The photochemical release of inorganic nitrogen from dissolved organic matter is an important source of bio-available nitrogen (N) in N-limited aquatic ecosystems. We conducted photochemical experiments and used mathematical models based on pseudo-first-order reaction kinetics to quantify the photochemical transformations of individual N species and their seasonal effects on N cycling in a mountain forest stream and lake (Plešné Lake, Czech Republic). Results from laboratory experiments on photochemical changes in N speciation were compared to measured lake N budgets. Concentrations of organic nitrogen (Norg; 40-58 µmol L-1) decreased from 3 to 26% during 48-hour laboratory irradiation (an equivalent of 4-5 days of natural solar insolation) due to photochemical mineralization to ammonium (NH4+) and other N forms (Nx; possibly N oxides and N2). In addition to Norg mineralization, Nx also originated from photochemical nitrate (NO3-) reduction. Laboratory exposure of a first-order forest stream water samples showed a high amount of seasonality, with the maximum rates of Norg mineralization and NH4+ production in winter and spring, and the maximum NO3- reduction occurring in summer. These photochemical changes could have an ecologically significant effect on NH4+ concentrations in streams (doubling their terrestrial fluxes from soils) and on concentrations of dissolved Norg in the lake. In contrast, photochemical reactions reduced NO3- fluxes by a negligible (<1%) amount and had a negligible effect on the aquatic cycle of this N form.

Biology Centre of the Academy of Sciences of the Czech Republic Institute of Hydrobiology České Budějovice Czech Republic

Faculty of Science University of South Bohemia in České Budějovice České Budějovice Czech Republic

Zobrazit více v PubMed

Porcal P, Amirbahman A, Kopáček J, Novák F, Norton SA (2009) Photochemical release of humic and fulvic acid-bound metals from simulated soil and streamwater. J Environ Monitor 11:1064–1071. PubMed

Vähätalo AV, Salonen K, Münster U, Järvinen M, Wetzel RG (2003) Photochemical transformation of allochthonous organic matter provides bioavailable nutrients in a humic lake. Arch Hydrobiol 156:287–314.

Vähätalo A, Järvinen M (2007) Photochemically produced bioavailable nitrogen from biologically recalcitrant dissolved organic matter stimulates production of a nitrogen-limited microbial food web in the Baltic Sea. Limnol Oceanogr 52:132–143.

Brezonik PL, Fulkerson-Brekken J (1998) Nitrate-induced photolysis in natural waters: controls on concentrations of hydroxyl radical photo-intermediates by natural scavenging agents. Environ Sci Tech 32:3004–3010.

Stevenson FJ (1982) Nitrogen in agricultural soils. Madison, WI: Soil Science Society of America.

Bushaw KL, Zepp RG, Tarr MA, Schulz-Jander D, Bourbonniere RA, et al. (1996) Photochemical release of biologically available nitrogen from aquatic dissolved organic matter. Nature 381:404–407.

Kieber RJ, Li A, Seaton PJ (1999) Production of Nitrite from the Photodegradation of Dissolved Organic Matter in Natural Waters. Environ Sci Tech 33:993–998.

Wang W, Tarr MA, Bianchi TS, Engelhaupt E (2000) Ammonium Photoproduction from Aquatic Humic and Colloidal Matter. Aquat Geochem 6:275–292. PubMed

Stedmon CA, Markager S, Tranvik L, Kronberg L, Slätis T, et al. (2007) Photochemical production of ammonium and transformation of dissolved organic matter in the Baltic Sea. Mar Chem 104:227–240.

Fanning JC (2000) The chemical reduction of nitrate in aqueous solution. Acs Sym Ser 199:159–179.

Takeda T, Takedoi H, Yamaji S, Ohta K, Sakugawa H (2004) Determination of Hydroxyl Radical Photoproduction Rates in Natural Waters. Anal Sci 20:153–158. PubMed

Kieber DJ, Peake BM, Scully MN (2003) Reactive oxygen species in aquatic systems, p. 251–288. In Hebling EW and Zagrese H, editors. UV effects in aquatic organisms and ecosystems. Royal Society of Chemistry, Cambridge.

Vione D, Falletti G, Maurino V, Minero C, Pelizzetti E, et al. (2006) Sources and Sinks of Hydroxyl Radicals upon Irradiation of Natural Water Samples. Environ Sci Tech 40:3775–3781. PubMed

Voelker BM, Sulzberger B (1996) Effects of fulvic acid on Fe(II) oxidation by hydrogen peroxide. Environ Sci Tech 30:1106–1114.

Aarnos H, Ylöstalo P, Vähätalo AV (2012) Seasonal phototransformation of dissolved organic matter to ammonium, dissolved inorganic carbon, and labile substrates supporting bacterial biomass across the Baltic Sea. J Geophys Res 117:2156–2202.

Wiegner TN, Seitzinger SP (2001) Photochemical and microbial degradation of external dissolved organic matter inputs to rivers. Aquat Microb Ecol 24:27–40.

Koopmans DJ, Bronk DA (2002) Photochemical production of dissolved inorganic nitrogen and primary amines from dissolved organic nitrogen in waters of two estuaries and adjacent surficial groundwaters. Aquat Microb Ecol 26:295–304.

Gao H, Zepp RG (1998) Factors Influencing Photoreactions of Dissolved Organic Matter in a Coastal River of the Southeastern United States. Environ Sci Tech 32:2940–2946.

Kitidis V, Stubbins AP, Uher G, Upstill GRC, Law CS, et al. (2008) Variability of chromophoric organic matter in surface waters from the Atlantic Ocean. Deep-Sea Res Pt II 53:1666–1684.

Porcal P, Dillon PJ, Molot LA (2013a) Seasonal changes in photochemical properties of dissolved organic matter in small boreal streams. Biogeosciences 10:5533–5543.

Kopáček J, Brzáková M, Hejzlar J, Nedoma J, Porcal P, et al. (2004) Nutrient cycling in a strongly acidified mesotrophic lake. Limnol Oceanogr 49:1202–1213.

Kopáček J, Turek J, Hejzlar J, Kaňa J, Porcal P (2006) Element fluxes in watershed-lake ecosystems recovering from acidification: Plešné Lake, the Bohemian Forest, 2001–2005. Biologia, Bratislava 61 (Suppl. 20):S427–S440.

Majer V, Cosby BJ, Kopáček J, Veselý J (2003) Modelling Reversibility of Central European Mountain Lakes from Acidification: Part I - The Bohemian Forest. Hydrol Earth Sys Sc 7:494–509.

Vrba J, Kopáček J, Fott J, Kohout L, Nedbalová L, et al. (2003) Long-term studies (1871–2000) on acidification and recovery of lakes in the Bohemian Forest (Central Europe). Sci Total Environ 310:73–85. PubMed

Kopáček J, Procházková L (1993) Semi-micro determination of ammonia in water by the rubazoic acid method. Int J Environ An Ch 53:243–248.

Van der Perk M (2006) Soil and water contamination from molecular to catchment scale. Taylor & Francis, London

Bevington PR, Robinson DK (2003) Data reduction and error analysis for the physical sciences. 3rd ed., McGraw-Hill, New York

CNI (2014) Hydrological data on surface water. ČSN 751400, Czech Standards Institute, Prague (In Czech)

Porcal P, Dillon PJ, Molot LA (2013b) Photochemical production and decomposition of particulate organic carbon in a freshwater stream. Aquat Sci 75:469–482.

Helms JR, Stubbins A, Ritchie JD, Minor EC, Kieber DJ, et al. (2008) Absorption spectral slopes and slope ratios as indicators of molecular weight, source, and photobleaching of chromophoric dissolved organic matter. Limnol Oceanogr 53:955–969.

Stone AT, Morgan JJ (1990) Kinetics of Chemical Transformation in the Environment, p. 1–42. In: Stumm WAeditor. Aquatic chemical kinetics: reaction rates of processes in natural waters. Wiley-Interscience publication. John Wiley & Sons, Inc. New York.

Bushaw-Newton KL, Moran MA (1999) Photochemical formation of biologically available nitrogen from dissolved humic substances in coastal marine systems. Aquat Microb Ecol 18:285–92.

Gardner WS, Cavaletto JF, Bootsma HA, Lavrentyev PJ, Troncone F (1998) Nitrogen cycling rates and light effects in tropical Lake Maracaibo, Venezuela. Limnol Oceanogr 43:1814–1825.

Anastasio C, McGregor KG (2000) Photodestruction of Dissolved Organic Nitrogen Species in Fog Waters. Aerosol Sci. Tech. 32:106–119.

Spokes LJ, Liss PS (1996) Photochemically induced redox reactions in seawater, II. Nitrogen and iodine. Mar Chem 54:1–10.

Jones DL, Shannon D, Murphy D, Farrar JF (2004) Role of dissolved organic nitrogen (DON) in soil N cycling in grassland soils. Soil Biol Biochem 36:749–756.

Lipson DA, Schmidt SK, Monson RK (2000) Carbon availability and temperature control the post-snowmelt baseline in alpine soil microbial biomass. Soil Biol Biochem 32:441–448.

Brooks PD, Williams MW, Schmidt SK (1998) Inorganic nitrogen and microbial biomass dynamics before and during spring snowmelt. Biogeochemistry 43:1–15.

Edwards KA, McCulloch J, Kershaw GP, Jeffries RL (2006) Soil microbial and nutrient dynamics in a wet Arctic sedge meadow in late winter and early spring. Soil Biol Biochem 38:2843–2851.

Bertilsson S, Stepanauskas R, Rocio-Hansson R, Granéli W, Wikner J, et al. (1999) Photochemically induced changes in bioavailable carbon and nitrogen pools in a boreal watershed. Aquat Microbial Ecol 19:47–56.

Tranvik L, Bertilsson S (2001) Contrasting effects of solar UV radiation on dissolved organic sources for bacterial growth. Ecol Lett 4:458–463.