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Modern Technologies for Sensing Pollution in Air, Water, and Soil
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Modern Technologies for Sensing Pollution in Air, Water, and Soil

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Chemical Sensors".

Deadline for manuscript submissions: closed (31 December 2014) | Viewed by 143406

Special Issue Editor

Prof. Dr. Ki-Hyun Kim

grade E-Mail Website
Guest Editor
Department of Civil & Environmental Engineering, Hanyang University, 222 Wangsimni-Ro, Seoul 04763, Republic of Korea
Interests: environmental & biomedical monitoring; air quality & environmental engineering; material engineering; coordination polymers; metal-organic frameworks (MOFs)
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Remarkable and rapid advances in technology have brought ever-increasing improvements in the quality of our everyday life but to the detriment to our environment and ecosystem. Emissions of anthropogenically-derived pollutants have increased gradually causing global deterioration of our atmosphere, water, and soil resources to levels not previously experienced in human history. Although emissions abatement efforts have had some limited success in some sectors, the prognosis for most ecological systems is to worsen over time. In light of the growing demand for accurately sensing environmental pollution, sensing methods have been developed to cover various pollutants in diverse media:

  • Heavy metals
  • Persistent organic pollutants (POP)
  • Environmental Persistent Pharmaceutical Pollutants (EPPP)
  • Polycyclic aromatic hydrocarbons
  • Volatile organic compounds
  • Environmental xenobiotics
  • Hazardous atmospheric pollutants (HAP)

This special issue aims to invite articles on the most up to date, emerging or new technologies to monitor various pollutants present in diverse environmental media including water, air, and soil systems

Prof. Dr. Ki-Hyun Kim
Guest Editor

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Keywords

  • monitoring
  • sensor
  • environmental media
  • water
  • air
  • soil
  • hazardous pollutants

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Published Papers (19 papers)

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Research

1485 KiB  
Article
Occurrence and Concentrations of Toxic VOCs in the Ambient Air of Gumi, an Electronics-Industrial City in Korea
by Sung-Ok Baek, Lakshmi Narayana Suvarapu and Young-Kyo Seo
Sensors 2015, 15(8), 19102-19123; https://doi.org/10.3390/s150819102 - 5 Aug 2015
Cited by 18 | Viewed by 6756
Abstract
This study was carried out to characterize the occurrence and concentrations of a variety of volatile organic compounds (VOCs) including aliphatic, aromatic, halogenated, nitrogenous, and carbonyl compounds, in the ambient air of Gumi City, where a large number of electronics industries are found. [...] Read more.
This study was carried out to characterize the occurrence and concentrations of a variety of volatile organic compounds (VOCs) including aliphatic, aromatic, halogenated, nitrogenous, and carbonyl compounds, in the ambient air of Gumi City, where a large number of electronics industries are found. Two field monitoring campaigns were conducted for a one year period in 2003/2004 and 2010/2011 at several sampling sites in the city, representing industrial, residential and commercial areas. More than 80 individual compounds were determined in this study, and important compounds were then identified according to their abundance, ubiquity and toxicity. The monitoring data revealed toluene, trichloroethylene and acetaldehyde to be the most significant air toxics in the city, and their major sources were mainly industrial activities. On the other hand, there was no clear evidence of an industrial impact on the concentrations of benzene and formaldehyde in the ambient air of the city. Overall, seasonal variations were not as distinct as locational variations in the VOCs concentrations, whereas the within-day variations showed a typical pattern of urban air pollution, i.e., increase in the morning, decrease in the afternoon, and an increase again in the evening. Considerable decreases in the concentrations of VOCs from 2003 to 2011 were observed. The reductions in the ambient concentrations were confirmed further by the Korean PRTR data in industrial emissions within the city. Significant decreases in the concentrations of benzene and acetaldehyde were also noted, whereas formaldehyde appeared to be almost constant between the both campaigns. The decreased trends in the ambient levels were attributed not only to the stricter regulations for VOCs in Korea, but also to the voluntary agreement of major companies to reduce the use of organic solvents. In addition, a site planning project for an eco-friendly industrial complex is believed to play a contributory role in improving the air quality of the city. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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4189 KiB  
Article
Submersible Spectrofluorometer for Real-Time Sensing of Water Quality
by Adriana Puiu, Luca Fiorani, Ivano Menicucci, Marco Pistilli and Antonia Lai
Sensors 2015, 15(6), 14415-14434; https://doi.org/10.3390/s150614415 - 18 Jun 2015
Cited by 17 | Viewed by 8900
Abstract
In this work, we present a newly developed submersible spectrofluorometer (patent pending) applied to real-time sensing of water quality, suitable for monitoring some important indicators of the ecological status of natural waters such as chlorophyll-a, oil and protein-like material. For the optomechanical realization [...] Read more.
In this work, we present a newly developed submersible spectrofluorometer (patent pending) applied to real-time sensing of water quality, suitable for monitoring some important indicators of the ecological status of natural waters such as chlorophyll-a, oil and protein-like material. For the optomechanical realization of the apparatus, a novel conceptual design has been adopted in order to avoid filters and pumps while maintaining a high signal-to-noise ratio. The elimination of filters and pumps has the advantage of greater system simplicity and especially of avoiding the risk of sample degradation. The use of light-emitting diodes as an excitation source instead of Xe lamps or laser diodes helped save on size, weight, power consumption and costs. For sensor calibration we performed measurements on water samples with added chlorophyll prepared in the laboratory. The sensor functionality was tested during field campaigns conducted at Albano Lake in Latium Region of Italy as well as in the Herzliya Harbor, a few kilometers North East of Tel Aviv in Israel. The obtained results are reported in the paper. The sensitivity achieved for chlorophyll-a detection was found to be at least 0.2 µg/L. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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1340 KiB  
Article
Reversible NO2 Optical Fiber Chemical Sensor Based on LuPc2 Using Simultaneous Transmission of UV and Visible Light
by Antonio Bueno, Driss Lahem, Christophe Caucheteur and Marc Debliquy
Sensors 2015, 15(5), 9870-9881; https://doi.org/10.3390/s150509870 - 27 Apr 2015
Cited by 13 | Viewed by 6176
Abstract
In this paper, an NO2 optical fiber sensor is presented for pollution monitoring in road traffic applications. This sensor exploits the simultaneous transmission of visible light, as a measurement signal, and UV light, for the recovery of the NO2 sensitive materials. [...] Read more.
In this paper, an NO2 optical fiber sensor is presented for pollution monitoring in road traffic applications. This sensor exploits the simultaneous transmission of visible light, as a measurement signal, and UV light, for the recovery of the NO2 sensitive materials. The sensor is based on a multimode fiber tip coated with a thin film of lutetium bisphthalocyanine (LuPc2). The simultaneous injection of UV light through the fiber is an improvement on the previously developed NO2 sensors and allows the simplification of the sensor head, rendering the external UV illumination of the film unnecessary. Coatings of different thicknesses were deposited on the optical fiber tips and the best performance was obtained for a 15 nm deposited thickness, with a sensitivity of 5.02 mV/ppm and a resolution of 0.2 ppb in the range 0–5 ppm. The response and recovery times are not dependent on thickness, meaning that NO2 does not diffuse completely in the films. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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2325 KiB  
Article
Stability of the Nine Sky Quality Meters in the Dutch Night Sky Brightness Monitoring Network
by Peter Den Outer, Dorien Lolkema, Marty Haaima, Rene Van der Hoff, Henk Spoelstra and Wim Schmidt
Sensors 2015, 15(4), 9466-9480; https://doi.org/10.3390/s150409466 - 22 Apr 2015
Cited by 19 | Viewed by 7032
Abstract
In the context of monitoring abundance of artificial light at night, the year-to-year stability of Sky Quality Meters (SQMs) is investigated by analysing intercalibrations derived from two measurement campaigns that were held in 2011 and 2012. An intercalibration comprises a light sensitivity factor [...] Read more.
In the context of monitoring abundance of artificial light at night, the year-to-year stability of Sky Quality Meters (SQMs) is investigated by analysing intercalibrations derived from two measurement campaigns that were held in 2011 and 2012. An intercalibration comprises a light sensitivity factor and an offset for each SQM. The campaigns were concerned with monitoring measurements, each lasting one month. Nine SQMs, together forming the Night Sky Brightness Monitoring network (MHN) in The Netherlands, were involved in both campaigns. The stability of the intercalibration of these instruments leads to a year-to-year uncertainty (standard deviation) of 5% in the measured median luminance occurring at the MHN monitoring locations. For the 10-percentiles and 90-percentiles, we find 8% and 4%, respectively. This means that, for urban and industrial areas, changes in the sky brightness larger than 5% become detectable. Rural and nature areas require an 8%–9% change of the median luminance to be detectable. The light sensitivety agrees within 8% for the whole group of SQMs. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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3523 KiB  
Article
Comparison of the Detection Characteristics of Trace Species Using Laser-Induced Breakdown Spectroscopy and Laser Breakdown Time-of-Flight Mass Spectrometry
by Zhenzhen Wang, Yoshihiro Deguchi, Junjie Yan and Jiping Liu
Sensors 2015, 15(3), 5982-6008; https://doi.org/10.3390/s150305982 - 11 Mar 2015
Cited by 15 | Viewed by 8243
Abstract
The rapid and precise element measurement of trace species, such as mercury, iodine, strontium, cesium, etc. is imperative for various applications, especially for industrial needs. The elements mercury and iodine were measured by two detection methods for comparison of the corresponding detection features. [...] Read more.
The rapid and precise element measurement of trace species, such as mercury, iodine, strontium, cesium, etc. is imperative for various applications, especially for industrial needs. The elements mercury and iodine were measured by two detection methods for comparison of the corresponding detection features. A laser beam was focused to induce plasma. Emission and ion signals were detected using laser-induced breakdown spectroscopy (LIBS) and laser breakdown time-of-flight mass spectrometry (LB-TOFMS). Multi-photon ionization and electron impact ionization in the plasma generation process can be controlled by the pressure and pulse width. The effect of electron impact ionization on continuum emission, coexisting molecular and atomic emissions became weakened in low pressure condition. When the pressure was less than 1 Pa, the plasma was induced by laser dissociation and multi-photon ionization in LB-TOFMS. According to the experimental results, the detection limits of mercury and iodine in N2 were 3.5 ppb and 60 ppb using low pressure LIBS. The mercury and iodine detection limits using LB-TOFMS were 1.2 ppb and 9.0 ppb, which were enhanced due to different detection features. The detection systems of LIBS and LB-TOFMS can be selected depending on the condition of each application. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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16732 KiB  
Article
A Bio-Inspired Two-Layer Sensing Structure of Polypeptide and Multiple-Walled Carbon Nanotube to Sense Small Molecular Gases
by Li-Chun Wang, Tseng-Hsiung Su, Cheng-Long Ho, Shang-Ren Yang, Shih-Wen Chiu, Han-Wen Kuo and Kea-Tiong Tang
Sensors 2015, 15(3), 5390-5401; https://doi.org/10.3390/s150305390 - 5 Mar 2015
Cited by 7 | Viewed by 6128
Abstract
In this paper, we propose a bio-inspired, two-layer, multiple-walled carbon nanotube (MWCNT)-polypeptide composite sensing device. The MWCNT serves as a responsive and conductive layer, and the nonselective polypeptide (40 mer) coating the top of the MWCNT acts as a filter into which small [...] Read more.
In this paper, we propose a bio-inspired, two-layer, multiple-walled carbon nanotube (MWCNT)-polypeptide composite sensing device. The MWCNT serves as a responsive and conductive layer, and the nonselective polypeptide (40 mer) coating the top of the MWCNT acts as a filter into which small molecular gases pass. Instead of using selective peptides to sense specific odorants, we propose using nonselective, peptide-based sensors to monitor various types of volatile organic compounds. In this study, depending on gas interaction and molecular sizes, the randomly selected polypeptide enabled the recognition of certain polar volatile chemical vapors, such as amines, and the improved discernment of low-concentration gases. The results of our investigation demonstrated that the polypeptide-coated sensors can detect ammonia at a level of several hundred ppm and barely responded to triethylamine. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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1648 KiB  
Article
Hydrodynamic Voltammetry as a Rapid and Simple Method for Evaluating Soil Enzyme Activities
by Kazuto Sazawa and Hideki Kuramitz
Sensors 2015, 15(3), 5331-5343; https://doi.org/10.3390/s150305331 - 4 Mar 2015
Cited by 11 | Viewed by 8669
Abstract
Soil enzymes play essential roles in catalyzing reactions necessary for nutrient cycling in the biosphere. They are also sensitive indicators of ecosystem stress, therefore their evaluation is very important in assessing soil health and quality. The standard soil enzyme assay method based on [...] Read more.
Soil enzymes play essential roles in catalyzing reactions necessary for nutrient cycling in the biosphere. They are also sensitive indicators of ecosystem stress, therefore their evaluation is very important in assessing soil health and quality. The standard soil enzyme assay method based on spectroscopic detection is a complicated operation that requires the removal of soil particles. The purpose of this study was to develop a new soil enzyme assay based on hydrodynamic electrochemical detection using a rotating disk electrode in a microliter droplet. The activities of enzymes were determined by measuring the electrochemical oxidation of p-aminophenol (PAP), following the enzymatic conversion of substrate-conjugated PAP. The calibration curves of β-galactosidase (β-gal), β-glucosidase (β-glu) and acid phosphatase (AcP) showed good linear correlation after being spiked in soils using chronoamperometry. We also performed electrochemical detection using real soils. Hydrodynamic chronoamperometry can be used to assess the AcP in soils, with a detection time of only 90 s. Linear sweep voltammetry was used to measure the amount of PAP released from β-gal and β-glu by enzymatic reaction after 60 min. For the assessment of soil enzymes, the results of hydrodynamic voltammetry assay compared favorably to those using a standard assay procedure, but this new procedure is more user-friendly, rapid and simple. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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3206 KiB  
Article
Research on Odor Interaction between Aldehyde Compounds via a Partial Differential Equation (PDE) Model
by LuchunYan, Jiemin Liu, Chen Qu, Xingye Gu and Xia Zhao
Sensors 2015, 15(2), 2888-2901; https://doi.org/10.3390/s150202888 - 28 Jan 2015
Cited by 5 | Viewed by 7127
Abstract
In order to explore the odor interaction of binary odor mixtures, a series of odor intensity evaluation tests were performed using both individual components and binary mixtures of aldehydes. Based on the linear relation between the logarithm of odor activity value and odor [...] Read more.
In order to explore the odor interaction of binary odor mixtures, a series of odor intensity evaluation tests were performed using both individual components and binary mixtures of aldehydes. Based on the linear relation between the logarithm of odor activity value and odor intensity of individual substances, the relationship between concentrations of individual constituents and their joint odor intensity was investigated by employing a partial differential equation (PDE) model. The obtained results showed that the binary odor interaction was mainly influenced by the mixing ratio of two constituents, but not the concentration level of an odor sample. Besides, an extended PDE model was also proposed on the basis of the above experiments. Through a series of odor intensity matching tests for several different binary odor mixtures, the extended PDE model was proved effective at odor intensity prediction. Furthermore, odorants of the same chemical group and similar odor type exhibited similar characteristics in the binary odor interaction. The overall results suggested that the PDE model is a more interpretable way of demonstrating the odor interactions of binary odor mixtures. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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5834 KiB  
Article
The Enhanced Formaldehyde-Sensing Properties of P3HT-ZnO Hybrid Thin Film OTFT Sensor and Further Insight into Its Stability
by Huiling Tai, Xian Li, Yadong Jiang, Guangzhong Xie and Xiaosong Du
Sensors 2015, 15(1), 2086-2103; https://doi.org/10.3390/s150102086 - 19 Jan 2015
Cited by 40 | Viewed by 10457
Abstract
A thin-film transistor (TFT) having an organic–inorganic hybrid thin film combines the advantage of TFT sensors and the enhanced sensing performance of hybrid materials. In this work, poly(3-hexylthiophene) (P3HT)-zinc oxide (ZnO) nanoparticles’ hybrid thin film was fabricated by a spraying process as the [...] Read more.
A thin-film transistor (TFT) having an organic–inorganic hybrid thin film combines the advantage of TFT sensors and the enhanced sensing performance of hybrid materials. In this work, poly(3-hexylthiophene) (P3HT)-zinc oxide (ZnO) nanoparticles’ hybrid thin film was fabricated by a spraying process as the active layer of TFT for the employment of a room temperature operated formaldehyde (HCHO) gas sensor. The effects of ZnO nanoparticles on morphological and compositional features, electronic and HCHO-sensing properties of P3HT-ZnO thin film were systematically investigated. The results showed that P3HT-ZnO hybrid thin film sensor exhibited considerable improvement of sensing response (more than two times) and reversibility compared to the pristine P3HT film sensor. An accumulation p-n heterojunction mechanism model was developed to understand the mechanism of enhanced sensing properties by incorporation of ZnO nanoparticles. X-ray photoelectron spectroscope (XPS) and atomic force microscopy (AFM) characterizations were used to investigate the stability of the sensor in-depth, which reveals the performance deterioration was due to the changes of element composition and the chemical state of hybrid thin film surface induced by light and oxygen. Our study demonstrated that P3HT-ZnO hybrid thin film TFT sensor is beneficial in the advancement of novel room temperature HCHO sensing technology. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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915 KiB  
Article
Application of PTR-MS for Measuring Odorant Emissions from Soil Application of Manure Slurry
by Anders Feilberg, Pernille Bildsoe and Tavs Nyord
Sensors 2015, 15(1), 1148-1167; https://doi.org/10.3390/s150101148 - 9 Jan 2015
Cited by 35 | Viewed by 8420
Abstract
Odorous volatile organic compounds (VOC) and hydrogen sulfide (H2S) are emitted together with ammonia (NH3) from manure slurry applied as a fertilizer, but little is known about the composition and temporal variation of the emissions. In this work, a [...] Read more.
Odorous volatile organic compounds (VOC) and hydrogen sulfide (H2S) are emitted together with ammonia (NH3) from manure slurry applied as a fertilizer, but little is known about the composition and temporal variation of the emissions. In this work, a laboratory method based on dynamic flux chambers packed with soil has been used to measure emissions from untreated pig slurry and slurry treated by solid-liquid separation and ozonation. Proton-transfer-reaction mass spectrometry (PTR-MS) was used to provide time resolved data for a range of VOC, NH3 and H2S. VOC included organic sulfur compounds, carboxylic acids, phenols, indoles, alcohols, ketones and aldehydes. H2S emission was remarkably observed to take place only in the initial minutes after slurry application, which is explained by its high partitioning into the air phase. Long-term odor effects are therefore assessed to be mainly due to other volatile compounds with low odor threshold values, such as 4-methylphenol. PTR-MS signal assignment was verified by comparison to a photo-acoustic analyzer (NH3) and to thermal desorption GC/MS (VOC). Due to initial rapid changes in odorant emissions and low concentrations of odorants, PTR-MS is assessed to be a very useful method for assessing odor following field application of slurry. The effects of treatments on odorant emissions are discussed. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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1176 KiB  
Article
Modification of Graphene on Ultramicroelectrode Array and Its Application in Detection of Dissolved Oxygen
by Jinfen Wang, Chao Bian, Jianhua Tong, Jizhou Sun, Yang Li, Wen Hong and Shanhong Xia
Sensors 2015, 15(1), 382-393; https://doi.org/10.3390/s150100382 - 26 Dec 2014
Cited by 10 | Viewed by 6845
Abstract
This paper investigated two different modification methods of graphene (GN) on ultramicroelectrode array (UMEA) and applied the GN modified UMEA for the determination of dissolved oxygen (DO). The UMEAs were fabricated by Micro Electro-Mechanical System (MEMS) technique and the radius of each ultramicroelectrode [...] Read more.
This paper investigated two different modification methods of graphene (GN) on ultramicroelectrode array (UMEA) and applied the GN modified UMEA for the determination of dissolved oxygen (DO). The UMEAs were fabricated by Micro Electro-Mechanical System (MEMS) technique and the radius of each ultramicroelectrode is 10 μm. GN-NH2 and GN-COOH were modified on UMEA by using self-assembling method. Compared with GN-NH2 modified UMEA, the GN-COOH modified UMEA showed better electrochemical reduction to DO, owing to better dispersing and more active sites. The GN-COOH on UMEA was electroreduced to reduced GN-COOH (rGN-COOH) to increase the conductivity and the catalysis performance. Finally, the palladium nanoparticles/rGN-COOH composite was incorporated into DO microsensor for the detection of DO. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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1533 KiB  
Article
Application of Gas Sensor Arrays in Assessment of Wastewater Purification Effects
by Łukasz Guz, Grzegorz Łagód, Katarzyna Jaromin-Gleń, Zbigniew Suchorab, Henryk Sobczuk and Andrzej Bieganowski
Sensors 2015, 15(1), 1-21; https://doi.org/10.3390/s150100001 - 23 Dec 2014
Cited by 51 | Viewed by 8960
Abstract
A gas sensor array consisting of eight metal oxide semiconductor (MOS) type gas sensors was evaluated for its ability for assessment of the selected wastewater parameters. Municipal wastewater was collected in a wastewater treatment plant (WWTP) in a primary sedimentation tank and was [...] Read more.
A gas sensor array consisting of eight metal oxide semiconductor (MOS) type gas sensors was evaluated for its ability for assessment of the selected wastewater parameters. Municipal wastewater was collected in a wastewater treatment plant (WWTP) in a primary sedimentation tank and was treated in a laboratory-scale sequential batch reactor (SBR). A comparison of the gas sensor array (electronic nose) response to the standard physical-chemical parameters of treated wastewater was performed. To analyze the measurement results, artificial neural networks were used. E-nose—gas sensors array and artificial neural networks proved to be a suitable method for the monitoring of treated wastewater quality. Neural networks used for data validation showed high correlation between the electronic nose readouts and: (I) chemical oxygen demand (COD) (r = 0.988); (II) total suspended solids (TSS) (r = 0.938); (III) turbidity (r = 0.940); (IV) pH (r = 0.554); (V) nitrogen compounds: N-NO3 (r = 0.958), N-NO2 (r = 0.869) and N-NH3 (r = 0.978); (VI) and volatile organic compounds (VOC) (r = 0.987). Good correlation of the abovementioned parameters are observed under stable treatment conditions in a laboratory batch reactor. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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3771 KiB  
Article
Adaptive Weibull Multiplicative Model and Multilayer Perceptron Neural Networks for Dark-Spot Detection from SAR Imagery
by Alireza Taravat and Natascha Oppelt
Sensors 2014, 14(12), 22798-22810; https://doi.org/10.3390/s141222798 - 2 Dec 2014
Cited by 18 | Viewed by 6582
Abstract
Oil spills represent a major threat to ocean ecosystems and their environmental status. Previous studies have shown that Synthetic Aperture Radar (SAR), as its recording is independent of clouds and weather, can be effectively used for the detection and classification of oil spills. [...] Read more.
Oil spills represent a major threat to ocean ecosystems and their environmental status. Previous studies have shown that Synthetic Aperture Radar (SAR), as its recording is independent of clouds and weather, can be effectively used for the detection and classification of oil spills. Dark formation detection is the first and critical stage in oil-spill detection procedures. In this paper, a novel approach for automated dark-spot detection in SAR imagery is presented. A new approach from the combination of adaptive Weibull Multiplicative Model (WMM) and MultiLayer Perceptron (MLP) neural networks is proposed to differentiate between dark spots and the background. The results have been compared with the results of a model combining non-adaptive WMM and pulse coupled neural networks. The presented approach overcomes the non-adaptive WMM filter setting parameters by developing an adaptive WMM model which is a step ahead towards a full automatic dark spot detection. The proposed approach was tested on 60 ENVISAT and ERS2 images which contained dark spots. For the overall dataset, an average accuracy of 94.65% was obtained. Our experimental results demonstrate that the proposed approach is very robust and effective where the non-adaptive WMM & pulse coupled neural network (PCNN) model generates poor accuracies. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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757 KiB  
Article
Investigation into Alternative Sample Preparation Techniques for the Determination of Heavy Metals in Stationary Source Emission Samples Collected on Quartz Filters
by Sharon L. Goddard and Richard J. C. Brown
Sensors 2014, 14(11), 21676-21692; https://doi.org/10.3390/s141121676 - 17 Nov 2014
Cited by 13 | Viewed by 6511
Abstract
Monitoring stationary source emissions for heavy metals generally requires the use of quartz filters to collect samples because of the high temperature and high moisture sampling environment. The documentary standard method sample preparation technique in Europe, EN 14385, uses digestion in hydrofluoric acid [...] Read more.
Monitoring stationary source emissions for heavy metals generally requires the use of quartz filters to collect samples because of the high temperature and high moisture sampling environment. The documentary standard method sample preparation technique in Europe, EN 14385, uses digestion in hydrofluoric acid and nitric acid (HF/HNO3) followed by complexing with boric acid (H3BO3) prior to analysis. However, the use of this method presents a number of problems, including significant instrumental drift during analysis caused by the matrix components, often leading to instrument breakdown and downtime for repairs, as well as posing significant health and safety risks. The aim of this work was to develop an alternative sample preparation technique for emissions samples on quartz filters. The alternative techniques considered were: (i) acid digestion in a fluoroboric acid (HBF4) and HNO3 mixture and (ii) acid extraction in an aqua regia (AR) mixture (HCl and HNO3). Assessment of the effectiveness of these options included determination of interferences and signal drift, as well as validating the different methods by measurement of matrix certified reference materials (CRMs), and comparing the results obtained from real test samples and sample blanks to determine limits of detection. The results showed that the HBF4/HNO3 mixture provides the most viable alternative to the documentary standard preparation technique. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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1336 KiB  
Article
Effects of Binary Mixtures of Inducers (Toluene Analogs) and of Metals on Bioluminescence Induction of a Recombinant Bioreporter Strain
by In Chul Kong
Sensors 2014, 14(10), 18993-19006; https://doi.org/10.3390/s141018993 - 13 Oct 2014
Cited by 4 | Viewed by 4946
Abstract
This paper investigated the effects of binary mixtures of bioluminescence inducers (toluene, xylene isomers, m-toluate) and of metals (Cu, Cd, As(III), As(V), and Cr) on bioluminescence activity of recombinant (Pm-lux) strain KG1206. Different responses and sensitivities were observed [...] Read more.
This paper investigated the effects of binary mixtures of bioluminescence inducers (toluene, xylene isomers, m-toluate) and of metals (Cu, Cd, As(III), As(V), and Cr) on bioluminescence activity of recombinant (Pm-lux) strain KG1206. Different responses and sensitivities were observed depending on the types and concentrations of mixtures of inducers or metals. In the case of inducer mixtures, antagonistic and synergistic modes of action were observed, whereas metal mixtures showed all three modes of action. Antagonistic mode of action was most common for mixtures of indirect inducers, which showed bioluminescence ranging from 29% to 62% of theoretically expected effects (P(E)). On the other hand, synergistic mode of action was observed for mixtures of direct and indirect inducers, which showed bioluminescence between 141% and 243% of P(E). In the case of binary metal mixtures, bioluminescence activities were ranged from 62% to 75% and 113% to 164% of P(E) for antagonistic and synergistic modes of action, respectively (p-values 0.0001–0.038). Therefore, mixture effects could not be generalized since they were dependent on both the types and concentrations of chemicals, suggesting that biomonitoring may constitute a better strategy by investigating types and concentrations of mixture pollutants at contaminated sites. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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1538 KiB  
Article
Monoterpenes Released from Fruit, Plant, and Vegetable Systems
by Mohammad Asif Iqbal, Ki-Hyun Kim and Jeong Hyeon Ahn
Sensors 2014, 14(10), 18286-18301; https://doi.org/10.3390/s141018286 - 29 Sep 2014
Cited by 10 | Viewed by 6265
Abstract
To quantify the emission rate of monoterpenes (MTs) from diverse natural sources, the sorbent tube (ST)-thermal desorption (TD) method was employed to conduct the collection and subsequent detection of MTs by gas chromatography. The calibration of MTs, when made by both mass spectrometric [...] Read more.
To quantify the emission rate of monoterpenes (MTs) from diverse natural sources, the sorbent tube (ST)-thermal desorption (TD) method was employed to conduct the collection and subsequent detection of MTs by gas chromatography. The calibration of MTs, when made by both mass spectrometric (MS) and flame ionization detector (FID), consistently exhibited high coefficient of determination values (R2 > 0.99). This approach was employed to measure their emission rate from different fruit/plant/vegetable (F/P/V) samples with the aid of an impinger-based dynamic headspace sampling system. The results obtained from 10 samples (consisting of carrot, pine needle (P. sylvestris), tangerine, tangerine peel, strawberry, sepals of strawberry, plum, apple, apple peel, and orange juice) marked α-pinene, β-pinene, myrcene, α-terpinene, R-limonene, γ-terpinene, and p-cymene as the most common MTs. R-limonene was the major species emitted from citrus fruits and beverages with its abundance exceeding 90%. In contrast, α-pinene was the most abundant MT (37%) for carrot, while it was myrcene (31%) for pine needle. The overall results for F/P/V samples confirmed α-pinene, β-pinene, myrcene, α-terpinene, and γ-terpinene as common MTs. Nonetheless, the types and magnitude of MTs released from fruits were distinguished from those of vegetables and plants. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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375 KiB  
Article
A Study on N2O Measurement Characteristics Using Photoacoustic Spectroscopy (PAS)
by Soyoung Kang, Seoungjin Kim, Seongmin Kang, Jeongwoo Lee, Chang-Sang Cho, Jea-Hwan Sa and Eui-Chan Jeon
Sensors 2014, 14(8), 14399-14410; https://doi.org/10.3390/s140814399 - 7 Aug 2014
Cited by 14 | Viewed by 6900
Abstract
N2O, which is emitted mainly from nitrogen decomposition via bacteria, livestock manure, agricultural fertilizer use, fossil fuel combustion and waste incineration, is classified as a substance that causes significant destruction of the ozone layer. The N2O measurement methods for [...] Read more.
N2O, which is emitted mainly from nitrogen decomposition via bacteria, livestock manure, agricultural fertilizer use, fossil fuel combustion and waste incineration, is classified as a substance that causes significant destruction of the ozone layer. The N2O measurement methods for these emission sources may be divided into chromatography, optical, and electrical current measurements. Chromatography has been widely utilized for analyzing N2O. However, up until now, few studies have been conducted on N2O using photoacoustic spectroscopy. Therefore, this study aimed to evaluate performance of photoacoustic spectroscopy in this regard based on laboratory and field test results. The repeatability of photoacoustic spectroscopy was measured at 1.12%, which is lower than the repeatability of 3.0% suggested by the ISO 1564 standard, so, it has shown an excellent repeatability. The detection limit was determined to be 0.025 ppm, and the response time was confirmed to be 3 min and 26 s. The results of comparison between these measurements and GC show that the latter has superior accuracy, but mobility and convenience are superior for PAS. On the contrary, GC has a continuous measurement limitation, but PAS makes it possible to conduct continuous measurements. Therefore, PAS can be extremely useful to confirm the characteristics of N2O emissions and to quantify their amount. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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1405 KiB  
Article
An Odor Interaction Model of Binary Odorant Mixtures by a Partial Differential Equation Method
by Luchun Yan, Jiemin Liu, Guihua Wang and Chuandong Wu
Sensors 2014, 14(7), 12256-12270; https://doi.org/10.3390/s140712256 - 9 Jul 2014
Cited by 20 | Viewed by 6649
Abstract
A novel odor interaction model was proposed for binary mixtures of benzene and substituted benzenes by a partial differential equation (PDE) method. Based on the measurement method (tangent-intercept method) of partial molar volume, original parameters of corresponding formulas were reasonably displaced by perceptual [...] Read more.
A novel odor interaction model was proposed for binary mixtures of benzene and substituted benzenes by a partial differential equation (PDE) method. Based on the measurement method (tangent-intercept method) of partial molar volume, original parameters of corresponding formulas were reasonably displaced by perceptual measures. By these substitutions, it was possible to relate a mixture’s odor intensity to the individual odorant’s relative odor activity value (OAV). Several binary mixtures of benzene and substituted benzenes were respectively tested to establish the PDE models. The obtained results showed that the PDE model provided an easily interpretable method relating individual components to their joint odor intensity. Besides, both predictive performance and feasibility of the PDE model were proved well through a series of odor intensity matching tests. If combining the PDE model with portable gas detectors or on-line monitoring systems, olfactory evaluation of odor intensity will be achieved by instruments instead of odor assessors. Many disadvantages (e.g., expense on a fixed number of odor assessors) also will be successfully avoided. Thus, the PDE model is predicted to be helpful to the monitoring and management of odor pollutions. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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617 KiB  
Article
Response Characterization of a Fiber Optic Sensor Array with Dye-Coated Planar Waveguide for Detection of Volatile Organic Compounds
by Jae-Sung Lee, Na-Rae Yoon, Byoung-Ho Kang, Sang-Won Lee, Sai-Anand Gopalan, Hyun-Min Jeong, Seung-Ha Lee, Dae-Hyuk Kwon and Shin-Won Kang
Sensors 2014, 14(7), 11659-11671; https://doi.org/10.3390/s140711659 - 1 Jul 2014
Cited by 21 | Viewed by 8991
Abstract
We have developed a multi-array side-polished optical-fiber gas sensor for the detection of volatile organic compound (VOC) gases. The side-polished optical-fiber coupled with a polymer planar waveguide (PWG) provides high sensitivity to alterations in refractive index. The PWG was fabricated by coating a [...] Read more.
We have developed a multi-array side-polished optical-fiber gas sensor for the detection of volatile organic compound (VOC) gases. The side-polished optical-fiber coupled with a polymer planar waveguide (PWG) provides high sensitivity to alterations in refractive index. The PWG was fabricated by coating a solvatochromic dye with poly(vinylpyrrolidone). To confirm the effectiveness of the sensor, five different sensing membranes were fabricated by coating the side-polished optical-fiber using the solvatochromic dyes Reinhardt’s dye, Nile red, 4-aminophthalimide, 4-amino-N-methylphthalimide, and 4-(dimethylamino)cinnamaldehyde, which have different polarities that cause changes in the effective refractive index of the sensing membrane owing to evanescent field coupling. The fabricated gas detection system was tested with five types of VOC gases, namely acetic acid, benzene, dimethylamine, ethanol, and toluene at concentrations of 1, 2,…,10 ppb. Second-regression and principal component analyses showed that the response properties of the proposed VOC gas sensor were linearly shifted bathochromically, and each gas showed different response characteristics. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
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