title: Toxicity in lead salt spiked soils to plants, invertebrates and microbial processes: Unraveling effects of acidification, salt stress and ageing reactions.
abstract: The fate and effects of toxic trace metals in soil freshly spiked soluble metal salts do not mimic those of metals in the field. This study was set up to test the magnitude of effects of salinity, acidification, and ageing on toxicity of lead (Pb) to plants, invertebrates and soil microbial processes. Three soils were spiked with Pb2+ salts up to a concentration of 8000 mg Pb/kg and were tested either after spiking, after soil leaching followed by pH correction, or after a 5-year outdoor ageing period with free drainage followed by pH correction. Soil solution ionic strength exceeded 150 mmol/L in soils tested directly after spiking and this decreased partially after leaching and returned back to background values after 5-year outdoor equilibration. Chronic toxicity to two plants, two invertebrates, and three microbial endpoints was consistently found in all spiked soils that were not leached. This toxicity significantly decreased or became absent after 5 years of ageing in 19 of the 20 toxicity tests by a factor 8 (median factor; range: 1.4->50), measured by the factor increase of total soil Pb dose required to induce 10% inhibition. The toxicity of Pb in leached soils was intermediate between the other two treatments. The lowest detectable chronic thresholds (EC10) in aged soils ranged 350-5300 mg Pb/kg. Correlation analysis, including data of Pb2+ speciation in soil solution, suggests that reduced ionic strength rather than acidification or true ageing is the main factor explaining the soil treatment effects after spiking. It is suggested that future toxicity studies should test fine PbO powder as a relevant source for Pb in soils to exclude the confounding salt effects.
authors.affiliation: Division Soil and Water Management, K.U.Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium. Electronic address: erik.smolders@ees.kuleuven.be.
authors.forename: Erik
authors.initials: E
authors.lastname: Smolders
authors.affiliation: ARCHE consulting, PJ Van Benedenstraat 4, box 203, B-3000 Leuven, Belgium.
authors.forename: Koen
authors.initials: K
authors.lastname: Oorts
authors.affiliation: Division Soil and Water Management, K.U.Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium.
authors.forename: Sofie
authors.initials: S
authors.lastname: Peeters
authors.affiliation: Department of Evolution, Ecology, and Organismal Biology, Ohio State University; 318 W. 12th Ave, Columbus, OH, USA.
authors.forename: Roman
authors.initials: R
authors.lastname: Lanno
authors.affiliation: Veterinary and Agrochemical Research Centre (CODA-CERVA), Leuvensesteenweg 17, B-3080 Tervuren, Belgium.
authors.forename: Karlien
authors.initials: K
authors.lastname: Cheyns
mesh_terms: D000818:Animals; D004784:Environmental Monitoring; D007448:Invertebrates / Q000187:drug effects; D007854:Lead / Q000633:toxicity*; D010944:Plants / Q000187:drug effects; D012492:Salts / Q000633:toxicity*; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000633:toxicity*; D014131:Trace Elements / Q000032:analysis
chemical_list: D012492:Salts; D012987:Soil; D012989:Soil Pollutants; D014131:Trace Elements; D007854:Lead
keywords: Bioavailability; Lead; Phosphorus; Soil toxicity; Spiking