Toward
the Origins of Quadruple Sulfur Isotope Anomalies
in Modern Sulfate: A Multitracer Approach and Implications for Paleo-
and Planetary Atmospheres
posted on 2023-02-28, 12:35authored byBinyan Yin, Xiaoxiao Yu, Xiaomin Lin, Zhisheng Zhang, Yanli Zhang, Mang Lin
Sulfur isotope mass-independent fractionation signatures
(S-MIF)
have been widely found in modern sulfate aerosols. Their mechanistic
origins and potential implications for atmospheric sulfate formation
chemistry are however poorly understood. Of particular importance
is that the mystery of modern sulfate S-MIF hinders precise interpretations
of S-MIF in geological sediment and meteorite samples. Here, we examine
several proposed origins of modern sulfate S-MIF using a multiple-tracer
approach. Quadruple sulfur isotopes of sulfate aerosols collected
from Guangzhou, a megacity in South China, were measured along with
various chemical and isotopic tracers for high-altitude air masses,
biomass burning, and mineral dusts in the same samples. Similar to
previous studies, we found that negative Δ36S values
in modern sulfate aerosols are linked to combustions, and to a larger
extent, to high-temperature processes that may involve symmetry-dependent
recombination reactions of sulfur. The origins of Δ33S anomalies widely observed in modern sulfate aerosols remain elusive
and require further investigation before we can unambiguously use
this proxy to quantify sulfur emission and transformation pathways
in the modern atmosphere. From a comparative planetology perspective,
we highlight that a complete understanding of S-MIF in modern aerosols
is crucial for tracking paleo- and planetary atmospheres by multiple
sulfur isotope measurements in Phanerozoic sediments and Martian meteorites
because their S-MIF magnitudes are similar.