Lake Sediments Research Articles

Effect of bridge height on airflow and aeolian sand flux near surface along the Qinghai-Tibet Railway, China

In this work, we studied the near-surface flow field structure of railway bridges with different heights through field investigation and wind tunnel simulation experiments. Meanwhile, we simulated the distribution of sand accumulation around a bridge via CFD software based on the sand accumulation around the Basuoqu bridge in the Cuona Lake section of the Qinghai–Tibet Railway. Results show that the sand around this railway bridge is mainly from the lake sediment on the west side of the railway and the weathered detritus on the east side. The height of the railway bridge in the sandy area affects the distribution of the near-surface flow field and the variation in speed on both sides of the bridge. The wind speed trough on both sides of the 6 m high bridge is higher, and the horizontal distance between the wind speed trough and the bridge section is 1.5 times that of the 3 m high bridge. Wind speed attenuates in a certain range on the windward and leeward sides of the bridge, forming an aeolian area; under the beam body, it is affected by the narrow tube effect, forming a wind erosion area. The height of the bridge determines its sand transport capacity. Under certain wind conditions, the overhead area at the bottom of the 3 m high bridge and its two sides do not have the sand transport capacity, so sand accumulates easily. Nevertheless, the sand accumulation phenomenon gradually disappears with the increase in bridge clearance height. The objectives of this study are to reveal the formation mechanism of sand damage for railway bridges, provide theoretical support for the scientific design of railway bridges in sandy areas, and formulate reasonable railway sand prevention measures to ensure the safety of railway running, which have certain theoretical significance and practical value.

Study of Volatile Organic Compounds in Emission from Bottom Sediments of Three Lakes with Impact of Anthropopression Using the Proton Transfer Reaction Mass Spectrometry

Studies of volatile organic compounds (VOCs) emitted from the bottom sediments of three Pomeranian lakes in Poland: Łazienkowskie, Rychnowskie, and Jeleń were conducted. All three lakes are subject to anthropogenic pressure but to varying degrees. In 2021, bottom sediment samples were taken from the lakes studied and an analysis of the emission of 20 volatile organic compounds was carried out using a proton transfer reaction mass spectrophotometer (PTR-MS). Concentrations in emissions from the bottom sediments of VOCs with the following mass–charge ratio (m/z) were analyzed: 57, 61, 63, 69, 75, 81, 83, 85, 87, 95, 97, 99, 101, 109, 111, 127, 129, 137, 149, and 157. The obtained data were analyzed by performing statistical tests and multivariate cluster and PCA analysis. The analysis shows that the lowest concentrations of VOCs were observed from bottom sediments in Lake Jeleń, which is subject to the lowest anthropopressure among the studied lakes. The analysis shows that the lowest concentrations of VOCs were observed from bottom sediments in Lake Jeleń, which is subject to lower anthropopressure among the studied lakes. With the help of cluster analysis, it was possible to collect data on the VOC concentrations into clusters, which resulted in demonstrating similarities between Łazienkowskie and Rychnowskie lakes—lakes connected by an isthmus, and the different characteristics of Lake Jeleń. PCA analysis leads to similar observations. The tested m/z VOCs can be identified using additional analytical methods.

Distribution of 137Cs specific activity in river sediments of the Barents Sea basin (Nenets Autonomous Okrug, Russian Arctic).

This article focuses on the study of the distribution of 137Cs in the bottom sediments of Arctic rivers of the Barents Sea basin (using the example of the Nenets Autonomous Okrug, Russian Arctic). This research is relevant due to the poorly studied region and the significant number of radiation-hazardous facilities in the Arctic zone of Russia, both those currently in operation and those that are "nuclear heritage sites". The study of 137Cs specific activity in bottom sediments was carried out in the period from 2020 to 2023 in the rivers Chizha, Nes, Vizhas, Oma, Pechora (river delta), as well as the rivers Kolva and Usa (first and second order tributaries, respectively, of the Pechora River). A total of 199 samples were collected. In addition to 137Cs specific activity, the samples were analysed for sediment particle size distribution, organic matter content, carbonate content and ash content. The 137Cs specific activity mainly ranged from the minimum detectable specific activity to 5.4 ± 0.8Bq·kg-1. In the Nes River basin (Kaninskaya tundra), the 137Cs content in bottom sediments reached 36.0 ± 3.2Bq·kg-1 (in the case of lake sediments) and 22.9 ± 3.7Bq·kg-1 (in the case of river sediments), values that are higher than those of the North-West of Russia. Considering the large area of the study area (Kaninskaya tundra, Pechora river delta, southern part of Bolshezemelskaya tundra) and the similarity of physical and chemical parameters of the studied rivers, it is possible to assume the existence of a zone of increased radionuclide content in the Nes river basin. This may be due to the runoff from the Nes River catchment area, its hydrological features, and the accumulation of 137Cs in the small fractions of bottom sediments. The results confirm the conclusions of previous soil studies in the Nes river basin. The main sources of elevated 137Cs content are global atmospheric deposition and the Chernobyl Nuclear Power Plant accident.

Effect of pH, Temperature, and Salinity Levels on Heavy Metal Fraction in Lake Sediments

Effect of pH, Temperature, and Salinity Levels on Heavy Metal Fraction in Lake Sediments

Survival strategies of aerobic methanotrophs under hypoxia in methanogenic lake sediments

BackgroundMicrobial methane oxidation, methanotrophy, plays a crucial role in mitigating the release of the potent greenhouse gas methane from aquatic systems. While aerobic methanotrophy is a well-established process in oxygen-rich environments, emerging evidence suggests their activity in hypoxic conditions. However, the adaptability of these methanotrophs to such environments has remained poorly understood. Here, we explored the genetic adaptability of aerobic methanotrophs to hypoxia in the methanogenic sediments of Lake Kinneret (LK). These LK methanogenic sediments, situated below the oxidic and sulfidic zones, were previously characterized by methane oxidation coupled with iron reduction via the involvement of aerobic methanotrophs.ResultsIn order to explore the adaptation of the methanotrophs to hypoxia, we conducted two experiments using LK sediments as inoculum: (i) an aerobic "classical" methanotrophic enrichment with ambient air employing DNA stable isotope probing (DNA-SIP) and (ii) hypoxic methanotrophic enrichment with repeated spiking of 1% oxygen. Analysis of 16S rRNA gene amplicons revealed the enrichment of Methylococcales methanotrophs, being up to a third of the enriched community. Methylobacter, Methylogaea, and Methylomonas were prominent in the aerobic experiment, while hypoxic conditions enriched primarily Methylomonas. Using metagenomics sequencing of DNA extracted from these experiments, we curated five Methylococcales metagenome-assembled genomes (MAGs) and evaluated the genetic basis for their survival in hypoxic environments. A comparative analysis with an additional 62 Methylococcales genomes from various environments highlighted several core genetic adaptations to hypoxia found in most examined Methylococcales genomes, including high-affinity cytochrome oxidases, oxygen-binding proteins, fermentation-based methane oxidation, motility, and glycogen use. We also found that some Methylococcales, including LK Methylococcales, may denitrify, while metals and humic substances may also serve as electron acceptors alternative to oxygen. Outer membrane multi-heme cytochromes and riboflavin were identified as potential mediators for the utilization of metals and humic material. These diverse mechanisms suggest the ability of methanotrophs to thrive in ecological niches previously thought inhospitable for their growth.ConclusionsOur study sheds light on the ability of enriched Methylococcales methanotrophs from methanogenic LK sediments to survive under hypoxia. Genomic analysis revealed a spectrum of genetic capabilities, potentially enabling these methanotrophs to function. The identified mechanisms, such as those enabling the use of alternative electron acceptors, expand our understanding of methanotroph resilience in diverse ecological settings. These findings contribute to the broader knowledge of microbial methane oxidation and have implications for understanding and potential contribution methanotrophs may have in mitigating methane emissions in various environmental conditions.

Late Pleistocene to Holocene vegetation changes in southeastern Patagonia (49° S): landscape changes related to disturbances

ABSTRACTSoutheastern Patagonia's (49° S) post‐glacial history inferred from high Andean lake sediments provides new insights regarding Late Pleistocene and Holocene vegetation dynamics at the eastern margin of the Southern Patagonian Icefield. The fossil records of pollen, charcoal and geochemical data from tephra layers from Laguna Chiquita and Laguna Gemelas Este were analysed to reveal past landscape dynamics related to vegetation changes, fire and volcanic events from ca. 15 200 cal a bp to the present. Nothofagus forest expanded over shrubland communities sometime between 15 200 and 4600 cal a bp, along with at least three disturbance sources related to the volcanic eruptions of Lautaro, Aguilera and Hudson, important local fire episodes, and neoglacial advances. Major charcoal deposition reveals moderate fire activity during the Late Pleistocene related to an open landscape characterised by a grass/shrub steppe. Local glacier advances may have affected the Laguna Gemelas Este sedimentation. Tephra deposition events do not correlate to vegetation changes inferred from the Laguna Gemelas Este and Laguna Chiquita pollen records. Late Holocene eastern Andean forest changes and fire activity at 49° S match other southern palaeoenvironmental records (50–52° S) suggesting that changes in the Southern Westerly Wind latitudinal position and intensity drove major palaeovegetation and fire dynamics before the European settlement. In the last centuries, fire and vegetation changes have been closely related to an increase in local ignition sources and the introduction of alien species.

Microplastics and their interaction with microorganisms in Bosten Lake sediment

Microplastics (MPs), discovered in oceans, lakes, and rivers, can infiltrate the food chain through ingestion by organisms, potentially posing health risks. Our research is the first to study the composition and distribution of MPs in Bosten Lake's sediment. In May, the average abundance of MPs was 0.95±0.72 particles per 10 grams, and in October, it was 0.90±0.61 particles per 10 grams. Bohu Town had the highest MP abundance, with 1.75±0.35 particles per 10 grams in spring and 2±0 particles per 10 grams in autumn. In May, 53% of the MPs were transparent, while in October, black MPs constituted 58%. The predominant morphology was fibrous, accounting for 61% of the total. MPs in the size range of 0.2-1 mm made up 91% and 66% of the total in May and October, respectively. The most common types of MPs in May were polyethylene terephthalate (PET) at 40% and polyethylene (PE) at 26%. In October, PET was the most prevalent at 71%, followed by poly(ether-ether-ketone)(PEEK) at 11%. Certain microbial taxa, such as Actinobacteriota, Pseudomonas, and Vicinamibacteraceae, associated with MP degradation or complex carbon chain breakdown, were notably enriched in sediment areas with high MP concentrations. A significant positive correlation was observed between the abundance of MPs in sediments and Actinobacteriota. Additionally, the abundance of Thiobacillus, Ca.competibacter, and other bacteria involved in soil element cycling showed a significant positive correlation with the organic matter content in the sediments. Anaerobic bacteria like Thermoanaerobacterium displayed a significant positive correlation with water depth. Our study reveals the presence, composition, and distribution of MPs in Bosten Lake's sediments, shedding light on their potential ecological impact.

A new approach to counting fossil and modern pollen grains: The orderly count

Palynology, the study of pollen and spores, plays a crucial role in various scientific disciplines, including earth sciences (paleovegetation and paleoclimatology), botany, allergy, archaeology, forensic sciencs and cosmetics. This study delves into the critical question in fossil pollen analysis studies: the minimum count of pollen grains required for accurate estimation of vegetation composition. Various statistical methods have been proposed over the years to address this question. Our research introduces an alternative technique, the orderly count, tailored to the nature of palynological analysis. We apply this method to diverse sediment catchments, including peat bogs, marine and lake sediments, from different geographical locations. Additionally, we revisit the reliability coefficients and propose adjustments for more accurate results. Our findings suggest that relying on statistical methods without considering the specific characteristics of palynological data may lead to low reliability. We advocate for the integration of dissimilarity criteria and the orderly count in sample size assessments for enhanced accuracy in palynological analyses. Our study emphasizes the importance of choosing appropriate methodologies aligned with the unique aspects of palynology to ensure robust and reliable results.

Sedimentary biomarkers and bone specimens reveal a history of prehistoric occupation on Somerset Island (Arctic Canada).

Archaeological studies of pre-historic Arctic cultures are often limited to artefacts and architecture; such records may be incomplete and often do not provide a continuous record of past occupation. Here, we used lake sediment archives to supplement archaeological evidence to explore the history of Thule and Dorset populations on Somerset Island, Nunavut (Canada). We examined biomarkers in dated sediment cores from two ponds adjacent to abandoned Thule settlements (PaJs-3 and PaJs-13) and compared these to sediment cores from two ponds without past human occupation. Coprostanol and epicoprostanol, δ15N measurements, sedimentary chlorophyll a and the ratio of diatom valves to chrysophyte cysts were elevated in the dated sediment profiles at both sites during Thule and Dorset occupations. Periods of pronounced human impact during the Thule occupation of the site were corroborated by 14C-dated caribou bones found at both sites that identified intense caribou hunting between ca 1185 and 1510 CE. Notably, these sediment core data show evidence of the Dorset occupation from ca 200 to 500 CE at sites where archaeological evidence was heretofore lacking. We highlight the utility of lake sediments in assisting archaeological studies to better establish the timings, peak occupations and even lifestyle practices of the Dorset and Thule Arctic peoples.

Watershed hydrology mediates the recovery of an arsenic impacted subarctic landscape

A holistic understanding of the chemical recovery of lakes from arsenic (As) pollution requires consideration of within-lake biogeochemical cycling of As and processes occurring in the surrounding catchment. This study used a watershed mass balance approach, complemented by experimental sediment incubations, to assess the mobility and transport of As within a subarctic watershed (155 km2) impacted by more than 60 years of atmospheric mining emissions. The period of record spanned a transition from drought to high streamflow between September 2017 and September 2019, which yielded insights into the interacting effects of hydrology and within-lake biogeochemical cycling of As. Internal loading of As from contaminated lake sediments (25 – 46 kg As year-1) and contributions from terrestrial sources (16 – 56 kg As yr-1) continue to negatively impact lake water quality (19 – 144 μg As L-1), but the relative importance of these loads varies seasonally and inter-annually in response to changing hydrological conditions. Wet conditions resulted in greater transport of As from terrestrial reservoirs and upstream areas, shorter lake water retention time, and increased the downstream export of As. During dry periods, the lake was disconnected from the surrounding watershed resulting in limited terrestrial contributions and longer lake water residence time, which delayed recovery due to the greater relative influence of internal loading from contaminated sediments. This study highlights that changing hydroclimatic regimes will alter trajectories of chemical recovery for arsenic impacted lakes through the coupling of within-lake and watershed transport processes.

Arsenic distribution characteristics and release mechanisms in aquaculture lake sediments

It is well known that aquaculture can alter the microenvironments of lakes at sediment-water interface (SWI). However, the main mechanisms underlying the effects of aquaculture activities on arsenic (As) transformations are still unclear. In this context, the present study aims to investigate the variations in the sediment As contents in Yangcheng Lake, as well as to assess its chemical transformations, release fluxes, and release mechanisms. The results showed substantial spatial differences in the dissolved As concentrations in the sediment pore water. The As release fluxes at the SWI ranged from 1.32 to 112.09μg/L, with an average value of 33.68μg/L. In addition, the highest As fluxes were observed in the aquaculture areas. The transformation of crystalline hydrous Fe oxide-bound As to adsorbed-As in the aquaculture lake sediments increased the ability of As release. The Partial least squares path modeling results demonstrated the great contributions of organic matter (OM) to the As transformations by influencing the sediment microbial communities and Fe/Mn minerals. The changes in the As fractionation and competing adsorption increased the dissolved As concentrations in the 0-10mm surface sediment. Non-specifically and specifically adsorbed As were the major sources of dissolved As in the sediments. Specifically, microbial reduction of As[V] and dissolution of Fe oxides increased the dissolved As concentrations at the SWI (20 to -20 mm). The results of the current study highlight the positive enhancement effects of aquaculture on As release from sediments. Environmental implicationsUnderstanding the transport and transformation patterns of As in aquaculture lake sediments is crucial for ensuring the protection and safety of aquaculture lakes, as well as for the effective management of water environments. This study showed higher dissolved As concentrations and release fluxes in aquaculture lakes than those in a non-aquaculture lake. Sediments with high total organic carbon (TOC) and P contens promoted the transformation of Fe-bound As to adsorbed-As and dissolved As. In addition, the microbial reduction of As[V] to As[III] played a key role in the As release process. This study highlights the high bioavailability of As in aquaculture lake sediments. Hence, it is crucial to devote great attention to the transformation process of released As from these sediments.

Heavy metal toxicity and its human health assessment: A preliminary study from the Perumal Lake sediments, Tamil Nadu, India

The current investigation manifests the heavy metal toxicity and its human health assessment to appraise the environmental deterioration of the sediments within the Perumal Lake, Tamil Nadu, India. Five surface samples were collected from the Perumal Lake in 2023, which undergoes the selective perception of the granulometric analysis, implying supremacy of the clay content and limited sand and silt contents. The organic matter indicates the higher input of waste disposal, and the CaCO3 illustrates the existence of shell fragments in the lake environments. Noteworthy results of the heavy metal concentration as arranged in the devaluation order as Zn > Cu > Fe > Cr > Ni > Mn > Pb > Co > Cd. Followed by the heavy metal concentration, the environmental contamination indices such as Igeo denote that except for Cd metal, other heavy metals indicate moderate to extreme pollution status. The Enrichment Factor (Ef) illustrates Fe, Co, Cd, Zn, Cu, Ni, and Pb, highlighting no metal enrichment. In contrast, Mn and Cr reveal low metal enrichments, and the Cf reveals all the heavy metals, which argues for low to high contamination ranges. The Cd and the mCd are categorized as very high, and PERI underscores the low-risk category. The Hazard Index (HI) of the non-carcinogenic category and carcinogenic demonstrates that children and adults are primarily at risk of ingestion. At the same time, the dermal pathway indicates low jeopardy to children and adults and no risk to humans. The Heavy Metal Toxicity Load (HMTL) poses the sample location three registers a significant accumulation of toxic contagion proposed to remove from the sediments. Realm of heavy metal toxicity and its human health assessment underscores for researchers in environmental quality determination, and the strategies discussed such as phytoremediation, in-situ capping, and biotechnological techniques, may be helpful in evaluation and implement remediation methods of pollution in aquatic environments.

The oldest ‘millipede’-plant association? Age, paleoenvironments and sources of the Silurian lake sediments at Kerrera, Argyll and Bute, Scotland

ABSTRACT On Kerrera island, poorly dated braided stream conglomerates and sandstones are interbedded with finer lake siltstones and shales, with land plants, fish and arthropods, including ‘millipedes’. Crystallization dates for minerals in the overlying Lorne Plateau Lave are older than 425 Ma (Upper Silurian Ludfordian), yet palynological data are supposed to give an early Devonian (419 Ma) age. Detrital zircon U/Pb dates of sediments enclosing the fish beds give two clusters of dates, one Proterozoic and the other Silurian. The most concordant youngest single grain date of 427.0 ± 4.5 Ma (0% discordance) gives the maximum age of the Fish beds and is consistent that the radiometric dates of the overlying rapidly erupted lavas. This maximum age is slightly older than that of the ‘millipede’-bearing Cowie fish bed with maximum age of 414.3 ± 7.1 Ma, which make the Kerrera ‘millipedes’ the oldest so far dated.

Characterizing the Stoichiometry of Individual Metal Sulfide and Phosphate Colloids in Soils, Sediments, and Industrial Processes by Inductively Coupled Plasma Time-of-Flight Mass Spectrometry.

Size and purity of metal phosphate and metal sulfide colloids can control the solubility, persistence, and bioavailability of metals in environmental systems. Despite their importance, methods for detecting and characterizing the diversity in the elemental composition of these colloids in complex matrices are missing. Here, we develop a single-particle inductively coupled plasma time-of-flight mass spectrometry (sp-icpTOF-MS) approach to characterize the elemental compositions of individual metal phosphate and sulfide colloids extracted from complex matrices. The stoichiometry was accurately determined for particles of known composition with an equivalent spherical diameter of ≥∼200 nm. Assisted by machine learning (ML), the new method could distinguish particles of the copper sulfides covellite (CuS), chalcocite (Cu2S), and chalcopyrite particles (CuFeS2) with 75% (for Cu2S) to 99% (for CuFeS2) accuracy. Application of the sp-icpTOF-MS method to particles recovered from natural samples revealed that iron sulfide (FeS) particles in lake sediment contained ∼4% copper and zinc impurities, whereas pure pyrite (FeS2) was identified in hydraulic fracturing wastewater and confirmed by selected area electron diffraction. Colloidal mercury in an offshore marine sediment was present as pure mercury sulfide (HgS), whereas geogenic HgS recovered from an industrial process contained ∼0.08 wt % silver per Hg, enabling source apportionment of these colloids using ML. X-ray absorption spectroscopy confirmed that Hg was predominantly present as metacinnabar (β-HgS) in the industrial process sample. The determination of impurities in individual colloids, such as zinc and copper in FeS, and silver in HgS may enable improved assessment of their origin, reactivity, and bioavailability potential.

The Forms of Phosphorus in Sediments of Large Lakes (Poyang Lake) and Its Impact on Endogenous Release

The Forms of Phosphorus in Sediments of Large Lakes (Poyang Lake) and Its Impact on Endogenous Release

Impacts of conventional and biodegradable microplastics on greenhouse gas emissions and microbial communities in lake sediment under diverse aging methods

Microplastics (MPs) are crucial in regulating microbial communities, thereby influencing greenhouse gas (GHG) emissions in freshwater ecosystems. MPs’ presence in lake sediment has been confirmed to be aged, necessitating a reassessment of their influence on GHG emissions. This study aims to investigate the impacts of MPs with various aging methods on organic carbon decomposition and GHG release in urban lake sediments. During the four-week duration of the microcosm experiment, the conventional polyethylene (PE) and biodegradable Poly (butylene-adipate-co-terephthalate) (PBAT) MPs were subjected to ultraviolet (UV) radiation, advanced oxidation processes (AOPs) and biological aging methods to investigate their impacts on carbon dioxide (CO2) and methane (CH4) emissions from lake sediment. Compared to pristine PE, pristine PBAT significantly exacerbated the detrimental impact on CO2 and CH4 emissions by 21.61% and 43.13%, respectively, mainly due to 10% increase in dissolved organic carbon (DOC) and 22.65% increase in microbial biomass carbon (MBC). The surface morphology and functional groups of MPs were changed obviously after aging, thereby influencing the decomposition potential of organic carbon and the capacity of microbial reproduction. The aging process of PBAT reduced the available nutrients for microbial activity due to its rapid degradation, leading to a pronounced inhibitory effect on microbial respiration. Besides, MPs aging altered the microbial relative abundance of phyla Firmicutes, Actinobacteria, as well as families Lutispora and Azospirillaceae, thus exerting influence on capacity and anaerobic proportion of microbial respiration.

Half of the soil erosion in the Alps during the Holocene is explained by transient erosion crises as a consequence of rapid human land clearing

Human land use changes have altered soil erosion for millennia with extensive consequences on terrestrial and aquatic ecosystems as well as on biogeochemical cycles along the land-ocean continuum. Despite their great importance, past erosion trends have high uncertainties limiting quantitative estimates of long-term erosion dynamics. Here, we applied a new approach combining well-dated paleo-records of soil erosion from lake sediments and a spatially distributed semi-empirical model to simulate annual soil erosion in six lake watershed systems in the Northwestern Alps during the Holocene. Progressive and abrupt changes in soil erosion are detected in the six watersheds. Progressive erosion explains most of the soil exports observed during the Early to Mid-Holocene period (from 11,700 to 3000 cal. yr. BP), while transient erosion crises (i.e., periods of abrupt increase in the erosion rates spanning approximately 1000 ± 500 years) led to massive soil losses during the Late-Holocene period (from 3000 to 1000 cal. yr. BP). Our coupled approach of proxy-model reconstruction shows that the transient erosion crises represent the half of the total soil erosion exports during the Holocene. These estimates defy current representations of large-scale soil erosion during the Holocene that do not consider transient erosion crises, hence potentially underestimating the anthropogenic perturbation of lateral fluxes and fate along the land-ocean continuum. Our results further suggest that erosion and/or land cover proxies need to be consistently integrated into model approaches when attempting to estimate past variations in mass exports from terrestrial to aquatic ecosystems over centennial to millennial timescales.

Spatial distribution of potentially toxic elements pollution and ecotoxicological risk of sediments in the high-altitude lakes ecosystem

Sediments are a sink and source for potentially toxic elements (PTE) contamination in aquatic systems. Among aquatic systems, lakes ecosystem play a significant role in managing, maintaining, and supplying water for several environmental and ecological services. The lake has a slow rate of water inflowing contaminant circulation, building up higher contaminants and hence making it most vulnerable. This study focused on and explored the sediments for PTE concentrations in the high-altitude lakes ecosystem of Swat Valley, northern Pakistan. The sediment samples were collected and analyzed for PTE concentrations. Among PTE, iron (Fe) showed an uppermost level of 1024 ± 94.2 mg/kg in Izmis Lake sediments, while cadmium (Cd) noted with a lowermost of 0.30 ± 0.1 mg/kg in Kandol Lake. PTE concentrations in the high-altitude lakes were noted to be lower than the sediment quality guidelines (SQGs), except for copper (Cu) and cadmium (Cd). The concentrations of PTE were utilized to calculate pollution factors and ecotoxicological risks. The contamination factor (Cf) of sediments in high-altitude lakes observed low to moderate contamination levels and ecotoxicological risks. Among high-altitude lakes, the Izmis Lake showed maximum Cf, pollution load index, and risk values for most of PTE than others. Statistical analyses revealed a significant correlation for most PTE and noted geogenic sources of contamination in sediments of high-altitude lakes.

Paleoseismic Investigation of the Thousand Springs Fault, Northwestern Basin and Range, Oregon

ABSTRACT Earthquake recurrence intervals, surface-rupture extents, and interactions between faults provide insight into how faults behave and are critical for seismic hazard mitigation and earthquake forecasting. Investigating the paleoseismology of spatially related faults can reveal strain distribution and whether faults rupture as a system or independently. Summer Lake basin, a graben in the northwestern Basin and Range with four active faults (three of which have prior paleoseismic investigations), provides an opportunity to investigate fault interactions. To expand the paleoseismic record, two trenches were excavated across the previously undocumented Thousand Springs fault, exposing a normal fault zone that offsets a sequence of deep- to shallow-water lake sediments, sand dunes containing reworked Mazama ash, and other Cascades-sourced tephra. Tephra units were correlated to known units by their physical characteristics, stratigraphic sequence, glass chemistry, and two new radiocarbon dates from the uppermost lake sediments. Using trench exposures, measured vertical separations through auguring, colluvial wedges, and extrapolated offsets based on a constant sedimentation rate, we identified at least five surface-rupturing earthquakes with a total offset of 3.4 + 2/−1 m in the past ∼65 ka. The oldest event (EH5) occurred at 63.8 ± 1.5 ka, event horizon 4 at 36.2 ± 12.7 ka (which could be more than one event), and event horizon 3 at 24.6 ± 0.3 ka. Event horizon 2, a warping event at our site, is likely more than one event and occurred between 7.5 and 10 ka; and the most recent event (EH1+), most likely more than one event, occurred between 3.3 and 7.7 ka. Several events correlate, within error, with events on other faults in the Summer Lake basin, suggesting that (1) the faults generally rupture together as a system, (2) the most recent earthquake may have ruptured all faults in the region, and (3) fault rupture is influenced by the rapid regression of Lake Chewaucan (∼13 ka).

Identification of Bioactive Compounds of Streptomyces spp. Isolated from Qom Lake Sediments and Evaluation of its Antimicrobial Activity against Pseudomonas aeruginosa

Background: Marine sediments are rich sources for isolating active secondary metabolites from microorganisms. Among the microorganisms, Actinomycetes are highly important due to the production of various chemical compounds in a wide range of biological activities, such as antibacterial activity. Streptomyces is the most important genera in the family of Actinomycetes. As a member of this group, it has great potential in the production of secondary metabolites such as antibiotics, enzymes, herbicides, anti-carcinogenic, and other useful compounds. Objective: This study aims to identify bioactive compounds of Streptomyces isolated from sediments of the Salt Lake of Qom and to study their antimicrobial properties against standard strains of Pseudomonas aeruginosa. Methods: In this study, 20 samples were collected from a depth of 5 to 15-20 cm of sediment in the Salt Lake of Qom. Pure cultivations were then provided from these samples. This study used starch casein agar (SCA) to isolate streptomyces, and 35 Streptomyces were isolated. The disc diffusion method was used to explore the antimicrobial properties of Streptomyces against clinical strains of Pseudomonas aeruginosa and strains standard of Pseudomonas aeruginosa PTCC 1310. Results: Seven strains, including SCA3 SCB1, SCB4, SCB8, SCC15, SCC18, and SCC28 strains, had antimicrobial properties. In this study, the results show that SCC15 with the halo diameter of 17, 17, 15, and 19 contains the best antibacterial properties against clinical strains 1, 2 and 3 of Pseudomonas aeruginosa and Pseudomonas aeruginosa PTCC 1310. among the 16 peaks observed by GC/MS to identify bioactive compounds of Streptomyces, it was found that Bis (2-ethyl hexyl) phthalate, with 69.06 percent, had the highest peak production, which reflects the importance of phthalates in microbial activities. Conclusion: According to the results, the Salt Lake of Qom was one of the sources of Streptomyces. In addition, the isolated Streptomyces had antimicrobial properties against Pseudomonas aeruginosa isolates. It was also found that phthalate was the most bioactive substance of Streptomyces isolated.