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Updated Global and Oceanic Mercury Budgets for the United Nations Global Mercury Assessment 2018
journal contribution
posted on 2018-09-18, 00:00 authored by P. M. Outridge, R. P. Mason, F. Wang, S. Guerrero, L. E. Heimbürger-BoavidaIn
support of international efforts to reduce mercury (Hg) exposure
in humans and wildlife, this paper reviews the literature concerning
global Hg emissions, cycling and fate, and presents revised global
and oceanic Hg budgets for the 2018 United Nations Global Mercury
Assessment. We assessed two competing scenarios about the impacts
of 16th – late 19th century New World silver (Ag) mining, which may
be the largest human source of atmospheric Hg in history. Consideration
of Ag ore geochemistry, historical documents on Hg use, and
comparison of the scenarios against atmospheric Hg patterns in environmental
archives, strongly support a “low mining emission” scenario.
Building upon this scenario and other published work, the revised
global budget estimates human activities including recycled legacy
emissions have increased current atmospheric Hg concentrations by
about 450% above natural levels (prevailing before 1450 AD). Current
anthropogenic emissions to air are 2.5 ± 0.5 kt/y. The increase
in atmospheric Hg concentrations has driven a ∼ 300% average
increase in deposition, and a 230% increase in surface marine waters.
Deeper marine waters show increases of only 12–25%. The overall
increase in Hg in surface organic soils (∼15%) is small due
to the large mass of natural Hg already present from rock weathering,
but this figure varies regionally. Specific research recommendations
are made to reduce uncertainties, particularly through improved understanding
of fundamental processes of the Hg cycle, and continued improvements
in emissions inventories from large natural and anthropogenic sources.
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oceanic Hg budgetsSpecific research recommendationssurface marine watersUnited Nations Global Mercury Assessment 2018Current anthropogenic emissionscentury New World silverOceanic Mercury Budgetsmarine waters show increasesscenario2018 United Nations Global Mercury AssessmentHg concentrationsAg ore geochemistryAD
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