Fine Sediment Research Articles

Four New Caddisfly Species of Marilia Müller, 1880 (Trichoptera: Odontoceridae) from a Tailings Dam Disaster Area, Rio Doce basin, Brazil

Marilia is the most diverse genus of the caddisfly family Odontoceridae, being distributed throughout the Oriental, Australasian and Neotropical regions. Herein, we describe four new Neotropical species from the Atlantic Forest, Rio Doce basin, Brazil. This basin was partly affected by a flood of 50 million m3 of mud and mining debris in 2015. Due to this disaster, numerous monitoring activities have been carried out to assess the impact generated. Material from one of these attempts was used to describe the new species: Marilia aranan sp. nov., Marilia krenak sp. nov., M. maxakali sp. nov. and M. mukurin sp. nov. Additionally, we provide a new state record of M. guaira from Minas Gerais. Marilia aranan sp. nov. was collected in tributaries as well as in the impacted area 7 years after the disaster. Marilia guaira and M. krenak sp. nov. were collected only in the impacted area. The other species were found only in tributaries. Odontoceridae are considered highly sensitive to disturbance. The presence of Marilia species suggests that parts of the riverbed have recovered from the fine tailing sediments and also highlights the importance of tributaries in the recolonization process.

The risk may not be limited to flooding: polluted flood sediments pose a human health threat to the unaware public

BackgroundBecause of global climate change, extreme flood events are expected to increase in quantity and intensity in the upcoming decades. In catchments affected by ore mining, flooding leads to the deposition of fine sediments enriched in trace metal(loid)s. Depending on their concentration, trace metal(loid)s can be a health hazard. Therefore, exposure of the local population to flood sediments, either by ingestion (covering direct ingestion and consuming food grown on these sediments) or via inhalation of dried sediments contributing to atmospheric particulate matter, is of concern.ResultsThe extreme flood of July 2021 deposited large amounts of sediment across the town of Eschweiler (western Germany), with the inundation area exceeding previously mapped extreme flood limits (HQextreme). These sediments are rich in fine material (with the < 63 µm fraction making up 32% to 96%), which either can stick to the skin and be ingested or inhaled. They are moderately to heavily enriched in Zn > Cu > Pb > Cd > Sn compared to local background concentrations. The concentrations of Zn, Pb, Cd, Cu, and As in flood sediments exceed international trigger action values. A simple assessment of inhalation and ingestion by humans reveals that the tolerable daily intake is exceeded for Pb. Despite the enrichment of other trace elements like Zn, Cu, Cd, and Sn, they presumably do not pose a risk to human well-being. However, exposure to high dust concentrations may be a health risk.ConclusionsIn conclusion, flood sediments, especially in catchments impacted by mining, may pose a risk to the affected public. Hence, we propose to (I) improve the flood mapping by incorporating potential pollution sources; (II) extend warning messages to incorporate specific guidance; (III) use appropriate clean-up strategies in the aftermath of such flooding events; (IV) provide medical support, and (V) clue the public and medical professionals in on this topic accordingly.Graphical

Surface Displacement of Hurd Rock Glacier from 1956 to 2019 from Historical Aerial Frames and Satellite Imagery (Livingston Island, Antarctic Peninsula)

In the second half of the 20th century, the western Antarctic Peninsula recorded the highest mean annual air temperature rise in the Antarctic. The South Shetland Islands are located about 100 km northwest of the Antarctic Peninsula. The mean annual air temperature at sea level in this Maritime Antarctic region is close to −2 °C and, therefore, very sensitive to permafrost degradation following atmospheric warming. Among geomorphological indicators of permafrost are rock glaciers found below steep slopes as a consequence of permafrost creep, but with surficial movement also generated by solifluction and shallow landslides of rock debris and finer sediments. Rock glacier surface velocity is a new essential climate variable parameter by the Global Climate Observing System, and its historical analysis allows insight into past permafrost behavior. Recovery of 1950s aerial image stereo-pairs and structure-from-motion processing, together with the analysis of QuickBird 2007 and Pleiades 2019 high-resolution satellite imagery, allowed inferring displacements of the Hurd rock glacier using compression ridge-and-furrow morphology analysis over 60 years. Displacements measured on the rock glacier surface from 1956 until 2019 were from 7.5 m to 22.5 m and surface velocity of 12 cm/year to 36 cm/year, measured on orthographic images, with combined deviation root-mean-square of 2.5 m and 2.4 m in easting and northing. The inferred surface velocity also provides a baseline reference to assess today’s displacements. The results show patterns of the Hurd rock glacier displacement velocity, which are analogous to those reported within the last decade, without being possible to assess any displacement acceleration.

The Clay Mineralogy and Geochemistry of Sediments in the Beibu Gulf, South China Sea: A Record of the Holocene Sedimentary Environmental Change

In this study, we analyzed the clay mineralogy and geochemistry of surface and drill core samples from the northeastern Beibu Gulf in order to unravel the sediment provenance of, and factors controlling, the sedimentary environment. The main clay mineral assemblage in the surface sediment samples included kaolinite (27–72%), smectite (4–51%), illite (7–20%), and chlorite (8–17%). The study area comprises three major clay distribution zones (from the northeastern coastal area to central Beibu Gulf basin), i.e., the kaolinite-dominated, kaolinite–smectite, and smectite-dominated zones. The zoning of the clay mineralogy and major and trace elements indicated the mixing of coarse terrigenous sediments with distal fine sediments. Early Holocene sea level rise was documented in core B15-1, which had three sedimentary units (divided into Units 1–3 from top to bottom), as revealed by the changes in the dominant clay minerals and geochemical/oxide ratios (SiO2/Al2O3, Rb/Sr, Sr/Ba, and Ti/Ca) in Unit 2. Unit 1 and Unit 3 were likely deposited in the continental and marine environments, respectively. The low sedimentation rate and hydrodynamic disturbance may have influenced the deposition process more than climatic fluctuations.

Substratum Raking Can Restore Interstitial Habitat Quality in Swedish Freshwater Pearl Mussel Streams

Functional and oxygenated stream beds provide crucial habitat for multiple endangered stream taxa, including endangered freshwater mussels, fishes, and insect larvae. Stream bed restoration measures such as substrate raking are often applied to mitigate excess fine sediment introductions and stream bed colmation, yet such measures are controversial. In this study, we conducted a systematic experiment in which sites with stream bed raking and removal of macrophytes were monitored over two years and compared with before-treatment conditions and untreated reference sites in the Swedish Brånsån stream, which still contains a population of the endangered freshwater pearl mussel Margaritifera margaritifera. The stream bed restoration resulted in improved habitat quality, as evident from decreased substrate compaction, increased redox potential, and oxygen supply into the stream bed. In contrast to previous studies in Central European catchments with more intensive agricultural catchment uses, the effects of the restoration measure were much longer, extending over two years. Consequently, stream bed raking and macrophyte removal can be considered a useful and more long-lasting restoration measure than currently assumed, especially in streams where excess input of fine sediment has already been mitigated, where catchment land use is rather extensive, and where near-natural flow regimes still prevail.

PERENCANAAN INSTALASI PENGOLAHAN AIR LIMBAH PADA INDUSTRI TAHU (Studi Kasus Pabrik Tahu WD Lamper Lor Semarang Selatan)

In the production process, the tofu industry produces solid and liquid waste. The waste contains organic matter with high levels of BOD, COD, and TSS and does not meet quality standards. If the waste is directly discharged into the environment, it will reduce the carrying capacity of the environment. This research was conducted at the WD Lamper Lor Tofu Factory, with the aim of planning the design and RAB for the construction of the wastewater treatment plant at the Tofu Factory. This research uses quantitative analysis methods which are presented in the form of numbers which are then explained and interpreted in the form of descriptions. The quality of BOD, COD, TSS, and pH were 144 mg/L, respectively; 380 mg/L; 98 mg/L; and 4.34. Based on the quality standards, the wastewater does not meet the requirements, so it is necessary to plan a wastewater treatment plant. Researchers plan the processing stages, namely Reservoir, Equalization, Anaerobic Digester, Gas Storage, Presettlement Tub, Anaerobic Biofilter, and Final Sedimentation Tub. The estimated effluent from the processing of BOD, COD, and TSS is 2,916 mg/L, respectively; 7.695 mg/L; 2.116 mg/L. In addition to processing it into water that is fit for reuse, the design of this wastewater treatment plant produces methane gas that can be used for the tofu-making process or can be used on a household scale. The total budget plan for the planning of the Wastewater Treatment Plant at the WD Tofu Factory is 31,106,117.05.

Carbon sequestration potential of process‐based river restoration

AbstractFloodplain restoration can enhance the capacity for carbon sequestration by facilitating higher water tables, deposition of fine sediment, and increased input and residence time of organic matter. We measured floodplain soil organic carbon stocks in nine stream restoration projects across the western United States and compared them to nearby degraded and reference condition floodplains. Degraded floodplains had the lowest soil mean carbon stocks in the majority of floodplains measured (range 161–894 Mg C/ha), and reference stocks had the highest stocks (range 391–904 Mg C/ha) of those with statistically significant differences between the three categories. Across all sites measured, stream restoration sites, referred to as treatment sites, had stocks (range 203–1028 Mg C/ha) similar to degraded condition floodplains but the largest range. When modeled under degraded conditions, four out of nine of the treatment sites had significantly higher OC stocks than predicted. Climate and geologic variables are most influential in predicting carbon stocks, and floodplains in the interior western USA have the highest carbon stocks. As the demand for carbon sequestration increases due to climate change, ecologically responsible floodplain restoration provides a significant opportunity for carbon storage. However, despite the statistically significant relationships we observed in this dataset, the variations within the data in relation to degraded/treatment/reference categories illustrate the uncertainties in quantifying the effects of restoration on floodplain carbon stocks.

Assessing the impacts of fine sediment removal on endogenous pollution release and microbial community structure in the shallow lakes

Resuspension is a crucial process for releasing endogenous pollution from shallow lakes into the overlying water. Fine particle sediment, which has a higher contamination risk and longer residence time, is the primary target for controlling endogenous pollution. To this end, a study coupling aqueous biogeochemistry, electrochemistry, and DNA sequencing was conducted to investigate the remediation effect and microbial mechanism of sediment elution in shallow eutrophic water. The results indicated that sediment elution can effectively remove some fine particles in situ. Furthermore, sediment elution can inhibit the release of ammonium nitrogen and total dissolved phosphorous into the overlying water from sediment resuspension in the early stage, resulting in reductions of 41.44 %–50.45 % and 67.81 %–72.41 %, respectively. Additionally, sediment elution greatly decreased the concentration of nitrogen and phosphorus pollutants in pore water. The microbial community structure was also substantially altered, with an increase in the relative abundance of aerobic and facultative aerobic microorganisms. Redundancy analysis, PICRUSt function prediction, and the correlation analysis revealed that loss on ignition was the primary factor responsible for driving changes in microbial community structure and function in sediment. Overall, the findings provide novel insights into treating endogenous pollution in shallow eutrophication water.

On the role of organic matter composition in fresh-water kaolinite flocculation

Organic matter has long been understood to affect fine sediment flocculation, yet the specific effects of different types of organic matter remain only partially understood. To address this knowledge gap, laboratory tank experiments were conducted in fresh water to investigate the sensitivity of kaolinite flocculation to varying organic matter species and contents. Three species of organic matter (xanthan gum, guar gum and humic acid) were investigated at varying concentrations. Results revealed a significant enhancement in kaolinite flocculation when organic polymers (xanthan gum and guar gum) were introduced. In contrast, the addition of humic acid had minimal influence on aggregation and floc structure. Notably, the nonionic polymer guar gum demonstrated greater efficacy in promoting the development of floc size compared to the anionic polymer, xanthan gum. We observed non-linear trends in the evolution of mean floc size (Dm) and boundary fractal dimension (Np) with increasing ratios of organic polymer concentration to kaolinite concentration. Initially, increasing polymer content facilitated the formation of larger and more fractal flocs. However, beyond a certain threshold, further increases in polymer content hindered flocculation and even led to the break-up of macro-flocs, resulting in the formation of more spherical and compact flocs. We further quantified the co-relationships between floc Np and Dm and found that larger Np values corresponded to larger Dm. These findings highlight the significant impact of organic matter species and concentrations on floc size, shape and structure, and shed light on the complex dynamics of fine sediment and associated nutrients and contaminants in fluvial systems.

Attachment efficiency among fine sediment considering surface heterogeneity

Interactions among natural fine sediment particles are essential to the flocculation process, and are affected significantly by surface heterogeneity. In this study, a series of mathematical sediments are generated to characterize the natural particles with different sizes and surface heterogeneities of micro-morphology and charge distribution. The total particles interactions are calculated with Derjaguin–Landau–Verwey–Overbeek (DLVO) theory to theoretically estimate the attachment efficiency (α), where the irreversible and reversible attachment are distinguished. The results show that approaching particles are easier to attached to after collision with increasing particle size (with a fixed size ratio between particles) or increasing similarity in size of both particles. Meanwhile, the electrostatic interactions increase significantly with the presence and enlargement of surface heterogeneities, especially at large separations, which reduces the more approachable reversible attachment, and thus mitigates the flocculation in aquatic systems. This study gives an insight into the mechanism of attachment among sediment considering surface heterogeneities, and provides a quantitative estimation of attachment efficiency which is adaptable for sediment flocculation modelling.

Submarine outfall effect on subtidal macrobenthic communities in a southwestern Atlantic coastal city

Submarine outfalls are an effective alternative for the final discharge of wastewater. The aim was to evaluate the subtidal macrobenthic community's responses and the changes in bottom sedimentary dynamics due to submarine outfall (SO) location. Sampling stages were: before SO (BSO), after SO (ASO) and after treatment plant (AEDAR). Sampling sites were determined at different distances from the coastline (coastal, oceanic, and reference) on both sides of the pipe (North and South). Species shifts (from tolerant to sensitive) were observed along with a decrease in organic matter in the AEDAR Stage. There were changes in the sedimentary dynamic with sediment accumulation on the South side of the SO (finest sediments) and erosion on the North side (coarsest sediments) in the ASO and AEDAR Stages. Species turnover was higher than nesting in all stages. Functional trait analysis allowed the identification of temporal variations in benthic communities. The body size, development mode, feeding mode, habit, adult mobility and tolerance to pollution were useful functional traits to detect changes through Stages (BSO, ASO, and AEDAR). Biotic indices classified the sites as slightly disturbed, indicating a slight improvement in the AEDAR Stage.

SEQUENCE OF VALLEY DEVELOPMENT OF ALAKNANDA AND ITS TRIBUTATIES &amp; QUATERNARY SEDIMENTATION, GARHWAL HIMALAYA, PARTS OF CHAMOLI TEHRI UTTAKASHI &amp; PAURI UTTAR PRADESH (UTTRARKHAND STATE ) INDIA

SEQUENCE OF VALLEY DEVELOPMENT OF ALAKNANDA AND ITS TRIBUTATIES &amp; QUATERNARY SEDIMENTATION, GARHWAL HIMALAYA, PARTS OF CHAMOLI TEHRI UTTAKASHI &amp; PAURI UTTAR PRADESH (UTTRARKHAND STATE ) INDIA

Impact of land use, land cover and morphometry on stream hydrochemistry and fine sediment geochemistry along the transect of Alaknanda basin, Garhwal Himalaya, India: an integrated study

Impact of land use, land cover and morphometry on stream hydrochemistry and fine sediment geochemistry along the transect of Alaknanda basin, Garhwal Himalaya, India: an integrated study

Differences in substratum preferences and behaviour within the invasive Corbicula species complex

Abstract Clams from the Corbicula species complex of Asian origin are invasive all over the world, currently extending their distribution to waters of the natural thermal regime in Central European areas. Features linking the clams to their habitats in newly invaded areas have not been fully examined. These include substratum preferences and mobility, which may be key to determining potential niche overlap with native bivalves and gaining a better knowledge of their potential active dispersal and impact. Therefore, our aim was to determine the substratum preferences, horizontal locomotion and burrowing behaviour of three Corbicula morphospecies from Poland, Central Europe: two populations of undetermined Corbicula sp. from an artificially heated habitat and water of the natural thermal regime (cold water), as well as Corbicula leana, and Corbicula fluminea (from artificially heated and cold water, respectively). To determine the preferred substratum range, we used pairwise choice tests with a range of muddy, sandy, and gravelly substrata, as well as zebra mussel shells. Then, we conducted behavioural observations (locomotion and burrowing) by CCTV cameras on substrata found as preferred and non‐preferred by clams. All morphospecies preferred fine‐grained over coarser substrata. C. fluminea from cold water had the widest range of substratum preferences. By contrast, C. leana from artificially heated water and Corbicula sp. from cold water showed the narrowest substratum preferences and spent the longest time deeply burrowed. The longest duration of burrowing activity was noted on non‐preferred coarser substrata, which may indicate difficulties in burrowing. On non‐preferred coarse substrata, C. fluminea (cold water) crawled more than the other morphospecies. Our results show that sediment preferences and behaviour (burrowing and locomotion) differ among various Corbicula morphospecies in Europe, probably also varying their invasive potential. This knowledge is important for determining the overlap of habitat preferences of non‐native Corbicula clams with native bivalves, which is critical for determining potential competition strength, impact, and/or displacement. Our results also indicate that habitats with fine sediments could be more threatened by Corbicula invasions.

Mill dams impact microbiome structure and depth distribution in riparian sediments.

Damming has substantially fragmented and altered riverine ecosystems worldwide. Dams slow down streamflows, raise stream and groundwater levels, create anoxic or hypoxic hyporheic and riparian environments and result in deposition of fine sediments above dams. These sediments represent a good opportunity to study human legacies altering soil environments, for which we lack knowledge on microbial structure, depth distribution, and ecological function. Here, we compared high throughput sequencing of bacterial/ archaeal and fungal community structure (diversity and composition) and functional genes (i.e., nitrification and denitrification) at different depths (ranging from 0 to 4 m) in riparian sediments above breached and existing milldams in the Mid-Atlantic United States. We found significant location- and depth-dependent changes in microbial community structure. Proteobacteria, Bacteroidetes, Firmicutes, Actinobacteria, Chloroflexi, Acidobacteria, Planctomycetes, Thaumarchaeota, and Verrucomicrobia were the major prokaryotic components while Ascomycota, Basidiomycota, Chytridiomycota, Mortierellomycota, Mucoromycota, and Rozellomycota dominated fungal sequences retrieved from sediment samples. Ammonia oxidizing genes (amoA for AOA) were higher at the sediment surface but decreased sharply with depth. Besides top layers, denitrifying genes (nosZ) were also present at depth, indicating a higher denitrification potential in the deeper layers. However, these results contrasted with in situ denitrification enzyme assay (DEA) measurements, suggesting the presence of dormant microbes and/or other nitrogen processes in deep sediments that compete with denitrification. In addition to enhanced depth stratification, our results also highlighted that dam removal increased species richness, microbial diversity, and nitrification. Lateral and vertical spatial distributions of soil microbiomes (both prokaryotes and fungi) suggest that not only sediment stratification but also concurrent watershed conditions are important in explaining the depth profiles of microbial communities and functional genes in dammed rivers. The results also provide valuable information and guidance to stakeholders and restoration projects.

Assessing gully erosion and rehabilitation using multi temporal LiDAR DEMs: Case study from the Great Barrier Reef catchments, Australia

Millions of dollars are being spent on gully rehabilitation to help reduce excess fine sediment delivery to the Great Barrier Reef (GBR). There is an urgent need for (i) prioritisation of active gullies for rehabilitation and (ii) the development of methodologies to inform the effectiveness of remediation. In this study we analyse DEMs of Difference derived from 0.5 m resolution 2–3 year interval multi-temporal LiDAR data collected pre and post rehabilitation at three variable gully morphologies in the Burdekin catchment. Our analysis indicates that the highest annual average fine sediment erosion rates for the untreated control gullies occur at the linear gully (53.38 t ha−1 y−1) followed by linear-alluvial gully (34.24 t ha−1 y−1) and least at the alluvial gully (14.41 t ha−1 y−1). The proportional loss or export of fine sediment from the gullies in their un-treated condition ranges from ∼68 to 90% of what is eroded, and when the gullies are treated the proportion of fine sediment that is retained in the gully proportional to what is eroded increases to ∼60% at all sites. Without pre-treatment baseline erosion rates, and additional post treatment LiDAR captures, it is difficult to quantify the treatment effectiveness. Our results offer insights in the erosion mechanisms within different geomorphic gully morphologies and rehabilitation effects in these erosional landforms. This study provides crucial knowledge of gully dynamics that can be coupled with other lines of evidence for better prioritisation of rehabilitation in the GBR catchments.

Benthic fluxes and mineralization processes at the scale of a coastal lagoon: Permeable versus fine-grained sediment contribution

Benthic fluxes of biogenic compounds play a major role in the biogeochemistry of shallow aquatic environments. Quantifying these fluxes at the scale of a lagoon is a challenge, especially when sediments are heterogeneous and fluxes at the sediment-water interface combine diffusive and advective transport processes. Diagenetic processes and associated benthic fluxes were quantified across different seasons in a lagoon of the French Mediterranean coast (La Palme lagoon) from vertical profiles of pore water and sedimentary solid fraction carried out at many representative stations of the lagoon. The northwestern part of the lagoon is covered with fine-grained sediment with low permeability and the rest of the lagoon contains permeable sandy sediment. We obtained vertical profiles with centimetre-scale resolution of water content, salinity, and major particulate and dissolved biogenic compounds of C, N, P, Si, S, Fe and Mn. This study allowed us to refine the sedimentary mapping of the lagoon, to specify the spatio-temporal evolution of biogeochemical processes, and to determine more precisely the part of the diffusive fluxes of nutrient compared to advective fluxes. Comparison of the vertical profiles with a molecular diffusion transport model shows that molecular diffusion is the dominant process in fine-grained sediments, while sandy sediments are dominated by advection due to circulation of lagoon water in shallow sediments. Benthic respiration renders fine-grained and sandy sediments anoxic from the first few mm below the sediment-water interface, particularly due to the availability of labile organic matter. Benthic dissolved inorganic nitrogen fluxes are of the same order of magnitude in both sediment types, despite the different flux mechanisms. This suggests that the intensity of organic matter mineralization processes is the same in fine and sandy sediments. Benthic phosphate fluxes are greater in sandy than in fine sediments because phosphorus is more efficiently retained in the solid fraction of fine sediments. Thus, sandy sediments play a dominant role in the pelagic-benthic coupling of the lagoon.

Extensive estuarine sedimentary storage of plastics from city to sea: Narragansett Bay, Rhode Island, USA

Plastics are an important new component of the global sedimentary system, and much concern exists about their transport, fate and impact. This study presents the first system-scale assessment of sedimentary storage of microplastic for an estuary, Narragansett Bay, RI (USA), and the measurements of shoreline and seabed sediments add to the growing body of literature demonstrating high coastal concentrations. Microplastic concentrations in sediments ranged from 396 to over 13,000 MP particles kg−1 dry sediment (DW), comparable to other shoreline and seafloor sites located near urban centers. As previously reported for fine sediment and other pollutants, estuarine plastic storage is extensive in Narragansett Bay, especially within the upper urbanized reaches. Over 16 trillion pieces of plastic weighing near 1000 tonnes is calculated to be stored in surface sediments of the Bay based on a power-law fit. This work highlights that estuaries may serve as a significant filter for plastic pollution, and this trapping may have negative consequences for these valuable, productive ecosystems but offer potential for efficient removal.

The seasonal movement of sediment-associated marine-derived nutrients in a morphologically diverse riverbed: the influence of salmon in an Interior British Columbia river

PurposeThis study (1) investigated the extent to which flocculation and the hydrological and morphological attributes of an interior salmon-bearing river regulate the seasonal storage of marine-derived nutrients (MDN) and (2) compared the contribution of MDN to the fine bed sediment relative to other nutrient sources to the river.MethodsPrevious research has determined that the co-existence of re-suspended fine sediment, generated by salmon redd construction, with salmonid excretion and decay products in the water column creates ideal conditions for the flocculation of these inorganic and organic particles. Stored and suspended fine bed sediment was sampled from seven sites with varying morphologies and bed substrate down the length of a large spawning river in the interior of British Columbia over a 12-month period. MDN contributions to the sediment was tracked using aggregated versus dispersed particle size, carbon-to-nitrogen ratios, stable carbon and nitrogen isotopes, and MixSIAR modeling.Results and discussion(1) There was a significant longitudinal spatial distinction of nutrient retention between sites upstream and downstream of a large seasonally inundated floodplain; (2) the MDN isotopic signal in the surficial stored bed sediment in this sample year was short term; and (3) upstream spawner numbers, substrate size, stream morphology, and discharge were relevant to both the magnitude and retention time of sediment-associated MDN.ConclusionA cumulative magnification of MDN was correlated with the distance from the headwaters and the number of upstream spawners. The relationship between MDN retention in interior rivers, and possible multi-year accumulation, was influenced by variability in channel morphology, substrate size, and the presence of an inundated floodplain halfway down the river.

Performance of permeable concrete mixes based on cement and geopolymer in aggressive aqueous environments

The permeable pavement efficiently manages stormwater, which is acidic and contains fine sediments and heavy metals exhausted by vehicles driving on this material. The heavy metal removal in permeable concrete samples based on geopolymer and Portland cement was examined in this study. Their performance when exposed to strong acids and turbid water were also investigated. They were able to infiltrate 28 L of water in 60 min and gained a compressive strength greater than 25 MPa in 2 weeks after casting. However, it was found that its porous structure was clogged with fine sediments when water containing bentonite clay passed through them for multiple cycles. To evaluate their metal removal capacity, a concentration of 10 mg/l of cadmium-containing solution was passed through such samples for a continuous period of 8 h. They were able to trap nearly 95% of the cadmium ions from the simulated wastewater during the column experiment. Their adsorption behaviour fits well with the pseudo-second-order kinetic and Langmuir isotherm models, implying that the main removal mechanism is chemisorption. To examine their acid resistance capacities, cement- and geopolymer-based mortar samples were exposed to acids for 2 weeks. The acid-exposed samples were severely degraded, as the mass loss in the geopolymer was determined to be 64% lower than that of the cement sample. Geopolymer-based permeable pavements are ecological, harden in moist air, gain higher strength at early ages, are acid resistant, and also remediate groundwater contamination.