Mathematical models for reactive contaminants in groundwater

Abstract The mass transport of contaminants in porous media is of great importance both in the field of research and in the applied field. Today's respect for the environment and the safeguarding of resources has greatly increased the need to monitor and prevent environmental pollution. Of great importance are the mathematical models that allow us to describe the concentration distribution in space and time of a pollutant in groundwater. This research is focused on the study and modeling of pollutants in groundwater. Bibliographic research and a subsequent in-depth study of 1D, 2D and 3D ADE models and their applications were conducted to examine the state of the art and possible areas for model development. Emphasis was placed on the development of a new one-dimensional solution. A variety of conditions were examined including the release of the source with step function, the decay of contaminants with consecutive reactions and the production and decay of the source concentration From the one-dimensional model, it was possible to extend the model to three-dimensions with the exact integral solution and approximate solution in closed form. A solution in approximate form was also obtained for a known solution in the Literature characterized by exponential decay at the source. A comparative simulation analysis was performed on the models based on Literature data

Analytical Solutions of One-Dimensional Contaminant Transport in Soils with Source Production-Decay

An analytical solution in closed form of the advection-dispersion equation in one-dimensional contaminated soils is proposed in this paper. This is valid for non-conservative solutes with first order reaction, linear equilibrium sorption, and a time-dependent Robin boundary condition. The Robin boundary condition is expressed as a combined production-decay function representing a realistic description of the source release phenomena in time. The proposed model is particularly useful to describe sources as the contaminant release due to the failure in underground tanks or pipelines, Non Aqueous Phase Liquid pools, or radioactive decay series. The developed analytical model tends towards the known analytical solutions for particular values of the rate constants

A novel method for Ion Exchange Capacity characterization applied to Anion Exchange Membranes for Water Electrolysers

Hydrogen production from water electrolysis, hydrogen fuel cells and redox flow batteries are the right approach for the renewable energy sector because the electricity generated by solar, wind, photovoltaic, hydroelectric can be managed with a carbon-free approach. These technologies all have in common one fundamental component: the membrane. Different types of membranes have been developed for both cationic and anionic exchange, and recently, research activity focalized on improving their performances is very fervent. One fundamental characteristic of a membrane is its Ion Exchange Capacity (IEC), i.e. the density of charged functionalizing groups. Within our research project NEMESI, funded by EU-PNRR (ID: RSH2B_000002), and dedicated to Anion Exchange Membrane Water Electrolysis, we studied and validated a novel alternative method to measure IEC. The present titration methods have limitations for the need of dedicated hardware or qualitative inspection of their color-turning endpoint. The proposed method, based on the redox titration of potassium ferricyanide with ascorbic acid, allows a quantitative and independent assessment based on both potentiometric and spectrophotometric measurements, along with the usually adopted visual observation, as the yellow-colored ferricyanide is reduced to colorless ferrocyanide. Moreover, if compared to the classical Mohr titration with silver nitrate, the new method can be carried out at variable ferricyanide concentrations during the addition of the ascorbic acid, so a complete curve of the redox reaction can be constructed: the initial ferricyanide ion load of the membrane (IEC) can thus be derived in a more precise way than with a single-point evaluation. Only one Ag/AgCl reference electrode and a platinum working electrode are required without any power supply/potentiostat. The proposed method was validated using Anion Exchange Membranes with known IEC

Design of the experiments for the selection of potential electrocatalysts for both AEM Electrolyzers and Redox Flow Batteries

Both hydrogen production by anion exchange membrane water electrolysis (AEMWE) and energy storage by redox flow batteries (RFB) are promising technologies for dealing with the intermittency of green electricity generation. We investigated on the possibility of using the same electrocatalyst in both the systems in order to reduce production costs if industrial scale electrochemical devices are to be constructed. In this work we selected spinel-based nanostructures as promising catalysts for both oxygen evolution reaction (OER) in AEMWE and positive electrode improvement in Vanadium RFB, and design a complete experimental campaign to choose the best material

Development of a low-cost monitoring system and operating database for microalgae cultivation in photobioreactors

The economic balance of microalgae cultivation at industrial scale to produce biofuels is currently advantageous only if some integrated solutions are adopted and/or simple design reactors as open ponds or tubular are used. Scale-up from lab to industrial production usually requires continuously or semi-continuously operated plants. Since in industrial production often wastewater and flue gas rich of CO2 are used as nutrients, feeding intervals must be controlled, by taking into account also light \u2013 dark cycles. Moreover, also extraction must be operated at time intervals and/or at different residence times if sets of parallel-series reactors are used. Finally, being algal growth discontinuous, semi-continuous reactors seem to be the best operating choice. Since the profit margin is low, production processes must be optimized, and to do this, continuous but low cost measures must be performed. An on-line monitoring and low-cost early-warning system was developed and is presented in this work. The system is tailored for microalgae cultures in open ponds and in tubular /airlift semi-continuous reactors. Measures of pH, T, DOx, Conductivity are carried out due to their low cost, while spectra or sample measurements, that cannot be adopted as on-line measures of plant performance, are used for calibration. Architecture and main features of the system, called MEMO, are described. It is an open-source web-based smart-SCADA system ad-hoc developed to acquire, manage, aggregate, historicize and show in real-time process data from microalgae cultivation. By MEMO it is possible to monitor the main operative conditions of the units in their different sections and to manage alarms. MEMO is mainly based on open-source hardware and software

A Method for Identifying Pollution Sources of Heavy Metals and PAH for a Risk-Based Management of a Mediterranean Harbour

A procedure for assessing harbour pollution by heavy metals and PAH and the possible sources of contamination is proposed. The procedure is based on a ratio-matching method applied to the results of principal component analysis (PCA), and it allows discrimination between point and nonpoint sources. The approach can be adopted when many sources of pollution can contribute in a very narrow coastal ecosystem, both internal and outside but close to the harbour, and was used to identify the possible point sources of contamination in a Mediterranean Harbour (Port of Vado, Savona, Italy). 235 sediment samples were collected in 81 sampling points during four monitoring campaigns and 28 chemicals were searched for within the collected samples. PCA of total samples allowed the assessment of 8 main possible point sources, while the refining ratio-matching identified 1 sampling point as a possible PAH source, 2 sampling points as Cd point sources, and 3 sampling points as C > 12 point sources. By a map analysis it was possible to assess two internal sources of pollution directly related to terminals activity. The study is the prosecution of a previous work aimed at assessing Savona-Vado Harbour pollution levels and suggested strategies to regulate the harbour activities

Assessment of sediment contamination and sampling design in Savona Harbour, Italy

none4A method for assessing environmental contamination in harbour sediments and designing the forthcoming monitoring activities in enlarged coastal ecosystems is proposed herein. The method is based on coupling principal component analysis of previous sampling campaigns with a discrete optimisation of a value for money function. The objective function represents the utility derived for every sum of money spent in sampling and chemical analysis. The method was then used to assess actual contamination and found to be well suited for reducing the number of chemicals to be searched during extended monitoring activities and identifying the possible sources of contamination. Data collected in Savona Harbour (Porto Vado), Italy, where construction of a new terminal construction is planned, were used to illustrate the procedure. 23 chemicals were searched for within a total of 213 samples in 68 sampling points during three monitoring campaigns. These data were used to test the procedure. Subsequently, 28 chemicals were searched for within 14 samples in 10 sampling points and collected data were used to evaluate the experimental error and to validate the proposed procedure.embargoed_20201001O. Paladino; M. Massabò; F. Fissore; A. MorandaPaladino, Ombretta; M., Massabò; F., Fissore; Moranda, Ariann

A novel method for Ion Exchange Capacity characterization applied to Anion Exchange Membranes for Water Electrolysers

Hydrogen production from water electrolysis, hydrogen fuel cells and redox flow batteries are the right approach for the renewable energy sector because the electricity generated by solar, wind, photovoltaic, hydroelectric can be managed with a carbon-free approach. These technologies all have in common one fundamental component: the membrane. Different types of membranes have been developed for both cationic and anionic exchange, and recently, research activity focalized on improving their performances is very fervent. One fundamental characteristic of a membrane is its Ion Exchange Capacity (IEC), i.e. the density of charged functionalizing groups. Within our research project NEMESI, funded by EU-PNRR (ID: RSH2B_000002), and dedicated to Anion Exchange Membrane Water Electrolysis, we studied and validated a novel alternative method to measure IEC. The present titration methods have limitations for the need of dedicated hardware or qualitative inspection of their color-turning endpoint. The proposed method, based on the redox titration of potassium ferricyanide with ascorbic acid, allows a quantitative and independent assessment based on both potentiometric and spectrophotometric measurements, along with the usually adopted visual observation, as the yellow-colored ferricyanide is reduced to colorless ferrocyanide. Moreover, if compared to the classical Mohr titration with silver nitrate, the new method can be carried out at variable ferricyanide concentrations during the addition of the ascorbic acid, so a complete curve of the redox reaction can be constructed: the initial ferricyanide ion load of the membrane (IEC) can thus be derived in a more precise way than with a single-point evaluation. Only one Ag/AgCl reference electrode and a platinum working electrode are required without any power supply/potentiostat. The proposed method was validated using Anion Exchange Membranes with known IEC

Design of the experiments for the selection of potential electrocatalysts for both AEM Electrolyzers and Redox Flow Batteries

Both hydrogen production by anion exchange membrane water electrolysis (AEMWE) and energy storage by redox flow batteries (RFB) are promising technologies for dealing with the intermittency of green electricity generation. We investigated on the possibility of using the same electrocatalyst in both the systems in order to reduce production costs if industrial scale electrochemical devices are to be constructed. In this work we selected spinel-based nanostructures as promising catalysts for both oxygen evolution reaction (OER) in AEMWE and positive electrode improvement in Vanadium RFB, and design a complete experimental campaign to choose the best material