Abstract
F-specific RNA bacteriophages (FRNAPHs) are commonly used as indicators of faecal and viral contamination in waters. Once they enter surface waters, the exact role of suspended solids, sediments and hydro-meteorological factors in their fluvial fate and transport is poorly understood, and long-term studies (e.g., over years) are lacking. In this study, FRNAPH concentrations and genogroup distribution were measured in the Orne River (France) during two years at weekly intervals, and during four storm runoff events. Hydro-meteorological driving factors were investigated at both time scales. FRNAPH concentrations and genogroups at different depths of a riverbank sediment core were also examined to better discriminate the origin of the faecal pollution. During low flows, the FRNAPH and the suspended solid transport were decoupled and the FRNAPH concentrations were mainly correlated with the air and water temperature. During storm runoff events, the FRNAPH concentrations only showed a significant correlation with conductivity, turbidity and water discharge. Despite the uncertainty of the predictions, multi parameter regression models using hydro-meteorological variables were suitable to predict log transformed FRNAPHs’ concentrations at low flows with a standard error of 0.46. Model performance using the storm runoff events dataset was low. This study highlights different driving factors at low flows and during storm runoff events, and the need to measure at both time scales to better understand phage transport dynamics in surface water.
Highlights
F-specific RNA bacteriophages (FRNAPHs) cannot grow outside their host cell, and their multiplication is unlikely in the environment due to the following parameters linked to bacteria host cells: low concentrations, the absence of receptor used by the phage (i.e., F-pili) and low metabolism [14,15]
The genotyping method allows for the discrimination of the origin of faecal pollution, since FRNAPH II and III are mostly found in human wastes and urban wastewater, while FRNAPH I and IV are in higher concentrations in animal wastes [17]
The data collected were used to determine (i) whether FRNAPHs were transported in association with suspended solids, (ii) whether the FRNAPH and suspended solids transport was controlled by the same hydro-meteorological drivers, (iii) whether those drivers were different at low flow and during storm runoff events and, (iv) whether it was possible to predict the FRNAPH concentrations from hydro-meteorological variables
Summary
The correlation was underlined between the concentration of FRNAPH II and the presence of human pathogenic viruses (adenovirus, norovirus) in rivers or oysters grown in polluted seawater [5,18] Once they reach the stream, viral particles are submitted to various biotic and abiotic stressors that drive their fate in aquatic environments, the most impacting being temperature and sunlight [19,20]. This, together with the large uncertainties of source and transport variables [32], hinders progress to assess and model viral pollution dynamics at a river basin scale In this respect, most of the microbial fate and transport models described far focused on faecal indicator bacteria [33,34], while only some include pathogens, allowing a direct assessment of health risks [35,36,37]. The data collected were used to determine (i) whether FRNAPHs were transported in association with suspended solids, (ii) whether the FRNAPH and suspended solids transport was controlled by the same hydro-meteorological drivers, (iii) whether those drivers were different at low flow and during storm runoff events and, (iv) whether it was possible to predict the FRNAPH concentrations from hydro-meteorological variables
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