Dissolved oxygen measurement (water sampling procedure and titration procedure)
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At the CTD water sampling, seawater was collected in a Niskin water sampling bottle (gray bottle pictured below). This seawater is divided and placed into glass bottles for oxygen measurement (oxygen bottle, DO bottle). Once placed in the glass bottle (DO bottle), fixative solution I and II are injected into the bottle, and then the lid of the DO bottle is put on.
In the DO water sampling process, it is important to prevent oxygen from the air from entering the sample seawater in the glass bottle, to avoid bubbles, and to reduce contact with the air as much as possible.
海水中in the sea 二スキンボトル降下Two Skin Bottle Descent 任意の深度で蓋閉めLid closed at any depth エアベントair vent 採水コックWater sampling cock 留め円盤付きWith clamping disk 甲板上で採水作業Water sampling on deck 採水チューブ取り付けWater sampling tube installation エアベント開けるOpen air vent チューブ先から水出るWater comes out of the end of the tube. 上向きに水を出しながらチューブを揉むRub the tube while letting the water out in an upward direction チューブ内壁の気泡を除くRemove air bubbles from the inner wall of the tube DO瓶を優しく洗うGently wash DO bottles. 泡立てないNo bubbling. ２回ほどtwice 瓶の蓋も洗うwash the lid of a jar too ③以降、チューブ先からは水を流し続けるAfter ③, water continues to flow from the end of the tube. 水を節約するため、指でつまんで、水量を調節するTo conserve water, pinch with fingers to adjust water volume 完全に水の流れを止めると、再び泡がチューブ内壁に付く可能性ありIf the water flow is completely stopped, bubbles may stick to the inner wall of the tube again DO瓶の底までチューブを入れるFill the tube to the bottom of the DO bottle. 泡立たないように、指でチューブをつまんでゆっくり水を満たすFill the tube slowly with water by pinching the tube with your fingers so it does not foam. 水が満たされたら、指つまみを開放するOnce the water is filled, release the finger knob. 勢いよく、水をオーバーフローさせるVigorous, overflowing water オーバーフローの量は、瓶容量のおよそ２倍Overflow volume is approximately twice the bottle capacity DO瓶から、チューブをゆっくり引き抜くGently pull the tube out of the DO bottle. 泡立たないように、指でチューブをつまんでPinch the tube with your fingers to keep it from bubbling. 最後、チューブ先が海面に接するところで、チューブからの水フローを完全に止めるAt the end, when the end of the tube touches the sea surface, the water flow from the tube is completely stopped. 液面から最後引き抜くとき、水が流れていると、泡立ってしまうWhen the last pull is made from the liquid surface, if water is flowing, it bubbles up. ポンプ式液注入器Pump type liquid injector ディスペンサーdispenser 固定液をディスペンサーを使って、DO瓶に注入 液出口を液面下に浸して、ワンプッシュFixing solution is dispensed and injected into the DO bottle. 液面下で指を離してよいYou may release your finger below the liquid surface. 瓶をゆっくり落とすDrop the bottle slowly. DO瓶を上下逆さまにして、気泡の有無を確認Turn DO bottle upside down and check for air bubbles 気泡があったら、やり直しIf there are air bubbles, start over.
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The following is a description of the DO titration method using the Winkler method (manual analysis).
溶存酸素測定の手順Dissolved oxygen measurement procedure Ⅰ液、Ⅱ液を入れたのち、蓋をしてオーバーフローさせるAfter adding Liquid Ⅰ and Liquid Ⅱ, cover and overflow 上下転倒して良く撹拌Stir well by inverting up and down 静置してよく沈殿させるAllow to stand and settle well 蓋をゆっくり外しRemove the lid slowly. スポイトで上澄み液を10mlほど吸い上げコニカルビーカーに移すSiphon off about 10 ml of the supernatant liquid with a dropper and transfer to a conical beaker. 上澄み液supernatant fluid 沈殿物sediment 机面でくるくる回転、沈殿を溶解させるSpinning on the desk surface, dissolving sedimentation コニカルビーカーにすべて移すTransfer all to a conical beaker. 洗瓶の純水でDO瓶を洗い、洗液もコニカルビーカーに移すWash DO bottles with pure water in wash bottle and transfer wash solution also to conical beaker ビュレットの液面の目盛を記録するRecord the liquid level scale of the burette. ビューレットからチオ硫酸ナトリウムをコニカルビーカーに滴下Drops of sodium thiosulfate from burette into conical beaker コニカルビーカーは机面上でクルクル回転Conical beakers spin around on the desk surface 薄黄色になったら、スポイトでデンプン溶液を1ml加えるWhen light yellow, add 1ml of starch solution with a dropper 色が無くなったところを、滴定の終点とする。The endpoint of the titration is the point where the color disappears. 色の有無の判別が難しければ、最後の一滴を滴下する前の目盛を読んでおく。一滴たらしてみて、判断すればよいIf it is difficult to determine the presence or absence of color, read the scale before dropping the last drop. Just try one drop and judge.
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