RESUMO
Based on the advantage of spectroscopy method and the significant effect of ·OH and ·O in advanced oxidation degradation system, the change of relative emission spectra intensities of the ·OH and the ·O in a pulsed discharge plasma (PDP) system bubbled with oxygen were tested by using the spectrum detecting technique in this research. The PDP system with needle-to-net electrode was set up in the paper to remediate the polluted soil. The relative emission spectra intensities of the ·OH and the ·O formed in the PDP system with oxygen (O2) bubbling were detected with the spectrograph to illustrate the critical effect of the ·OH and the ·O on the organic compound degradation in the PDP system. The changes of the relative emission spectra intensities of the ·OH and the ·O under the conditions of without soil addition, with the original soil addition, with the organic compound polluted soil addition and with the organic compound-heavy metal polluted soil addition were firstly investigated in the paper. The effect of peak pulse voltage, electrode gap and O2 flow rate on the relative emission spectra intensities of the ·OH and the ·O were also studied to explain the changing rule of the active species in the PDP system. The obtained results show that the addition of soil are beneficial to the formation of the ·OH and the ·O in PDP system for the soil remediation. The relative emission spectra intensities of the ·OH and the ·O in the PDP system with organic compounds polluted soil addition were lower than those in the PDP system with the original soil addition, which proved the oxidation of the ·OH and the ·O on the organic compounds degradation in the remediation system, and the addition of heavy metal ions were favorable to the degradation of the organic compounds in the PDP system. Furthermore, the increase of the peak pulse voltage as well as theO2 flow rate was in favor of the formation of the ·OH and the ·O, while the relative emission spectra intensities of the ·OH and the ·O were lower under the condition of the higher electrode gap, which demonstrated that the higher electrode gap were not in favor of the active species formation. In the study, based on the description of the pivotal role of ·OH and the ·O in the PDP system for the polluted soil remediation, the influence rule of the main factors during the process of polluted soil remediation in the PDP system on the content of ·OH and the ·O were analyzed. This research will provide some basic experimental evidence for the application of PDP technology on the polluted soil remediation.
RESUMO
Based on the higher oxidation potential of OH radicals (2.8 V), the synergetic effect of pulsed discharge plasma (PDP) and activated carbon (AC) and the advantages of emission spectroscopic detection, such as easy operation, high accuracy and high sensitivity, the relative emission spectra of the OH radicals generated in the PDP/AC system with oxygen flow were measured by the emission spectroscopic detection technique and the spectral intensity of the OH radicals was used to represent the relative amount of the OH radicals formed in the reaction system. The effect of additive amount of the AC, peak pulse voltage and electrode gap on the relative emission spectrum intensities of OH radicals were investigated to illustrate the crucial factors for the OH radicals formation in the PDP/AC system. In addition, the formation of OH radicals in the two liquid phases of distilled water and acid orange 7 (AO7) solution in the sole PDP system and the PDP/AC system were investigated to testify the synergetic mechanism of PDP/AC and the oxidization of OH radicals on the organic compounds in the reaction system. The obtained results showed that the catalytic effect of the AC increased with the increase of the additive amount of the AC in the PDP system, which led to the increase of the relative emission spectral intensities of the formed OH radicals in the synergistic system; higher peak pulse voltage was in favor of the energy input in the discharge system and then enhanced the formation of OH radicals; increase of the electrode gap led to the decrease of energy efficiency in the reaction system and the decrease of the formed OH radicals in the PDP/AC system; the formation of OH radicals in the PDP/AC system was higher than that in the sole PDP system both in the distilled water and in the AO7 solution; the formation of OH radicals in the distilled water was higher than those in the AO7 solution no matter the reaction system was the sole PDP system or the PDP/AC system. The two results indicated that the AC addition was beneficial to the formation of OH radicals in the PDP system and the OH radicals had an important effect on the organic compounds degradation both in the sole PDP system and in the PDP/AC system.
RESUMO
In order to reveal vertical distribution characteristics of nitrogen and organic matter in the ancient canal sediments of Zhenjiang old town, the columnar sediment samples in Dianli road bridge (D) and Nanshui bridge (B) were collected, contents of total nitrogen (TN), organic nitrogen (Org-N), ammonia nitrogen (NH4(+)-N), nitrate nitrogen (NO3(-)-N) and organic matter (O. M) were determined, and C/N, nutrient concentration coefficient and the correlation of nitrogen, O. M and environmental factors had been analyzed, and organic nitrogen and organic index had also been evaluated. The results showed that (1) The average contents of TN, Org-N, NH4(+) -N, NO3(-) -N and O. M were 366.33 mg x kg(-1), 348.02 mg x kg(-), 89.47 mg x kg(-1), 13.51 mg x kg(-1), 0.43%, respectively, in Dianli road bridge (D). And the average contents of TN, Org-N, NH4(+) -N, NO3(-) -N and O. M were 940.23 mg x kg(-1), 893.22 mg x kg(-1), 169.48 mg x kg(-1), 15.19 mg x kg(-1), 0.76%, respectively, in Nanshui bridge (B). The ranked order of average N and O. M was D < B, which indicated that nitrogen and organic matter pollution in Nanshui bridge (B) was more serious than that in Dianli road bridge (D). (2) The results of C/N indicated that the O. M source of sediment was zooplankton and phytoplankton in ancient canal. (3) There was no significant difference (P > 0.05) of nutrient concentration coefficient between D and B sampling points, which indicated that the concentration process of nitrogen and organic matter was similar in D and B sampling points. (4) TN and O. M were not significantly correlated, which indicated that TN might come from exogenous pollution. (5) The organic index evaluation results showed that ancient canal sediments of Zhenjiang old town were in a cleaning situation, and organic nitrogen still belonged to fairly cleaning and slight cleaning categories.
