title: Amelioration of the photo-induced toxicity of polycyclic aromatic hydrocarbons by a commercial humic acid.
abstract: The ability of a commercial (Aldrich Chemical Co.) humic acid (AHA) to ameliorate the photo-induced toxicity of polycyclic aromatic hydrocarbons (PAHs) was examined using Lemna gibba L. (G3). Plants were exposed to anthracene and benzo(a)pyrene both with and without AHA and grown under visible light as well as lighting that simulates relative abundances of UV-A and UV-B in natural sunlight (SSR). Modest additions of 1.6 mg.L-1 AHA were sufficient to ameliorate the photo-induced toxicity of 2 mg.L-1 anthracene by improving growth rates to nearly 50% of controls and inducing minor recovery from complete chlorosis in the most highly affected plants. Benzo(a)pyrene induced minor, but significant, chlorosis under SSR, and AHA additions always increased growth rate and chlorophyll content, although to less of a degree than anthracene toxicity under SSR. The protective effects of AHA on anthracene toxicity increased linearly with increases in AHA concentrations up to 6.2 mg.L-1. Slopes of these relationships changed in the presence of UV light relative to visible light treatments; thus UV changed the extent to which AHA mediates PAH toxicity. However, the net effect was still for AHA to ameliorate PAH photo-induced toxicity even though UV has the potential to photooxidize AHA and enhance the production of potentially toxic reactive oxygen species from AHA photosensitization.
authors.affiliation: Department of Biology, University of Waterloo, Ontario, Canada. gensemer@bio.bu.edu
authors.forename: R W
authors.initials: RW
authors.lastname: Gensemer
authors.forename: D G
authors.initials: DG
authors.lastname: Dixon
authors.forename: B M
authors.initials: BM
authors.lastname: Greenberg
mesh_terms: D000873:Anthracenes / Q000633:toxicity*; D001564:Benzo(a)pyrene / Q000633:toxicity*; D018533:Biomass; D002614:Chelating Agents / Q000494:pharmacology*; D002734:Chlorophyll / Q000096:biosynthesis / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000633:toxicity*; D006812:Humic Substances / Q000494:pharmacology*; D019684:Magnoliopsida / Q000187:drug effects*; D018515:Plant Leaves / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D013472:Sunlight / Q000009:adverse effects; D014466:Ultraviolet Rays / Q000009:adverse effects
chemical_list: D000873:Anthracenes; D002614:Chelating Agents; D004785:Environmental Pollutants; D006812:Humic Substances; D002734:Chlorophyll; D001564:Benzo(a)pyrene; C034020:anthracene