Use of fallout radionuclides ((7)Be, (210)Pb) to estimate resuspension of Escherichia coli from streambed sediments during floods in a tropical montane catchment.
Consumption of water polluted by faecal contaminants is responsible for 2 million deaths annually, most of which occur in developing countries without adequate sanitation. In tropical aquatic systems, streambeds can be reservoirs of persistent pathogenic bacteria and high rainfall can lead to contaminated soils entering streams and to the resuspension of sediment-bound microbes in the streambed. Here, we present a novel method using fallout radionuclides ((7)Be and (210)Pbxs) to estimate the proportions of Escherichia coli, an indicator of faecal contamination, associated with recently eroded soil particles and with the resuspension of streambed sediments. We show that using these radionuclides and hydrograph separations we are able to characterize the proportion of particles originating from highly contaminated soils and that from the resuspension of particle-attached bacteria within the streambed. We also found that although overland flow represented just over one tenth of the total flood volume, it was responsible for more than two thirds of the downstream transfer of E. coli. We propose that data obtained using this method can be used to understand the dynamics of faecal indicator bacteria (FIB) in streams thereby providing information for adapted management plans that reduce the health risks to local populations. Graphical Abstract Graphical abstract showing (1) the main water flow processes (i.e. overland flow, groundwater return flow, blue arrows) and sediment flow components (i.e. resuspension and soil erosion, black arrows) during floods in the Houay Pano catchment; (2) the general principle of the method using fallout radionuclide markers (i.e. (7)Be and (210)Pbxs) to estimate E. coli load from the two main sources (i.e. streambed resuspension vs soil surface washoff); and 3) the main results obtained during the 15 May 2012 storm event (i.e. relative percentage contribution of each process to the total streamflow, values in parentheses).
Géosciences Environnement Toulouse (GET), UMR 5563 (CNRS-UPS-IRD), 14 avenue Edouard Belin, 31400, Toulouse, France. Olivier.ribolzi@ird.fr.
Olivier
O
Ribolzi
Laboratoire des Sciences du Climat et de l'Environnement (LSCE), UMR 8212 (CEA-CNRS-UVSQ/IPSL), Domaine du CNRS, avenue de la Terrasse, 91198, Gif-sur-Yvette cedex, France.
Olivier
O
Evrard
Université Pierre et Marie Curie (UPMC), UMR 7618 iEES (UPMC-CNRS-IRD-INRA-UDD-UPEC), case 120, 4 place Jussieu, 75252, Paris cedex, France.
Sylvain
S
Huon
Institut de Recherche pour le Développement (IRD), iEES-Paris, UMR 242, 32, avenue Henri Varagnat, 93143, Bondy cedex, France.
Emma
E
Rochelle-Newall
Institut de Recherche pour le Développement (IRD), iEES-Paris, UMR 242, 32, avenue Henri Varagnat, 93143, Bondy cedex, France.
Thierry
T
Henri-des-Tureaux
IRD, National Agriculture and Forestry Research Institute (NAFRI), P.O. Box 4199, Ban Nogviengkham, Xaythany District, Vientiane, Lao People's Democratic Republic.
Norbert
N
Silvera
IRD, National Agriculture and Forestry Research Institute (NAFRI), P.O. Box 4199, Ban Nogviengkham, Xaythany District, Vientiane, Lao People's Democratic Republic.
Chanthamousone
C
Thammahacksac
Department of Agricultural Land Management (DALaM), P.O. Box 4199, Ban Nogviengkham, Xaythany District, Vientiane, Lao People's Democratic Republic.
Oloth
O
Sengtaheuanghoung
D001608:Beryllium / Q000032:analysis*; D004784:Environmental Monitoring; D004926:Escherichia coli; D005243:Feces / Q000382:microbiology; D055868:Floods; D019015:Geologic Sediments / Q000382:microbiology*; D007854:Lead / Q000032:analysis*; D011847:Radioactive Fallout; D011868:Radioisotopes / Q000032:analysis*; D011891:Rain; D045483:Rivers / Q000382:microbiology*; D014329:Tropical Climate; D014873:Water Pollutants
D011847:Radioactive Fallout; D011868:Radioisotopes; D014873:Water Pollutants; D007854:Lead; D001608:Beryllium
Beryllium-7; Erosion; FIB; Hydrological modelling; Land use; Lead-210; Overland flow; South East Asia