title: Bioaccumulation and bound-residue formation of a branched 4-nonylphenol isomer in the geophagous earthworm Metaphire guillelmi in a rice paddy soil.
abstract: Nonylphenols (NPs) are the breakdown products of the nonionic surfactants nonylphenol ethoxylates and are toxic pollutants. Here we studied the bioaccumulation, elimination, and biotransformation of NP (12.3 mg kg(-1) soil dry weight) in a typical Chinese geophagous earthworm, Metaphire guillelmi, in a rice paddy soil, using 4-[1-ethyl-1,3-dimethylpentyl]phenol (4-NP(111)), the main constitute of technical NP, radiolabeled with (14)C. Earthworms rapidly bioaccumulated (14)C-4-NP(111) following a two-compartment first-order kinetics model. At steady state (after 20 days exposure), the normalized biota-soil accumulation factor amounted to 120, and 77% of the accumulated radioactivity were present as nonextractable bound residues. The total radioactivity was eliminated from the earthworm following an availability-adjusted decay model and controlled by the elimination rate of the bound residues (half-life = 22.6 days). The extractable residues consisted mainly of one less-polar metabolite (37%) and polar compounds (50%), including glucuronide conjugates of 4-NP(111) and the metabolite; and free 4-NP(111) accounted for only 9% of the total extractable residues. This study provides the first results of the toxicokinetics and biotransformation of 4-NP in a terrestrial organism, and underlines the significant underestimation of the bioaccumulation and risk assessment based only on free NP in earthworms.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, 22 Hankou Road, 210093 Nanjing, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Shan
authors.forename: Ting
authors.initials: T
authors.lastname: Wang
authors.forename: Chengliang
authors.initials: C
authors.lastname: Li
authors.forename: Erwin
authors.initials: E
authors.lastname: Klumpp
authors.forename: Rong
authors.initials: R
authors.lastname: Ji
mesh_terms: D000383:Agriculture; D000818:Animals; D001345:Autoradiography; D001673:Biodegradation, Environmental; D001711:Biotransformation; D002250:Carbon Radioisotopes; D002855:Chromatography, Thin Layer; D005247:Feeding Behavior / Q000502:physiology*; D005966:Glucuronidase / Q000378:metabolism; D007536:Isomerism; D007700:Kinetics; D009835:Oligochaeta / Q000378:metabolism*; D012275:Oryza; D010636:Phenols / Q000737:chemistry* / Q000378:metabolism*; D012987:Soil
chemical_list: D002250:Carbon Radioisotopes; D010636:Phenols; D012987:Soil; D005966:Glucuronidase; C041594:4-nonylphenol