Mercury transformations and exchanges in a high turbidity estuary:

Abstract

The speciation and partition of mercury in a macrotidal estuary (Seine estuary, France) was studied in order to explore the role of the high turbidity zone (HTZ) in mercury transfer to the adjacent coastal waters. Water and particles were analyzed to determine the concentrations of various mercury species, including monomethylmercury and the inorganic fraction. The exchangeable particulate mercury, which varies with salinity, and the mercury fraction associated with the amorphous oxyhydroxides were evaluated. The distribution of dissolved mercury species during early mixing suggests non-conservative behavior of organically bound mercury at the head of the estuary. Mercury in the particles covaried positively with suspended particulate matter concentrations up to a threshold, which constitutes the typical mercury load of particles and deposited sediments of the HTZ. This distribution pattern is well explained by a dilution model: a slowly settling, low metal population of particle, characterized by relatively invariant turbidity, becomes admixed with a variable amount of higher metal content particles derived from the resuspension in the HTZ. In addition, in the HTZ, which acts as a degradation reactor for particulate organic matter, particulate mercury concentrations increase with increasing C:N ratios and amorphous oxyhydroxides particles. Mercury reaches the estuarine HTZ mainly associated with the riverine and marine particles, including organic matter and oxyhydroxides, which are temporarily trapped in the HTZ and mixed with autochthonous HTZ particles. The largest particles periodically settle and undergo diagenetic reactions and resuspensions, which lead to their mercury enrichment. Depending upon hydrodynamic conditions, mercury escapes seaward as fine particulate within the plume, partially associated with the oxyhydroxides. A surface complexation model reproduces most of the partitioning observed. In the dissolved phase the model simulation suggests that a very strong ligand must be present to explain the field observations. Low (summer) 1.32 ± 0.04 (n=5)1.34 ± 0.12 (n=8) 1.70 ± 0.17 (n=9) 1.59 ± 0.33 (n=13) (HgT) P (nmol.g -1 ) High (winter) nd 2.34 ± 0.67 (n=14) 1.21 ± 0.45 (n=9) 0.44 ± 0.21 (n=11)

Characteristics of dissolved organic matter (DOM) and relationship with dissolved mercury in Xiaoqing River-Laizhou Bay estuary, Bohai Sea, China

“…dissolved Hg could not be explained by a conservative mixing of two end-members: terrestrial/allochthonous and non-terrestrial/ urban/atmospheric sources of Hg. Similar non-conservative patterns of Hg changes from freshwater to estuary had also been previously reported (Han et al, 2006;Can ario et al, 2008;Laurier et al, 2003;Balcom et al, 2008). Notably, in high salinity water, inorganic ligands (e.g.…”

“…As shown in Table S2 Conaway et al, 2003;Choe et al, 2004). Yet our values were still higher than some other estuaries (e.g., New York/ New Jersey harbor estuary of US; Balcom et al, 2008;and Seine estuary of France;Laurier et al, 2003). Additionally, the Xiaoqing River showed a higher concentrations of dissolved Hg than the tributaries of the Chesapeake Bay, US (Lawson et al, 2001).…”

“…Across various aquatic systems, river-estuary systems are important ecological environments. In recent years, Hg cycling in estuarine and coastal marine environments have been widely studied (Merritt and Amirbahamn, 2009;Pan and Wang, 2012;Mason et al, 1999;Laurier et al, 2003;Lawson et al, 2001;Han et al, 2006;Can ario et al, 2008;Choe et al, 2004;Conaway et al, 2003). There are only a few reports on the Hg contamination in Chinese estuaries, where high levels of Hg commonly are encountered, caused by the rapid industrial developments (Wang et al, 2009, Luo et al, 2012Gao et al, 2014;Ci et al, 2011).…”

Mercury and methylmercury cycling in sediments of the mid‐Atlantic continental shelf and slope

“…Iron can also affect Hg mobility in sediment. For example, the dissolution of Fe(III) oxides has been observed to increase the pore-water concentration of Hg (Gobeil and Cossa 1993;Gagnon et al 1996;Laurier et al 2003), which in turn could increase Hg bioavailability to methylating bacteria. This could be another explanation for the observed relationship in Fig.…”

Heterogeneities of hydrocarbon compositions in mudstones of a turbiditic sequence of the Miocene Kawabata Formation in Yubari, central Hokkaido, Japan

“…have been reported (e.g., Hedges and Keil, 1995;Thomsen et al, 2001;Laurier et al, 2003;Treignier et al, 2006), there have been only a few geochemical studies of older turbiditic sedimentary sequences for reconstruction of long time-scale paleoenvironments and material-cycling systems. Hoefs et al (2002) reported the organic geochemical investigations of Miocene to Pleistocene turbiditic sequences collected by Ocean Drilling Program (ODP) Leg 157 on the Madeira Abyssal Plain (MAP) off northern Africa, which showed variations in biomarker compositions that were attributed to redox conditions (oxygen exposure time) of the depositional environment.…”