A first inventory of the labile biochemicals found in Avignon groundwater: can we identify potential bacterial substrates?

Ludivine Rousset,Christos Panagiotopoulos,Mounir Traikia,Catherine Duport,Odile Berge,Thierry Clavel,Marie Lagrée,Marina Gillon

doi:10.1051/e3sconf/20198802001

Abstract

Groundwater is a major source of water for irrigation of vegetables, especially in the Mediterranean basin. Contamination of aquifer by pathogens has been responsible for numerous disease outbreaks worldwide. Several studies reported that groundwater dissolved organic matter (DOM) can serve as a source of carbon and energy for heterotrophic metabolism of pathogens. In this study, we aimed to investigate the DOM composition of groundwater collected at Avignon. Six liters of groundwater were filtered (0.2 µm) and freeze-dried following appropriate cleaning procedure. The bulk analyses of powder sample were performed using 1D and 2D nuclear magnetic resonance spectroscopy and liquid chromatography coupled with mass spectroscopy. Several components were found at concentrations around 1 µM and comprise: (i) humic and fulvic acids originated from land-derived material or soils and, (ii) various acids, esters and alcohols of different sizes including acetate, lactate and formate, these may result from microbial metabolism. In conclusion, the Avignon groundwater DOM contains a heterogeneous mixture of dissolved organic components with a rather low potential bioreactivity based on the low level of labile biogeochemicals such as carbohydrates.

Highlights

Water is the main limiting factor for agriculture in Mediterranean basin due to arid and semi-arid climate
Analysis of the six samples collected from site n°33 at various dates confirmed that the physico-chemical parameters of Avignon groundwater are relatively stable [4] especially in terms of temperature, pH, dissolved oxygen and electrical conductivity (Table 1)
The very low levels of bacterial populations and Dissolved Organic Carbon (DOC) concentration illustrated the oligotrophic status of Avignon groundwater

Summary

Introduction

Water is the main limiting factor for agriculture in Mediterranean basin due to arid and semi-arid climate. Surface water resources are more and more limited in these areas and aquifers are considered as major sources of water for irrigation. The factors that are the most influential in occurrence, survival, dynamic and dispersion of pathogenic bacteria in groundwater are not well understood especially in the agricultural context. Among these factors, there are dissolved oxygen, temperature, pH, pollutants, biological interaction and Dissolved Organic Matter (DOM). DOM is composed of two fractions: the labile or biodegradable fraction, a potential carbon and energy source for heterotrophic pathogens [2] and the refractory fraction considered relatively less important for bacterial growth. The labile fraction consists mainly of sugars, amino acids, peptides and other simple compounds while the refractory fraction is composed mainly of high molecular weight molecules such as humic and fulvic acids

Objectives

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Conclusion