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Dioxin, the collective term for polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans, are generated during various chemical and high temperature processes. They have been shown to be toxic to humans and animals with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exhibiting the greatest toxicity. Dioxin has been shown to exhibit immunotoxicity, reproductive and developmental toxicity in several animals. Epidemiological studies on groups of humans with prolonged or elevated exposure to dioxin have indicated increased cancer rates above threshold levels of exposure. Conversely, other studies have concluded that dioxin is a net anticarcinogen. There has been much study aimed at quantifying the relative contributions of the identified dioxin sources to the environmental load. Although some data suggests that burning of vegetation produces measurable amounts of dioxin it is rather industrial process waste streams which emit the greatest amounts. Processes implicated include organic chemical synthesis, metal processing, paper pulp bleaching and incineration of organic materials. Dioxin emission reduction strategies for high temperature processes have focussed upon the minimisation of the conditions at which dioxin forms in exhaust streams. Additionally, screening of process materials has been practised as have substitution of process chemicals in the pulp and paper bleaching industry.

This study centered around a transect of high-resolution (multi) cores from the 20° W meridian, 60-18° N in the northeast Atlantic. It spans a range of primary productivity zones, and was used to quantify and examine the vertical flux of organic carbon from the euphotic zone (50 m deep) to the sediment—water interface, through the sediment mixed layer, to burial in late Holocene sediment. The disequilibrium between members of the natural uranium decay series ( 226 Ra, 210 Pb and 210 Po) - which track the biogenic flux through scavenging of the particle-reactive nuclides —was employed. Together with experimentally and observationally derived factors, these data were used to convert nuclide flux to organic carbon flux resulting in an estimate of the water column flux of organic carbon. At the sediment-water interface micro-oxygen electrodes were used to quantify the consumption of organic carbon by aerobic respiration. It was noted that the estimated organic carbon flux is strongly dependent on the intensity of bioturbation. The late Holocene organic carbon burial flux was calculated for selected cores from measured organic carbon profiles and sediment accumulation rates over approximately the last 10000 years. This combined approach reveals a strong spatial and temporal signal in the flux of organic carbon through the deep sea in the northeast Atlantic, and provides additional insight into the fate of carbon in this area of the ocean.