title: Ecological risk assessment of on-site soil washing with iron(III) chloride in cadmium-contaminated paddy field.
abstract: On-site soil washing with iron(III) chloride reduces Cd levels in soil, and thus the human health risks caused by Cd in food. However, it may threaten aquatic organisms when soil washing effluent is discharged to open aquatic systems. Therefore, we conducted trial-scale on-site soil washing and ecological risk assessment in Nagano and Niigata prefectures, Japan. The ecological effect of effluent water was investigated by two methods. The first was bioassay using standard aquatic test organisms. Twice-diluted effluent water from the Nagano site and the original effluent water from the Niigata site had no significant effects on green algae, water flea, caddisfly, and fish. The safe dilution rates were estimated as 20 times and 10 times for the Nagano and Niigata sites, respectively, considering an assessment factor of 10. The second method was probabilistic effect analysis using chemical analysis and the species sensitivity distribution concept. The mixture effects of CaCl(2), Al, Zn, and Mn were considered by applying a response additive model. The safe dilution rates, assessed for a potentially affected fraction of species of 5%, were 7.1 times and 23.6 times for the Nagano and Niigata sites, respectively. The actual dilution rates of effluent water by river water at the Nagano and Niigata sites were 2200-67,000 times and 1300-110,000 times, respectively. These are much larger than the safe dilution rates derived from the two approaches. Consequently, the ecological risk to aquatic organisms of soil washing is evaluated as being below the concern level.
authors.affiliation: National Institute for Agro-Environmental Sciences, Kannondai 3-1-3, Tsukuba, Ibaraki 305-8604, Japan. nagait@affrc.go.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Nagai
authors.forename: Takeshi
authors.initials: T
authors.lastname: Horio
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yokoyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Kamiya
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Takano
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Makino
mesh_terms: D000383:Agriculture; D000818:Animals; D059001:Aquatic Organisms; D002104:Cadmium / Q000032:analysis* / Q000737:chemistry / Q000633:toxicity; D002712:Chlorides / Q000737:chemistry*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005290:Ferric Compounds / Q000737:chemistry*; D007564:Japan; D012275:Oryza; D018570:Risk Assessment; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis* / Q000737:chemistry / Q000633:toxicity
chemical_list: D002712:Chlorides; D005290:Ferric Compounds; D012987:Soil; D012989:Soil Pollutants; D002104:Cadmium