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• Salinity is a measure of the mass of dissolvedsalts (ionic constituents) in a given mass of solution and usuallyexpressed as parts per thousａnd (ppt).
• Ions commonly found in water include calcium,magnesium, potassium and sodium cations and bicarbonate, carbonate,chloride, nitrate, and sulfate anions.
• Conductivity is a good measure of salinity inwater. Other indirect measures are water density, sound speed, andrefractive index. All can be used to calculatesalinity.

Calculations

1. Collect conductivity (μS/cm) and water temperature (C) data.
2. Use spreadsheet or calculator to convert conductivity andtemperature data to salinity value.

        Conductivity:  (μS/cm)
   Water temperature:  (℃)
                      
            Salinity:  (ppt)

3. Equations used are based on the practical salinity scale andare valid for surface waters with salinity between 2 and 42 ppt.Please view the source to this document and consult StandardMethods for the Examination of Water and Wastewater if youhave questions or concerns.

電導(dǎo)率

水的電導(dǎo)率與其所含無機(jī)酸、堿、鹽的量有一定關(guān)系。當(dāng)它們的濃度較低時(shí)，電導(dǎo)率隨濃度的增大而增加，因此，該指標(biāo)常用于推測水中離子的總濃度或含鹽量。不同類型的水有不同的電導(dǎo)率。新鮮蒸餾水的電導(dǎo)率為0.2-2μS／cm，但放置一段時(shí)間后，因吸收了CO₂，增加到2—4μS/cm；超純水的電導(dǎo)率小于0.10/μS/cm；天然水的電導(dǎo)率多在50—500μS/cm之間，礦化水可達(dá)500—1000μS/cm；含酸、堿、鹽的工業(yè)廢水電導(dǎo)率往往超過10000μS/cm；海水的電導(dǎo)率約為30 000μS/cm。

電極常數(shù)常選用已知電導(dǎo)率的標(biāo)準(zhǔn)溶液測定。不同濃度溶液的電導(dǎo)率(25℃)列于下表。溶液的電導(dǎo)率與其溫度、電極上的極化現(xiàn)象、電極分布電容等因素有關(guān)，儀器上一般都采用了補(bǔ)償或消除措施。

水樣采集后應(yīng)盡快測定，如含有粗大懸浮物質(zhì)、油和脂，干擾測定，應(yīng)過濾或萃取除去。

具體操作方法參見電導(dǎo)儀說明書。