Distributed chemical sensing: An unexplored frontier in urban, industrial, and environmental monitoring

In many geoscience settings, chemical parameters in the subsurface can vary significantly in both space and time. Therefore, the traditional approach of point sampling followed by laboratory analysis often provides a poor representation of the conditions, resulting in inaccurate risk evaluation and management decisions. Real-time in situ sensor monitoring provides high temporal data density, which is invaluable in many situations. However, the expense of chemical point sensors, as well as their requirements for power and data handling, in many cases limit our ability to obtain high spatial data density. Fiber-optic sensing is the only available technology that offers both high temporal and spatial resolution in real-time, i.e., distributed sensing, with a single sensor. Currently, this technology is only available commercially to sense physical parameters of the fiber, which are temperature, acoustic fields, and strain. Here, we outline the vast potential for the development of distributed chemical sensing (DCS). The key to developing a DCS concept is the ability to relay a change in the chemical environment to a physical parameter that can be interpreted with distributed fiber-optic techniques. To date, only a few concepts have been demonstrated. However, with advances in, for example, material science and nanotechnology during the past decade, the number of potential DCS concepts is large. We outline some of the areas where DCS has significant potential to advance the state of the art in chemical sensing within the geosciences and discuss various potential DCS concepts worthy of further research.