No abstract

No abstract

No abstract

A two‐compartment open model using plasma and seasonally variable lipid compartments was developed and validated for several organochlorines in herring gulls (Larus argentatus). Plasma clearance rate constants (k′pc, L·kg−1·d−1), plasma: whole‐body lipid partition coefficients (Kpf) and compartment sizes for lipid and plasma were obtained for juvenile gulls injected i.p. with a mixture of p,p′‐DDD, p,p′‐DDE, hexachlorobenzene, oxychlordane, γ‐hexachlorocyclohexane, trans‐chlordane, octachlorostyrene, dieldrin, mirex and photomirex. Concentrations in plasma were determined at 11 time points during the 239‐d study, and whole‐body contaminant burdens and lipid weights were determined at 3 time points. Mean Kpf for p,p′‐DDD and p,p′‐DDE (0.0038 ± 0.0002) was different from that of the other organochlorines (0.0058 ± 0.0005, n = 7). The latter values were close to the expected fraction lipid in plasma, indicating a simple thermodynamic partitioning between lipid pools in adipose tissue and plasma. Plasma clearance rate constants ranged from approximately 0.04 L·kg−1·d−1 for slowly clearing organochlorines such as p,p′‐DDE and mirex to 500 L·kg−1·d−1 for rapidly clearing γ‐hexachlorocyclohexane and trans‐chlordane. Simulations using these parameters and lipid weight regimes for individual experimental birds tracked observed plasma concentrations and final body burdens closely. Simulated whole‐body half‐lives of organochlorines in wild adult gulls were similar to those published for other species.

Radiolabelled [14C]DDE was used as a model compound to determine important factors in the clearance of persistent lipophilic compounds in free‐living herring gulls (Larus argentatus). Adult, breeding male and female gulls were dosed orally during incubation and then captured one week and one year later. After one week, [14C]DDE had equilibrated with native DDE in all tissues. The ratios of DDE levels on a lipid weight basis relative to whole body were as follows: muscle, 0.8 to 0.9; liver, 0.5 to 0.7; egg, 0.4; and brain, 0.1. The plasma/whole body lipid partition coefficient was 0.0041 ± 0.0014. The whole body annual average clearance rate was 0.95 ± 0.51 year−1 (half‐life = 264 d). Native DDE levels in males were twice those in females, but no differences were found for [14C)DDE after one year. The lower levels in females do not appear to be related to excretion of DDE in eggs or higher monooxygenase activity, but they may be related to differences in feeding ecology. Additional physiological and ecological factors must therefore be included in a proposed two‐compartment (plasma/whole body lipid) model of residue levels in eggs based on experimental data from caged gulls.