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

Abstract

In groundwater, dissolved organic matter (DOM), a complex material, is a contaminant of concern owing to its ability to influence water quality and stimulate microbial metabolism. Using a 445-nm diode laser-induced fluorescence (LIF) spectroscopy, DOM contamination levels have been investigated of well water samples fetched from ten privately owned hand-dug wells during dry and wet seasons of 2016, 2017 and 2018, in Ghana. The results showed spatio-temporal heterogeneities in the LIF spectra, and the fluorescence intensity peaks were generally higher and broader during the wet season than the dry season. In this study, DOM fluorescence spectra at an emission wavelength band of 460-650 nm showed two distinct broad peak shoulders within 480-500 nm and 550-570 nm, engulfing the water Raman peak at 527 ± 2 nm for all the water samples studied. Furthermore, principal component analysis and cluster analysis were used to differentiate the 2016 water samples based on their DOM contamination levels. In each case, three groups or clusters were identified based on their similarities and dissimilarities. The study revealed humic DOM substances as the most typical well water fluorophores. Applying the K-nearest neighbour algorithm as a classifier method for the classification of 30 water samples studied in 2016, 16.7% (5/30) were classified as very good drinking water, 46.7% (14/30) as good, 26.7% (8/30) as fairly good, and 10% (3/30) as bad drinking water samples. In general, levels of dissolved organic matter contamination increased over the study period during the rainy seasons for wells situated in close proximity to septic tanks, refuse dumps, public toilets and in wetlands. Thus, in the study the fluorescence intensity depends on the sampling site and the season, and indicates the DOM contamination level.

Water quality assessment in mosquito breeding habitats based on dissolved organic matter and chlorophyll measurements by laser-induced fluorescence spectroscopy

“…The degree of nutrient pollution or eutrophication can be measured by the level of chlorophyll in the water [ 17 , 18 ]. Besides chlorophyll, the content of dissolved organic matter (DOM) in water bodies is another important water quality indicator [ 19 , 20 ]. DOM is the largest component of organic matter in the aquatic system and its levels and composition can be greatly influenced by nutrient pollution [ 21 ].…”

Assessment of Physicochemical Groundwater Quality and Hydrogeochemical Processes in an Area near a Municipal Landfill Site: A Case Study of the Toluca Valley

“…Currently, the quality of groundwater is a critical environmental problem and is generally evaluated by monitoring dissolved organic matter (DOM) by measuring dissolved organic carbon [4][5][6][7][8][9]. DOM is a parameter that can reflect the contamination of water by organic compounds of anthropogenic origin.…”

“…The organic matter of natural origin composed of humic and fulvic acids greatly influences the solubility and transport of harmful chemical contaminants. The high load of the latter can lead to the generation of carcinogenic by-products during disinfection processes [5,9,10]. The DOM present in the groundwater may differ from region to region, and the studies carried out to determine its origin report that it is predominantly derived from superficial garbage and soil, not from the aquifer matrix [5,9,11,12].…”

Removal of humic acid from aqueous solutions by a novel hydrogarnet/zeolite composite

“…Natural organic matter (NOM) present in water is formed via metabolic reactions and contains mainly humic substances, polysaccharides, and proteins. The contamination level of NOM in water is changed by the site and season [1]. High NOM levels in water can cause coloration and fouling of membranes used in ultrafiltration treatments for drinking water [2][3][4][5].…”