Technological applications of chlorophyll a fluorescence for the assessment of environmental pollutants

Chlorophyll a fluorescence has been extensively studied over the last few years. As demonstrated, this phenomenon is closely related to the state of photosystem II, which plays a leading role in the photosynthetic process, and therefore it has become a powerful tool to investigate this complex and any damage occurring in it as a result of physical or chemical stresses. This means that by using photosynthetic organisms as biological probes, one can consider chlorophyll a fluorescence as one of the techniques of choice to reveal the presence of some hazardous toxicants widely spread in the environment. Herbicides, pesticides, and heavy metals, whose concentration in water and food products is generally subject to extremely severe restrictions, are a concrete example of compounds detectable by chlorophyll a fluorescence. These dangerous substances react with the photosystem II, modifying the fluorescence emitted and giving responses which vary in a concentration-dependent manner. The possibility of performing easy, fast, and direct measurements of the fluorescence, even under light conditions, has opened new frontiers for the analysis in situ of pollutants. The aim of this review is to give an overview of the different techniques based on chlorophyll a fluorescence spectrometry, focusing in particular on those which represented the starting point for applications addressed to the assessment of toxic compounds in environmental samples.