Présentations Colloques

    Oral Presentation
    Session 7.03: Agricultural and sanitation contaminants and implications for water services and health
    Huang Shuangbing
    NH4+ occurrence in subsurface aquifer: to assess the association of NH4-N with OMs in aquifers of Jianhan Plain, China
    NH4-N contamination in subsurface aquifers has been increasingly reported and for many cases, assumed to be associated with sediment organic matter (SOM). Thus, the specific mechanism of natural occurrence of ammonium is necessary to be assessed. We investigated NH4-N concentration, its spatial distribution and assessed the binding mechanism of ammonium with organic matter (OM) for groundwater of Jianhan Plain by combing areal investigation with experimental studies. **A widespread and accompanying occurrence of ammonium with organic matter (OM) was observed in the groundwater. NH4-N concentrations of most of groundwater were 1-8 mg L while those of DOC were 3-7mg L.**Our experiment study firstly revealed the close relationships of NH4+ with specific OM components both on sediment and also in groundwater. High significant correlation relationships (p<0.001) at different levels were observed between NH4+ and various fluorescent DOM components for sediments extracted DOM solutions and groundwater samples. We then designed complexation experiments to investigate affinity of NH4+ with aqueous DOM (i.e., groundwater DOM) by employing techniques of advanced spectroscopies (differential adsorption spectroscopy and PARAFAC-EEM) and model predication of thermodynamics equilibrium. The results demonstrated consistent variations in spectrum signals with the binding levels of NH4+ to DOM. Based on the results presented, we believe the close relationships of NH4+ with OM on solid phase of sediments could be related with both effects of electrostatic sorption and physical assemblage, while the affinity relationship in aqueous solution is mainly caused by the binding of NH4+ to OM functional groups ligands.**Our investigation revealed widespread and accompanying occurrence of NH4+ with OM in aquifers. The assessment to binding mechanism of NH4+ with OM demonstrated the significant binding ability of OM components to NH4+ both on sediments and in groundwater. Thus the considerations of potential mitigation measures for naturally occurred NH4+ should include the associations of ammonium with OM.


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