Distribution and bioavailability of mercury in size-fractioned atmospheric particles around an ultra-low emission power plant in Southwest China.

Ultra-low emission (ULE) technology retrofits significantly impact the particulate-bound mercury (Hg) emissions from coal-fired power plants (CFPPs); however, the distribution and bioavailability of Hg in size-fractioned particulate matter (PM) around the ULE-retrofitted CFPPs are less understood. Here, total Hg and its chemical speciation in TSP (total suspended particles), PM10 (aerodynamic particle diameter ≤ 10 µm) and PM2.5 (aerodynamic particle diameter ≤ 2.5 µm) around a ULE-retrofitted CFPP in Guizhou Province were quantified. Atmospheric PM2.5 concentration was higher around this ULE-retrofitted CFPP than that in the intra-regional urban cities, and it had higher mass Hg concentration than other size-fractioned PM. Total Hg concentrations in PM had multifarious sources including CFPP, vehicle exhaust and biomass combustion, while they were significantly higher in autumn and winter than those in other seasons (P < 0.05). Regardless of particulate size, atmospheric PM-bound Hg had lower residual fractions (< 21%) while higher HCl-soluble fractions (> 40%). Mass concentrations of exchangeable, HCl-soluble, elemental, and residual Hg in PM2.5 were higher than those in other size-fractioned PM, and were markedly elevated in autumn and winter (P < 0.05). In PM2.5, HCl-soluble Hg presented a significantly positive relationship with elemental Hg (P < 0.05), while residual Hg showed the significantly positive relationships with HCl-soluble Hg and elemental Hg (P < 0.01). Overall, these results suggested that atmospheric PM-bound Hg around the ULE-retrofitted CFPP tends to accumulate in finer PM, and has higher bioavailable fractions, while has potential transformation between chemical speciation.

[Screening of mixed crop disease-resistant bacterial inoculants from N2-fixing and P-solubilzing bacterial isolates].

In this paper, a total of 22 bacterial isolates capable of fixing nitrogen and/or solubilizing phosphorus were inoculated, and mixed incubated in 15 liquid media. The isolates were obtained from soil with selective media, and not purified. After grown for 48 hours, the mixed cultures were continuously inoculated to the same media, and then incubated under the same conditions. The procedures were repeated for 12 times, and 15 stable bacterial mixtures (SBM) were obtained. Each SBM was purified, which contained two or three bacterial species. Agar plate bacteriostasis test showed that 6 mixed cultures of the SBM exhibited significant inhibition effects to one or more plant pathogens of Verticillium dahliae, Rhizoctonia solani, and Pseudomonas syringae. It was found that C7 and C15 were the two SBM with most obvious antibiological effect. SMB C15 had the ability of nitrogen fixation, and C4, C5 C7, C9, C14 and C15 showed the ability of phosphorus solubilization. These results suggested a possible approach to develop stable, synergistic, and multi-functional antibiological agents.