Uptake and Elimination of 4-Nonylphenol in the Enchytraeid Enchytraeus albidus

We determined the uptake and elimination kinetics of 4-nonylphenol (4-NP) in Enchytraeus albidus. A relatively fast degradation of 4-NP in test soil occurred at 20°C (λ = 0.11 day⁻¹). The concentration of 4-NP in worm tissue followed a three-phase kinetics model, with a short phase of fast 4-NP accumulation shortly after exposure start (k ᵤ = 0.97 mg kg⁻¹ day⁻¹), followed by partial elimination (K ₑ₁ = 1.47 day⁻¹) until reaching the equilibrium phase (A = 44.7 mg kg⁻¹ fresh tissue), and finally the elimination upon transfer to uncontaminated soil (K ₑ₂ = 0.67 day⁻¹). During uptake, the internal concentration was similar to the concentration found in the soil, with a BAF ~ 1. In un-spiked soil, elimination took place within the first 24 h (elimination t₁/₂ ~ 1 day).