Midstream Areas Research Articles

Source apportionment and ecological risk assessment of antibiotics in Dafeng River Basin using PMF and Monte-Carlo simulation.

Antibiotics, prevalent in aquatic ecosystems, pose a grave threat to human health and the ecological well-being. This paper performed a case study on Dafeng River Basin in southern China. Specifically, techniques including positive matrix factorization (PFM) and Monte-Carlo simulation were employed to comprehensively investigate the spatial variations, possible sources, and ecological risks of antibiotics in four groups: sulfonamides (SAs), macrolides (MLs), quinolones (QNs), and tetracyclines (TCs). The major findings were as follows: first, 43 and 39 antibiotics were detected in the surface water and sediments of the basin, respectively, where the respective total content were ND-490.08ng/L and ND-144.34μg/kg, and the QNs and TCs were the two dominating groups. Second, the highest antibiotic content in surface water (441.43ng/L) was observed in the midstream area, whereas the highest concentration in sediments (68.41μg/kg) was found in the upstream region. Third, the investigation identified five sources of antibiotics discharged to surface water: domestic sewage, agricultural drainage, livestock discharge, sewage treatment plants, and aquaculture; three sources were detected for antibiotics in sediments: aquaculture, sewage treatment plants, and livestock discharge. Fourth, QNs had a significantly higher ecological risk than the other three groups of antibiotics, and livestock discharge (31.4% contribution) and aquaculture (23.4% contribution) were the main sources of risks of antibiotic contamination in Dafeng River Basin. This study is expected to provide some reference for control and risk management of antibiotic pollution in Dafeng River Basin.

Patterns distribution, concentrations and sources of radioactive elements from black sand in the Red Sea coast, Egypt

In Egypt, the distribution of black sand in various coastal regions has been readily apparent by thorough research. Unfortunately, these investigations did not measure radioactivity in black sand, particularly in the vicinity of the Red Sea. Gamma-ray spectroscopy was used to detect the naturally occurring radioactivity from 238U, 232Th, 40K, and 226Ra in black sand samples from eight locations along the Red Sea coast: Ras Elbehar, Gemsa, Hurghada Elahiaa, Hurghada Titanic, Safaga, Qusier Elsharm Alqbly, Gabal Alrosass, and Marsa Alam. The resultant data were interpolated to represent the spatial distribution. Additionally, the potential rocks sources of radionuclides were geologically mapped to elucidate the relationship between rock components and radioactivity. The results showed that 226Ra, 232Th and238U were higher at samples collected from Ras Elbehar, Hurghada Elahiaa and Hurghada Titanic compared to the other sites. On the other hand, 40K showed the lowest mean value (75.3 ± 3.8 Bq/kg) in Hurghada Titanic samples, while it peaked (563 ± 28 Bq/kg) in Qusier Elsharm Alqbly samples. The interpolated results show notable differences in radioactive amounts between the north and south, which are indicative of several environmental conditions and human activities. Alkaline syenite, syenogranite, older granites (tonalite and granodiorite), and minor acidic volcanic/metavolcanic rocks make up the upstream area of the basin area draining into, for example, the Ras Elbehar locality (highest activity concentrations for 238U (1596 ± 80 Bq/kg) and 226Ra (886 ± 44 Bq/kg)), while alkali-feldspar granite, schist, and shale rocks make up the mid-stream area. The findings provide a basis for scientific forecasting on the impact of synthetic or naturally occurring radioactive isotopes introduced into aquatic environments.

Predicting the impact of climate change on crop water footprint using CMIP6 in the Shule River Basin, China

Quantitatively predicting the impacts of climate change on water demands of various crops is essential for developing measures to ensure food security, sustainable agriculture, and water resources management, especially in arid regions. This study explored the water footprints (WFs) of nine major crops in the middle and downstream areas of Shule River Basin, Northwest China, from 1989 to 2020 using the WF theory and CROPWAT model and predicted the future WFs of these crops under four emission and socio-economic pathway (SSPs-RCPs) scenarios, which provides scientific support for actively responding to the negative impacts of climate change in arid regions. Results indicated: (1) an increasing trend of the overall crop WF, with blue WF accounting for 80.31–99.33% of the total WF in the last 30 years. Owing to differences of planting structure, water-conservation technologies, and other factors, the multi-year average WF per unit area of crops was 0.75 × 104 m3 hm−2 in downstream area, which was higher than that in midstream area (0.57 × 104 m3 hm−2) in the last 30 years; therefore agricultural water use efficiency in the downstream area was lower than that in the midstream area, implying that the midstream area has more efficient agricultural water utilization. (2) an initial increase and then decrease of crop WFs in the study area under SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios by the end of the century, reaching their peak in 2030s which was higher than that from 1989 to 2020; with the maximum growth rates in the midstream area ranging from −0.85% in SSP5-8.5 to 5.33% in SSP2-4.5 and 29.74% in SSP5-8.5 to 34.71% in SSP2-4.5 in the downstream area. The local agricultural water demand would continue to increase and water scarcity issues would be more severe in the next 10–20 years, affecting downstream areas more. Under the SSP3-7.0 scenario, crop WF values of the midstream and downstream regions will be 2.63 × 108 m3 and 4.22 × 108 m3 in 2030, respectively, which is significantly higher than those of other scenarios and show a long-term growth trend. The growth rate of the midstream and downstream regions will reach 44.71% and 81.12%, respectively, by the end of this century, so the local agricultural water use would be facing more strain if this scenario materializes in the future. Therefore, the Shule River Basin should encourage development of water-saving irrigation technologies, adjust the planting ratio of high water consuming crops, and identify other measures to improve water resource utilization efficiency to cope with future water resource pressures.

Trace elements in the Upper Indus River Basin (UIRB) of Western Himalayas: Quantification, sources modeling, and impacts

This study conducted a comprehensive analysis of trace element concentrations in the Upper Indus River Basin (UIRB), a glacier-fed region in the Western Himalayas (WH), aiming to discern their environmental and anthropogenic sources and implications. Despite limited prior data, 69 samples were collected in 2019 from diverse sources within the UIRB, including mainstream, tributaries, and groundwater, to assess trace element concentrations. Enrichment factor (EF) results and comparisons with regional and global averages suggest that rising levels of Zn, Cd, and As may pose safety concerns for drinking water quality. Advanced multivariate statistical techniques such as principal component analysis (PCA), absolute principal component scores (APCS-MLR), Monte Carlo simulation (MCS), etc were applied to estimate the associated human health hazards and also identified key sources of trace elements. The 95th percentile of the MCS results indicates that the estimated total cancer risk for children is significantly greater than (>1000 times) the USEPA’s acceptable risk threshold of 1.0 × 10−6. The results classified most of the trace elements into two distinct groups: Group A (Li, Rb, Sr, U, Cs, V, Ni, TI, Sb, Mo, Ge), linked to geogenic sources, showed lower concentrations in the lower-middle river reaches, including tributaries and downstream regions. Group B (Pb, Nb, Cr, Zn, Be, Al, Th, Ga, Cu, Co), influenced by both geogenic and anthropogenic activities, exhibited higher concentrations near urban centers and midstream areas, aligning with increased municipal waste and agricultural activities. Furthermore, APCS-MLR source apportionment indicated that trace elements originated from natural geogenic processes, including rock-water interactions and mineral dissolution, as well as anthropogenic activities. These findings underscore the need for targeted measures to mitigate anthropogenic impacts and safeguard water resources for communities along the IRB and WH.

삼국시대 남강유역 취락 변천 연구

This study aims to examine the evolution and everyday relations of settlements in the Nam River basin within a socio-cultural context. Here, the everyday relations of settlements refer to the relationships between settlements distributed within the same cultural sphere. The location and structure of settlements in the Nam River basin during the Three Kingdoms Period were analyzed and classified into four types, with Type A being the largest and most complex. The settlements in the Nam River basin can be temporally divided into four phases based on their types. Phase I is characterized by settlements concentrated in the midstream area, with uncertain structures. Phase II marks the beginning of the widespread expansion of agricultural settlements. Large settlements (Type A), such as the Hachon-Galjeonri settlement group in the upstream and the Pyeonggeodong settlement group in the downstream, are surrounded by densely populated Type B, C, and D settlements. Entering Phase III, the settlement landscape undergoes rapid changes. The number of settlements decreases sharply, and the construction of tombs increases significantly. Following Phase II, the existence of large settlements in both the upstream and downstream continues, suggesting that the divided cultural spheres between the upstream and downstream persisted. In Phase IV, a clear differentiation begins to emerge between the cultural spheres of the upstream and downstream. In the downstream, large settlements disappear, while the influence of Gaya continues. Conversely, in the upstream, various cultures coexist. This is a result of the maximization of the ‘borderland’ nature of the upper regions, where the settlements located at the crossroads of transportation routes experienced the influx and coexistence of various cultures. Therefore, it is judged that the upstream and downstream had completely different cultural spheres in Phase IV, diverging around the midstream area.

Analysis of the spatial–temporal evolution and driving factors of carbon emission efficiency in the Yangtze River economic Belt

As an important economic growth pole and ecological area in China, the urban agglomeration of the Yangtze River Economic Belt (YREB) is the key to carbon emission reduction. Exploring the spatial–temporal evolution and driving variables of its carbon emission efficiency (CEE) is crucial for realizing the goals of carbon peaking and carbon neutrality. The super-efficiency SBM model, the nuclear density method, and the spatial autocorrelation method were used to discuss the spatial–temporal CEE characteristics of 105 cities in the YREB. On the driving factors of carbon emissions, the geographic detector and the Tobit model were combined to explore the spatial differentiation characteristics of the driving factors from the perspective of heterogeneity, and concurrently analyze the single-factor’s effecting intensity and impacting direction, as well as the dual-factors’ interaction effects. The findings indicated that the CEE of YREB generally showed a slow upward trend during 2006–2021. From the perspective of time dynamic evolution, the differentiation of efficiency intensified, and the overall development was toward the high efficiency level. Furthermore, the results of spatial pattern evolution showed that the CEE presents the pattern of “downstream areas > midstream areas > upstream areas”, “high in the east and low in the west”, “hot in the east and cold in the west”, while the spatial clustering effect was significant, showing the distributions of low-low clustering or high-high clustering. Moreover, the results of the geographic detector showed that government intervention, economic growth, and technological progress were the main driving factors. In addition, the interactions government intervention and the other factors were significantly detected. Tobit regression results showed that technological advancement and economic growth had a favorable impact on CEE, but foreign investment, urbanization, and government involvement had negative impacts. In the future, the correlations between provinces and cities should be strengthened and amplified to promote the integrated green development, as well as to improve the ecological environments.

Spatio-Temporal distribution characteristics and driving factors of traditional villages in the Yellow River Basin.

Currently, research on traditional villages mainly focuses on the current development status and evolutionary trends in specific regions, with relatively limited studies from a macroscopic and holistic perspective on the spatiotemporal evolution of traditional villages. Therefore, this study selects traditional villages in the Yellow River Basin (YRB) as the research object. By analyzing the spatiotemporal distribution characteristics and driving factors of traditional villages (TVs) in the basin, it aims to further promote high-quality development in the YRB and protect traditional cultural resources. Based on data from 892 village points of the first to sixth batches of TVs in the YRB, ArcGIS 10.8 spatial analysis techniques were employed to analyze the overall spatial pattern of TVs in the YRB. The results indicate: (1) In the basin, TVs are more numerous in the east than the west and more in the south than the north, forming clusters and contiguous distributions, with dense areas primarily in the upstream regions dominated by Qinghai Province and the midstream areas along the Shanxi-Shaanxi coast. (2) The number and scale of TVs in the basin generally exhibit an increasing trend, with imbalanced provincial distribution. More recent years show a more balanced distribution of villages and proportions, with a higher number of villages in the mountainous and plateau regions of the basin. (3) The layout center of TVs within the basin evolves with each batch, showing a migration pattern from north to south, back to north, and finally east to west. (4) The interaction of natural and social factors plays a synergistic role in driving the spatiotemporal distribution pattern of TVs. Among these, natural geographical factors are the primary factors. TVs are more commonly found in regions with low altitude sunny slopes, mild climate, abundant precipitation, proximity to ancient roads and rivers, gentle slopes, and soil predominantly comprising loess, brown earth, and alluvial soils. The cultural environment is a secondary factor, with TVs often located in areas with larger populations, developed economies, and rich cultural heritage.

Efektivitas Waktu Pelumuran Ekstrak Asam Belimbing Wuluh (Avverhoa Bilimbi) terhadap Penurunan Kadar Logam Berat Merkuri (Hg) pada Ikan Mujair (O.Mosambiccus)

This study aims to analyze the effectiveness of coating time with belimbing wuluh (averrhoa blimbi) extract in reducing the heavy metal mercury (Hg) levels in Mozambique tilapia (O.mossambicus). This research employed a Completely Randomized Design (CRD) method where the data were analyzed using variance analysis (ANOVA) and further tested by Duncan's multiple range test. The study was conducted using an experimental approach with two replications at three different locations: downstream (Bolangitang River), midstream (Sonuo Village), and upstream (Ollot Village). The treatments involved different coating times with averrhoa blimbi extract. The treatment levels consisted of four control levels: 5 minutes, 10 minutes, and 15 minutes. The research results demonstrated that a 15-minute coating time with averrhoa blimbi extract significantly reduced mercury levels in Mozambique tilapia in the downstream area of the Bolangitang River, with the highest reduction percentage reaching 63%. Meanwhile, the lowest reduction percentage was observed in the midstream area (Sonuo Village), with a 10-minute coating time resulting in a reduction percentage of 20.01%. Thus, the coating time of averrhoa blimbi extract was 50% effective in reducing heavy metal mercury (Hg) levels. This study contributes significantly to understanding the potential use of natural materials in addressing heavy metal pollution in freshwater ecosystems. It also highlights the relevance of utilizing local materials such as averrhoa blimbi as an alternative in conservation efforts and the protection of the environment and fisheries resources.

Uncertainty in measuring the role of climate change on debris-flow triggering on volcanoes - bulk-density, temperature and moisture analysis at Unzen Volcano (Japan)

As climate change creeps into the 21st century, the intensity of debris flows due to heavy and concentrated rainfall has increased in mountainous regions of Japan and East Asia. However, the relationship between climate change and an increase in debris flows is likely to be non-linear. Rainwater infiltrates more quickly into porous material, and the lack of vegetation cover increases evaporation and the temperature of surface sediments. In addition, periodic gully collapses bring fresh layers of porous material that increase the distance between the surface and the vadose zone. Therefore, to understand the relationship between volcanic debris flows (or lahars), parameters such as density, porosity, temperature, and moisture retention must be captured in detail in both time and space. The aim of this paper is to assess the role of loose, coarse, and porous sediments in lahar triggering. The present study was conducted at Unzen volcano in the Tansandani Guly between 31 May and 1 June 2023, 30 years after the last eruption. The dacite material is composed of a matrix of sand and coarse sand mixed with larger fractions and blocks, therefore traditional density measurement methods could not be applied, and a photogrammetric based method was used. In the field, sets of SfM-MVS photographs were taken before and after digging a hole in the sediments so that the measured mass could be compared to the volume of the hole in the sediments. After the sediments were dried, the dry and wet density, bulk density and porosity of the sample were calculated. When compared to the temperature data collected in the field, the following results were obtained: (1) The porosity of the volcanic material was highest in the lower reaches, followed by the upper reaches, and lowest in the middle reaches. This may be because fine sand washed out of the upstream area by rainfall is currently stored in the midstream area, which may facilitate debris flow generation. In addition, the downstream area has a high porosity, which may be due to the surrounding vegetation preventing the influx of new fine sand from the channel wall. (2) Because of the higher porosity and the lack of organic matter and vegetation cover, the increase in temperature acts more directly on the decrease in water content than in mountainous areas. Consequently, empirical equations for the potential for mudslides in volcanic areas with respect to surface temperature and soil moisture need to be developed for hazard and disaster risk management purposes.

Spatial differentiation and formation mechanism of ecological sensitivity in large river basins: A case study of the Yellow River Basin, China

Conducting ecological sensitivity assessment is a crucial approach for pinpointing regional ecological environmental issues, which can offer a scientific basis to aid in the prevention of regional ecological degradation and ensuring regional ecological security. With the protection and high-quality development of the Yellow River Basin (YRB) at the level of a national strategy in China, there is a critical need for a comprehensive assessment of the YRB’s ecological sensitivity. To this end, this study aimed to construct a new ecological sensitivity evaluation index system from three perspectives: natural ecosystem, natural-social ecosystem, and social ecosystem. The ecological sensitivity index was quantified using the entire-array-polygon indicator method, and the spatiotemporal changes of ecological sensitivity in the YRB and its sub-basins were analyzed from 2000 to 2020. The optimal parameters-based geographical detector model was employed to delve into the mechanisms driving the spatial variation in ecological sensitivity. We found that (1) from 2000 to 2020, ecological sensitivity in the YRB exhibited a bimodal trend. Spatially, it tended to be low in the western and eastern parts while it was relatively high in the southern and central regions. (2) The YRB displayed notable clustering effects in terms of ecological sensitivity. The source area showed both “high-high” and “low-low” groupings, the upstream area showed a predominance of “low-low” clusters, while the midstream area and downstream area were demonstrated by concentrated “high-high” clusters. However, the clustering effect in downstream gradually weakened over time. (3) The ecological sensitivity of the YRB was primarily driven by factors like shifts in climate change and soil erosion. There were also marked differences in spatial heterogeneity of ecological sensitivity across different sub-basins. Moreover, the influence of interactive factors on the YRB's ecological sensitivity and its sub-basins was enhanced. The research findings enhance our understanding of ecological issues faced by the YRB and establish a foundation for developing strategies to protect and manage its environmental ecosystem effectively.

Hydrogeochemical evolution of groundwater impacted by acid mine drainage (AMD) from polymetallic mining areas (South China)

Mining activities have long-term impacts on the groundwater of surrounding areas and deserve in-depth analysis and study. Herein, the geochemical mechanisms of acid mine drainage (AMD)-affected groundwaters were examined, and groundwater quality was assessed through water quality indices. 15 water samples from 7 domestic and 4 groundwater monitoring wells were tested for physical and chemical parameters in 2022, and multivariate statistical analysis was carried out with monitoring data from 21 domestic wells in 2010. The groundwater chemical composition varied from a predominantly Ca-HCO3 type in 2010 to a Ca-SO4 type in 2022. The isotopic values of δ18O and δD indicate that groundwater has not been significantly affected by evaporation. Changes in groundwater sulfate and total dissolved solids (TDS) levels over the twelve-year period confirmed the AMD infiltration impact on groundwater quality. The groundwater chemical properties changed more slowly than those of surface waters affected by AMD based on a cumulative increase in sulfate concentration of 29.94 mg/L. Changes in groundwater quality were investigated, namely, the spatiotemporal distribution of potentially toxic elements (PTEs), including Fe, Mn, Cd, Pb, and As. Mn concentrations in upstream groundwater areas near the mine decreased by 61.8% between 2010 and 2022. Conversely, groundwater in midstream areas had Mn concentrations of 2.25 mg/L and arsenic concentrations of 11.8 μg/L, both exceeding the WHO, 2022 standard. According to multivariate statistical analysis, Mn, Cd, and Pb originated from polymetallic minerals, whereas As was likely derived from the reduction of Fe/Mn hydroxyl oxides. AMD remediation improved contaminated upstream groundwater quality over 12 years, with a 36.8% improvement in WQI values. PTE distribution determined water quality changes; therefore, PTE contamination should be treated in mid- and downstream regions while contaminated groundwater should be treated upstream.

The dynamic patterns and driving factors of land use conflict in the Yellow River basin of China.

Land use conflict, as the spatial manifestation of conflicting human-land relationship, has a profound impact on sustainable use of regional land resources. Taking the Yellow River Basin (YRB) as an example, a land use conflict assessment model was constructed based on landscape pattern indices. The dynamic patterns and driving factors of land use conflict in the YRB and the corresponding driving factors were then assessed from 2000 to 2020 based on spatial autocorrelation analysis and the geodetector method. Significant spatial and temporal differences in land use conflict were observed in the YRB from 2000 to 2020. During this period, the area of stable controllable decreased by 3465 km2, whereas the areas of strong and extreme conflict increased by 34,964 and 13,057 km2, respectively. The expansion of areas with extreme and strong conflict mostly occurred in regions with high urbanization and human activity, including northern Shaanxi, Hetao Plain, and the Yellow River Delta. The distribution of land use conflict in the YRB from 2000 to 2020 was characterized by significant spatial agglomeration; high-value cluster conflict mainly extended from the midstream area to the upstream area, whereas low-value clusters tended to be concentrated in the upstream area of the Qinghai and Qilian Mountains. The spatial and temporal differentiation in land use conflict from 2000 to 2020 was influenced by factors related to the natural environment, geographic location, social economy, and regional policy in the YRB. The effects of elevation, distance to the nearest major river, population, economic density, and per capita disposable income of residents increased continuously during the study period, whereas the influences of mean annual precipitation and ecological retreat weakened. Analysis of the interactions between driving factors showed significant dual-factor and non-liner enhancement effects on the spatial and temporal differentiation in land use conflict. The findings provide a scientific reference for the comprehensive management of national land and ecological construction in the YRB.

Does the development of digital economy alleviate environmental problems-empirical evidence from the Yangtze River economic belt

The digital economy has become a new driving force for economic development. This paper takes 11 provinces and cities in the Yangtze River Economic Belt as research objects, constructs comprehensive evaluation indicators of environmental problems and digital economy, uses panel data of 11 provinces and cities in the Yangtze River Economic Belt from 2011 to 2020, and applies various econometric models to empirically test the impact of digital economy development on environmental problems in multiple dimensions. It was found that the development of the digital economy in the Yangtze River Economic Belt significantly mitigates environmental problems, a conclusion that still holds after the robustness analysis. The mediation analysis indicates that the development of the digital economy mitigates environmental problems through industrial structural upgrading and green technology innovation. The heterogeneity analysis shows that the digital economy development in the downstream areas of the Yangtze River Economic Belt has the largest environmental improvement effect and the smallest in the midstream areas. Spatial spillover analysis shows that digital economy development in the Yangtze River Economic Belt has significantly reduced environmental problems in surrounding areas through spatial spillover effects. The findings of the study provide empirical evidence that the development of the digital economy can mitigate environmental problems, and also serve as a policy reference for developing the digital economy and bringing the environmental improvement role of the digital economy into play.

Study on the spatial–temporal evolution and driving mechanism of urban land green use efficiency in the Yellow River Basin cities

Under the current social background of green, sustainable, and high-quality development, countries and regions have increasingly begun to regard green development as a major goal of their economic and social development plans. If the evaluation of urban land use efficiency continues to be based only on economic and social outputs, such research will not conform to the current social development situation. Therefore, this paper introduces negative impacts, such as environmental pollution, into the evaluation system, using the Super-EBM model to measure the urban land green use efficiency (ULGUE) of the Yellow River Basin (YRB) based on panel data from 2011 to 2019. Exploratory spatial data analysis, kernel density estimation, and trend surface analysis were used to study the spatial–temporal evolution characteristics of ULGUE, and the GTWR model was used to explore potential driving mechanisms. The overall ULGUE remained relatively flat from 2011 to 2015, before showing a climbing growth in the post-2015 period; at the sub-basin level, the ULGUE in the midstream area was significantly higher than that in the downstream area, and slightly higher than that in the upstream area, but the rate of ULGUE increase in the upstream area was significantly higher than that in other areas. The spatial aggregation degree of ULGUE showed an increasing trend followed by a decreasing trend, but at the end of the study period, it was still slightly higher than its initial level. The overall ULGUE showed a “polarization–non-differentiation–polarization” trajectory, with the highest efficiency area gradually shifting from the northwest to the central region. Although the driving factors vary between different cities, in general, the roles of technology input and pollution emission factors have gradually increased. This research provides a scientific reference for high-quality development of the YRB and supports the optimal allocation of land resources and regional coordinated development.

The role of human activities in the weakening of the propagation relationship between meteorological and hydrological droughts in the Heihe River Basin

AbstractMeteorological droughts could propagate into hydrological droughts and cause agricultural and societal damage. However, the quantitative impact of human activities on the drought propagation has not been well understood. Based on the precipitation and streamflow observational data and hydrological model simulations during 1961–2013, this study analysed the drought propagation characteristics and quantified the impact of human activities on the propagation in the upper and middle reaches of Heihe River Basin. The matched meteorological and hydrological drought events indicated that the drought propagation was characterized by a lagged onset, weakened drought severity and reduced development and recovery speeds. In the upstream area, the correlations between meteorological and hydrological droughts were significant, and human activities had a negligible impact on the drought propagation. In contrast, the impact from human activities was significant in the midstream area, and the effect was two‐fold. Specifically, human activities (e.g., reservoir regulation) reduced the propagation probability of one or several meteorological droughts propagating into a hydrological drought by 16%. Meanwhile, human activities had remarkable effects on long‐lasting and extreme hydrological droughts through reducing their duration and severity by 18% and 37% respectively. On the other hand, the occurrence probability of mismatched drought events, that is, meteorological droughts without causing hydrological droughts and hydrological droughts without preceding meteorological droughts, increased by 34% due to human interventions. Human activities also accelerated the development speed of slowly developing hydrological droughts. In addition, human activities increased the mean duration and severity of moderate hydrological droughts by 32% and 18%. The results are expected to provide scientific bases for understanding the formation and development process of hydrological drought and improving drought forecasting under global change.

Toxicity evaluation of a heavy-metal-polluted river: Pollution identification and bacterial community assessment.

The Salt River is an important urban river in Kaohsiung, Taiwan. In this study, the source identification and risk and toxicity assessment of the heavy-metal-contaminated sediments in the Salt River were investigated. The geo-accumulation index (Igeo), enrichment factor (EF), sediment quality guidelines (SQGs), potential ecological risk index (RI), pollution load index (PLI), and toxic units (TU) were applied to determine effects of heavy metals on microbial diversities and ecosystems. Results from the ecological and environmental risk assessment show that high concentrations of Zn, Cr, and Ni were detected in the midstream area and the sum of toxic units (ΣTUs) in the midstream (7.2-32.0) is higher than in the downstream (14.0-19.7) and upstream (9.2-17.1). It could be because of the continuous inputs of heavy-metal-contained wastewaters from adjacent industrial parks. Results also inferred that the detected heavy metals in the upstream residential and commercial areas were possibly caused by nearby vehicle emissions, non-point source pollution, and domestic wastewater discharges. Results of metagenomic assays show that the sediments contained significant microbial diversities. Metal-tolerant bacterial phyla (Proteobacteria: 24.4%-46.4%, Bacteroidetes: 1.3%-14.8%, and Actinobacteria: 2.3%-11.1%) and pathogenic bacterial phyla (Chlamydiae: 0.5%-37.6% and Chloroflexi: 5.8%-7.2%) with relatively high abundance were detected. Metal-tolerant bacteria would adsorb metals and cause the increased metal concentrations in sediments. Results indicate that the bacterial composition in sediment environments was affected by anthropogenic pollution and human activities and the heavy-metal-polluted ecosystem caused the variations in bacterial communities. PRACTITIONER POINTS: Microbial community in sediments is highly affected by heavy metal pollution. Wastewaters and vehicle traffic contribute to river sediments pollution by heavy metals. Proteobacteria, Bacteroidota, and Actinobacteria are dominant heavy-metal-tolerant bacterial phyla in sediments. Toxicity assessment is required to study risk levels of heavy-metal contained sediments.

Abnormal flow pattern of low wall shear stress and high oscillatory shear index in spontaneous vertebral artery dissection with vertebral artery hypoplasia.

Spontaneous vertebral artery dissection (sVAD) might tend to develop in vertebral artery hypoplasia (VAH) with hemodynamic dysfunction and it is crucial to assess hemodynamics in sVAD with VAH to investigate this hypothesis. This retrospective study aimed to quantify hemodynamic parameters in patients with sVAD with VAH. Patients who had suffered ischemic stroke due to an sVAD of VAH were enrolled in this retrospective study. The geometries of 14 patients (28 vessels) were reconstructed using Mimics and Geomagic Studio software from CT angiography (CTA). ANSYS ICEM and ANSYS FLUENT were utilized for mesh generation, set boundary conditions, solve governing equations, and perform numerical simulations. Slices were obtained at the upstream area, dissection or midstream area and downstream area of each VA. The blood flow patterns were visualized through instantaneous streamline and pressure at peak systole and late diastole. The hemodynamic parameters included pressure, velocity, time-averaged blood flow, time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), endothelial cell action potential (ECAP), relative residence time (RRT) and time-averaged nitric oxide production rate (TARNO). Significant focal increased velocity was present in the dissection area of steno-occlusive sVAD with VAH compared to other nondissected areas (0.910 m/s vs. 0.449 vs. 0.566, p < 0.001), while focal slow flow velocity was observed in the dissection area of aneurysmal dilatative sVAD with VAH according to velocity streamlines. Steno-occlusive sVAD with VAH arteries had a lower time-averaged blood flow (0.499 cm3/s vs. 2.268, p < 0.001), lower TAWSS (1.115 Pa vs. 2.437, p = 0.001), higher OSI (0.248 vs. 0.173, p = 0.006), higher ECAP (0.328 Pa-1 vs. 0.094, p = 0.002), higher RRT (3.519 Pa-1 vs. 1.044, p = 0.001) and deceased TARNO (104.014 nM/s vs. 158.195, p < 0.001) than the contralateral VAs. Steno-occlusive sVAD with VAH patients had abnormal blood flow patterns of focal increased velocity, low time-averaged blood flow, low TAWSS, high OSI, high ECAP, high RRT and decreased TARNO. These results provide a good basis for further investigation of sVAD hemodynamics and support the applicability of the CFD method in testing the hemodynamic hypothesis of sVAD. More detailed hemodynamic conditions with different stages of sVAD are warranted in the future.

고지형환경 분석을 이용한 보성강 중류지역 청동기시대 유적의 입지 특징

The purpose of this paper is to identify the topographical landscape of the Bronze age sites in the midstream area of the Boseong River which is currently submerged using the palaeomorphic environment analysis method and to restore the scale of the settlements. As a result of the palaeomorphic environment analysis, mountain(hills and pebbles), terrace, natural levee, alluvial fans, river island, and old river channel were observed in the midstream area of the Boseong River. Although there is a slight difference in the size of the settlement, the main location of the sites is the terrace. Terrace, a stable terrain free from river flooding, has been the best terrain for resident who have been living a settled life since prehistoric times. In order to resolve the uneven excavation status between settlements and tombs, the distribution ratio of 1 (dolmen): 10 (residential) surveyed in the Dalong district of Daegok-ri was substituted to calculate the residential prediction base for the terrain where dolmen were concentrated. As a result of analyzing the density of the settlements(residential base number/100㎡), the large settlements, central settlements, and middle settlements are separated, and the settlements is a residential center type, the tomb is a tomb center type, and the topography is different. The dolmens functioned to view the settlements and monitor other areas around it. The larger the settlement, the more a connecting network was formed within the relationship between the settlements. On the other hand, in unit settlements, settlements and tombs coexist within the same topographic space. The construction of a group of dolmens in an alluvial site away from the mountain seems to have been intended to maintain and strengthen the identity of the community.

Future drought risks in the Yellow River Basin and suggestions for targeted response

Drought risk has posed severe challenges to social development and human security in the Yellow River Basin (YRB), which is vulnerable to water scarcity. When dealing with drought, the insufficient coordination among various departments caused by the uncertainty of the comprehensive drought risk under climate change could lead to water conflict. Therefore, in this study, the drought risk changes in the YRB under shared socioeconomic pathway (SSP) scenario 5–8.5 were assessed by integrating the temporally dynamic hazard with the static vulnerability and exposure. Then, suggestions for drought risk management were developed according to the spatial differentiation of the drought risk characteristics. The results show that the drought hazard may increase as the standardized precipitation evapotranspiration index (SPEI) decreases from the baseline (1985–2014; −0.04 ± 0.26) to the mid-term period (2041–2070; −0.09 ± 0.21), and may decrease as the SPEI increases (0.14/10 yr) significantly (p < 0.01) during the long-term period (2071–2100). As a result, the drought risk in the upstream, midstream, and downstream areas may change by 0.26 ± 0.56, −0.05 ± 0.49, and −0.86 ± 0.38 levels in the long term, respectively, compared with the baseline. To reduce the drought risk, it is suggested that agricultural technology be further developed in the southwestern upstream, central upstream, and northern midstream areas; the water management be strengthened in the Hetao Plain and Ordos Plateau; the scale of exposure be controlled in the provincial capitals, southeastern midstream, and downstream areas; and the drought disaster research and early warning system be improved in the areas between 105°E and 110°E. Detailed suggestions for drought risk response were developed for each specific region.

Comparison of Various Annual Land Cover Datasets in the Yellow River Basin

Accurate land cover (LC) datasets are the basis for global environmental and climate change studies. Recently, numerous open-source annual LC datasets have been created due to advances in remote sensing technology. However, the agreements and sources of error that affect the accuracy of current annual LC datasets are not well understood, which limits the widespread use of these datasets. We compared four annual LC datasets, namely the CLCD, MCD12Q1, CCI-LC, and GLASS-LC, in the Yellow River Basin (YRB) to identify their spatial and temporal agreement for nine LC classes and to analyze their sources of error. The Mann–Kendall test, Sen’s slope analysis, Taylor diagram, and error decomposition analysis were used in this study. Our results showed that the main LC classes in the four datasets were grassland and cropland (total area percentage &gt; 80%), but their trends in area of change were different. For the main LC classes, the temporal agreement was the highest between the CCI-LC and CLCD (0.85), followed by the MCD12Q1 (0.21), while the lowest was between the GLASS-LC and CLCD (−0.11). The spatial distribution of area for the main LC classes was largely similar between the four datasets, but the spatial agreement in their trends in area of change varied considerably. The spatial variation in the trends in area of change for the cropland, forest, grassland, barren, and impervious LC classes were mainly located in the upstream area region (UA) and the midstream area region (MA) of the YRB, where the percentage of systematic error was high (&gt;68.55%). This indicated that the spatial variation between the four datasets was mainly caused by systematic errors. Between the four datasets, the total error increased along with landscape heterogeneity. These results not only improve our understanding of the spatial and temporal agreement and sources of error between the various current annual LC datasets, but also provide support for land policy making in the YRB.