title: Single versus multiple occupancy--effects on toxicity parameters measured on Eisenia fetida in lead nitrate-treated soil.
abstract: The mortality (7 and 14 d), weight change (7 and 14 d), and metal uptake of Eisenia fetida (Savigny, 1826) kept in Pb(NO3)2-treated Kettering loam soil in single- and multiple-occupancy (10 earthworms) test containers were determined. The number of earthworms to dry mass (g) ratio of soil was 1:50 in both sets of test containers. Lead concentrations were in the nominal range of 0 to 10,000 mg Pb/kg soil (mg/kg hereafter). Levels of mortality at a given concentration were statistically identical between the single- and multiple-occupancy tests, except at 1,800 mg/kg, at which significantly (p < or = 0.05) more mortality occurred in the multiple-occupancy tests. Death of individual earthworms in the multiple-occupancy tests did not trigger death of the other earthworms in that soil. The LC50 values (concentration statistically likely to kill 50% of the population) were identical between the multiple- and single-occupancy soils: 2,662 mg/kg (2,598-2,984, 7 d) and 2,589 mg/kg (2,251-3,013, 14 d) for the multiple-occupancy soils and 2,827 mg/kg (2,443-3,168, both 7 and 14 d) for the single-occupancy soils (values in brackets represent the 95% confidence intervals). Data were insufficient to calculate the concentration statistically likely to reduce individual earthworm mass by 50% (EC50), but after 14 d, the decrease in earthworm weight in the 1,800 and 3,000 mg/kg tests was significantly greater in the multiple- than in the single-occupancy soils. At 1,000, 1,800, and 3,000 mg/kg tests, earthworm Pb tissue concentration was significantly (p < or = 0.05) greater in earthworms from the multiple-occupancy soils. The presence of earthworms increased the NH3 content of the soil; earthworm mortality increased NH3 concentrations further but not to toxic levels.
authors.affiliation: Department of Soil Science, School of Human and Environmental Sciences, University of Reading, Whiteknights, Reading RG6 6DW, United Kingdom.
authors.forename: Mark
authors.initials: M
authors.lastname: Currie
authors.forename: Mark E
authors.initials: ME
authors.lastname: Hodson
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Arnold
authors.forename: Caroline J
authors.initials: CJ
authors.lastname: Langdon
mesh_terms: D000818:Animals; D004463:Ecology / Q000379:methods; D007854:Lead / Q000633:toxicity*; D009566:Nitrates / Q000633:toxicity*; D009835:Oligochaeta / Q000187:drug effects*; D011156:Population Density; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000633:toxicity*; D018675:Toxicity Tests / Q000379:methods
chemical_list: D009566:Nitrates; D012987:Soil; D012989:Soil Pollutants; D007854:Lead; C017461:lead nitrate