Tanja Radu

Comparison of soil pollution concentrations determined using AAS and portable XRF techniques.

Past mining activities in the area of Silvermines, Ireland, have resulted in heavily polluted soils. The possibility of spreading pollution to the surrounding areas through dust blow-offs poses a potential threat for the local communities. Conventional environmental soil and dust analysis techniques are very slow and laborious and consequently there is a need for fast and accurate analytical methods, which can provide real-time in situ pollution mapping. Laboratory-based aqua regia acid digestion of the soil samples collected in the area followed by the atomic absorption spectrophotometry (AAS) analysis confirmed very high pollution, especially by Pb, As, Cu, and Zn. In parallel, samples were analyzed using portable X-ray fluorescence radioisotope and miniature tube powered (XRF) NITON instruments and their performance was compared. Overall, the portable XRF instrument gave excellent correlation with the laboratory-based reference AAS method.

Ion selective electrodes in environmental analysis

An overview is given dealing with the application of ion-selective electrodes (ISEs) in environmental analysis. ISEs are placed into the context of the trend of development of sensors for extensive and frequent monitoring. Discussed are the issues such as sensing platforms and their mass-production, improvement of precision, diagnostic of sensor functionality, and development of reference electrodes. Several examples of real-life application of ISEs in environmental analysis are given. The main emphasis of this article is directed towards summarizing recent results of the authors during the past several years.

Portable X-ray fluorescence as a rapid technique for surveying elemental distributions in soil

ABSTRACT Case studies from two sites demonstrate how concentration distributions of hazardous contaminants can be rapidly measured and visualized using portable XRF (X-ray fluorescence) coupled with geostatistical interpolation tools. In this study, lead is used as an exemplar due to its well-known detrimental effect on human health through long-term exposure. A portable Thermo Scientific NITON X-ray fluorescence (XRF) instrument was used for real-time in-situ concentration measurements, which were linked to GPS coordinates of the sampling locations. A 52 point mixed sampling density survey was performed at a site near Maynooth, Co. Kildare, and a second 58 survey undertaken at Dublin City University (DCU). At Maynooth, high concentrations of Pb (above 110 mg/kg) were found close to the site where a local canal meets a road. At the DCU site, results indicate high Pb concentrations (above 160 mg/kg) near a busy main road. Geostatistical techniques were used to generate concentration prediction and critical threshold contour surfaces for both sites. Linked with GPS coordinates for each sampling location, this technology enables the distribution of multiple elements to be mapped over wide areas in a relatively short time. Supplemental materials are available for this article. Go to the publishers online edition of Spectroscopy Letters to view the supplemental file.

Fibers and Fabrics for Chemical and Biological Sensing

Wearable sensors can be used to monitor many interesting parameters about the wearer’s physiology and environment, with important applications in personal health and well-being, sports performance and personal safety. Wearable chemical sensors can monitor the status of the wearer by accessing body fluids, such as sweat, in an unobtrusive manner. They can also be used to protect the wearer from hazards in the environment by sampling potentially harmful gas emissions, such as carbon monoxide. Integrating chemical sensors into textile structures is a challenging and complex task. Issues which must be considered include sample collection, calibration, waste handling, fouling and reliability. Sensors must also be durable and comfortable to wear. Here, we present examples of wearable chemical sensors that monitor the person and also his/her environment. We also discuss the issues involved in developing wearable chemical sensors and strategies for sensor design and textile integration.

Simultaneous Detection of Ammonium and Nitrate in Environmental Samples Using on Ion-Selective Electrode and Comparison with Portable Colorimetric Assays

Simple, robust, and low-cost nitrate- and ammonium-selective electrodes were made using substrate prepared from household materials. We explored phosphonium-based ILs and poly (methyl methacrylate)/poly(decyl methacrylate)(MMA-DMA) copolymer as matrix materials alternative to classical PVC-based membranes. IL-based membranes showed suitability only for nitrate-selective electrode exhibiting linear concentration range between 5.0 × 10−6 and 2.5 × 10−3 M with a detection limit of 5.5 × 10−7 M. On the other hand, MMA-DMA—based membranes showed suitability for both ammonium- and nitrate-selective electrodes, and were successfully applied to detect NO3− and NH4+ in water and soil samples. The proposed ISEs exhibited near-Nernstian potentiometric responses to NO3− and NH4+ with the linear range concentration between 5.0 × 10−5 and 5.0 × 10−2 M (LOD = 11.3 µM) and 5.0 × 10−6 and 1.0 × 10−3 M (LOD = 1.2 µM), respectively. The power of ISEs to detect NO3− and NH4+ in water and soils was tested by comparison with traditional, portable colorimetric techniques. Procedures required for analysis by each technique from the perspective of a non-trained person (e.g., farmer) and the convenience of the use on the field are compared and contrasted.

Community scale, decentralised anaerobic digestion for energy and resource recovery

The paper describes “Community scale, decentralized anaerobic digestion for energy and resource technology” which is a joint UK-Thailand project much in line with the current aims of the Thai Government for decentralized energy generation. The use of food waste for biogas generation by the process of anaerobic digestion provides multiple benefits: decreased energy dependency, nutrient preservation and recycling, and reduced greenhouse gas emissions. It is also promoted in the remoter Scotland and Wales of the UK. The aim of the project is the design and deployment of small scale digesters and their networking into remotely monitored units. Here, we are describing initial design of the reactors and some issues associated with using food waste as substrate. Based on the literature, we have also estimated the reactors performance to be 0.40-0.50 m3/kg of feedstock for biogas production.

Operational experiences of industrial scale AD: Lessons for the future

In this paper we discuss operational experiences of two large industrial anaerobic digestion facilities processing brewery waste and maize. The raw effluent from the brewery waste has COD ranging from 5500 mg/l to 41400 mg/l, with variable flow rate and suspended solids up to 4800 mg/l. The Anaerobic Digestion (AD) treatment uses 900m3 EGSB reactor. The two-year monitoring of data includes Ripleys Ratio, Volatile Fatty Acids, and pH. These parameters indicate lower performance and certain instability before the planned maintenance works, followed by the much improved performance afterwards. The average biogas production is 3540 Nm3/day but the variance of the biogas flow remains an issue. The combined Heat and Power (CHP) production from energy crops uses ensilaged, purposely grown maize with 28-34% dry matter and chop length of 6-9 mm. The available three-year data for this AD facilities indicate great process stability. It uses 150 t/day of maize, and result in energy production of 21 GW/year which is 7000 homes equivalent. This energy is evenly split between the sewage treatment works and injection to the public electricity grid. Depending on the dry solids content, the digestate is either stored and spread on the land, or sold to farmers.

Ion-selective Electrodes with Polypyrrole-and Poly(3-octylthiophene)-Mediated Internal Solid Contact in Soil Analysis

The integration of chemo/bio sensors in large wireless sensing networks (WSN) is currently limited, largely due to the issues related with power consumption and data handling. Also, there are very few low cost chemo/bio sensors that combine sensitive, low limit of detection capabilities with simple experimental setup. However, with recent advances, ion-selective electrodes (ISEs) may become an excellent candidate for deployment in WSNs. In this paper, we describe a solid-contact electrode based on poly(3-octylthiophene) (POT) as an internal contact. We report its characteristics and its application to the for measurement of Pb2+ in 16 soil samples, with a ultimate goal of producing a small, simple and sensitive sensor that can be integrated into WSNs. The electrode had a detection in the soil digestion matrix (1×10-3 M HNO3) of 1×10-7 M (20 ppb). The electrodes results were compared with atomic absorbtion spectrometry (AAS) as a common instrumental technique used in soil analysis. We also report on the performance of solid-contact ISEs based on polypyrrole (PPy) and POT. A superior detection limit of POT- relative to PPy-based ISEs was observed. Furthermore, a good correlation has been observed between POT-based ISEs and AAS and between the two types of ISEs.