A dual isotope approach to identify denitrification in groundwater at a river-bank infiltration site

Nitrate sources and dynamics in a salinized river and estuary – a δ<sup>15</sup>N–NO<sub>3</sub><sup>−</sup> and δ<sup>18</sup>O–NO<sub>3</sub><sup>−</sup> isotope approach

“…It is clear that in the upstream part of the HH River before the floodgate F1, NO (Mariotti et al, 1981;Mayer et al, 2002;Fukada et al, 2003). Some studies reported that a linear relationship indicating an enrichment of 15 N relative to 18 O by a factor between 0.8 and 2.0 gives evidence for denitrification (Aravenaand and Robertson, 1998;Fukada et al, 2003;Xue et al, 2009) and 1.0 for assimilation (Granger et al, 2004).…”

“…The third one with mean salinity around 2.2 flows through Tianjin municipality and is separated into three parts by two floodgates crossing the river, for providing water supply for the residents living along the river bank. Since the rapid urbanization and population growth in Tianjin municipality, NO − 3 loading has progressively increased in rivers and estuaries associated with human activities such as agricultural runoff: untreated domestic and industrial wastewater (Gao et al, 2011). Furthermore, port construction and reclamation projects along the coastline of the municipality aggravate NO − 3 pollution (Zhang et al, 2004).…”

Residence times and mixing of water in river banks: implications for recharge and groundwater–surface water exchange

“…6), which would be not be expected for a KCl source; however, K may be removed from waters recharging through the soils by vegetation (e.g. Schachtman and Schroder, 1994) or sorption onto clay minerals such as illite (Griffioen, 2001). In any case, the observation that increased Cl concentrations coincide with increased rainfall suggests that infiltration facilitates the transport of Cl from the land surface and/or the soil profile into shallow groundwater (cf.…”

“…Fukada et al (2003) identified the continuing denitrification of river water as it infiltrated an alluvial aquifer and demonstrated that the chemistry of infiltrating water is likely to vary according to its residence time within the alluvial aquifer. Understanding the source and load of nutrients in rivers is fundamental in understanding their ecology (Boulton, 1993(Boulton, , 2005, while determining the different sources of water in the riparian zone is crucial to effective vegetation management (Cey et al, 1999;Lambs, 2004;Lamontagne et al, 2005;Woessner, 2000).…”

The influence of bedrock hydrogeology on catchment-scale nitrate fate and transport in fractured aquifers

“…Previous groundwater studies have attributed an enrichment of δ 15 N to δ 18 O by a factor of between 8 1.3 and 2.1 to denitrification ; Aravena & Robertson 1998;Fukada et al 2003). 9 Fractionation processes influencing ammonia prior to its ammonification to ammonium and 10 subsequent nitrification to nitrate can have an impact on the nitrate isotopic signature.…”