Delta Area Research Articles

Understanding land subsidence in the Pearl River Delta region of China based on InSAR observations

Land subsidence occurs in river delta areas. A comprehensive understanding of the factors contributing to land subsidence is crucial for effective geohazard mitigation and land planning. This study investigates the distribution characteristics and spatiotemporal evolution pattern of the land subsidence in the Pearl River Delta based on the InSAR-derived ground deformation data spanning 2016 to 2021; and, the effects of the influencing factors, including the Quaternary sediment thickness, land use classification, land reclamation, and subway construction and operation, on the subsidence are analyzed. The results unveil the presence of four major subsidence zones and several minor coastal subsidence bowls in the research area, with a total area of about 1100 km, all of which exhibit prolonged and intense subsidence. In the remaining regions, land subsidence predominantly exhibits weak and short-term occurrences. The subsidence in the study area follows a distinct linear evolutionary pattern with a slight rebound, potentially linked to the rise of groundwater levels. Regions with Quaternary sediment thickness surpassing 20 m, engaging in aquaculture or agricultural activities, and featuring reclaimed land are predisposed to prolonged and intense ground subsidence. In addition, the construction and operation of subway lines may induce ground subsidence, especially in geologically vulnerable areas. This study provides valuable insights into land subsidence research in delta regions.

Advancing Black Men’s Type 2 Diabetes Healthcare Through Addressing Gender-centered Social Norms, Cognitive Scripts, and Manhood: An Integrated Public Health Approach for Reducing T2D Disparities

ABSTRACT In the United States, the burden of type 2 diabetes (T2D) health complications and outcomes is higher in Black men, and the diabetes disparities are escalating. Previous evidence-based research underscored the need to explore gender-specific experiences of chronic illness in social-cultural, historical, and clinical contexts. Our community-engaged qualitative study focused on learning from the live experiences of Black men (n = 15) in the Arkansas Delta area. Applying a narrative approach, we explored and learned from the participants about their perception of the consequences of T2D on manhood and the usefulness of T2D management instructions. Findings indicate that an integrated public health approach contextualizes social-cultural norms, cognitive scripts, and gender-centered expressions of manhood, a promising direction in T2D healthcare; social support is essential for emotional and physical help in continued T2D management; and connecting with Black men and their insights are vital to develop relevant and appropriate guidelines for T2D management care.

Effects of upstream and downstream boundary conditions on lacustrine shallow-water delta morphologies: A numerical modeling approach

Lacustrine shallow-water deltas exhibit highly variable morphologies, owing to their high sensitivity to changes in the upstream and downstream boundary conditions, where a small change significantly alters their morphology. In this study, we present the results from a numerical model (DELFT3D) used to explore the mechanism of distributary network amalgamation and delta evolution under various boundary conditions. We established a reference case to model the delta building-out process considering the basin water depth difference (shallow and deep). Geological and hydrodynamic models were established by varying the water level under a steady river discharge and sediment supply. Despite similar initial conditions, each modeled delta exhibits a unique morphological evolution, progressing through distinct stages: (i) formation of unstable, narrow channels with quasi-radial shapes; (ii) channel development, shaping the delta based on controlling factors; (iii) reduction of deltaic activity and increased channel avulsion due to delta submergence, and; (iv) new channels emerging, paving the way for reshaping and migration towards new paths, resulting in fewer bifurcations and straighter channels. Quantitative relationships characterizing delta morphology and distributary channels were established, and the following results were noted: (i) a positive correlation between active and abandoned channels, distributary channel network opening angle, and delta area with discharge and sediment grain size, and negative correlation with basin depth and falling water level; (ii) a positive correlation of lobe elongation with basin depth and discharge, and a negative correlation with sediment grain size; and (iii) roughness and length-to-width ratio emerging as key predictors of delta shape. By applying the model predictions to real-world scenarios, including modern deltas (Sile and Chiemsee) and ancient systems (Bohai Bay Basin), this study can provide valuable insights into the dynamics of lacustrine deltaic systems and their responses to changing boundary conditions. This highlights the importance of understanding deltaic systems for both theoretical research and practical applications.

Unleashing Economic Potential: Enhancing Cassava Production Efficiency in Nigeria

Purpose: This study is aimed at determining the economic efficiency of Manihot esculenta Crantz (Cassava) production in Nigeria’s Delta State. The study offers a detailed analysis of how socio-economic characteristics influence production output across both early and late farming seasons. Design/ Methodology/ Approach: This study employed a multi-stage random sampling approach in selecting a diverse cohort of 500 cassava farmers engaged in both early and late-season cultivation. Through rigorous personal interviews, primary data was gathered that was both comprehensive and insightful. Advanced parametric statistics and the Cobb-Douglas stochastic frontier function were used for the analysis. Findings: The mean economic efficiency scores were determined to be 0.63 for early-season farms, 0.78 for late-season farms, and 0.76 when considering all farms collectively. The output elasticities of material inputs, labour, and land were found to be 0.42, 0.61, and 0.05, respectively for all farms. For early-season farms, these values were 0.36, 0.68, and 0.04, whereas, for late-season farms, they were 0.31, 0.7, and 0.03. Research Limitation/Implications: This work concentrated on Cassava production efficiency within and around Nigeria’s Delta area. Practical Implication: Understanding the socio-economic factors that influence production during different seasons can help in designing strategies that maximize output in both early and late farming seasons. Social Implication: This study would help agricultural development economists and policy-makers in addressing the economic problems of Cassava farmers both present and future generations. Originality/Value: By examining both early and late farming seasons, the study provides a comprehensive understanding of how socio-economic factors vary across different agricultural cycles. This dual-season approach is relatively rare and offers more detailed insights into the dynamics of cassava production throughout the year.

Molecular and Morphological Assessment of the Impact of Gas Flares on the Fungal Abundance and Diversity in soils of Niger Delta Area, Nigeria

Fungal abundance and diversity in soils of three communities flow stations (ID, IR and OB) owned by an unnamed oil exploration firm operating in the Niger Delta area for about five decades were determined using nucleic acid analytical methods. Top soil (0-15 cm) samples were collected from mini pits using sterile bottles at 50, 100 and 150 meters from the flare barrier of each community flow station and soil samples from the control was taken at 2.5 kilometers during the dry and wet seasons. The fungal properties were determined first using the cultural method of serial dilution method which revealed the presence of the following fungi; Aspergillus sp, and penicillium chrysogenum at 50 m away from flare in all the three flow stations during the dry seasons and in the wet season Aspergillus sp, penicillium chrysogenum, Mucor sp., yeast cells, A. niger, and Rhizopus sp. At 100 m away from flare, Mucor sp, A. niger and rhizopus were isolated in all three-flow station in the dry season and in the wet season, Yeast cells, A. niger, Aspegillus sp. and Rhizopus were isolated. P. chrysogenum, Aspergillus sp. and yeast cells were isolated at 150 m away from flare in the dry season and in the same distance, yeast cells, A. niger aggregate, A. niger and P. chrysogenum were isolated. At the control site, during the dry season, A. niger, P. chrysogenum, Aspergillus sp., Rhizopus sp. and Botryodiplodia threobome were isolated in the dry and A. niger, P. chrysogenum and yeast in the wet season. Fungal DNA was extracted using Norgen fungal genomic DNA extraction kits for the molecular analysis to establish the true characteristics and species identity of the isolates earlier identified with cultural methods. This revealed the presence of the following fungi upon sequence blast on NCBI database; Aspergillus fumigatus (Aspergillus fumigatus brown 2 (abr2) gene, complete cds strain), Aspergillus fumigatus (Aspergillus fumigates strain IHM 15988 pigment biosynthesis protein), Fusarium phyllophilum , Fusarium graminearum, Aspergillus oryzae (a strain of Aspergillus niger) Aspergillus oryzae (niger). Findings from this work have shown that molecular technique gave the exact identity of fungal species isolated from study area. All six (6) molecularly identified fungi were isolated from the three-study flow station and in both seasons. The Aspergillus group was dominant as a result of their ability to adapt to the flare environment

Sedimentary record of water-sediment regulation and channel shifts in the Yellow River (Huanghe) Delta

Delta are vital habitats for people and biotic communities. Many of the world's large river deltas are shrinking because of relative sea level rise and intensifying human interventions in the basin. Among these, the Yellow River Delta (hereafter YRD) has been enormously impacted by frequent channel avulsions and a Water-Sediment Regulation Scheme (WSRS) through upstream reservoirs since 2002. However, it remains undisclosed how the YRD responses to these human interventions. Here, modern sedimentation and inter-annual to multi-decadal timescales evolution of the YRD were studied using a dataset including 10 sediment cores collected in the subaqueous delta during the 2014 WSRS, satellite images, hydrographic and bathymetric data from 1976 to 2014. Our results show that the sedimentation of the delta can be divided into three stages: 1976–1995, 1996–2001, and 2002–2014. The area of subaerial delta generally increased from 3884 km2 to 4441 km2 during the whole 1976–2014 period except for a net land loss during 1996–2000. >70% of the delta coastline became artificial after 2000. Bathymetric data reveals that the subaqueous delta was seriously eroded after 1996 due to a shortage of sediment supply, with an estimated 2.3 × 108 t/yr and 1.1 × 108 t/yr of sediment respectively transported to the delta's adjacent sea during 1996–2001 and 2002–2014. The deltaic sediment became coarser due to the impact of the WSRS. Radionuclide 7Be uncovers a rapid sediment accumulation of ∼12 cm at the active delta front during the 2014 WSRS. The evolution of the YRD has become complex under the influence of natural and anthropogenic factors. The YRD thus provides an exemplar shift from natural to human-dominated delta. These results are important for the delta management decision making.

Using Google Earth Engine to Assess the Current State of Thermokarst Terrain on Arga Island (the Lena Delta)

The mapping of thermokarst landscapes and the assessment of their conditions are becoming increasingly important in light of a rising global temperature. Land cover maps provide a basis for quantifying changes in landscapes and identifying areas that are vulnerable to permafrost degradation. The study is devoted to assessing the current state of thermokarst terrain on Arga Island. We applied a random forests algorithm using the capabilities of the Google Earth Engine cloud platform for the supervised classification of the composite image. The analyzed composite consists of a Sentinel-2 image and a set of calculated indices. The study found that thermokarst-affected terrains occupy 35% of the total area, and stable terrains cover 29% at the time of image acquisition. The classifier has also mapped water bodies, slopes, and blowouts. The accuracy assessment revealed that the overall accuracy for all the different land cover classes was 98.34%. A set of other accuracy metrics also demonstrated a high level of performance. This study presents significant findings for assessing landscape changes in a region with unique environmental features. It also provides a potential basis for future interdisciplinary research and for predicting future thermokarst landscape changes in the Lena Delta area.

Ownership and use of insecticide-treated nets in Myanmar: insights from a nationally representative demographic and health survey

BackgroundMalaria poses a substantial public health threat in Myanmar, indicating the need for rigorous efforts to achieve elimination of the disease nationwide by 2030. The use of insecticide-treated nets (ITNs) forms part of a pivotal strategy for preventing transmission. This study explored the ownership and use of ITNs in Myanmar and identified factors associated with non-use of ITNs.MethodsHousehold datasets from the 2015–2016 Myanmar Demographic and Health Survey were utilised, which encompassed all household members except children under the age of five. Descriptive statistics and inferential tests, including simple and multiple logistics regression models and Pearson correlations, were employed for analysis. All analyses, taking the two-stage stratified cluster sampling design into account, used weighting factors and the “svyset” command in STATA. The ownership and use of bed nets were also visualised in QGIS maps.ResultsAmong the 46,507 participants, 22.3% (95% CI 20.0%, 24.5%) had access to ITNs, with only 15.3% (95% CI 13.7, 17.1%) sleeping under an ITN the night before the survey. Factors associated with the non-use of ITNs included age category (15–34 years—aOR: 1.17, 95% CI 1.01, 1.30; 50+ years—aOR: 1.19, 95% CI 1.06, 1.33), location (delta or lowland—aOR: 5.39, 95% CI 3.94, 7.38; hills—aOR: 1.80, 95% CI 1.20, 2.71; plains—aOR: 3.89, 95% CI 2.51, 6.03), urban residency (aOR: 1.63, 95% CI 1.22, 2.17), and wealth quintile (third—aOR: 1.38, 95% CI 1.08, 1.75; fourth—aOR: 1.65, 95% CI 1.23, 2.23; fifth—aOR: 1.47, 95% CI 1.02, 2.13). A coherent distribution of the ownership and use of ITNs was seen across all states/regions, and a strong correlation existed between the ownership and use of ITNs (r: 0.9795, 95% CI 0.9377, 0.9933, alpha < 0.001).ConclusionsThis study identified relatively low percentages of ITN ownership and use, indicating the need to increase the distribution of ITNs to achieve the target of at least one ITN per every two people. Strengthening the use of ITNs requires targeted health promotion interventions, especially among relatively affluent individuals residing in delta or lowland areas, hills, and plains.

Triple burden of malnutrition among Vietnamese 0·5-11-year-old children in 2020-2021: results of SEANUTS II Vietnam.

SEANUTS II Vietnam aims to obtain an in-depth understanding of the nutritional status and nutrient intake of children between 0.5-11.9 years old. Cross-sectional survey. A multistage cluster systematic random sampling method was implemented in different regions in Vietnam: North Mountainous, Central Highlands, Red River Delta, North Central and Coastal Area, Southeast and Mekong River Delta. 4001 children between 6 months and 11.9 years of age. Prevalence of stunting and underweight was higher in rural than in urban children, whereas overweight and obese rates were higher in urban areas. 12.0% of the children had anemia and especially children 0.5-1-year-old were affected (38.6%). Low serum retinol was found in 6.2% of children ≥ 4 years old. Prevalence of vitamin D insufficiency was 31.1% while 60.8% had low serum zinc. For nutrient intake, overall, 80.1% of the children did not meet the estimated energy requirements. For calcium intake, ∼60% of the younger children did not meet the RNI while it was 92.6% in children >7 years old. For vitamin D intake, 95.0% of the children did not meet RNI. SEANUTS II Vietnam indicated that overnutrition was more prevalent than undernutrition in urban areas, while undernutrition was found more in rural areas. The high prevalence of low serum zinc, vitamin D insufficiency and the inadequate intakes of calcium and vitamin D are of concern. Nutrition strategies for Vietnamese children should consider three sides of malnutrition and focus on approaches for the prevention malnutrition.

The Nexus of Regional Integration and Household Welfare: A Case Study of the Yangtze Delta Area

Public policies of regional integration have been widely implemented recently in multiple countries as a significant approach to improving regional economic cooperation and reducing economic inequalities. In China, improving household welfare and narrowing welfare gaps become another major purpose of regional integration. Nevertheless, little attention has been paid to household-level impacts of regional integration on improving welfare. This study provides empirical analysis on impacts of regional integration on household welfare by using the case of the Yangtze Delta area from 2010 to 2020. We find that overall impacts of regional integration on improving household welfare and reducing household welfare inequality are significantly positive, and such impacts reveal spatial heterogeneity. Public transport infrastructural integration and city-level migration are two major mechanisms through which such impacts can be amplified. Results remain feasible after a series of robustness tests. We believe that integration should be further implemented to eliminate poverty and boost social welfare in both developed and developing regions in China, and cross-city and interprovincial trade needs to be promoted as an important means of regional integration.

Evaluating the Nephroprotective and Hepato-protective Effects of Hypoestes rosea in Acetaminophen-Induced Toxicity in Albino Rats

The leaves of Hypoestes rosea are in use as traditional medicine in the Niger Delta areas in Nigeria and the Western part of Cameroun for the management of different ailments in children, such as anaemia, malaria, fever and other ailments. Regardless of its uses, scanty studies evaluating its organ protective effects exist. Therefore, this research study evaluates the nephroprotective and hepato-protective effects of Hypoestes rosea in acetaminophen-induced toxicity in Albino rats. The objectives of this research study are to evaluate the protective effect of Hypoestes rosea on the kidney and the liver of albino rats. Acetaminophen, which is frequently used as an analgesic and antipyretic drug at high doses, can be harmful to vital organs of the body, affecting the liver and kidneys. In this study, effects of an aqueous extract of Hypoestes rosea (AEHr) on liver function parameters and kidney function parameters of acetaminophen induced-toxicity in albino rats were evaluated using acute (15 days) and sub-chronic (30 days) duration of study and study group comprising of prophylactic (pre-treatment) and therapeutic (post-treatment) phases with six experimental groups in each phase. A total of 112 adult apparently healthy Albino rats weighing (180-220g) were used for this study, divided into six experimental groups of extract control (EC), negative control (NC), positive control (PC), AEHr100mg/kg b w., AEHr 200mg/kg b w., and AEHr 300mg/kg b w. groups each of six rats. At the end of the research study period, blood samples were collected through jugular puncture for liver and kidney function parameters. Results showed that acetaminophen-induced toxicity in albino rats caused toxicity to the kidney and toxicity to the liver, as evidenced by the raised levels of potassium, urea, creatinine and low bicarbonate from the renal function parameters and also as evidenced by significant elevation of bilirubin and liver enzymes with a significantly low total protein and albumin levels from the liver function parameters when compared with other experimental groups. Conversely, AEHr at different concentrations in a dose-dependent pattern at the different treatment phases and different duration periods were able to repair the injury to the kidney and liver caused by acetaminophen induction to normal. Consequently, the findings of this research propose that Hypoestes rosea contains active ingredients accountable for the nephroprotective and hepato-protective abilities in rats and can be recommended for more studies using higher mammals.

Provenance of mixed volcaniclastic-carbonaticlastic gravity-flow deposits: a case study from the Cretaceous of the southern Central Alborz (Iran)

ABSTRACT Understanding the petrographic and geochemical characteristics of different tectonic settings is essential to improving traditional methods of identifying the provenance of palaeo-sedimentary environments. This research focuses on the K2b unit, which consists of mixed carbonate and volcanic lithic sandstones located in Iran with the age of the Turonian-Early Campanian period. Five sedimentary lithotypes with distinct petrographic and geochemical signatures were identified in the Turonian/Lower Campanian K2b unit, which consists of coarse-grained fan-delta strata. Carbonate and volcanic lithic fragments are the most characteristic components of mostly quartzo-lithic to felspatho-litho-quartzose sandstone layers, documenting a unidirectional paleocurrent pattern with the north-eastward direction. The original composition has undergone diagenesis, resulting in the precipitation of authigenic carbonates and depleting Rare Earth Elements (REE) except for Eu, which shows a positive anomaly. The K2b fan delta was situated on the margin of the proto-south Caspian back-arc basin, and the sediments were sourced from the undissected magmatic arc. The gravity flow deposits in the K2b unit were likely triggered by tectonic activity in the catchment area of the fan delta, leading to uplift and formation of relief associated with the regional Mosha Fault and, on a larger palaeogeographic scale, with subduction of the Arabian plate beneath the Iranian plate during Turonian-Early Campanian.

Investigating Dirofilaria immitis isolates infecting domestic canines and their susceptibility/resistance patterns to macrocyclic lactones in the northern region of the Mississippi Delta area (southeast Missouri)

Previous reports of macrocyclic lactone (ML) resistance in Dirofilaria immitis, the parasitic nematode which causes heartworm disease, have mainly been from the southern Mississippi Delta region. Southeast Missouri (SEMO), forming the northern boundary of this region, has not previously been well studied. The area is an ideal propagation region for heartworm infection and possibly for the spread of ML resistance. To assess whether D. immitis isolates infecting domestic canines in SEMO exhibit evidence of resistance to MLs, domestic canines, presented to veterinary facilities testing positive for heartworms through antigen and microfilariae (MF) examination, were utilized in the study. Using a descriptive epidemiological cross-sectional study, from March 2021 through February 2022, blood sample collection from 96 canines living in SEMO testing positive for heartworms were analyzed. MiSeq technology was utilized to sequence specific genetic markers associated with susceptibility/resistance for MLs in D. immitis isolates. Genomic data revealed most D. immitis isolates had genotypic profiles consistent with resistance to MLs. Of the 96 samples tested, 91 (94.8%) had a resistant genotype, 4 (4.2%) had a mixed genotype, and 1 sample (1%) genotyped as susceptible. While detailed and reliable medical histories were not available for most canines, detailed medical history from 2 canines indicated evidence of phenotypic resistance that was consistent with their genotypes. However, in vivo preventive tests are needed to confirm a high frequency of phenotypic ML resistance in D. immitis from this region. Increasing resistance patterns to MLs indicate the approach to heartworm prevention/treatment protocol should be reconsidered. New measures may be required to stop heartworm disease.

A Contrastive Analysis of the Morphological and Syntactic Aspects of Urhobo and Ijaw Languages

The study undertakes a contrastive analysis of the morphological and syntactic aspects of Urhobo language and the Izon language, which are two indigenous languages spoken in the Niger Delta area in Nigeria. Contrastive analysis is used as the theory of preference to explore these languages, to show their similarity and points of divergence. The findings from the study attest to the similarity of these languages predictably as a result of their shared origin as they both are from the same Niger-Congo language family. There are cases of exact translations and linguistic interconnectedness between both languages in the morphological level. The study also confirms that there is noticeable difference in all levels of linguistics that makes both languages not mutually intelligible. The research’s implications include recommendations for language teaching and preservation as both languages are highly relevant for intercultural communication. The study also recommends that further research should be done in Nigeria’s indigenous languages as a way to respect and maintain unique linguistic identities. Scholars from different Nigerian languages should encourage the development and the growth of the indigenous languages to stop them from going into extinction. English language is the official language in Nigeria, it is the language of government, commerce, education, law, mass media and other areas of communication at the official level. The Nigerian language learner encounters so many problems in learning English. This paper reveals the importance of our indigenous languages.

The influence of enterprise dormitories on the urban integration of migrant workers in China: an exploration of two distinct migration stages of individual and family migration and the differences between them

The role of enterprise dormitories as the main living arrangements of Chinese migrant workers who are registered as rural residents but make their living in cities in pursuit of urbanisation cannot be ignored. However, the existing research on living spaces and the urban integration of migrant workers lacks sufficient focus on enterprise dormitories. Using the logit model to examine representative data on the Pearl River Delta and Yangtze River Delta areas and applying a national dataset taken from the China Migrants Dynamic Survey, we analyse how enterprise dormitories affect the urban integration of migrant workers across the different migration stages in this paper. The research results reveal that there are two migration stages in the urban integration of migrant workers. In the individual migration stage, based on the production target, enterprises accommodate migrant workers as a means of reducing their labour costs by increasing the labour time input of migrant workers. Moreover, in the family migration stage, enterprise dormitories are conducive to the low-cost integration of migrant workers into urban society, but they negatively affect further family migration because of the insufficient family living space that they provide. This research offers the intellectual foundation required for not only resolving the contradiction between the family reunification of migrant workers and their employment situation but also for the optimisation of housing policy.

Revisiting the stratigraphic development of the postglacial, transgressive paleo-Changjiang (Yangtze River) mouth: A journey from tide-dominated estuary to delta

Abstract The transition between a tide-dominated estuary and a tide-dominated delta, which is observed in modern settings and repeatedly throughout the geologic record, is a critical process for understanding sea-level and environmental changes. This transition remains poorly documented, however, leaving a knowledge gap about the sedimentary and stratigraphic processes involved. To help bridge the gap, we reexamined the postglacial transgressive system beneath the modern Changjiang (Yangtze River) Delta, built by one of the world’s largest rivers, using new chirp data supplemented by correlation with previously documented boreholes. Our results revealed a previously undocumented tide-dominated estuary-to-delta transition around the Younger Dryas, with the pretransition evolution dominated by the retrogradation of the tide-dominated estuary, which fills most of the accommodation space in the lowstand incised valley. This transition occurred when the middle and seaward parts of the estuary reached the subaqueous modern Changjiang Delta area and underwent extensive tidal erosion. Overlying the tidal ravinement, a series of ridge-and-swale structures formed due to tidal/fluviotidal channelization on the mud-dominated heterolithic substrate, primarily consisting of delta-front sediments characterized by flat, stratified reflections (bedding) with shallowing-upward trends. Ridge orientation rotates clockwise from north to south, with intervening swales bifurcating from a common apex point, and these features are flanked by inclined and sigmoidal levee-like channel fills dominated by homogeneous mud (acoustically transparent material). We reinterpret these features as tide-dominated delta islands and distributary channels, rather than the previously interpreted erosional mud ridges in the seaward part of the estuary, as they align with patterns observed in classic tide-dominated deltas. These patterns also suggest a shift from delta-front to delta-plain environments coinciding with shoreline advance ca. 10 k.y. B.P., but this was preceded by the evolution of a backstepping delta. Our study highlights the interplay between sediment supply and sea-level fluctuations in controlling the large-scale stratigraphic and environmental evolution of tidal-dominated river mouth systems. In the transgressive, paleo-Changjiang mouth, this interplay drove the system to evolve through stages of retrogradational estuary, backstepping delta, and progradational delta, and each environment differs significantly from the pattern observed in the modern Changjiang Delta. This study provides important insights for evaluating the evolution and sequence-stratigraphic reconstruction of other tidal depositional systems.

Temporal change in channel form and hydraulic behaviour of a tropical river due to natural forcing and anthropogenic interventions

ABSTRACT Assessing the degradation of river channels is crucial in the Anthropocene era, particularly in the deltaic areas worldwide. The present study aims to investigate the degradation of the Mathabhanga-Churni River giving emphasis on the temporal change of channel morphology and hydraulic behaviour and comparing the current situation with the historical past based on planform morphology and meander geometry of 118 meander loops, and width, depth, cross-sectional area, and hydraulic behaviour (velocity, discharge, stream power) at 47 cross-sections. The absence of lateral dynamicity, the static character of channel sinuosity during the last century (1913–2018), and the constant meander morphology reflects the static meander geometry and degradation of the river. The reduction of average channel width, depth, and cross-sectional area supports the falling trend of channel forms. Findings on hydraulic behaviour indicate declining discharge (~50% reduction during 1915–2018) that induces the present-day downscaled velocity and lowered stream power. Neotectonics (eastward tilting of the Bengal delta) and anthropogenic stressors such as stream crossings, agriculture on river beds, brickfields, and urbanisation have a severe impact on the hydromorphology of the channel, turning the active river into a stagnant and polluted channel.

Assessment of coastal river water quality in Bangladesh: Implications for drinking and irrigation purposes.

Saltwater intrusion in the coastal areas of Bangladesh is a prevalent phenomenon. However, it is not conducive to activities such as irrigation, navigation, fish spawning and shelter, and industrial usage. The present study analyzed 45 water samples collected from 15 locations in coastal areas during three seasons: monsoon, pre-monsoon, and post-monsoon. The aim was to comprehend the seasonal variation in physicochemical parameters, including water temperature, pH, electrical conductivity (EC), salinity, total dissolved solids (TDS), hardness, and concentrations of Na+, K+, Mg2+, Ca2+, Fe2+, HCO3-, PO43-, SO42-, and Cl-. Additionally, parameters essential for agriculture, such as soluble sodium percentage (SSP), sodium absorption ratio (SAR), magnesium absorption ratio (MAR), residual sodium carbonate (RSC), Kelly's ratio (KR), and permeability index (PI), were examined. Their respective values were found to be 63%, 16.83 mg/L, 34.92 mg/L, 145.44 mg/L, 1.28 mg/L, and 89.29%. The integrated water quality index was determined using entropy theory and principal component analysis (PCA). The resulting entropy water quality index (EWQI) and SAR of 49.56% and 63%, respectively, indicated that the samples are suitable for drinking but unsuitable for irrigation. These findings can assist policymakers in implementing the Bangladesh Deltaplan-2100, focusing on sustainable land management, fish cultivation, agricultural production, environmental preservation, water resource management, and environmental protection in the deltaic areas of Bangladesh. This research contributes to a deeper understanding of seasonal variations in the hydrochemistry and water quality of coastal rivers, aiding in the comprehension of salinity intrusion origins, mechanisms, and causes.

Spatiotemporal variations and driving forces analysis of ecosystem water conservation in coastal areas of China

China's coastal zones, characterized by their ecological vulnerability and significant economic growth, demand effective water conservation management. Such management is pivotal not only for safeguarding water resources but also for ensuring ecological stability and promoting sustainable socio-economic development. In this study, based on the water balance model, the spatiotemporal dynamics of water conservation in the ecosystems of China's coastal areas from 2001 to 2021 were characterized by three dimensions: overall, zonal, and raster. The results show that: ① the distribution pattern of ecosystem water conservation in China's coastal areas from 2001 to 2021 is “high in the south and low in the north”, with a total amount of 117.726 billion m3/a, with the Pearl River Delta and Southwest Coastal Areas as the main high-value areas, and the overall water conservation and its capacity show a “ decreasing-rising-decreasing” pattern. The overall water conservation and its capacity show a fluctuating trend of “falling-rising-falling”. Additionally, water conservation capacity varied significantly among different vegetation types and across marine-terrestrial gradients, with the highest capacity recorded in evergreen coniferous forests and areas situated 140 km from the coastline. ②From 2001 to 2021, the water conservation capacity of China's coastal ecosystems exhibited significant temporal patterns and spatial differentiation along the marine-terrestrial gradient. The research suggests that these patterns of change are intricately linked with the stages of regional development strategies and ecological construction within these coastal zones. ③In China's coastal areas, a mere 11.63 % of the rasters showed significant changes in water conservation, dominated by highly significant and significant increases, mainly in the Southeast Coastal Area, the Pearl River Delta and Southwest Coastal Areas, and the Bohai Bay Coastal Area. This included areas such as the Yangtze River Delta silty coastal plain area, the Bohai Bay silty coastal plain area, the sandy silt coastal hilly terrace area of western Guangdong and Guinan, and other China coastal protection forest system construction projects. ④ Water conservation function within China's coastal ecosystems demonstrates a profound interconnection with both natural and socio-economic determinants. Natural elements such as elevation, slope, and precipitation positively correlate with water conservation metrics. Conversely, evapotranspiration and temperature are inversely related to conservation outcomes. In terms of social factors, water conservation has a significant negative correlation with GDP density and population density, with the highest negative correlation with the GDP2 density.

Polycyclic aromatic hydrocarbons and their halogenated derivatives in soil from Yellow River Delta: Distribution, source apportionment, and risk assessment

The distribution of polycyclic aromatic hydrocarbons (PAHs) and halogenated PAHs (HPAHs) in surface soils from the petroleum industrial area of the Yellow River Delta (YRD) in China were investigated. The total concentrations of 16 PAHs ranged from 19.6 to 1560 ng/g, while 22 HPAHs ranged from 2.44 to 14.9 ng/g. Moreover, a high degree of spatial distribution heterogeneity was observed for both PAHs and HPAHs, which is likely attributed to the distinct industrial activities in studied area. The combustion of biomass and petroleum were identified as primary sources of soil PAHs and HPAHs in the YRD. Furthermore, benzo[b]fluoranthene, benzo[k]fluoranthene, and benzo[g,h,i]perylene exhibited high ecological risks (with risk quotients of 1.47, 1.44, and 1.02, respectively) in specific sites within the YRD. Considering the high toxicity of HPAHs and their potential joint environmental effects with PAHs, continuous attention should be directed towards the environmental risks associated with both PAHs and HPAHs.