Tracing the sources of suspended sediment and particle-bound trace metal elements in an urban catchment coupling elemental and isotopic geochemistry, and fallout radionuclides

Abstract

The excessive supply of contaminants from urban areas to rivers during the last centuries has led to deleterious impacts on aquatic ecosystems. The sources, the behavior, and the dynamics of these contaminants must be better understood in order to reduce this excessive anthropogenic pollution. Accordingly, the current research investigated the particle-bound trace element (TE) contamination of the 900-km2 Orge River (Seine basin, France) and the potential sources of these particles (agricultural or forest soils, channel banks, road deposited sediments), through the analysis of multiple fallout radionuclides, elemental geochemistry, and lead isotopic composition on suspended particulate matter (SPM) collected during a hydrological year at four stations following an increasing urbanization gradient (300 to 5000 inhab.km−2). Fallout radionuclide measurements showed an increasing contribution of recently eroded particles from urban areas to the SPM in downstream direction. However, this contribution varied depending on hydrological conditions. A greater contribution of particles originating from urban areas was observed during low stage periods. On the contrary, the contribution of agricultural soils and channel banks that are less enriched in contaminants and fallout radionuclides was higher during seasonal floods, which explained the dilution of radionuclide contents in sediment transiting the river during those events. Trace element contamination of SPM in Cu, Zn, Pb, and Sb increased from moderate to significant levels with urban pressure in downstream direction (with corresponding enrichment factors raising from 2 to 6). In addition, Pb isotopic ratios indicated that the main source of Pb corresponded to the “urban” signature found in road deposited sediments. The low variations in lead isotope ratios found in the SPM for contrasting hydrological conditions demonstrated the occurrence of a single source of Pb contamination. These results demonstrate the need to better manage urban runoff during both flood and low precipitation events to prevent the supply of diffuse particle-bound contamination to rivers draining urban areas.Electronic supplementary materialThe online version of this article (10.1007/s11356-018-2892-3) contains supplementary material, which is available to authorized users.

Innovative combination of tracing methods to differentiate between legacy and contemporary PAH sources in the atmosphere-soil-river continuum in an urban catchment (Orge River, France)

“…Fallout radionuclide concentrations measured in the Orge River SPM were reported in a previous paper (Froger et al, 2018) and showed a linear increase in 7 Be and 210 Pb xs activities in SPM collected in downstream direction (Fig. S2).…”

“…All river water, atmospheric and road sediments samples were collected in the Orge River catchment, which is located 30 km south of Paris City and drains into the Seine River ( Figure 1; see Froger et al, 2018). Four sampling sites were selected based on their urbanization rate and previous work on the catchment (Le Pape et al, 2012): three were located on the main stem of the Orge River, whereas a fourth site was located on its main tributary, the Yvette River.…”

“…The transfer time of particles from urban surfaces to the river appears to be crucial, as it may affect to a large extent the PAH degradation rate. In the Orge River system, the fast transfer of particles once they have been supplied to the river (Froger et al, 2018) likely reduces the potential degradation of particulate PAHs in the river because of the absence of sediment storage in the channel in downstream sections of the river. This specific context likely explains the good match observed between the modelled signature of TUP and that of urban runoff particles collected in storm sewers.…”

“…The objective of the current research was to identify the PAH sources and pathways in an urban catchment and to differentiate between legacy and current PAH sources, through the investigation of PAH contamination in the atmosphere, the soil and the river during a hydrological year. To achieve this goal, the Orge River catchment was selected as it is representative of urbanized catchments (Froger et al, 2018) and located in an early industrialized region. Source identification using PAH diagnostic ratios was combined with new approaches such as PAH correlations and the measurement of fallout radionuclides used for sediment fingerprinting to better discriminate both sources and pathways of particle-bound PAH in the atmosphere, the soils and the river.…”

Raman spectroscopy to investigate the speciation and origin of hazardous elements associated to suspended particulate matter during a large flood event

“…Moderately contamination by Cu, Zn, Sb, and Pb, was also found in SPM collected in an urban river in the Orge River catchment (a subcatchment of the Seine River basin located 30-km south of Paris City). [12] The resuspension of SPM previously accumulated in the bottom is another source of HEs in rivers during flood events. [13] Therefore, understanding the distribution and composition of SPM in rivers is, clearly, a matter of high concern.…”