Media release

From: AAAS

Global transport of mercury in rivers has risen 2- to 3-fold since the 1850s

Human activity since the Industrial Revolution has caused a 2- to 3-fold increase in the global river transport of mercury, a new study suggests. Higher mercury concentrations in rivers (riverine Hg) across the world pose a health risk. Yet, the degree by which coal combustion, mining, manufacturing, and other industrial practices have altered this natural cycle since the 1850s was unquantified until now. Here, Dong Pengand colleagues have done so.

First, they calculated global riverine Hg levels in the pre-industrial era, creating a river-specific Hg-cycle model derived from the Community Earth System Model (CESM2). From 1845-1859, the average baseline river cycle was roughly 390 megagrams of Hg per year (Mg/year) globally. It fluctuated regionally between 321-483 Mg/year. Peng et al. also corroborated this finding with global historic sediment cores. Next, they compared the pre-industrial riverine Hg budget to today’s budget of roughly 1,000 Mg/year, as established by recent analyses.

Allowing for variability, they found a change equating to a 595 Mg/year increase in the last 2 centuries. “The 1850 Hg budgets and concentrations can still serve as a reference baseline, providing a historical benchmark to gauge the impacts of both natural and anthropogenic factors, and the progress and effectiveness in Hg pollution reduction initiatives,” the authors write, suggesting the baseline could be a target for policymakers.