Sources of dissolved inorganic nitrogen in a coastal lagoon adjacent to a major metropolitan area, Miami Florida (USA)

• Published in: Applied geochemistry Vol. 38; pp. 134 - 146
• Main Authors: Swart, Peter K., Anderson, William T., Altabet, Mark A., Drayer, Courtney, Bellmund, Sarah
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.11.2013; Elsevier
• Subjects: Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Geochemistry; Marine; Pollution, environment geology; Florida; United States; Floridan Aquifer; Dade County Florida; Biscayne Bay; ASW, USA, Florida; ASW, USA, Florida, Miami; ASW, USA, Florida, Biscayne Bay; interfaces; waste water; nitrogen; Plantae; algae; nitrates; North America; denitrification; assimilation; lagoons; water treatment; landfills; carbon; organic materials; Thallophyta
• ISSN: 0883-2927; 1872-9134
• DOI: 10.1016/j.apgeochem.2013.09.008

•A range of biota (algae and sea grasses) shows enriched δ15N close to the coast.•Enriched signals are evident in the particulate and sedimentary organic material.•δ15N signals are correlated with high inputs of dissolved inorganic matter.•The enriched values support the presence of a sewage related component.•The δ15N could arise from the local landfill, injected wastewater, or septic systems. Between 2006 and 2007, a study was carried out to determine the relative importance of natural and anthropogenic input of nitrogen into Biscayne Bay (South Florida, USA) using δ13C and δ15N values of algae, seagrasses, and particulate organic material, δ18O and δ15N of the NO3- and δ13C of the dissolved inorganic carbon. The δ15N values of all components showed a strong east to west gradient approaching more positive values (+7 to +10‰) close to the land-sea interface. The nitrogen could have emanated from the local waste water treatment plant, septic systems within the region, or nitrogen which had been affected by denitrification and leached from the local landfill, wastewater which had been injected into the Floridan aquifer and leaked back to the surface, and/or some other as yet unidentified source. The measured NO3- δ15N and δ18O values indicated that the dissolved nitrate originated from anthropogenic sources and was fractionated during assimilation.