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| Titel |
Removal of trace metals from contaminated street and wetland sediments with a biosurfactant (Saponin) and an artificial surfactant (SDS) |
| VerfasserIn |
Li Huang, Loretta Li, Ken Hall |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250045609
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| Zusammenfassung |
| Trace metals are the most common priority contaminants in urban runoff. Their influx within
watersheds due to urban development affecting water and sediment contamination is an
ongoing concern. Motor vehicle traffic is an important source of copper, lead, manganese and
zinc. Contaminants transported within stormwater discharges are a major cause of
impairment of receiving waters.
The objective of this study is to investigate the effectiveness of two surfactants: (1)
plant-derived saponin, and (2) artificial/synthetic sodium dodecyl sulfate (SDS) to remove
trace metals from contaminated sediments. Sediment samples from a street trap of a busy
suprmarket parking lot (organic matter 75 g/kg) and constructed wetland (organic matter 200
g/kg) were collected in highly urbanized areas of Vancouver, Canada. The trace metals (Cu,
Mn, Pb, Zn) were analyzed for their total concentrations. The sediment samples were
subjected to batch desorption tests to determine the trace metal removal by these two
surfactants. Surfactant concentrations were 200, 2,000, 5,000, 10,000 and 20,000
mg/L; reaction times of 0.5, 1, 2, 6, 12 and 24 h were tested. Exchangeable forms
of trace metals were determined by extraction with 1 M MgCl2 at pH 7 for the
sediment samples before and after surfactant treatment (20,000 mg/L surfactants for 24
h) for their effectiveness in removing the bio-available trace metals. Remediated
sediments of the highest surfactant concentration tested (20,000 mg/L) and reaction time
(24 h) were subjected to three distilled water washings to remove the remaining
surfactants from the sediments and ensure that no surfactant is introduced into the
environment.
The metal removal capacities of saponin and SDS were enhanced as the surfactant
concentration increased from 200 to 20000 mg/L. The surfactants assisted in the effective
removal of the metals with 1 h of desorption, and the removal of metals increased slowly as
the reaction time increased from 1 to 24 h. The maximum removal was 10-20% of the total
trace metals. The removal of the metals by saponin was 5-10% higher than by SDS under the
same washing conditions. Both surfactants are most effective in removing the exchangeable
Zn (40-70%). Saponin removed 50% of the exchangeable Cu, whereas SDS is ineffective in
desorbing exchangeable Cu. Saponin and SDS removed 50% exchangeable Mn from the
wetland sediment, but only 10% from the parking lot street sediment. The surfactant sediment
concentrations after three rinses with distilled water were reduced by 99%. The
residual saponin and SDS were both below the toxicity limits (LC50) for aquatic life. |
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