Effect of dissolved organic matter on mercury release from water body

Dissolved organic matter（DOM） plays an important role in the process of mercury release from water body.In this study,the influence of DOM from different sources（DOMR,DOMS and DOMH,extracted from rice straw,compost and humic soil respectively） on mercury reduction was investigated.The molecular weight distribution and chemical composition of DOM from each source were determined using ultrafiltration membrane technique and elemental analysis respectively.The result showed that mercury release from DOM-added samples was much lower than the control;the lowest mercury release flux was observed in the treatment of DOMH,25.02% of the control,followed by DOMS and DOMR,62.46% and 64.95% of the control,respectively.The higher saturation degree and lower molecular weight of DOMH was responsible for the highest inhibition degree on the mercury release.The link between DOMH,concentration and mercury flux was also estimated and the result showed that mercury flux was increased with DOMH at lower concentration,while decreased with DOMH at higher concentration.Different mechanism dominated the influence of DOM on mercury release with variation of DOM concentration.

Release of Mercury from Intertidal Sediment to Atmosphere in Summer and Winter

The release of mercury from intertidal sediment to atmosphere was studied based on the simulated experiment. The experiment samples were collected from the Haibo Estuary (S1) and the Licun Estuary (S2) of the Jiaozhou Bay in China,which are seriously polluted with mercury. The results show that the mercury in sediment releases rapidly to atmosphere under solar radiation. After 8 hours of solar radiation,mercury concentrations decrease from 5.62 μg/g and 2.92 μg/g to 2.34 μg/g and 1.39 μg/g in S1 and S2 sediments respectively in summer,and decrease from 5.62 μg/g and 2.92 μg/g to 4.58 μg/g and 2.13 μg/g respectively in winter. The mercury species in the sediment change markedly under solar radiation. The concentrations of mercury bound to organic matter decrease significantly from 2.73 μg/g to 0.31 μg/g in S1 and from 2.07 μg/g to 0.31 μg/g in S2,and the released mercury mainly comes from mercury bound to organic matter. Mercury flux shows distinguishing characteristic of diurnal change,and it increases rapidly in the morning with the rising of solar radiation intensity,but decreases in the afternoon. The mercury flux increases with sediment temperature and solar radiation intensity. The rapid release of mercury in intertidal sediment plays an important role in the regional mercury cycle.

Thermal desorption of mercury from lignite in a high-temperature furnace and in power plant mills

In this article,the binding forms of two lignite samples are determined by thermal desorption using a high-temperature furnace.Each mercury compound,such as HgCl2,has a specifc binding strength whose decomposition requires a certain thermal energy.Hence,the release of mercury from pure substances and lignite samples was analyzed in a high-temperature furnace.The released mercury is determined with a Mercury Vapor Monitor.The obtained characteristic temperature range and peak of the mercury release were compared between lignite samples and mercury pure substances.For the lignite samples investigated,the binding form of mercury was then identifed as Humic Acid.These organic compounds vaporize at lower temperatures.About half of the mercury bound in the lignite was already released at 350℃.Furthermore,the question arises whether mercury is already released during the grinding-drying process in the coal mill of a power plant.At two power plants,lignite samples were taken simultaneously at the feeder before entering the coal mill and at the dust line afterwards.The samples were analyzed for mercury concentration.The results show that up to one third of the mercury was already released in the coal mill.The vaporized mercury enters the combustion chamber detached from the lignite.The stated analysis methods and the results presented in this article contribute to the understanding of the mercury binding forms in lignite.It also shows the potential of thermal coal pretreatment as a favorable alternative mercury separation technology to others such as activated carbon dosing.