slanost

Slanost, also translated as salinity, is the level of dissolved salts in a substance, most commonly in water. It describes the concentration of inorganic ions such as sodium, chloride, calcium and sulfate in oceans, lakes, rivers, or soils. The term is used across oceanography, hydrology and agriculture, reflecting how salt content affects physical properties and biological processes. In practice, slanost is expressed in practical salinity units (PSU) or in parts per thousand (ppt, g/kg). For most purposes they are numerically similar, and standard seawater has a slanost of about 35 PSU or 35 ppt.

Measurement methods include conductivity meters, which infer salinity from electrical conductivity and are calibrated to PSU, and refractometers for quick field estimates. In soils, slanost is often assessed as soil salinity, typically reported as the electrical conductivity of a soil extract (ECe) or by saturation extract salinity.

Natural ranges vary: freshwater systems usually have slanost below 0.5 ppt; seawater about 35 ppt; brackish water from roughly 0.5 to 30 ppt; hypersaline waters exceed seawater salinity and can reach well above 40 ppt in isolated basins (for example, the Dead Sea and some evaporative lakes).

Biological and ecological significance: Slanost affects osmoregulation, enzyme activity and water uptake. Most freshwater organisms are limited by rising salinity, while specialized halophiles tolerate high levels. In plants, high soil slanost reduces germination and crop yields due to osmotic stress. Human activities, such as irrigation, drainage and climate change, can increase slanost in soils and estuaries.

Applications and management: Monitoring slanost is essential in desalination, aquaculture, agriculture and environmental assessment, informing water quality management and ecosystem health.