Eco-toxicological bioassay of atmospheric fine particulate matter (PM2.5) with Photobacterium Phosphoreum T3.

A bioluminescent bacterium, Photobacterium phosphoreum T3 (PPT3), was used as a bio-indicator for the atmospheric fine particulate matter (PM2.5) to determine the eco-toxicity of PM2.5. The PM2.5 contains toxic chemicals, which reduce light output. The PM2.5 samples were collected in the period from March 2014 to January 2015 in Nanjing and analyzed for the chemical composition versus their eco-toxicity. The eco-toxicological responses of each toxicant were detected in PM2.5 samples with PPT3. The dose-response curves obtained were verified using the Weibull fitting function. According to the measured EC50 values (EC50, the concentration of a toxicant that inhibits 50% of the bioluminescence), the toxicity sequence was: B[a]P>hexa-PCB>tetra-PCB>tri-PCB>Pb(2+)>DEHP>Cu(2+)>DBP>BDE209>Zn(2+)>DMP>DEP, where B[a]P is benzo(a)pyrene, PCB is polychlorinated biphenyl, DEHP is diethylhexyl phthalate, DBP is dibutyl phthalate, BDE209 is decabromodiphenyl ether, DMP is dimethyl phthalate, and DEP is diethyl phthalate. All the PM2.5 samples analyzed proved to be weak toxic for PPT3. The toxicity of PM2.5 was assessed by the dose-addition of organic species and heavy metallic elements existing in PM2.5 with PPT3. The bioluminescence test showed that the metals and organics detected in PM2.5 promoted PM2.5 toxicity. The total detectable organics (denoted by ΣOrs) exhibited slightly higher toxicity than the total metals (denoted by ΣMs). In contrast, the sum of water-soluble ions (denoted by ΣIons) was beneficial to PPT3. The PM2.5 toxicity increased as the PM2.5 trapped more organics or metallic elements from the industrial or densely populated urban areas, where the PM2.5 had a high inhibition rate of bioluminescence for PPT3 in contrast to the residential PM2.5 samples, where the minimum inhibition rate was observed. The toxicity of PM2.5 samples varied with the mass concentrations, chemical constituents, and sampling locations. The chemicals in PM2.5, especially organic species and metallic elements, affected its eco-toxicity. These data provided good understanding of the atmospheric PM2.5 pollution in the large portion of the East China.