Pore waters, estuarine sediments

This removal may also include diffusion of soluble U(VI) from seawater into the sediment via pore water. Uranium-organic matter complexes are also prevalent in the marine environment. Organically bound uranium was found to make up to 20% of the dissolved U concentration in the open ocean." ° Uranium may also be enriched in estuarine colloids and in suspended organic matter within the surface ocean. " Scott" and Maeda and Windom" have suggested the possibility that humic acids can efficiently scavenge uranium in low salinity regions of some estuaries. Finally, sedimentary organic matter can also efficiently complex or adsorb uranium and other radionuclides. 

Cochran JK (1984) The fates of U and Th decay series nuclides in the estuarine environment. In The Estuary as a Filter. Kennedy VS (ed) Academic Press, London, p 179-220 Cochran JK (1992) The oceanic chemistry of the uranium - and thorium - series nuclides. In Uranium-series Disequilibrium Applications to Earth, Marine and Environmental Sciences. Ivanovich M, Harmon RS (eds) Clarendon Press, Oxford, p 334-395 Cochran JK, Masque P (2003) Short-lived U/Th-series radionuclides in the ocean tracers for scavenging rates, export fluxes and particle dynamics. Rev Mineral Geochem 52 461-492 Cochran JK, Carey AE, Sholkovitz ER, Surprenant LD (1986) The geochemistry of uranium and thorium in coastal marine-sediments and sediment pore waters. Geochim Cosmochim Acta 50 663-680 Corbett DR, Chanton J, Burnett W, Dillon K, Rutkowski C. (1999) Patterns of groundwater discharge into Florida Bay. Linrnol Oceanogr 44 1045-1055... 

Toxicity in estuarine sediments—use of Mutatox and Microtox to evalu- 173 ate the acute toxicity and genotoxicity of organic sediments Toxicity tests for the analysis of pore water sediment a comparison of 4 174... 

Li et al. [323] studied the bacterial transformation of pyrene in an estuarine environment (Kitimat Arm, British Columbia, Canada), where they separated a metabolite (i.e., ris-4,5-dihydroxy-4,5-dihydropyrene) from the sediment and pore waters. The presence of this key metabolite from the dioxygenase-mediated transformation of pyrene [100, 186, 342], along with previous pyrene degradation studies using cultures isolated from the same sediment samples, suggested a possible in situ bacterial transformation of pyrene in the Kitimat Arm environment. 

Table 6 Results of in vivo bioassays with sediment or sediment pore water from estuarine and coastal locations in the ...

It offers the possibility of incorporating any bioassay that is currently available. It thus provides the current best estimate of relative hazard for the sites being investigated. There is however a continuing need to develop, both for freshwater and marine or estuarine ecosystems, a battery of validated toxicity tests with sensitive species for whole sediment, wet sediment, organic extract, and pore water. 

Skrabal, S.A., Donat, J.R., and Burdige, D.J. (2000) Pore water distributions of dissolved copper and copper-complexing ligands in estuarine and coastal marine sediments. Geochim. Cosmochim. Acta 64, 1843-1857. 

Ammonium is present at very low concentrations (0.03—0.5 iM) in oceanic surface waters, at higher concentrations in coastal and estuarine waters (Sharp, 1983), and at concentrations orders of magnitude higher in sediment pore waters. In seawater, NH4+ exists as the acid base pair NH4+-NH3 (ammonia) the pFC of the pair is 9.3. The methods discussed here measure the sum of NH4+, the form that dominates at the pH of seawater ( <8.3), and NH3, the volatile form that dominates under more alkaline conditions. There are many approaches to measuring NH4+, but we win focus on the two most widely used— phenol-hypochlorite and orthophtal-dialdehyde (OPA). 

Hines M. E., Orem W. H., Lyons W. B., and Jones G. E. (1982) Microbial activity and bioturbation-induced oscillations in pore water chemistry of estuarine sediments in spring. Nature 299, 433-435. 

Some studies have reported conservative behavior during estuarine mixing. In the unpolluted Krka Esmary of Yugoslavia, Seyler and Martin (1991) observed a linear increase in total arsenic with increasing salinity, ranging from 0.13 xgL in freshwaters to 1.8 JLgL offshore. Other studies however, have observed nonconservative behavior in estuaries due to processes such as diffusion from sediment pore waters, co-precipitation with iron oxides, or anthropogenic inputs (M. O. Andreae and T. W. Andreae, 1989 Andreae et al., 1983). The flocculation of iron oxides at the freshwater-saline interface as a result of increase in pH and salinity can lead to major decrease in the arsenic flux to the oceans (Cullen and Reimer, 1989). 

Important for understanding factors controlling the biogeochemical cycle of PCBs In the environment more specifically aquatic ecosystems Including estuaries. Our data have demonstrated this for the case of a severely polluted coastal estuarine area, both for the data discussed herein and for pore water, sediment and water column data presented and discussed elsewhere (10, 30). 

DOC Estuarine waters, sediment pore waters UV irradiation for improving oxidation with peroxydisulfate in acidic medium UV-Vis 0.26 mg L 1 Air-segmented flow analyser in-line C02 dialysis [425]... 

Figure 1 Biogeochemical cycles in estuarine and coastal sediments. Particles that fall to the sediment-water interface simultaneously undergo chemical reactions and are mixed through the upper few centimeters of the sediment column. Chemical transformations alter the particles and the sedimentary pore waters surrounding them, driving solute exchange between sediments and the water column and determining the composition of accumulating sediments.

HiS levels in pore waters. In these locations, Fe phosphate minerals may control Fe solubility. The combination of laboratory equilibration studies and pore water solute concentration measurements led Martens et al., for example, to conclude that deep pore waters were in equilibrium with vivianite -F63P04 8H2O - in a coastal sediment. Hyacinthe et al. found that iron was sequestered as an Fe(iii) phosphate in low-salinity, estuarine sediments. This ferric phosphate may have been formed in surface sediments (see below) or in the water column. 

Figure 4 also shows the removal of Mn " " from pore waters below the zone where it is added by reductive dissolution of Mn oxides. Equilibrium calculations have been used to infer that the mineral controlling Mn solubility in coastal and estuarine sediments is most likely to be a mixed Mn, Ca carbonate,... 

The sediments are also important sites for ther removal of fixed nitrogen from coastal waters. Because there is relatively little NOs in the shallow waters overlying coastal and estuarine sediments, diffusion of NOs from bottom water is not a major source of N for denitrification. However, rapid organic matter oxidation results in the release of NH4+ to the pore waters. NH4+ can be converted to Ni by a nitrification/denitrification cycle or by NH4+ oxidation coupled to the reduction of NOs ... 

Microbial extracelMar polymeric substances (EPSs) - ubiquitous features in aquatic environments - actively participate in binding dissolved overlying and pore-water metals in sediments. Organic sediment coatings in the form of bacterial EPS equivalent to about 0.5% orgaiuc matter can adsorb cadmium under estuarine conditions. 

Thus, pore water studies provide evidence that some trace elements (As, Co, Cr) become more soluble on redox dissolution of Mn-Fe oxides in marine and sediments. However, these studies have failed to detect a parallel release of trace elements (other than Co) with Fe and Mn during redox events (Sakata, 1985 Morfett et al., 1988 Achterberg et al., 1997). It appears that in spite of the loss of labile organic matter and oxides of Fe and Mn, the trace elements remain relatively immobile. In oceanic or estuarine sediments it has been proposed that sulphides have a role to play in fixing the trace elements under reducing conditions. This has also been demonstrated in sulphate-rich freshwater systems (Huerta-Diaz et al., 1998). However, Cu and Pb, at least, clearly remain firmly attached to freshwater sediment even in the absence of measurable sulphides, and where Mn and Fe are being actively released via reduction (Sakata, 1985). 

The pore water composition of lanthanides is poorly characterized. Low concentrations and small volumes of pore water samples (typically 10-50 ml) combine to make detection difficult. Only the lanthanide-enriched pore waters of anoxic coastal and estuarine sediments have been measured at a few sites (sect. 6). Currently, the pore water chemistry of lanthanides in non-coastal marine sediments is unknown. The field of lanthanide pore water chemistry remains an important challenge. 

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