title: Bioavailability of the organophosphorous insecticide chlorpyrifos to the suspension-feeding bivalve, Mercenaria mercenaria, following exposure to dissolved and particulate matter.
abstract: Under estuarine conditions, hydrophobic pesticides undergo physical/chemical partitioning into dissolved and particulate fractions of sediments. Our experimental study using 14C-chlorpyrifos (14C-CHPY) showed that sorptive associations of this common insecticide with particulate (>0.2 microm) and dissolved fractions (<0.2 microm) of sediments strongly influenced uptake, tissue absorption, and elimination in the estuarine bivalve Mercenaria mercenaria. Bivalves were fed algae mixed with particulate and dissolved fractions of 14C-CHPY-contaminated estuarine sediment particles, components of estuarine sediments (silica, humic acids), and a naturally occurring food source (phytoplankton) to quantify relative uptake, tissue absorption efficiencies, and elimination of 14C-CHPY. Measurements of 14C-CHPY tissue absorption efficiencies (AE%) indicated that particle source qualities influenced much of the insecticide bioavailability. Mean tissue AE% of 14C-CHPY associated with different particulate fractions ranged from 23 to 31%, while uptake from the dissolved/colloidal forms resulted in low (7-17%) AE%. Our data indicated that 14C-CHPY is more likely to bioaccumulate through ingestion of contaminated particulate material than through filtration/ingestion of dissolved/colloidal material. The high selectivity and digestibility of algae particles by M. mercenaria, a potentially ingested food source, may play an important role in the bioavailability of chlorpyrifos in this animal.
authors.affiliation: Department of Environmental Health Sciences, University of South Carolina, Columbia, South Carolina 29208, USA. acbejara@mailbox.sc.edu
authors.forename: Adriana C
authors.initials: AC
authors.lastname: Bejarano
authors.forename: Anneli
authors.initials: A
authors.lastname: Widenfalk
authors.forename: Alan W
authors.initials: AW
authors.lastname: Decho
authors.forename: G Thomas
authors.initials: GT
authors.lastname: Chandler
mesh_terms: D000818:Animals; D001682:Biological Availability; D049872:Bivalvia / Q000502:physiology*; D002250:Carbon Radioisotopes / Q000493:pharmacokinetics; D004390:Chlorpyrifos / Q000493:pharmacokinetics* / Q000633:toxicity; D056890:Eukaryota / Q000737:chemistry; D005247:Feeding Behavior; D019015:Geologic Sediments / Q000737:chemistry*; D007306:Insecticides / Q000493:pharmacokinetics* / Q000633:toxicity; D010316:Particle Size; D014018:Tissue Distribution
chemical_list: D002250:Carbon Radioisotopes; D007306:Insecticides; D004390:Chlorpyrifos