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Optical Sensing for Environmental Monitoring

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

Deadline for manuscript submissions: closed (31 July 2022) | Viewed by 26610

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Special Issue Editors

Prof. Dr. Radhakrishna Prabhu

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Guest Editor

School of Engineering, Robert Gordon University, Aberdeen AB10 7GJ, UK
Interests: leakage detection; optical fibre-based sensors; robots; hollow core photonic crystal fibres; biosensors and instrumentation; environmental sensing and monitoring; clean technology
Special Issues, Collections and Topics in MDPI journals

Dr. Sandhya Devalla

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Guest Editor

Senior Analytical Chemist, The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, Scotland, UK
Interests: in development of analytical methodologies and assessments of organic and inorganic contaminants in different environmental compartments
Special Issues, Collections and Topics in MDPI journals

Dr. Carlos Fernandez

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Guest Editor

School of Pharmacy and Life Sciences, Robert Gordon University, Aberdeen AB107GJ, UK
Interests: nanomaterials; graphene and graphene-based compounds; energy storage devices; 2D materials; functional materials; sensors; environmental and pharmaceutical devices
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Environmental monitoring has become essential for human sustainability and for the efficient and safe use of environmental resources. Environmental monitoring typically involves sampling and analysing data with the help of sophisticated instruments to characterize and monitor the quality of the environment (air/water/soil). However, this usually involves sample collection , transport, storage and off-site analysis which may not be cost-effective and may alter sample characteristics. The use of sensors is fast gaining attraction because of their ability for in situ monitoring and rapid transmission of real-time data. Various types of sensors have been used for environmental monitoring, based on optical and spectroscopic (fluorescence, Raman, IR) techniques. Typical detection may involve monitoring of environmental changes in the ocean or atmosphere or nuclear/industrial facilities under harsh conditions, (e.g., subsea pipelines) in both the temporal and spatial domains. This may be carried out remotely, involving multiple parameters. Optical or optical fibre based sensors are emerging as potential for the environmental monitoring. Optical fibres have advantages like smaller size, immunity to electromagnetic interference, freedom from corrosion, chemical inertness and large bandwidth which can accommodate the growing needs of sensing and monitoring in challenging environments.

Current trends in environmental sensor development are to realise in-situ type, smaller, easy to use, and rapid sensors, with “smart” capabilities. The future sensor is expected to have high sensitivity and selectivity with real time monitoring or multi-analyte detection capability based on the “lab-on-a-chip” principle. This can simplify the analysis, reduce the cost and extend reliable monitoring outside the central laboratory. Optical biosensors based on bio-affinity molecules can provide very good sensitivity and selectivity for monitoring. This Special Issue will include featured research articles on environmental monitoring based on optical techniques.

Dr. Radhakrishna Prabhu
Dr. Sandhya Devalla
Dr. Carlos Fernandez
Guest Editors

Manuscript Submission Information

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Keywords

environmental sensor
optical sensor
optical fiber sensor
spectroscopy
biosensors
water/air/soil quality
oil & gas sensor

Published Papers (10 papers)

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Research

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10 pages, 3186 KiB

Open AccessCommunication

An Improved Acoustic Pick-Up for Straight Line-Type Sagnac Fiber Optic Acoustic Sensing System

by Jianjun Chen, Jiang Wang, Ning Wang, Juan Ruan, Jie Zhang and Yong Zhu

Sensors 2022, 22(21), 8193; https://0-doi-org.brum.beds.ac.uk/10.3390/s22218193 - 26 Oct 2022

Cited by 7 | Viewed by 1173

Abstract

An improved acoustic pick-up is presented to enhance the acoustic sensing sensitivity of the straight line-type Sagnac fiber optic acoustic sensing system. A hollow elastomer cylinder is introduced into the system, and the optical fiber is tightly wound around the cylinder to construct the pick-up. The theoretical analysis was finished, and it showed that the improved pick-up will bring in an extra phase change and let the phase difference increase almost an order. The extra phase change will enhance the sensing sensitivity correspondingly. The titanium alloy elastic cylinder was designed and manufactured. The experiment system was built, and a sinusoidal acoustic signal was used as the sound source. The tests were taken during 100–1500 Hz, and the experimental study showed that the sensitivity was more than 130 mV/Pa when the pick-up was used as the acoustic sensing element, and compared to the fiber only system, the sensitivity was enhanced more than 71.2%. The improved pick-up will be helpful in sound recognition and expand the application area of the Sagnac acoustic sensing system. Full article

(This article belongs to the Special Issue Optical Sensing for Environmental Monitoring)

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20 pages, 7305 KiB

Open AccessArticle

An Automated Optical Strain Measurement System for Estimating Polymer Degradation under Fatigue Testing

by Alexey A. Bogdanov, Sergey V. Panin, Pavel S. Lyubutin, Alexander V. Eremin, Dmitry G. Buslovich and Anton V. Byakov

Sensors 2022, 22(16), 6034; https://0-doi-org.brum.beds.ac.uk/10.3390/s22166034 - 12 Aug 2022

Cited by 7 | Viewed by 1416

Abstract

(1) Background: this study deals with design of an automated laboratory facility based on a servo-hydraulic testing machine for estimating parameters of mechanical hysteresis loops by means of the digital image correlation (DIC) method. (2) Methods: the paper presents a description of the testing facility, describes the grounds for calculating the elastic modulus, the offset yield strength (OYS) and the parameters of the mechanical hysteresis loops by the DIC method. (3) Results: the developed hardware-software facility was tested by studying the fatigue process in neat polyimide (PI) under various amplitude tension-tension loadings. It was found that the damage accumulation was accompanied by the decrease in the loop areas, while failure occurred when it reduced by at least ~5 kJ/m³. (4) Conclusions: it was shown that lowering the loop area along with changing the secant modulus value makes it possible to estimate the level of the scattered damage accumulation (mainly at the stresses above the OYS level). It was revealed that fractography data, namely the pattern and sizes of the fatigue crack initiation and propagation zones, did not correlate well with the dependences of the parameters of the hysteresis loops. Full article

(This article belongs to the Special Issue Optical Sensing for Environmental Monitoring)

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18 pages, 6660 KiB

Open AccessArticle

Detection of Oil in Seawater Based on the Fluorometric Index during the Winter Season in the Baltic Sea—The Case of the Gulf of Gdansk

by Emilia Baszanowska and Zbigniew Otremba

Sensors 2022, 22(16), 6014; https://0-doi-org.brum.beds.ac.uk/10.3390/s22166014 - 12 Aug 2022

Cited by 5 | Viewed by 1256

Abstract

This study is a continuation of analyses of the fluorometric index (FI), based on the fluorescence of substances of oil origin, as an indicator of oil in a seawater column. The effectiveness of the FI in the cold season (late autumn, winter and early spring) for the coastal water in the southern Baltic Sea was assessed. FI was tested for seawater polluted with a mixture of crude oils, lubricating oils and fuels. Laboratory analyses of oil–water systems for low (reaching the limit of detection) oil content in seawater were performed. The influences of the natural components of seawater that disrupt oil detection are discussed. The ability to detect oil in a seawater column regardless of the season was confirmed. Full article

(This article belongs to the Special Issue Optical Sensing for Environmental Monitoring)

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11 pages, 3823 KiB

Open AccessArticle

Real-Time Monitoring of SO₂ Emissions Using a UV Camera with Built-in NO₂ and Aerosol Corrections

by Yuanhui Xiong, Kuijun Wu, Guangbao Yu, Zhenwei Chen, Linmei Liu and Faquan Li

Sensors 2022, 22(10), 3900; https://0-doi-org.brum.beds.ac.uk/10.3390/s22103900 - 20 May 2022

Viewed by 1899

Abstract

Nitrogen dioxide (NO₂) absorption correction of the sulfur dioxide (SO₂) camera was demonstrated for the first time. The key to improving the measurement accuracy is to combine a differential optical absorption spectroscopy (DOAS) instrument with the SO₂ camera for the real-time NO₂ absorption correction and aerosol scattering correction. This method performs NO₂ absorption correction by the correlation between the NO₂ column density measurement of the DOAS and the NO₂ optical depth of the corresponding channel from the SO₂ camera at a narrow wavelength window around 310 and 310 nm. The error of correction method is estimated through comparison with only using the second channel of the traditional SO₂ camera to correct for aerosol scattering and it can be reduced by 11.3% after NO₂ absorption corrections. We validate the correction method through experiments and demonstrate it to be of greatly improved accuracy. The result shows that the ultraviolet (UV) SO₂ camera system with NO₂ absorption corrections appears to have great application prospects as a technology for visualized real-time monitoring of SO₂ emissions. Full article

(This article belongs to the Special Issue Optical Sensing for Environmental Monitoring)

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19 pages, 5260 KiB

Open AccessArticle

Chlorophyll-a Pigment Measurement of Spirulina in Algal Growth Monitoring Using Portable Pulsed LED Fluorescence Lidar System

by Jumar G. Cadondon, Prane Mariel B. Ong, Edgar A. Vallar, Tatsuo Shiina and Maria Cecilia D. Galvez

Sensors 2022, 22(8), 2940; https://0-doi-org.brum.beds.ac.uk/10.3390/s22082940 - 12 Apr 2022

Cited by 14 | Viewed by 2949

Abstract

Chlorophyll-a measurement is important in algal growth and water quality monitoring in natural waters. A portable pulsed LED fluorescence lidar system based on the preliminary algal organic matter and pigments excitation–emission matrix (EEM) of commercialized AZTEC Spirulina powder at varying concentrations was developed. Fluorescence peaks from EEMs showed increasing intensity as the Spirulina concentration increases. Using this information, an LED fluorescence lidar with a wavelength of 385 nm, pulse width of 10 ns, and repetition frequency of 500 kHz was constructed for chlorophyll detection at 680 nm. Turbidity measurements were also conducted at 700 nm emission wavelength at the same excitation wavelength. Range-resolved fluorescence lidar signals from the portable pulsed LED fluorescence lidar system are highly correlated with the standard methods such as optical density at 680 nm (R² = 0.87), EEM fluorescence chlorophyll-a pigment at 680 nm (R² = 0.89), and corrected chlorophyll-a concentration (R² =0.92). The F680/F700 lidar ratio was measured to provide a linear relationship of chlorophyll-a and turbidity in waters. The F680/F700 measurement showed strong correlations with Spirulina concentration (R² = 0.94), absorbance at 680 nm (R² = 0.84), EEM chlorophyll-a pigment at 680 nm (R² = 0.83), and corrected chlorophyll-a concentration (R² = 0.86). Results revealed that this new technique of chlorophyll-a measurement can be used as an alternative to other standard methods in algal growth monitoring. Full article

(This article belongs to the Special Issue Optical Sensing for Environmental Monitoring)

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17 pages, 5086 KiB

Open AccessArticle

Fluorometric Detection of Oil Traces in a Sea Water Column

by Emilia Baszanowska and Zbigniew Otremba

Sensors 2022, 22(5), 2039; https://0-doi-org.brum.beds.ac.uk/10.3390/s22052039 - 05 Mar 2022

Cited by 7 | Viewed by 1658

Abstract

This study focuses on broadening the knowledge of a fluorometric index to improve the detection of oil substances present in the marine environment. It is assumed that the value of this index will provide information about a possible oil discharge at some distance from the sensor. In this paper, the detection of oil present in seawater as a mixture of oils such as fuel, lubricate oil, or crude oil based on a fluorescence indicator-fluorometric index (FI_o/w) is discussed. FI_o/w was defined based on specific excitation and emission wavelengths coming from the obtained excitation–emission spectrum (EEM) of oil-free seawater and, in parallel, the same water but artificially polluted with oil. For this, measurements of a mixture of oils in seawater for an oil-to-water ratio in the range from 50 × 10⁻⁹ to 200 × 10⁻⁹ as well as oil-free seawater were performed. Laboratory measurements continued five times in months in the summer season with the coastal waters of the southern Baltic Sea (last spring, summer, and early autumn). The dependence of FI_o/w on the presence of oil in seawater, the oil-in-water ratio, as well as months of the considered season has been demonstrated. Full article

(This article belongs to the Special Issue Optical Sensing for Environmental Monitoring)

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9 pages, 12580 KiB

Open AccessArticle

A Versatile Multiple-Pass Raman System for Industrial Trace Gas Detection

by Chunlei Shen, Chengwei Wen, Xin Huang and Xinggui Long

Sensors 2021, 21(21), 7173; https://0-doi-org.brum.beds.ac.uk/10.3390/s21217173 - 28 Oct 2021

Cited by 5 | Viewed by 1646

Abstract

The fast and in-line multigas detection is critical for a variety of industrial applications. In the present work, we demonstrate the utility of multiple-pass-enhanced Raman spectroscopy as a unique tool for sensitive industrial multigas detection. Instead of using spherical mirrors, D-shaped mirrors are chosen as cavity mirrors in our design, and 26 total passes are achieved in a simple and compact multiple-pass optical system. Due to the large number of passes achieved inside the multiple-pass cavity, experiments with ambient air show that the noise equivalent detection limit (3σ) of 7.6 Pa (N₂), 8.4 Pa (O₂) and 2.8 Pa (H₂O), which correspond to relative abundance by volume at 1 bar total pressure of 76 ppm, 84 ppm and 28 ppm, can be achieved in one second with a 1.5 W red laser. Moreover, this multiple-pass Raman system can be easily upgraded to a multiple-channel detection system, and a two-channel detection system is demonstrated and characterized. High utilization ratio of laser energy (defined as the ratio of laser energy at sampling point to the laser output energy) is realized in this design, and high sensitivity is achieved in every sampling position. Compared with single-point sampling system, the back-to-back experiments show that LODs of 8.0 Pa, 8.9 Pa and 3.0 Pa can be achieved for N₂, O₂ and H₂O in one second. Methods to further improve the system performance are also briefly discussed, and the analysis shows that similar or even better sensitivity can be achieved in both sampling positions for practical industrial applications. Full article

(This article belongs to the Special Issue Optical Sensing for Environmental Monitoring)

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16 pages, 2430 KiB

Open AccessArticle

An Advanced Sensor for Particles in Gases Using Dynamic Light Scattering in Air as Solvent

by Dan Chicea, Cristian Leca, Sorin Olaru and Liana Maria Chicea

Sensors 2021, 21(15), 5115; https://0-doi-org.brum.beds.ac.uk/10.3390/s21155115 - 28 Jul 2021

Cited by 6 | Viewed by 2243

Abstract

Dynamic Light Scattering is a technique currently used to assess the particle size and size distribution by processing the scattered light intensity. Typically, the particles to be investigated are suspended in a liquid solvent. An analysis of the particular conditions required to perform a light scattering experiment on particles in air is presented in detail, together with a simple experimental setup and the data processing procedure. The results reveal that such an experiment is possible and using the setup and the procedure, both simplified to extreme, enables the design of an advanced sensor for particles and fumes that can output the average size of the particles in air. Full article

(This article belongs to the Special Issue Optical Sensing for Environmental Monitoring)

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16 pages, 1161 KiB

Open AccessCommunication

Tackling Heterogeneous Color Registration: Binning Color Sensors

by Paul Myland, Sebastian Babilon and Tran Quoc Khanh

Sensors 2021, 21(9), 2950; https://0-doi-org.brum.beds.ac.uk/10.3390/s21092950 - 22 Apr 2021

Cited by 5 | Viewed by 2295

Abstract

Intelligent systems for interior lighting strive to balance economical, ecological, and health-related needs. For this purpose, they rely on sensors to assess and respond to the current room conditions. With an augmented demand for more dedicated control, the number of sensors used in parallel increases considerably. In this context, the present work focuses on optical sensors with three spectral channels used to capture color-related information of the illumination conditions such as their chromaticities and correlated color temperatures. One major drawback of these devices, in particular with regard to intelligent lighting control, is that even same-type color sensors show production related differences in their color registration. Standard methods for color correction are either impractical for large-scale production or they result in large colorimetric errors. Therefore, this article shows the feasibility of a novel sensor binning approach using the sensor responses to a single white light source for cluster assignment. A cluster specific color correction is shown to significantly reduce the registered color differences for a selection of test stimuli to values in the range of 0.003–0.008

Δ u^{'} v^{'}

, which enables the wide use of such sensors in practice and, at the same time, requires minimal additional effort in sensor commissioning. Full article

(This article belongs to the Special Issue Optical Sensing for Environmental Monitoring)

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Review

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39 pages, 5598 KiB

Open AccessReview

Recent Advances on Detection of Insecticides Using Optical Sensors

by Nurul Illya Muhamad Fauzi, Yap Wing Fen, Nur Alia Sheh Omar and Hazwani Suhaila Hashim

Sensors 2021, 21(11), 3856; https://0-doi-org.brum.beds.ac.uk/10.3390/s21113856 - 03 Jun 2021

Cited by 18 | Viewed by 8401

Abstract

Insecticides are enormously important to industry requirements and market demands in agriculture. Despite their usefulness, these insecticides can pose a dangerous risk to the safety of food, environment and all living things through various mechanisms of action. Concern about the environmental impact of repeated use of insecticides has prompted many researchers to develop rapid, economical, uncomplicated and user-friendly analytical method for the detection of insecticides. In this regards, optical sensors are considered as favorable methods for insecticides analysis because of their special features including rapid detection time, low cost, easy to use and high selectivity and sensitivity. In this review, current progresses of incorporation between recognition elements and optical sensors for insecticide detection are discussed and evaluated well, by categorizing it based on insecticide chemical classes, including the range of detection and limit of detection. Additionally, this review aims to provide powerful insights to researchers for the future development of optical sensors in the detection of insecticides. Full article

(This article belongs to the Special Issue Optical Sensing for Environmental Monitoring)

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