Remediation System Research Articles

Application of slow-releasing green denaturing colloidal substrates to contain and bioremediate hexavalent-chromium plume

Chromium (Cr) is a major heavy metal pollutant that has been found in many groundwater-polluted sites. The effectiveness of hexavalent chromium [Cr(VI)] plume containment and remediation via the bioreduction and adsorption mechanisms were evaluated in this study using the developed green slow-releasing denaturing-colloidal substrates (G-SDS). The major components of G-SDS were gelatin, agar, and cane molasses (optional), and weight ratios for gelatin and agar were 3 and 0.5%, respectively. Gelatin was used for slow carbon release and Cr(VI) adsorption, cane molasses was applied for rapid carbon release, and agar was used as the solidifying agent to form G-SDS. Environmental scanning electron microscope analyses indicate that the G-SDS had a rigid and stable 3-D structure with irregular and rippled surface and staged sheets, which created significant surface areas for Cr(VI) adsorption. Results from the column study show that more than 98% of Cr(VI) was removed with increased Cr(III) concentrations in column effluents. The G-SDS could form a permeable and reticulated fiber biobarrier after its injection for Cr(VI) adsorption. The released carbon substrate from G-SDS could subsequently enhance Cr(VI) bioreduction mechanisms. The released amine from gelatin could react with water and produce ammonia, which could neutralize the acidified water due to the produced organic acids from G-SDS fermentation. The microbial communities in column soils were characterized by the next-generation sequencing technology. G-SDS supplement caused the variations in microbial diversities and predominant bacteria. The released carbon from G-SDS resulted in the formation of anaerobic conditions , and thus, the growth of the Cr(VI) reducer was enhanced. G-SDS could serve as a source of primary substrate for Cr(VI) bioreduction. The dominant groups of bacterial communities include Acinetobacter, Bacillus sp., Clostridium , Desulfovibrio, and Geobacter . Both G-SDS and column soils contained significant amounts of Cr(III) after the column experiment indicating that the adsorbed Cr(VI) within G-SDS was bioreduced to Cr(III). Moreover, Cr(OH) 3 was formed and precipitated in soils after Cr(VI) bioreduction. Results indicate that the passive biobarrier system containing G-SDS can be used as an economically and practically acceptable remedial system to contain the Cr(VI) plume and reduce the environmental risks caused by Cr(VI). G-SDS can enhance Cr(VI) removal via the development of bioreduction, adsorption, and precipitation mechanisms. • The developed G-SDS can remove Cr(VI) via the bioreduction and adsorption. • G-SDS forms semi-solidified colloid for slow and long-term carbon release. • Cr(OH) 3 is formed and precipitated after Cr(VI) bioreduction. • Dominant CRB include Acinetobacter, Bacillus , Clostridium, Desulfovibrio and Geobacter. • Released amine from G-SDS can produce ammonia, which has the buffering capacity.

Protection of Personal Information in Government Information Disclosure Based on the Administrative Regulation Perspective

Personal information protection is the focus of data security governance, while government information disclosure is a practical need for government administration in the context of the information age. As a public authority, the government's disclosure of information is effectively regulated by the administrative law. The revised Regulation of the People's Republic of China on the Disclosure of Government Information protects personal information mainly in terms of administrative procedures for seeking consent, administrative supervision of information disclosure departments, and administrative remedies for infringement of personal information. However, it still faces problems such as low level of legislation, irregular enforcement procedures, lack of supervision, and imperfect supervision and remedy systems. The future protection of personal information needs to further improve the path of administrative regulation of government information disclosure, make up for the shortcomings in legislation and supervision, improve the consultation system of prior notification and information disclosure as well as continue to follow the principle of procedural due process.

The Development of a New Chemically Resistant Sprayed Mixture

This paper deals with research and development of a new chemically resistant sprayed mixture based on portland cement and special admixtures. The new material will be part of a comprehensive remediation system for the remediation of chemically attacked and stressed sewer structures. The aim of this work is to verify the effect of the amount of crystalline waterproofing admixture on selected physical-mechanical characteristics and chemical resistance, specifically resistance to the attack of sulphate solution and the attack of aggressive biogenic sulfuric acid solution. Furthermore, the resulting characteristics of test specimens manufactured in the laboratory and test specimens made by spraying into boxes and subsequent cutting to the required dimensions were compared. Due to the fact that there is currently no official methodology in the Czech Republic for testing the chemical resistance of cementitious materials intended for sewage environments, the methodology was used in accordance with DIN 19573 "Draft on mortars for construction and rehabilitation sewer systems". The sulphate resistance was determined for test specimens measuring 160×40×10mm, which were exposed to a solution of sulphate salts with a concentration of 29.8g / l (44g/l Na2SO4) for 91days. To determinate the resistance to biogenic sulfuric acid, special tanks were assembled in which the test specimens, measuring 80×40×40mm, were exposed for 14 days to a solution of sulfuric acid (H2SO4) with a molar concentration of 1,0mol/l (pH=0). The results of this work show the optimal amount of crystalline waterproofing admixture. The results of this work will be used in the next phase of research, when cement and some fillers will be substituted by selected secondary raw materials, namely to improve or at least maintain the key characteristics of the final sprayed mixture. Keywords: Sprayed mixture, Sulphates, Biogenic sulfuric acid, Chemical resistance, Crystalline waterproofing admixture

Insights into rhamnolipid amendment towards enhancing microbial electrochemical treatment of petroleum hydrocarbon contaminated soil

Environmental pollution by hydrophobic hydrocarbons is increasing, notably nowadays due to a large amount of industrial activity. Microbial electrochemical technologies (MET) are promising bio-based systems which can oxidize hydrophobic hydrocarbon pollutants and produce bioelectricity simultaneously. However, MET faces some issues in terms of soil remediation, including low mass transfer, limited electro-activity of anodes as electron acceptors, low bioavailability of hydrocarbons, and the limited activity of beneficial bacteria and inefficient electron transport. This study aims to investigate the role of the addition of rhamnolipid as an analyte solution to the MET to enhance the efficacy and concurrently solve the abovementioned issues. In this regard, a novel long chain of RL was produced by using low-cost carbon winery waste through non-pathogenic Burkholderia thailandensis E264 strains. Different doses of RL were tested, including 10, 50, and 100 mg/L. A maximum enhancement in the oxidation of hydrophobic hydrocarbons was found to be up to 72.5%, while the current density reached 9.5 Am-2 for the MET reactor having a dose of 100 mg/L. The biosurfactants induced a unique microbial enrichment associated with Geobacter, Desulfovibrio, Klebsiella, and Comamona on the anode surface, as well as Pseudomonas, Acinetobacter, and Franconibacter in soil MET, indicating the occurrence of a metabolic pathway in microbes working with the anode and soil bioelectrochemical remediation system. According to cyclic voltammetry analysis, redox peaks appeared, showing a minor shift in redox MET-biosurfactant compared to the bare MET system. Furthermore, the phytotoxicity of polluted soil to L. sativum seeds after and before MET remediation shows a decrease in phytotoxicity of 77.5% and 5% for MET-biosurfactant system and MET only, respectively. With MET as a tool, this study confirmed for the first time that novel long-chain RL produced from non-Pseudomonas bacteria could remarkably facilitate the degradation of petroleum hydrocarbon via extracellular electron transfer, which provides novel insights to understand the mechanisms of RL regulating petroleum hydrocarbon degradation.

A Generic Closed-Loop Contaminant Treatment System Package for MODFLOW 6.

We present a contaminant treatment system (CTS) package for MODFLOW 6 that facilitates the simulation of pump-and-treat systems for groundwater remediation. Using the "nonintrusive" MODFLOW 6 application programming interface (API) capability, the CTS package can balance flows between extraction and injection wells within the outer flow solution loop and applies blended concentration/mass treatment efficiency within the outer transport solution loop. The former can be important when the requested extraction rate cannot be satisfied by the current simulated groundwater system conditions, while the latter can be important for simulating incomplete/imperfect treatment schemes. Furthermore, the CTS package allows users to temporally vary all aspects of a simulated CTS system, including the configuration and location of injection and extraction wells, and the CTS efficiency. This flexibility combined with the API-based implementation provide a generic and general CTS package that can be applied across the wide range of MODFLOW 6 simulation options and that evolves in step with MODFLOW 6 code modifications and advancements without needing to update the CTS package itself.

Supercritical fluid remediation for soil contaminants: Mechanisms, parameter optimization and pilot systems

Soil contamination is one of the major sustainable development issues which requires increasing efforts from multidisciplinary collaborations. In recent years, supercritical fluid remediation has been proposed as one “green technology” that is suitable with various types of contaminants without destroying the soil nature. Supercritical fluid process employs the high solubility and zero surface tension of supercritical states as well as the large solubility variations in the supercritical region for high efficiency separation. In this analysis, characteristics of soil contaminants in representative “matrix” conditions and related effects on remediation process with supercritical fluid technology are analyzed. Mechanisms and procedures of supercritical remediation technology are summarized and compared for different contaminants. Operation conditions, flow design, processing time and the entrainer applications in supercritical fluid remediation systems are shown to act more as coupled parameter groups rather than single-parameter controlled system. From a summary of existing remediation prototypes, a remediation efficiency around 80 % were shown. It is recommended that large-scale remediation trials be operated and optimized soon.

Improved precision in As speciation analysis with HERFD-XANES at the As K-edge: the case of As speciation in mine waste.

High-energy-resolution fluorescence-detected (HERFD) X-ray absorption near-edge spectroscopy (XANES) is a spectroscopic method that allows for increased spectral feature resolution, and greater selectivity to decrease complex matrix effects compared with conventional XANES. XANES is an ideal tool for speciation of elements in solid-phase environmental samples. Accurate speciation of As in mine waste materials is important for understanding the mobility and toxicity of As in near-surface environments. In this study, linear combination fitting (LCF) was performed on synthetic spectra generated from mixtures of eight measured reference compounds for both HERFD-XANES and transmission-detected XANES to evaluate the improvement in quantitative speciation with HERFD-XANES spectra. The reference compounds arsenolite (As2O3), orpiment (As2S3), getchellite (AsSbS3), arsenopyrite (FeAsS), kaňkite (FeAsO4·3.5H2O), scorodite (FeAsO4·2H2O), sodium arsenate (Na3AsO4), and realgar (As4S4) were selected for their importance in mine waste systems. Statistical methods of principal component analysis and target transformation were employed to determine whether HERFD improves identification of the components in a dataset of mixtures of reference compounds. LCF was performed on HERFD- and total fluorescence yield (TFY)-XANES spectra collected from mine waste samples. Arsenopyrite, arsenolite, orpiment, and sodium arsenate were more accurately identified in the synthetic HERFD-XANES spectra compared with the transmission-XANES spectra. In mine waste samples containing arsenopyrite and either scorodite or kaňkite, LCF with HERFD-XANES measurements resulted in fits with smaller R-factors than concurrently collected TFY measurements. The improved accuracy of HERFD-XANES analysis may provide enhanced delineation of As phases controlling biogeochemical reactions in mine wastes, contaminated soils, and remediation systems.

A novel BC-HMRPGPB-plant system for remediation of low concentration Cd in soil: The process of metal migration and microbial community evolution

HMs are bioaccumulative and non-biodegradable toxicants and can generate serious health risks to living organisms. The threat of low concentrations of HMs in soils is often overlooked. The BC-HMRPGPB-Plant association can provide a feasible green approach for remediation of HM-contaminated sites with low concentrations. In this study, strain AP-3 showed a high tolerance to several metals and exhibited the excellent biosorption for Cd. Then, the strain AP-3 was successfully immobilized on BC by physical adsorption method and functional groups (hydroxyl and carbonyl groups) between BC and AP-3 surface. We discover that encapsulation of BCS with sodium alginate helped microorganisms to resist interference from external HMs. SABCS can effectively improve soil properties, which further facilitated the plant growth and accumulation of HMs in plant roots. The treatment of SABCS reduced the accumulation of metals in edible tissues by 25% compared to the control, which greatly reduced the risk of consumption. The migration of HMs by the BC-HMRPGPB-Plant system was bottom-up process. The activities of S-CAT, S-DHA, S-UE and S-PPO were significantly increased after the bioremediation, which further promoted the biosorption of HMs by plants. Furthermore, BC-HMRPGPB-Plant system alleviated the toxicity of HMs to rhizobacteria and facilitated the accumulation of HMs in the roots. Ultimately, the strain was successfully colonized in the rhizosphere and soil microbial community was not significantly altered after bioremediation. Our study provided that a feasible pathway for the BC-HMRPGPB-Plant system to remediate HM-contaminated sites.

Transfer of trace organic compounds in an operational soil-aquifer treatment system assessed through an intrinsic tracer test and transport modelling.

Soil Aquifer Treatment (SAT) can provide supplementary treatment of trace organic compounds (TrOCs) such as pharmaceutical and industrial compounds present in Secondary Treated Wastewater (STWW). Concern on presence of unregulated TrOCs in natural systems has raised recently as well as the interest in SAT systems for remediation. The present study quantifies, at the field scale over35 m of lateral groundwater flow, the effectiveness of the Agon-Coutainville SAT system (Manche, Normandy, France) for TrOCs removal by sorption and biodegradation through monitoring of seven TrOCs (oxazepam, carbamazepine, benzotriazole, tolyltriazole, caffein, paracetamol, ibuprofen) and major inorganic compounds as intrinsic tracers in STWW and groundwater during a 34-day STWW infiltration experiment during operational use of the SAT. Cationic exchanges and mixing between groundwater and STWW during the experiment were highlighted by major ions and geochemical simulations. Due to the low thickness of the unsaturated zone, a 1D analytical solution of the advection-dispersion equation (ADE) was applied on chloride data. Chloride was used as conservative intrinsic tracer to calibrate the horizontal flow and transport parameters such as the aquifer dispersion coefficient (D) and the average pore water velocity (ν) allowing estimation of the groundwater residence time. Transport and attenuation of the TrOCs were simulated assuming first-order degradation constant (μ) and linear retardation coefficient (R), calibrated to simulate the observed temporal changes in the breakthrough of TrOCs. Sorption was found to play a role in the transport of TrOCs, notably for oxazepam with a higher linear retardation coefficient value of 2.2, whereas no significant differences of retardation were observed for carbamazepine, tolyltriazole, benzotriazole (1.37, 1.35, 1.36 respectively). Estimated first order degradation rate constants, between 0.03d-1 for carbamazepine and 0.09d-1 for tolyltriazole, were generally high compared to the literature, possibly due to favourable redox conditions and important microbial activities within the system. This study provides evidence of the efficiency of the Agon-Coutainville SAT system for the removal of TrOCs.

손해배상제도의 목적과 손해의 개념에 관한 연구

Among the various issues regarding the damage remedy system, the purpose and concept of the damage are the most fundamental ones that suggest a direction for how we should look at the damage in specific cases. Above all, regarding the purpose of the damage remedy system, the original one was the corrective justice, but in the contemporary welfare society, the distributive justice is being more and more emphasized. Our Civil Code pursues a fair and valid sharing of damage, which implies that the code accepts both corrective and distributive justices. Regarding the concept of damage, the Roman law did not clearly distinguish the contractual damage from the that of tort, but established the concept that the damage would involve violation and gain, and such concept would form the basis of the Medieval law and would also form the background of the damage in the contemporary civil laws. This study would review the concepts of the damage in German and French civil codes and then, discuss their concept in the US Tort. Specifically, this study examines the core disputes regarding the concept of the damage to better understand the core discussions of such concepts related with the concept of the damage as differential amount theory, normative concept of damage and foreseeability in an effort to make clear the discussions regarding the scope of the damage in Article 393 of our Civil Code. In particular, domestic majority of theories and judicial precedents adopt the Proximate casual relation theory as a criterion for decision on the scope of the damage, but Article 393 itself should function as criteria for decision on the scope of the damage. Hence, as the Paragraph 2 of Article 393 stipulates, it is judged that the foreseeability shall be the criteria for decision on the special damage, and that beside the principles of interest balancing and the foreseeability, other specific validity such as purpose of the norm should be considered for a fair distribution of the damage.

Effective BiOCl Electrons Collector for Enhancing Photocarrier Separation of Bi2WO6/BiOCl Composite

Enhancing photocarrier separation is a key step of photocatalysis, and in situ constructed composition interface is an advanced method to achieve this aim. Therefore, we report a face-to-face Bi2WO6/BiOCl (BWOC) which was synthesized via the continuous in situ ion-exchange method. As UV light is harmful to the human body, BWOC exhibits excellent photocatalytic activity only in visible light, and this is an important feature because visible light is a human-friendly operating condition. Under 50 W visible LED lamp illumination, unexcited BiOCl (BOC) only extracts electrons of excited Bi2WO6 (BWO), and holes remain on BWO, resulting in excellent photocarrier spatial separation efficiency through the face-to-face interface. This is why BWOC can be safe to use for the removal of hazardous substances. Compared with BWO and BOC, BWOC possesses 2.6 and 5.6 times higher photodegradation activity than RhB. This work provides a novel insight of efficient visible light photocatalytic system for environmental remediation.

Sustainable environmental remediation via biomimetic multifunctional lignocellulosic nano-framework

Chemical pollution threatens human health and ecosystem sustainability. Persistent organic pollutants (POPs) like per- and polyfluoroalkyl substances (PFAS) are expensive to clean up once emitted. Innovative and synergistic strategies are urgently needed, yet process integration and cost-effectiveness remain challenging. An in-situ PFAS remediation system is developed to employ a plant-derived biomimetic nano-framework to achieve highly efficient adsorption and subsequent fungal biotransformation synergistically. The multiple component framework is presented as Renewable Artificial Plant for In-situ Microbial Environmental Remediation (RAPIMER). RAPIMER exhibits high adsorption capacity for the PFAS compounds and diverse adsorption capability toward co-contaminants. Subsequently, RAPIMER provides the substrates and contaminants for in situ bioremediation via fungus Irpex lacteus and promotes PFAS detoxification. RAPIMER arises from cheap lignocellulosic sources, enabling a broader impact on sustainability and a means for low-cost pollutant remediation.

Efficient removal of neonicotinoid by singlet oxygen dominated MoSx/ceramic membrane-integrated Fenton-like process

Removal of neonicotinoids (NEOs) from contaminated water is of great importance for both ecological environment and human health. However, conventional Fenton process might be insufficient for NEOs removal due to short lifetime for generated HO• and limited Fe3+/Fe2+ redox cycle. Advancing Fenton process to produce singlet oxygen can be an effective route to improve its efficacy for NEOs removal. Herein, we developed a molybdenum sulfide modified ceramic membrane-integrated Fenton-like system to achieve efficient catalytic removal of NEOs. The reduced Mo0 and Mo4+ could promote the reduction process of Fe3+ to Fe2+, improving the activation efficiency of hydrogen peroxide (H2O2) and the generation of superoxide radical (O2•−). Consequently, the coexisting Mo6+ reacted with O2•− to generate 1O2. The membrane enabled the pollutants to adequately contact oxidants due to the enhanced convective mass transfer. The functionalized membrane exhibited stable catalytic performance for clothianidin (CLO, a kind of NEOs, 10 mg/L) removal (degradation efficiency > 85%). The presence of 1O2 enabled the dechlorination and hydroxylation of CLO and thus reduced the toxicity of wastewater. Our work sheds light on the use of functionalized ceramic membrane integrated catalytic Fenton system for effective environmental remediation.

Tungsten Trioxide and Its TiO2 Mixed Composites for the Photocatalytic Degradation of NOx and Bacteria (Escherichia coli) Inactivation

The increased air pollution and its impact on the environment and human health in several countries have caused global concerns. Nitrogen oxides (NO2 and NO) are principally emitted from industrial activities that strongly contribute to poor air quality. Among bacteria emanated from the fecal droppings of livestock, wildlife, and humans, Escherichia coli is the most abundant, and is often associated with the health risk of water. TiO2/WO3 heterostructures represent emerging systems for photocatalytic environmental remediation. However, the results reported in the literature are conflicting, depending on several parameters. In this work, WO3 and a series of TiO2/WO3 composites were properly synthesized by an easy and fast method, abundantly characterized by several techniques, and used for NOx degradation and E. coli inactivation under visible light irradiation. We demonstrated that the photoactivity of TiO2/WO3 composites towards NO2 degradation under visible light is strongly related to the WO3 content. The best performance was obtained by a WO3 load of 20% that guarantees limited e−/h+ recombination. On the contrary, we showed that E. coli could not be degraded under visible irradiation of the TiO2/WO3 composites.

From Photocatalysis to Photo-Electrocatalysis: An Innovative Water Remediation System for Sustainable Fish Farming

In this study, the effects of photo-electrocatalysis (PEC) were evaluated as an innovative application of conventional photocatalysis (PC) to remediate water in a recirculating system for rainbow trout (Oncorhynchus mykiss) culture, in relation to fish welfare and health, with a multidisciplinary approach. Three tanks were employed, equipped with conventional biological filters as a control system, and three tanks equipped with the PEC purification system. The concentrations of ammonia, nitrite and nitrate ions in water were monitored, and the fish’s oxidative damage and stress response were evaluated in parallel. The water of the PEC-treated experimental group showed lower ammonia (TAN) and nitrite concentrations and higher nitrate concentration, possibly deriving from TAN oxidation through PEC, also leading to gaseous N2. Histological analysis did not reveal any pathological alteration in the gills and liver of both groups. The superoxide dismutase (sod1), glutathione reductase (GR), glutathione peroxidase (GPx1), and Tumor necrosis factor (TNFα) gene expressions were significantly higher in the control group than in the PEC-treated group, while the Heat shock protein 70 (Hsp70) expression did not show any difference in the two groups. These results indicate that the use of PEC filters has a positive effect on water quality, compared to the use of conventional biological filters, inducing a high level of welfare in O. mykiss.

Ultra-low power light driven lycopodium-like nanofiber membrane reinforced by PET braid tube with robust pollutants removal and regeneration capacity based on photo-Fenton catalysis

Membrane separation is regarded as one of the most effective strategies for treating complex wastewater systems for environmental remediation. However, frequent membrane fouling has severely limited its widespread application. Herein, a nanofiber membrane composed of β-FeOOH nanorods and electrospun Poly (m-phenyleneisophalamide) (PMIA) nanofibers on polyester braid tube substrate was fabricated by electrospinning and in situ synthesis. The study focuses on the photo-Fenton catalytic performance under ultra-low power LED illumination. The PMIA/β-FeOOH nanofiber membrane presents excellent catalytic capacity for removing dyes, antibiotics and hazardous Cr (VI) (the maximum removal efficiency up to ∼ 99.9 %). In virtue of high porosity and interconnected channel structure, the reinforced membrane exhibits a superior permeation ability (∼3000 L·m−2·h−1) and outstanding oil–water separation efficiency (∼99 %). More importantly, it can simply achieve highly efficient self-cleaning and membrane regeneration by ultra-low power LED driven photo-Fenton catalysis. The versatile PMIA/β-FeOOH nanofiber membrane exhibits an excellent and stable photo-Fenton catalytic capacity as well as superhydrophilicity/underwater superoleophobicity under ultra-low power visible-light irradiation. This revolutionary ultra-low power driven photocatalytic membrane provides a new approach responding to complicated wastewater purification.

A novel sulfur-driven autotrophic denitrification coupled with bio-cathode system for bioelectricity generation and groundwater remediation.

This study explored the feasibility of treating wastewater using sulfur-driven autotrophic denitrification (SAD) coupled with the bio-cathode of microbial fuel cell (MFC), focusing on simultaneous bioelectricity generation, denitrification, and desulphurization. A maximum output voltage of 360 mV was obtained with a power generation cycle of 25 h when simulated wastewater with 100.0 mg/L of each NO3--N and S2--S was employed as the influent in the SAD-BMFC. Compared with solo SAD or MFC, SAD-BMFC obtained a higher NO3--N removal rate (E12 h = 87.7%, E24 h = 100%), and less NO2--N accumulation. S2--S of the influent was almost completely removed, oxidized to S0-S (88.6-90.2 mg/L) and SO42--S (9.8-11.4 mg/L). The reaction system achieved self-balance of acidity-alkalinity (pH 7.05-7.35). The SAD process was the main pathway for NO3--N removal (80.2%) and a smaller proportion of electrons came from the bio-cathode. This study effectively combined SAD with a bio-cathode system for simultaneous energy harvest and bio-enhanced remediation of groundwater contaminated by both NO3--N and S2--S.

Synergistic strengthening of SPC/Fe(II) system by CA coupled with mZVI for trichloroethylene degradation in SDS-containing aqueous solution

This study investigated the effect of synergistic strengthening by citric acid (CA) coupled with micron zero valent iron (mZVI) in Fe(II) catalyzed sodium percarbonate (SPC) system on trichloroethylene (TCE) removal in an aqueous environment with the existence of sodium dodecyl sulfate (SDS). Compared with SPC/Fe(II), SPC/Fe(II)/mZVI, SPC/Fe(II)/CA, and SPC/Fe(II)/CA/mZVI systems, the synergistic strengthening effect by CA and mZVI could maximize TCE removal to 92.0 % and dechlorination of TCE to 88.0 % within 30 min. Furthermore, the synergistic system has the widest pH range of 3–7. The removal of TCE could hardly be improved by only adjusting pH in the system without CA addition, while it could be easily achieved by the synergistic strengthening SPC/Fe(II)/CA/mZVI system. Fe(II) concentration and hydroxyl radical (HO•) amount showed that the presence of CA and mZVI could continuously release Fe(II) and efficiently promote the formation of HO•. Besides HO•, reductive radicals such as superoxide radical (O2−•) and carbon dioxide radical (CO2−•) were also abundant in the SDS environment. Although the reaction kinetic constant was reduced due to the negative effects of weak alkaline pH and inorganic anions in the actual groundwater, the chemical dosages with the original ratio of SPC/Fe(II)/CA/mZVI could still reach 87.8 % TCE degradation, which showed the superiority of this system for remediation of the actual contaminated groundwater.

Towards an effective application of parameter estimation and uncertainty analysis to mathematical groundwater models

Groundwater models serve as support tools to among others: assess water resources, evaluate management strategies, design remediation systems and optimize monitoring networks. Thus, the assimilation of information from observations into models is crucial to improve forecasts and reduce uncertainty of their results. As more information is collected routinely due to the use of automatic sensors, data loggers and real time transmission systems; groundwater modelers are becoming increasingly aware of the importance of using sophisticated tools to perform model calibration in combination with sensitivity and uncertainty analysis. Despite their usefulness, available approaches to perform this kind of analyses still present some challenges such as non-unique solution for the parameter estimation problem, high computational burden and a need of a deep understanding of the theoretical basis for the correct interpretation and use of their results, in particular the ones related to uncertainty analysis. We present a brief derivation of the main equations that serve as basis for this kind of analysis. We demonstrate how to use them to estimate parameters, assess the sensitivity and quantify the uncertainty of the model results using an example inspired by a real world setting. We analyze some of the main pitfalls that can occur when performing such kind of analyses and comment on practical approaches to overcome them. We also demonstrate that including groundwater flow estimations, although helpful in constraining the solution of the inverse problem as shown previously, may be difficult to apply in practice and, in some cases, may not provide enough information to significantly constrain the set of potential solutions. Therefore, this article can serve as a practitioner-oriented introduction for the application of parameter estimation and uncertainty analysis to groundwater models.

«Механизм действия права»: содержание понятия

The article deals with the challenges that arise when we try to comprehend the concept of «mechanism of law». The author analyzes and systematizes various points of view on the issue of its scope. Considering the ideas existing in legal science about the action of law, the nature of the relationship between the action of law and the activity of legal subjects, the author concludes that it is incorrect to identify the mechanism of action of law with the system of legal remedies used by subjects to achieve legally significant goals. It is proved that the mechanism of law is a sequence of stages reflecting the logic of the movement from the emergence of a legitimate interest to its implementation by legal measures, among which a special role is assigned to legitimate state coercion. The author reveals the most significant characteristics of the mechanism of action of law. Firstly, an idea of its scope allows us to describe the stages of the named mechanism (which the author proposes to consider the manifestation of law, familiarization with law, individual legal regulation and the implementation of law). Secondly, the difference between the mechanism of action of law and the mechanism of action of other social regulators makes it possible to better understand the study of the impulse that activates the mechanism in question and its driving force.