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Differences in phytotoxicity and dissipation between ionized and nonionized oil sands naphthenic acids in wetland plants
Author(s) -
Armstrong Sarah A.,
Headley John V.,
Peru Kerry M.,
Germida James J.
Publication year - 2009
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/09-059.1
Subject(s) - environmental chemistry , daphnia magna , naphthenic acid , oil sands , extraction (chemistry) , chemistry , phytotoxicity , toxicity , botany , biology , organic chemistry , materials science , corrosion , asphalt , composite material
Naphthenic acids (NAs) are composed of alkyl‐subst ituted acyclic and cycloaliphatic carboxylic acids and, because they are acutely toxic to fish, are of toxicological concern. During the caustic hot‐water extraction of oil from the bitumen in oil sands deposits, NAs become concentrated in the resulting tailings pond water. The present study investigated if dissipation of NAs occurs in the presence of hydroponically grown emergent macrophytes ( Typha latifolia, Phragmites australis , and Scirpus acutus ) to determine the potential for phytoremediation of these compounds. Plants were grown with oil sands NAs ( p K a ∼ 5‐6) in medium at p H 7.8 (predominantly ionized NAs) and p H 5.0 (predominantly nonionized NAs) to determine if, by altering their chemical form, NAs may be more accessible to plants and, thus, undergo increased dissipation. Whereas the oil sands NA mixture in its nonionized form was more toxic to wetland plants than its ionized form, neither form appeared to be sequestered by wetland plants. The present study demonstrated that plants may selectively enhance the dissipation of individual nonionized NA compounds, which contributes to toxicity reduction but does not translate into detectable total NA dissipation within experimental error and natural variation. Plants were able to reduce the toxicity of a NA system over 30 d, increasing the median lethal concentration (LC50; % of hydroponic solution) of the medium for Daphnia magna by 23.3% ± 8.1% (mean ± standard error; nonionized NAs) and 37.0% ± 2.7% (ionized NAs) as determined by acute toxicity bioassays. This reduction in toxicity was 7.3% ± 2.6% (nonionized NAs) and 45.0% ± 6.8% (ionized NAs) greater than that in unplanted systems.