Simultaneous removal of Cd (II), Ni (II), and Pb (II) from water by a submerged macrophyte pondweed (Potamogeton malaianus).

The current work investigated the potential of submerged macrophyte pondweed (Potamogeton malaianus) in treating cadmium, nickel, and lead-contaminated water through phytoremediation. The adsorption for the three metal ions occurred rapidly within 2 h and attained dynamic equilibrium in no more than 72 h. The removal efficiencies of Cd (II), Ni (II), and Pb (II) were high, passing 94% in both single- and multi-metal systems. The kinetic adsorption curves of Cd (II), Ni (II), and Pb (II) were fitted well by both pseudo-first-order and pseudo-second-order kinetics (R2 = 0.9875-0.9995). The equilibrium adsorption capacities of Cd (II), Ni (II), and Pb (II) for P. malaianus were 6.29-6.97 mg kg-1 . In plants, the higher concentration of each metal ions was accumulated in leaves (12.44-38.15 mg kg-1 ) than in roots (10.32-26.10 mg kg-1 ). The chlorophyll contents increased from 0.69 to 0.89-1.00 mg g-1 under the treatment of Cd (II), Ni (II), and Pb (II), whereas the chlorophyll a/b ratio was kept constant. There was no significant difference between single- and multi-metal systems. FT-IR spectra showed that COH and C═N might be involved in the adsorption of Cd (II), Ni (II), and Pb (II). This study demonstrated that P. malaianus could be a suitable submerged macrophyte for the simultaneous removal of Cd (II), Ni (II), and Pb (II) from water.

Optimization of the preparation of fungal-algal pellets for use in the remediation of arsenic-contaminated water.

This study was conducted to optimize the preparation of fungal-algal pellets for use in the removal of arsenite (As(III)) and arsenate (As(V)) from water. Three parameters, i.e., glucose concentration, shaking speed, and pH, were investigated to show their effects on the immobilization efficiency of algal biomass attached to fungal mycelial pellets. The highest immobilization efficiency was achieved at 5 g glucose L-1, 140 rpm, and pH 7. Furthermore, the fungal-algal pellets with different initial algal biomass were tested regarding the stability and their capability of removing As(III) and As(V). The fungal-algal pellets could not keep good stability when the initial algal biomass was more than 4.8 × 107 cells mL-1. The highest removal rates of As(III) and As(V) were obtained by the fungal-algal pellets with initial algal biomass of 4.8 × 107 cells mL-1, and the removal rate of As(V) was much higher compared with that of As(III). Similar trends were observed for the concentrations of total arsenic as well as As(III) and As(V) in fungal-algal pellets. The fungal-algal pellets with initial algal biomass of 4.8 × 107 cells mL-1 showed a significant potential for removing As(V) from water, and microalgae might play a key role in the absorption and transformation of inorganic arsenic. Adsorption kinetics studies suggested that the adsorption of As(V) onto fungal-algal pellets followed the pseudo-second-order kinetic model, and the pseudo-first-order kinetic model was more appropriate for describing the adsorption of As(III).

Bioaccessibility of arsenic from gastropod along the Xiangjiang River: Assessing human health risks using an in vitro digestion model.

The bioaccessibility of total arsenic (tAs) and arsenic species in Bellamya aeruginosa collected from Xiangjiang River was evaluated using an in vitro digestion model, to assess the potential health risks to local residents. The tAs concentrations in gastropod samples ranged from 1.98 to 6.33 mg kg-1 (mean 3.79 ± 1.60 mg kg-1). Five arsenic species including arsenite [As(III)], arsenate [As(V)], dimethylarsinic acid (DMA), arsenobetaine (AsB), and arsenocholine (AsC) were detected. Inorganic arsenic (iAs) concentrations, which were about a half of organic arsenic (oAs), were higher than the maximum permissible limit (≤0.50 mg kg-1 in aquatic products). Bioaccessible concentrations of tAs in digestive juices were found to be decreased in the order: intestinal phase > gastric phase > salivary phase. As(III) and AsC were the predominant species, but AsB was not detectable in all digestive juices. Bioaccessible iAs concentrations, which were close to the level of bioaccessible oAs, were not significantly different among three digestive juices, but also above 0.50 mg kg-1. Accordingly, bioaccessibility of tAs was highest in intestinal phase (48%), then in gastric phase (40%), and lowest in salivary phase (33%). Bioaccessibility of As(III) was close to 100%, and bioaccessibility of iAs was much higher than that of oAs. The mean values of target hazard quotient (THQ) and bioaccessible THQ were 0.80 and 0.70, respectively. The probability of experiencing non-carcinogenic effects was reduced to 18% down from 22% as considering iAs bioaccessibility. The mean values of carcinogenic risk (CR) and bioaccessible CR were higher than the acceptable value (1 × 10-4). Gastropod consumption from sampling sites may cause a potential carcinogenic risk.