Performance Evaluation of Low-Cost BTEX Sensors and Devices within the EURAMET Key-VOCs Project

The KEY-VOCs project is a EURAMET joint research project focused on key Volatile Organic Compounds (VOCs) in air. One of its activities is the evaluation of sensors-based measurement systems. In Europe, the monitoring of benzene in ambient air is mandatory as set by the European Directive for air quality (AQD) [1]. This Directive states that the reference method of measurement shall consist of active or on-line sampling followed by gas chromatography [2]. These methods are time consuming, expensive to implement and not easily portable prohibiting more local estimation of the population exposure. However, the AQD allows using indicative measurements with higher uncertainty than those of the reference methods. Sensor systems are good candidates for indicative methods with the additional ability of near-to real-time measurements

Review of Portable and Low-Cost Sensors for the Ambient Air Monitoring of Benzene and Other Volatile Organic Compounds

This article presents a literature review of sensors for the monitoring of benzene in ambient air and other volatile organic compounds. Combined with information provided by stakeholders, manufacturers and literature, the review considers commercially available sensors, including PID-based sensors, semiconductor (resistive gas sensors) and portable on-line measuring devices as for example sensor arrays. The bibliographic collection includes the following topics: sensor description, field of application at fixed sites, indoor and ambient air monitoring, range of concentration levels and limit of detection in air, model descriptions of the phenomena involved in the sensor detection process, gaseous interference selectivity of sensors in complex VOC matrix, validation data in lab experiments and under field conditions

Effects of Modified Atmosphere Packaging on Selected Phenomena Affecting Quality of Fresh, Edible Bamboo Shoots

ABSTRACT Changes in phenomena affecting quality of fresh bamboo shoots (Dendrocalamus asper, Schultes f.) due to modified atmosphere packaging were evaluated. After harvest bamboo shoots were peeled, and stored in the open (unpacked) or packaged in polyvinyl chloride wrap (thickness 5 pm) or polypropylene bags (thickness 15 pm) at two different temperatures (9 and 28 °C) and shelf life was determined. Unpacked samples had very high weight losses (5% per day) at both temperatures limiting their shelf life to less than 2 days. Both types of packaging reduced water loss significantly (polyvinyl chloride: 0.5% per day at both temperatures, polypropylene: 0.09% and 0.14% at 9 and 28 °C respectively). Samples stored at room temperature started to discolor within 1-2 days while packed samples in the refrigerator showed the first signs of discoloration only after 5-7 days of storage. Refrigeration was also effective to inhibit fungal growth. Our results show that application of cold storage or packaging alone yields no, or only a limited extension of shelf life but their combined application yields a shelf life extension till 2 weeks. Keywords: Modified atmosphere packaging, bamboo shoots (Dendrocalamus asper, Schultes f.), postharvest

Effect of moisture on the adsorption of ammonia

The effect of moisture on the adsorption of ammonia was systematically studied using different surface materials and humidity levels. The experimental water amount fractions varied between 6 and 18,000 mu molmol(-1), and the ammonia amount fraction was 400nmolmol(-1). The investigated materials included plain 316L stainless steel and stainless steel cured with Dursan, SilcoNert 2000 and halocarbon wax coatings. Furthermore, Teflon (PTFE) and polyvinylidene difluoride (PVDF) polymer surfaces were studied. Dynamically diluted ammonia, test tubes prepared with the investigated materials, a commercial ammonia analyzer based on cavity ring-down spectroscopy, and a commercial dew-point transmitter were employed. The adsorption was assessed quantitatively using continuous flow conditions and real-time monitoring of the adsorption process. The ammonia adsorption was found to increase substantially in dry conditions for all the studied materials except PVDF. The increase was largest for plain stainless steel which was the most adsorbing material. The coatings applied on stainless steel decreased the adsorption significantly in dry conditions. Polymers PVDF and PTFE were the least-adsorbing materials. In water amount fractions between 1000 and 10,000 mu mol mol(-1), the ammonia adsorption was at its lowest. The adsorption increased again above 1% humidity levels.Peer reviewe

MetNH3: Metrology for Ammonia in Ambient Air

Measuring ammonia in ambient air is a sensitive and priority issue due to its harmful effects on human health and ecosystems. Ammonia is increasingly being globally acknowledged as a key precursor to atmospheric particulate matter. The European Directive 2001/81/EC on “National Emission Ceilings for Certain Atmospheric Pollutants (NEC)” regulates ammonia emissions in the member states. However, due to the chemical characteristics of ambient ammonia traceable on-line measurements still have significant challenges in analytical technology, uncertainty, quality assurance and quality control (QC/QA). Currently the UK National Ammonia Monitoring Network uses an accredited off-line low temporal resolution and on-line denuder–IC methods at the UK Supersites. There is a need for traceable ammonia measurements which will be vitally important for identifying changes in environment policies, climate and agricultural practice. This in turn should lead to improvements emission inventory uncertainties and for providing independent verification of atmospheric model predictions. MetNH3 (EMRP Joint Research Project) has worked with SMEs in testing improved reference gas mixtures by static and dynamic gravimetric generation methods, develop and refine existing laser based optical spectrometric standards and establishing the transfer from high-accuracy standards to field applicable methods. The first results from the metrological characterisation of a commercially available cavity ring-down spectrometer (CRDS) are presented and the results from a new design “Controlled Atmosphere Test Facility (CATFAC)”, which is currently characterising the performance of diffusive samplers. The range and characteristics of instruments are discussed. The plans for a major ammonia field intercomparison in 2016 will be outlined

Metrology for Ammonia in Ambient Air. Final publishable JRP report

This project developed reference standards and measurement techniques for traceable measurements of NH3 in air. These will enable validated high quality ammonia measurement data which will help monitor and compare NH3 levels and ensure compliance with environmental protection policies and legislation

Photoacoustic trace gas sensing : application to fruit and insects

Contains fulltext : 19010_phottrgas.pdf (publisher's version ) (Open Access)A novel photoacoustic spectrometer has been applied to study trace gas emissions by fruit and insects. The spectrometer is based on a newly designed CO laser that can operate on 400 laser lines between 5.1-8.0 and 2.8-4.1 micrometer (delta v=1 and 2 mode, respectively). The spectrometer is equipped with three intracavity photoacoustic cells which introduces additional losses in the laser cavity, but still a proper operation in the delta v=2 mode with its low gain is possible. Fast switching between the two operation modes is achieved using a newly designed grating holder. A number of applications show the versatility of this spectrometer: The trace gase emissions by avocado fruit were studied under anaerobic and post-anaerobic conditions. Release of ethanol and acetaldehyde under anaerobic conditions followed a pattern that is similar to that of many other fruits. Returning the fruit to aerobic conditions yielded an unprecedentedly high upsurge in acetaldehyde. A similar response in acetaldehyde is observed when initial conditions are hypoxic instead of anaerobic. Another application deals with water loss recordings of tiny insects called thrips (50 microgram), the smallest of all flying insects. We were able to record the water loss of a single individual. Interestingly, they could stand arid conditions for very prolonged periods. As a potential insecticide, we tested the effect of elevated CO2 levels. Only very high CO2 levels (34 %) showed a clear effect on the mortality of the insects. Finally, with a different photoacoustic spectrometer based on a CO2 laser we determined the tracheal volume of insects using a novel SF6 wash-out technique. In addition, the respiration pattern of the insects was resolved in detail from both CO2 and SF6 release. The high sensitivity of the spectrometer for SF6 detector (5 ppt) opens new ways to study respiration in even the smallest insects104 p