Accumulation and depuration of sediment‐sorbed C12‐ and C16‐polychlorinated alkanes by oligochaetes (Lumbriculus variegatus)

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Abstract
Oligochaetes (Lumbriculus variegatus) were exposed to sediment spiked with four 14C‐polychlorinated alkanes (PCAs) (C12H20C16 [56% Cl by weight], C12H16Cl10 [69% Cl], C16H31Cl3 [35% Cl], and C16H21Cl13 [69% Cl]) to measure bioaccumulation parameters and biotransformation. Chlorinated paraffins are industrial products that consist of thousands of different PCAs. Chlorinated paraffins are hydrophobic (log octanol–water partition coefficients [Kows] > 5.0) and are reported to have relatively high concentrations in sediment compared with other persistent organochlorines; however, no data exist on their bioavailability from sediment. The PCAs C12H20Cl6, C12H16Cl10, and C16H31Cl3 were readily available to sediment‐ingesting oligochaetes, whereas C16H21Cl13 had lower bioavailability. Uptake rates of the C12‐PCAs were greater than the C16‐PCAs, but half‐lives (t½s) were greater for the C16‐PCAs (t½ = 30‐33 d) than for the C12‐PCAs (t½ = 12‐14 d). Biota–sediment accumulation factors were >1 for C12H20Cl6, C12H16Cl10, and C16H31Cl3, but 16H21Cl13. Comparison of toluene‐extractable and ‐nonextractable 14C suggest that PCAs were biotransformed in aerobic sediments and by oligochaetes, and that the susceptibility to degradation in sediments decreases with increasing chlorine content. The relative abundance of individual PCAs may differ between sediment and benthic invertebrates because of differences in the bioaccumulation and degradation of PCAs of varying carbon chain length and chlorine content.

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