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| Titel |
Zn transport and fate in sand columns containing microbial biofilms |
| VerfasserIn |
Suyin Yang, Bryne Ngwenya, Ian Butler, Stephen Elphick |
| 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 |
250047756
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| Zusammenfassung |
| Both biofilms and trace metals are ubiquitous in subsurface and aquatic system. Their
interactions are of great interest. The growth of biofilms results in the decrease of porosity,
hydraulic conductivity and flow rate and therefore retards metal transport in porous
media. Biofilms mainly consist of extracellular polymeric substance (EPS), immobile
bacteria and mobile bacteria. EPS compounds and bacteria cell wall contain acidic
functional groups that when deprotonated, can bind significant concentrations of metal
cations. With the migration of mobile bacteria, the transport of metal adsorbed
to bacteria might be facilitated. Metals, in turn, affect microbial growth both as
nutrients and toxins. The toxicity may increase the detachment of bacteria leading to
facilitated metal transport or increasing the EPS production resulting in retardation of
metal transport. In this study, we aim to investigate the interactions between metal
and biofilms, especially, the effect of biofilms on zinc transport and fate in porous
media.
Batch experiments were performed to assess Zn adsorption onto bacterium strain Pantoea
Agglomerans. Voltammetry with solid-state gold-amalgam microelectrodes was tested and
used to analyze labile zinc in cell suspensions. Then, polycarbonate column packed with sand
was set up to test the effect of biofilm on Zn transport and the impact of Zn on biofilm
growth. P. agglomerans cells were inoculated to develop a biofilm for one week with the
supply of nutrient broth medium. Hydraulic conductivities were continuously measured while
cell viable was monitored from column outflow by colony forming units. Inductively coupled
plasma atomic emission spectrometry was used to quantify total zinc in solution and
biofilms.
Our batch experiments showed adsorption of Zn in bacteria and suggest that
voltammetry with solid-state electrodes is suitable to quickly and effectively quantify
labile zinc in solution and consequently to derive surface complexation constants
for metals and bacterial surfaces. The breakthrough curves in our continuous flow
column experiments show both facilitated and retarded Zn transport within one
week of biofilm growth, dependent upon the aqueous Zn concentration. With higher
concentration of Zn, the mobility of the detached bacteria and EPS enhanced Zn
transport, due to metal toxicity. And after a 10 day period of running with Zn in
the column, most of Zn accumulated in the bottom of the column where higher
biofilm growth was detected. The results indicate a flexible modelling approach
is necessary for quantifying metal contaminant transport in microbial biofilms. |
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