Dredged Sediments Research Articles

Flocculating and dewatering of lake sediment: An in-situ pilot study comparing synthetic polymers and biopolymers for restoring lake water quality and reusing phosphorus

Dredging of lake sediment is a method to remove accumulated phosphorus and nitrogen in lakes and thereby reducing the risk of eutrophication. After dredging, the sediment is dewatered to reduce the volume. It is important to get a high dry matter content and ensure that the filtrate does not contain harmful compounds so it can be returned to the lake. A pilot-scale belt filter and flexible intermediate bulk containers (FIBC) were used for dewatering lake sediment with the sediment treated with a synthetic polymer or three different biopolymers. The goal of the study was to retain the phosphorus in the filter cake while returning the filtrate to the lake with a minimal phosphorus content. Results showed dry matter content of up to 16 % in the dewatered sediment and the sediment retained 96–99 % of the phosphorus. Furthermore, nitrogen was reduced by 27–71 % in the filtrate water. Toxicity tests found low ecotoxicity for most biopolymer filtrates, whereas synthetic polymer showed the highest potential ecotoxicity. Consequently, biopolymers provided satisfactory results, proving more environmentally friendly despite requiring longer filtration time.

Applying industrial side streams in the neutralization of acid generating sulfide-rich sediments – The impact on pH and leaching of harmful elements

Acid sulfate soils can cause severe environmental harm due to a low pH and mobilization of harmful elements. Acid sulfate soil material is formed when oxidation of sulfide minerals causes a drop in pH to <4.0 for mineral oil materials and <3.0 for organic soil materials or when the soil materials contain enough sulfide to potentially do so.Two dredged, acid sulfate soil materials from Finland were used in this laboratory study. Chemical analyses were performed to determine the pre-incubation characteristics of both fresh dredged sediment samples and oxidized samples after 23 weeks of incubation. Total element concentrations were determined after digestion in aqua regia by ICP-MS or ICP-OES. The leachable concentration of elements was determined by using the two-stage shaking test (method SFS-EN 12457-3). The leaching of harmful elements (Cd, Co, Ni, Mn, and Zn) was high in the acidified dredged spoil samples. Also, the leaching of S was high. The soluble concentration was dependent on total concentration, pH, and the mobility of the elements.During a 23-week oxidation period, the impact of various amounts of industrial side streams (alkaline ashes, industrial lime residues) as neutralizing agents on the acid-generating dredged sediments was investigated in the laboratory. Calcite was used as a reference material. pH measurements were carried out during the incubation period. The leaching of elements was determined with a modified method based on the SFS-EN 12457-2 standard before and after oxidation.The untreated dredged spoils and the samples treated with too low amounts of neutralizing agents, acidified to pH < 4 during the oxidation period. Thus, harmful elements were leached out. However, the 100 % theoretical calculated neutralization need was suitable to prevent acidification and thus the leaching of harmful substances from the neutralized acid-generating dredged spoils. However, the leaching of Mo increased at neutral pH values. The results showed that industrial side streams can be applicable for the neutralization of acid sulfate soil materials. However, the legislation must also be considered.

Coupling effect of cement-stabilization and biopolymer-modification on the mechanical behavior of dredged sediment

Nowadays, biopolymer stabilization as a promising eco-friendly approach in soft ground improvement has attracted wide attentions. However, the feasibility of using biopolymer as a green additive of cement-stabilized dredged sediment (CDS) with high water content is still unknown. In this study, guar gum (GG) and xanthan gum (XG) were adopted as typical biopolymers, and a series of unconfined compressive strength (UCS), splitting tensile strength (STS) and scanning electron microscopy (SEM) tests were performed to evaluate the mechanical and microstructural properties of XG- and GG-modified CDSs considering several factors including biopolymer modification, binder–soil ratio and water–solid ratio. Furthermore, the micro-mechanisms revealing the evolutions of mechanical properties of biopolymer-modified CDS were analyzed. The results indicate that the addition of XG can effectively improve the strength of CDS, while the GG has a side effect. The XG content of 9% was recommended, which can improve the 7 d- and 28 d-UCSs by 196% and 51.8%, together with the 7 d- and 28 d-STSs by 118.3% and 42.2%, respectively. Increasing the binder–soil ratio or decreasing the water–solid ratio significantly improved the strength gaining but aggravated the brittleness characteristics of CDS. Adding XG to CDS contributed to the formation of microstructure with more compactness and higher cementation degrees of ordinary Portland cement (OPC)-XG-stabilized DS (CXDS). The micro-mechanism models revealing the interactions of multiple media including OPC cementation, biopolymer film bonding and bridging effects inside CXDS were proposed. The key findings confirm the feasibility of XG modification as a green and high-efficiency mean for improving the mechanical properties of CDS.

An electrochemical strategy for dredged sediment resource utilization: Phosphorus forms transformation by a neutral pH electro-Fenton system

Dredged sediment has a high-water content and complex contaminant composition, dramatically impacting the environment if not treated and managed correctly. However, at the same time, it is also a valuable phosphorus-rich resource. Treating contaminated dredged sediments for resource recycling is critical to achieving sustainable development goals. In this study, a novelty neutral pH electro-Fenton (EF) experimental device was specifically designed for phosphorus (P) transformation study in dredged sediment. Result showed that the transformation of P forms in dredged sediments due to ·OH generation in this EF system. The decrease rates of organic P (OP) and apatite P (Ca–P) were 21.8 % and 69.6 %, respectively, while, the increase rates inorganic P (IP) and non-apatite inorganic P (Fe–P) were 25.2 % and 250.0 %, respectively, after 6 h of EF reaction. Analysis of the microbial community revealed that the EF reaction did not significantly reduce microbial diversity in the dredged sediment (p > 0.05). Furthermore, the abundance of Massilia and Thiobacillus, which are involved in transforming P form, increased significantly following the EF reaction and was positively correlated with Fe–P and IP (R2 > 0.999) and negatively correlated with OP and Ca–P (R2 > 0.999). This study proves that treating polluted dredged sediment with a neutral pH EF system can transform P into bioavailable forms. This work provides a new and sustainable strategy for recycling P from phosphorus-rich waste streams as a substitute for mining P rock.

The beneficial reuse of contaminated sediment: Long-term assessment of fly ash and lime-based mixtures

In recent decades, sediment has been recognised as a problematic resource due to its potentially harmful effects and the large quantities present in water bodies. There is a need to properly manage large quantities of dredged sediments so that they can be used as a resource and not necessarily treated as a waste product. This research investigates the effects of ageing and maturation of solidified/stabilized mixtures of contaminated sediment with fly ash and lime. The effects of ageing on the microstructural properties and chemical integrity of mixtures were studied for 7 days, 28 days, and 7 years using scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), X-ray diffraction analysis (XRD), and DIN (German Standard Procedure for Water, Wastewater and Sediment Testing (Group S)) and TCLP (Toxicity Characteristic Leaching Procedure) leaching tests. The results of the microstructure and strength analysis showed that the use of fly ash and lime as binders promoted the permanent structural integrity of the sediment. The treated sediment with 20 wt% fly ash and 10 wt% lime (F20L10) achieved higher overall strength compared to the mixture containing only 30 wt% fly ash (F30). The speciation and redistribution of metals and As in the treated sediment mixtures during the long-term evaluation indicate a strong reduction in their mobility. This material can be considered environmentally friendly and can be used as a fill material in road construction. The investment and operating costs are justified in this solution for sediment management. However, it is important to monitor the produced material over time to ensure that it remains effective and sustainable in the long term.

Investigating the influence of particle size ranges on the physical, mineralogical, and environmental properties of raw marine sediment

Annually, over one billion cubic meters of sediments are dredged worldwide. The field of construction suffer shortage of natural resources, these sediments present a potential local resource in various regions. Amongst the sectors, road construction stands as the largest consumer of aggregates, making the recovery of sediments an appealing solution. The dredged sediments made of three phases: solid, liquid, and air. The solid phase contains both mineral and organic components, each with particle size ranges. Particle size is a well-known factor significantly impacting material characteristics.This study's primary objective is to compare sediment particle size ranges as sub materials, particularly focusing on their classification for sediment recovery in road construction. The preparation of sediments for characterization tests in this context necessitates specific drying procedures, prompting an investigation into the effects of drying methods. Three distinct drying techniques-air drying, freeze drying, and oven drying were employed.Particle size ranges were extracted from raw marine sediment and categorized based on the following diameter ranges: 2–0.4 mm; 0.4–0.180 mm; 0.180–0.063 mm; and < 0.063 mm. Comprehensive physical, environmental, and chemical characterizations were conducted. The pivotal findings of this study unequivocally reveal variations in the distribution of organic matter across these different fractions. Notably, the fine fraction exerts a substantial influence on material-level attributes, especially concerning environmental characterization. Moreover, the choice of sample drying method before testing introduces variable effects on the investigated attributes. environmental impact analyses using leaching tests indicated higher values of elements like Barium (Ba), Molybdenum (Mo), Fluoride (F), and Chloride (Cl) in sediment fractions below 0.063 mm. The DRX analyses appear that the fine fraction had few clay particles, and higher values measured on different test were associated with organic matter.

Effects of sediment dredging on freshwater system: a comprehensive review.

As a common geo-engineering method to control internal load of nutrients and pollutants, sediment dredging has been used in many freshwater basins and has achieved certain effects. However, dredging can disturb water bodies and substrates and cause secondary pollution. It negatively affects the water environment system mainly from the following aspects. Dredging suddenly changes the hydrological conditions and many physical indicators of the water body, which will cause variations in water physicochemical properties. For example, changes in pH, dissolved oxygen, redox potential, transparency, and temperature can lead to a series of aquatic biological responses. On the other hand, sediment resuspension and deep-layer sediment exposure can affect the cycling of nutrients (e.g., nitrogen, phosphorus), the release and valence conversion of heavy metals, and the desorption and degradation of organic pollutants in the overlying water. This can further affect the community structure of aquatic organisms. The aim of this paper is to analyze the relevant literature on freshwater sediment dredging, and to summarize the current knowledge of the potential environmental risks caused by the dredging and utilization of freshwater sediments. Based on this, the paper attempts to propose suggestions to mitigate these adverse environmental impacts. These are significant contributions to the development of environmentally friendly freshwater sediment dredging technologies.

Characterizing nitrogen dynamics and their response to sediment dredging in a lowland rural river

It is challenging to quantify nitrogen (N) balance in a lowland rural river covered by macrophytes due to its multiple N sources and complex cycling processes. In order to address the challenge, we developed a N-cycling model (River-N) for lowland rural rivers covered by macrophytes, and coupled it with Nitrogen Dynamic Polder (NDP) and Environmental Fluid Dynamics Code (EFDC) model. A two-year (2020–2021) dataset was used to calibrate and validate the coupled model. The coupled model was used to investigate a lowland rural river’s N imports, exports and its response to sediment dredging, and resulted in an acceptable performance for total N concentrations (TN) (R2 = 0.57). Our investigation conducted in the study river revealed a considerable N retention (difference between imports and exports) ability (955.5 kg yr−1). The river’s N imports were mainly from connected-river import (55.6 %), surrounding-polder export (31.4 %), sediment N release (7.4 %). N exports were mainly from connected-river export (59.0 %), denitrification (31.7 %) and macrophyte uptake (4.4 %). Compared with scenario without dredging, the rates of particulate nitrogen (PN) resuspension and settling increased, and the rates of ammonia nitrogen (NH4+) release, denitrification and macrophyte uptake decreased under the scenario with dredging. During dredging period, the rates of NH4+ release, PN resuspension, PN settling were 2.6, 7.0 and 4.3 times higher than that during pre-dredging period, respectively. The denitrification rate during dredging period was decreased to 43.5 % of that during pre-dredging period. Our investigation results implied that sediment dredging can be a pathway to remove high-N sediment, but did not necessarily decrease TN in river due to external N imports. Considering the critical role of macrophytes in N-cycling, macrophytes should be a critical component requiring our attention in water management practices.

Killing two birds with one stone: Preparation of ceramsite high-strength lightweight aggregate via co-sintering of dredged sediment and municipal solid waste incinerated fly ash

The disposal of dredged sediment (DS) and municipal solid waste incineration fly ash (MSWIFA) has become a notable concern. In this study, a novel ceramsite high-strength lightweight aggregate (HLWA) was developed by the co-sintering of DS and MSWIFA. The optimal HLWA (DS-10FA-1160) was synthesized using a mixture of 90 % DS and 10 % MSWIFA at 1160 °C. DS-10FA-1160 exhibited a high cylinder compressive strength (42.82 MPa) and negligible leaching concentrations of heavy metals (HMs). The “killing two birds with one stone” mechanism was adopted as follows: MSWIFA promoted the generation of strength enhancing phases (e.g., rankinite and amorphous phases) while phillipsite-K and the disconnected pore structure of DS-10FA-1160 steadily encapsulated HMs.

Assessing the weed infestation potential of dredged streambed sediments targeted for reuse in agricultural fields

One of the problematic outcomes of soil erosion is sedimentation in stream channels adjacent to agricultural areas. Excess sediments routinely dredged are subsequently dumped in the riparian zone, where the prolonged presence of dredged sediment piles threatens the eco-hydrological balance of the agricultural-riverine environments. Reusing dredged sediments as an amendment for adjacent agricultural fields may serve as an alternative solution. However, farmers are hesitant to use this material in their fields due to the potential for weed infestation, with the associated costs incurred by crop losses. Here, we investigate the potential for weed infestation associated with reusing dredged sediments in agriculture. The research findings validate farmers' concerns regarding the undesirable proliferation of weeds following soil amelioration with dredged sediments. We present a comprehensive protocol for assessing the necessity for weed management intervention, based on infestation potential of weeds, while specifically targeting the reduction of adverse effects caused by agricultural weeds.

Growing Salix spp. on heavy metal contaminated sediment (Oskarshamn, Sweden) as a joint phytoremediation and circular economy approach

The sediments of rivers or harbours have always been considered sinks for numerous heavy metals, pesticides, chemicals and contaminants of anthropogenic origin. The eco-friendly management of contaminated sediment have received attention due to their large-scale presence in harbour areas. Application of bioenergy crop species, such as Salix spp., have shown a strong potential for reducing heavy metals from the contaminated sediment. The aim of this study was to investigate the application of Salix spp. on contaminated dredged sediment and heavy metal accumulation and translocation patterns in different parts of plants. Two Salix cultivars (Wilhelm and Ester; commercially available in Sweden) were cultivated in contaminated sediment for 5 weeks in a field setting. Heavy metals (Cd, Cu, Pb, Ni and Zn) content in different plant parts (root, cutting, shoot and leaves) were analysed by using atomic absorption spectrophotometer (AAS). The result indicated that the root biomass production was negatively affected for both cultivars due to the contaminated sediment medium, even though no morphological symptoms were present. Both Cd and Cu net accumulation were found to be significantly higher in Ester cultivars. The low translocation of heavy metals in Salix spp. hints that accumulated heavy metals are stored in the root parts. Low translocation of heavy metals from contaminated sediments gives a strong potential for using a growth medium to utilize phosphorus (P) in the sediment from a circular economy and bioeconomy perspective.

Mechanical properties and shrinkage performance of one-part-geopolymer based on fly ash and micronized dredged sediments

This paper aims to study the drying and autogenous shrinkage of optimized One-Part-Geopolymer binders based on micronized dredged sediments and fly ash. Four One-Part-Geopolymer with 0, 15, 30 and 50% wt of sediments and fly ash were optimized by the variation of SiO2/Al2O3 molar ratio between 3; 3.5; 4; 4.5; 5. Findings shown that the sediments incorporation increases the mechanical strength and decreases the matrix pore size. This improvement is related to two phenomena: the fineness of the sediments which plays the role of nucleation zone in the matrix, and the coexistence of C-A-S-H and N-A-S-H gels as shown by the SEM-EDS. The reduction in the pore size of mortars with the addition of sediments leads to an increase in drying and autogenous shrinkage which have been linked to pore distribution rather than mass loss, unlike ordinary cementitious materials. However, the shrinkage values are still lower than the literature findings.

How sediment dredging alters phosphorus dynamics in a lowland rural river?

China's lowland rural rivers are facing severe eutrophication problems due to excessive phosphorus (P) from anthropogenic activities. However, quantifying P dynamics in a lowland rural river is challenging due to its complex interaction with surrounding areas. A P dynamic model (River-P) was specifically designed for lowland rural rivers to address this challenge. This model was coupled with the Environmental Fluid Dynamics Code (EFDC) and the Phosphorus Dynamic Model for lowland Polder systems (PDP) to characterize P dynamics under the impact of dredging in a lowland rural river. Based on a two-year (2020–2021) dataset from a representative lowland rural river in the Lake Taihu Basin, China, the coupled model was calibrated and achieved a model performance (R2>0.59, RMSE<0.04 mg/L) for total P (TP) concentrations. Our research in the study river revealed that (1) the time scale for the effectiveness of sediment dredging for P control was ∼300 days, with an increase in P retention capacity by 74.8 kg/year and a decrease in TP concentrations of 23% after dredging. (2) Dredging significantly reduced P release from sediment by 98%, while increased P resuspension and settling capacities by 16% and 46%, respectively. (3) The sediment-water interface (SWI) plays a critical role in P transfer within the river, as resuspension accounts for 16% of TP imports, and settling accounts for 47% of TP exports. Given the large P retention capacity of lowland rural rivers, drainage ditches and ponds with macrophytes are promising approaches to enhance P retention capacity. Our study provides valuable insights for local environmental departments, allowing a comprehensive understanding of P dynamics in lowland rural rivers. This enable the evaluation of the efficacy of sediment dredging in P control and the implementation of corresponding P control measures.

Assessment of harbor sediment contamination for a path to valorize dredged material

Annually, over one billion m3 of sediment are dredged worldwide to ensure safe access for ships to harbors. Dredged sediment from harbors, considered as waste, presents an interesting opportunity for sustainable development projects by valorizing it as construction material. Characterizing dredged material is a crucial step to confirm the feasibility of reusing marine sediment and identifying potential valorization pathways. However, previous studies have primarily focused on investigating dredged sediment properties at a physical, geotechnical, and mineralogical level, with limited analysis of the presence of chemical contaminants, despite their impact on assessing sediment quality as a substitute for construction aggregate. The aim of this paper is to evaluate the contamination of marine sediment dredged from Safi harbor, located in central Morocco in an urbanized and industrialized area. Determining the contaminant content in the sediment is a prerequisite for the valorization process. To achieve this objective, the chemical characteristics of sediment collected from six different sampling points are studied. On one hand, the concentrations of the following trace metals are measured: Cadmium (Cd), Arsenic (As), Chromium (Cr), Nickel (Ni), Lead (Pb), Copper (Cu) and Zinc (Zn). On the other hand, Total Petroleum Hydrocarbons (TPH) and Total Organic Carbon (TOC) are analyzed. The results show that the reference values for the studied contaminants are not exceeded at the sampling points located in the port access channel. These findings indicate the potential for valorizing dredged sediment as an alternative source of construction materials.

Characterisation, remediation and valorisation of contaminated sediments: a critical review

The constraints associated with the availability of huge amounts of natural resources for infrastructure and agricultural development call for the reuse and recycling of anthropogenically created geomaterials, which is in line with the UN Sustainable Development Goals. In this context, valorisation of dredged sediments (DSs), obtained from water bodies such as rivers, lakes and oceans, as a resource material is worth considering. Unfortunately, DSs might be contaminated and exhibit a higher moisture-holding capacity due to higher contents of organic matter and clay minerals/colloids. These attributes pose a serious question towards dumping of DSs in the deep sea (in the case of marine sediments), a practice that prevails presently despite endangering marine life. Hence, the way forward would be to characterise them holistically, followed by adequate treatment to make them ecologically synergetic before developing a strategy for their valorisation. In this regard, many studies have been focused on the characterisation and treatment of DSs to make them an environmentally safe man-made resource. With this in mind, a critical synthesis of the published literature pertaining to the (a) characterisation; (b) treatment, remediation and immobilisation of contaminants; and (c) utilisation of DS was conducted, and the salient findings are presented in this paper. Based on this study, it was observed that DS acts as a sink for emerging contaminants for which no remediation strategies are available. Moreover, the study emphasised the lacuna in upscaling the existing treatment and stabilisation techniques to field conditions while highlighting the concept of circular economy.

Reed restoration decreased nutrients in wetlands with dredged sediments: Microbial community assembly and function in rhizosphere

Using dredged sediments as substrate for aquatic plants is a low-cost and ecological friendly way for in situ aquatic ecological restoration. However, the limited information available about how aquatic plant restoration affects the microbial ecology and nutrients in dredged sediments. In this study, nutrient contents, enzyme activities, and bacterial and archaeal communities in vertical sediment layers were determined in bulk and reed zones of wetlands constructed with dredged sediments in west Lake Taihu for three years. Reed restoration significantly decreased total nitrogen, total phosphorus, and organic carbon contents and increased alkaline phosphatase, urease, and sucrase activities compared to bulk area. Bacterial communities in vertical sediment layers had higher similarity in reed zone in comparison to bulk zone, and many bacterial and archaeal genera were only detected in reed rhizosphere zones. Compared with the bulk zone, the reed restoration area has a higher abundance of phylum Actinobacteriota, Hydrothermarchaeota, and class α-proteobacteria. The assembly process of the bacterial and archaeal communities was primarily shaped by dispersal limitation (67.03% and 32.97%, respectively), and stochastic processes were enhanced in the reed recovery area. Network analysis show that there were more complicated interactions among bacteria and archaea and low-abundance taxa were crucial in maintaining the microbial community stability in rhizosphere of reed zone. PICRUST2 analysis demonstrate that reed restoration promotes metabolic pathways related to C and N cycle in dredged sediments. These data highlight that using dredged sediments as substrates for aquatic plants can transform waste material into a valuable resource, enhancing the benefits to the environment.

PEMANFAATAN SEDIMEN SELOKAN SALURAN AIR DI DINOYO SURABAYA SEBAGAI CAMPURAN MEDIA TANAM GUNA MENDUKUNG URBAN FARMING YANG RAMAH LINGKUNGAN

Pengerukan sedimen oleh Dinas PU Bina Marga dan Pematusan Surabaya menghasilkan lumpur sedimen sebanyak 595.040 m3/tahun. Pemanfaatan sedimen dimaksudkan agar dapat menambah nilai potensi sedimen sebagai media tanam pertamanan atau pertanian kota, penelitian ini bertujuan untuk mengetahui pengaruh sedimen sebagai media tanam dengan mencampurkan hasil pengolahan limbah lainnya yakni kompos hijau sertacocopeat menggunakan variasi 1:1:1, 1:3:1, 1:5:1, uji vegetatif persemaian Capsicumfrutescens selama 2 minggu, dan respon terhadap penambahan pupuk NPK. Hasilpenelitian setelah dilakukan pretreatment pengeringan, penumbukan, pengayakanmenunjukkan perbandingan campuran terbaik adalah 1:1:1 dengan hasil akhir parameter C 3,58 %, N 0,31%, P 0,02%, K 1,63%, KTK 43,92 emol/kg, C/N 21, pH 8,55, tidak toksik dengan persentase penghambatan benih tumbuh 4%, pertumbuhan persemaian optimal dan kehilangan nutrisi yang lebih rendah. Penelitian menunjukkan sedimen dapat digunakan sebagai substrat campuran media tanam yang lebih ramah lingkungan dalam jangka panjang.

Analisis Volume Sedimen Terhadap Pendangkalan Di Dalam Saluran Primer Jaringan Irigasi (Studi Kasus: D.I. Cipicung Subang)

Research conducted in the primary canal of D.I Cipicung, Subang Regency, experienced damage to the irrigation network. Damage to the D.I Cipicung irrigation canal network in the primary canal, so that research is needed to find out how much silting volume is caused by sediment deposition in the irrigation canal. The method in this study uses a mathematical method to determine the volume of sediment deposition in the channel. The results show that the volume of sediment in the primary canal in the Cipicung D.I irrigation network is Vq Primary = 16.24 m3 (difference in depth 0.64 m) or 0.16% of the length per section 50.5 m of the total length of the primary canal 300 m and the change in the cross section of the primary channel is A = 1.25 m2 or 27.11%. So that the results of these calculations, it is necessary to resolve by repairing the right side of the canal lining with construction, the entrance channel from the river to the primary canal needs to be built a gate, dredging of sediment is required in the primary canal, and maintenance is required so that the canal is routinely once a week or once a month so that the strong channel is not quickly damaged.&#x0D; Keywords: Sediment Siltation, Primary Canal, Irrigation Network Damage.

Biochar amendment for reducing the environmental impacts of reclaimed polluted sediments

Dredging activities produce large amounts of polluted sediments that require adequate management strategies. Sediment reuse and relocation can involve several environmental issues, such as the release of CO2 and nitrogen compounds in the environment, the transfer of metals to plant tissues and the persistence of phytotoxic compounds. In this framework, the aim of the present work is to evaluate the use of biochar at different doses, in combination with plant growth, to reduce the environmental impacts polluted dredged sediments.Irrespective to the plant treatment, the amendment of the sediment with the lowest dose of biochar (3%) reduced by 25% the CO2 emissions of the substrate, by 89% the substrate carbon loss and by 35% the amount of nitrogen released into the environment (average values of the three plant treatments). The negative priming effect of biochar on organic matter mineralization can be responsible for the beneficial reduction of carbon and nitrogen release in the environment. The lack of similar effects observed at the higher biochar doses can depend on the low albedo of the biochar particles, causing the substrate warming (+1 °C for highest biochar dose) and accelerating the organic matter mineralization. Finally, shrub growth in combination with 3% biochar was able to offset the CO2 emission of the sediment and to reduce the amount of nitrogen lost.This work provides new insight on the potential benefit related to the biochar amendment of organic matter-rich dredged sediments, suggesting that the use of moderate dose of wood biochar in combination with shrub plantation can reduce the release of CO2 and nitrogen compounds in the environment.

Anthropogenic impact in and around Lake Coatetelco (south-central Mexico) from land use and landcover analysis between 1980 and 2020 CE

Land use/land cover (Lu/Lc) changes of last four decades (1980–2020 CE) helped to evaluate the anthropogenic impacts in surroundings of the Lake Coatetelco at central-south Mexico. Reduction in lake area during an interval of more precipitation between 1980 and 1989 CE reflected the perturbations such as dredging of lake bottom sediment, and a growth in lake area (ca. 1.3 km2) after 2010 CE suggested more sedimentation from enhanced erosion in the watershed due to 2.5-fold increase in built-up land with more growth dynamicity at NNW, WWN and WWS of the lake. It caused the influence of agricultural sector to decline by gaining from the crop land and (uncultivated) fallow land. Lack of correspondence between the total population and increasing urbanization could be an indicator of migration from this region due to climate change. This pilot study provided baseline data in a rural part of Mexico about some of the important changes occurred in and around a perennial lake for assessment of the short- and long-term anthropogenic impacts and planning for their mitigation.