Stream Sediment Research Articles

Seasonal patterns in sediment nitrification rates and their linkages to ammonium cycling in three agricultural streams

Nitrification, or the microbial transformation of ammonium (NH4+–N) to nitrate, is influenced by NH4+–N and dissolved oxygen availability, water temperature, and carbon-to-nitrogen ratios. Open-canopy agricultural streams receive excess inorganic nitrogen (N) from the surrounding landscape and the mineralization of organic-rich sediments, and the form and timing of these N inputs varies throughout the year. Compared to forested streams, the seasonality of nitrification rates in agricultural streams are not well documented. We conducted nitrification assays on stream sediments to estimate seasonal rates in three agricultural streams from summer 2020 to spring 2021. We documented seasonal variation in nitrification rates and identified changes in environmental controls [e.g., stream temperature, NH4+–N and dissolved organic carbon (DOC) availability, chlorophyll-a]. Nitrification rates were highest in spring (54.4 ± 12.7 mg N m−2 d−1; p = 0.02), coinciding with elevated NH4+–N and higher stream temperatures relative to winter (p < 0.001). Rates were lowest in autumn (19.9 ± 3.5 mg N m−2 d−1) when organic carbon concentrations peaked (17.2 ± 10.3 mg C L−1; p = 0.01). Algal senescence in autumn may allow heterotrophs to outcompete nitrifiers for NH4+–N. However, partial least square regression analyses indicated that sediment organic matter (as %OM) is an important positive predictor of nitrification, suggesting carbon can be an indirect positive control on nitrification. In the context of previous studies, agricultural streams had elevated NH4+–N concentrations, but nitrification rates were comparable to those in less impacted systems. Although complex interactions exist among rates and drivers, rates from this study help expand documentation of nitrification in agricultural streams, and provide insight into temporal variation and dominant controls.

Temperature alters bacterial community structure in sediment of mountain stream

Temperature and nutrients are known as crucial drivers for the variations of bacterial community structure and functions in oceans and lakes. However, their significance and mechanisms in influencing the bacterial community structure and function in mountain stream remain unclear. In this study, we investigated the spatiotemporal patterns of the bacterial communities and the main environmental factors in the Taizicheng River, a high-latitude mountainous stream, to reveal the main driving factors for sedimental bacterial communities. Our findings identified that the phyla Acidobacteriota and Bacteroidota served as the strong discriminant for sedimental bacterial community in the non-freezing and freezing periods, respectively. In contrast, no significant difference was detected in bacterial functional composition. Mantel test and Redundancy analysis showed that temperature and nutrients played significant roles in determining the bacterial community structure and temperature critically influenced the bacterial metabolic processes. The results of partial least squares path model demonstrated that temperature affected the bacterial community structure in both directly (43.70%) and indirectly pathways (41.10%) by affecting the sediment parameters. However, the functional composition was not significantly affected by temperature and nutrients. Our results highlight that the change of temperature can significantly alters the structure of bacterial communities rather than functional composition and provides new insights into the response mechanisms of bacterial communities to environmental factors which contributes to the deep understanding of the driving factors as well as the protection strategies for microbial communities in mountain stream and aquatic ecosystem.

Methane and sulfide sulfur in water and bottom sediments of streams of the steppe zone of the European part of Russia

The results of long-term studies of the conjugate distribution of concentrations of methane (CH 4 ) and sulfide sulfur (S sulfide ) in bottom sediments of streams of the steppe zone of the European part of Russia are analyzed. In addition to CH 4 and S sulfide , Eh and pH values, humidity and density were determined in various sediment horizons; CH 4 , dry residue and pH values were determined in water. Concentrations of CH 4 in the water of watercourses vary from 0.1 to 2007.0 µl/l (median 24.3 µl/l), with the largest number of values (72 %) in the range 10.1–100.0 µl/l. The concentrations of CH 4 and Ssulfide in the bottom sediments of watercourses are quite high and vary, respectively, from 0.01 to 51.0 µg/g of wet sediment (median 1.35 µg/g) and from 0.001 to 4.50 mg/g of wet sediment (median 0.813 mg/g). Usually, there is an increase in CH 4 and S sulfide from the surface layer to the subsurface horizons, after which their concentrations decrease. The difference between the distribution of sulfides and the distribution of CH 4 is the more frequent occurrence of maximum concentrations of sulfides in less deep sediment horizons. Seasonal changes in the distribution of CH 4 and S sulfide along the vertical of sediments were recorded not only in terms of their concentrations, but also in the location of maximum and minimum values. There is a weak direct relationship between the concentrations of CH 4 and S sulfide , which indicates synchronous processes of formation of these gases in separate layers of sediments of the studied watercourses. The direct relationship established between the concentrations of CH 4 in water and the 0–2 cm layer of bottom sediments indicates sediments as an important source of CH 4 entering water and its emission into the atmosphere.

Instream sediment mining in Chilean rivers: review and management proposal

The effects of instream sediment mining have been widely described in the literature. Although this activity has been strictly regulated in some countries, other countries still register an increasing number of sediment mining extractions, as is the case of Chile. The goal of this work is to study the current state of instream gravel mining in Chile, describing the current legislation in the country. The results showed an increasing trend in the number of approved projects, and although present in the whole country, a large proportion were located in the central and southern regions, led by Ñuble Region. The regulation of mining activities in the country is currently managed and evaluated by the municipal government where the extraction is located, after an evaluation from the Department of River Works, which has led to an over-extraction situation in some rivers. Within this context, there has been a raise in the Chilean society awareness regarding environmental issues, accompanied by the identification of the main negative impacts of sediment mining from fluvial systems. Recently, the Chilean government has been discussing a new instream sediment mining law, with the aim to standarise the regulations and incorporating a socio-environmental vision in the evaluation of these projects.

Spatial Distribution, Contamination Characteristics and Eco-Risk Assessment of Toxic Metals in Stream Sediments of Njombe-Penja Banana Plain, Cameroon Volcanic Line

Spatial Distribution, Contamination Characteristics and Eco-Risk Assessment of Toxic Metals in Stream Sediments of Njombe-Penja Banana Plain, Cameroon Volcanic Line

Geochemical distribution of elements in the environmental media from the surroundings of open pit areas

The results of geochemical investigations - carried out within the framework of the European project LIFE IP RESTART - in the degraded areas of the Kopriva (deposit of natural stone-limestone) and Lipovški vrh (deposit of limestone for industrial purposes) open pits are presented. There test sites of the installation of secondary raw materials (a mixture of recycled materials and mineral raw materials) with the aim of revitalizing degraded surfaces are planned. The main goal of this study is to define the baseline geochemical distribution of elements in environmental materials (rocks, soil, stream sediment and surface water) for the purpose of monitoring the potential environmental impacts of installed secondary raw materials. In rocks Ca content predominates due to the geological setting (predominantly limestone) of the studied areas. According to the legislative guidelines for soil, exceedances have been found for Pb in one sample (origin can be natural or anthropogenic) and Ni in two samples (presumably natural origin) from the area of Kopriva. In the area of Lipovški vrh in the stream Suhi Potok, higher contents of Mg, Na, Sr, Ca, Mn and S occur in the downstream sediment compared to upstream sediment. It is assumed higher contents occur due to anthropogenic contribution of carbonate material along the stream (washing of materials from nearby open pit and road). In the surface water of Suhi Potok, higher concentrations of S, Sr, B, U and Zn were determined. However, the concentrations did not exceed the legislative guidelines.

Spatial distributions, potential sources, and ecological risks of heavy metals in stream sediments in Zambia

The ecological risk assessment and source identification of heavy metals (HMs) are significant for resource utilization and food security. This study aims to assess the spatial distributions, potential sources, and ecological risks of HMs in stream sediments in Zambia. Using 735 samples collected from stream sediments across the country and methods such as inductively coupled plasma mass spectrometry (ICP-MS), atomic fluorescence spectrometry (AFS), and X-ray fluorescence spectrometry (XRFS), this study determined the concentrations of the seven HMs, i.e., arsenic (As), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), and zinc (Zn). The spatial distributions of these HMs were determined using a Geographic Information System (GIS), and their ecological risks were accessed based on the analytical results of their potential sources. Additionally, this study explored the relationships between mining activities and regions with high heavy metal (HM) concentrations based on the statistical analysis of the HM concentrations and geology of the study area. The results indicate the stream sediments in Zambia exhibit average As, Cr, Cu, Hg, Ni, Pb, and Zn concentrations of 1.49 × 10−6, 19.34 × 10−6, 12.12 × 10−6, 12.70 × 10−9, 7.13 × 10−6, 12.52 × 10−6, and 16.30 × 10−6, respectively. The analytical results of the geoaccumulation index (Igeo) and potential ecological risk index (PERI) reveal the presence of relatively high As and Cu concentrations, especially in Copperbelt and North-Western provinces and areas surrounding Lusaka—the capital of Zambia. The HM contamination in stream sediments in Zambia is primarily caused by Cu and gold (Au) mining. This study exemplifies how to determine potential sources and ecological risks of HMs in stream sediments, holding important implications for nation-scale environmental contamination prevention and land utilization planning.

The sub-watershed extraction and application of geochemical anomalies: A case study of the geochemical survey data of 1:50000 stream sediments in the Haoteluowa area of the Eastern Kunlun Orogeny

The sub-watershed extraction and application of geochemical anomalies: A case study of the geochemical survey data of 1:50000 stream sediments in the Haoteluowa area of the Eastern Kunlun Orogeny

Heavy-Fluid Separation of the North Caka Mountain Stream Sediment and its Significance to Search Pegmatite Lithium Ore

Heavy-Fluid Separation of the North Caka Mountain Stream Sediment and its Significance to Search Pegmatite Lithium Ore

Optimising sub-metre resolution 3D geomorphic change detection over large areas using multitemporal airborne laser scanning with Sentinel-1 InSAR and Sentinel-2 optical observations

Airborne laser scanning (ALS) is widely used in studies of Earth surface change and has potential to inform targeted landscape remediation over large areas. Leveraging this capability requires geomorphic change detection methods that exploit the full 3D information contained in ALS point clouds but remains challenging over large areas (i.e., > 10 km2). We developed a methodology for geomorphic change detection over large areas using multitemporal ALS in a multiscale model-to-model cloud comparison (M3C2) framework adapted for volumetric estimation. Time series Sentinel-2 optical observations were used to isolate persistently-bare areas as candidate sites to co-register the ALS point clouds. Geomorphic stability of those sites was determined from coherence change detection using time series Sentinel-1 InSAR, thereby ensuring only geomorphically-stable sites were used for co-registration. Results showed the Sentinel-based co-registration produced a closer vertical alignment (0.00 ± 0.09 m) between ALS point clouds over stable parts of the landscape, while co-registration using an iterative closest-point algorithm contained bias (0.07 ± 0.10 m). The methodology was used to estimate annual sediment yield for a semi-arid catchment in northeastern Australia and results were compared with long-term field-based stream sediment monitoring. The ALS-based geomorphic change detection estimated 2.58 ± 0.54 t·ha−1·a−1 sediment yield and stream sediment monitoring estimated 1.40 t·ha−1·a−1. These similar estimates indicate multitemporal ALS can produce realistic whole-of-catchment sediment yield estimates in ungauged catchments (i.e., with no stream sediment monitoring) and improves the spatial detail of those estimates. Accurately detecting geomorphic change from multitemporal ALS also required a strategy to manage vegetation-related error due to misclassification of ALS point clouds. Combined identification of fine-scale erosion processes and reliable estimation of catchment-scale erosion rates indicates the proposed methodology provides a valuable tool for planning landscape remediation over large areas.

Riverine Cu-distribution in sediments of the Jaba-Kawerong river system 30 years after cease of mining at Panguna/Bougainville

The investigation of surface and river sediments over 30 years after the cease of large scale Cu and Au mining operation at Panguna (Bougainville) shows the impact of mining and tailings disposal on the associated riverine environment. While Zn, Pb and Cd have elevated concentrations in the former mining area and are low (< 100, < 28, < 1 mg/kg, respectively) in sediment of the Jaba-Kawerong river system, Cu represents the dominant environmental metal emission. Sediments of active streams and overbank deposits range between 1000 and 3000 mg/kg Cu. Most samples exceed freshwater sediment or soil quality guideline values, indicating the probability of toxic effects on sediment dwelling or aquatic organisms and ecological or health risks associated to agricultural use of the former mining area and floodplains. Copper in surface and river sediments is associated to bornite, chalcopyrite and chloritized biotite of the primary Panguna ore mineral assemblage. This attests to ongoing remobilization of sediment and/or reflects mobilization of additional Cu bearing material from the waste rock dump of the Panguna mine. Copper in surface and river sediments is also contained in secondary Cu-phases such as covellite as well as hydrated basic Cu-sulfates, which formed under locally variable redox conditions. Fe-oxihydroxides, occurring in variable abundance as reflected by Fe concentrations between 18,200 and 379,000 mg/kg (Mn 145–3086 mg/kg), can be identified as further Cu-carriers, taking up the metal from the aqueous phase in the sedimentary pore space. Mine derived input of Cu bearing minerals is confined to the sedimentary body of the Jaba-Kawerong river system. The diversity of Cu bearing phases with different environmental and processing properties sets constraints on re-processing sediments as secondary Cu-ores or re-using of sediments as building material.

Geochemical constraints on weathering and provenance of stream sediments from Bat Xat, northwestern Vietnam

The stream sediment samples collected from the Bat Xat district in Vietnam have been studied to establish their geochemical characteristics, provenance, weathering intensity, and climate. This comprehensive investigation included major, trace, and rare earth elements (REEs). The sediments were classified as greywacke, lithicarenite, and arkose, denoting compositionally immature deposits. The sediments exhibited moderate chemical weathering in the source domain, with a CIA average value of 67.01, PIA of 73.58, and ICV of 1.05. This suggests a depositional environment influenced by humid climatic conditions attributed to the attenuation of the Indian summer monsoon. The trace element and REE geochemistry of the Bat Xat sediments symbolize their characteristic signatures, with REE patterns mirroring those of their origins. The initial source materials are primarily associated with felsic rocks, with a smaller contribution from sedimentary and metamorphosed sedimentary rocks in the study area. Geochemical characteristics are large fluctuations in Eu/Eu∗ values and high (Gd/Yb)N ratios. We assume that Bat Xat sediments originated from the exhumated Archean crystalline basement or mixed rocks of the Archean component.

A synthesis of the National-scale Geochemical Survey in the last 50 years in Brazil

At the end of the 19th century, classical geochemistry arrived in Brazil through Henri Gorceix, being primarily used in his studies of mineralogy and petrology. Meanwhile, exploration geochemical arrives later, in the mid-20th century. But it was only in the late 1960s that systematic survey at the national level began, starting with the creation of CPRM - Geological Service of Brazil, culminating in over 50 years of uninterrupted activities, providing coverage of the entire country at various scales: global (7.3%), national (6.2%), regional (22.7%), and local (2.3%). Throughout this period, 681 projects were carried out and a variety of sample matrices were collected, such as stream sediment (226,792), soil (122,202), heavy-mineral pan concentrate (107,959), rock (56,807), among others (8,258), totaling 522,018 samples so far. All this collection has been progressively recovered, compiled, and organized into a robust public database (open access), developed by CPRM - Geological Service of Brazil. More recently, high-density geochemical surveys were conducted in partnership with the China Geological Survey with the aim of comparing analytical and sampling methodologies. For the future (until 2050), two main actions are planned: 1) an expectation of an increase in the coverage of high-density prospecting surveys, ranging from 951,386 km² (restrictive scenario: 11.2% of Brazilian territory) to 2,204,778 km² (favorable scenario: 25.9% of Brazilian territory); 2) a forecast of Brazil's participation in the Global Geochemical Baselines Program, where sampling will be subdivided by regions – North (736), Central-West (225), Northeast (305), and South-Southeast (343) – totaling 1,609 sampling cells.

Novel Photoelectron-Assisted Microbial Reduction of Arsenate Driven by Photosensitive Dissolved Organic Matter in Mine Stream Sediments.

The microbial reduction of arsenate (As(V)) significantly contributes to arsenic migration in mine stream sediment, primarily driven by heterotrophic microorganisms using dissolved organic matter (DOM) as a carbon source. This study reveals a novel reduction pathway in sediments that photosensitive DOM generates photoelectrons to stimulate diverse nonphototrophic microorganisms to reduce As(V). This microbial photoelectrophic As(V) reduction (PEAsR) was investigated using microcosm incubation, which showed the transfer of photoelectrons from DOM to indigenous sediment microorganisms, thereby leading to a 50% higher microbial reduction rate of As(V). The abundance of two marker genes for As(V) reduction, arrA and arsC, increased substantially, confirming the microbial nature of PEAsR rather than a photoelectrochemical process. Photoelectron ion is unlikely to stimulate photolithoautotrophic growth. Instead, diverse nonphototrophic genera, e.g., Cupriavidus, Sphingopyxis, Mycobacterium, and Bradyrhizobium, spanning 13 orders became enriched by 10-50 folds. Metagenomic binning revealed their genetic potential to mediate the photoelectron-assisted reduction of As(V). These microorganisms contain essential genes involved in respiratory As(V) reduction, detoxification As(V) reduction, dimethyl sulfoxide reductase family, c-type cytochromes, and multiple heavy-metal resistance but lack a complete photosynthesis system. The novel microbial PEAsR pathway offers new insights into the interaction between photoelectron utilization and nonphototrophic As(V)-reducing microorganisms, which may have profound implications for arsenic pollution transportation in mine stream sediment.

Distribution and sources of polycyclic aromatic hydrocarbons in cascade reservoir sediments: influence of anthropogenic activities and reservoir hydrology.

The construction of dams has caused disruptions to river connectivity, leading to alterations in the deposition of hydrophobic organic contaminants in reservoir sediments. Further investigation is warranted to explore the impact of cascade reservoirs with differing hydrological characteristics on polycyclic aromatic hydrocarbons (PAHs) distribution in sediment. This study examines the presence of 30PAHs in the sediments collected from six cascade reservoirs situated in the Wujiang River basin during January and July 2017. The results showed that Σ30PAHs ranged from 455-3000ng/g dw (mean 1030ng/g dw). Anthropogenic activities and reservoir hydrology determined the distribution trend of PAHs in sediments, with an overall increase from upstream to midstream and then a decrease downstream. The PAH levels were highly linked to the secondary industry (P < 0.05). This was further supported by the relationship between the PAH emissions from coal combustion and traffic sources analyzed by the positive matrix factorization model and economic parameters in the wet season (P < 0.01). At the same time, reservoir age (RA) showed a positive correlation with PAH concentrations (P < 0.05), while hydraulic retention time (HRT) exhibited a negative correlation with PAH levels (P = 0.03). The relationship between total organic carbon (TOC) and PAHs in stream sediments worldwide was nonlinear (P < 0.01), with PAH concentrations initially rising and then falling as TOC levels increased. Concerns regarding carcinogenic risk were raised due to contributions from coal and vehicular sources, with the risk increasing with RA.

Indicator element selection and lithological mapping using deep learning methods in the Dahongliutan area, NW China

Rare metal resources are extensively used in the emerging energy field, making the security and sustainability of rare metal supply chains critical issues. Pegmatite-type rare metal deposits are a significant source of rare metal resources. Geochemistry is one of the most direct and effective methods of mineral exploration. In this study, whole-rock geochemical data from the Akesayi region, located in the Western Kunlun area of China, were used to identify the indicative elements of pegmatite automatically. Based on the stream sediment geochemical data, various deep learning models have been employed to achieve automatic lithological identification of the area. The results indicate that a novel interpretable model using SHapley Additive exPlanations (SHAP) and eXtreme Gradient Boosting (XGBoost) was employed to select indicative elements for the pegmatite in the Akesayi region, identifying Ta and Rb as key elements. The state-of-the-art application of deep-learning algorithms for lithological mapping has proven to be highly effective. Among the four approaches, the ensemble strategy integrating 1D convolutional neural networks, 2D3D convolutional neural networks, and dual-branch neural networks yields the best lithological mapping results. This approach resulted in a total classification accuracy of 90.422 %, an average accuracy of 90.502 %, a Kappa coefficient of 89.643 %, and a user accuracy of 65.530 % for the pegmatite lithological unit. These results demonstrate that the proposed model can provide robust technical support for the exploration of rare metal pegmatites in regions with challenging natural conditions and limited research.

Two-Step Clustering for Mineral Prospectivity Mapping: A Case Study from the Northeastern Edge of the Jiaolai Basin, China

The advancement of geological big data has rendered data-driven methodologies increasingly vital in Mineral Prospectivity Mapping. The effective integration of quantitative and qualitative data, including experiential and knowledge-based insights, is crucial in geological data fusion. Specifically, the conversion of raw data into samples and the selection of predictive methods are two core issues that constitute the focus of this study. Traditional clustering methods require the user to specify the number of clusters in advance. The two-step clustering can automatically determine the clustering result ‘k’ while analyzing both continuous and categorical variables, by building a Cluster Feature (CF) and using information criteria to merge nodes. In this study, we conducted an analysis utilizing stream sediment element data, residual gravity anomalies, and fault distribution through the two-step clustering method. Factor analysis (FA) was employed to reduce 16 elemental variables from stream sediments into five uncorrelated continuous variables; additionally, residual gravity anomalies were transformed from continuous to categorical variables via an interval-based method before being combined with fault distribution, resulting in seven variables for clustering. The research findings indicate that categorical variables significantly influence clustering results; concurrently, as the importance of continuous variables within the cluster increases, so does k. When only one categorical variable is present, residual gravity anomalies show significantly better clustering than fault distribution; however, when two categorical variables are involved, it is essential to consider the quantity of categories: more categories lead to poorer quality. The results from the Jiaolai Basin’s northeastern margin indicate a significant correlation with known gold deposits; two-step clustering is a promising and effective method for improving mineral prospecting efforts.

Distribution, enrichment characteristics and prospecting potential of lithium in Uzbekistan: Insights from 1:1 million geochemical mapping

With the world economy gradually shifting to alow‑carbon and greener model in recent years, there is a growing need for developing key metals like lithium in economic development. Economic growth has sped up the country's shift to a green economy along with Uzbekistan's reform and opening up, and the country's developing major mineral resources, such as lithium, have garnered a lot of attention. Owing to lithium resource protential of Uzbekistan is unclear, it is important to examine the possibility of lithium mineralization. The distribution and enrichment characteristics of lithium in the Uzbeksitan Tianshan are studied in this paper, based on geochemical mapping data at a 1:1000000 scale. It's concluded that stream sediments from the Tianshan region of Uzbekistan have higher concentration of lithium than the continental crust, and the South Tianshan has the highest lithium content. Lithium mineralization has been found in the lithium-geochemical anomaly areas in the eastern part of Uzbekistan South Tianshan through field investigation. Spodumene pegmatite, the first instance of pegmatitic type lithium mineralization in this region and even in the Tianshan orogenic belt of Central Asia. In conjunction with the geological background analysis, the metallogenic potential of lithium was assessed, resulting in the identification of four regions with lithium geochemical anomaly, and these sites will serve as target areas for Li deposits prospecting work in the future. This work has significant implications for the advancement of our understanding of the metallogenic theory of pegmatite-type Li deposits, as well as practical guiding significance for lithium ore prospecting in the Tianshan orogenic belt of Central Asia.

Unraveling the interplay between seasonal variations in macroinvertebrates and microplastics in urban stream sediments

Unraveling the interplay between seasonal variations in macroinvertebrates and microplastics in urban stream sediments

Ecological and Human Health Risk Assessment Based on Stream Sediments from Coastal Oecusse (Timor)

Timor Island is located in a geologically complex region strongly affected by the collision of the Australian margin with the Banda volcanic arc. In Oecusse, an enclave of East Timor in the western part of Timor, crop out several lithological units of the Banda Terrane that are associated with the obduction of oceanic crust and upper mantle on the Australian continental crust. This study reports the geochemistry of stream sediments from the coastal region of the Oecusse enclave, where the Banda Terrane is best represented, employing statistical analyses to discern the sources of metal(oid)s and assessing ecological and health risks. Arsenic, Cr, and Ni are the elements with higher potential ecological risk factors. The potential ecological risk index (PERI), which combines single indexes of ecological risk factors for multiple elements, is very high in a stream sourced by the Lolotoi-Mutis Complex. Significant risks for human health were found for As (sourced by the Lolotoi-Multis Metamorphic Complex and basalts of the Barique Formation), Mn (sourced by the Maubisse and Barique formations), and V (sourced by the Manamas Formation). The highest values of hazard index (HI), however, were determined with Cr, in particular for children (HI higher than 10 in 12 sediments sourced by ultramafic units and their covering sedimentary units). This investigation shows that high geogenic concentrations of several elements, particularly those derived from the oceanic crust and the upper mantle, raise significant cancer and non-carcinogenic risks.