This
study examined the isotopic composition of particulate bound
mercury (PBM) in 10 Chinese megacities and explored the associated
sources and transformation mechanisms. PBM in these cities was characterized
by negative δ202Hg (mean: −2.00 to −0.78‰),
slightly negative to highly positive Δ199Hg (mean:
−0.04 to 0.47‰), and slightly positive Δ200Hg (mean: 0.02 to 0.06‰) values. The positive PBM Δ199Hg signatures were likely caused by physiochemical reactions
in aerosols. The Δ199Hg/Δ201Hg ratio
varied from 0.94 to 1.39 in the cities and increased with the increase
in the corresponding mean Δ199HgPBM value.
We speculate that, in addition to the photoreduction of oxidized Hg,
other transformation mechanisms in aerosols (e.g., isotope exchange,
complexation, and oxidation, which express nuclear volume effects)
also shape the Δ199HgPBM signatures in
the present study. These processes are likely enhanced in the presence
of strong gas-particle partitioning of gaseous oxidized Hg (GOM) and
elevated levels of redox active metals (e.g., Fe), halides, and elemental
carbon. Based on Δ200HgPBM data presented
in this and previous studies, we estimate that large proportions (∼47
± 22%) of PBM were sourced from the oxidation of gaseous elemental
Hg followed by the partitioning of GOM onto aerosols globally, indicating
the transformation of Hg(0) to PBM as an important sink of atmospheric
Hg(0).
Dissolved gaseous mercury (DGM) and reactive mercury (RHg) are important Hg forms in natural water bodies. Knowledge of the concentration levels and isotope compositions of DGM and RHg in aquatic...
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