Two Centuries of Coral Skeletons from the Northern South China Sea Record Mercury Emissions from Modern Chinese Wars

Abstract

The contemporary mercury (Hg) cycle in the world's oceans has been greatly affected by human activities. However, we are still lacking reliable, long-term, and continuous records of Hg in seawater. Here, we report for the first time on using annually banded Porites coral skeletons from the northern South China Sea (SCS) as an archive for recording changes of seawater dissolved Hg spanning the past two centuries. We developed a combustion-trapping method to preconcentrate ultratrace Hg concentrations from coral aragonitic skeletons for highly accurate total Hg measurements. Results show that Hg in the coral skeletons ranges from 0.3 to 5.1 pmol/g and is discriminated against Ca during coral skeletal calcification. Preindustrial (1798-1832) Hg levels in coral skeletons were found to be approximately 0.5 pmol/g. The highest Hg concentrations (3-5 pmol/g) were observed during the WWII period (1933-1942). Other distinct Hg maxima (∼3 pmol/g) are observed for the periods 1833-1847, 1858-1862, 1918-1927, 1978-1982, and 1988-1992, with the first four coinciding with contemporary Chinese wars. Our study suggests that the production and use of ammunitions in those wars likely account for the primary Hg emission sources in the northern SCS before 1950, and coral is potentially a robust indicator of historical, regional Hg contamination events.

Spread, Behavior, and Ecosystem Consequences of Conventional Munitions Compounds in Coastal Marine Waters

“…Elevated levels of Hg in fish near munitions dumpsites have been attributed to mercury fulminate (Della Torre et al, 2010), although a definitive link was not shown. Mercury records in corals from the South China Sea show peaks in concentration that appear to coincide with regional wars (Sun et al, 2016). However, it is unclear if a munition Hg source is substantial enough to sufficiently elevate concentrations in seawater (C. Lamborg, as cited by Monahan, 2016).…”

700 years reconstruction of mercury and lead atmospheric deposition in the Pyrenees (NE Spain)

“…Several sites in remote regions from South and North America have also shown high Hg accumulation rates around CE 1940 (Beal et al, 2015;Biester et al, 2002;Schuster et al, 2002). Coral skeletons from the South China Sea and North Atlantic myctophids, have also revealed the highest Hg concentrations in the marine realm during the WWII (Martins et al, 2006;Sun et al, 2016). This global increase in Hg deposition highlights the long-range atmospheric transport of gaseous Hg, from anthropogenic emission sources to remote areas where atmospheric Hg can be oxidized to divalent Hg (Hg II ), and deposited onto terrestrial and marine ecosystems (Wang et al, 2014).…”

Mercury Inputs Into Eastern China Seas Revealed by Mercury Isotope Variations in Sediment Cores

“…As reported by R. Sun et al. (2016), coral skeletons from the northern South China Sea have recorded significant Hg emissions from modern Chinese wars during the period of 1800–2000. Unraveling the input pathway, transformation, and fate of these historically anthropogenic Hg in the coastal environment is thus a challenging but imperative task.…”