AbstractThree outdoor pools (5.5 m3) were treated with 14C1,3,6,8‐tetrachloridibenzo‐p‐dioxin (1,3,6,8‐T4CDD) at concentrations of 98, 245 and 980 ng/L, and the movements and accumulation of the compound were monitored in air, water, sediment and vegetation over a 426‐d period. The concentrations of 1,3,6,8‐T4CDD in the air above the treated pools ranged from 8.4 to 18.8 ng/m3during the first day after treatment. Total14C concentration in the water column declined rapidly, with more than 90 lost from the water phase within 96 h (t1/2= 14.0 to 28.5 h). The sediments were the major reservoir for the compound, accounting for 34 to 80 of the added compound at 34 d and 5 to 14 at 426 d. Total 14CT4CDD concentrations in the sediments increased at 90 d, in part because of the end‐of‐season deposition of rooted vegetation. 1,3,6,8‐T4CDD degraded in natural water in Pyrex flasks at similar rates in sterile and nonsterile waters (t1/2= 6.3 to 8.0 d) in sunlight, but not under darkened conditions. A single, polar photodegradation product (retention time 0.82 relative to 1,3,6,8‐T4CDD) was detected by HPLC, and 20 of the14C was unextractable within 10 d. Similar degradation products were noted in the water and sediments (90 and 426 d). In duckweed (Lemnasp.) and (Potamogetonsp.), concentration factors for 1,3,6,8‐T4CDD ranged from 2.5 to 3.4 × 104and from 0.27 to 2.0 × 105, respectively. At 426 d posttreatment, 5 to 8 of the applied 1,3,6,8‐T4CDD could be accounted for in all aquatic compartments, with an additional 4 to 6 of14C present as unidentified polar products
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