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11Trace elements (TEs) emitted from coal-fired power plant has caused widespread 12 concern. The onsite investigation of the TEs emission from a Chinese 660MW 13 pulverized coal (PC) boiler equipped with SCR, ESP, WFGD and WESP was 14 conducted by using US EPA Method 29. Simultaneous sampling of the coal, bottom 15 ash, ESP ash, flue gas and by-products from WFGD and WESP process was 16 performed. Results show that TEs mass balance rates for the entire system, furnace 17 and each air pollution control device (APCD) are in acceptable range of 70-130%, 18 which confirms the validity and reliability of the field test data. The studied TEs are 19 mainly distributed in bottom and ESP ash with the ratio of 2.11%-12.15% and 20 87.83%-97.83% respectively while little amount of them exists in WFGD, WESP and 21 stack. Coal combustion by-products like bottom ash and gypsum have little influence 22 on soil from the perspective of TEs while more attention should be paid to Ni, Zn and 23 Cd in the ESP ash. Waste water from WFGD should be treated carefully especially 24 for Cr and Mn. WESP waste water has no influence on ground water except Mn, Ag 25 and Sb. Zn, Ni and Sb prefer to enrich in ESP ash while accumulation of Mn occurs in 26 bottom ash. Ba is enriched in both bottom and ESP ash. ESP has great removal 27 efficiency for TEs with value exceeding 99.87%. Both WFGD and WESP are capable 28 to capture TEs, which results in the overall removal rate across ESP + WFGD + 29 WESP more than 99.90%. TEs concentration in the flue gas emitted from the stack is 30 extremely low with the range of 0.00-1.33 µg/m 3 . The ultra-low emission (ULE) 31 coal-fired power plant equipped with SCR + ESP + WFGD + WESP has good effects 32 on TEs emission control.33

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Due to widespread global mercury pollution via anthropogenic activities such as coal combustion and its severe toxicity even at low concentrations, it is necessary to remove mercury from power plant flue gas to protect both humans and the ecosystem. Currently, significant efforts are being made to maximize Hg 0 adsorption rates while minimizing the impact on the cost of electricity. The purpose of this study is to explore the influence of different sulfur forms on vapor Hg 0 removal by SO 2 -impregnated porous carbons. After SO 2 impregnation, reductive heat treatment in N 2 and H 2 O 2 oxidation process was used to diverge the sulfur form composition in porous carbons. The ultimate and X-ray photoelectron spectroscopy analysis were used to verify the sulfur species. The pore structures of sorbents were determined by nitrogen adsorption/desorption measurements. Then, their mercury removal performance was investigated in a fixed-bed reactor and the influence of different sulfur forms on equilibrium mercury adsorption capacity and mercury desorption was studied. Finally, the kinetics of mercury adsorption on SO 2 -impregnated sorbents was explored to identify whether the adsorption process is controlled by chemical adsorption. The results showed that apparent increases in the quantities of reduced sulfur species were observed after heat treatment, which is assumed to be beneficial for mercury adsorption. H 2 O 2 oxidation after SO 2 impregnation has caused a loss of reduced and nonoxidized sulfur forms in porous carbons, as well as an increase in insoluble oxidized sulfur species. One interesting finding is that even though the micropore volumes of porous carbons decreased after heat treatment, the Hg 0 adsorption capacities of reduced samples and the thermal stability of adsorbed mercury were both positively raised. After H 2 O 2 treatment, the oxidized SO 2 impregnated samples showed an obvious decrease in Hg 0 adsorption capacity. Compared with nonoxidized and oxidized sulfur forms, the reduced sulfur forms have shown a rather significant correlation with the mercury adsorption performance of SO 2 -impregnated samples. Kinetic analysis illustrates that mercury adsorption on SO 2 -impregnated porous carbons was mainly controlled by chemical adsorption.

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