Effect on the Photo-production of Dissolved Gaseous Mercury in Post-desulfurized Seawater Discharged from a Coal-Fired Power Plant

Abstract

A high concentration of dissolved gaseous mercury (DGM) was detected in post-desulfurized waste seawater, which was discharged from a coal-fired power plant equipped with a seawater desulfurization system and which was located in a coastal area. A large amount of DGM was converted from other forms of mercury during transformation processes, such as photo-reduction. The present study targeted the photo-reduction of mercury and the effects of various environmental parameters on DGM production in the post-desulfurized seawater discharged. The results suggested that the photoreduction of mercury was significantly induced under UV radiation, especially with UVB. The particulate mercury on suspended solids was easily photo-reduced and considered as an important source of DGM. It was confirmed that the suspended solids in postdesulfurized seawater could enhance the reduction process of mercury under UV radiation. The pseudo-firstorder rate constants of DGM production, which were determined through the concentration gradient and trial methods, were 1.39×10 −3 min −1 and 1.45×10 −3 min −1 , respectively. The values showed no significant difference and were both much higher than the reported results, indicating that the photo-reduction of mercury in post-desulfurized seawater deserved more attention. In addition, the initial mercury level was observed when mixing the post-desulfurized seawater with fresh seawater, and this suggested that a significant amount of initial mercury would be produced when the post-desulfurized seawater was discharged into the adjacent sea area and thus becomes another considerable source of DGM.

Experimental Determination of Mercury Photoreduction Rates in Cloudwater

“…This is clearly demonstrated in UV‐Test #3, in which Hg D accounted for only 10% of Hg T yet more than 55% of Hg T was photoreduced after the exposure to UV radiation for ∼50 hr, suggesting that a considerable fraction of Hg P was photoreduced. Similar photoreduction behavior of Hg P in solutions was also reported in lake water (O’Driscoll et al., 2018) and seawater (Sun et al., 2015). The photoreduction of Hg P in cloudwater likely occurs through the photochemical conversion from Hg P to Hg D , followed by photoreduction of Hg D .…”

Application of an Isotope Binary Mixing Model for Determination of Precise Mercury Isotopic Composition in Samples with Low Mercury Concentration

“…Although the effect of different matrices on isotope analysis have been conducted, , most studies, including ours, have preferred to use the same matrix solution to dilute standards and samples in order to avoid matrix interference. , In this study, the standard addition method was employed to evaluate both the influence of initial mercury on the isotopic compositions of the mixing solutions and the isotope data of the binary mixing model. Previous results have shown that initial mercury was elemental mercury generated through mixing between high concentration and low concentration mercury solutions. , Therefore, a standard solution (NIST SRM 3133) of high concentration was mixed with an in-house standard (NIST RM 8610) of low concentration in incremental proportions. A total of eight samples were prepared in duplicate by spiking the in-house standards with NIST SRM 3133 at four different mixture proportions.…”

“…Previous results have shown that initial mercury was elemental mercury generated through mixing between high concentration and low concentration mercury solutions. 49,50 Therefore, a standard solution (NIST SRM 3133) of high concentration was mixed with an in-house standard (NIST RM 8610) of low concentration in incremental proportions. A total of eight samples were prepared in duplicate by spiking the in-house standards with NIST SRM 3133 at four different mixture proportions.…”