Nitrogen isotope hydrochemistry and denitrification within the Chalk aquifer system of north Norfolk, UK

Multi-isotope approach for the identification and characterisation of nitrate pollution sources in the Marano lagoon (Italy) and parts of its catchment area

“…The possibility of quantifying both the origin and the secondary processes affecting N concentrations by means of a single tracer appears more limited however. Nitrogen cannot be considered conservative because it is biologically modified through nitrification and denitrification reactions, both during infiltration of the water and in the groundwater body, causing isotopic fractionation that modifies the б 15 N signatures of the dissolved N species (VOGEL et al, 1981;MARIOTTI et al, 1988;Böttcher et al, 1990;Smith et al, 1991;FEATS et al, 1998;ARAVENA AND ROBERTSON, 1998;PAUWELS et al, 2000, TORRENTÓ et al, 2010ZHANG et al, 2010). In some cases, the interference between the isotopic fractionation (linked to denitrification) and the mixing processes (from the combination of multiple nitrate sources) might hamper the identification of nitrate sources, since the associated fractionation processes can alter the isotope composition of dissolved nitrate.…”

Groundwater nitrate pollution in the recharge zone of a regional Quaternary flow system (Wielkopolska region, Poland)

“…In general, this process is effective under anaerobic conditions, in which electron donors, such as dissolved organic carbon, sedimentary organic matter or the reduced form of sulphur, are available. In some aquifer systems, denitrification within the aquitard has been documented (Robertson et al 1995;Feast et al 1998;Rodvang and Simpkins 2001). This denitrification is manifested by the absence of nitrate, even in regions that are strongly influenced by agricultural activities, where a high content of nitrate occurs in shallow flow systems.…”

Macronutrient status of UK groundwater: Nitrogen, phosphorus and organic carbon

“…Foster et al (1985) found denitrifying bacteria in till and the 1960s tritium peak preserved but absence of nitrate. Feast et al (1998) found isotopic evidence of denitrification in the overlying Till deposits on the Chalk.…”

“…These processes are not easily distinguishable based on nitrate concentrations and lithology alone, a range of hydrochemical and isotope techniques have been used effectively to constrain denitrification processes (e.g. Feast et al, 1998;Gooddy and Darling, 2009;Lapworth et al, 2008b). Alternative urban sources may, however, still be significant and explain some elevated occurrences; for example, the Birmingham aquifer in the West Midlands, underlying the UK's second city, is classified in the maximum concentration band.…”