Loose Deposits Research Articles

Iron particles lower than 10 μm in drinking water dominate particle catalysis effect on disinfection byproduct formation

Iron particles could catalyze disinfection by-product (DBP) formation in drinking water distribution systems (DWDS), but the catalytic effects of iron particles considering size effects have not been focused. Here, we first found that fine particles (lower than 10 μm) dominated the particle catalysis effect of the iron particles on the formation of DBPs containing multiple Cl atoms (DBP-3Cl), especially those with aromatic structure and containing multiple N atoms (DBP-3N). The loose deposit particles were filtered through 50 μm (F50), 10 μm (F10) and 1 μm (F10) membranes, and their turbidity values were 231.6, 53.4 and 1.1 NTU, respectively. In mass ratio, F50, F10 and F1 accounted for 84 %, 15 % and 1 % of unfiltered samples. Notably, the lower mass F10 generated more DBP-3Cl and DBP-3N than F50. Metal crystals and natural organic matters showed little difference among different sizes. The high catalytic activity of particles in F10 due to size effect was proved to be the essential mechanism. F1 contained few particles to affect DBP formation. In toxicity evaluation, the toxicity of F10 was even higher than F50. Therefore, fine particles with sizes lower than 10 μm may play a dominate role in the catalytic effect on DBP transformation in DWDS.

Geothermal and structural features of La Palma island (Canary Islands) imaged by ambient noise tomography

La Palma island is located in the NW of the Canary Islands and is one of the most volcanically active of the archipelago, therefore the existence of geothermal resources on the island is highly probable. The main objective of this work is to detect velocity anomalies potentially related to active geothermal reservoirs on La Palma island, by achieving a high-resolution seismic velocity model of the first few kilometres of the crust using Ambient Noise Tomography (ANT). The obtained ANT model is merged with a recent local earthquake tomography model. Our findings reveal two high-velocity zones in the island’s northern and southern parts, that could be related to a plutonic intrusion and old oceanic crust materials. Conversely, four low-velocity zones are imaged in the southern part of the island. Two of them can be related to hydrothermal alteration zones located beneath the Cumbre Vieja volcanic complex. This hypothesis is reinforced by comparing the S-wave velocity model with the seismicity recorded during the pre-eruptive phase of the 2021 Tajogaite eruption, which revealed an aseismic volume coinciding with these low-velocity zones. Another low-velocity zone is observed in the southern part of the island, which we interpret as highly fractured rocks which could favour the ascent of hot fluids. A last low-velocity zone is observed in the central part of the island and associated with loose deposits generated by the Aridane valley mega landslide.

From rainfall to runoff: The role of soil moisture in a mountainous catchment

Soil moisture is essential in runoff generation, chemical transport, vegetation growth, and geological hazards like landslides in mountainous regions. However, due to its difficulty of measurement and its significant spatial heterogeneity and temporal variability, the dynamics and influence of soil moisture in the rainfall-runoff process are still not fully understood. In this study, precipitation, runoff, and soil moisture at multiple depths were measured and analyzed in a small, post-seismic mountainous catchment. Our results suggest that the dynamics of soil moisture could be explained by the characteristics of soil. The drastic change and the anisotropy of saturated hydraulic connectivity in the upper soil of the loose deposits in our catchment would lead to soil stratification at depths between 30 cm and 50 cm. The temporal variability of soil moisture was more highly correlated within the soil layers above and beneath the interface. Above the interface, besides vertical infiltration, occurrences of preferential flow were also frequent, transient perched water table may emerge during the wet period, making it a more active runoff contributor than the soil layers below the interface. When the level of rainfall reached the threshold, the correlation between rainfall and runoff became linear. This threshold response was more significant at soil layers above the interface, especially at the site with large topographic gradient. High antecedent soil moisture could skew the partitioning of precipitation into discharge, leading to an earlier flow peak. Our findings provide guidance on observation spot selection and the soil properties needed for the interpretation of future measurements, and may help develop flood early warnings system in small ungauged mountainous catchments with high flood risk.

Risk Assessment of Single-Gully Debris Flow Based on Dynamic Changes in Provenance in the Wenchuan Earthquake Zone: A Case Study of the Qipan Gully

After the Wenchuan earthquake on 12 May 2008, a huge amount of loose deposits was generated on the mountain surface in the earthquake zone, and vegetation was severely damaged, providing a rich source of material for debris flow, greatly increasing the danger. For many years, researchers have mainly considered the recovery of slope vegetation in assessing the risk of debris flow post-earthquake. However, field investigations have found that large amounts of the dynamic reserve materials in the gully have an important impact on the risk. Thus, based on field survey data, this paper takes the Qipan gully in Wenchuan County as an object and uses multi-source and multi-scale monitoring methods (Landsat series, Quickbird, and Unmanned Air Vehicle) to analyze and statistically study the provenance of the slope and gully both pre- and post- the earthquake. By comprehensively using game theory combination weighting and the cloud model, a dynamic risk assessment model for debris flow was constructed to evaluate the risk of debris flow from 2005 to 2019. The results show that the slope provenance post-earthquake was 7.7 times that of pre-earthquake, and by 2019 the slope provenance had recovered to the pre-earthquake level. Based on the statistical estimation of the amount of debris flow outbreak and the dredging of the blocking dam recorded in relevant data, the dynamic provenance of debris flow had decreased by about 781.3 × 104 m3 by 2019. Compared with considering slope provenance only, the assessment result of debris flow risk considering both slope and gully provenance is more realistic. The results are expected to provide reference and guidance for dynamic assessment of the risk of debris flow faced by increasing projects in high-seismic-intensity mountainous areas and to ensure the safety of people’s lives and property effectively.

A Model Describing the Process of the Electrodeposition of Zinc Loose Deposits in Pulsed Current Modes

A phenomenological model describing the change in the structural characteristics of loose zinc deposits obtained in pulsed current modes is presented. Comparison of experimental data on the structural properties of deposits with the results of model calculations indicates the adequacy of the model. To describe the features of the dendritic deposit growth and to determine the duration of the homogeneous structure formation in pulsed modes, the concept of critical thickness is introduced, at which a sharp change in the loose deposit density occurs. The dependence of the zinc deposit critical thickness on the pulse duty ratio under pulsed current modes is determined. The increasing of the pulse duty ratio leads to denser deposits with rounded dendrite shapes and fewer growth points, as compared with the deposit obtained in galvanostatic mode.

A Model Describing the Process of the Electrodeposition of Zinc Loose Deposits in Pulsed Current Modes

A Model Describing the Process of the Electrodeposition of Zinc Loose Deposits in Pulsed Current Modes

Control of Loose Deposits in a Simulated Drinking Water Distribution System Using Ultrafiltration

Loose deposits on water supply pipe walls easily fall off and may affect the safety of the drinking water supply, and the control of them has been a hot research issue in recent years. In this research, we used two simulated pipeline test reactors to systematically study the formation and shedding pattern of loose sediment on the pipeline, analyze its characteristics, and explore the control role of the ultrafiltration process on loose sediment in the water supply pipeline network. The results showed that the loose deposits adhered to the pipe reactor fed by filtered water formed slower than did that fed by unfiltered water, the maximum accumulation of the loose deposits was reduced from 2.17 to 1.46 g/m2. The reactor after ultrafiltration showed a reduction of more than 40% in the concentration of substances other than Ca and Si. Copper and zinc were reduced by more than 80%, while the iron content was reduced by 91.2%. When the shear force of the pipe wall of the water pipeline is less than 0.33 Pa, there are loose deposits formed on the pipe wall; when the shear force of the pipe wall of the water pipeline is greater than 0.94 Pa, it was found that the loose deposits on the pipe wall were shed more completely. Ultrafiltration removes most of the suspended living bacteria, but it is not effective in removing dissolved organic matter from the water, resulting in high peak levels of bacteria on the walls and in the effluent. The maximum bacterial content of the reactor effluent after ultrafiltration was 1.6 × 104 CFU/cm2 after 22 d. It is therefore necessary to consider the use of the ultrafiltration process in conjunction with other processes to achieve the ultimate goal of controlling microbial contamination in the pipeline network.

Mineral Associations of Concentrates from Gold-Bearing Placers of the Miass Placer Zone (South Urals) and Possible Primary Sources of Gold

Abstract —The placer deposits of the Miass valley in the Southern Urals have been known since the beginning of the 19th century. Over two centuries of mining more than 120 tons of gold have been extracted from alluvial and alluvial–deluvial placers. Despite the industrial significance of this territory, native gold of alluvial deposits is practically unstudied and there is no data on the mineral composition of concentrates. Native gold and heavy fraction minerals from seven placers of the Miass placer zone of deluvial–alluvial and alluvial types were researched. The study of the typomorphic features of native gold and distribution of heavy fraction minerals in loose deposits makes it possible to determine the genetic types of primary sources of placer formation. Chrome-spinel and ilmenite prevail in the concentrates, magnetite, epidote, rutile, titanite, clinopyroxene, hematite, zircon, garnets, and monazite are less common. Chromespinelides of various placers are represented by chromite and subferrichromite, they are characterized by a high average content of Cr2O3 (50.9 wt.%). Chromespinelide chemical composition features show evidence of its penetration into placer sediments from rocks of the ophiolitic association. The composition and morphological features of phosphates of rare earth elements (monazite and xenotime) indicate their metamorphogenic nature and penetration into placers from the Riphean strata. Native gold is characterized by a low degree of roundness. Mineral inclusions in native gold are represented by sulfides, arsenides, bismuthides, cuprous gold, platinoids. Composition of native gold from the Miass River valley placers varies over a wide range. The main admixtures are silver (4.5–23.4 wt.%) and mercury (up to 5.14 wt.%), copper (up to 2.03 wt.%) was noted in several grains. The EBSD study of native gold internal structure showed predominance of primary crystallization structures, a low degree of deformation and growth of gold-rich rims with a fine-grained mosaic structure. Formation of gold-rich rims in gold grains in placers is explained by recrystallization of the most deformed parts of gold during transportation. Placers occurred due to the destruction of primary sources located in the upper reaches of streams or near them, which is confirmed by a low degree of grains’ roundness. The composition of native gold in combination with a set of micro-inclusions indicate the gold–sulfide-quartz type of mineralization of most primary sources.

Probabilistic and deterministic-based approach for liquefaction potential assessment of layered soil

In the present study, deterministic and probabilistic approaches have been used for the assessment of liquefaction potential of ground during an earthquake. The deterministic approach was used to analyze and assess the liquefaction of loose saturated river bed deposit with emphasis on two benchmark locations. A wide range of earthquake data in the form of peak ground acceleration (PGA) values of 0.18 g, 0.37 g, 0.6 g and 0.75 g was used as input motions. The dynamic properties of soil were evaluated using standard penetration test (SPT) data obtained from the bore logs. The shear stress induced within soil deposit due to the seismic excitation was calculated in the form of cyclic stress ratio (CSR) and cyclic resistance ratio (CRR) in order to calculate the factor of safety (FOS) against liquefaction. In addition, liquefaction potential index (LPI) and probability of liquefaction (PL) were also calculated using input motion. It was observed, based on the probability analysis and liquefaction indices, that the shallow layer soil profile is safe against liquefaction, whereas deep layer soil profile is unsafe.

Modelling the evolution of debris flows after the 2008 Wenchuan earthquake

Strong earthquakes can trigger extensive landslides, generating abundant loose deposits that are prone to be remobilized as debris flows by subsequent rainfall events. The magnitude-frequency distribution of post-earthquake debris flows often changes significantly over time. However, the key parameters controlling the post-earthquake debris flow activity and magnitude were poorly understood. In this study, we selected a representative catchment in the Wenchuan earthquake-hit region to study the activity of debris flows from 2008 to 2020, as well as the changes in parameters due to material depletion, grain size coarsening and vegetation recovery. Samples were collected from the field in different years after the earthquake and were tested in the laboratory to obtain their geotechnical properties. A numerical model was improved by considering the changing properties to fit better to dynamic conditions after the earthquake. We found that the particle size of the loose material gradually coarsened, the shear strength showed an increasing trend, while the erodibility coefficient of loose material showed a decreasing trend. The evolution of these parameters controlled the magnitude-frequency of post-earthquake debris flows and also changed their behavior from slope failures in the first few years after the earthquake to concentrated surface runoff erosion (channel erosion) in later years. The results have an important implication for risk assessment and prediction of future debris flows in earthquake-prone regions.

Complex study of loose cave deposits of the central Asian region using X-ray analysis methods

The elemental and mineral composition of loose sediments from the Kan-i-Gut mine-cave (Central Asia) was compared. The obtained concentrations of Mn, Fe, and Zn agree with the minerals determined in the composition of samples from the middle and lower horizons. Increased concentrations of Y, as well as the correlation of this element with As in the researched samples were revealed, which gives grounds to assume the presence of yttrium arsenates in the loose formations. The mineral associations found in the mine-cave indicate the formation of the original karst cavity during sulfuric acid speleogenesis. The mineral gergeite was identified in this site for the first time.

Evolution of debris flow activities in the epicentral area, 10 years after the 2008 Wenchuan earthquake

The occurrence of debris flows after the earthquake not only damaged infrastructure but also caused large numbers of casualties. Analyzing the evolution of debris flows after the Wenchuan earthquake is significant for understanding the long-term impacts of the earthquake on the subsequent debris flow activities. This study made a continuous track of mass movements of loose deposits in all debris flow gullies from 2008 to 2018 along Provincial Road 303 (PR303) after the Wenchuan earthquake according to remote sensing images interpretation and field investigations. Four aspects, i.e. vegetation recovery, source materials, runout characteristics, and human activities were analysed to describe the evolution laws based on the 10-year inventory of debris flows. The loose deposits on the hillslope were found to be gradually transported into channels. A declining trend of mass transport rate from 2010 (24.5%) to 2018 (6.5%) was found. The occurrence frequency, magnitude, and mobility of debris flows were found to decrease. Recovery of vegetation made the loose deposits stable, whereas human activities of excavation of debris flows deposits promoted the occurrence of landslides. Three stages were divided for debris flows activities: the active period (2010–2014), the unstable period (2014–2017), and the recession period (after 2017). The decreasing trend of debris flows in the future is predicted.

In-situ cathodic electrolysis coupled with hydraulic backwash inhibited biofilm formation on a backwashable carbon nanotube membrane

Electro-coupled membrane filtration (ECMF) is an innovative and green technology for water and wastewater treatment. However, the dynamics of biofouling development in the ECMF system has yet been determined. This fundamental question was systematically investigated in this study through laboratory dead-end ECMF experiments. It was found that the ECMF process with an applied voltage of 3 V and a backwash interval of 60 min was capable of completely eradicating membrane biofouling in an extended filtration time of 1450 min. In contrast, membrane biofouling was much severer with a longer backwash interval of 720 min or without backwash. The complemental permeate analysis and membrane characterization results revealed that biofouling during ECMF involved two sequential stages. During the first stage, dead bacteria and their degradation debris formed a loose deposit layer on the membrane surface. The continuous accumulation of this layer decreased the electrochemical performance of the membrane cathode. As such, bacteria in the top deposit layer proliferated and secreted extracellular polymeric substances, which led to irreversible fouling in the second stage. Therefore, timely removal of the initial deposit layer by hydraulic backwash was crucial in preventing irreversible membrane biofouling. These findings provided novel insights into the synergistic effects of cathodic electrolysis and hydraulic backwash for biofouling mitigation.

New seismic monitoring center in South America to assess the liquefaction risk posed by subduction earthquakes

The east of Cali is composed of loose sand deposits with high water table levels. This condition and the high seismic hazard of the city make cyclic liquefaction one of the main hazards in the city, which may affect more than 600,000 citizens and important infrastructures such as the city’s main drinking water treatment plants. Therefore, it was decided to design and implement a seismic monitoring center to study the behavior of liquefiable soils under local seismogenic conditions, in which subduction earthquakes predominate. First, more than 130 earthquakes from two seismic monitoring centers with liquefiable layers in the USA were studied to determine the requirements for the adequate design of the monitoring center. Then, a robust geotechnical and seismic characterization of the study area including SPT, CPTu, and seismic and ambient noise tests were carried out. From this information, the specifications and location of the instruments and, in general, the characteristics of the monitoring center were defined. The monitoring center has been planned to be established in two stages, and the first one has already been built and commissioned. The implementation of the first stage allowed to adequately record 35 earthquakes from different seismogenic sources, most of them from subduction earthquakes, and to verify that the potentially liquefiable layer remains saturated throughout the year. Subsequent ground motion sensors will allow to deeply study and understand large shear strains and excess pore pressures generation in the soil deposit, as well as their relationships with different intensity measures. The experience shared herein can benefit the design, construction, and operation of other seismic monitoring centers across the world.

Disaster Mechanism and Evolution Characteristics of Landslide–Debris-Flow Geohazard Chain Due to Strong Earthquake—A Case Study of Niumian Gully

Taking the Niumian Gully landslide–debris-flow geohazard chain as an example, we analyze the disaster mechanism of the landslide–debris-flow geohazard chain and its evolution process through field investigation as a reference for disaster prevention and risk reduction in areas with strong earthquakes by analyzing the accumulative sliding amount and the critical rainfall for debris flow formed by loose deposits. Due to the 8.0 Ms earthquake in Wenchuan, the cumulative sliding of the slope reached 230.51 m, much greater than the critical sliding in the Longmen Mountain earthquake area. Permanent damage to the slope occurred, resulting in a landslide, which provided the material source for the occurrence of debris flows. When the study area experienced concentrated rainfall (e.g., exceeding 10.31 mm/h or 54.67 mm/d), loose deposits in the basin began to form a debris flow, causing a landslide–debris-flow geohazard chain. During the evolution process of the geohazard chain, the following stages were observed: pre-earthquake gestation, landslide starting during a strong earthquake, landslide blocking a channel and forming a dammed lake, bursting of the dammed lake flood–debris-flow, sliding of loose deposits, and reciprocating loose-deposit sliding and debris flows. Thus, the formation of the Niumian Valley geohazard chain can be attributed to the combined result of strong earthquake activities and rainfall. In addition, under the action of rainfall, the occurrence of the debris flow and unstable sliding of loose deposits also caused the reciprocating occurrence of debris flows, loose-deposit sliding, and flood-induced debris flows in the study area.

Subfossil Insect Collections From the Arctic of Northeast Asia and Northwest North America

Subfossil insects (mostly beetles) are common in the Late Cenozoic terrestrial loose deposits of the Arctic. The best-studied areas are those regions that remained ice-free during the Pleistocene — in Alaska and Yukon, northeast Siberia, and west Chukotka. Tertiary subfossil insects have been found in Alaska, Yukon, Canadian Northwest Territories, and Greenland. The northernmost sites (above 75°N) are Ellesmere and Meighen Islands in Canada, Kap Kobenhavn in Greenland, and Faddeyevsky and Navaya Sibir’ Islands in Siberia. Collections from North America and Russia are housed in research institutions such as The Geological Survey of Canada (GSC) in Ottawa, University of Alberta (UofA) in Edmonton, Paleontological Institute (PIN) in Moscow, and Institute of Plant and Animal Ecology in Yekaterinburg; collections from Greenland are housed in the Zoological Museum, University of Copenhagen. The collections are mainly used for research purposes, including reconstruction of past climate and environment, stratigraphy, origin of local faunas, and ecosystems of the past. A few extinct species have been described from the late Neogene and early Quaternary.

Prototype of an IoT-Based Low-Cost Sensor Network for the Hydrological Monitoring of Landslide-Prone Areas.

Steep slopes covered by loose unsaturated pyroclastic deposits widely dispersed in Campania, Southern Italy, are often subjected to shallow landslides that turn into fast debris flows causing a large amount of damage and many casualties, triggered by heavy and persistent precipitation. The slope of Cervinara, located around 40 km northeast of Naples, was involved in a destructive flowslide between 15 and 16 December 1999, triggered by a rain event of 325 mm in 48 h. Hydrometeorological monitoring activities have been carried out near the landslide scarp of 1999 since 2017 to assess the water balance and to identify major hydrological processes involving the cover and the shallow groundwater system developing in the upper part of the underlying limestone fractured bedrock. Since 1 December 2022, a remotely accessible low-cost network has been installed to expand the field hydrological monitoring. The use of a network of low-cost capacitive sensors, communicating within the domain of Internet of Things (IoT) technology, aiming at dispersed monitoring of soil moisture, has been tested. Specifically, the tested prototype network allows measurements of the soil water content at two different points, communicating through a Wi-Fi-based IoT system using ESP32 boards. The ThingSpeakTM IoT platform has been used for remote field data visualization. Based on the obtained results, the prototype of this IoT-based low-cost network shows the potential to expand the amount of hydrological data, suitable for setting up early warning systems in landslide-prone areas.

Interface Change and Toxicity Risks of Loose Deposits Induced by Boiling in Water with Discoloration

Boiling is commonly used as a point-of-use household water treatment. This study evaluated the effect of boiling on the water quality, with particles originating from loose deposits in drinking water distribution systems. Results showed that during the boiling process, turbidity did not have an obvious change before 60 °C, but it abruptly increased after 90 °C, and it finally reached about 220 NTU (initial 194 NTU) after boiling (100 °C) under a particle concentration of 100 mg/L with a slight initial discoloration. The particles had smaller size, more particle counts, and lower agglomeration after boiling. Boiling induced an increase of dissolved organic matter (DOM) in water, and the particles contributed to the DOM significantly. In addition, the particles had an increased specific surface area (from 106.8 to 123.4 cm2/g) and roughness after boiling. More importantly, the particles exhibited higher cytotoxicity after boiling for human gastric mucosal cells, and a good negative linear relationship was found between turbidity and cell viability. Interestingly, the increase of intracellular reactive oxygen species was observed in the water samples with particles added. Furthermore, particles promoted the formation of disinfection byproducts with a more aromatic structure, which had higher toxicity. This study states that removing particles before boiling is necessary.

Pollution characteristics of full-scale butterfly valves: Risk assessment of heavy metal release behavior influenced by the bacterial communities and corrosion products

Given that contamination of butterfly valves has not been well understood in drinking water distribution systems (DWDSs), this study aimed to investigate the synergistic adsorption/release effects of microorganisms and corrosives on heavy metals. Results showed that outer layer scales were relatively loose, while hard black inner scales were mainly composed of Fe3O4 and Fe2O3, allowing Ca, As, Cr, Tl, and Pb to accumulate with low-diverse bacteria, primarily Desulfovibrio. Loose black inner layer scales were mainly formed by Fe(OH)3 and Fe(OH)2, enabling Ca, Cr, and Pb to accumulate with high-diverse bacteria, notably Desulfovibrio, Xanthobacteraceae, and Gallionellaceae. Metals involved in the metabolic activity of bacteria showed a negative correlation with these bacteria. Metals complexed and precipitated extracellularly in bacteria exhibited a positive correlation with these bacteria. Individual Pollution Factor (ICF), Global Pollution Factor (GCF), and Risk Assessment Code (RAC) demonstrated high bio-availability risks for Cd, especially in loose deposits with significant mobility.

Перспективные методы обнаружения субмаринной разгрузки в Балтийском море и опыт их применения

Submarine discharge of groundwater (SDGW) is a hydrological process that typically occurs in coastal areas and is defined as the underwater inflow of fresh and brackish ground­water from the continent to the sea. The discharge of waters with a composition sharply differ­ent from seawater leads to the formation of hydrochemical anomalies in the near-bottom hori­zon and alters the composition of bottom sediments. Under different regional conditions, dis­charge can occur as a focused flow through cracks in karst and fissured rocks, as a diffuse flow in loose deposits, or through the recirculation of seawater in bottom deposits. Therefore, it is essential to consider local geological and hydrogeological conditions, as they can significantly influence the character and distribution of groundwater and, consequently, the possibility of submarine discharge and the likelihood of its detection. Despite the ubiquity of the SDGW process in the continental shelf zone, practical detection is often a challenging task. The aim of this study is to identify approaches that best allow for documenting the phenomenon of sub­marine discharge of groundwater in the southeast part of the Baltic Sea. Detecting submarine groundwater discharge in the Baltic Sea is crucial for understanding the processes in the wa­ter body and evaluating the ecological situation. The study examines various methods for detecting SDGW: computational-analytical, geophysical, radioisotopic, chemical, and biologi­cal. The expe­rience of their application in the southeastern Baltic Sea is characterized, allow­ing for the identi­fication of areas where submarine discharge of groundwater from Jurassic and Cretaceous hori­zons occurs. The conclusion is drawn that for effective detection of sub­marine discharge foci, a comprehensive approach involving various research methods is neces­sary.