastal squeeze on the degradation of coastal Suaeda salsa wetland, this study employs the representative silty coastal region of China's northern Liaodong Bay as a case study to conduct empirical investigation. The research integrates Landsat imagery and digital elevation data, and incorporates spatial autocorrelation, elastic coefficient analysis, and barycenter model analysis to examine the threshold of degradation and spatial variations of Suaeda salsa wetland in response to coastal squeeze. The results show that: (1) The risk intensity of coastal squeeze in the study area exhibited a pattern of initial decline followed by an increase from 1995 to 2020, with the highest risk areas predominantly located in the development zone on the eastern bank of the Liao River Estuary. (2) There was a positive correlation between the growth of the coastal squeeze index and the loss of the Suaeda salsa wetland. When the proportion of area in which the coastal squeeze deteriorates reached 43.9%, the Suaeda salsa wetland lose resilience against the impact of coastal squeeze, leading to an intensified rate of loss. (3) Compared with the west side of the Liao River, the critical area of coastal squeeze and the loss barycenter of the Suaeda salsa wetland on the east side of the Liao River have a greater range of changes. The planning and management of coastal ecological restoration necessitates considering the occurrence conditions of the coastal squeeze impact threshold on the loss threshold of wetland and the migration characteristics of the wetland loss area. This approach enables the timely control of coastal squeeze risk intensity in the area and the preservation of wetlands' resistance to external disturbances. Consequently, it holds immense importance for the sustainable development of coastal wetlands.

Mapping Suspended Sediment Changes in the Western Pacific Coasts

The Western Pacific Coasts (WPC) are the outlets of many large Asian rivers. In recent years, the interplay of climate changes and human activities has persistently altered the suspended sediment concentrations (SSC) in the WPC, triggering substantial shifts in coastal ecosystems. However, the scarcity of coastal observation stations hampered comprehensive investigations at large scales. This study employed three representative SSC retrieval models and utilized Landsat images acquired from 1990 to 2020 to estimate the SSC in the WPC with a focused endeavor to dissect the intricate spatial and temporal variability of SSC in the region. The findings revealed the following insights: (1) The outcomes derived from the three distinct SSC models consistently manifested a discernible decreasing pattern in SSC changes over the past three decades across all six major estuaries (Liao River Estuary, Yellow River Estuary, Yangtze River Estuary, Hangzhou Bay, Pearl River Estuary, and Mekong River Estuary). (2) The seasonal attributes of the six major estuaries differed, primarily due to distinct dominant influencing factors like precipitation, upstream sediment load, wind, and tides. (3) Collectively, SSC tends to be relatively higher in the Yangtze River Estuary, Hangzhou Bay, and Yellow River Estuary, while the Pearl River and Mekong River Estuaries exhibit relatively lower levels. Notably, the SSC exhibited distinct spatial traits along the coastlines of different estuaries. (4) SSC in the non-estuarine regions along the WPC, a similar significant declining trend in SSC is observed as in the estuaries, albeit the rate of decline generally appeared to be less pronounced. Furthermore, regions with faster rates of SSC reduction are typically concentrated near major estuaries in the northern part of the Coasts. The decline in estuarine SSC plays an important role in the overall decrease in SSC across the WPC. These study outcomes held substantial significance for advancing the stability and sustainable evolution of the WPC.

Field survey and analysis of water flux and salinity gradients considering the effects of sea ice coverage and rubber dam: a case study of the Liao River Estuary, China

Predicting net river fluxes is important to promote good water quality, maritime transport, and water exchange in estuaries. However, few studies have observed and evaluated net water fluxes to estuaries under complex conditions. This study used advanced survey techniques to obtain high-frequency monitoring data of cross-sectional current velocity, water level, and salinity in the Liao River Estuary (LRE) from 2017 to 2020. The net water flux into the sea was computed based on field data and the impacts of the rubber dam and sea ice cover on water flux and salinity processes were analyzed in the study region. In the Liao River Station (LRS), the fluctuations of water level and discharge were not obvious in winter due to the sea ice cover. There were significant seasonal and inter-annual changes in water fluxes due to variability in river discharge and tidal oscillations. The results also showed that the net water flux into the sea from the LRS was positive in wet season, and greater during ebb tides than flood tides. The net water fluxes in the normal and dry seasons were mostly negative due to the influence of tides, indicating that the annual runoff from the Liao River fluctuated greatly throughout the year. The water flux in the LRS was more suitable for representing water flux into the sea than the Liujianfang Hydrometric Station (LHS) in the LRE. The impacts of the rubber dam and Panshan Sluice on water fluxes to the sea were both significant. Lower salinity in the study area coincided mostly with height water fluxes to the sea and periods when the rubber dam was raised. This study results provide us new insights to measure the water flux into sea under the condition of ice cover in the tidal reach of estuary and the method can be used for water flux observation for other estuaries.

Succession and environmental response of sediment bacterial communities in the Liao River Estuary at the centenary scale

Microbial community succession in turbulent estuarine environments is key to the understanding of microbial community development in estuaries. Centennial-scale sediment core samples collected from the Liao River Estuary (LRE) channel bar and side beaches were studied for geochemistry and 16S rRNA gene-based bacterial analyses. The results showed that bacterial community composition significantly differed between the sediments of the two sides of the channel bar, with Campilobacterota and Bacteroidota being dominant bacterial phyla in the tributary (T1, T2) and mainstream (MS1, MS2) sediment, respectively. Co-occurrence network of the bacterial community at the genus level showed more centralized and compacted topological features in tributary with weaker hydrodynamic, and the keystone taxas were Halioglobus, Luteolibacter, and Lutibacter in the bacterial community. The bacterial network structure had more edges and larger average degree in LRE sediments from the stage of the year 2016–2009 and the stage before 1939, which was possibly related to hydrodynamic conditions and nutrients. Stochastic processes (dispersal limitation) were the key factors driving bacterial community assembly in the LRE sediments. In addition, total organic carbon (TOC), total sulfur (TS), and grain size were the main deterministic factors affecting the change of bacterial community structure. Relative microbial abundance has the potential to indicate geologically historical environmental changes. This study provided a new perspective to reveal the succession and response of bacterial communities under frequent fluctuation environments.

Temporal trends of organophosphate esters in a sediment core from the tidal flat of Liao River estuary, Northeast China

The historical trends and inventory of organophosphate esters (OPEs) were investigated based on depth profiles of OPEs in sediment core collected from the tidal flat of the Liao River estuary in northeastern China. The concentration of ∑13OPEs in sediment core has increased continuously since records began, reaching a peak of 10.8 ng g-1 dry weight (dw) in the 1960s, then began to decline and fall to a low of 3.91 ng g-1 dw in the 1980s, before rising again and increasing to 20.4 ng g-1 dw in the 2000s. After a brief decline, It started to increase again and reached a peak of 27.0 ng g-1 dw in 2018. Tributyl-n-phosphate was found in each layer of the sediment core, accounting for 31.9 - 100% of ∑13OPEs. The fluxes of OPEs ranged from 46.5 to 105 ng cm-2 y-1 in the sediment layers deposited between 2007 and 2018. The inventory of OPEs in the sediment core was estimated to be 1541 ng cm-2. This work reports for the first time the historical contamination trends of OPEs in Chinese sediments, which is important for assessing the environmental risk of OPEs.

Benthic Microbial Communities and Environmental Parameters of Estuary and Hypoxic Zone in the Bohai Sea, China

The sediment microbial community plays a key role in the cycling of organic matter in marine ecosystems. The characteristics of the sediment microbial community are significantly related to changes in the environment. In this study, we analyzed the diversity and distribution of microbial communities in sediments from different geographical regions (the Liao River estuary, Yellow River estuary, hypoxic zone, and offshore zone) of the Bohai Sea using high-throughput sequencing. The results showed that the community richness and diversity (especially the unique diversity) of the Liao River estuary were larger than those of the Yellow River estuary, hypoxic zone, and offshore zone. The phylum Proteobacteria dominated in the Liao River estuary (46.26%), hypoxic zone (76.19%), and offshore zone (69.79%), while the dominant phylum in the Yellow River estuary was the Bacteroidetes phylum. The genus Gillisia was the dominant genus in both the Liao River estuary and Yellow River estuary. The offshore zone and hypoxic zone shared the same dominant Photobacterium genus. The results of Pearson correlation and redundancy analysis showed that environmental parameters such as nitrite, silicate, nitrate, phosphate, ammonia, dissolved oxygen, pH, and salinity interfered significantly with the structure and diversity of the microbial community. The results of this study will provide support for future research on the interaction mechanism of pollutants and microorganisms in the estuaries and a typical hypoxic zone of the Bohai Sea.

Recording and modeling the seasonal growth of salt marsh vegetation at Liao river estuary, China, based on the wetland image monitoring system (WIMS)

Recording and modeling the seasonal growth of salt marsh vegetation at Liao river estuary, China, based on the wetland image monitoring system (WIMS)

Landscape pattern changes and its drivers inferred from salt marsh plant variations in the coastal wetlands of the Liao River Estuary, China

Coastal wetlands are important ecosystems that connect land to open sea, and their service functions are important in estuaries globally. Using long time series of remotely sensed information, transfer matrix and direction of landscape types from 1986 to 2020 in the coastal wetlands of the Liao River Estuary (LRE) were selected to investigate landscape pattern changes. And the dynamic response of Suaeda salsa (S. salsa) to hydro-climatic factors were explored using partial correlation and nonlinear analysis. The results suggested that landscape fragmentation and abundance have increased with frequent disturbance in the LRE over the last three decades, and more than 60 % of S. salsa, tidal flats, and water transitioned into buildings, farmland, and Phragmites australis (P. australis) in the study area. Further analyses of dynamic response of landscape metrics to influence factors indicated that the main drivers forcing landscape pattern changes in coastal wetlands in the LRE were socio-economic factors, followed by natural factors. The S. salsa spatial variations were positively correlated with river discharge and precipitation but without significant correlation with temperature in the early growing stages of vegetation (P < 0.05) in the coastal wetlands of the LRE, which implied that S. salsa growth mainly relies on river discharge and precipitation by reducing water salinity. Present study may provide new insights into restoration guidance and environmental management for coastal wetland protection.

Morphological Characteristics and Hydrological Connectivity Evaluation of Tidal Creeks in Coastal Wetlands

Tidal creeks play a critical role in delivering water, suspended sediments, and nutrients to coastal wetlands, so it is important to understand the characteristics of the tidal creek system to guide the development and sustainable utilization of coastal wetlands. Using the coastal wetlands of the Liao River Estuary (LRE) as a study area, this study accurately divided the tidal flat based on the principle of tidal correction, extracted the linear features of tidal creeks using high-resolution remote sensing (RS) data, and then classified the tidal creeks on a tidal flat using the tidal creek ordering algorithm. Our study aimed to quantify the morphological characteristics of tidal creeks and qualitatively evaluate the parameters of the tidal creek network in the study area. The study results show obvious spatial heterogeneity in the order and the average length of tidal creeks in the coastal wetlands of the LRE. With the increase in the order of tidal creeks, the average length of tidal creeks increased exponentially and the number of tidal creeks decreased exponentially in the study area. The total density of tidal creeks was related to the beach surface elevation gradient, and the density and frequency of tidal creeks reduced substantially with an increase in the order of tidal creeks. The sinuosity ratio of tidal creeks declined sharply with a fall in the beach surface elevation gradient. The average bifurcation ratio of tidal creeks in the upper intertidal zone was higher than that in other zones, indicating that the tidal creeks in the upper intertidal zone were erratic. In addition, the hydrological connectivity of the tidal creek network in the upper intertidal zone and the development of the tidal creek system in the supratidal zone were the highest in the LRE. The study results help understand the spatial variations in tidal creek morphology under the influence of tidal hydrodynamics.

Ecological environmental quality assessment of Chinese estuarine wetlands during 2000–2020 based on a remote sensing ecological index

Coastal estuarine wetlands are important transition zones between rivers and oceans and are extremely rich in biodiversity. In recent years in China, large-scale reclamation and development of coastal cities have imposed serious pressures on coastal ecosystems. Thus, assessing the ecological quality of estuarine wetlands is extremely important for sustainable development. Our study focuses on four typical estuarine wetlands at the mouths of the Yangtze, Yellow, Liaohe and PearRivers. Their ecological quality between 2000 and 2020 was assessed using a remote sensing ecological index (RSEI), which was derived from several remote sensing indexes processed via the online Google Earth Engine platform. From 2000 to 2020, the RSEIs of coastal wetland increased from 0.42 to 0.63 in the Liao River estuary, 0.27 to 0.45 in the Pearl River estuary and from 0.47 to 0.54 in the Yangtze River estuary, and decreased from 0.56 to 0.49 in the Yellow River estuary. The spatial distribution in ecological environmental quality was significantly clustered. High-high clusters occurred mainly in areas of lush vegetation, while low-low clusters were mostly found in built-up areas or coastal zones. Aquacultural and built-up areas had negative impacts on the ecological environment, while vegetation cover had a positive influence. The quality of the ecological environment within these wetlands has gradually improved due to the environmental management policies of national and local governments. This approach to evaluating the ecological quality of estuarine wetlands using the RSEI and Google Earth Engine provides critical information to inform sustainable development policy.

Anthropogenic influences on genetic diversity and differentiation of the clearhead icefish (Protosalanx hyalocranius), as revealed by mitochondrial and microsatellite DNA markers

The clearhead icefish, Protosalanx hyalocranius, is an economically important fishery species in China. For the past few decades, the wild resources of P. hyalocranius have markedly decreased due to human activities such as overfishing, hydro-projects and water pollution. Meanwhile, P. hyalocranius has been widely introduced into lakes and reservoirs of northern China and some have become established, invasive populations, leading to detrimental effects on ecosystems. Using mitochondrial control region sequences and nine microsatellite DNA markers, the aim of this study was to assess to what extent human activities could impact the genetic diversity and population structure of P. hyalocranius, and explore the sources of the invasive Heilong River population based on genetic characterization. Based on mitochondrial DNA, the average haplotype diversity and nucleotide diversity among six populations were 0.737 and 0.0029 respectively. Based on microsatellite markers, the observed (HO) and expected (HE) heterozygosities in each population ranged from 0.481 to 0.565 and 0.478 to 0.565, respectively. Both mitochondrial and microsatellite markers indicated the genetic diversity in Chaohu Lake was the lowest. HO and HE of the two anadromous populations (Liao River Estuary and Yalu River Estuary) were close to Chaohu Lake and relatively low among all populations. The pairwise Dest values showed high and significant genetic differentiation between Taihu Lake and other populations. There was no evidence of genetic differentiation between Chaohu Lake and the two anadromous populations. No significant reduction of genetic diversity was observed in the Heilong River population. Bottleneck analysis showed that the two anadromous populations may have experienced a recent genetic bottleneck. DIYABC analysis suggested that the sources of the invasive Heilong River population were Taihu and Hongze lakes, with a greater genetic contribution from Hongze Lake. Therefore, the anadromous populations of P. hyalocranius may have suffered more impacts from human activities than the strictly freshwater populations. Among freshwater populations, Chaohu Lake should also be paid more attention in fisheries management. In addition, our study demonstrated that multiple introductions can give rise to high genetic diversity in an invasive population.

TEMPORAL AND SPATIAL EVOLUTION CHARACTERISTICS OF LAND USE AND LANDSCAPE PATTERN IN KEY WETLAND AREAS OF THE WEST LIAO RIVER BASIN, NORTHEAST CHINA

The impact of the wetland ecosystem on arid and semi-arid areas is much higher than that in humid areas. It plays a more significant role in regulating climate, conserving water sources, purifying water bodies, and protecting biodiversity. The West Liao River Basin is located in a moderately temperate, semi-arid, and continental monsoon climatesensitive area, with a fragile ecological environment. Climate warming and drought have gradually caused dry-flow of some river sections in the basin, reduction in the water area, shrinking of wetlands, degradation of vegetation ecological function, and decline of biodiversity. Ultimately, the effect of ecological barriers is significantly weakened. The research of the temporal and spatial evolution of landscape patterns and their relationship with human activities in arid and semi-arid regions is of great significance for the protection and restoration of wetland resources. Based on Landsat remote sensing images in 1985 and 2015, the temporal and spatial evolution of landscape patterns in four key wetland areas in the West Liao River Basin was studied by 3S technology and landscape ecology indexes. Results show that during the 30a years, the wetland resources area in the West Liao River Basin is drastically reduced. Wetland resources of the four study areas, the Dalinor, the Saihanwula, the Hongshan Reservoir, and the West Liao River Estuary, were decreased by 13.80%, 31.06%, 61.10%, and 66.03%, respectively. The reduced wetland resources in the Dalinor and the Saihanwula were mainly converted into grassland, while those of the Hongshan Reservoir and the West Liao River Estuary were mostly converted into farmland. The diversity and evenness indexes of landscape in the Hongshan Reservoir and the West Liao River Estuary are gradually decreasing. The diversity and evenness indexes of the Dalinor and the Saihanwula are not significantly changed but are slightly disturbed by human activities. Changes in the landscape pattern index highlight the decrease in the water area, the increase in the area of dry and paddy fields, and the improvement of sandy land. All these further reflect that insufficient water resources supplementation and increasing human disturbance have a profound impact on the landscape pattern, which has also become the main driving force for the evolution of the landscape pattern in the West Liao River Basin.

Potentially Toxic Metals in Sediments from Liao River Estuary Wetland: Concentration, Source, and Risk Assessment

AbstractIn this study, a total of 26 surface sediments samples are collected from the Liao River estuary wetland, China. The concentration, potential ecological risk, and source apportionment of potentially toxic metals including Sr, Zn, Cr, Ni, Pb, Cu, and As in different seasons are analyzed. The average concentrations of potentially toxic metals are below the first class of Chinese marine sediment quality standard. There is no significant difference in the concentrations of potentially toxic metals in the sediments collected in June and November. The concentrations of potentially toxic metals in the periphery of the nature reserve are higher than those in the core area of the nature reserve. The average enrichment factors of As, Pb, Cu, Ni, Zn, and Cr are about 1, classified as minimal enrichment. The average enrichment factor of Sr is &gt;2, which corresponds to moderate enrichment. The individual (Er) and total potential ecological risks (RI) of potentially toxic metals are low. The positive matrix factorization model suggested that the potentially toxic metals in surface sediments in June are dominantly from atmospheric deposition, industrial discharges, natural sources, and traffic emission. However, the traffic emission source is replaced by agricultural production and metal smelting activities in November.

Assessing the Ecosystem Health of Coastal Wetland Vegetation (Suaeda salsa) Using the Pressure State Response Model, a Case of the Liao River Estuary in China.

Suaeda salsa (S. salsa) is an important ecological barrier and tourism resource in coastal wetland resources, and assessing changes in its health is beneficial for protecting the ecological health of wetlands and increasing finances. The aim was to explore improvements in the degradation of S. salsa communities in the Liao River Estuary National Nature Reserve since a wetland restoration project was carried out in Panjin, Liaoning Province, China, in 2015. In this study, landscape changes in the reserve were assessed based on Sentinel-2 images classification results from 2016 to 2019. A pressure-state-response framework was constructed to assess the annual degradation of S. salsa communities within the wetlands. The assessment results show that the area of S. salsa communities and water bodies decreased annually from 2016 to 2019, and the increased degradation indicators indicate a state of continued degradation. The area of types such as aquaculture ponds and Phragmites australis communities did not change much, while the estuarine mudflats increased year by year. The causes of S. salsa community degradation include anthropogenic impacts from abandoned aquaculture ponds and sluice control systems but also natural impacts from changes in the tidal amplitude and soil properties of the mudflats. The results also indicate that the living conditions of S. salsa in the Liao River estuary wetlands are poor and that anthropogenic disturbance is necessary to restore the original vegetation abundance.

Continuous Change Mapping to Understand Wetland Quantity and Quality Evolution and Driving Forces: A Case Study in the Liao River Estuary from 1986 to 2018

Coastal wetland ecosystems, one of the most important ecosystems in the world, play an important role in regulating climate, sequestering blue carbon, and maintaining sustainable development of coastal zones. Wetland landscapes are notoriously difficult to map with satellite data, particularly in highly complex, dynamic coastal regions. The Liao River Estuary (LRE) wetland in Liaoning Province, China, has attracted major attention due to its status as Asia’s largest coastal wetland, with extensive Phragmites australis (reeds), Suaeda heteroptera (seepweed, red beach), and other natural resources that have been continuously encroached upon by anthropogenic land-use activities. Using the Continuous Change Detection and Classification (CCDC) algorithm and all available Landsat images, we mapped the spatial–temporal changes of LRE coastal wetlands (e.g., seepweed, reed, tidal flats, and shallow marine water) annually from 1986 to 2018 and analyzed the changes and driving forces. Results showed that the total area of coastal wetlands in the LRE shrank by 14.8% during the study period. The tidal flats were the most seriously affected type, with 45.7% of its total area lost. One of the main characteristics of wetland change was the concurrent disappearance and emergence of wetlands in different parts of the LRE, creating drastically different mixtures of wetland quality (e.g., wetland age composition) in addition to area change. The reduction and replacement/translocation of coastal wetlands were mainly caused by human activities related to urbanization, tourism, land reclamation, and expansion of aquaculture ponds. Our efforts in mapping annual changes of wetlands provide direct, specific, and spatially explicit information on rates, patterns, and causes of coastal wetland change, both in coverage and quality, so as to contribute to the effective plans and policies for coastal management, preservation, and restoration of coastal ecosystem services.

Habitat changes in the most important stopover sites for the endangered red-crowned crane in China: a large-scale study.

The red-crowned crane (Grus japonensis) is an endangered bird species that has been listed as one of the Class I National Key Protected Wild Animals of China. This study analyzed the habitat changes in the two most important stopover sites for red-crowned crane (Liao River Estuary and Yellow River Delta National Nature Reserves) from 2000 to 2015. The results showed that the landscape patterns of the important stopover sites of red-crowned crane changed obviously and the potential suitable habitat area (tidal flats and marshland) for the red-crowned crane decreased by 183.3 km2, while the area of human activities (including aquaculture waterbodies, farmland and artificial facilities) increased by 140.3 km2. Landscape fragmentation intensified, which could has negative impacts on the survival of the red-crowned crane during migration. A comparative study confirmed that the reduction in marshlands and increasing landscape fragmentation caused by human activities were the main threats in the Liao River Estuary National Nature Reserve, while human activities and natural factors (such as channel flow, rainfall, and sediment discharge) were the jointly driving factors for the reduction in suitable habitats for red-crowned cranes in the Yellow River Delta National Nature Reserve. We suggest there are some loopholes in the management of the two nature reserves, which need to be strengthened urgently in China.

Geochemical composition of sediments in the Liao River Estuary and implications for provenance and weathering

Liao River Estuary in Northeast China is one of the most important seven estuaries in China. Grain size, clay minerals, major and trace elements and rare earth element (REE) compositions were employed to evaluate the chemical weathering and climate of provenance area, and source-rock composition, and to further infer the provenance and tectonic setting of the Liao River Estuary sediments. Except for the SiO2, K2O and Na2O contents, the contents of all the major element oxides in the sediments were positively correlated with the Al2O3 contents, suggesting that they were associated with clay minerals/micaceous in the sediments. The chemical index of alteration (CIA) ranged between 56 and 64 with an average of 61 in the sediment samples reflecting low to intermediate weathering intensity of source area. The ratios of smectite/kaolinite, smectite/(illite+ chlorite) and Rb/Sr were higher during 1963–2003, indicating that the weathering was enhanced and the regional climate was relatively warm and humid. The geochemical indicators suggested that granite was the most likely source rock for the sediment samples. The La–Th–Sc, Th–Co–Zr/10 and Th–Sc–Zr/10 diagrams suggested that the provenance of the sediments was evolved from continental island arc setting. Moreover, the source rock characteristics and tectonic setting were consistent with those in the eastern of Inner Mongolia Autonomous Region. It was concluded that the source area was mainly located in the east of the Inner Mongolia Autonomous Region.

The impacts of runoff decrease and shoreline change on the salinity distribution in the wetlands of Liao River estuary, China

Abstract. The wetland of Liao River estuary (LRE) in northeastern China is one of the best-preserved wetlands across the globe. However, it is extremely vulnerable to hydrological changes as well as other disturbances, particularly upstream river discharges and the reclamation from anthropogenic activities. In this study, a 3D hydrodynamic model was used to reproduce the flow patterns of the LRE and to explore the variation in salinity under different scenarios. Furthermore, the impact of river discharge and shoreline changes on the salinity distribution in the LRE was quantitatively analyzed and discussed through several simulation experiments. The model reasonably reconstructed the spatiotemporal variability and distribution of salinity in the Liao River estuary and the wetlands across intertidal areas. Increases in runoff were demonstrated to significantly decrease the mean salinity values of the estuary, with changes in salinity negatively correlated to the longitudinal distance from the estuary mouth. Moreover, the shoreline change caused by the construction of Panjin Port was observed to have an obvious influence on the salinity distribution of the LRE, particularly in the lower reaches of the Pink Beach wetland. Comparisons of the Liao River estuary residual flow fields under different shorelines revealed that the establishment of the port resulted in the diffusion of the runoff from the Daliao River due to the obstruction of the port body, which enhanced the tidal mixing effect and consequently weakened the dilution effect of freshwater entering the Pink Beach wetland. Overall, the current study should be helpful for offering a greater understanding of Suaeda heteroptera vegetation degradation in the LRE, China, and also provides a new perspective in investigating the degradation mechanism in other estuarine wetlands.

Evaluation of Liao River estuary with cumulative and sudden risk assessment methods

In order to strengthen the management of water environment, cumulative and sudden risks were integrated into risk assessment of water environment. Analytic hierarchy process (AHP) was used to empower the index system. The cumulative and sudden risks of water environment were divided into five levels. The zoning matrix of risk level was applied to evaluate Liao River estuary area. The evaluation results were basically consistent with the field survey results. Although the cumulative risk of Liaoning province in 2011-2017 showed a downward trend, it is still in a high-risk state. The investment in water treatment, the number of water treatment equipment and water quality were the major factors that affect the cumulative risk, and the critical enterprises around the Liao River estuary are the main factors that affect the sudden risk. The above indicators were controlled can reduce the water environment risk.