title: Effect of long-term equilibration on the toxicity of molybdenum to soil organisms.
abstract: To determine if long-term equilibration may alleviate molybdenum toxicity, earthworms, enchytraeids, collembolans and four plant species were exposed to three soils freshly spiked with Na(2)MoO(4).2H(2)O and equilibrated for 6 or 11 months in the field with free drainage. Total Mo concentrations in soil decreased by leaching, most (up to 98%) in sandy soil and less (54-62%) in silty and clayey soils. Changes in residual Mo toxicity with time were inconclusive in sandy soil. In the other two soils, toxicity of residual total Mo was significantly reduced after 11 months equilibration with a median 5.5-fold increase in ED50s. Mo fixation in soil, i.e. the decrease of soil solution Mo concentrations at equivalent residual total soil Mo, was maximally a factor of 2.1 only. This experiment shows natural attenuation of molybdate ecotoxicity under field conditions is related to leaching of excess Mo and other ions as well as to slow ageing reactions.
authors.affiliation: Department of Animal Ecology, Faculty of Earth and Life Science, VU University, Amsterdam, The Netherlands. kees.van.gestel@falw.vu.nl
authors.forename: Cornelis A M
authors.initials: CA
authors.lastname: van Gestel
authors.forename: Steve P
authors.initials: SP
authors.lastname: McGrath
authors.forename: Erik
authors.initials: E
authors.lastname: Smolders
authors.forename: Maria Diez
authors.initials: MD
authors.lastname: Ortiz
authors.forename: Eef
authors.initials: E
authors.lastname: Borgman
authors.forename: Rudo A
authors.initials: RA
authors.lastname: Verweij
authors.forename: Jurgen
authors.initials: J
authors.lastname: Buekers
authors.forename: Koen
authors.initials: K
authors.lastname: Oorts
mesh_terms: D000818:Animals; D001181:Arthropods / Q000187:drug effects*; D008982:Molybdenum / Q000032:analysis / Q000633:toxicity*; D009835:Oligochaeta / Q000187:drug effects*; D010944:Plants / Q000187:drug effects*; D012989:Soil Pollutants / Q000032:analysis / Q000633:toxicity*
chemical_list: D012989:Soil Pollutants; D008982:Molybdenum