Distribution of colloidal trace metals in the San Francisco Bay estuary

̃udo-Wilhelmy, Sergio A. San; Rivera-Duarte, Ignacio; Flegal, A. Russell

doi:10.1016/s0016-7037(96)00284-0

Cited by 172 publications

(100 citation statements)

References 75 publications

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“…One of the processes is the adsorption-desorption of trace metals in estuarine mixing zones. Salinity and pH have been found to strongly affect mobility and flux rates of trace metals [13] when they are carried by rivers to various estuarine/coastal systems around the world; for instance, in the Galveston Bay estuary in Texas [14], the San Francisco Bay Estuary in California [15], the Changjiang Estuary in China [16,17], the Bang Pakong Estuary in Thailand [18], the Scheldt Estuary in the Netherlands [19], and the Conwy Estuary in North Wales [20]. The ongoing saltwater intrusion in the world's estuaries may shift metal mobilization and precipitation landwards, the occurrence and effects of which are not well investigated.…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal Distributions of Sr and Ba along an Estuarine River with a Large Salinity Gradient to the Gulf of Mexico

2016

Water

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Strontium and barium to calcium ratios are often used as proxies for tracking animal movement across salinity gradients. Many estuarine rivers face saltwater intrusion due to sea level rise, potentially causing changes in mobility and distribution of these metals upstream. From May 2013 to August 2015, monthly water samples were collected and in-situ measurements were performed at six sites along an estuary strongly affected by saltwater intrusion, the Calcasieu River, with salinity ranging from 0.02 to 29.50 Parts Per Thousand (ppt). Results showed that the total Sr concentration and the Sr/Ca ratio both increased significantly with increasing salinity. The average Sr concentration at the site closest to the Gulf of Mexico (Site 6) was 46.21 µmol/L, about 130 times higher than that of the site furthest upstream (Site 1, 0.35). The average Sr/Ca ratio at Site 6 (8.41 mmol/mol) was about three times the average Sr/Ca ratio at Site 1 (2.89). However, the spatial variation in total Ba concentration was marginal, varying from 0.36 to 0.47 µmol/L. The average Ba/Ca ratio at Site 1 (4.82 mmol/mol) was about 54 times the ratio at Site 6 (0.09), showing a negative relation between the Ba/Ca ratio and salinity. All elemental concentrations and ratios had considerable seasonal variations, with significant differences among sampling months for the Sr and Ba concentrations and the Ba/Ca ratio (p < 0.01). The results suggest that for low-gradient estuarine rivers such as the Calcasieu River, water chemistry upstream would experience substantial Sr and Ca enrichment, potentially affecting aquatic environments and biological communities.

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Section: Introductionmentioning

confidence: 99%

Spatiotemporal Distributions of Sr and Ba along an Estuarine River with a Large Salinity Gradient to the Gulf of Mexico

2016

Water

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“…The iron (Fe)-HS peak occurs at ,20.6 V, at nearly the same potential as the peak for Fe-DHN. The CSV response for FA (Suwannee River FA) and HA (SRHA) standards in ultraviolet (UV)-digested seawater in the presence of bromate was found to be the same as that for HS in natural waters (fresh, estuarine, and coastal waters), indicating that FA and HA are good model compounds for the natural HS.HS and iron are known to co-precipitate at the lowsalinity end of estuaries (Sholkovitz and Copland 1981), removing more than 99% of the dissolved iron and lowering its concentration from 0.5-10 mmol L 21 , which is typical for freshwaters (Nagai et al 2007), to the 1-20 nmol L 21 range found in end-estuarine and coastal waters (Sanudo-Wilhelmy et al 1996;Buck and Bruland 2007). The estuarine removal reactions indicate that iron complexation with HS might be relatively unimportant in seawater, although it is important in freshwaters.…”

mentioning

confidence: 98%

“…HS and iron are known to co-precipitate at the lowsalinity end of estuaries (Sholkovitz and Copland 1981), removing more than 99% of the dissolved iron and lowering its concentration from 0.5-10 mmol L 21 , which is typical for freshwaters (Nagai et al 2007), to the 1-20 nmol L 21 range found in end-estuarine and coastal waters (Sanudo-Wilhelmy et al 1996;Buck and Bruland 2007). The estuarine removal reactions indicate that iron complexation with HS might be relatively unimportant in seawater, although it is important in freshwaters.…”

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confidence: 99%

Evidence for geochemical control of iron by humic substances in seawater

Laglera

Berg

2009

Limnology & Oceanography

264

310

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A new method, based on the direct detection of iron-humic substance (HS) species by cathodic stripping voltammetry (CSV), is used to determine the iron binding capacity and complex stability of fulvic acid (FA), humic acid (HA), and the natural HS in the seawater. The FA binds 16.7 6 2.0 nmol iron (Fe) (mg FA) 21 , whereas the HA and the marine HS bind 32 6 2.2 nmol Fe (mg FA) 21 . The complex stabilities are (log K9 Fe9HS values) 10.6 for FA and 11.1 for HA and coastal HS. Measurements of coastal waters (Irish Sea) show that the HS occur in a widespread fashion, the HS concentration decreasing with increasing salinity and occurring at levels of 400 (at salinity 30) to 70 (at salinity 34) mg L 21 . A sample from the deep Pacific was found to contain 36 mg HS L 21 , amounting to 4% of the dissolved organic matter. Comparative measurement of the total iron complexing capacity by CSV with competitive ligand exchange showed that the natural HS can account for the entire ligand concentration in the shallow coastal and deep ocean waters tested. Measurements of the iron solubility showed that FA added to seawater and the HS in coastal waters maintain iron in solution at a level just below the iron binding capacity. The preliminary data for the open ocean indicate that the same may be true for HS in deep ocean waters. The data are consistent with a mechanism by which iron is transported from land to sea, associated with land-derived HS.Humic substances (HS) are ubiquitous hydrophobic components of the natural organic matter present in soil and aquatic environments that consist predominantly of polyphenols and benzoic/carboxylic acids (Buffle 1990). HS are operationally divided into humic acids (HAs) and fulvic acids ( Previous work has shown that HS in seawater can be determined at good sensitivity by cathodic stripping voltammetry (CSV), which takes advantage of adsorption of the complex on the mercury drop electrode as a concentration step prior to the CSV scan; bromate is added to enhance the sensitivity through a catalytic effect (Laglera et al. 2007). A very similar procedure (Obata and Van Den Berg 2001) is used to determine iron in seawater by means of CSV in the presence of a specific adsorptive ligand (2,3-dihydroxynaphthalene; DHN). The iron (Fe)-HS peak occurs at ,20.6 V, at nearly the same potential as the peak for Fe-DHN. The CSV response for FA (Suwannee River FA) and HA (SRHA) standards in ultraviolet (UV)-digested seawater in the presence of bromate was found to be the same as that for HS in natural waters (fresh, estuarine, and coastal waters), indicating that FA and HA are good model compounds for the natural HS.HS and iron are known to co-precipitate at the lowsalinity end of estuaries (Sholkovitz and Copland 1981), removing more than 99% of the dissolved iron and lowering its concentration from 0.5-10 mmol L 21 , which is typical for freshwaters (Nagai et al. 2007), to the 1-20 nmol L 21 range found in end-estuarine and coastal waters (Sanudo-Wilhelmy et al. 1996;Buck and Bruland 2007). The...

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“…27,28 Indeed, many workers have demonstrated that a significant, but variable fraction of dissolved trace metals in seawater is associated with colloidal organic matter. 29,30 The interest of the studying trace-metal complexation by organic matter is that they can control the availability of metals by regulating their dissolved free-ion concentration, and thus decrease or increase the adsorption of trace-metals onto particles affecting metal fate and transport. Coastal seawater is more dynamic than the open-ocean environment, being subject to varying influences of atmospheric inputs, originating from the continent and phytoplankton productivity.…”

Section: Introductionmentioning

confidence: 99%

Determination of Trace Metal Complexes by Natural Organic and Inorganic Ligands in Coastal Seawater

Abbasse¹,

Ouddane²,

Fischer³

2003

ANAL. SCI.

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The distribution, mobility, bioavailability, toxicity, bioaccumulation and biodegradability of chemical elements depend not only on their concentrations, but also on their physico-chemical associations with natural systems. [1][2][3][4] Several trace metals occur in natural water distributed between different oxidation states. At equilibrium, the species present are controlled not only by the pH, but also by the redox potential of the system that describes the progress of electron-transfer reactions. 5 The dissolved forms of trace elements are mainly present as free hydrated ions, ion pairs (where the coordinated water is retained), and inorganic and organic complexes with a covalent bound. For example, dissolved trace metals can also form complexes with a wide range of organic and inorganic compounds, depending on the pH, oxidation state, and relative abundance of the complexing agents. The main inorganic compounds are chloride, carbonate, sulfate, hydroxyl, and fluoride; the complexes formed between them and trace metals are almost always very labile. Organic ligands include both biochemical species of low molecular weight (<10 3 ), such as siderophores, carboxylic acids, aminoacids, sugars, small hydroxyacids, 6 etc., and heterogeneous compounds of unknown structure 7-9 with a wide range of relative molecular masses (10 3 -10 7 ). At any rate, there is great certitude that stronger ligands, which are able to complex metal ions, but are not yet completely identified, are present in seawater, most often at very low concentrations. These various forms of organic matters in aquatic systems come largely from living organisms, mainly as polypeptides and polysaccharides in algae exudates, 10 and from pollution sources. Estimating the ligand organic concentration in natural water has until now been a difficult problem. Generally, though the water of open-ocean contains only small amounts of organic matter.The maximum concentration of total organic carbon observed in surface waters is less than 200 µmol/L. 11 Especially prominent among organic matter compounds in aqueous systems are humic substances. These compounds, which result from living matter decay, are a mixture of organic polymers containing charged hydrophobic and hydrophilic groups that possess polyelectrolyte and multifunctional proprieties. In solution, these compounds can occur either in free form, often negatively charged, or bound to others, such as glycine, aspartic acid and alanine. The principle functional groups in humic matter are -COOH, -NH2, -OH and -SH, [12][13][14] It is well-documented that organic compounds form strong complexes with most metals in aquatic systems, and that seawater is a complex medium which contains a large variety of organic and inorganic ligands, including colloidal matter. We suggest that most trace metals are complexed in seawater and that some inorganic metals complexes are either labile or not stable. In contrast, metal-organic complexes are often stable and need various and specific treatments to be dissociated. In t...

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Distribution of colloidal trace metals in the San Francisco Bay estuary

Cited by 172 publications

References 75 publications

Spatiotemporal Distributions of Sr and Ba along an Estuarine River with a Large Salinity Gradient to the Gulf of Mexico

Spatiotemporal Distributions of Sr and Ba along an Estuarine River with a Large Salinity Gradient to the Gulf of Mexico

Evidence for geochemical control of iron by humic substances in seawater

Determination of Trace Metal Complexes by Natural Organic and Inorganic Ligands in Coastal Seawater

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