title: Anthropogenic loads and biogeochemical role of urea in the Gulf of Trieste.
abstract: In order to assess the role of urea in the Gulf of Trieste, oceanographic data collected from 2002 to 2011 were analyzed together with ancillary ambient information and compared to past studies. The recent levels of urea found in these coastal waters (median = 1.1 μM N, maximum value = 19.7 μM N) are often high and similar to those reported in the early 1980s. A preliminary estimate of the external inputs indicated that this enrichment in urea is mainly due to emissions from urban sewage systems, whereas the contributions of rivers and atmospheric deposition are scarce. As a consequence, urea appears to be a reliable tracer of the diffusion of wastewaters in the coastal marine environment, more specific and sensitive than other nutrients, with a behavior that also reflects the technology of the treatment plants. The stability of urea levels over the last three decades suggests that the upgrade of wastewater treatment technologies was probably balanced by the concomitant increase of the anthropogenic pressure in the area (477,000 to 1,300,000 inhabitant equivalent). Budget estimates on the gulf-wide scale indicate that urea (177-530 t N) is not negligible compared to dissolved inorganic nitrogen (409-919 t N) and that it can constitute up to 56% of the nitrogen available for plankton growth. A large accumulation of urea can occur during summer periods characterized by stable weather conditions and weak circulation, whereas a biologically mediated degradation to ammonium is observed in autumn in concomitance to a strong shift of the marine ecosystem toward heterotrophic conditions. These processes, together with a potential competition between phytoplankton and bacteria for the utilization of this nitrogen form, suggest that the biogeochemical role of urea should be better investigated in mid-latitude coastal zones subjected to highly variable ambient conditions and to overloads of this compound.
authors.affiliation: CNR-ISMAR, Istituto di Scienze Marine, Trieste, Viale Romolo Gessi 2, 34123 Trieste, Italy. Electronic address: stefano.cozzi@ts.ismar.cnr.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Cozzi
authors.affiliation: ARPA-FVG, Laboratorio Unico Regionale, Sede di Trieste, Via Alessandro Lamarmora 13, 34139 Trieste, Italy. Electronic address: andrea.mistaro@arpa.fvg.it.
authors.forename: Andrea
authors.initials: A
authors.lastname: Mistaro
authors.affiliation: CNR-ISMAR, Istituto di Scienze Marine, Trieste, Viale Romolo Gessi 2, 34123 Trieste, Italy. Electronic address: stefania.sparnocchia@ts.ismar.cnr.it.
authors.forename: Stefania
authors.initials: S
authors.lastname: Sparnocchia
authors.affiliation: ARPA-FVG, Laboratorio Unico Regionale, Sede di Trieste, Via Alessandro Lamarmora 13, 34139 Trieste, Italy. Electronic address: luigi.colugnati@arpa.fvg.it.
authors.forename: Luigi
authors.initials: L
authors.lastname: Colugnati
authors.affiliation: NIB-MBS, National Institute of Biology, Marine Biology Station, Fornace 41, 6330 Piran, Slovenia. Electronic address: Oliver.Bajt@mbss.org.
authors.forename: Oliver
authors.initials: O
authors.lastname: Bajt
authors.affiliation: ARPA-FVG, Laboratorio Unico Regionale, Sede di Trieste, Via Alessandro Lamarmora 13, 34139 Trieste, Italy. Electronic address: loredana.toniatti@arpa.fvg.it.
authors.forename: Loredana
authors.initials: L
authors.lastname: Toniatti
mesh_terms: D004784:Environmental Monitoring; D007558:Italy; D045483:Rivers / Q000737:chemistry; D012623:Seawater / Q000737:chemistry; D014508:Urea / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D014508:Urea
keywords: Coastal zone monitoring; Northern Adriatic; Nutrients; Sewage; Urban impact; Urea