Drivers of Surface Ocean Mercury Concentrations and Air–Sea Exchange in the West Atlantic Ocean

• Published in: Environmental science & technology Vol. 47; no. 14; pp. 7757 - 7765
• Main Authors: Soerensen, Anne L, Mason, Robert P, Balcom, Prentiss H, Sunderland, Elsie M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 16.07.2013
• Subjects: Applied sciences; Atlantic Ocean; Atmospheric pollution; Biogeochemistry; Carbon; Exact sciences and technology; Measurement; Mercury; Mercury - analysis; Natural water pollution; Oceans; Pollutants physicochemistry study: properties, effects, reactions, transport and distribution; Pollution; Seawater; Seawaters, estuaries; Water Pollutants, Chemical - analysis; Water treatment and pollution; West Atlantic; Atlantic Ocean; AW, West Atlantic; Environmental factor; Zerovalent metal; Neurotoxic; Heavy metal; Trace element; Air sea interface; Flux density; Air pollution; Poison; Water pollution; Gas exchange; Mercury; Material balance; Concentration distribution; Seawater
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es401354q

Accurately characterizing net evasion of elemental mercury (Hg0) from marine systems is essential for understanding the global biogeochemical mercury (Hg) cycle and the pool of divalent Hg (HgII) available for methylation. Few high resolution measurements of Hg0 are presently available for constraining global and regional flux estimates and for understanding drivers of spatial and temporal variability in evasion. We simultaneously measured high-resolution atmospheric and surface seawater Hg0 concentrations as well as the total Hg distribution during six cruises in the West Atlantic Ocean between 2008 and 2010 and examined environmental factors affecting net Hg0 formation and evasion. We observed the lowest fraction of Hg as Hg0 (7.8 ± 2.4%) in the near-coastal and shelf areas that are influenced by riverine inputs. Significantly higher %Hg0 observed in open ocean areas (15.8 ± 3.9%) may reflect lower dissolved organic carbon (DOC) in offshore environments, which is known to affect both the reducible HgII pool and redox kinetics. Calculated Hg0 evasion changed by more than a factor of 3 between cruises (range: 2.1 ± 0.7 to 6.8 ± 5.1 ng m–2 h–1), driven mainly by variability in Hg0 and wind speed. Our results suggest that further mechanistic understanding of the role of DOC on Hg redox kinetics in different types of marine environments is needed to explain variability in Hg0 concentrations and improve global estimates of air–sea exchange.