Local River Research Articles

Characterising groundwater-surface water connectivity in the lower Gandak catchment, a barrage regulated biodiversity hotspot in the mid-Gangetic basin

The alluvial aquifer system of the Indo-Gangetic Basin (IGB) is one of the world’s most important freshwater resources, sustaining humans and river ecosystems. Understanding groundwater recharge processes and connections to meteoric and surface water is necessary for effective water resource management for human and wider ecological requirements. Parts of the mid-Gangetic Basin, across eastern Uttar Pradesh and Bihar, are characterised by stable long-term groundwater levels, high annual rainfall, and limited historical groundwater use compared to parts of Northwest India for example. In this paper we use a combination of environmental tracers and hydrograph observations to characterise sources of recharge and groundwater-surface water interaction using a transect approach across the catchment of the River Gandak, a major barrage-regulated tributary of the River Ganga. Stable isotope results show that the dominant source of groundwater recharge, in the shallow (0–40 m bgl) Holocene and underlying Pleistocene aquifer system (>40 m bgl), is local rainfall. The shallow Holocene aquifer is also supplemented by local recharge from river and canal seepage and irrigation return flow in the upper and mid parts of the catchment. These observations are corroborated by evidence from detailed groundwater hydrographs and salinity observations, indicating localised canal, river and lake connectivity to groundwater. In the middle and lower catchment, river discharge is dominated by groundwater baseflow during the peak dry season when barrage gates are closed, which contributes to ecological flows for endangered river dolphins and gharial crocodiles. Groundwater residence time tracers indicate active modern recharge in the shallow alluvial aquifer system across the catchment. In the shallow Holocene aquifer elevated arsenic (As), iron (Fe), and manganese (Mn) exceeded WHO drinking water guidelines in a minority of sites, and uranium (U) and fluoride (F) concentrations approach but do not exceed the WHO guideline values. These observations varied across the catchment with higher As, Fe and Mn in the upper and mid catchments and higher U in the lower catchment. Groundwater salinity was typically between 500 and 1000 μS/cm, and isolated higher salinity was due to recharge from flood-plain wetlands and lakes impacted by evaporation. At present, the Gandak catchment has relatively high rainfall and low abstraction, which maintains stable groundwater levels and thus baseflow to the river in the dry season. Potential future threats to groundwater resources, and therefore river ecology due to the sensitivity to changes in baseflow in the catchment, would likely be driven by reductions in local monsoon rainfall, changes in water management practices and increased groundwater use.

Mercury (Hg) Contaminated Sites in Kazakhstan: Review of Current Cases and Site Remediation Responses.

Mercury (Hg) emissions from anthropogenic sources pose a global problem. In Central Asia, Kazakhstan’s central and northern regions are among the most severely Hg-contaminated territories. This is due to two former acetaldehyde (in Temirtau) and chlor-alkali (in Pavlodar) plants, discharges from which during the second half of the 20th century were estimated over 2000 tons of elemental Hg. However, the exact quantities of Hg released through atmospheric emissions to the environment, controlled discharges to the nearby aquatic systems, leakages in the cell plant, and contaminated sludge are still unknown. The present review is the initiation of a comprehensive field investigation study on the current state of these contaminated sites. It aims to provide a critical review of published literature on Hg in soils, sediments, water, and biota of the impacted ecosystems (Nura and Irtysh rivers, and Lake Balkyldak and their surrounding areas). It furthermore compares these contamination episodes with selected similar international cases as well as reviews and recommends demercuration efforts. The findings indicate that the contamination around the acetaldehyde plant site was significant and mainly localized with the majority of Hg deposited in topsoils and riverbanks within 25 km from the discharge point. In the chlor-alkali plant site, Lake Balkyldak in North Kazakhstan is the most seriously contaminated receptor. The local population of both regions might still be exposed to Hg due to fish consumption illegally caught from local rivers and reservoirs. Since the present field data is limited mainly to investigations conducted before 2010 and given the persisting contamination and nature of Hg, a recent up-to-date environmental assessment for both sites is highly needed, particularly around formerly detected hotspots. Due to incomplete site remediation efforts, recommendations given by several researchers for the territories of the former chlor-alkali and acetaldehyde plant site include ex-situ soil washing, soil pulping with gravitational separation, ultrasound and transgenic algae for sediments, and electrokinetic recovery for the former and removal and/or confinement of contaminated silt deposits and soils for the latter. However, their efficiency first needs to be validated. Findings and lessons from these sites will be useful not only on the local scale but also are valuable resources for the assessment and management of similar contaminated sites around the globe.

Body Size Distribution and Ovarian Histology of Pisodonophis boro (Hamilton, 1822) (Anguillifomes: Ophichthidae) from Pranburi River Estuary, Thailand

Reproductive characteristics on the snake eel Pisodonophis boro, a commercially important and high-value food source species in Thailand, have never been reported. We determined the body size distribution and gonadal structure of P. boro during the reproductive cycle. Healthy specimens were collected by local Pranburi River stuarine fishermen during March 2015 to March 2016. The total length of P. boro ranged from 24 cm to 97 cm with mean value of 66.28 ± 2.59 cm (N = 105, mean ± SD). Subsequent macroscopic observation demonstrated that the gonad of P. boro is a paired and elongated organ located parallel to the digestive tract. Surprisingly, the 105 specimens were all female, suggesting the protogynous sex reversal or spatial displacement of sexes in this species. Furthermore, only early and late perinucleolar stage oocytes were histologically identified throughout this study (synchronous developing type), which is often observed in semelparous fish species. These unique reproductive features of this eel in Thailand warrants further investigations on the male-female distribution and precise reproductive mode.

Lithostratigraphy of the Palaeoproterozoic Hekpoort Formation (Pretoria Group, Transvaal Supergroup), South Africa

Abstract The Palaeoproterozoic Hekpoort Formation of the Pretoria Group is a lava-dominated unit that has a basin-wide extent throughout the Transvaal sub-basin of South Africa. Additional correlative units may be present in the Kanye sub-basin of Botswana. The key characteristic of the formation is its general geochemical uniformity. Volcaniclastic and other sedimentary rocks are relatively rare throughout the succession but may be dominant in some locations. Hekpoort Formation outcrops are sporadic throughout the basin and mostly occur in the form of gentle hills and valleys, mainly encircling Archaean domes and the Palaeoproterozoic Bushveld Complex (BC). The unit is exposed in the western Pretoria Group basin, sitting unconformably either on the Timeball Hill Formation or Boshoek Formation, which is lenticular there, and on top of the Boshoek Formation in the east of the basin. The unit is unconformably overlain by the Dwaalheuwel Formation. The type-locality for the Hekpoort Formation is the Hekpoort farm (504 IQ Hekpoort), ca. 60 km to the west-southwest of Pretoria. However, no stratotype has ever been proposed. A lectostratotype, i.e., the Mooikloof area in Pretoria East, that can be enhanced by two reference stratotypes are proposed herein. The Hekpoort Formation was deposited in a cratonic subaerial setting, forming a large igneous province (LIP) in which short-termed localised ponds and small braided river systems existed. It therefore forms one of the major Palaeoproterozoic magmatic events on the Kaapvaal Craton.

Filling of sedimentary basins and the birth of large rivers: The lower Danube network in the Dacian Basin, Romania

Large rivers typically form in the final phase of evolution of sedimentary basins. By that time the sediment supply balances out the accommodation, local rivers coalesce into larger rivers and seek pathways to flow out of the basin into areas where accommodation is available. Very often, this is controlled by tectonics controlling sediment supply and accommodation or facilitating opening inter-basinal gateways. Using subsurface data (seismic and well logs), this paper discusses the controlling factors that lead to the birth of large, continental-scale rivers using the Danube River in the Carpathians foreland basin as a study example. The Proto-Danube originated in the North Alpine Foreland basin around 19–18 Ma and prograded southwards across the Vienna basin (14–13 Ma) and Pannonian basin (10–5 Ma) before reaching the Dacian basin. The Dacian basin took shape during the mid-Miocene and initially consisted of a number of individual and loosely connected depocenters, which were subsequently filled by local sediment sources. These sources typically reflect the uplift and erosion history of the closest orogenic segment. As the accommodation filled, the fluviatile networks coalesced and merged with the Paleo-Danube around 4 Ma, which flowed closer to the Carpathians, about 100 km north of the present path. Continued subsidence in the eastern part of the foreland basin controlled the further evolution of the Paleo-Danube that formed a large delta system, a precursor of the present-day Danube Delta. Eventually, the delta depocenter advanced into the Black Sea in the Romanian/Pleistocene. We interpret this to be the result of increased sediment supply due to renewed uplift of the Carpathians. Comparing the evolution of the Danube River drainage with other continental scale rivers around the world, we can conclude that the Danube represents an uncommon river system characterized by transiting multi-basin drainages. Initially, multiple small rivers filled sub-basins from different directions and these coalesced at later stages. Most large modern rivers, similar in size, formed within a simpler tectonic frame with sediments commonly supplied along a well-defined tectonic trend.

Unravelling the hydrological effects on spatiotemporal variability of water chemistry in mountainous rivers from Southwest China

AbstractUnderstanding the effects of hydrological processes on solute dynamics is critical to interpret biogeochemical processes. Water chemistry and isotopic compositions of surface water (δ18Ow and δDw) were investigated in rivers from Southwest China to study the effects of hydrological variability on biogeochemical processes. The inverse relationship between deuterium excess (d‐excess) and δ18Ow could be ascribed to non‐equilibrium fractionation processes, and the slope of the Local River Water Line was much lower than the Local Meteoric Water Line, suggesting the post‐precipitation evaporation pattern. The evaporation fraction (1–f) was estimated by the d‐excess method, varying from 0.01 to 0.18. (1–f), was a function of water temperature and drainage mean elevation, indicating that evaporation easily occurs at high temperatures in low‐elevation regions. The hydrological processes co‐varied with solute dynamics in the river network, and fluid transit time and temperature were likely responsible for the co‐variations. Also, we found that hydrological processes played an important role in solute dynamics through shifting the geochemical processes (e.g., enrichment, water‐rock reaction, photosynthesis, and secondary mineral precipitation). This study highlights that biogeochemical processes co‐vary with hydrological processes, and we suggest that investigating hydrological processes can help to understand biogeochemical processes.

Colorectal Cancer Risk and Prevention Knowledge among Adults Attending Public Health Facilities in Obudu, Cross River State, Nigeria

Background: Colorectal cancer (CRC) is the 5th most frequent cause of cancer-related deaths in Nigeria. As with other cancers, CRC risk is multifactorial, including issues such as poor diet, obesity, alcohol abuse, physical inactivity, age above 50 years, history of adenomatous polyps, inflammatory bowel disease, and family history of CRCs or polyps.
 Aim: The study aimed to ascertain the level of knowledge of risk factors and preventive measures against CRC among adults attending health facilities in Obudu Local Government area Cross River State, Nigeria.
 Study Design: A descriptive survey research design was used.
 Place and Duration of Study: Urban health facilities in Obudu Local government area, Cross River state between 2017 and 2019.
 Methodology: The sample of the study comprised 310 attendees of health facilities. A structured questionnaire was the main instrument used for data collection. Face validity was employed. The split-half method was used to establish the reliability of the instrument with thirty adults in a neighboring town.
 Results: Findings showed that males had better knowledge of risk factors (75.3%) than females (45.8%); and males had better knowledge of prevention of CRC (82.1%) than females (57.2%), hence showing a significant association (P=.002, P=.003) between gender with knowledge of risk factors and prevention of CRC respectively. There were also significant associations between age (P=.007, .001) and educational level (P=.002, .006) with knowledge of risk factors and prevention of CRC respectively. This showed that younger ages and higher education were associated with better knowledge of CRC.
 Conclusions: Less knowledgeable women and persons with low educational level should be targeted with messages on CRC. Health educators should intensify their health education campaign on the importance of screening as the major preventive measure against CRC at the household level. Government and non-governmental organizations (NGOs) should sponsor the provision of resources and screening facilities.

Dynamics of river plumes in the South Brazilian Bight and South Brazil

The plumes from the rivers of the South Brazilian Bight (SBB) and South Brazil (SB) were studied using a realistic model configuration. River plume variability on continental shelves is driven by the input of river runoff into the shelf, by wind variability, and also by ambient currents and its seasonal variability, especially the Brazil Current, which are realistically modelled in this study. It is presented a simulation of 4 years using a nested configuration, which allows resolving the region around Florianópolis with very high resolution (∼150 m). The dispersion of river plumes was assessed not only with the hydrodynamical model results but also by using passive tracers whose dynamics was analyzed seasonally. Several dyes were released together with the river discharges. This approach allowed calculating the depths of the riverine freshwater, and the resulting regions affected by the plumes. Northward intrusions of waters from the southern region, under the potential influence of the distant La Plata river plume, were evaluated with a Lagrangian approach. The local river plumes are confined to the inner shelf, except south of 30°S where discharges from Lagoa dos Patos disperse over the shelf in the spring and summer. The Brazil Current flowing southward over the slope prevents the river plumes from interaction with oceanic mesoscale dynamics. The river plumes are, thus, mainly controlled by the wind forcing. The plumes from SBB are able to disperse until SB following the southward wind regime typical of the summer. And both the SB and La Plata river plumes are also able to reach SBB, forced by the northward wind typical of the winter season, until the latitude of 25.5°S. A low salinity belt (below 35) is present along the coastal region of SB and SBB year-round, supported by contributions from both the large and small rivers. The interaction between the different plumes influences the dispersion patterns, shielding the Florianṕolis coastal region from plumes of distant rivers, and dispersing the plume of SBB rivers away from Santa Catarina Island as it disperses southward during the summer months.

Recurrent rock avalanches progressively dismantle a mountain ridge in Beichuan County, Sichuan, most recently in the 2008 Wenchuan earthquake

Large earthquake-triggered landslides, in particular rock avalanches, can have catastrophic consequences. However, without accelerometer records, the recognition of slopes prone to such failures remains difficult, because slope-specific seismic response depends on many factors including local topography, landforms, structure and internal geology. We address these issues by exploring the case of a rock avalanche of >3 million m3 triggered by the 2008 Mw7.9 Wenchuan earthquake in the Longmen Shan range, China. The failure, denominated Yangjia gully rock avalanche, occurred in Beichuan County (Sichuan Province), one of the areas that suffered the highest shaking intensity and death toll caused by co-seismic landsliding. Even though the Wenchuan earthquake produced tens of large (volume > 1 million m3) rock avalanches, many of which resulted in dangerous landslides, few studies so far have examined the pre-2008 history of the failed slope or reported on the stratigraphic record of mass-movement deposits exposed along local river courses. The presented case of the Yangjia gully rock avalanche shows the importance of such attempts as they provide information on the recurrence of large slope failures and their associated hazards. Our effort stems from recognition, on 2005 satellite imagery, of topography and morphology indicative of a large, apparently pre-historic slope failure and the associated breached landslide dam, both features closely resembling the forms generated in the catastrophic 2008 earthquake. The follow-up reconstruction recognizes an earlier landslide deposit exhumed from beneath the 2008 Yangjia gully rock avalanche by fluvial erosion since May 2008. We infer a seismic trigger also for the pre-2008 rock avalanche based on the following circumstantial evidence: i) the same source area (valley-facing, terminal portion of a flat-topped, elongated mountain ridge) located within one and a half kilometer of the seismically active Beichuan fault; ii) significant directional amplification of ground vibration, sub-parallel to the failed slope direction, detected via ambient noise measurements on the ridge adjacent to the source area of the 2008 rock avalanche and iii) common depositional and textural features of the two landslide deposits. Then, we show how, through consideration of the broader geomorphic and seismo-tectonic contexts, one can gain insight into the spatial and temporal recurrence of catastrophic slope failures in Beichuan County and elsewhere in the Longmen Shan. This insight, combined with local-scale geologic and geomorphologic knowledge, may guide selection of suspect slopes for reconnaissance, wide-area ambient noise investigation aimed at discriminating their relative susceptibility to co-seismic catastrophic failures. We indicate the feasibility of such investigations through the example of this study, which uses 3-component velocimeters designed to register low amplitude ground vibration.

Scale relationship between landscape pattern and water quality in different pollution source areas: A case study of the Fuxian Lake watershed, China

Understanding the scale relationship between landscape pattern and water quality is of great significance for improving water pollution and guiding the rational planning of land use in watersheds. At present, most existing studies take the watershed as a whole to explore the scale relationship between landscape pattern and water quality. Research on different types of pollution sources is still lacking. According to the characteristics of the pollution source in the watershed, the study of the multiscale effects of landscape pattern of different pollution source areas on water quality will help better the understanding of the impact of the surrounding landscape on the water quality of rivers, which is very important for local river management. In this study, a typical plateau lake basin, the Fuxian Lake basin, is taken as the research area, and the scale relationship between the surface landscape pattern and water quality in different pollution sources is taken as the research object. The redundancy analysis and multiple regression modeling are used to explore the impact of landscape pattern on water quality. The results show that the key landscape metrics that affect water quality indices in different pollution source areas and at different scales are quite different. Shannon's diversity index (SDI) had a significant effect on total phosphorus (TP) across the entire watershed. In the urban region, SDI and the mean shape index (MSI) have the greatest impact on chemical oxygen demand (COD) at the sub-watershed scale. In the phosphorus mining region, the landscape metrics SDI, Shannon's evenness index (SEI), and patch cohesion index (COHES) have significant effects on water quality, especially on TP. In the farmland and village region, the other 7 landscape metrics excluding the number of patches (NumP) become the leading indicators affecting water quality at different scales, among which total nitrogen (TN) has a particularly significant influence. Overall, the factor with the greatest effect on water quality was SDI in different pollution source areas. In terms of the scale effect, the landscape pattern has the strongest effect on water quality changes in the urban and phosphorus mining regions at sub-watershed scales, while in the farmland and village region, 300 m and 500 m are the areas where the landscape pattern has the strongest effect on water quality. These findings can provide decisional support for improving the water quality of lakes and rivers from the perspective of sustainable landscape management.

Industry in the Urban Space of Pre-industrial Cherepovets, 1880–1940s

The article is devoted to the analysis of the industrial development dynamics in Cherepovets in the late imperial period, during the revolution, the establishment of Soviet power and the first Five-Year Plans of industrialization.
 The purpose of the study is to reconstruct Cherepovets industrialization in the
 context of the urban space development in the 1880–1940s before the construction
 of a metallurgical plant and gaining the status of an industrial center.
 In the 1880–1940s Cherepovets industry mainly served the needs of the
 city and the governorate. Small industries dominated in the city. They were located on the city outskirts, as well as near local rivers. The present research is based on materials taken from the archives of the Cherepovets Museum Association, the Cherepovets Documentation Storage Center, the Russian State Historical
 Archive, and from official state statistics and periodicals. The analysis of
 these documents allowed the author to study the dynamics of Cherepovets industry
 development.
 The article states that developmental peaks that were associated with a
 quantitative increase in factories and plants in the city and that occurred on the eve and in the first years of World War I, as well as in the second Five-Year Plan of Soviet industrialization. The decline in industrial production was influenced by political
 events related to the end of World War I, the revolution, the civil war, and the outbreak of the Great Patriotic War. They had a decisive influence on the economy
 of the country and the city. In the period under the study the urban space grew due
 to the expansion of urban outskirts, where industrial enterprises were built, and the
 inclusion of neighboring villages in the urban area.
 The results obtained in the study are significant for understanding the processes of the industrial potential formation in Soviet industrial centers, as well as for the subsequent studies devoted to the development of socioenvironmental urban problems caused by industrialization.

Assessment of fine sediment river bed stocks in seven Alpine catchments

While the finest fraction of suspension has long been considered to have limited interactions with the river bed, several recent studies based on flume and field observations raise questions about this hypothesis which is fundamental for suspended load modeling and river management. In this study, we report a large field campaign in which we quantify the river bed stocks of fine particles in 7 contrasted Alpine catchments. Using a simple protocol, we performed more than 300 riverbed measurements of the local surface and subsurface stocks. Results indicate that even when the river bed surface contains no fine particles, significant quantities can be found in the subsurface layer which is in most cases the layer having the higher stocks. We also observed that stocks highly depend on the facies considered suggesting that storage processes are strongly driven by the local hydraulics and river bed characteristics. By integrating these local stocks at the catchment scale, we estimated that they could represent more than 50% of the mean annual suspended load in catchments having large alluvial braided sections. On the opposite, these stocks could be as small as 1% in highly eroded head water catchments. This suggests that the bed of large alluvial Alpine rivers can be considered as a significant source of fine particles. These observations were confirmed by using a simplified vertical scouring model to estimate conditions for these stocks to be released in the flow. However, the use of this model suggests that other bed reworking processes (channel widening and migration) have to be considered. Finally, these observations suggest that interactions between particles transported as suspension and gravel beds are far from being negligible processes in catchments having large alluvial sections typically found in Alpine environments.

Isotopic and hydrochemical evidence for the salinity origin in the coastal aquifers of the Pearl River Delta, Guangzhou, China

To better understand the origin of the saline groundwater in the Pearl River Delta (PRD), China, water samples were collected from local aquifers, rainfall regions and rivers for isotopic and hydrochemical analysis. The hydraulic connections between the aquifers in the study area were tested by analyzing a series of water samples from different months in one hydrological year (January 2017–January 2018). The total dissolved solids (TDS) results show that the highly saline groundwater only occurs in the granites, which indicates that the TDS distribution depends on the permeability of the aquifer material. Variations in the TDS and stable hydrogen and oxygen isotope ratios (δ2H and δ18O, respectively) of the water samples from different months reflect a dynamic balance among evaporation and precipitation in a hydrological year. Additionally, the very old radiocarbon (14C) ages and undetectable amounts of tritium (3H) in most of the groundwater samples suggest that the residence time of the groundwater in the aquifer is high. In general, the saline groundwater (TDS >5 g/L) in the area mainly originated primarily from seawater intrusion in the past. Meanwhile, the water contents of saline groundwater were affected by evaporation and long-term geochemical processes, such as water-rock, sulfate reduction, methanogenesis and ion exchange. The fresh groundwater in the area is from modern meteoric precipitation recharge.

A Robust Method to Update Local River Inundation Maps Using Global Climate Model Output and Weather Typing Based Statistical Downscaling

Global warming is changing the magnitude and frequency of extreme precipitation events. This requires updating local rainfall intensity-duration-frequency (IDF) curves and flood hazard maps according to the future climate scenarios. This is, however, far from straightforward, given our limited ability to model the effects of climate change on the temporal and spatial variability of rainfall at small scales. In this study, we develop a robust method to update local IDF relations for sub-daily rainfall extremes using Global Climate Model (GCM) data, and we apply it to a coastal town in NW Spain. First, the relationship between large-scale atmospheric circulation, described by means of Lamb Circulation Type classification (LCT), and rainfall events with potential for flood generation is analyzed. A broad ensemble set of GCM runs is used to identify frequency changes in LCTs, and to assess the occurrence of flood generating events in the future. In a parallel way, we use this Weather Type (WT) classification and climate-flood linkages to downscale rainfall from GCMs, and to determine the IDF curves for the future climate scenarios. A hydrological-hydraulic modeling chain is then used to quantify the changes in flood maps induced by the IDF changes. The results point to a future increase in rainfall intensity for all rainfall durations, which consequently results in an increased flood hazard in the urban area. While acknowledging the uncertainty in the GCM projections, the results show the need to update IDF standards and flood hazard maps to reflect potential changes in future extreme rainfall intensities.

Evaluation of sedimentation pond performance for a cleaner water production from an open pit mine at the edge of the Alto Tajo Natural Park

Controlling sediment produced by water erosion is the highest environmental challenge in steep, open pit sand mines located in erosive climates. Although restoration is impractical in active mine areas, sedimentation ponds are the Best Available Technique by the European Union to reduce sediment spillages from these environments. Few studies have described and supported such a solution with high resolution data. The María José mine is one of two active kaolin mines in the mining area of the Alto Tajo Natural Park, a highly erosive setting. It has a complex maintained pond system as a hydrologic and sedimentary control measure. In this landscape, mining can only be sustainable if clean water from production is ensured. The pond system retains sediment and water during a rain event, deposits the sediment, and eventually spills the water under controlled events. The María José spillages have been continuously monitored for suspended sediment concentration and water discharge at the mine outlet since 2012. During four years the efficiency of the pond system varied (96.7–99%), producing an average annual sediment yield of 5.6 Mg ha−1 y−1, a reduction of 98.4% compared with the sediment yield reported for similar local mines having no ponds. A quarter of this sediment was produced under controlled spillages allowing runoff management; the rest during large rainfall events when runoff decreased pond efficiency gives rise to an increase in suspended sediment concentration, as is typical of local natural rivers. Provided continuous maintenance, sediment ponds are shown to be a successful method to produce clean water. Successful pond efficiency implies that a mine produces water and sediment during baseflow conditions, allowing sufficient sediment volume to accumulate during rainstorms.

Effect of binder and moisture content on compactibility and shear strength of river bed green sand mould

Green sand mold casting process is an ancient manufacturing process where the manufacturing cost is very low and can produce intricate shape casting for different industrial applications. In recent years, the sand casting foundries are shifted from western countries to India and other Asian countries due to easy availability of manpower and raw materials. However, in India silica sand availability is decreasing gradually due to high production rate of sand casting products and huge civil construction, leads to increase in the cost of production of sand casting products. The current investigation aims to study the effect of binder and moisture percentage on local river bed sand mould compactibility and shear strength. The sand mould cylindrical specimens are fabricated as per American Foundry Society (AFS) to determine shear strength of the mould. The result shows that the mould compactibility decreases and shear strength increases with the increase in binder percentage. The optimum sand mould compactibility 52% and shear strength 0.56 kg/cm2 are observed at 7% moisture and 14% bentonite. Furthermore, the compactibility and shear strength of river bed sand mould and commercially used pure silica sand mould are compared and found local river bed sand may be used as alternative silica sand in green sand mould casting.

The myth of the Messinian Dardanelles: Late Miocene stratigraphy and palaeogeography of the ancient Aegean-Black Sea gateway

The Dardanelles region has formed a key gateway connecting the Eastern Paratethys and the Aegean/Mediterranean since the late Miocene. Its sedimentary sequences contain crucial information about connectivity and tectonics but so far lack unambiguous age constraints. Only a few Miocene marine episodes have been documented and fossil assemblages are predominantly composed of Paratethyan fauna (mollusks and ostracods). Here, we apply an integrated stratigraphic approach and use the recently established chronostratigraphy for the Eastern Paratethys to re-evaluate the faunal assemblages and palaeoenvironments of the Seddülbahir and İntepe sections that allegedly played a crucial role in the geodynamic evolution of the Dardanelles during the Messinian-Zanclean. The Paratethyan ostracods and mollusks, however, clearly indicate that these sections correspond to the middle Tortonian (~9 Ma; Bessarabian–Khersonian in Eastern Paratethys terminology). Nannofossil assemblages are dominated by a mixing of reworked taxa from the late Eocene and Oligocene and no age-diagnostic taxa have been observed. Dinoflagellate analyses are also hampered by reworking and mainly reveal non-marine (fresh to oligohaline) aquatic conditions. Fossil mammal remains in the Seddülbahir section and other localities in the region confirm the late Miocene age. Strontium (87Sr/86Sr) isotope ratios of the anomalohaline (brackish) ostracods are significantly below open ocean values and similar to values obtained from Khersonian ostracods of Bulgaria. Fresh water assemblages reveal much higher 87Sr/86Sr values, which are interpreted to reflect the composition of local rivers. We conclude that in late Miocene times the Dardanelles region was a fresh to anomalohaline embayment, ephemerally connected to the Eastern Paratethys. We found no evidence for a major Messinian erosional surface nor for marine Mediterranean fossils indicative of the early Zanclean. Our results furthermore indicate that the proposed Messinian age for the propagation of the North Anatolian Fault into the Dardanelles region must be revised.

A new approach to spatiotemporal estimation of the river state

The paper proposes a spatiotemporal method of analysis of the river state on the basis of the measurement of pollution level indicators in the context of its application in modern control systems. For the examined objects and measurements of their characteristic parameters described by differential equations, the issue of river state estimation was formulated on the basis of discrete measurements of water pollution carried out in control stations located along the river. Using such determined estimates of all control signals describing the level of pollution in the rivers, higher accuracy of water quality control was obtained in comparison with a case based solely on measurements of some easily accessible parameters. While designing the presented solution, a mathematical model of a physical object was used which was a section of a river understood as a certain mathematical abstraction binding together variables characterizing the state of the object, interaction of external signals and its reaction. It has been assumed that the dissolved oxygen (DO) concentration is the starting point at the stage of water quality status modeling as many other indicators of pollution level are associated with it. Such an indicator may be biochemical oxygen demand (BOD) which also reflects the DO consumption in rivers and represents the degradation of water quality. Having a mathematical model of pollution distribution in the river and real measurements, numerical simulations created the possibility of influencing the changes in pollution indicators (BOD and DO) in specific conditions and in a specific time. The paper verifies the compliance of the proposed mathematical model of the object with the actual representation of the local river Wislok in the Subcarpathian province in Poland.

Citizen science and aquatic macroinvertebrates: public engagement for catchment-scale pollution vigilance

ABSTRACT The Riverfly Partnership, launched in 2004, is a UK network of organisations and individuals working to protect river habitats and macroinvertebrate communities. The Riverfly Partnership’s Anglers’ Riverfly Monitoring Initiative (ARMI), launched in 2007, supports citizen science volunteers to monitor macroinvertebrates in their local rivers. In Manchester and surrounding areas, ARMI monitoring began in 2011 with volunteers from a fishing club active across the Irwell catchment. Whilst there has been mixed success establishing a robust long-term monitoring program, volunteers investigate issues raised by the local community and data provide a baseline against which river pollution events can be compared. For example, in April 2017 citizen scientists responding to a report of dead crayfish by an angler identified a pollution incident resulting in a catastrophic loss of macroinvertebrates along a 19 km reach of the River Irwell. Recognizing the limitations of the ARMI methodology for urban and degraded rivers nationwide led to the development of the Urban Riverfly index through the Riverfly Partnership so that citizen scientists can more effectively contribute to the work of government agencies mitigating urban river pollution. Citizen science has importantly been a catalyst for public engagement and environmental projects which should encourage wider public participation in river catchment management.

Plio-Quaternary landscape evolution in the uplifted Ardennes: New insights from 26Al/10Be data from cave-deposited alluvium (Meuse catchment, E. Belgium)

Despite a wealth of recent studies dealing with the evolution of the drainage network in the uplifted Ardennes massif (E. Belgium), especially from the Middle Pleistocene onwards, the Ardennian landscape evolution and long-term incision rates in the Meuse catchment remain poorly documented over the whole Plio-Quaternary. Alluvium-filled multilevel cave systems represent a relevant setting to unravel the Late Cenozoic history of regional river incision. We present here a dataset of 26Al/10Be concentration data obtained from fifteen pebble samples washed into the Chawresse system, one of the largest multi-level cave systems of Belgium, which developed in Devonian limestones of the lower Ourthe Valley, the main Ardennian tributary of the Meuse. The sample collection spans an elevation difference higher than 120 m and their depleted 26Al/10Be ratios yield burial ages ranging from ~0.25 to 3.28 Ma. After critical assessment of our dataset for intra-karstic reworking issues, the most striking outcome of the obtained burial ages is the acceleration by a factor five of the incision rates (from ~30 to ~150 m/Ma) during the first half of the Middle Pleistocene. Integrating this incision peak and our pre-burial denudation rates, we then revisit the existing framework of Plio-Quaternary denudation and river incision in the Ardennian Meuse catchment. Whilst our 26Al/10Be concentration data shed new light on the temporal and spatial variability of the local river and hillslope system response to coupled tectonic and climatic forcings, it simultaneously highlights sampling issues and the need for further chronological data.