Yangtze Research Articles

Synergizing Convergent Cross-Mapping and machine learning for reliable daily forecasting of riverine chlorophyll-a concentration

River algal blooms pose a global ecological and environmental problem, resulting in serious consequences for watershed ecosystems and human health. However, current research has yet to fully identify factors influencing river algal blooms or accurately predict chlorophyll-a concentration, a key indicator, at various lead-times using high-frequency data. Here, we employed Empirical Dynamic Modeling (EDM) and machine learning techniques to forecast daily chlorophyll-a concentration in the Han River of China. The Convergent Cross-Mapping (CCM) analysis revealed the causal relationships between chlorophyll-a concentration and eight variables: pH, total nitrogen, water level in the Han River, water level in the Yangtze River, water temperature, permanganate index, sunlight duration and total phosphorus in the Han River. Subsequent multivariate EDM models with three lead-times (i.e., 1-day, 5-day, and 10-day) only showed acceptable performance in model training (R2 = 0.19–0.73, MAE = 2.76–9.17 μg/L), while exhibited poor predictive performance in model testing (R2 = − 0.50–0, MAE = 9.64–13.09 μg/L). However, Gradient Boosting Machine (GBM) and Random Forest (RF) models with three lead-times exhibited robust performance in both model training (R2 ≥ 0.8, MAE < 4 μg/L) and testing (R2 > 0.6, MAE < 6 μg/L), demonstrating that machine learning models were more suitable than multivariate EDM models for reliably predicting algal blooms. Our study contributes valuable tools for predicting daily chlorophyll-a concentration. The methods presented herein hold broad applicability and offer insights into predicting the entire process of river algal blooms based on daily monitoring data.

From Imbalance to Synergy: The Coupling Coordination of Digital Inclusive Finance and Urban Ecological Resilience in the Yangtze River Economic Belt

In the context of rapid urbanization and digitalization, scientifically assessing the spatio-temporal interaction between digital inclusive finance (DIF) and urban ecological resilience (UER) is crucial for promoting the coordinated development of the regional ecology and economy. This study investigates the spatiotemporal evolution of the coupled coordination degree (CCD), the decoupling phenomenon, and its hindering factors in the Yangtze River Economic Belt (YREB) by utilizing the kernel density analysis, standard deviation ellipse, decoupling model, and obstacle degree analysis. Through systematic analyses, this paper aims to elucidate the development disparities among regions within the YREB, identify problematic areas, and propose targeted improvement measures. The results show that (1) The CCD between DIF and UER in the YREB has increased annually from 2011 to 2020. However, there are persistent imbalances, with an overall low level of coordination and uneven spatial development, and a trend of “higher coordination in the east and lower coordination in the west”. (2) The overall CCD of the YREB has reached at least the primary coordination level, with the coupling enhancement speed ranked as “downstream &gt; midstream &gt; upstream”, and regional differences decreasing. (3) The decoupling analysis reveals a predominant decoupling trend between DIF and UER, indicating that the digitization of financial services has not concurrently increased ecological pressures. (4) The obstacle degree analysis identifies resilience and digitalization as major barriers hindering CCD. This study provides a scientific basis and analytical framework for understanding the current spatiotemporal interaction between DIF and UER in the YREB, offering an important reference for formulating more effective policies.

Microphysical characteristics of torrential predecessor rain events over the Yangtze River Delta Area and the related tropical cyclones

The precipitation structures and microphysical characteristics of predecessor rain events (PREs) over the Yangtze River Delta area and related tropical cyclones (TCs) from 2014 to 2019 were investigated using Dual-frequency Precipitation radar data from Global Precipitation Measurement (GPM) for drop size distributions (DSDs). Results showed that the total mean rain rate of PREs was larger than that of TCs, primarily due to higher convective and stratiform rain rates, with enhanced fractional coverage of convective rain in PREs. Examination of microphysical characteristics revealed that a greater quantity of small-sized droplets and a smaller quantity of medium- as well as large-sized droplets contributed towards PREs in comparison with TCs. The conclusion still holds when partitioning DSDs based on different precipitation rate categories. Further investigation of DSDs using gamma functions illustrated that precipitation in PREs had lower average mass-weighted diameters (Dm) and enhanced normalized number concentration (Nw) compared with TCs; partitioning precipitation into convective and stratiform components illustrated a larger Dm and lower Nw in TCs than PREs. The analysis of microphysical and thermodynamical processes using the reanalysis data indicates that relatively intense convective activity with drier conditions may be favorable to enhancing raindrop growth through collision-coalescence processes, as a result of larger Dm in TCs than PREs. The empirical relations (Z–R algorithms) applied in different rain regimes (stratiform, convective, and total PREs) revealed significant diversities, relying on weather conditions and geographical locations. Plain language summaryThe Yangtze River Delta area is an important economic belt in China. Under climate change, observed frequent occurrences of weather extremes of heavy rainfall and tropical cyclones (TCs) exert adverse effects on economic development in this region. Thus, a deep understanding of the mechanism of TCs torrential rainfall in the Yangtze River Delta area is urgently necessary. In this study, we investigated the precipitation patterns and microphysical characteristics of predecessor rain events (PREs) in the Yangtze River Delta region, and their association with TCs in the South China Sea-Western North Pacific Ocean (SCS-WNPO) area from 2014 to 2019. We found that PREs had a higher total mean precipitation rate than TCs. Further examination using gamma functions demonstrated that PREs exhibited lower average mass-weighted diameters (Dm) and higher normalized intercept parameters (Nw) than TCs. This pattern persisted when distinguishing between convective and stratiform precipitation components. We believe that our study makes a significant contribution to the literature because these results provide valuable insights into the distinct precipitation characteristics of PREs and TCs in the study region and contribute to a better understanding of tropical cyclone-related rainfall patterns, and act as a scientific basis for disaster mitigation.

How Top-Down Water Regulation Affects the Financial Performance of Enterprises: The River Chief System in China as an Example

As a top-down type of water regulation, the River Chief System (RCS) in China has effectively enhanced urban water quality. Simultaneously, environmental control significantly impacts the financial performance of enterprises. In recent years, the tension between environmental protection and economic development has escalated, underscoring the undeniable economic ramifications of stringent water regulations. Enterprises are the fundamental agents of economic activities and environmental impact, thus becoming the primary targets of water environment regulatory policies. This study adopts the differences-in-differences (DID) method and uses a sample of listed enterprises in the Yangtze River Economic Belt region from 2010 to 2021 to study the impact of the RCS on the financial performance of enterprises. The results show that the RCS harms the financial performance of enterprises. This impact primarily manifests through increased environmental protection investments. Conversely, the RCS does not have a positive influence on enterprises’ technological innovation. This indicates the challenge of stringent top-down environmental regulations in stimulating short-term technological advancements and enhancing enterprise performance. Moreover, the adverse effects of the RCS on financial performance are notably pronounced for non-state-owned enterprises and those located in the upper Yangtze River Economic Belt. This suggests that private enterprises and those in less-developed regions exhibit lower resilience to top-down environmental regulations.

Differentiated strategies for synergistic mitigation of ammonia and methane emissions from agricultural cropping systems in China

Ammonia (NH3) and methane (CH4) emissions from agricultural cropping systems in China have substantially impacted environmental quality and climate change, which become the key sector for synergizing pollution control and carbon reduction. However, the experiences of synergistic NH3 and CH4 emission governance at fine scales in this sector are still lacking. Here, we estimated NH3 and CH4 emissions from agricultural cropping systems in China in 2019 and identified regional characteristics of these emissions using advanced spatial analysis techniques. Subsequently, we developed an innovative synergistic mitigation zoning identification method to establish targeted and spatially differentiated reduction measures, addressing a critical gap in mitigation strategies for agricultural cropping systems in China. The results showed that NH3 and CH4 emissions from the three most important crops were 3.04 Tg N yr-1 and 8.13 Tg C yr-1, respectively. NH3 and CH4 emissions exhibited the highest values in Eastern China, but the highest emission densities of NH3 (49.8 kg N ha-1 yr-1) and CH4 (394 kg C ha-1 yr-1) were observed in Northwest and South China, respectively. Further, bivariate local indicators of spatial association (LISA) maps revealed that the middle and lower reaches of the Yangtze River were hotspots for simultaneous high emissions of NH3 and CH4. Finally, based on the identified eight categories of zones, region-specific mitigation measures were proposed, including improved fertilization practices, irrigation methods, and straw management. These targeted, spatially differentiated mitigation strategies provide a reference framework and feasible approach for synergistic pollution control and carbon reduction in China's agricultural sector.

Numerical Simulation of Saltwater Intrusion in the Yangtze River Estuary Based on a Finite Volume Coastal Ocean Model

Numerical Simulation of Saltwater Intrusion in the Yangtze River Estuary Based on a Finite Volume Coastal Ocean Model

Risk assessment of Arsenic in surface water of China water systems based on a time-dependent species sensitivity distribution (SSD) method

Arsenic (As) is a naturally occurring metalloid element widespread in the environment. Assessing the ecological risk of As in surface water, especially the acute risk caused by emergent pollution incidents, is of great significance. However, acute toxicity data including median lethal concentration (LC50) and median effective concentration (EC50) of As derived by toxicology experiment may vary according to the exposure time, which is referred as time dependence effect. Time dependence not only affects toxicity data but also influences the characterization of acute risk in the ecosystem. However, previous research on the time dependence effect of As, especially the quantitative influence on the risk assessment is still limited. In this research, acute toxicity data of As(III) and As(V) was collected. Time dependence of toxicology data of inorganic As was studied. Time-dependent species sensitivity distributions of freshwater species were established. The hazardous concentration for 5% of species (HC5) values in different exposure time were further derived. Finally, the dynamic ecological risk of As in major Chinese water basins was evaluated. The results suggested that the toxicity data of inorganic As had a significant linear relationship (p < 0.01) with time. The HC5 values of As (III) and As (V) at an exposure time of four days were reduced by 15.5% and 77.5%, respectively, as compared to the HC5 value of one day. According to the ecological risk characterized by the probability density overlapping area method, the ecological risk of As(III) and As(V) increases with the exposure duration. The Yangtze River had the highest risk, with risk values ranging from 19.9% to 22.6%. According to the results, the time dependence of toxicity data should be fully considered in the formulation of water quality criteria or ecological risk assessment so as to provide better protection for the water ecosystem security.

Experimental study on the thixotropic strength of the marine soft clay from the Yangtze River estuary

Soft clay in the offshore area of the Yangtze River estuary has been investigated considering its basic physical properties. Forty-five unconfined compressive strength tests were conducted on the remolded marine soft clay to investigate the impacts of curing time T, water content w, plasticity index IP, and clay particle content ρc on the thixotropic static shear strength ratio As of the marine soft clay from the Yangtze River estuary. Results show that the stress–strain curves were primarily strain hardening and strain softening curve types. Unconfined compressive strength qu increased with an increase in T. All specimens with different basic physical properties were capable of thixotropic strength recovery. When T = 0–28 days, As increased rapidly, while for T &amp;gt; 28 days, As of most specimens increased slightly or tended to stabilize. The impacts of w, IP and ρc on As do not follow a consistent pattern, but there is a strong correlation between As and w/wL (wL is the liquid-limit water content). For w/wL &amp;lt; 0.75, As increased with increasing w/wL, whereas for w/wL ≥0.75, As decreased with increasing w/wL. We proposed a simple and widely applicable power function prediction model for the As of the soft clay from the Yangtze River estuary.

Coupling coordination analysis and spatiotemporal heterogeneity between urban land green use efficiency and ecosystem services in Yangtze River Economic Belt, China

Rapid urbanization has resulted in the conversion of different land types, leading to a serious disruption of the balance of ecosystems, and the contradiction between land use and ecological security becomes increasingly severe. As a key factor affecting ecosystem services (ESs), improving the urban land green use efficiency (ULGUE) can effectively mitigate the decline in the ecosystem services function. This study tried to verify the profound impact of land use on ESs by measuring the coupling coordination degree (CCD) between ULGUE and ESs from the perspective of coupling coordination. However, the traditional CCD model suffers from volatility and non-comparable confidence levels in results. For this background, this study adopted the improved CCD model to measure the association between ULGUE and ESs in the Yangtze River Economic Belt (YREB). Also, a comprehensive spatial evolution of the CCD was further explored. The main conclusions are as follows: (a) The overall level of ULGUE in YREB showed an increasing trend with the distribution of ULGUE in most cities ranging from 0.71 to 1.00, showing a higher level overall and the spatial distribution character of “small aggregation, large distribution”; (b) The ESs of YREB from 2005 to 2020 demonstrated a decreasing trend and majority of cities’ current ecological protection efforts are lagging behind the extent of ecosystem damage caused by human activities; (c) The overall average CCD of YREB was largely at basically balanced level and the average CCD change ranges from 0.38 to 0.45 between 2005 and 2020, but the overall CCD had a strong spatial correlation strength. (4) To some extent, the improved CCD model solved the problems of volatility and credibility based on the traditional CCD results, which have strong rationality and scientific validity. Identifying the coupling and coordination characteristics and mechanisms can effectively provide theoretical support for the sustainable development of watersheds.

How Do Changes in Ecosystem Services Multifunctionality Influence Human Wellbeing? Evidence From the Yangtze River Delta Urban Agglomeration in China

ABSTRACTA proclaimed goal of landscape management is to improve the multifunctionality of ecosystem services (ESs) to sustain higher levels of human wellbeing (HWB). Although the enhancement of ES multifunctionality is often considered to lead to better HWB, empirical evidence directly supporting this claim remains scarce. This study investigates the relationship between ES multifunctionality and HWB in rapidly urbanizing regions, using the Yangtze River Delta Urban Agglomeration in China as a case study. We quantified ES multifunctionality with the Gini‐Simpson Diversity Index and identified ES multifunctional types using the bundle approach. We also calculated both the HWB mean score and HWB evenness score with the improved radar chart method, examining their relationships with ES multifunctionality through Spearman correlation analysis and the Kruskal–Wallis rank‐sum test. Results showed that (1) ES multifunctionality exhibited varied relationships with HWB indicators, but overall showed significant negative associations with both HWB mean score and HWB evenness score. (2) Each HWB indicator significantly differed across the detected ES bundles, but none of the bundles exhibited the highest values of all HWB indicators. (3) HWB mean score and HWB evenness score were generally higher in the peri‐urban bundle while lower in the agriculture and forest bundles. Our findings suggest that peri‐urban landscapes can provide relatively higher and more balanced levels of HWB in urban agglomerations. This also implies that a “land‐sharing” urban development model, which balances natural and built environments, may be more beneficial for enhancing ES multifunctionality and HWB compared with a “land‐sparing” model, where natural and built areas are separated.

River Hydrological Regime Changes and Their Attribution: A Case Study in the Upper Reaches of the Yangtze River Using a Multi‐Model Approach

River Hydrological Regime Changes and Their Attribution: A Case Study in the Upper Reaches of the Yangtze River Using a Multi‐Model Approach

Study on the ecosystem service flow based on the relationship of between supply and demand in Yangtze River Economic Belt

Ecosystems supply goods and services to humans and are the basis for sustainable development of human society. The study of the supply of ecosystem services and the demand and consumption of ecosystem services by human society, and the analysis of the supply and demand characteristics and flow relationships of ecosystem service flows are of great significance for the management of regional ecosystems and the development of ecological compensation. Taking the Yangtze River Economic Belt as an example, this paper calculates the supply and demand indices of ecosystem services in 2015 and 2020, and determines the ecosystem spatial flow paths and flow volumes from the ecosystem supply area to the demand area based on various methods and models such as the minimum cumulative resistance (MCR) model and distance decay model. The results indicate that 1). In 2015 and 2020, the supply and demand of ecosystem services in the Yangtze River Economic Zone show an increasing trend numerically, and there is spatial heterogeneity in the spatial distribution. In terms of ecosystem service supply per unit area, the midstream region is higher than the upstream and downstream regions. In terms of the demand for ecosystem services per unit area, the downstream is higher than the midstream and upstream. 2). From the supply-demand balance of ecosystem services in the Yangtze River Economic Zone, the midstream region is mainly the area of surplus supply of ecosystem services, and the downstream region is mainly the area of deficit supply. From 2015 to 2020, the number of areas with balanced supply and demand of ecosystem services in the Yangtze River Economic Belt decreases and the number of areas with unbalanced supply and demand increases, which is related to the changes in the level of economic development and land use patterns. 3). The flow of ecosystem services in the Yangtze River Economic Belt shows an increasing trend, from 726.59 billion yuan in 2015 to 1,450.54 billion yuan in 2020, with Jiangxi Province being the main ecosystem service supply area and Zhejiang Province being the main ecosystem service demand area in the Yangtze River Economic Belt.

Emission inventory of IVOCs from diesel engine emissions in China based on real-world measured data

Intermediate volatility organic compounds (IVOCs), recognized as significant precursors of secondary organic aerosols, play a pivotal role in environmental pollution. This study utilized measured real-world emission factors to construct an inventory of IVOC emissions from diesel engines and to analyze their spatial distribution across China in 2022. Furthermore, the emission inventory derived from this approach was compared with that obtained through the IVOC/primary organic aerosol (POA) ratio method. The following findings were observed: (1) In 2022, the total IVOC emissions from diesel engines in China amounted to approximately 430 Gg, surpassing those emitted by gasoline engines and residential solid fuel combustion. Specifically, the IVOC emissions attributed to on-road diesel vehicles, inland vessels, agricultural machinery, and non-road construction machinery were recorded at 377, 39.3, 10.4 and 3 Gg, respectively. (2) In terms of geographical distribution in 2022, IVOC emissions from diesel engines were predominantly concentrated in Eastern, Southern and Northern China; on-road diesel vehicle emissions were primarily located within logistics hubs or regions characterized by extensive national and arterial road networks; while non-road construction and agricultural machinery emissions were largely confined to Eastern and Central China. Emissions from inland vessels exhibited a more distinct regional pattern concentrated mainly within the Yangtze River Delta, Pearl River Delta, and Bohai Rim areas. (3) A comparative analysis between the inventory established using real-world measured emission factors and that derived via IVOC/POA ratios indicated that the latter methodology may have overestimated emissions associated with inland vessels and non-road construction machinery. Moving forward, reducing IVOC emissions from diesel engines is crucial for enhancing air quality and safeguarding human health-particularly concerning heavy-duty vehicles, light-duty vehicles, and inland vessels.

Ecosystem services in the Yangtze River Basin and their trade-offs/synergies relationships in response to climate change

Abstract The Yangtze River Basin is an important ecological security barrier with significant economic status, but it is greatly affected by climate change. Therefore, we investigated the spatio-temporal evolution characteristics of annual ecosystem service (net primary production (NPP), water conservation and soil retention), their interrelationships and responses to climate change in the Yangtze River Basin from 2001 to 2020. The annual NPP, soil retention and water conservation were 511 gC m−2, 632 t and 272 mm, respectively and they all increased over 2001–2020 though this varied in both time and space. The capacities of soil retention and water conservation did not increase, and even gradually decreased for first 10 years (2001–2010), most likely due to the subsequent effects of the catastrophic flood of Yangtze River occurred in 1998. There are tradeoffs between NPP and soil retention/water conservation in the west Sichaun Province, which is different from the rest of the Yangtze River Basin where synergistic relationships dominate. Precipitation is the dominate climatic influencing factor on the ecosystem service trends found in the Yangtze River Basin. The concept of ecosystem services is being incorporated into decision-making and management, this study is critical to guide regional effective resource utilization, ecosystem management decisions and feasible policies.

Using hydrological modeling and satellite observations to elucidate subsurface and surface hydrological responses to the extreme drought

Climate change and anthropogenic activities have intensified extreme weather events globally. In the summer of 2022, the Yangtze River Basin (YRB) in China experienced an extreme drought, significantly impacting the ecosystems and society. However, the specific effects of this extreme drought on surface and subsurface hydrological dynamics remain unclear. Here we employed satellite-observed terrestrial water storage anomaly (TWSA) and a modified hydrological model with consideration of reservoir operation, human water consumption, and water diversion engineering to quantify how subsurface and surface water in YRB responded to such an extreme drought in 2022. Validation against a series of observations shows that the modified model has good performance in reproducing daily streamflow, reservoir water storage, lake water storage, and snow water equivalent. It achieved more precise GRACE TWSA estimates in the YRB with significant human intervention, and therefore it can fairly accurately quantify both surface and subsurface hydrological responses to the 2022 extreme drought. Compared to the same months (July-December) in 2015–2021, the drought in 2022 resulted in a decrease in precipitation and discharge of 373 km3 (36 %) and 324 km3 (50 %), respectively, while an increase in evapotranspiration of 156 km3 (29 %) in the YRB. In general, the surface water storage (SWS) is relatively low from July 2022, followed by subsurface water storage (SSWS) from August 2022, indicating an approximately one-month lag from the former to the latter. During the latter half year of 2022, the SWS and SSWS reduced by 48 km3 and 83 km3, respectively, suggesting the changes in the latter dominated the TWS variations. This study sheds light on the responses of surface and subsurface hydrology to extreme droughts, and the hydrological modeling framework with consideration of human activities proposed here holds applicability beyond the YRB.

Fingerprint of Plio–Quaternary detrital zircon geochronology: Implications for sediment provenances and geomorphological evolution of the Yangtze Delta

The Yangtze (Changjiang River) Delta serves as a prominent depocenter for siliciclastic sediments from the Tibetan Plateau and Yangtze Craton, providing essential data on sediment source-to-sink dynamics and geomorphological evolution of large river drainage systems. This study presents the detrital zircon geochronology of Plio–Pleistocene sediments in the Yangtze Delta, alongside the data from modern river sediments, to elucidate provenance evolution since the Pliocene. The zircon geochronology reveals a considerable shift in sediment provenance during the Pliocene–Pleistocene transition. The Pliocene sediments exhibit a straightforward and predominant zircon age spectrum characterized by a typical peak age of 100–200 Ma. This spectrum markedly differs from the modern upper–middle Yangtze River sediments but closely resembles those of local rivers in the lower Yangtze River region. This demonstrates that the Pliocene sediments originated from local mountainous rivers, indicating the paleo-Yangtze River channelization prior to the Quaternary. In contrast, the zircon age spectra of Pleistocene sediments in the present-day delta reveal several dominant age groups ranging from 11.9 ± 1 to 3643 ± 30 Ma, similar to those found in present-day upper–middle Yangtze River sediments. This implies that the Pleistocene sediments were mainly derived from the upper–middle Yangtze River, showing a diversity of source rocks with varying geological ages and origins. The presence of the upper Yangtze River provenance signal, characterized by Cenozoic (<65 Ma) zircons, in early Pleistocene strata (ca. 1.6 Ma) of the delta suggests that the paleo-Yangtze River transported Tibet-sourced sediments into the modern delta area no later than that time. These findings indicate the geomorphological evolution of the Yangtze River Delta from an intermontane basin in the Pliocene to an alluvial–fluvial plain during the Quaternary. This geomorphological and geographic evolution, along with changes in sediment source, directly reflect extensive tectonic subsidence in eastern China since the late Cenozoic.

Integrating heterogeneous information for modeling non-stationarity of extreme precipitation in the Yangtze River Basin

Extreme precipitation exhibits non-stationary characteristics due to climate change and land use/cover change in recent years. In the literature, probability distributions with varying parameters associated with covariates have been applied to describe the non-stationarity of extreme precipitation. However, there is no consensus on the optimal distributions and the number and type of covariates for constructing non-stationary models. This study comprehensively investigates and determines the optimal distribution models, the type of covariates, and the number of covariates to best characterize the non-stationarity of extreme precipitation, using the Yangtze River Basin as the study area. The time series of four indices representing extreme precipitation of different durations and intensities are fitted by stationary and non-stationary Generalized Additive Models for Location, Scale, and Shape. The models are constructed using seven distributions and four types (time, global climate, local climate, and land cover) of covariates. Each model incorporates one to three covariates simultaneously. The results show that the most preferred distribution is the Generalized Extreme Value distribution for very wet-day precipitation, while the Log-Normal distribution is more suitable for other extreme precipitation indices. For the type of covariates, when using a single covariate, the proportion of stations using a global climate covariate as the best covariate (22.3 %–33.2 % of 193 stations) is close to that using a local climate covariate as the best covariate (22.3 %–27.5 %). The proportion of stations using land cover as the best covariate is much lower (7.3 %–10.9 %), while that using time as the best covariate is the lowest (1.6 %–4.1 %). When using multiple covariates, the models with both global and local climate covariates are mostly selected (8.3 % to 17.6 %) for all extreme precipitation indices. For the number of covariates, one or two covariates are enough to describe the non-stationary behaviors of all extreme precipitation indices. This study emphasizes the necessity to use non-stationary models for extreme precipitation frequency analysis with careful consideration and selection of distributions and covariates.

Sediment source-to-sink patterns along the Southeast China coast during the late quaternary: New insights from sediment geochemistry and OSL ages in the Ningde Bay

The geomorphology and environmental conditions of the southeast China coast are significantly influenced by sediment discharge from the Yangtze River, a major river located to the north. Nonetheless, the extent to which the Yangtze River affects sediment transport processes from source to sink along the southeast coast remains unclear. Our recent findings in coastal/marine deposits from the late Quaternary period (MIS5e, MIS3, and MIS1) in Ningde Bay offer new perspectives on this issue. Provenance discrimination of the late Quaternary boreholes was carried out using sediment geochemical analysis and OSL dating of fine- and medium-grained quartz. The results indicate varying provenances during sea-level fluctuation, with distal Yangtze River origins during MIS5e, MIS3, and MIS1, and a local source during MIS4. The findings also suggest that the southward transport of Yangtze sediments along the southeast China coast has occurred since MIS5e. However, OSL ages of the fine-grained quartz in the MIS3 deposit range from approximately 90 to 140 kyr, notably older than those of medium-grained quartz (40–80 kyr). This remarkable age discrepancy indicates that Yangtze-derived sediments previously deposited on the shelf of the East China Sea during MIS5 were reworked and transported southward in MIS3. This phenomenon can be elucidated by the insufficient supply of Yangtze sediments during MIS3, which could be linked to the weakened East Asian monsoon. This new source-to-sink pattern for the southeast China coast is characterized by a compensating mechanism of inner shelf old sediment in response to the inadequate supply of Yangtze sediments. This study contributes to a better understanding of the significant impacts of reduced Yangtze sediment input on its distal sedimentary systems over time.

Genome-wide association study and candidate gene identification for the cold tolerance at the seedling stage of rapeseed (Brassica napus L.)

Rapeseed (Brassica napus L.) is an important overwintering oilseed crop and suffers from severe cold stress during the seedling stage due to the increasingly delayed sowing in the Yangtze River Basin. However, the genetic basis underlying cold tolerance in rapeseed seedlings is not well understood. In this study, we observed the cold tolerance of 217 rapeseed accessions in the field and found a significant negative correlation between cold tolerance grades and malondialdehyde (MDA) contents. A genome-wide association study (GWAS) of cold tolerance grades Identified four significant loci in the genomic region of one MYB transcription factor BnaA8.MYB60. Furthermore, field accessions with BnaA8.MYB60Hap1 exhibited significantly higher cold tolerance and lower expression of BnaA8.MYB60 compared to the majority of accessions with BnaA8.MYB60Hap2. These results suggested that variations in the genomic sequences of BnaA8.MYB60 caused the divergence of gene expression levels and functions on cold tolerance in rapeseed seedlings. This study could provide the theoretical guidance for the breeding of cold-tolerant rapeseed varieties.

The mechanism of urban agglomeration causing the enhancement of regional extreme heat and drought events

Urban agglomerations formed by rapid urbanization have been found to be important ways through which human activities influence regional weather and climate. However, the role of urban agglomerations in the formation of extreme heat and drought events remains unclear. We perform numerical simulations using RegCM 5.0 on an August 2022 extreme heat event in the Yangtze River Basin in China. The results show that urban agglomerations lead to significantly increased temperature in both urban (0.6 °C increase) and non-urban (0.2 °C increase) areas. The land feedback formed by urban agglomerations significantly increases the surface sensible heat, turbulence activity, urban upward movement, and urban heat island effect. As a result, the sinking airflow is enhanced, the surface wind is increased, and a dome-shaped wind field anomaly is formed around the urban agglomerations. This widens the geographic scope of the heat event and heightens its intensity.