11:00 〜 13:00
[AAS11-P15] 2020年中国ロックダウンと2021年豪雪がエアロゾル大気輸送に与えた影響
キーワード：物質輸送、降水、エアロゾル、大気汚染、栄養塩、異常気象
Aerosols composed of anthropogenic materials such as Asian loess and factory soot have been important nutrient sources for primary production (phytoplankton) in the surface ocean. For example, nitrate is the nutrient for phytoplankton, while sulfate denatures trace metals such as iron into soluble forms that are easily available to organisms. As one of the transit areas from the Asian continent to the Pacific Ocean, the snow cover of Mt. Tateyama Murodo. This characteristic has been used to assess the impact of transboundary pollution from continental sources. Recent events include 1) significant changes in China's atmospheric environment in 2020 due to lockdown by COVID-19, and 2) record-breaking heavy snowfall in the plains of Toyama Prefecture in the winter of 2021. In order to evaluate how these events affect the atmospheric transport of aerosols, this study compared the chemical composition of Mt. Tateyama Murodo and precipitation (rainfall and snowfall) in the plains of Toyama in 2020 and 2021.
The snow layers were collected at Mt. Tateyama Murodo in April 2021. As samples from the plain area, precipitation was collected from January to April on the roof of University of Toyama. The main chemical compositions of these samples were measured, including δ18O, δD, δ34S, REEs, and so on. Precipitation samples collected by the Toyama Pref. Environmental Science Research Center in 2020 were used for measurement.
The location of the loess layer and the d-value were used to estimate the snow cover timing on a monthly scale. High δ34S and nss-SO42-/NO3- values were identified in the 2020 sample. This result indicates anthropogenic emissions in China during the lockdown period (January to March 2020). These values could be attributed to the increased rate of major sulfate emissions from households without widespread desulfurization rather than from China factories. The total deposition of major chemical components in Mt. Tateyama Murodo in 2021 winter was much smaller than in 2020. On the other hand, deposition in the plains was higher in 2021 winter than in 2020. This suggests that intensive heavy snowfall deposited a large amount of chemical components in the plains and consequently reduced the amount deposited in the Tateyama area. This study emphasizes the threat that increasingly extreme weather events will reduce the nutrient supply to the Pacific Ocean via aerosols, and the importance of continuous monitoring of the snow cover in Mt. Tateyama.
The snow layers were collected at Mt. Tateyama Murodo in April 2021. As samples from the plain area, precipitation was collected from January to April on the roof of University of Toyama. The main chemical compositions of these samples were measured, including δ18O, δD, δ34S, REEs, and so on. Precipitation samples collected by the Toyama Pref. Environmental Science Research Center in 2020 were used for measurement.
The location of the loess layer and the d-value were used to estimate the snow cover timing on a monthly scale. High δ34S and nss-SO42-/NO3- values were identified in the 2020 sample. This result indicates anthropogenic emissions in China during the lockdown period (January to March 2020). These values could be attributed to the increased rate of major sulfate emissions from households without widespread desulfurization rather than from China factories. The total deposition of major chemical components in Mt. Tateyama Murodo in 2021 winter was much smaller than in 2020. On the other hand, deposition in the plains was higher in 2021 winter than in 2020. This suggests that intensive heavy snowfall deposited a large amount of chemical components in the plains and consequently reduced the amount deposited in the Tateyama area. This study emphasizes the threat that increasingly extreme weather events will reduce the nutrient supply to the Pacific Ocean via aerosols, and the importance of continuous monitoring of the snow cover in Mt. Tateyama.