Spectra Scientific | Professional Grade Groundwater Monitoring
Conductivity
Measures the ability of water to conduct electricity, reflecting its ion concentration, which is vital for assessing water quality and ecosystem health.
I. Introduction to Conductivity
What is Conductivity?
Measures water’s ability to carry an electrical current, indicating
ion concentration.
Why is Conductivity Important?
Determines water quality, contamination levels, and
salinity balance in ecosystems.
II. Understanding Conductivity
- Definition: Conductivity (σ) is directly related to ion concentration from dissolved salts and inorganic compounds.
- Units of Measurement: Siemens per meter (S/m) or microsiemens per centimeter (µS/cm) at 25°C.
- Resistivity Relationship: Resistivity (ρ) is the inverse of conductivity (ρ = 1/σ).
- Specific Conductance: Conductivity corrected to 25°C for standardized comparison.
III. Salinity and Its Measurement
- Definition: Total dissolved salts in water, commonly measured in parts per thousand (ppt) or practical salinity units (psu).
- Measurement Methods:
- Absolute Salinity (SA - TEOS-10): More precise, accounts for seawater composition.
- Practical Salinity (S - EOS-80): Conductivity-based estimation, widely used in oceanography.
- Salinity Units: Expressed in ppt, g/kg, or psu.
- Typical Salinity Levels:
- Freshwater (<1 ppt)
- Brackish water (1-33 ppt)
- Seawater (~35 ppt)
- Hypersaline (>38 ppt)
IV. Total Dissolved Solids (TDS)
- Definition: Sum of dissolved ions and particles (<2 microns) in water.
- Measurement Methods:
- Gravimetry: Evaporation-based measurement.
- TDS-Conductivity Relationship: TDS derived from conductivity using conversion factors.
- Water Classification by TDS:
- Freshwater (<1,000 ppm)
- Brackish water (1,000-10,000 ppm)
- Saline water (10,000-35,000 ppm)
- Hypersaline (>35,000 ppm)
V. Importance of Conductivity Monitoring
- Aquatic Life: High salinity disrupts osmoregulation, affecting freshwater species.
- Dissolved Oxygen Solubility: Higher salinity reduces oxygen solubility.
- Pollution Detection: Changes in conductivity indicate contamination from salts, chemicals, or organic pollutants.
- Ocean Circulation: Salinity affects water density, influencing global currents.
VI. Factors Affecting Conductivity Fluctuations
- Temperature: Higher temperatures increase conductivity.
- Water Flow: Freshwater inflows dilute conductivity, while mineralized groundwater increases it.
- Rainfall & Flooding: Can increase or decrease conductivity based on runoff composition.
- Stratification & Haloclines: Salinity gradients create layers in estuaries and oceans.
VII. Typical Conductivity Ranges
- Distilled Water: 0.5-3 µS/cm
- Tap Water: 50-800 µS/cm
- Freshwater Streams: 100-2,000 µS/cm
- Seawater: ~55,000 µS/cm
- Industrial Wastewater: >10,000 µS/cm
VIII. Conductivity, Salinity & TDS in Water Quality
Conductivity, salinity, and TDS are essential parameters for water quality assessment. Monitoring these factors ensures environmental sustainability, supports aquatic ecosystems, and helps detect contamination risks.