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Article by: Leo Sprincean, on 19 August 2023 at 06.03 am PDT

Have you ever wondered how scientists determine a change in a heterogeneous medium without directly interfering with it?

Actually, there are many ways that scientists can do this, although the most practical one is through the usage of the so-called - chemical sensors.

Chemical sensors have emerged as a revolutionary technology in the realm of environmental monitoring, offering precise and rapid detection of specific chemicals or molecules. These sensors play a crucial role in safeguarding the environment by providing real-time data on pollutants, contaminants, and hazardous substances. Their sensitivity and selectivity have paved the way for a wide range of applications, making them indispensable tools for researchers, regulatory bodies, and industries alike.

Air Quality Monitoring

One of the most prominent applications of chemical sensors is in air quality monitoring. Pollutants such as nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), carbon monoxide (CO), and particulate matter can severely impact human health and the environment. Chemical sensors deployed in urban areas, industrial sites, and near traffic zones can continuously monitor these pollutants and provide data for assessing air quality levels. For instance, the "Air Quality Egg", a community-driven project, which grew out of Internet of Things meetup groups in New York City and Amsterdam, led by Pachube evangelist Ed Borden, uses chemical sensors to monitor air quality. The device measures particulate matter (PM2.5 and PM10), carbon monoxide (CO), nitrogen dioxide (NO2), and temperature and humidity. Data collected by these sensors help citizens and authorities track air pollution levels in their neighborhoods and make informed decisions to improve air quality.

Water Quality Assessment

Chemical sensors are also integral to water quality assessment efforts. Contaminants such as heavy metals, organic pollutants, and pathogens can compromise water safety. In freshwater bodies, sensors equipped with biosensing technology can detect harmful algal blooms by targeting specific metabolites or toxins produced by the algae. These sensors aid in early warning systems, allowing authorities to take timely action to mitigate potential water contamination and protect aquatic ecosystems. Furthermore, this type of chemical sensor is the most accessible due to the critical demand for them on the market. The YSI ProDSS (Digital Sampling System) is a portable water quality sensor that measures various parameters including dissolved oxygen, turbidity, pH, conductivity, and chlorophyll-a fluorescence. It is widely used in environmental research and management to assess the health of water bodies like lakes, rivers, and oceans.

Industrial Emissions Monitoring

Industries that produce chemical emissions are required to comply with regulations and minimize their environmental impact. Chemical sensors are employed to monitor and quantify emissions of volatile organic compounds (VOCs) and other pollutants from industrial processes. These sensors contribute to the enforcement of emission standards and assist industries in optimizing their production processes to reduce pollution. One example of a versatile gas analyzer used for monitoring emissions in industrial processes is the Gasmet DX4000. It can simultaneously measure multiple gases, including volatile organic compounds (VOCs) and hazardous air pollutants, helping industries comply with emissions regulations and reduce environmental impact.

Hazardous Gas Detection

Chemical sensors play a pivotal role in detecting hazardous gases in confined spaces and workplaces. For instance, hydrogen sulfide (H2S) is a toxic gas commonly found in industries such as oil and gas, wastewater treatment, and mining. Sensors designed to detect H2S provide workers with vital information about potentially unsafe environments, ensuring their safety and well-being. For instance, the BW GasAlert MicroClip is a wearable gas detector commonly used in workplaces where exposure to hazardous gases like hydrogen sulfide (H2S) is a concern. It provides real-time readings and alarms to protect workers from potentially dangerous environments.

Precision Agriculture

In the realm of agriculture, chemical sensors are used to monitor soil health and nutrient levels. Nitrate and phosphate sensors, for example, help farmers optimize fertilizer application, minimizing nutrient runoff and its adverse effects on water bodies. One of the most used handheld devices that uses near-infrared spectroscopy to analyze soil samples is the SoilCares Scanner. It measures nutrient levels such as nitrogen, phosphorus, and potassium, helping farmers optimize fertilizer application and reduce nutrient runoff.

As technology continues to advance, chemical sensors are becoming more compact, cost-effective, and integrated with data analysis tools. This enables real-time monitoring, data-driven decision-making, and the ability to address environmental challenges with greater precision. Chemical sensors hold the promise of a greener and healthier future, where timely and accurate detection of pollutants contributes to sustainable resource management and environmental preservation. 

Resources

• Sadik, O. A., & Mulchandani, A. (2000). Chemical and Biological Sensors: Meeting the challenges of environmental monitoring. In ACS Symposium Series (pp. 1–6). https://doi.org/10.1021/bk-2000-0762.ch001
  
• Long, F., Zhu, A., & Shi, H. (2013). Recent Advances in Optical Biosensors for Environmental Monitoring and Early Warning. Sensors, 13(10), 13928–13948. https://doi.org/10.3390/s131013928
  
• Gründler, P., & Karschin, H. H. (2007). Chemical Sensors: An Introduction for Scientists and Engineers. Springer Science and Business Media.