Short communication Do lagoons near concentrated animal feeding operations promote nitrous oxide supersaturation? Konstantinos C. Makris a, * , Dibyendu Sarkar b , Syam S. Andra c , Stephan B.H. Bach d , Rupali Datta e a Cyprus International Institute for the Environment and Public Health in association with the Harvard School of Public Health, 5 Iroon Street,1105 Nicosia, Cyprus b Department of Earth and Environmental Studies, Montclair State University, Montclair, NJ, USA c Environmental Geochemistry Laboratory, University of Texas at San Antonio, San Antonio, TX, USA d Department of Chemistry, University of Texas at San Antonio, San Antonio, TX, USA e Department of Biology, Michigan Technological University, Houghton, MI, USA Supersaturation of nitrous oxide may occur in lagoons near concentrated animal feeding operations. article info Article history: Received 10 November 2008 Received in revised form 16 January 2009 Accepted 23 January 2009 Keywords: Supersaturation Nitrous oxide Climate change Global warming Animal waste Lagoons Wastewater abstract Animal wastewater lagoons nearby concentrated animal feeding operations (CAFOs) represent the latest tendency in global animal farming, severely impacting the magnitude of greenhouse gas emissions, including nitrous oxide (N 2 O). We hypothesized that lagoon wastewater could be supersaturated with N 2 O as part of incomplete microbial nitrification/denitrification processes, thereby regulating the N 2 O partitioning in the gaseous phase. The objectives of this study were: (i) to investigate the magnitude of dissolved N 2 O concentrations in the lagoon; and (ii) to determine the extent to which supersaturation of N 2 O occurs in wastewater lagoons. Dissolved N 2 O concentrations in the wastewater samples were high, ranging from 0.4 to 40.5 mgN 2 O mL 1 . Calculated dissolved N 2 O concentrations from the experimentally measured partition coefficients were much greater than those typically expected in aquatic systems (<w0.6 mgN 2 O mL 1 ). Knowledge of the factors controlling the magnitude of N 2 O supersaturation could potentially bridge mass balance differences between in situ measurements and global N 2 O models. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Owing to the at least an order of magnitude lower atmospheric concentration of nitrous oxide (N 2 O) compared to those of carbon dioxide (CO 2 ), one might overlook the importance of N 2 O as a major greenhouse gas. However, due to its 300 times larger global warming potential than an equal mass of CO 2 ,N 2 O is increasingly becoming a subject of global warming research and public policy debates (IPCC, 1997). Gradual increases in atmospheric N 2 O concentrations have been linked to the observed climate change and partially contribute to the global warming effect. Agricultural activities represent a major source of elevated N 2 O concentrations in the atmosphere, since global anthropogenic N 2 O emissions from agriculture totaled w6Tg N 2 O–N in 1994 (w75% total anthropo- genic emissions) (IPCC, 1997). Reduction in N 2 O emissions is deemed necessary but may seem distant unless we fully comprehend the N 2 O sinks and sources related to agricultural activities. Direct emissions from either nitrogen fertilized or manure-amended agricultural soils or animal waste management systems represent major pools of N 2 O (Kroeze et al., 1999). The conventional notion that N 2 O losses are solely attributed to gaseous movement from the source to the atmosphere has been challenged by data supporting N 2 O losses via surface runoff and water drainage from agricultural soils (Dowdell et al., 1979). Certain environmental conditions could minimize N 2 O fugacity, and enhance its solubility in water, making it susceptible to N 2 O losses via runoff towards down- stream water bodies. Concentrated animal feeding operations (CAFOs) represent the latest tendency in global animal farming, severely impacting the magnitude of greenhouse gas emissions, including N 2 O, since more and more CAFOs worldwide switch to liquid animal waste management systems (Koneswaran and Nierenberg, 2008). Live- stock and manure piles are the main sources of N 2 O emissions in CAFOs, but lagoons storing animal wastewater have been largely overlooked with respect to N 2 O emissions. Earlier work in our group identified an organoarsenical (roxarsone) metabolite com- plexed to N 2 O in an animal waste aqueous suspension, using electrospray ionization mass spectrometry (Makris et al., 2008a). We decided to investigate this further by looking into animal * Corresponding author. Tel.: þ357 2 244 9292; fax: þ357 2 244 9293. E-mail address: kcmakris@gmail.com (K.C. Makris). Contents lists available at ScienceDirect Environmental Pollution journal homepage: www.elsevier.com/locate/envpol 0269-7491/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.envpol.2009.01.019 Environmental Pollution 157 (2009) 1957–1960