Search

Predicting the crucial effect of single metal pollutants against the aquatic ecosystem has been highly debatable for decades. However, dealing with complex metal mixtures management in toxicological studies creates a challenge, as heavy metals may evoke greater toxicity on interactions with other constituents rather than individually low acting concentrations. Moreover, the toxicity mechanisms are different between short term and long term exposure of the metal toxicant. In this study, acute and chronic toxicity based on luminescence inhibition assay using newly isolated Photobacterium sp.NAA-MIE as the indicator are presented. Photobacterium sp.NAA-MIE was exposed to the mixture at a predetermined ratio of 1:1. TU (Toxicity Unit) and MTI (Mixture Toxic Index) approach presented the mixture toxicity of Hg2+ + Ag+, Hg2+ + Cu2+, Ag+ + Cu2+, Hg2+ + Ag+ + Cu2+, and Cd2+ + Cu2+ showed antagonistic effect over acute and chronic test. Binary mixture of Cu2+ + Zn2+ was observed to show additive effect at acute test and antagonistic effect at chronic test while mixture of Ni2+ + Zn2+ showing antagonistic effect during acute test and synergistic effect during chronic test. Thus, the strain is suitable and their use as bioassay to predict the risk assessment of heavy metal under acute toxicity without abandoning the advantage of chronic toxicity extrapolation.

Ultraviolet (UV) photodegradation is increasingly applied to control volatile organic compounds (VOCs) due to its degradation capabilities for recalcitrant compounds. However, sometimes the UV photodegradation products are also toxic and can affect human health. Here, 10 VOCs at 150~200 ppm in air were treated using a laboratory-scale UV reactor with 185/254 nm irradiation, and the biotoxicity of their off-gas was studied by investigating their off-gas absorption solutions. The CO2 increase and VOC decrease were 39~128 ppm and 0~42 ppm, respectively, indicating that the VOCs and their products were mineralized in off-gas absorption solutions. The total organic carbon (TOC) of the absorption solutions are 4~20 mg∙L&minus, 1. Luminescent bacteria and Daphnia magna were used to detect the acute toxicity, and an umu assay was used to determine the genotoxic potential. Trichloroethylene showed a highest toxicity to luminescent bacteria, while chlorobenzene had the lowest toxicity. Water-soluble UV photodegradation products for styrene are very toxic to Daphnia magna. In the umu assay, the genotoxicities of off-gas absorption solutions of trichloroethylene, methylbenzene, ethyl acetate, butyl alcohol, and styrene were 51.26, 77.80, 86.89, 97.20, and 273.62 mg (4-NQO)&middot, L&minus, 1 respectively. In addition, the analysis of the genotoxicity/TOC and intermediates products indicated that the off-gas absorption solutions of styrene, trichloroethylene, and butyl alcohol contain many highly toxic substances.

Four different manufactured surface-coated silver nanoparticles (AgNPs) with coating of citrate, tannic acid, polyethylene glycol, and branched polyethylenimine were used in this study. The toxicity of surface-coated AgNPs was evaluated by a luminous microbial array for toxicity risk assessment (LumiMARA) using multi-species of luminescent bacteria. The salt stability of four different AgNPs was measured by UV absorbance at 400 nm wavelength, and different surface-charged AgNPs in combination with bacteria were observed using scanning electron microscopy (SEM). Both branched polyethylenimine (BPEI)-AgNPs and polyethylene glycol (PEG)-AgNPs were shown to be stable with 2% NaCl (non-aggregation), whereas both citrate (Cit)-AgNPs and tannic acid (Tan)-AgNPs rapidly aggregated in 2% NaCl solution. The values of the 50% effective concentration (EC50) for BPEI-AgNPs in marine bacteria strains (1.57 to 5.19 mg/L) were lower than those for the other surface-coated AgNPs (i.e., Cit-AgNPs, Tan-AgNPs, and PEG-AgNPs). It appears that the toxicity of AgNPs could be activated by the interaction of positively charged AgNPs with the negatively charged bacterial cell wall from the results of LumiMARA. LumiMARA for toxicity screening has advantageous compared to a single-species bioassay and is applicable for environmental samples as displaying ranges of assessment results.

Biogas slurry has become a serious pollution problem and anaerobic digestion is widely applied to pig manure treatment for environmental protection and energy recovery. To evaluate environmental risk of the emission of biogas slurry, luminescent bacteria (Vibrio fischeri), larvae and embryos of zebrafish (Danio rerio) were used to detect the acute and development toxicity of digested and post-treated slurry. Then the ability of treatment process was evaluated. The results showed that digested slurry displayed strong toxicity to both zebrafish and luminescent bacteria, while the EC50 for luminescent bacteria and the LC50 for larvae were only 6.81% (v/v) and 1.95% (v/v) respectively, and embryonic development was inhibited at just 1% (v/v). Slurry still maintained a high level of toxicity although it had been treated by membrane bioreactor (MBR), while the LC50 of larvae was 75.23% (v/v) and there was a little effect on the development of embryos and V. fischeri, the results also revealed that the zebrafish larvae are more sensitive than embryos and luminescent bacteria to pig slurry. Finally, we also found the toxicity removal rate was higher than 90% after the treatment of MBR according to toxicity tests. In conclusion, further treatment should be used in pig slurry disposal or reused of final effluent.