The Contribution of Volcanic Eruptions of Miyake Island to Sulfur Isotope Ratios of Sulfate in Atmospheric Bulk Deposition in Metropolitan Tokyo, Japan

Abstract

In July 2000, a volcanic eruption took place on Miyake Island (Miyakejima), 150 kmsouth of metropolitan Tokyo, after last erupting 17 years ago. Volcanic gases released by this eruption were transported toward the main Japanese Island of Honshu. High SO₂ concentrations and acidic precipitations were detected at various locations in Japan. Atmospheric bulk depositions in Bunkyo were collected and SO₄^2- concentrations and δ³⁴S were measured, to study the influence of volcanic emission on the bulk deposition chemistry. The S0₄^2-_nss concentrations and deposition flux increased with activity of Miyakejima volcano. Air mass trajectory at 850hPa passed over the Kanto area from Miyakejima.δ³⁴S_nss values tended to increase since August 2000, reaching values close to the δ³⁴S value of volcanic ashes from Miyakejima (about 6‰). Also, 634Snss values of bulk deposition in Ohta and δ³⁴S_nss values of aerosol in Wako showed an increasing trend. These results demonstrate that the Miyakej ima eruption may have an important influence on bulk deposition chemistry in Bunkyo. We roughly calculated the contribution ratio of S0₄^2- in Miyakejima eruption using δ³⁴S values. As a result the highest contribution ratio was over 90% from October 1 to 3, 2000.