The effectiveness of a novel and low-cost adsorbent, iron-modified bamboo charcoal (BC-Fe), for arsenic removal from aqueous systems was evaluated in this study. The BC-Fe was synthesized by loading iron onto bamboo charcoal via soaking in a ferric salt solution. The BC-Fe possessed a porous structure with a surface area of 277.895 m 2 /g. The adsorption characteristics of arsenic onto BC-Fe were further investigated at various pHs, contact times, arsenic concentrations, and adsorbent doses in batch tests. The corresponding optimum equilibrium pH ranges for As(III) and As(V) removal were 4-5 and 3-4, respectively. The equilibrium times for As(III) and As(V) adsorption were 30 and 35.5 h, respectively. The arsenic removal was strongly dependent on the initial adsorbate concentration and adsorbent dosage. The maximum arsenic removal capacities of BC-Fe under the experimental conditions were 7.237 and 19.771 mg/g for As(III) and As(V), respectively.The pseudo-second-order kinetic model and Freundlich isotherm explained the kinetic and equilibrium of both the As(III) and As(V) adsorbent processes, respectively. Based on these results, the BC-Fe developed in this study is a promising material for the treatment of arsenic-contaminated water.

Our previous data have shown that inorganic arsenic concentrations were high in Dianchi Lake, China, where Microcystis blooms often occur. To explore the relationship between arsenic and the growth of Microcystis, the effects of arsenite [As(III)] and arsenate [As(V)] on the growth and toxin production of M. aeruginosa strain FACHB 905 were tested. Results showed that M. aeruginosa FACHB 905 was tolerant to inorganic arsenic and its growth was not inhibited when the concentration of As(III) was below 10 −5 mol L −1 or that of As(V) below 10 −3 mol L −1. Total microcystin production was stimulated in the presence of 10 −7 mol L −1As(III) and the response of this M. aeruginosa strain to As(III) seemed to be a typical inverted U-shaped hormesis. The content increase of microcystin-LR per cell indicated that the toxicity was enhanced as M. aeruginosa FACHB 905 was exposed to As(V). Considering the relatively high concentration of inorganic arsenic in Dianchi Lake (139 μg L −1 in epilimnetic water), the origin of the M. aeruginosa strain, inorganic arsenic favors survival of M. aeruginosa FACHB 905 and may stimulate its microcystin production and cellular toxicity.inorganic arsenic, cyanobacteria, Microcystis aeruginosa, microcystin Citation: Gong Y, Ao H Y, Liu B B, et al. Effects of inorganic arsenic on growth and microcystin production of a Microcystis strain isolated from an algal bloom in Dianchi Lake, China. Chinese Sci Bull, 2011Bull, , 56: 2337Bull, −2342Bull, , doi: 10.1007 Arsenic is a ubiquitous toxic element in aquatic environments and its residence time in freshwater has been estimated at about 50 years [1]. The main arsenic species, including arsenate [As(V)], arsenite [As(III)], monomethylarsonic acid (MMAA), and dimethylarsinic acid (DMAA), have been found to be toxic to phytoplankton at different potencies and different species have different effects [2][3][4][5]. As(III) inhibits the incorporation of carbon into glutamate [2]. As(V) inactivates the phosphate transport system and glucose metabolism, because of its similar structure to phosphate, and is readily co-transported into the cell [5,6]. Methylated species are shown to be less toxic or even non-toxic and, therefore, are regarded as detoxified products of some algae [7,8]. Previous studies indicated that algal sensitivity to inorganic arsenic may be species specific [6,9,10].Microcystis is a dominant cyanobacterium that blooms in the hypertrophic Dianchi Lake, Kunming, China [11]. A previous survey of this lake showed that the inorganic arsenic concentration (arsenate plus arsenite) was 139 μg L −1 in epilimnetic water and 332 mg kg −1 in sediment (data not shown). It is still unclear whether the occurrence of Micro- et al. Chinese Sci Bull August (2011) Vol.56 No.22 cystis blooms in the lake is linked with arsenic abundance, and whether arsenic affects the toxin production of Microcystis species, if the linkage exists. The effects of As(III) and As(V) on growth and toxin production of M. aeruginosa, isolated from a harmful algal bloom, ...

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The extensive use of parabens as preservatives in food and pharmaceuticals and personal care products results in frequent detection of their residuals in aquatic environment. In this work, the adsorption and removal of four parabens (methyl-, ethyl-, propyl-, and butyl-paraben) and two chlorinated methyl-parabens (CMPs) by periphyton were studied. Characteristics of the periphyton were identified to explore the possible relationship between paraben removal and periphyton properties. Results showed that linear adsorption coefficients (K ) vary from 554.4 to 808.6 L kg for the adsorption parabens and CMPs to autoclaved periphyton. The adsorption strength is positively related to the hydrophobicity of these compounds. Removal of parabens from water by periphyton was efficient with half-life (t ) values estimated using first-order kinetic model ranging from 0.49 to 3.29 days, but CMPs were more persistent with t ranging from 1.15 to 25.57 days, and t increased with the chlorination degree. Higher incubation temperature accelerated the removal of all tested compounds, while a better removal of CMPs was observed in dark condition. Analysis of periphyton properties suggests that bacteria played a more important role in the removal of CMPs, but no specific relationship between periphyton properties and paraben removal ability can be established.

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