电导率与盐度

Water Quality Monitoring: Conductivity to Salinity Conversion

Salinity

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

Collect conductivity (μS/cm) and water temperature (C) data.

Use spreadsheet or calculator to convert conductivity and temperature data to salinity value.

     Conductivity:  (μS/cm)

Water temperature:  (℃)

                   

         Salinity:  (ppt)

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CO₂，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。

浓度（mol/L）	电导率（μS/cm）
0.0001	14.94
0.0005	73.90
0.001	147.0
0.005	717.8
0.01	1413
0.02	2767
0.05	6668
0.1	12900

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。

盐度详解