Effects of organic material on the bioavailability, toxicokinetics and toxicity of xenobiotics in freshwater organisms

Abstract

Pohjoisille ekosysteemeille tyypillinen runsas orgaanisen aineksen määrä joko liuenneena vedessä tai järvien pohjamudassa voi sitoa useita kemiallisia saasteita ja siten vähentää eliöiden altistumista niille sekä siitä syntyviä myös koko ekosysteemille haitallisia vaikutuksia. Anna Nikkilän tutkimuksessa havaittiin, että orgaaninen aines voi vähentää merkittävästi harvasukamadon sekä vesikirpun altistumista tietyille rasvaliukoisille ympäristömyrkyille aromaattisten monirenkaisten hiilivetyjen (pyreeni, reteeni) sekä kloorifenolien (2,4,5-trikloorifenoli, pentakloorifenoli) ryhmistä. Osa tutkituista yhdisteistä sitoutui orgaaniseen ainekseen eikä näin ollut eliöille altistavassa muodossa. Vesiliukoisen rikkakasvien torjunta-aineen (atratsiini) altistavuuteen veden liukoisella orgaanisella aineksella ei ollut vaikutusta. Päällyslevien yhteisörakenne ja eliöihin liittyvät ominaisuudet vaikuttavat atratsiinin biokertymiseen enemmän kuin liukoisen orgaanisen aineksen määrä tai laatu. Kaikki tutkitut vierasaineet kuitenkin kertyivät tutkimuseliöihin orgaanisen aineksen sitomiskyvystä huolimatta.

The effects of organic carbon, as dissolved in water (DOC) or in sediment(SOC), on the binding, bioavailability, toxicokinetics and toxicity of organicxenobiotics were studied. The binding of pyrene (log Kow 5.2) to DOC was fairlylow, but mainly related to the amount of DOC. Pyrene uptake by the waterfleaDaphnia magna decreased by 17 % in the high-DOC water (17.4 mg DOC/l)compared to that in DOC-free water. Pyrene also became less bioconcentratedin D. magna in DOC-rich waters than in the DOC-free reference water. Atrazine(log Kow 2.7) uptake and elimination, in turn, were not affected by the amount ofDOC. Both the uptake and elimination of atrazine were higher in themultispecies periphyton communities than in D. magna. The atrazinebioconcentration was low, both in the periphyton and D. magna, but again,higher in the periphyton. A substantial concentration of SOC also decreased thebioavailability and uptake of retene (log Kow ~ 6), 2,4,5-trichlorophenol (2,4,5-TCP) and pentachlorophenol (PCP) (log Kow values 3.8 and 5.0, respectively) forthe oligochaete worm Lumbriculus variegatus. Retene was chronically non-toxicto the worms at 200 µg retene/g sediment dry weight. DOC and SOC can thusdecrease the bioavailability of the lipophilic pyrene, retene and PCP as well asthe relatively lipophilic 2,4,5-TCP. The bioavailability of a more hydrophilicatrazine is not affected by DOC. The periphyton community structure andfactors related to organisms affected the bioconcentration of atrazine more thanthe quantity or quality of DOC did. The lethal body residues for both thechlorophenols in L. variegatus were practically the same in freshwater andsediments, expressing the usefulness of this end point for more accuratepredictions on the bioavailability and toxicity of chemicals. Coexposure to UV-Bradiation enhanced the acute toxicity of pyrene to D. magna but DOC decreasedthe photomodification of the freely dissolved pyrene by diminishing theamount of light coming into contact with the parent compound.