A gravity core (220 cm depth) was collected to investigate the geochemistry, enrichment, and pollution of trace metals in anoxic sediments from San Simon Bay, an ecosystem of high biological ...productivity in the northwest of Spain. A five-step sequential extraction procedure was used. The Cu, Pb, and Zn contents decreased with depth, with maximum values in the top layers. Ni and Zn were bound to pyrite fractions, while Cd and Pb were associated with the most mobile fractions. The analyzed metals were associated with the fractions bound to organic matter, mainly with the strongly bound to organic matter fraction. High Cd and Cu values were observed. The fractionation showed a high mobility for Cd (28.3–100%) and Pb (54.0–70.2%). Moreover, the pollution factor and the geoaccumulation index reflected a high contamination for Pb and a moderate contamination for Cu and Zn in the superficial layers, pointing to a possible ecotoxicological risk to organisms in San Simon Bay.
Two sedimentary sequences (coastal and subtidal) were studied in San Simón Bay (Ría de Vigo), situated on the Atlantic coast of NW Iberia. The coastal record is a shallowing upward sequence which ...evidences a locally-developed low marsh, situated below the current beach, and dated at the second half of the 4th century. During the following decades this low marsh was progressively replaced by an alder swamp which formed on it. This suggests an apparent stabilisation or slow-down of the relative sea-level (RSL), in this site, at the beginning of the Dark Ages (DA). The subtidal sequence studied reflects the main changes in the landscape, the hydrological conditions, climate and RSL affecting this part of NW Iberia during the last 1250 years. Evidence of changing dinocysts content in the sediment reveals that two centennial or decadal-scale episodes existed of shelf marine waters more intensely penetrating inside the bay: between the 15th-18th centuries and at ca 1800–1930 AD. Besides, we related different proxies with the occurrence of four main climatic stages, namely the previously described Dark Ages (DA, ca 350–750 AD), the Mediaeval Climatic Anomaly (MCA, ca 750–1100 AD) and the Little Ice Age (LIA. ca 1500–1930 AD); in addition we propose a regional MCA/LIA transition (ca 1100–1500 AD) that it has not been previously described. Our environmental characterization indicates a persistent North Atlantic Oscillation (NAO) negative mode domain in Ría de Vigo during the MCA, but this became weaker during the LIA and, probably, also during the earlier DA. NAO mode become more irregular during the MCA/LIA transition, generally persisting in dominant negative mode except for a phase of minor upwelling intensification, at ca 1150–1350 AD, which mainly affected the external parts of the ria. We postulate that an almost simultaneous phase (ca 1100–1350 AD) of stronger continental contribution in the sediments may be related to increasing storm intensities, probably linked to a reinforcement of the Easter Atlantic (EA) pattern; and also that the intertidal/supratidal ecosystems inside San Simón Bay may have extended further in the past, at least towards the end of the 5th century, and between ca 1050–1350 AD and ca 1450–1750 AD. A number of local historical references are consistent with our palaeoecological data and so support the chronology proposed as well as many of the environmental changes reconstructed. This good agreement will help in the interpretation of other analogous sequences extending back in time.
•Pollen and geochemical analyses were performed in coastal and subtidal sediments.•Pollen stratigraphy, radiocarbon dates and historic evidence provided a chronology.•Landscape dynamics and hydrological conditions were inferred from biological data.•A stabilisation or slow-down of the RSL occurred at the beginning of the Dark Ages.•Climate dynamics is reviewed from a complete series of well-characterized NAO modes.
Ría de Vigo is a river valley flooded by the sea, with a bay (San Simón Bay) at its innermost part. The accumulation of Holocene sediment in San Simón Bay has been studied by the integration of 1) ...large scale high resolution seismic data, and 2) detailed geochemical analysis of a gravity core. In San Simón Bay the majority of the seismic records are obscured by acoustic turbidity which represents gassy sediments, but on records from Rande Strait it is possible to distinguish two Quaternary seismic sequences; an Upper Pleistocene sequence (SQ1) and a Holocene sequence (SQ2). Only SQ2 is recognized in San Simón Bay where it is comprised of two seismic units; the upper unit represents the HST sediment, i.e. the period of highest sea level. A gravity core taken within the gassy zone at 10 m water depth provided 3.55 m of fine-grained sediments (muds) from the youngest seismic unit (4 m thick). Geochemical analysis show high values (4 to 10%) of TOC. Sediment and porewater analyses indicate a distinct sulphate–methane transition zone (SMTZ) between 60 and 80 cm where sulphate is depleted (to <1.7 mM) and methane increases (to >0.4 mM). The top of the acoustic turbidity (the gas front) at 80 cm corresponds to the lower limit of the SMTZ. The methane cannot have been derived from the underlying metamorphic and granitic rocks, but was probably derived by microbial degradation of the organic matter in the Holocene sediments. We estimate that the sediments of the Bay contain approximately 1.8 × 10
6 m
3 of organic carbon and 275 ton of methane.
This book, entitled “Elemental Concentration and Pollution in Soil, Water, and Sediment”, presents an updated overview of the main trace elements in living organisms. This collection brings ...researchers from different fields together, including those from biogeochemistry and ecotoxicology in various environmental media, in order to provide a more comprehensive understanding of the environmental fate of trace elements in their biogeochemical cycles for different ecosystems.
The Gila River and its tributaries in southern Arizona and adjoining states incorporate several dozen individual extensional basins of the central Basin and Range province into a single integrated ...drainage network. Forty basins in the Gila domain contain more than 1000m (maximum ~3500m) of post-12Ma basin fill. Subsurface evaporites in many basins document internal drainages terminating in isolated playa lakes during early phases of basin history. The nature of intrabasinal and interbasinal divides and of eroded or sedimented stream passages through mountain ranges intervening between the basins reveal the geomorphic mechanisms that achieved drainage integration over late Miocene to early Pleistocene time. Drainage integration accompanied by headward erosion eastward toward Gila headwaters was a response to Miocene opening of the Gulf of California, into which the Gila River debouched directly before the Pliocene (<5Ma) lower course of the Colorado River was established. Residual basins of internal drainage where headward erosion has not yet penetrated into basin fill are most common in the easternmost Gila domain but also persist locally farther west. Most basin fill was dissected during drainage integration within the upstream Gila domain but continued accumulation of undissected basin fill by sediment aggradation is dominant in the downstream Gila domain. Basin dissection was initiated by Pliocene time in the central Gila domain but was delayed until Pleistocene time farther east. In the westernmost Gila domain, interaction with erosional and depositional episodes along the Colorado River influenced the development of Quaternary landscapes along the tributary Gila River. The sedimentary history of the Gila drainage network illustrates the means by which trunk rivers can establish courses across corrugated topography produced by the extensional rupture of continental blocks.
•The Gila River integrates drainage through 550km of block-faulted basins and ranges.•The Gila domain includes forty sedimentary basins with more than 1000m of basin fill.•Bedrock canyons and sediment ramps connect basins through intervening mountain ranges.•Areal patterns of dissected and undissected basin fill record Gila geomorphic history.•Regional headward erosion over time gradually integrated the Gila drainage network.
The concentrations of both major and trace elements in San Simón Bay's subtidal sediments were determined for the purposes of (1) evaluating the influence of anthropogenic activities on metal content ...(against pre-anthropogenic background values attained via the deepest core samples), (2) establishing the subtidal sediments' degrees of pollution in recent decades, and (3) determining the influence of mussel raft systems on the composition of bottom sediments. Subtidal sediments consist of laminated, organic-rich, fine-grained sediments with low carbonate content and a notable presence of gas in their lower part. The recent sedimentary record revealed pollution, mainly from Pb and Cu, rising toward the sediment surface. The sources of various heavy metals were accordingly identified, with the application of Principal Component Analysis to discriminate among the different metal sources. It has been found that the mineralogy of the catchment area determines the overall composition, whereas biogenic production and anthropogenic activities contribute to the total metal content. At the same time, mariculture influences the composition of underlying sea bottom sediments, by changing the inorganic carbon content. Finally, evidence is provided to show how sediment composition is tied mainly to aquaculture and watershed characteristics via conditioning by anthropogenic activities.
The subtidal sediments of the inner Ría de Vigo (NW Spain) are fine-grained, rich in organic matter, and accumulate at rates of around 3 mm/yr. Redoxomorphic pyrites formation was studied in four ...sediment cores. Four operationally-defined iron fractions were determined (HCl-extracted, silicate-bound, organic and pyritic), and the dimensions and morphology of pyrites (which mainly occurred as isolated framboids 3–5 μm in diameter) were studied by SEM. Sediment appearance and degree of pyritization (DOP) identified an oxic zone limited to the top few millimetres, a suboxic zone that in most cores was just a few decimetres thick (the exception was a core obtained in an area of strong turbulent currents), and an underlying anoxic zone with DOP values of around 60%. Pyritic iron increased at the expense of the HCl-extracted fraction in approximately the top metre, but no further pyrite formation occurred at greater depths. Pyrite formation in these lower levels was not limited by lack of either HCl-extracted iron or metabolizable organic matter, but apparently by lack of sulphate ion, the diffusion of which to these depths was probably prevented by the fine texture of the sediments. Our findings highlight the interest of studying transitional sedimentary environments in order to explore in detail the geochemical parameters controlling pyrite formation.
Traditional artisanal Pecorino Siciliano (PS) cheeses, and two experimental PS cheeses were manufactured using either raw or pasteurised ewes' milk with the addition of starter cultures. The ...bacterial diversity and dynamics of the different cheese types were evaluated both by culturing and characterisation of isolates, and a culture-independent approach based on the 16S ribosomal RNA (rRNA) gene.
Following cultivation, artisanal and experimental cheese types showed similar microbial counts, and isolates belonging to
Lactococcus lactis,
Streptococcus thermophilus,
Enterococcus faecalis and
Leuconostoc mesenteroides were identified by phenotypic characterisation and comparison of the restriction fragment length polymorphism (RFLP) of the 16S rRNA gene to that of reference species. The culture-independent fingerprinting technique PCR and denaturing gradient gel electrophoresis (DGGE) of V6 to V8 regions of the 16S rRNA gene of samples taken during artisanal PS cheese manufacture, from raw milk to the ripened cheese, indicated relevant shifts in the microbial community structure.
The dominance of
Streptococcus bovis and
Lactococcus lactis species in the traditional artisanal PS was revealed by 16S rRNA gene sequencing. Comparison of DGGE profiles of samples from milk to ripened cheese, derived from artisanal procedure and the two experimental PS cheeses during production showed similar trends with the presence of intense bands in common. Nevertheless, the profiles of several artisanal cheeses from different farms appeared more diverse, and these additional species are probably responsible for the generally superior flavour and aroma development of traditional PS cheese.
San Simon Bay in northwestern Spain absorbs municipal and industrial wastes from the coastline, including a ceramic factory at the river moth. Metal concentrations and metal speciation were monitored ...in the bay and sediment samples, and traced to anthropogenic sources. Data are reported for Al, Fe, Mn, Cu, Pb, and Zn concentrations, as well as the detection limits for each.
The Ensenada de San Simón is the inner part of the Rı́a de Vigo, one of the major mesotidal rı́as of the Galician coast, NW Spain. The geochemistry of its surface sediments, and the river sediments ...which drain into it from a granitic and metamorphic hinterland, are described. Multivariate statistical analysis of the sediment compositions (using ridge regression and mixture-modelling) enabled the major- and trace-element distributions to be accounted for in terms of both natural and anthropogenic sources: Between 60 and 80% of the Cr, Cu, Ni, Pb and Zn concentrations of the bottom sediments of the Ensenada can be explained by sediment input from the combined R. Oitaben and R. Verdugo, the R. Redondela and faecal matter from mussel rafts, but there is additional enrichment towards the mouth of the Ensenada. This enrichment is attributed to marine water entering the Ensenada from the polluted industrial areas of the adjacent Rı́a de Vigo. It is suggested that these metals are carried landwards in solution by the tidal incursion of marine water (the volume of which, on an annual basis, greatly exceeds that contributed by the rivers). Although the incoming marine waters may also be important in supplying Pb to the outer Ensenada, this element may also be delivered by land run-off, or by windborne vehicular emissions to the Ensenada as a result of the surrounding network of roads and a road bridge over the Estrecho de Rande.
PDF
