Effect of Abiotic and Biotic Factors on the Photo-Induced Production of Dissolved Gaseous Mercury Sehee Oh & Moon-Kyung Kim & Young-Min Lee & Kyung-Duk Zoh Received: 29 September 2010 / Accepted: 21 January 2011 / Published online: 20 February 2011 # Springer Science+Business Media B.V. 2011 Abstract This study was conducted to evaluate the contribution of environmental factors such as solar radiation and dissolved organic matter (DOM) on the photo-induced dissolved gaseous mercury (DGM) production through laboratory experiments using field water samples collected from wetlands. DGM pro- duction was more significantly influenced by UVB intensity than UVA. DGM formation was also significantly affected by DOM chemical structure/ composition rather than its concentration. Increasing NO 3 - concentration limited DGM production, but photo-induced Hg oxidation stimulated by NO 3 - would possibly occur when the NO 3 - level is more than twice the DOC level. The addition of phosphorus into the field water samples induced a slight increase of DGM production; however, the addition of nitrogen decreased DGM formation, suggesting that an increase of limiting nutrients in water may promote biotic DGM production. Experiments using a Sele- nastrum capricornutum monoculture solution showed that cell density had a positive effect on DGM production. Moreover, the difference in DGM produc- tion between filtered and unfiltered samples showed that S. capricornutum significantly produced biotic DGM under UVA irradiation. Finally, our results imply that environmental factors such as light intensity, DOM sources, and site-specific microorganisms can signifi- cantly affect photo-induced Hg transformation. Keywords Dissolved gaseous mercury (DGM) . Dissolved organic matter (DOM) . UVA . UVB . Nitrate . Algae . Climate change 1 Introduction Dissolved gaseous mercury (DGM), mainly as Hg(0), is a major volatile species of mercury (Hg) in natural water columns. It can escape to the atmosphere, leading to reduction of the Hg burden on water systems and finally to its bioaccumulation in the aquatic food chain (Fitzgerald et al. 1991; Vandal et al. 1991). Also, production and volatilization of DGM in aquatic environment greatly influence the global mercury cycle (Mason et al. 1994; Zhang and Lindberg 2000). Therefore, understanding of the main processes controlling DGM production and evaluation of the importance of those processes are needed. DGM production in natural water is predominated by solar radiation. Many studies have demonstrated that the diurnal and seasonal patterns of DGM concentration in freshwaters are significantly related to solar radiation (Amyot et al. 1997a, b; Zhang and Lindberg 2000, 2001). According to those studies, DGM concentrations were highest around noon and in the summer under maximum insolation. Water Air Soil Pollut (2011) 220:353–363 DOI 10.1007/s11270-011-0759-z S. Oh : M.-K. Kim : Y.-M. Lee : K.-D. Zoh (*) Department of Environmental Health, School of Public Health, Seoul National University, Seoul 151-745, South Korea e-mail: zohkd@snu.ac.kr