Characterization of Chromophoric Dissolved Organic Matter (CDOM) in Rainwater Using Fluorescence Spectrophotometry

Abstract

The fluorescence excitation-emission matrix of Chromophoric dissolved organic matter (CDOM) samples from rainwater collected at Rameswaram, Tamilnadu, India are analysed. Total five peaks were observed for humic/marine and protein likes substances respectively. The peak A and C intensities varies form 1.98 ± 0.28 and 0.97 ± 0.11 QSU respectively represents humic like substances. The peak B and T intensities varies from 3.94 ± 0.75 and 7.42 ± 1.43 QSU showed association of protein like substances whereas peak M intensities varies from 1.92 ± 0.37 QSU indicates marine contribution. Among the fluorophores, the following sequence were observed as T > B > A > M > C which indicates dominance of Tryptophan like substances in rainwater. The average peak T/C ratios was observed as 7.88 ± 2.2 indicates microbial contamination by Tryptophan-like substances with the high biological activity and low volatility.

Absorption and fluorescence characteristics of rainwater CDOM and contribution to Lake Taihu, China

“…To define and classify the CDOM characteristics, we used the humification index (HIX: FI 254 ) and the index of recent autochthonous contribution (BIX: FI 310 ) (Huguet et al, 2009), which have proven effective in many studies (Salve et al, 2012;Zhang et al, 2010). FI 254 is defined as the ratio of the integrated fluorescence intensity of 435e480 nm to 300e345 nm (I 435e480 /I 300e345 ).…”

“…Although the composition and sources of rainwater CDOM have been studied (Kieber et al, 2006;Miller et al, 2009;Muller et al, 2008;Salve et al, 2012), there is limited knowledge of the dynamics, seasonal variations, material composition and controlling factors of rainwater CDOM in different regions of the world. Surprisingly, previous studies on rainwater CDOM have not focused on the most polluted regions of the world, and we are aware of few studies on rainwater CDOM in China (Cheng, 2010), even though China has high levels of atmospheric pollution and a high population density.…”

“…Recent studies have addressed the optical properties, composition, and potential sources of rainwater CDOM using three main techniques: (i) ultravioletevisible (UVeVis) spectral absorption, (ii) fluorescence excitationeemission matrices (EEMs), and (iii) nuclear magnetic-resonance spectroscopy (Kieber et al, 2006;Miller et al, 2009;Muller et al, 2008;Salve et al, 2012;Santos et al, 2009Santos et al, , 2013. UVeVis spectroscopy is an important tool to evaluate CDOM composition and structure semi-quantitatively, using spectral slope, spectral slope ratio, and molecular size (MS) (Peuravuori and Pihlaja, 1997;Zhang et al, 2011b).…”

Dissolved organic carbon transformations and microbial community response to variations in recharge waters in a shallow carbonate aquifer

“…Previous fluorescence studies of rain DOC composition indicate the ubiquitous presence and common dominance of tryptophan-like fluorescence (Muller et al 2008;Salve et al 2012;Santos et al 2012;Zhang et al 2014). As with the humic substances, tryptophanlike material is thought to be incorporated during cloud formation due to the presence of proteinaceous and biogenic matter in cloud waters (Muller et al 2008).…”

“…Atmospheric sources include bacteria, yeast, (Milne and Zika 1993;Determann et al 1996;Muller et al 2008). The presence of tryptophan-like material, along with relatively high BIX values (\0.8), has previously been used to infer a significant microbial-origin for atmospheric components within the rainfall (Salve et al 2012;Zhang et al 2014).…”