the PIREN-Seine programme. Both qualitative and quantitative variations of DOM
have been related to hydrological conditions and specific geographical locations.
Furthermore, it has been demonstrated that EfDOM of the Paris conurbation, despite
the very significant improvement in wastewater treatment over the past 50 years,
had a very strong impact on DOM present downstream, both in terms of quantity
and quality, causing a significant increase in hydrophilicity downstream of the
agglomeration.
With regard to speciation and bioavailability of dissolved metals, these studies
have demonstrated the strong trace metal-binding ability of EfDOM in spite of its
low aromaticity. The remarkably high binding ability of EfDOM and especially of
its HPI fraction could be explained by its proteinic nature as well as high nitrogen
and sulphur group contents. Through modelling, it has been demonstrated that
EfDOM, due to their very high complexing properties, can control, to a large degree,
the dissolved trace metal speciation downstream of the Paris conurbation, particularly in low-water periods because of low EfDOM dilution. These results also
highlight that the trace metal speciation computation in surface water subjected
to important urban discharges should include not only the humic and/or fulvic part
of DOM but also other more hydrophilic fractions as depicted by EfDOM. Logically,
given the strong affinity of EfDOM for trace metals, these studies have pointed out
that EfDOM had a high influence on copper toxicity to Daphnia magna, with a
slightly greater protective effect than one fulvic acid standard and DOM from
the upstream Paris conurbation. Much research is still needed, however, in order
to fully understand how the shape and molecular structures constitutive of EfDOM
molecules favour the interactions between binding moieties and metallic pollutants.
With regard to pollutant-suspended particle interactions, our results highlight
that in many cases trace metal and PAH adsorption onto particles was strongly
modified in presence of DOM. Furthermore, the DOM influence on pollutant
adsorption depends on the DOM type. Hence, in addition to playing a central role
in dissolved metal speciation, EfDOM could also influence the pollutant transport in
aquatic systems as well as their transfers among aquatic compartments.
The combination of all these results indicates that it is essential to take into
account the great spatio-temporal variability of DOM properties to investigate
water quality and river system functioning. It also highlights that hydrophilic organic
matter from major WWTPs could play an important role in the biogeochemical cycle
of pollutants within aquatic systems under strong urban pressure.
Acknowledgements We sincerely thank Dr. Benoit Pernet-Coudrier, assistant professor at the
University of Western Brittany, who passed away accidentally in 2016. His PhD work has strongly
contributed to the study of interactions between DOM and metals discussed in this chapter.
This work was conducted in the framework of the PIREN-Seine research programme (www.
piren-seine.fr), a component of the Zone Atelier Seine within the international Long-Term Socio
Ecological Research (LTSER) network.
238
G. Varrault et al.
have been related to hydrological conditions and specific geographical locations.
Furthermore, it has been demonstrated that EfDOM of the Paris conurbation, despite
the very significant improvement in wastewater treatment over the past 50 years,
had a very strong impact on DOM present downstream, both in terms of quantity
and quality, causing a significant increase in hydrophilicity downstream of the
agglomeration.
With regard to speciation and bioavailability of dissolved metals, these studies
have demonstrated the strong trace metal-binding ability of EfDOM in spite of its
low aromaticity. The remarkably high binding ability of EfDOM and especially of
its HPI fraction could be explained by its proteinic nature as well as high nitrogen
and sulphur group contents. Through modelling, it has been demonstrated that
EfDOM, due to their very high complexing properties, can control, to a large degree,
the dissolved trace metal speciation downstream of the Paris conurbation, particularly in low-water periods because of low EfDOM dilution. These results also
highlight that the trace metal speciation computation in surface water subjected
to important urban discharges should include not only the humic and/or fulvic part
of DOM but also other more hydrophilic fractions as depicted by EfDOM. Logically,
given the strong affinity of EfDOM for trace metals, these studies have pointed out
that EfDOM had a high influence on copper toxicity to Daphnia magna, with a
slightly greater protective effect than one fulvic acid standard and DOM from
the upstream Paris conurbation. Much research is still needed, however, in order
to fully understand how the shape and molecular structures constitutive of EfDOM
molecules favour the interactions between binding moieties and metallic pollutants.
With regard to pollutant-suspended particle interactions, our results highlight
that in many cases trace metal and PAH adsorption onto particles was strongly
modified in presence of DOM. Furthermore, the DOM influence on pollutant
adsorption depends on the DOM type. Hence, in addition to playing a central role
in dissolved metal speciation, EfDOM could also influence the pollutant transport in
aquatic systems as well as their transfers among aquatic compartments.
The combination of all these results indicates that it is essential to take into
account the great spatio-temporal variability of DOM properties to investigate
water quality and river system functioning. It also highlights that hydrophilic organic
matter from major WWTPs could play an important role in the biogeochemical cycle
of pollutants within aquatic systems under strong urban pressure.
Acknowledgements We sincerely thank Dr. Benoit Pernet-Coudrier, assistant professor at the
University of Western Brittany, who passed away accidentally in 2016. His PhD work has strongly
contributed to the study of interactions between DOM and metals discussed in this chapter.
This work was conducted in the framework of the PIREN-Seine research programme (www.
piren-seine.fr), a component of the Zone Atelier Seine within the international Long-Term Socio
Ecological Research (LTSER) network.
238
G. Varrault et al.