The use of sensor arrays for environmental monitoring: interests and limitations

Abstract

Continuous, in situ monitoring of air, water and land quality is fundamental to most environmental applications. Low cost and non-invasive chemical sensor arrays provide a suitable technique for in situ monitoring. Their ability and performance under realistic conditions is discussed in this paper. Published studies report promising results despite a number of limitations that are associated with both the technology itself and its application in ever changing ambient conditions. Early investigations include the analysis of single substances as well as odour and wastewater organic load monitoring. Reported applications typically highlight the sensitivity of the currently available sensors to changes in temperature, humidity and flow rate. Two types of approaches are recommended to deal with these effects: either working under fixed experimental conditions or measuring the external parameters to numerically compensate for their change. The main challenge associated with the use of non-specific sensor arrays lies in establishing a relationship between the measured multivariate signals and the standards metrics that are traditionally used for quality assessment of gas mixtures. For instance, odour monitoring requires calibration against olfactometric measurements while investigations of wastewater samples still need to be correlated with organic pollution parameters such as BOD, COD or TOC. On the other hand, results obtained in the field have demonstrated how sensor arrays can be readily used as simple alarm devices or as early warning systems based on a general air/water quality index.

Predictive intelligence to the edge through approximate collaborative context reasoning

“…The Algorithm 2, at every time instance t, calculates the outlier indicator I t using (16), which requires O(1), given the closest pattern w * , which requires O(d log K). When the optimal stopping criterion holds true, which is determined in O(1) time, then the closest pattern w * is either updated or a new pattern is inserted in the pattern set W in O (1). In the adaptation, the dynamic vigilance ρ * is updated in O(dK).…”

“…Hence, the required number of iterations is L = log χ 1 ξ min +1, which maps to O(1) iterations. Now, if node i starts the election process with ξ i > ξ min then O (1) iterations are the maximum number of steps for the election process.…”

“…Events are related to critical aspects, e.g., security issues or violations of predefined constraints. For instance, in security and environmental monitoring applications, a monitoring infrastructure is imperative to apply an efficient mechanism to derive alerts when specific criteria are satisfied [1,8,10,12,23]. We can identify two main orientations in terms of data acquisition, transfer and contextual reasoning: -Orientation 1: Centralized Context Reasoning.…”

Reliable Long-Term Data from Low-Cost Gas Sensor Networks in the Environment

“…Low-cost sensors are increasingly being used in environmental research [1]. They offer flexibility and opportunity to explore hypotheses previously too difficult to test [2].…”

Optical Sensing Performance of Multimode Polymer Optical Fiber (POF) Coated with ZnO towards Methanol Vapour

“…Measurement of chemical contamination is required in a numerous of applications, including the water contamination, chemical, and food processing industry. [1] Thus, the chemical compound contamination measurement has been extensively studied over the last many years, and a remarkable progress in employing optical fiber sensor for the growth of volatile organic compound sensors has been developed. [2] However, potentially competent electronic based sensor as conventional technique e.g., capacitance based, wet-dry bulb and solid-state humidity sensors are also widely deployed and comprehensively practice in targeting the present of volatile organic compounds.…”