The influence of phototrophic benthic biofilms on Cd, Cu, Ni, and Pb transport in permeable sediments

Abstract

The effect of phototrophic biofilm activity on advective transport of cadmium (Cd), copper (Cu), nickel (Ni), and lead (Pb) in sandy sediments was examined using percolated columns. Cd and Ni in the effluent exhibited clear diel cycles in biofilmcontaining columns, with concentrations at the end of dark periods exceeding those during illumination by up to 4.5-and 10-fold for Ni and Cd, respectively. Similar cycles were not observed for Pb or Cu. Breakthrough of the latter metals was greatly retarded and incomplete relative to Cd and Ni, and trends in biofilm treatments did not differ greatly from those in control columns. Inhibition of photosystem II by DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) proved that diel cycles of Cd and Ni were controlled by oxygenic photosynthesis, and microsensor measurements showed that metal cycles closely matched metabolic activity-driven pH variations. The sorption edge pH for the sand/biofilm substrate followed the order Ni [ Cd [ Cu [ Pb, and for Ni and Cd, was within the pH 7-10 range observed in the biofilmcontaining column. Adsorption dynamics over the light periods matched pH increases, but desorption during dark periods was incomplete and slower than the rate of change of pH. Over a diel cycle, desorption was less than adsorption, resulting in net binding of dissolved metals due to the biofilm metabolic activity. Extraction with selective reagents indicated that the adsorbed metals were readily exchangeable, and potentially bioavailable. Thus, phototrophic benthic biofilms can control the transport of some metals across the sand-water interface, and processes in this very thin surficial layer should be considered when evaluating chemical fluxes in permeable sediments.

The degradation of linear alkylbenzene sulfonate (LAS) in the presence of light and natural biofilms: The important role of photosynthesis

“…32 • C under illumination and decreased to ambient temperature at about 25 • C in dark for experiment set 1-4, and almost remained unchanged for set 5. For pH (initial pH ≈ 7.9), it was almost constant for experiment set 1, and varied with illumination in a similar manner to that of temperature for experiment set 2 (up to near 8.7 and down to around 6.4), as a result of photosynthesis and respiration [3,6,30]. The pH decreased slightly for the other 3 sets of experiment, down to about 6.6-6.9, which should be due to the buffering effect of biofilms on pH [22].…”

“…Studies have shown that the diurnal rhythm of photosynthesis and respiration of aquatic organisms is the main reason for the increase of pH and dissolved oxygen (DO) in daytime and decrease at night, coupled with temperature variation, in natural waters [1][2][3][4][5]. These fluctuations affect the behavior of trace metals in aquatic systems significantly: the concentrations of trace metals in water usually decrease under illumination and increase in dark, which have been verified in both laboratory and field studies [1,2,[5][6][7]. The speciation of trace metals is also affected [1,8].…”

“…Several studies have also showed that the degradation of LAS in natural waters is rather slow and inefficient, especially the adsorbed LAS [14,15,[17][18][19]. Natural biofilms, consisting of algae, bacterium and other microorganisms and associated minerals, exist widely on surfaces of all kinds of solid materials in natural waters, and play a significant role in determining the characteristics of the microenvironment [2,6,8,20]. …”

Effect of VariablepCO2on Ca2+Removal and Potential Calcification of Cyanobacterial Biofilms —An Experimental Microsensor Study

“…Thus binding and release of Ca 2C ions can occur at a wide range of pH values. The effect of pH may be allosteric, as the pH dependance of the ion-exchange behavior of biomass depends on the ion type (see Beck et al 2011). Alternatively, the observed Ca 2C release might result from heterotrophic exopolymer digestion where decarboxylation liberating previously complexed Ca 2C .…”

Influence of biofilms on heavy metal immobilization in sustainable urban drainage systems (SuDS)

“…In comparison, the heavy metal breakthrough experiments employed a 5ppm pulse of either Cu solution or a mixture (M+) of Cu, Pb, and Zn (Table 1) dissolved in SuDS pond water to assess permanent loss within the columns. These metals are the most common heavy metal pollutants in the road runoff [21][22][23][24] specific to gravel filter drains, with Cu typically the highest in concentration. These multi-metal M+ solutions were prepared by dissolving metal salts of Copper(II) nitrate (Cu(NO 3 ) 2 · 3H 2 O), Lead(II) nitrate (Pb(NO 3 ) 2 ) and Zinc nitrate (Zn(NO 3 ) 2 · 6H 2 O) (Sigma-Aldrich) in deionized water to achieve a stock solution of 1000ppm.…”