『Abstract
　Utilizing a sequential extraction technique this study provides the first quantitative analysis on the abundance of sedimentary phosphorus and its partitioning between chemically distinguishable phases in sediments of the Bering Sea, the Chukchi Sea and the Mackenzie River Delta in the western Arctic Ocean. Total sedimentary phosphorus (TSP) was fractionated into five operationally defined phases: (1) adsorbed inorganic and exchangeable organic phosphorus, (2) Fe-bound inorganic phosphorus, (3) authigenic carbonate fluorapatite, biogenic apatite and calcium carbonate-bound inorganic and organic phosphorus, (4) detrital apatite, and (5) refractory organic phosphorus. TSP concentrations in surface sediments increased from the Chukchi Sea (18μmol g^-1 of dried sediments) to the Bering Sea (22μmol g^-1) and to the Mackenzie River Delta (29μmol g^-1). Among the five pools, detrital apatite phosphorus of igneous or metamorphic origin represents the largest fraction (〜43％) of TSP. The second largest pool is the authigenic carbonate fluorapatite, biogenic apatite as well as CaCO3 associated phosphorus (〜24％ of TSP), followed by the Fe-bound inorganic phosphorus, representing 〜20％ of TSP. The refractory organic P accounts for 〜10％ of TSP and the readily exchangeable adsorbed P accounts for only 3.5％ of TSP. Inorganic phosphorus dominates all of phosphorus pools, accounting for an average of 87％ of the TSP. Relatively high sedimentary organic carbon and total nitrogen contents and low δ¹³C values in the Mackenzie River Delta together with the dominance of detrital apatite in the TSP demonstrate the importance of riverine inputs in governing the abundance and speciation of sedimentary phosphorus in the Arctic coastal sediments.

Keywords: Phosphorus; Sediment; Apatite; Arctic Ocean; Mackenzie River Delta』

1. Introduction
2. Methods
　2.1. Sample collection
　2.2. Measurements of organic carbon (OC) and total nitrogen (TN) and their stable isotope composition
　2.3. Sequential extraction procedure
　2.4. Analysis of dissolved phosphate
　2.5. Determination of total dissolved phosphorus in the extract
　2.6. Determination of content of iron oxides
　2.7. Determination of dissolved silicate
3. Results and discussion
　3.1. Organic carbon and total nitrogen and their stable isotopic composition
　3.2. Total sedimentary phosphorus
　3.3. Adsorbed inorganic and exchangeable organic phosphorus
　3.4. Iron oxides and Fe-bound phosphorus
　3.5. Authigenic carbonate fluorapatite, biogenic apatite and CaCO3-bound inorganic and organic phosphorus
　3.6. Detrital apatite phosphorus
　3.7. Refractory organic phosphorus
　3.8. Variations in sedimentary N/P ratios
4. Conclusions
Acknowledgments
References

図2　堆積性リンの異なる形態の連続抽出に用いた方法．抽出には全てのステップにおいて50ミリリットルを用いた．抽出物は溶存無機リン（DIP）と全溶存リン（TDP）について決定し、溶存有機リンはそれらの差として計算した．〔※Ruttenberg(1992)によるSEDEX法を基本にしたものである。〕

	0.5 gの乾燥堆積物
ステップ1	pH 8 1M MgCl2 2時間、25℃	DIP、TDP →	吸着された無機P （Adsorbed inorganic P） 交換可能な有機P （Exchangeable organic P）
ステップ2	BD（bicarbonate dithionite mixed solution、NaHCO3＋Na2S2O4） 4時間、25℃	DIP →	鉄結合無機P （Fe-bound inorganic P）
	0.5M NaCl すすぎ洗い、2時間、25℃
ステップ3	pH 4酢酸バッファー 6時間25℃	DIP、TDP →	自生アパタイト （Authigenic apatite） CaCO3結合無機および有機P （CaCO3-bound inorganic and organic P）
	1M MgCl2 すすぎ洗い、2時間25℃
ステップ4	1M HCｌ 16時間、25℃	DIP →	砕屑性アパタイト （Detrital apatite）
ステップ5	550℃で灰化 1M HCｌ 16時間、25℃	DIP →	溶けにくい有機P （Refractory organic P）