Chromophoric Dissolved Organic Matter as a Tracer of Fecal Contamination for Bathing Water Quality Monitoring in the Northern Tyrrhenian Sea (Latium, Italy)

Abstract

<jats:p>Dissolved organic matter present in natural aquatic environments is a heterogeneous mixture of allochthonous and autochthonous materials. In coastal areas vulnerable to sewage waste, its biologically active component, the chromophoric dissolved organic matter (CDOM), is expected to change its composition and distribution in relation to anthropogenic activities, suggesting the possible use of CDOM as a proxy of fecal contamination. This study aimed at testing such hypothesis by investigating and relating the optical properties of CDOM with Escherichia coli abundance, physiological state, and enzymatic activities in a bathing area of the Northern Tyrrhenian Sea (Latium, Italy) affected by urban wastewaters. The parallel factor analysis (PARAFAC) applied to the excitation–emission matrices (EEMs) of CDOM allowed us to distinguish three main components: C1 (λEx/λEm = 342 nm/435 nm), C2 (λEx/λEm = 281–373 nm/460 nm), and C3 (λEx/λEm = 286 nm/360 nm). C1 and C2 corresponded to humic acids of terrestrial origin, while C3 to tryptophan, whose fluorescence peak was detected close to sewage sites, strongly related to active E. coli cells. The comparison between spectral and microbiological methods is suggested as a suitable approach to monitor bathing water quality for the implementation of coastal observing system capability.</jats:p>

Solid-Phase Extraction of Aquatic Organic Matter: Loading-Dependent Chemical Fractionation and Self-Assembly

“…Applying PARAFAC analysis to EEMs of discrete permeate samples resulted in six underlying components (Supporting Information Figure S1). Based on the fluorescence maxima, components C2, C3, and C5 can be attributed to terrestrial humic-like sources, − while C4 was previously interpreted as representing marine and microbial humic-like fluorophores (peak M). , C1 represents terrestrial and marine humic-like sources, ,, and C6 was categorized as a protein-like component (tryptophan-like peak T) with biological autochthonous origin. ,, The average extraction efficiency for all components varied from 88.0% at the beginning to 24.6% at the end. A cluster analysis based on six components revealed most pronounced changes of the permeate fluorescence after the first 0.5 and 2 L of extraction.…”

Development of a New Predictive index (Bathing Water Quality Index, BWQI) Based on Escherichia coli Physiological States for Bathing Waters Monitoring

“…In the perspective of environmental protection, this study represents a further step towards the set up of a coastal observing system, developing new management solutions and implementing the capability of the existing Civitavecchia Coastal Environment Monitoring System C-CEMS in forecasting potential pollution phenomena [14,15]. The development of a forecasting system integrated with in situ real-time measures would be fundamental to support local Authorities on the management of emergency discharge events, thus limiting the risk to bathers' health coming from fecal bacteria.…”

“…To set up the model taking into account the contribute of VBNC E. coli spread from a generic discharge point, a specific experiment was performed in the Santa Cecilia bathing area (Figure 1), close to Santa Marinella and considered as a suitable site to study the dynamics of untreated urban wastewaters into the sea [14]. In Santa Cecilia, two monitoring stations (SC0 and SC1) were strategically located in an area where wastewaters accumulate before their discharge into the sea and immediately in front of the outflow, respectively.…”

Bathing Water Quality Monitoring Practices in Europe and the United States

“…However, significant within-day variation in FIB concentrations, especially at coastal sites, means that intensive sampling of bathing waters for FIB is a prerequisite for building and testing models [ 94 ]. Numerous other potential approaches have been proposed for regulatory monitoring purposes such as measuring chromophoric dissolved organic matter with a spectrophotometer [ 95 , 96 ], and considering the distribution of living and dormant FIB abundance and their residence time in coastal water [ 97 ]. However, adopting new monitoring procedures for bathing water quality regulation is challenging.…”