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.

Soil acidification increases metal extractability and bioavailability in old orchard soils of Northeast Jiaodong Peninsula in China

“…Finally, acidification did not significantly influence the solid phase speciation of Cu and Pb as they were only to a small extent bound to carbonates and Fe or Mn oxides in the examined soils. The concentrations of Cu and Pb accumulated by E. fetida in this experiment are comparable to those reported by other studies using soils containing similar concentrations of aged metals (Gaw et al, 2012). The significant relationships observed between earthworm and soil concentrations of Cu (p < 0.001) and Pb (p < 0.01; Table 5) were consistent with correlations previously reported for E. fetida in laboratory exposure assays with metalcontaminated field soils (Grelle and Descamps, 1998;Bleeker and van Gestel, 2007).…”

“…The order of uptake of metals and the magnitude of the BAFs (Table 4) were in agreement with the results recently reported for earthworms exposed to orchards soils contaminated by metals as a result of historical agrichemical applications (Gaw et al, 2012). The BAFs demonstrated marked differences in accumulation of metals in subsurface soil of the aged orchards and vineyard, as evidenced by the highest BAFs, with BAFs exceeding 1 for Cu, Zn and Cd (Table 4).…”

Subcellular partitioning of metals in Aporrectodea caliginosa along a gradient of metal exposure in 31 field-contaminated soils

“…2 shows elevated individual values (outliers) for earthworms exposed to several smelter-contaminated soils, but no clear pattern could be distinguished. In the literature, internal Cd concentrations in A. caliginosa exposed or living in soils containing less than 1 μg/g total Cd ranged from 4 to 36 μg/g consistently with the range reported here (4-24 μg/g) (Nannoni et al, 2011;Gaw et al, 2012;Łaszczyca et al, 2004;Morgan, 1998, 1999). Several studies showed that earthworms can accumulate high amounts of Cd after short term exposure to high soil Cd concentrations (e.g.…”

Persistence and Changes in Bioavailability of Dieldrin, DDE, and Heptachlor Epoxide in Earthworms Over 45 Years

“…Alexander (2000) argued that because regulatory agencies do not take aging into account, toxic exposures are being over estimated in assessments and he cited his laboratory studies on earthworms in aged soils in support of his argument (Morrison et al 2000;Kelsey et al 2005). In contrast, Gaw et al (2012), studying the accumulation of DDE in Aporrectodea caliginosa in aged horticultural soils under laboratory conditions, concluded that DDE remains biologically available to earthworms and to animals that prey on earthworms. Our field study documents the actual decrease in insecticide residues over 45 years.…”