Removal and bioaccumulation of anthropogenic, halogenated transient tracers in an anoxic fjord

• The persistence of the anthropogenic halogenated tracers, CFC-11 (CCl3F), CFC-12 (CCl2F2), CFC-113 (CCl2FCClF2), carbon tetrachloride (CCl4) and methyl chloroform (CH3CCl3) in oxygen-depleted waters was investigated in the anoxic fjord Framvaren in southern Norway. A model for the ventilation of the water in the fjord was created based on tritium and CFC-12 profiles. The results suggest that CFC-12 is stable in this environment, although still affected by particulate scavenging, while the other four halocarbon species shows signs of significant removal in the oxic/anoxic interface. The first-order removal coefficients were calculated to be 0.35, 0.19, 1.23 and 0.31 year(-1) for CFC-11, CFC-113, CCl4 and CH3CCl3, respectively. Significant downward flux of halogenated tracers by sinking organic matter is suggested by the model; the tracers are subsequently released to the water column by the remineralisation of the particles. This process acts as a sink of halogenated tracers in the surface waters, whereas it is a source for the deep waters. Our results points to bioaccumulation factors (BF) for the CFC tracers in the order of 4.4-5.4 (log BF), which is 100-600 times those previously reported. This might be of significance to near-shore, semi-enclosed, basins with a high flux of organic matter, but would still have little importance in open ocean basins. (c) 2004 Elsevier B.V. All rights reserved.

Subject headings

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Keyword

anoxic basins

bioaccumulation

biodegradation

halocarbons

tracers

Norway

Framvaren

DEEP-WATER FORMATION

CARBON-TETRACHLORIDE

PARTITION-COEFFICIENT

ORGANIC-CHEMICALS

WEDDELL SEA

BLACK-SEA

FRAMVAREN

ATLANTIC

CFC-11

CHLOROFLUOROCARBONS

Publication and Content Type

ref (subject category)

art (subject category)