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Quantitative Reconstruction of Sulfur Deposition Using a Mixing Model Based on Sulfur Isotope Ratios in Tree Rings
Author(s) -
Ishida Takuya,
Tayasu Ichiro,
Takenaka Chisato
Publication year - 2015
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2014.11.0506
Subject(s) - δ34s , deposition (geology) , sulfur , environmental science , terrestrial ecosystem , sulfate , atmospheric sciences , isotope analysis , stable isotope ratio , pollution , ecosystem , physical geography , geology , chemistry , ecology , paleontology , geography , structural basin , physics , oceanography , biology , nuclear physics , organic chemistry , quartz , fluid inclusions
Quantification of sulfur (S) deposition is critical to deciphering the environmental archive of S in terrestrial ecosystems. Here we propose a mixing model that quantifies S deposition based on the S isotope ratio (δ 34 S) in tree rings. We collected samples from Japanese cedar ( Cryptomeria japonica D. Don) stumps from two sites: one near Yokkaichi City (YOK), which is well known for having the heaviest S air pollution in the world, and one at Inabu‐cho (INA) in central Japan, which has been much less affected by air pollution. The δ 34 S profiles at both sites are consistent with S air pollution and contributions of anthropogenic S. The minimum value in YOK is lower than the δ 34 S values of anthropogenic S or any other possible source. Because the δ 34 S in the tree rings is affected by fractionation in the forest ecosystems, we used a mixing model to account for the isotope effects and to distinguish the sources of S. Based on the model results, we infer that the peak of S emissions at YOK occurred sometime between the late 1960s and early 1970s (489 mmol m −2 yr −1 ). This estimated value is comparable with the highest reported values in Europe. This is the first quantitative estimate of anthropogenic input of S in forest systems based on δ 34 S in tree rings. Our results suggest that tree ring data can be used when monitoring stations of atmospheric S are lacking and that estimates of S deposition using δ 34 S in tree rings will advance our understanding of the local‐scale S dynamics and the effect of human activities on it. Core Ideas We studied δ 34 S in tree rings to evaluate sulfur deposition in Japan. The δ 34 S profiles were consistent with sulfur air pollution. Isotope fractionation may affect δ 34 S in tree rings. We propose a mixing model to quantify sulfur deposition based on δ 34 S. The estimate suggests that the world's largest amount of sulfur was deposited in the past.