电导率与盐度

• Salinity is a measure of the mass of dissolved salts (ionic constituents) in a given mass of solution and usually expressed 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 in water. Other indirect measures are water density, sound speed, and refractive index. All can be used to calculate salinity.

Calculations

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

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

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

电导率

水的电导率与其所含无机酸、碱、盐的量有一定关系。当它们的浓度较低时，电导率随浓度的增大而增加，因此，该指标常用于推测水中离子的总浓度或含盐量。不同类型的水有不同的电导率。新鲜蒸馏水的电导率为0.2-2μS／cm，但放置一段时间后，因吸收了CO ₂，增加到2—4μS/cm；超纯水的电导率小于0.10/μS/cm；天然水的电导率多在50—500μS/cm之间，矿化水可达500—1000μS/cm；含酸、碱、盐的工业废水电导率往往超过10 000μS/cm；海水的电导率约为30 000μS/cm。

电极常数常选用已知电导率的标准氯化钾溶液测定。不同浓度氯化钾溶液的电导率(25℃)列于下表。溶液的电导率与其温度、电极上的极化现象、电极分布电容等因素有关，仪器上一般都采用了补偿或消除措施。

水样采集后应尽快测定，如含有粗大悬浮物质、油和脂，干扰测定，应过滤或萃取除去。

具体操作方法参见电导仪说明书。