Specific Surface Area Of Sediments Research Articles

Muddy sediments are an important potential source of silicon in coastal and continental margin zones

The dissolution of silicate minerals on the seafloor releases an important amount of dissolved silicon (dSi), which is necessary for maintaining high diatom production in Coastal and Continental Margin Zones (CCMZs). However, the dissolution of silicate minerals along the continental shelves is variable, which hinders our understanding of the marine Si cycle on both a regional and global scale. To understand the discrepancy of silicon (Si) released in different sediment matrices and its potential controlling factors, we investigated surface sediments of typical CCMZs of the Chinese marginal Seas using a continuous alkaline extraction technique, grain size and chemical (carbon and total nitrogen) analysis as well as a qualitative measurement of clay mineral composition by X-ray diffraction. The results showed that the amount of Si and aluminum (Al) leached from muddy sediments were 2 times greater than those released from sandy sediments. High dissolution rates (> 0.20 mg-SiO2 g−1 min−1) of silicate minerals are caused by a large sediment-specific surface area. Further, our data showed that biogenic silica (bSi) with high Al content (Si:Al < 40) has low reactivity and that the source of Al incorporated in bSi is silicate minerals undergoing dissolution. We show that although the dissolution of silicate minerals is less active than that of bSi, it still potentially releases more bio-available Si and Al to seawater due to its dominant presence on the seafloor (70.3% − 99.0%wt). This study highlights silicate minerals as an important potential marine Si source and emphasizes the need for a better understanding of the roles of silicate minerals in the Si cycle of marginal seas in future studies.

Predicting distribution coefficients for antibiotics in a river water–sediment using quantitative models based on their spatiotemporal variations

Antibiotics are widely used in humans and animals, but their presence in environmental matrices after use is of great concern. Distribution behavior of antibiotics in natural water–sediment systems is influenced by sediment properties, but how these properties, such as surface area, affect their distribution between water and sediment phases remains unclear. The concentrations of antibiotics also vary both spatially and temporally. In this study, a solid/liquid distribution coefficient Kd(pre) was proposed and evaluated in 12 quantitative predicting models based on aquatic field data compared with a bulk coefficient Kd. Results confirmed by the occurrence pattern, concentration levels and spatiotemporal distributions indicated that the characteristics of antibiotics pollution in rural northwestern Guangzhou were generally consistent with previous investigations, suggesting that this investigation was representative of the present aquatic pollution status of antibiotics. The median concentrations were <100 ng·L−1 and 220 ng·g−1 (d.w.) in the water and sediments, respectively. The most pronounced high concentrations of total antibiotic residue found were 778.0 ng·L−1 for sulfonamides (SAs) in water and 1596.9 ng·g−1 (d.w.) for fluoroquinolones (FQs) in sediments at site 13 in December of 2016, probably due to its dense population, high frequency of antibiotic use and low water flow. Moreover, 12 quantitative models were established with a high level of robustness and ability to spatiotemporally predict the Kd for each of the 12 antibiotics. The models revealed that pH, organic matter and specific surface area of sediments played significant roles in influencing the adsorption of SAs, FQs, tetracyclines (TCs) and (macrolides) MLs. Our findings provide insights into the effects of physicochemical properties on distribution of antibiotics, predicting their fate and transport, as well as assessments of exposure and risk of these emerging pollutants to aquatic ecosystems.

Background values for evaluation of heavy metal contamination in sediments

The contamination of sediments can be evaluated from comparison of the current concentration with the estimated background value. Although it is known that grain size affects background concentrations, there have been difficulties in evaluating this effect. The specific surface area of sediments, which can be calculated from the grain size distribution, is introduced as a property index for correlation of background values. The results show that for sandy-to-sandy silt sediments, the background values of metals are expressed in terms of fines content, which can be correlated with the corresponding specific surface area. However, for silty clay or clayey silt sediments, which would have a high metal retention capacity, the level of the background may be constrained by the relatively low concentrations of metals in seawater. Finally, background levels of Zn, Cu and Pb are presented.

The supply and preservation of ancient and modern components of organic carbon in the Canadian Beaufort Shelf of the Arctic Ocean

The provenance of organic matter in sediments from the Mackenzie River and Beaufort Shelf was investigated using the stable carbon and radiocarbon isotopic compositions of bulk organic matter and the stable carbon isotopic compositions of individual organic compounds, including lignin-derived phenols and lipid-derived fatty acids. Most river suspended sediments and shelf surface sediments contained organic carbon characterized by highly depleted Δ 14C values that were consistent with average radiocarbon ages exceeding 7000 years. The stable carbon isotopic signatures of lignin phenols were uniformly depleted (−25≥ δ 13C≥−32‰), indicating the predominant contributions of C 3 vascular plant sources. The isotopic compositions of C 14 and C 16 fatty acids exhibited important contrasts between the river (−36‰ to −40‰) and shelf (−25‰ to −29‰) sediments that were consistent with contributions from freshwater algae and/or vascular plants in the former and marine phytoplankton in the latter. Using 14C isotopic mass balance, the abundances of modern and ancient organic matter were quantitatively constrained. The fate of organic matter in the Beaufort Shelf was explored by normalizing these abundances to the specific surface area of sediments. Ancient organic carbon, which may include old pre-aged soil material as well as fossil bitumen or kerogen, accounted for the majority (∼70%) of the particulate organic matter exported by the Mackenzie River and deposited in surface sediments of the Beaufort Shelf. Modern organic carbon accounted for ∼30% in both river and shelf sediments, with significant contributions from vascular plant-derived materials in both river and shelf samples and from marine algae in the shelf sediments. Respiration (and/or leaching) of particle-bound marine organic matter dominates the carbon metabolism in the Mackenzie Delta/Beaufort Shelf region. However, land-derived pools, including modern carbon derived from vascular plants as well as ancient carbon also appeared to undergo a degree of post-depositional degradation prior to burial in the shelf. These novel source apportionments are reflected in an updated carbon budget for the study area.

Desorption kinetics for field-aged polycyclic aromatic hydrocarbons from sediments.

This study considers desorption kinetics for 12 field-aged polycyclic aromatic hydrocarbons (PAHs) desorbing from size- and density-fractionated sediments collected from two locations in the New York/New Jersey Harbor Estuary. Desorption kinetics for PAHs with a log octanol-water partition coefficient greater than 6 were well-described by a one-domain diffusion model that assumes that PAHs are initially uniformly distributed throughout spherical sediment aggregates. PAH hydrophobicity and sediment specific surface area were the parameters most strongly correlated with the magnitude of the observed diffusivity for the one-domain model. For less hydrophobic PAHs, a two-domain desorption model was used also, and the results suggest that a substantial fraction of these field-aged PAHs desorb via a relatively fast macro-mesopore diffusion mechanism. The model-predicted fraction of PAHs in the fast-diffusion regime by compound and sediment was highly correlated with the measured percent PAH desorption in 24 h. The fast-domain diffusivity was 100 times greater than the slow-domain diffusivity, was correlated with both PAH properties and sediment physical and chemical properties, and could be estimated by readily obtainable physical and chemical parameters. In contrast, the slow-domain diffusivity was not significantly correlated with PAH properties. Our results suggest that macro-mesopore diffusion may control mass transport of less-hydrophobic PAHs in estuarine sediments.

Factors affecting lysine sorption in a coastal sediment

Sediment sorption capacity was measured in a coastal environment over a 2-year period using lysine as a model compound. Sorption capacity was found to vary over time but did not seem to follow a clear seasonal pattern or relate to organic carbon, sediment grain size distribution, or sediment specific surface area. Instead, adsorption capacity appeared to be more related to annual precipitation patterns. Years of below normal precipitation apparently created conditions with high adsorption capacity, while years with higher than normal precipitation were associated with lower adsorption capacity. Laboratory experiments showed that adsorption capacity of anoxic sediments is lower than for oxidized sediment, and the magnitude of this difference changed with time. Adsorption of lysine, glutamic acid, leucine, melanoidin and naphthalene was enhanced to different degrees when anoxic sediment was oxidized. Laboratory experiments showed that natural dissolution/precipitation cycling of manganese or iron oxide could not explain either changes in sorption with time or differences between anoxic and oxic sorption. Sediment amended with manganese oxyhydroxide at forty times background values showed a slight increase in adsorption. Iron oxyhydroxide amendment showed no effect. This study also addressed potential problems inherent to slurry sorption experiments such as the use of biocide and the effect of slurry solid to water ratio. Using HgCl2 as a biocide did not markedly affect lysine sorption. Although slurry ratio of solid to water did affect distribution coefficients, normalization of distribution coefficients to slurry porosity provides a meaningful way to report sorption and results in relatively constant estimates of adsorption capacity when using slurries of variable ratios of total suspended solid to water.

Importance of suspended participates in riverine delivery of bioavailable nitrogen to coastal zones

Total nitrogen (TN) loadings in riverine sediments and their coastal depocenters were compared for 11 river systems worldwide to assess the potential impact of riverine particulates on coastal nitrogen budgets. Strong relationships between sediment specific surface area and TN allow these impacts to be estimated without the intense sampling normally required to achieve such budgets. About half of the systems showed higher nitrogen loadings in the riverine sediments than those from the coastal depocenter. In spite of uncertainties, these comparisons indicate that large, turbid rivers, such as the Amazon, Huanghe, and the Mississippi, deliver sediments that in turn release significant or major fractions of the total riverine nitrogen delivery. Riverine particulates must therefore be considered an essential factor in watershed nutrient loading to coastal ecosystems and may affect delivered nutrient ratios as well as total nutrient loading. The relative importance of particulate versus dissolved delivery has decreased over recent decades in the Mississippi as a result of damming and fertilizer use in the watershed.

Sedimentological and Surface Characteristics of the Northern and Central Adriatic Sediments

The results of this investigation reveal mutual relationship between some sedimentological and surface chemical characteristics, such as granulometric and mineral composition, specific surface area (SSA) and organic matter content, of northern and central Adriatic surface sediments. Grain size distribution and mineral composition enabled the reconstruction of the sedimentation pattern in the northern and central Adriatic Sea. It was shown that sands are spread in the east, along the Croatian coast. Toward the west, the share of finer sediments increases, so that the western region (parallel to the Italian coast) is covered with pelites. Such a pattern is typical for the northern Adriatic and the 401-407 profile of the central Adriatic. Most of the central region is covered with pelites. Granulometric and mineral composition are interrelated, indicating that sediments having more clay minerals (aluminosilicates) are always fine-grained, while coarser sediments contain more quartz and carbonates. The SSA and organic matter content are dependent on the grain size and mineral composition - fine-grained clay minerals have larger SSA’s and contain more organic matter attached to their surface. These organic substances influence considerably the SSA of sediments. It was noted that, after removing the organics, the SSA of sediments changed. This indicates that, effecting the SSA of sediments, organic matter effects their adsorptive ability.

Retention of riverine iron in estuaries

Retention of Fe flocs, resulting from the mixing of river water and seawater, was examined in three Maine estuaries. Riverine Fe was found to remain fairly conservative with salinity, implying that the process of floccufation does not necessarily remove Fe from water parcels. Laboratory experiments corroborated the field data by demonstrating that neither gravity nor suspended sediment were very effective in removing flocculated Fe from suspension. However, input of a tannery effluent did appear to result in scavenging of Fe from estuarine waters. Flocculated riverine Fe was found to increase considerably the Fe concentrations of estuarine bottom sediments, with the amount of iron per sediment specific surface area dependent on mean river flow entering an estuary. While no long term retention efficiencies could be calculated for these estuaries, it seems likely that a significant portion of flocculated riverine Fe escapes to shelf waters.

Specific surface areas in coastal sediments: Relationships with other textural factors

Sediment specific surface area can be a controlling variable in sediment biogeochemistry, therefore a variety of granulometric techniques have been employed to infer relative and absolute surface areas in sediments. This study compares specific surface areas with other textural parameters for a suite of aluminosilicate sediments from the Gulf of Maine and contiguous estuaries. The intragranular porosity of sediment grains increases with grain size, and is probably due to varying relative contributions of nanometer and micrometer-sized pores. Poor sorting of sediments causes underestimation of absolute surface areas by geometrical calculation using measures of central tendency. Underestimation is worse in coarser estuarine sediments owing to a combination of increased roughness factors of coarser grains and poorer sorting. Relative surface areas among sediments may be accurately assessed by measuring the proportion clay or fine silt. Means and medians do not provide accurate estimation of relative surface areas unless the samples share similar sorting characteristics. An algorithm to predict absolute surface areas from grain-size distributions of Gulf of Maine sediments is presented.

Granulometric dependence of chromium accumulation in estuarine sediments in Maine

Variation of chromium concentrations with grain size in estuarine sediments comples use of a sediment textural indicator in examination of pollutant chromium distribution. Sediment specific surface area is shown to be superior to measurements of the proportion of fine-grained sediment in defining regional variations of chromium concentration with sediment texture in three relatively unpolluted estuaries. Mineralogy is the prime control on chromium levels in these estuaries. The application of a textural normalization technique using specific surface areas in an estuary receiving a chromium-rich effluent allows differentiation of polluted from nonpolluted sediments. Accumulation of effluent chromium occurs within the estuary, not in adjacent coastal sediments, and concentration occurs in intertidal rather than subtidal zones.