Low Heavy Metal Research Articles

Co-Combustion of Municipal Sewage Sludge and Biomass in a Grate Fired Boiler for Phosphorus Recovery in Bottom Ash

Phosphorus has been identified as a critical element by the European Union and recycling efforts are increasingly common. An important phosphorus-containing waste stream for recycling is municipal sewage sludge (MSS), which is used directly as fertilizer to farmland. However, it contains pollutants such as heavy metals, pharmaceutical residues, polychlorinated bi-phenyls (PCBs) and nano-plastics. The interest in combustion of MSS is continuously growing, as it both reduces the volume as well as destroys the organic materials and could separate certain heavy metals from the produced ashes. This results in ashes with a potential for either direct use as fertilizer or as a suitable feedstock for upgrading processes. The aim of this study was to investigate co-combustion of MSS and biomass to create a phosphorus-rich bottom ash with a low heavy metal content. A laboratory-scale fixed-bed reactor in addition to an 8 MWth grate-boiler was used for the experimental work. The concentration of phosphorus and selected heavy metals in the bottom ashes were compared to European Union regulation on fertilizers, ash application to Swedish forests and Swedish regulations on sewage sludge application to farmland. Element concentrations were determined by ICP-AES complemented by analysis of spatial distribution with SEM-EDS and XRD analysis to determine crystalline compounds. The results show that most of the phosphorus was retained in the bottom ash, corresponding to 9–16 wt.% P2O5, while the concentration of cadmium, mercury, lead and zinc was below the limits of the regulations. However, copper, chromium and nickel concentrations exceeded these standards.

Assessment of water quality index and heavy metals in Sungai Bunus, Malaysia

Water Quality Index (WQI) is an indicator of water quality. The index is shown in classes where Class I indicates a Natural Level of water quality, Classes IIA/IIB, Class III and IV indicate the presence of a certain amount of pollutant, and Class V highly polluted water. Hence, this study was conducted to evaluate the current WQI and the extent of heavy metals present in Sungai Bunus, a river in Selangor, Malaysia, by Harkins’s Standardized Distances Method (HSDM). Water samples were taken six times between 24th October 2016 and 11th November 2016 at the upstream, middle stream and downstream of the Sungai Bunus. Five in situ tests and eight laboratory tests were conducted. The findings showed that the upstream of the Sungai Bunus was the cleanest, measured 63.40 % while the downstream the dirtiest, 39.97 %. Secondly, it showed that this river contained the lowest heavy metals in the upstream compared to the other parts. The upstream Harkins index was 12.17, the middle stream between 11.33 and 30.47, and the downstream 15.67 - 28.70. Cadmium, chromium, iron, and manganese were found in the river water, which exceeded the Raw Water Quality and Drinking Water Quality Standards. It was also found that the cadmium and chromium exceeded the highest permissible effluent standards B, where cadmium was 0.02 mg/L while chromium 0.05 mg/L. To improve the water quality of this river to the Class IIB standard, it is recommended that the Bunus Sewerage Treatment Plant (STP) be upgraded and the source of pollutions identified.

Arbuscular mycorrhizal fungal inoculation improves Nauclea orientalis L. growth dan phosphorus uptake in gold mine tailings soil media

Gold mine tailing soil media is characterized by low soil fertility and heavy metals toxicity. As an effort to improve the condition of gold mine tailing soil media, a revegetation experiment using Arbuscular Mycorrhizal Fungi (AMF) and soil media from gold mine tailing was conducted in the greenhouse. The objectives were to assess initial growth, P uptake and Pb reduction in Nauclea orientalis L. plants inoculated with indigenous AMF grown on gold mine tailing soil media. Three AMF fungi were used in this study, i.e. Glomus aggregatum , Glomus sp. and Acaulospora delicata. The experiment was conducted in Completely Randomized Design, having four treatments, i.e. control, G. aggregatum , Glomus sp. and A. delicata . The experiment was carried out for 3 months in a greenhouse scale. The results showed that local AMF inoculation significantly increased the height and stem diameter of lonkida by 181-213% and 284-443%, respectively, compared to control. The highest measurements of leaf’s length and width of lonkida seedlings were obtained from Glomus sp. and A. delicata treatments. Glomus sp. and A. delicata each significantly increased P levels in roots and shoots. Inoculation with G. aggregatum reduced Pb in the root and shoots parts by 74-86% and 72-76%, respectively, compared to controls. Local AMFs are potential to be developed as biological fertilizers to support revegetation in degraded lands, such as in gold mine tailing areas.

Spatio-temporal Index Based on Time Series of Leaf Area Index for Identifying Heavy Metal Stress in Rice under Complex Stressors.

Crops under various types of stresses, such as stress caused by heavy metals, drought and pest/disease exhibit similar changes in physiological-biochemical parameters (e.g., leaf area index [LAI] and chlorophyll). Thus, differentiating between heavy metal stress and nonheavy metal stress presents a great challenge. However, different stressors in crops do cause variations in spatiotemporal characteristics. This study aims to develop a spatiotemporal index based on LAI time series to identify heavy metal stress under complex stressors on a regional scale. The experimental area is located in Zhuzhou City, Hunan Province. The situ measured data and Sentinel-2A images from 2017 and 2018 were collected. First, a series of LAI in rice growth stages was simulated based on the WOrld FOod STudies (WOFOST) model incorporated with Sentinel 2 images. Second, the local Moran’s I and dynamic time warping (DTW) of LAI were calculated. Third, a stress index based on spatial and temporal features (SIST) was established to assess heavy metal stress levels according to the spatial autocorrelation and temporal dissimilarity of LAI. Results revealed the following: (1) The DTW of LAI is a good indicator for distinguishing stress levels. Specifically, rice subjected to high stress levels exhibits high DTW values. (2) Rice under heavy metal stress is well correlated with high-high SIST clusters. (3) Rice plants subjected to high pollution are observed in the northwest of the study regions and rice under low heavy metal stress is found in the south. The results suggest that SIST based on a sensitive indicator of rice biochemical impairment can be used to accurately detect regional heavy metal stress in rice. Combining spatial-temporal features and spectral information appears to be a highly promising method for discriminating heavy metal stress from complex stressors.

Congruously designed eco-curative integrated farming model designing and employment for sustainable encompassments.

Eco-degradative features associated with the modern agriculture due to utilization of toxic agro-chemicals and intensified technologies need an urgent attention. Considering this need for eco-curativeness and eco-efficiency, current has for the first time employed an integrated farming system (IFS) through designing an appropriate assemblage of vegetables, poultry, and fish (VPF) and investigated its applied scale practicability in addition to the its role in the enhancement of the productivity and environmental quality maintenance. The practical employment of VPF model resulted in the remarkable improvement of soil fertility through an increment in the essential nutrient quantity. Physicochemical analysis of the soils expressed an improvement in the treated samples, i.e., pH (7.31), EC (0.92dS/m), organic matter (2.97%), nitrogen (2.1mg/kg), phosphorous (120.3mg/kg), potassium (322mg/kg), calcium (1482.0mg/kg), and magnesium (471.5mg/kg). Furthermore, ecological detoxification was expressed in form of lower heavy metals (HM) in the experimental soils. At the early plantation stage, HM concentration in the soils modified with nutrient-rich water signified considerably lower pattern with trend, i.e., Cd < Zn < Ni <Pb< Cu < Fe. The morphological growth of the vegetable plants, i.e., Lycopersicon esculentum L., Capsicum annum, and Abelmoschus esculentus, and fish species, i.e., Lobeo rohita and Clarias gariepinus, in the current investigation was remarkably good. Currently employed VPF model expressed a duality in completion of sustainability goals through production of good-quality vegetables in addition to environmental integrity boosting by complete elimination of need for toxic chemical inputs. Results of this research can be adopted for large-scale employment for production of augmented agricultural production in a completely sustainable manner.

Effects of intercropping on cadmium uptake by maize and tomato

In order to explore the effect of intercropping on the uptake of heavy metal cadmium (Cd), pot experiments were undertaken using three different planting methods: monoculture, restrictive intercropping and intercropping. The effects of Cd accumulation in different plant parts, and their causes, were examined using a plant species regarded as a relatively high heavy metal accumulator (tomato: Lycopersicon esculentum var. Zhongshu 4) and a species regarded as a relatively low heavy metal accumulator (maize: Zea mays L. var. Jinzhumi). Cd levels for all experiments were 3.70 mg/kg. Results indicate that restricted intercropping and intercropping of tomato and maize increased the accumulation of Cd (from 13.52 mg/kg to 24.94 mg/kg and 27.30 mg/kg in tomato leaf, respectively). Compared with the control group, pH levels in soil surrounding tomato roots in the intercropped samples decreased and the activity of acid phosphatase increased, while the activity of urease decreased. Intercropping can also change the structure of the crop root microorganism population, increase the abundance of microbiological species that promote the uptake of heavy metals, and finally achieve high accumulation of Cd in tomatoes. Our research results provide reference for controlling soil heavy metal pollution and ensuring food safety by using an intercropping model.

Chemical Stabilization of Fly Ash from Medical Waste Incinerators

Fly ash from Medical Waste (MW) incinerators contains many toxic materials and requires appropriate treatment. In this work, a procedure for the stabilization of a fly ash produced by a MW incinerator is proposed. Firstly, a detailed characterization of the fly ash as received is presented. The European standard leaching test EN 12457/2 (2002) was used for the fly ash classification, and according to the results, the leachate concentration of Pb, Total Dissolved Solids (TDS), chloride and fluoride ions, exceeded the legal limit values for non-hazardous waste landfilling. A treatment method involving two processes, i.e., phosphoric acid stabilization followed by water washing, was applied for the stabilization of the MW fly ash. This method has been successfully applied for the stabilization of Municipal Solid Waste Incineration (MSWI) fly ash, and was modified in this study in order to be used for Medical Waste Incineration (MWI) fly ash treatment. Two modifications of this method were examined in order to effectively stabilize the ash and produce process wastewater with low heavy metal content. The use of 10% w/w phosphoric acid (acid to ash ratio) followed by water washing with a Liquid to Solid (L/S) ratio equal to 3:1 L kg−1 was found to successfully stabilize the MWI fly ash and produce a waste that can be disposed of in a non-hazardous landfill. Additional use of phosphoric acid provides no significant improvement of the wastewater quality.

Maximizing ammonium and phosphate recovery from food wastewater and incinerated sewage sludge ash by optimal Mg dose with RSM

Nitrogen (N) and phosphorus (P) removal and recovery as struvite from various waste streams have drawn much attentions for environmentally friendly and economically competitive fertilizer production. In this study, integrated approach of using food wastewater (FW) and incinerated sewage sludge ash (ISSA) as the alternative N and P sources and optimum Mg dosage were investigated for the first time to achieve maximal nutrient recovery as struvite (MgNH4PO4∙6H2O). Response surface methodology (RSM) successfully established the optimum condition for the maximum recovery of PO43−-P (97.7%), NH4+-N (74.8%), and Mg2+ (95.5%) as precipitate at pH 9.63 and molar ratio of PO43−-P:NH4+-N:Mg2+ of 1:0.6:1.59. The recovered precipitate mostly consists of struvite (72.6%) and shows high P-bioavailability (98.8%) with very low heavy metals content indicating a high performance fertilizer. Moreover, economic analysis highlights that the struvite production pathway could gain $149.1/m3 of FW to move forwards for economical struvite production.

Low-cost modified reactor to produce biochar and clamshell as alternative materials from acid mine drainage problem solving

Industrial activities and the natural oxidation of metallic sulphide-ores produce sulphate-rich waters with low pH and high heavy metals content generally termed Acid Mine Drainage (AMD). This is of great environmental concern, as some heavy metals are highly toxic. Within several possibilities, biochar and clamshell is an attractive option to treat AMD and to recover metals. This study aims to describe a simple method to utilized waste of both. Pyrolysis of waste material used to change waste to biomaterial biochar and clamshell. This research showed that biochar and clamshell are potentials material to reduce AMD impacts. This research will help and acceptable for rural areas to solve AMD problems.

Developing an Integrated Nuclear Waste Management Strategies on Aggregate Orphan Source Radioactive Materials in the Oil and Gas Sector.

Orphan sourced radioactive waste materials associated with oil and gas exploration, exploitation and production have been identified as causal factors in environmental health risks of operation personnel and the host communities in the Niger Delta. These Technologically Enhanced Radionuclides such as 14C, 40K, 87Rb, 232Th, 288U and some low frequency radioactive heavy metals constitute potential dangers to environmental health assay. Highly Sensitive Radiation Detection Tracers (HSRDT) were deployed for tracking and analysis of ionized leakages in the coastal marine offshore and shallow offshore areas in in a typical deltaic region. The inverse determination technique of the generalized half-life period was integrated into the model equations 1 – 12. Table 1 is a survey from 1992 t0 2015, showing that some identified radionuclides are reactive and contaminants to the surrounding environment from oil and gas processes. However, inadequate strategic decommissioning activities are responsible for severe occupational and environmental hazards to flora and fauna. This paper is fundamental to developing an integrated orphan waste management system as remedial techniques to minimize radiation waste burns and other harmful environmental effects on personnel and the environment. Its application is useful for decision-making on radioactive waste material management strategy. Furthermore, possible conceptual legal framework and standards for the disposal system of orphan sourced radionuclides in the petroleum sector could be explored. Keywords: Radioactive Waste Materials; Aggregate Orphan–Sourced Radionuclides; Environment Management; Waste Disposal Systems; Oil and Gas Sector etc.

Heavy metals in alluvial gold mine spoils in the peruvian amazon

Alluvial gold mining in the Peruvian Amazon has become a key driver of land degradation and deforestation. The associated release of mercury in the environment poses direct human health risks and is likely to engender cascading effects throughout local food chains. We carried out research in an alluvial gold mine concession in the Madre de Dios region to compare the degree of soil-borne pollution of heavy metals in areas where mining operations were abandoned more and less recently (1–5 and 6–8 years ago, respectively) with non-impacted old-growth forest areas. All heavy metals, were below permissible levels according to Peruvian and Canadian environmental quality standards. Mean As, Ba, Pb, Cu, Cr, Ni, V and Zn concentrations in impacted areas were 1.90 ± 1.51, 29.80 ± 22.87, 4.60 ± 2.55, 12.68 ± 8.13, 7.90 ± 3.98, 7.93 ± 3.89, 12.67 ± 6.62, and 26.65 ± 13.53 mg kg−1 dry matter (DM), respectively. Heavy metal concentrations were higher in non-impacted old growth forest soils than in mining spoils, and tended to increase with time since abandonment of mining operations. Hg was not detected in any of the sites. Low heavy metal concentrations in mine spoils might beexplained because of intense volatilization, reduced metal retention capacity due to the low clay and organic matter content, and leaching processes related with soil rinsing which is part of the mining operations combined with intense rainfall. Our findings suggest that heavy metal concentrations in mining spoils should not be considered to constrain forest restoration efforts or the development of similar land uses as in comparable non-impacted high forest soils.

Humic-like substances extracted from different digestates: First trials of lettuce biostimulation in hydroponic culture

Digestate valorization is a key challenge for the feasibility of Anaerobic Digestion plants. In this study, humic-like substances (HLS) extracted from two digestates (sewage sludge and manure) were used for the biostimulation of hydroponic cultures of Lactuca sativa (lettuce) at different doses and compared to a commercial reference of leonardite HLS. Aerial biomass increase averages ranged from 7 to 30 %, but the results presented a high coefficient of variation (around 20 %). The commercial reference did not present statistically significant biomass yield improvement. The application of manure digestate extract at the higher fulvic-like acids dose (4.6 mg/L of dissolved organic carbon) presented the best and most significant results compared to the blank (Hoagland's solution only). However, this result cannot be strictly dissociated from the supplementary amounts of nutrients brought by the extracts. Additionally, all the products presented low heavy metal content compared to the recent EU regulation for biostimulants (2019/1009). This preliminary study confirmed the interest of extracting HLS from two digestates for application as biostimulants, shedding light on a new perspective for digestate valorization.

Neuroprotective effect of Costus afer on low dose heavy metal mixture (lead, cadmium and mercury) induced neurotoxicity via antioxidant, anti-inflammatory activities

Humans are constantly exposed to heavy metals due to their ubiquity in the environment. Hence, this study investigated the possible protective effect of Costus afer aqueous leaf extract (CALE) against low dose heavy metal mixture (LDHMM)-induced neurotoxicity. Male albino rats were divided into 6 equal groups. Group 1 served as the normal control receiving only deionized water. Group 2 served as the toxic control receiving on metal mixture (20 mg/kg PbCl2, 1.61 mg/kg CdCl2 and 0.40 mg/kg HgCl2), groups 3, 4 and 5 were co-treated with metal mixture and CALE (750, 1500 and 2250 mg/kg body weight, respectively) and group 6 was treated with metal mixture and ZnCl2. All treatments were administered through oral gavage for 90days. Oxidative stress biomarkers [malondialdehyde (MDA), superoxide dismutase (SOD), glutathione content (GSH) and catalase (CAT)], inflammatory cytokines [interlukin-6 (IL-6) and interlukin-10 (IL-10)], histopathological changes and heavy metal concentration were determined in brain of rats. Results indicated that LDHMM significantly increased (p < 0.05) the lipid peroxidation marker (MDA) and the pro-inflammatory cytokine (IL-6), while lowered levels of the oxidative biomarkers (SOD, CAT and GSH) and anti-inflammatory cytokine (IL-10). Also, LDHMM caused some histopathological changes such as reactive gliosis and glia cell proliferation. LDHMM elevated the lead, cadmium and mercury concentrations in the brain. Severity of the distorted cortical parameters were ameliorated by CALE administration. The CALE induced significant protective effect on LDHMM-mediated neurotoxicity in a dose-dependent manner which may be a result of its antioxidant anti-inflammatory and metal chelation mechanisms.

Very-long-chain fatty acids (VLCFAs) in plant response to stress.

Plant growth is affected by various stresses leading to changes in metabolism. Stress conditions include a variety of biotic and abiotic factors such as pathogens, drought, high and low temperatures and heavy metals. Among multiple physiological responses to stress, there is an adaptive modification in membrane lipid constituents. In particular, the composition of membrane very-long-chain fatty acids (VLCFAs) changes both qualitatively and quantitatively. Here, we evaluate the current data on the effects of stress on plant VLCFAs composition. In summary, some stress conditions lead to an increase of the total amount of saturated and, in certain cases, unsaturated VLCFAs. Currently, it is not completely clear how these molecules participate in the biology of plant cell membranes. Their possible functional roles are discussed.

Physico-chemical properties of peatland located in the impact zone of municipal landfill

The results of studies of peat located in the impact zone of municipal landfill are presented. It is established that according to the peat genetic horizons profile the distribution of the mobile fractions of heavy metals is manifested in a gradual decrease with depth. The content of heavy metals (manganese, copper, zinc, lead, cobalt, mercury) in the peat does not exceed the MAC, except for cadmium, which is spread by waste from the landfill. The source of cadmium in landfills is waste containing lacquers and paints, fluorescent lamps, batteries etc. Cadmium sulfide is the basis for yellow paints used in vehicle dyeing, textile production, soap making. Peat is characterized as very poor in micromycetes distribution. Some micromycetes detected are indicators of high mineral content and low heavy metal content. Analysis of peat micromycetes by growth rate showed that the slowest growing micromycetes owns the largest proportion - 70%. The distribution by color showed that dark-colored micromycetes of the Moniliaceae, characterized by toxicity, predominate. According to the humus reserve, peat is slightly humus. It is not recommended to use such peat for crop cultivation. Instead, peat can be a source of fuel under conditions of industrial development and compliance with existing rules and state standards.

Bitkilerde Abiyotik Stres Toleransında Etkili Olan Moleküllere Örnek Olarak Eksojen Salisilik Asit Uygulamaları

Endojen ve eksojen faktörlere bağlı olan bitki büyüme ve gelişmesi; kuraklık, tuz, yüksek ve düşük sıcaklık derecesi, radyasyon ve ağır metaller gibi abiyotik stres faktörlerinden büyük ölçüde etkilenmektedir. Bitkilerde stresle başa çıkma, olumsuz koşullarda hücre metabolizmasında değişikler yapılması ve savunma mekanizmalarının harekete geçirilmesi ile gerçekleşmektedir. Salisilik asit (SA) bitkilerde bu mekanizmaları harekete geçiren moleküllerden biri olup, özellikle patojen saldırılarına karşı cevap oluşturulmasında etkili olan, içsel bir bitki büyüme düzenleyicisidir. Fenolik bir bileşik olan ve bir bitki hormonu olarak da tanımlanan SA, stres koşulları altında sinyal molekülü olarak görev alarak bitkinin stres koşullarında oluşturduğu cevabı düzenlemekte ve hayatta kalmasını sağlamaktadır. Özellikle eksojen SA uygulamalarının bitkilerde patojenite ile ilişkili genleri aktive ederek hastalıklara direnç sağladığı bilinmektedir. Dışarıdan uygulanan SA‘in biyotik stres faktörleri yanında abiyotik stres faktörlerine karşı da bitkinin toleransını artırdığını gösteren çok sayıda çalışma bulunmaktadır. Eksojen SA uygulamaları domates, biber, mısır ve fasulye gibi farklı bitkilerde uygulanmış ve tuz, yüksek ve düşük sıcaklık, kuraklık ve ağır metal streslerine cevap oluşturmada etkin olduğu belirlenmiştir. Buna karşın bazı çalışmalarda eksojen SA uygulamalarının bazı bitki türlerinde vejetatif ve biyokimyasal içeriklerde inhibe edici özelliğinin bulunduğunun gösterilmesi; SA etkilerinin uygulama dozu, bitki türü ve uygulanma şekline bağlı olarak değişebileceği sonucunu vermektedir.

Effect of Land Use Conversion on Surface Soil Heavy Metal Contamination in a Typical Karst Plateau Lakeshore Wetland of Southwest China.

Land use conversion could directly or indirectly influence heavy metal geochemistry by changing soil properties. The aim of this study was to explore the effect of land use conversion on surface soil heavy metal contamination in the karst plateau lakeshore wetlands of Southwest China. Based on this, a total of 120 soil samples were collected from 30 sites from different types of land uses (farmlands, grasslands and woodlands) around a lake in Suohuangcang National Wetland Park in August 2017. Contents of As, Cd, Cu, Cr, Hg, Pb and Zn were analyzed, and soil heavy metal contamination was assessed in all three land use types. Results showed that land use transformation from farmland to grassland or woodland was not conducive to the release of soil heavy metal. Surface soil of all three land use types have been moderately polluted by As, Cr, Pb, and Zn, and grassland and woodland also had moderate Cd contamination. The pollution load index (PLI) results revealed low heavy metal contamination in grassland and woodland but no contamination in farmland. Although the integrated contamination in the studied region did not pose a serious potential ecological risk (RI < 150), it might affect human health through the water supply and food chain. Therefore, it is necessary to monitor and control As, Cd, Cr, Pb, and Zn concentrations of surface soil through controlling pollutants, improving waste treatment, as well as strengthening supervision and management in the vicinity of the Suohuangcang National Wetland Park.

El color del polvo urbano como indicador de contaminación por metales pesados

<div><strong>Introduction:</strong> Urban dust contains heavy metals (HMs) that pose a risk to human health.</div> <div><strong>Objective:</strong> To evaluate the color of urban dust as an indicator of HM pollution. </div> <div>Materials and methods: Color and HMs (Ba, Cr, Cu, Pb, Mn, Ni, V and Zn) were measured in 455 dust samples, and redness and saturation rates were calculated. Based on color, groups of samples were formed using cluster analysis. Multiple regression analysis between HMs and indices by color groups was performed, as well as a Kruskal-Wallis analysis of HMs by color groups.</div> <div><strong>Results and discussion:</strong> Urban dust samples were classified as dark grayish brown (I), dark gray (II), dark olive brown (III), very dark gray (IV), grayish brown (V) and black (VI). Multiple linear regressions between color indices and HMs showed high and significant correlation (P < 0.05) in groups I, II, III and IV. Urban dust HMs were generally found in the order Zn > Mn > Ba > Pb > Cu > Cr > Ni > V. Also, Cr, Cu, Ni, Pb and Zn showed significant differences (P < 0.05) among the color groups; the samples from very dark gray to black were the most polluted, and those of dark grayish brown had lower HM contents. </div> <div><strong>Conclusions:</strong> Urban dust color is an indicator of heavy metal pollution in Mexico City. </div>

Mid‐term effects on ecosystem services of quarry restoration with Technosols under Mediterranean conditions: 10‐year impacts on soil organic carbon and vegetation development

The use of Technosols for the restoration of limestone quarries overcomes the usual “in situ” scarcity of soil and/or its poor quality. The use of mine spoils, improved with mineral and/or organic amendments, could be an efficient and environmentally friendly option. Properly treated sewage sludge from urban wastewater treatment plants could be a suitable organic amendment and fertilizer (rich in N and P) whenever its pollutant burden is low (heavy metals and/or organic pollutants). Its appropriate use could improve essential soil physical and chemical properties and, therefore, promote key ecosystem services of restored areas, such as biomass production and carbon sequestration, as well as biodiversity and landscape recovery. However, the mid‐term impacts of these restoration practices on soil functioning and their services have rarely been reported in the available literature. In this study we assess the mid‐term effects (10 years) of the use of sewage sludge as a Technosol amendment on soil organic carbon (SOC), nutrient status, and plant development in several restored quarries. Soils restored using sewage sludge showed a threefold increase in SOC compared to the corresponding unamended ones, despite the moderate sludge dosage applied (below 50 tonnes/ha). Plant cover was also higher in amended soils, and recruitment was not affected by sludge amendment at these doses. This study demonstrates that, used at an appropriate rate, sewage sludge is a good alternative for the valorization of mine spoils in quarry restoration, improving some important regulatory ecosystem services such as carbon sequestration, without compromising woody plant encroachment.

Thermal hydraulics modeling of On-line refueling for the Advanced High Temperature Reactor (AHTR)

As part of the effort to move forward the Fluoride salt-cooled High-temperature Reactor (FHR) technology, the Advanced High Temperature Reactor (AHTR) is being developed at Oak Ridge National Laboratory (ORNL) and several other institutions. Due to its plank fuel design and inherently low heavy metal loading, which challenges fuel utilization, online refueling is considered as an option for improving the economic viability of this reactor.This work presents the thermal hydraulic modeling of the online refueling for the AHTR. Analyses at the single channel and fuel assembly level have been performed in order to develop a model of the reactor. The reactor modeling has been integrated with CFD studies for characterizing the steady state conditions and the refueling transient. The simulations of the transient have been complemented by the analysis of the stability of the refueling operation.This work demonstrates the viability of online refueling from a thermal hydraulic standpoint and develops a modeling approach for this type of operational transient.