title: Changes in the long-term supply of mercury species to the upper mixed waters of a recovering lake.
abstract: We quantified internal processes that supply methylmercury from hypolimnetic reducing zones to the upper waters of a Hg-contaminated lake, Onondaga Lake, NY, USA. Diffusive transport continuously supplied methylmercury to the epilimnion under summer stratification, while fall mixing resulted in a pulsed release of methylmercury to the upper mixed waters. These processes were the main internal sources of methylmercury to the epilimnion, and together almost equaled the total external supply. The wind-driven entrainment represented an additional stochastic internal supply of methylmercury of approximately 9% in 2006. Considering more than 15 years of data, we estimate 1.8 wind-driven events occur per year. The mass of methylmercury inputs to the epilimnion exceeded the measured increase, suggesting that loss processes are important in regulating methylmercury accumulation. The relative contribution of internal sources of methylmercury to the epilimnion has decreased in recent years, shifting the importance to the external inputs.
authors: Department of Civil and Environmental Engineering, Syracuse University, Syracuse, NY 13244, USA. Electronic address: stodorov@syr.edu.
authors: Svetoslava G
authors: SG
authors: Todorova
authors: Department of Civil and Environmental Engineering, Syracuse University, Syracuse, NY 13244, USA. Electronic address: ctdrisco@syr.edu.
authors: Charles T
authors: CT
authors: Driscoll
authors: Upstate Freshwater Institute, P.O. Box 506, Syracuse, NY 13214, USA. Electronic address: sweffler@upstatefreshwater.org.
authors: Steven W
authors: SW
authors: Effler
authors: Upstate Freshwater Institute, P.O. Box 506, Syracuse, NY 13214, USA. Electronic address: susanod@upstatefreshwater.org.
authors: Susan
authors: S
authors: O'Donnell
authors: Upstate Freshwater Institute, P.O. Box 506, Syracuse, NY 13214, USA. Electronic address: damatthews@upstatefreshwater.org.
authors: David A
authors: DA
authors: Matthews
authors: Utica College, 1600 Burrstone Road, Utica, NY 13502, USA. Electronic address: ditodorov@utica.edu.
authors: Dimitar L
authors: DL
authors: Todorov
authors: Department of Civil and Environmental Engineering, Syracuse University, Syracuse, NY 13244, USA. Electronic address: stephanieg@stetsonengineers.com.
authors: Stephanie
authors: S
authors: Gindlesperger
mesh_terms: D004784:Environmental Monitoring; D060106:Lakes / Q000737:chemistry*; D008628:Mercury / Q000032:analysis*; D008767:Methylmercury Compounds / Q000032:analysis; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data
chemical_list: D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D008628:Mercury
keywords: Diffusive mixing; Entrainment; Methyl mercury; Onondaga Lake; Turnover