Trends in Atmospheric Deposition of Mercury
In Chap. 2 of this volume Lange and Frederick evaluate changes in mercury (Hg) concentrations in Everglades biota to identify the occurrence of temporally coherent trends that ideally can be understood and related to changing process dynamics. To the ext
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Trends in Atmospheric Deposition of Mercury Curtis D. Pollman and Daniel R. Engstrom
Abstract In Chap. 2 of this volume Lange and Frederick evaluate changes in mercury (Hg) concentrations in Everglades biota to identify the occurrence of temporally coherent trends that ideally can be understood and related to changing process dynamics. To the extent such trends occur in the Everglades, processes that are potentially causative include atmospheric deposition of Hg, changing dynamics in key water quality variables such as sulfate and dissolved organic carbon, and changing hydrology. This overall process of trend identification and elucidation of underlying factors can in turn provide insight on possible strategies for mitigating the problem of excessive biota Hg concentrations in the Everglades. This chapter evaluates whether changes in atmospheric deposition of Hg to the Everglades have occurred in recent years using direct evidence from measured wet deposition and gaseous elemental mercury (GEM). The chapter also considers changes in mercury concentrations recorded in bottom sediments as a proxy for longer-term changes in atmospheric deposition. This latter analysis includes a review of changes observed in aquatic ecosystems from North America and Europe as well as south Florida and the Everglades, and whether recent changes in south Florida reflect large scale processes or reductions in local emissions of Hg. Keywords Mercury · Wet deposition · Total gaseous mercury · Sediment · Sediment accumulation rates · Lake Annie · R-EMAP
C. D. Pollman (*) Aqua Lux Lucis, Inc., Gainesville, FL, USA e-mail: [email protected] D. R. Engstrom St. Croix Watershed Research Station, Science Museum of Minnesota, Marine on St. Croix, MN, USA e-mail: [email protected] © Springer Nature Switzerland AG 2020 C. D. Pollman et al. (eds.), Mercury and the Everglades. A Synthesis and Model for Complex Ecosystem Restoration, https://doi.org/10.1007/978-3-030-55635-8_1
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C. D. Pollman and D. R. Engstrom
Introduction
Like many otherwise pristine and oligotrophic ecosystems, the Florida Everglades are characterized by high concentrations of mercury (Hg) in fish (Chap. 9, Volume II) and other biota (Chap. 10, Volume II). This problem was first identified in 1989 when a monitoring project by state agencies found Hg in largemouth bass (LMB) from the Florida Everglades to average in excess of 2 mg/kg—well above the Florida Department of Health advisory limits for limited consumption of 0.5 mg/kg. Subsequent to these initial findings, elevated concentrations were found in other Everglades biota, including the endangered Florida panther (Roelke and Glass 1992) and several different species of wading birds (Frederick et al. 1999). Two types of temporal trend dynamics can be demonstrated for tissue concentrations of Hg in Everglades biota. The first are long-term increases (decadal or greater) of 4 to 6 based on comparing recent concentrations of Hg measured in the scapular feathers of Everglades white ibises (Eudocimus albus), great egrets (A
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