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The volume concentration of peroxyacetyl nitrate (PAN) and O 3 in the atmosphere were measured at the Tianjin Meteorological Tower in summer 2017 by using the online instrument with meteorological parameters and back trajectory analysis to analyze the delivery characteristics of PAN and O 3 . The average volume concentrations of PAN and O 3 during the observational period are (0.73±0.56)×10 -9 and (53±25)×10 -9 , respectively. The hourly maximum concentrations of PAN and O 3 are 3.49×10 -9 and 137×10 -9 . The volume concentrations of PAN and O 3 show pronounced diurnal profiles, which are both characterized by much higher values at daytime than at nighttime. In addition, the correlation coefficient between PAN and O 3 at daytime ( R 2 =0.52) is notably higher than that at nighttime ( R 2 =0.21). The air masses originating from the south show the highest volume concentration of PAN and O 3 , with the lowest volume concentration originating from the east. The wind rose plot and cluster analysis of the back trajectories show that the highest concentration of pollutants mainly originates in the southwest. The air massess originating from the east and circulating through the Bohai Sea and coastal areas of the Hebei and Liaoning provinces show the lowest volume concentrations of PAN and O 3 . The transportation within the boundary layer plays an important role in the concentration distribution of PAN and O 3 .

Ambient O3, NOx, NOy, and CO were measured at the Shangdianzi regional background station from 26 March to 9 October 2008, and VOCs samples were taken and analyzed. This paper uses the data to obtain the ozone production efficiency (OPE) at Shangdianzi and studies the relationship of OPE with NO, and VOCs. In addition, the potential impact from the dry deposition of NOx oxidation products on the calculated OPE was estimated and tentatively corrected. Based on this study, the daily OPE varied in the range of 0.2-21.1, with an average of 4.9 +/- 3.6. An overall OPE average of 4.3 +/- 1.5 can be obtained. The dependence of OPE on the NO, concentration can be described using an empirical parabolic function. If the concentration of NOx is lower than 14 x 10(-9), OPE increases with NO,; while if the concentration of NOx is higher than 14 x 10(-9), OPE decreases with NOx. The correlation analysis indicates that the concentrations of aromatics and OVOCs are positively correlated to OPE. Dry deposition of HNO3 and other NO, oxidation products may significantly impact the calculated OPE values, leading to overestimate. It is possible to correct such overestimate using the NOy/CO ratios obtained at an urban site and at Shangdianzi. However, this correction is less rigorous and the corrected OPE data remain to be validated. The uncorrected data can be viewed as the upper limit of the real OPE.

Mu transposition recombination technique was firstly used as a mutagenesis tool to explore a cluster of genes involved in biosynthesis and regulation of pigments in P. aeruginosa. Eight pigment mutants were screened and identified. Gene cloning and sequencing of the region flanking the insertion revealed that the genes hmgA, ptsP, sucC, phzS, phzF1 were disrupted with mini-Mu respectively. Among them, gene hmgA is involved in the degradation of tyrosine, others affect the metabolism of pyocyanin which is the most important pigment of P. aeruginosa. Both gene phzS and gene phzF1 have been experimentally demonstrated to participate in pyocyanin synthesis. Gene ptsP belongs to a phosphotransferase system and gene sucC encodes succinyl-CoA synthetase beta chain. This is the first report that gene ptsP and sucC may be involved in the regulation of the biosynthesis of pyocyanin.