Underlying uncertainty in future projection of marine ecosystem feedbacks to climate change

AAS21-05発表要旨 / 日本地球惑星科学連合2012年大会（2012年5月20日～5月25日, 幕張メッセ国際会議場） / 日本惑星科学連合の許諾に基づき本文ファイルを掲

Atmospheric Deposition of Soluble Organic Nitrogen due to Biomass Burning

Atmospheric deposition of reactive nitrogen (N) species from large fires may contribute to enrichment of nutrients in aquatic ecosystems. Here we use an atmospheric chemistry transport model to investigate the supply of soluble organic nitrogen (ON) from open biomass burning to the ocean. The model results show that the annual deposition rate of soluble ON to the oceans is increased globally by 13% with the increase being particularly notable over the coastal water downwind from the source regions. The estimated deposition of soluble ON due to haze events from the secondary formation is more than half of that from the primary sources. We examine the secondary formation of particulate C-N compounds (e.g., imidazole) from the reactions of glyoxal and methylglyoxal with atmospheric ammonium in wet aerosols and upon cloud evaporation. These ON sources result in a significant contribution to the open ocean, suggesting that atmospheric processing in aqueous phase may have a large effect. We compare the soluble ON concentration in aerosols with and without open biomass burning as a case study in Singapore. The model results demonstrate that the soluble ON concentration in aerosols is episodically enriched during the fire events, compared to the without smoke simulations. However, the model results show that the daily soluble ON concentration can be also enhanced in the without smoke simulations during the same period, compared to the monthly averages. This indicates that care should be taken when using in-situ observations to constrain the soluble ON source strength from biomass burning. More accurate quantification of the soluble ON burdens with no smoke sources is therefore needed to assess the effect of biomass burning on bioavailable ON input to the oceans.Poster abstract A31G-3099 presented at 2014 Fall Meeting, AGU, San Francisco, Calif., 15-19 Dec

Atmospheric Chemistry Transport Modeling of Organic Nitrogen Input to the Ocean

Atmospheric deposition of reactive nitrogen (N) species from air pollutants is a significant source of exogenous nitrogen in marine ecosystems. Here we use a process-based chemical transport model to investigate global supply of soluble organic nitrogen (ON) from continental sources to the ocean. The present-day emissions of NO, NH3, and the primary ON are 46, 42, and 11 Tg N/yr. Comparisons of modeled deposition with observations at coastal and marine locations show overall good agreement for inorganic nitrogen and total nitrogen, but significant underestimates for ON when we explicitly calculated volatile ON and particulate ON in the model. The model results suggest that including soluble ON potentially emitted with carbonaceous aerosols and/or transformed from NH4+ on carbonaceous and dust aerosols contributes to a better predictive capability of the deposition rates. The estimated annual total deposition rates of ON to the ocean range from 0.9 to 5.9 Tg N/yr, depending on the solubility at emission and/or the transformation on aerosols. The model results show a clear distinction in the vertical distribution of ON between different sources (i.e., the primary or secondary formation). These results highlight the necessity of improving the process-based quantitative understanding of the solubility of ON in emitted particles and the chemical reactions of inorganic nitrogen species with organics in aerosol and cloud water.Poster abstract B43E-0545 presented at 2013 Fall Meeting, AGU, San Francisco, Calif., 9-13 Dec

Reconciling modeled and observed atmospheric deposition of soluble organic nitrogen at coastal locations

Atmospheric deposition of reactive nitrogen (N) species from air pollutants is a significant source of exogenous nitrogen in marine ecosystems. Here we use an atmospheric chemical transport model to investigate the supply of soluble organic nitrogen (ON) from anthropogenic sources to the ocean. Comparisons of modeled deposition with observations at coastal and marine locations show good overall agreement for inorganic nitrogen and total soluble nitrogen. However, previous modeling approaches result in significant underestimates of the soluble ON deposition if the model only includes the primary soluble ON and the secondary oxidized ON in gases and aerosols. Our model results suggest that including the secondary reduced ON in aerosols as a source of soluble ON contributes to an improved prediction of the deposition rates. The model results show a clear distinction in the vertical distribution of soluble ON in aerosols between different processes from the primary sources and the secondary formation. The model results (excluding the biomass burning and natural emission changes) suggest an increase in soluble ON outflow from atmospheric pollution, in particular from East Asia, to the oceans in the twentieth century. These results highlight the necessity of improving the process-based quantitative understanding of the chemical reactions of inorganic nitrogen species with organics in aerosol and cloud water

Does a Theoretical Estimation of the Dust Size Distribution at Emission Suggest More Bioavailable Iron Deposition?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95443/1/grl28895.pd

Global modeling of SOA: the use of different mechanisms for aqueous-phase formation

There is growing interest in the formation of secondary organic aerosol (SOA) through condensed aqueous-phase reactions. In this study, we use a global model (IMPACT) to investigate the potential formation of SOA in the aqueous phase. We compare results from several multiphase process schemes with detailed aqueous-phase reactions to schemes that use a first-order gas-to-particle formation rate based on uptake coefficients. The predicted net global SOA production rate in cloud water ranges from 13.1 Tg yr-1 to 46.8 Tg yr-1 while that in aerosol water ranges from -0.4 Tg yr-1 to 12.6 Tg yr-1. The predicted global burden of SOA formed in the aqueous phase ranges from 0.09 Tg to 0.51 Tg. A sensitivity test to investigate two representations of cloud water content from two global models shows that increasing cloud water by an average factor of 2.7 can increase the net SOA production rate in cloud water by a factor of 4 at low altitudes (below approximately 900 hPa). We also investigated the importance of including dissolved Fe chemistry in cloud water aqueous reactions. Adding these reactions increases the formation rate of aqueous-phase OH by a factor of 2.6 and decreases the amount of global aqueous SOA formed by 31%. None of the mechanisms discussed here is able to provide a best fit for all observations. Rather, the use of an uptake coefficient method for aerosol water and a multi-phase scheme for cloud water provides the best fit in the Northern Hemisphere and the use of multiphase process scheme for aerosol and cloud water provides the best fit in the tropics. The model with Fe chemistry underpredicts oxalate measurements in all regions. Finally, the comparison of oxygen-to-carbon (O / C) ratios estimated in the model with those estimated from measurements shows that the modeled SOA has a slightly higher O / C ratio than the observed SOA for all cases

大気質改善に対する海洋への可溶性鉄供給量変化の将来予測

緒言 エアロゾルにより供給される可溶性鉄は遠洋の植物プランクトンの成長にとって必要な栄養素となる。生物・地球化学過程として海洋の鉄循環を含む従来の数値モデルでは、土壌起源のエアロゾル粒子中に一定の割合で可溶性鉄が存在すると仮定されている。しかし、エアロゾル粒子中の可溶性鉄濃度の見積もりに関わる不確かさは数値モデルによる大気中二酸化炭素濃度予測に多大な不確実性を与える。そこで、生態系と気候との複雑な相互作用を考慮にいれた形で地球温暖化予測するためには、鉄イオンや錯体などの溶存態供給量を推定できる数値モデルが必要となる。本研究では、全球エアロゾル化学輸送モデルを用いて、将来予想される大気質改善に対する海洋への可溶性鉄供給量変化の将来予測に与える影響を評価する。 手法 我々のエアロゾル化学輸送モデルは、鉱物エアロゾル中の比較的不溶な鉄が酸性物質と化学反応し、溶解する過程を動的に表現している。植生と化石燃料の燃焼起源の鉄はエアロゾルの溶液中で、一定の鉄溶解度に仮定されて、直ちに溶解する。将来予測実験では、大気汚染物質の排出量データとしてIPCC第5次報告書で用いられたシナリオのうちRCP4.5を使用した。 数値実験結果と考察 従来、エアロゾル粒子中に含まれる主要な可溶性鉄は土壌粒子中に存在する酸化鉄（ヘマタイト）の酸による溶解によって生成されるとして仮定されていた。しかし、大部分のダスト粒子は大気中で塩基性を保つ上に、ヘマタイトの酸による溶解速度は極めて遅いため、ヘマタイトの酸による溶解のみを考慮に入れた可溶性鉄の割合の計算結果は観測結果を過小評価する。本研究では、土壌粒子中に反応性の高い化学形態にある鉄が含有することを考慮にいれた。その場合、観測結果との整合性が顕著に改善されることを明らかにした。本研究の結果は、植物プランクトンにとって利用されやすい性質となる鉄の存在量を予測するためには、反応性の高い化学形態にある鉄含有量を正確に算出する必要があることを示唆する。さらに、大気汚染物質の排出量削減に対して、数値モデルによる将来予測の計算結果は可溶性鉄供給量が将来減少することを示唆した。大気質改善に対する海洋への可溶性鉄供給量変化の予測を向上させるためには、比較的清浄な環境での鉄溶解度をより良く理解する必要がある。しかし、南大洋上でエアロゾル粒子中の可溶性鉄濃度の観測例が極めて少ないため、比較的清浄な環境における数値モデルの結果を評価することは困難である。今後、モデルの高度化を図るためには、比較的清浄な地域でのエアロゾル中可溶性鉄を対象として、現場観測と室内実験、さらには数値モデルの結果を統合的に検討することが重要である。日本気象学会2013年度春季大会（2013年5月15日～18日, 国立オリンピック記念青少年総合センター） / 発表番号: B16

Role of acid mobilization in projected response of soluble iron supply to improvement of air quality in the future

Acidification of dust aerosols may increase aerosol iron (Fe) solubility, which is linked to mineral properties (e.g., crystallinity, grain size and impurity content). The mixing of the mineral dust with combustion aerosols can also elevate iron solubility when aerosol loading is low. Here, we use a process-based chemical transport model [1, 2] with improved treatment of Fe in mineral dust and proton-promoted dissolution scheme to investigate the deposition of soluble iron and its response to changes in anthropogenic emissions of both primary particles and precursor gases. Comparisons of modeled Fe dissolution curves with the measured dissolution rates show overall good agreement under acidic conditions. The improved treatment of Fe in mineral dust and the proton-promoted dissolution scheme results in reasonable predictive capability for iron solubility over the oceans in the Northern Hemisphere. Our model results suggest that iron included in aluminosilicate dust can be released in the form of ferrihydrite colloids, nanoparticles and aqueous species during the long-range transport and thus provide an important bioavailable source of iron to the oceans. As a result of considering both the atmospheric processing of mineral dust and source composition of combustion aerosols, soluble iron deposition to the subarctic North Pacific is projected to respond nonlinearly to changing emissions of fly ash and air pollutant gases (e.g., SO2, NO2 and NH3). These results could have important implications for iron fertilization of phytoplankton growth, and highlight the necessity of improving the process-based quantitative understanding of the response of the chemical modification in iron-containing minerals to environmental changes. [1] Xu, & Penner (2012) Atmos. Chem. Phys. 12, 9479-9504, doi:10.5194/acp-12-9479-2012. [2] Ito (2013) Global Biogeochem. Cycles 27, 1-10, doi: 10.1029/2012GB004378.Conference abstract (August 25-30, 2013. Goldschmidt 2013 in Florence, Italy

Radiative forcing of iron oxides from combustion sources

Combustion aerosols affect the climate by absorbing and scattering radiation. Iron (Fe) oxides emitted from combustion sources largely reside in supermicron aerosols. Fe oxides on aerosols are known to absorb sun light and heat the atmosphere. However, supermicron aerosols from combustion sources are ignored for radiative forcing in climate models. Here, we use a global chemical transport model and a radiative transfer model to estimate the radiative forcing of Fe oxides from combustion sources. The model results suggest that Fe oxides from combustion sources significantly contribute to a warming effect at the top of the atmosphere over the air polluted regions such as China and India as well as biomass burning source regions. However, the estimates strongly depend on chemical speciation of Fe oxides, which is also important for bioavailability. These results suggest comprehensive observations are needed to fully understand the effects of Fe oxides on the net radiative forcing and ecosystems.Poster abstract A21K-2305 presented at 2017 Fall Meeting, AGU, New Orleans, Louisiana, 11-15 Dec

Aerosol radiative forcing of pyrogenetic iron oxides

Abstract ID 4.035, 2018 joint 14th iCACGP Quadrennial Symposium and 15th IGAC Science Conference, Takamatsu, Kagawa, 25-29 September 201