title: Effect of dissolved humic acid on the Pb bioavailability in soil solution and its consequence on ecological risk.
abstract: Current risk characterization in ecological risk assessment does not consider bioavailability of heavy metals, which highly depends on physicochemical properties of environmental media. This study was set to investigate the effect of humic acid (HA), used as a surrogate of organic matter, on Pb toxicity and the subsequent effect on risk characterization in ecological risk assessment. Pb toxicity was assessed using Microtox(®) in the presence and absence of two different forms of HA, particulate HA (pHA) and dissolved HA (dHA). With increasing contact time, the EC10 values increased (i.e., the toxic effects decreased) and the dissolved Pb concentrations of the filtrates decreased. The high correlation (R = 0.88, p < 0.001) between toxic effects determined using both the mixture and its filtrate as exposure media leads us to conclude that the Pb toxicity highly depends on the soluble fraction. Also, reduced Pb toxicity with increasing dHA concentrations, probably due to formation of Pb-dHA complexes, indicated that Pb toxicity largely comes from free Pb ions. Overall, this study shows the effect of HA on metal toxicity alleviation, and emphasizes the need for incorporating the bioavailable heavy metal concentrations in environmental media as a point of exposure in ecological risk assessment.
authors.affiliation: Department of Civil and Environmental Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, Republic of Korea.
authors.forename: Jinsung
authors.initials: J
authors.lastname: An
authors.affiliation: Department of Environmental Science, Hankuk University of Foreign Studies, 81 Oedae-ro, Mohyeon-myeon, Cheoin-gu, Yongin-si, Gyeonggi-do, Republic of Korea. Electronic address: gracejho@gmail.com.
authors.forename: Eun Hea
authors.initials: EH
authors.lastname: Jho
authors.affiliation: Department of Civil and Environmental Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, Republic of Korea.
authors.forename: Kyoungphile
authors.initials: K
authors.lastname: Nam
mesh_terms: D048908:Aliivibrio fischeri / Q000187:drug effects; D001681:Biological Assay; D055598:Chemical Phenomena; D004463:Ecology; D006812:Humic Substances / Q000032:analysis*; D007854:Lead / Q000032:analysis / Q000737:chemistry / Q000633:toxicity*; D008956:Models, Chemical; D018570:Risk Assessment; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry / Q000633:toxicity*; D012995:Solubility; D018675:Toxicity Tests
chemical_list: D006812:Humic Substances; D012987:Soil; D012989:Soil Pollutants; D007854:Lead
keywords: Bioavailability; Ecological risk assessment; Humic acid; Lead; Toxicity