SalinitySalinity

““In one drop of water are found In one drop of water are found all the secrets of all the oceans”all the secrets of all the oceans”

What is it?What is it? Salinity is the total amount of dissolved material Salinity is the total amount of dissolved material

in grams in one kilogram of sea water.in grams in one kilogram of sea water. The variability of dissolved salt is very smallThe variability of dissolved salt is very small Dimensionless quantity. Dimensionless quantity.

It has no unitsIt has no units

Notice that the range of salinity Notice that the range of salinity for most of the ocean's water is for most of the ocean's water is from 34.60 to 34.80 parts per from 34.60 to 34.80 parts per thousand, which is 200 parts thousand, which is 200 parts per million. per million.

Histogram of temperature and Histogram of temperature and salinity of cold water in the salinity of cold water in the oceans. Height is proportional oceans. Height is proportional to volume.to volume.

Global Ocean SalinityGlobal Ocean Salinity

MeasurementMeasurement

Never Never measured measured directlydirectly

Relative Relative proportions of proportions of the major the major constituents of constituents of sea water are sea water are constant.constant.

ChlorinityChlorinityChemical method for determining salinity.Chemical method for determining salinity.

Chloride is the most common dissolved ionChloride is the most common dissolved ion• Easiest to determine preciselyEasiest to determine precisely• Can be used to calculate the total concentration of Can be used to calculate the total concentration of

dissolved constituentsdissolved constituents• Used exclusively until the 1960’sUsed exclusively until the 1960’s

Salinity = 0.03 + 1.80655 x chlorinitySalinity = 0.03 + 1.80655 x chlorinityOrOr

S= 1.80655 CLS= 1.80655 CL

Ability of a substance to Ability of a substance to

conduct electric currentconduct electric current Proportional to salinity - a salty solution, Proportional to salinity - a salty solution,

because it is full of charged particles, will conduct electricity. because it is full of charged particles, will conduct electricity. Reciprocal of resistivity (ohms)Reciprocal of resistivity (ohms) mostly reported in microSiemens per centimeter (mS/cm) or mostly reported in microSiemens per centimeter (mS/cm) or

milliSiemens per meter (mS/m) at a standard reference milliSiemens per meter (mS/m) at a standard reference temperature of 25 degrees Celsius.temperature of 25 degrees Celsius.

Affected by temperature (25Affected by temperature (25ºC reference temp)ºC reference temp) Widely used in the 80’sWidely used in the 80’s Meters are expensiveMeters are expensive

ConductivityConductivity

RefractometerRefractometer

When light passes from a medium of one refractive index to When light passes from a medium of one refractive index to one with a different refractive index, the light bends one with a different refractive index, the light bends (refracts) at the interface. The amount it bends or, the (refracts) at the interface. The amount it bends or, the angle of refraction, depends on the difference in the two angle of refraction, depends on the difference in the two media's refractive indices.media's refractive indices. Refractive index –the ratio of the speed of light Refractive index –the ratio of the speed of light

traveling through a vacuum to the speed of light in traveling through a vacuum to the speed of light in the material being tested. the material being tested.

• Affected only significantly by temperature. Many Affected only significantly by temperature. Many refractometers are automatically temperature refractometers are automatically temperature compensated.compensated.

Measures density of liquidsMeasures density of liquids Expressed in terms of specific gravity – Expressed in terms of specific gravity –

describes the weight of dissolved describes the weight of dissolved material in the watermaterial in the water• ratio of the density of the substance being ratio of the density of the substance being

measured to the density of water at the measured to the density of water at the same temperature (1.00)same temperature (1.00)

• Specific gravity less than 1 are lighter than Specific gravity less than 1 are lighter than water, greater than 1 is heavierwater, greater than 1 is heavier

HydrometerHydrometer

•HOW DOES IT WORK?HOW DOES IT WORK? The hydrometer floats in the The hydrometer floats in the liquid. The level where the surface of the liquid liquid. The level where the surface of the liquid touches the scale indicates the specific gravity. Also, touches the scale indicates the specific gravity. Also, floating arm versions.floating arm versions.

YSI 85: Salinity, Conductivity, YSI 85: Salinity, Conductivity, Dissolved Oxygen & Dissolved Oxygen & Temperature MeterTemperature Meter

Multi-parameter probe provides Multi-parameter probe provides simultaneous measurement of:simultaneous measurement of:

TemperatureTemperature Dissolved oxygen (DO)Dissolved oxygen (DO) ConductivityConductivity SalinitySalinity

For advanced users, an adjustable conductivity For advanced users, an adjustable conductivity reference temperature and compensation factor can reference temperature and compensation factor can be used, as well as user defined equations for be used, as well as user defined equations for determining salinity.determining salinity.

Practical Take HomePractical Take Home

More than one way to skin a catMore than one way to skin a cat Understand your instrument, it’s limitations Understand your instrument, it’s limitations

and the principles behind how it worksand the principles behind how it works Something other than the parameter you are Something other than the parameter you are

measuring make affect your measurementmeasuring make affect your measurement You may need a different instrument to You may need a different instrument to

measure the same parameter under different measure the same parameter under different circumstancescircumstances

All instruments have a range of effectivenessAll instruments have a range of effectiveness

Quality ControlQuality ControlUsers of your data need to know how accurate and reproducible Users of your data need to know how accurate and reproducible

those data are!those data are!

Quality Assurance (QA) – broad plan for Quality Assurance (QA) – broad plan for maintaining quality in all aspects of a maintaining quality in all aspects of a programprogram Selection of parameters and proceduresSelection of parameters and procedures Data management and analysisData management and analysis Steps taken to determine validity of specific Steps taken to determine validity of specific

sampling or analysis proceduressampling or analysis procedures

Quality Control (QC)Quality Control (QC)

Steps you take while Steps you take while running your analysis running your analysis

or taking or taking measurements to measurements to

insure accuracy and insure accuracy and precision.precision.

Immediate ResponseImmediate Response

Quality Asessment Quality Asessment

After the fact After the fact assessment. assessment.

Blind Samples.Blind Samples.