Alternative Title極東ロシアにおける変動する大気環境に対する森林集水域の応答に関する研究
Note (General)Acid deposition and following acidification are processes that can be associated with the atmospheric pollution. Even with decreased emission levels of SO2 and NOx, acid deposition continues to be one of the important ecological problems in the world. A number of studies related to the ecosystem recovery from excess sulfur (S) and nitrogen (N) deposition have been published in different regions of the world. Even so, ongoing acidification could be found in some areas. One of such examples is Komarovka river (KMR) situated in the Russian Far East. One of the sites for the Acid Deposition Monitoring Network in East Asia (EANET), Primorskaya, is situated there, providing a long-term data on wet deposition (WD), air concentrations for dry deposition (DD), and stream water (SW). However, the processes undergoing at the catchment are still not well understood. For the present study, the following objectives were defined: to evaluate the acidification situation and determine possible influencing factors of changing deposition and discharge fluxes; to compare the seasonal deposition and discharge trends at KMR; and to characterize the catchment in terms of sensitivity to atmospheric deposition in comparison to other sites in the Sea of Japan region. Compared to the many other sites in the East Asia region, the climate at KMR is drier and colder during the winter. The ratio of sea-salt fraction in precipitation is quite low. At the same time, SW can be characterized by high alkalinity and buffering capacity. The upstream of the river belongs to the national reserve territories, and the influence of the human activities at the catchment itself is very low. Due to its whereabouts near the borders, KMR is a possible object of a long-range transport influence. Therefore, KMR can serve as a rather unique and interesting subject of study, based on which it could be possible to understand the acidification processes more precisely. In the study, the trend analysis of WD, DD, and SW fluxes was performed based on data from EANET monitoring. Results for the period 2005-2020 are presented in this thesis. The DD fluxes were calculated from meteorological and air concentration data by the inferential method. The contribution of S by the DD flux into the total deposition was decreasing from 2011 to 2018. The WD fluxes of sulfate (SO42-) and nitrate (NO3-) have a changing point from decreasing to increasing after 2011 and 2014, respectively. Those trends seem to be not consistent with the latest trends of emissions that decrease in the region. Amount of precipitation tended to rise during the warm season starting around 2010, suggesting its contribution to an increase in fluxes of SO42- and NO3-. Phenomena of SW acidification was detected for KMR alongside with the increase of SO42- and NO3- concentrations. In general, decreasing trend of pH in SW is going against increasing trend of rainwater pH. On the other hand, the recent increase in SW fluxes of SO42- and NO3- could be attributed to the rise of precipitation amount during the warm season, following an increase in WD, and to the overall increase in SW discharge. The input-output balance shows discrepancies in S and Ca outputs, while uncertainties in flux estimations should also be taken into account. It was suggested that the excess S output could be attributed to the mobilization of S formerly accumulated on the catchment, including geological S weathering. To better understand mechanisms of the acidification phenomena at KMR, the comparison with two sites of the same Sea of Japan region (Ijira and Kajikawa) was performed. These forested catchments were characterized by the higher levels of dissolved inorganic nitrogen (DIN) concentration in WD. However, NO3- concentrations in SW of KMR appeared to rise more significantly in response to deposition. The study showed the phenomena of acidification of KMR SW in conditions of decreasing emission levels of acidifying precursors. The excess discharge of S suggests the possibility of mobilization of previously accumulated material into the SW. Also, the relationship between increases in deposition and discharge fluxes and the climate change was suggested. In addition, KMR appears to be more sensitive to the acidification compared to the sites of the same region. Thus, responses of forested catchments not only to changing atmospheric environment but also to the climate change should be further investigated in the future research.
新大院博(農)第230号
Collection (particular)国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文
Date Accepted (W3CDTF)2023-05-05T22:12:34+09:00
Data Provider (Database)国立国会図書館 : 国立国会図書館デジタルコレクション