[M-IS21_28PO1] Biogeochemistry

[MIS21-P13] Locaization of delta-34S value distribution in tree ring of Japanese cedar and evaluation on the S deposition history

*Takuya ISHIDA¹, Chisato TAKENAKA¹, Ichiro TAYASU² (1.Nagoya univ., 2.Kyoto univ.)

Keywords:Tree ring, Sulfur isotope, Morphology, Sulfur deposition

Anthropogenic sulfur emissions have been changed with human activities and affected sulfur dynamics in terrestrial ecosystems. Therefore, the information on sulfur deposition change should be important for understanding of the effects of anthropogenic sulfur on its dynamics. The stable sulfur isotope ratios (δ³⁴S) in tree rings are a useful archive for the history of sulfur deposition (Kawamura et al. 2006), since the δ³⁴S of various origins have specific values and there is few isotopic fractionation through absorption of sulfur by plant. However, only few studies have been conducted about the δ³⁴S in tree ring, and factors affecting the δ³⁴S in tree ring have not been understood. The aim of this study is to clarify the localization of δ³⁴S distribution in tree ring. We also perform the evaluation of sulfur deposition history at locations received heavy anthropogenic sulfur deposition using tree ring. The investigation was carried out at two study sites, Yokkaichi (YOK) and Inabu (INA) in central Japan. Both study sites have different histories of sulfur deposition. YOK had been affected by quite high anthropogenic sulfur deposition during 1960s. INA is located about 60 km NE of main urban area (Nagoya City). Three disk samples were obtained from Japanese cedar (Cryptomeria japonica) stump in 2013 at YOK and in 2012 at INA. The stumps at YOK were 63-year-old cut down in 2012 and those at INA were170-year-old cut down in 2007. In addition, at INA, three 40-year-old living stems were cut down in 2013 at INA and the disk samples were obtained. After washing and dried, the tree ring samples were divided into 5 year increments from bark toward the pith, and ground using power mill. The ground samples were digested with HNO₃ and H₂O₂ on a hot plate and after filtration BaCl₂ was added to obtain the BaSO₄. The δ³⁴S values (VCDT) were measured using EA-IRMS. To evaluation the localization of δ³⁴S in sapwood, heartwood and pith, the data from the stump and the living wood samples at INA were compared. These samples showed the different localization of δ³⁴S against the age. There were no difference of δ³⁴S between the sapwood (living wood) and the heartwood (stump) at the same age. However, the δ³⁴S values of the pith (living wood) were higher than those of heartwood (stump). This result indicated that the specific composition of sulfur compound might be consisted in pith and the δ³⁴S of the pith should be unsuitable for evaluation of sulfur deposition history. The δ³⁴S values in ring at YOK declined from the late 1950s to early 1970s and then increased again. This trend was almost homologized in ring at INA and air SO₂ concentration at near the YOK. In contrast, the minimum value of at YOK (-7.3‰) was lower than that at INA (-1.6‰). These results should be reflected by the deposition history of anthropogenic sulfur with low δ³⁴S value at each site.