In situ fluorescence measurements of dissolved organic matter: A review

Abstract

There is a need for an inexpensive, reliable and fast monitoring tool to detect contaminants in a short time, for quick mitigation of pollution sources and site remediation, and for characterisation of natural dissolved organic matter (DOM). Fluorescence spectroscopy has proven to be an excellent technique in quantifying aquatic DOM, from autochthonous, allochthonous or anthropogenic sources. This paper reviews the advances in in situ fluorescence measurements of DOM and pollutants in various water environments. Studies have demonstrated, using high temporal-frequency DOM fluorescence data, that marine autochthonous production of DOM is highly complex and that the allochthonous input of DOM from freshwater to marine water can be predicted. Furthermore, river measurement studies found a delayed fluorescence response of DOM following precipitation compared to turbidity and discharge, with various lags, depending on season, site and input of dissolved organic carbon (DOC) concentration. In addition, research has shown that blue light fluorescence (emission = 430-500 nm) can be a good proxy for DOC, in environments with terrestrial inputs, and ultraviolet fluorescence (emission = UVA-320-400 nm) for biochemical oxygen demand, and also E. coli in environments with sanitation issues. The correction of raw fluorescence data improves the relationship between fluorescence intensity and these parameters. This review also presents the specific steps and parameters that must be considered before and 2 during in situ fluorescence measurement session for a harmonised qualitative and quantitative protocol. Finally, the strengths and weaknesses of the research on in situ fluorescence are identified.

Monitoring Approaches for Faecal Indicator Bacteria in Water: Visioning a Remote Real-Time Sensor for E. coli and Enterococci

“…Fluorescence measurement is inexpensive and reagentless and often requires little sample preparation; it is highly sensitive and non-invasive and allows the detection and characterisation of proteins, microorganisms, and inorganic, natural, and organic matter in water [62,68,72,73]. Fluorescence measurement instrumentation includes spectrofluorometers, microplate readers, fluorescence microscopes, fluorescence scanners (including microarray readers), and flow cytometers [36,69].…”

“…In contrast with standard water-testing procedures, the fluorescence measurement enables fast or near-instantaneous results, and it can be used with or without reagents, thus reducing costs; however, currently, for E. coli and enterococci, results can be delayed by sample collection, preprocessing, and fluorescence measurement in laboratories [8,38,74]. Furthermore, most typical fluorescence sensors are bulky and expensive and are commonly affected by optical inferences; findings have shown that miniaturisation, filters, and compensation algorithms could overcome such limitations, but more experimentation is required [62,72,73].…”

“…Fluorescence spectroscopy directly measures the specific fluorescence emission at a wavelength range produced by materials after excitation, and results are commonly expressed in fluorescence excitation-emission matrix (EEM) plots [34,62,72,73,75] or through an absolute value if a specific excitation-emission pair is targeted based on known properties of the target parameter. The use of fluorescence spectroscopy as a final assessment tool to assess water quality in surface and ground waters has been reported and reviewed widely [34].…”

“…Portable fluorescence spectroscopy (PFS) devices, incorporated into floating buoys or mobile sensors, utilise the intrinsic fluorescence properties of substances and organisms [34,73,75], and results can be displayed in EEMs (refer to Table A1). Using an experimental PFS device, several reports have found that the fluorescence pair with 280 nm excitation and 350 nm emission correlated well to the E. coli presence and biochemical oxygen demand (BOD) of sewage-impacted waters and waters affected by low sanitation [23,34,76].…”

Dissolved organic matter in hand-dug well water as groundwater quality indicator: assessment using laser-induced fluorescence spectroscopy and multivariate statistical techniques

“…Water of all kinds fluoresces [9], because only absorbing molecules can emit fluorescence. Carstea et al [12] have posited that fluorescence spectroscopy an inexpensive, reliable, excellent technique and fast monitoring tool is used to detect and quantify contaminants in a short time, for quick mitigation of pollution sources and site remediation, and for characterization of natural dissolved organic matter. In other words, fluorescence spectroscopy has proven to be an excellent technique in quantifying aquatic DOM, from autochthonous, allochthonous, or anthropogenic sources [38].…”