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The paper deals with the quality of the Pivka sinking stream at the Postojnska jama swallow-hole. In its superficial flow the Pivka receives waste communal and industrial waters from the villages; only the waste waters of Postojna itself are treated. By various methods of sampling the author tried to estimate properties of the Pivka quality. Periodical observations provided the variations of single parameters during the observations and pointed out critical situations occurring during winter and summer drought. During drought the water level is low and the Pivka sinks in upstream parts of the riverbed already. Specially critical is the low level of dissolved oxygen and the presence of organic pollution. Detailed systematic observation during 24 hours provided properties of water quality at low winter and summer levels and also at increase, or decrease of discharge. Prispevek obravnava kvaliteto ponikalnice Pivke na ponoru v Postojnsko jamo. Pivka sprejema odpadne komunalne in industrijske vode naselij, od katerih čistijo le odpadne vode Postojne. Z različnimi pristopi pri vzorčevanju so skušali zajeti čim več značilnosti Pivke. Občasna opazovanja so podala nihanja posameznih parametrov in opozorila na kritične situacije, ki nastopajo v zimski in poletni suši zaradi nizkega vodostaja Pivke že v zgornjem delu struge. Kritičnost se odraža v nizki vsebnosti raztopljenega kisika ter prisotnosti organskega onesnaženja. Podrobnejša sistematična opazovanja tekom 24 ur so podala značilnosti kvalitete ob nizkih zimskih in poletnih vodah ter ob naraščanju in upadanju pretoka. |
