Cov tshuaj tshem tawm hauv dej yog ib qho zoo uas muaj cov khoom tawg uas yog li 0.1μm-100μm. Pom los ntawm qhov muag liab qab. Cov xau no feem ntau yog los ntawm cov xuab zeb, av nplaum, protozoa, algae, kab mob, kab mob, thiab macromolecular organic teeb meem, thiab lawv feem ntau raug tshem tawm hauv cov dej ntws. Lub turbidity ntawm dej kuj yog tshwm sim los ntawm tej yam no.
Cov lus tsis sib haum uas tuaj yeem tshem tawm hauv dej hiav txwv kom ntev ntev. Qee zaum hu ua cov kev tshem tawm lossis tshem tawm cov colloids. Nws muab faib ua ob ntu: organic thiab inorganic. Cov organic feem ntau tso tawm cov khoom pov tseg, uas yog tsim ntawm carbohydrates (saib carbohydrates), protein (saib protein), lipids (saib lipids), thiab lwm yam. ), cov zaub mov hauv dej (xws li precipitated glauconite thiab staurolite thiab lwm yam silicates, carbon).