title: Comparison of earthworm and chemical assays of the bioavailability of aged 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene, 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane, and heavy metals in orchard soils.
abstract: Orchard soils can contain elevated concentrations of 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE), 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p'-DDT), and heavy metals as a result of historical agrichemical applications. The bioavailability of p,p'-DDE, p,p'-DDT, As, Cd, Cu, and Pb from five field-aged New Zealand orchards and three grazing soils was assessed by using a 28-d bioassay with Aporrectodea caliginosa and chemical assays. Significant relationships were found between total soil and earthworm tissue concentrations for p,p'-DDE (p < 0.001), p,p'-DDT (p < 0.001), Cu (p < 0.001), and Pb (p < 0.01). Two neutral salt solutions, 0.01 M CaCl(2) and 1 M NH(4)NO(3), were used as surrogate measures of the bioavailability of heavy metals. Copper was the only heavy metal for which significant correlations were found between neutral-salt-extractable and earthworm tissue concentrations (p < 0.001). Up to 28% of the aged DDT residues were released from the soils by Tenax over a 24-h extraction period. Significant relationships (p < 0.01) between the Tenax-extractable and earthworm tissue concentrations for p,p'-DDE and p,p'-DDT showed that Tenax provides a good surrogate measure of the bioavailability of these compounds to A. caliginosa. Surprisingly, there was a similarly significant relationship (p < 0.001) between the total soil and earthworm tissue concentrations for p,p'-DDE and p,p'-DDT, suggesting that total soil concentrations alone were sufficient to predict uptake by A. caliginosa. These results demonstrate that the aged agrichemical residues in orchard soils, and particularly p,p'-DDE and p,p'-DDT, remain highly bioavailable to A. caliginosa despite decades of weathering and continue to present an environmental risk.
authors.affiliation: The University of Waikato, Hamilton, New Zealand. sally.gaw@canterbury.ac.nz
authors.forename: Sally
authors.initials: S
authors.lastname: Gaw
authors.forename: Grant
authors.initials: G
authors.lastname: Northcott
authors.forename: Nick
authors.initials: N
authors.lastname: Kim
authors.forename: Alistair
authors.initials: A
authors.lastname: Wilkins
authors.forename: Joanne
authors.initials: J
authors.lastname: Jensen
mesh_terms: D000383:Agriculture; D000818:Animals; D003634:DDT / Q000032:analysis* / Q000378:metabolism; D003633:Dichlorodiphenyl Dichloroethylene / Q000032:analysis* / Q000378:metabolism; D004784:Environmental Monitoring; D019216:Metals, Heavy / Q000032:analysis* / Q000378:metabolism; D009520:New Zealand; D009835:Oligochaeta / Q000378:metabolism*; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism*
chemical_list: D019216:Metals, Heavy; D012987:Soil; D012989:Soil Pollutants; D003633:Dichlorodiphenyl Dichloroethylene; D003634:DDT