Chemical Composition Of Sediments Research Articles

Biogenic sediment regimes in the Neogene equatorial Pacific, IODP Site U1338: Burial, production, and diatom community

The equatorial Pacific experienced significant changes in productivity and microfossil assemblage since 16 million years ago (Ma). We compiled a record of those changes from IODP Site U1338 using a reconnaissance of diatom assemblages and high-resolution XRF-scan chemical profiles (1–2 kyr spacing). Productivity and CaCO 3 dissolution intervals are defined by sediment component ratios, in particular opal/clay opal/BaSO 4 and CaCO 3 /BaSO 4 or CaCO 3 /clay. There are large abrupt changes in export production in the Miocene, especially compared to the Pleistocene and Pliocene and average levels of export production are higher throughout the Miocene compared to the Pliocene and Pleistocene. Using diatom assemblages and bulk sediment composition, the U1338 sediment record is divided into several distinct deposition regimes: (1) a Middle Miocene Regime > 13.2 Ma marked by low diatom numbers and a few short-lived productivity intervals, (2) a Carbonate Crash Regime distinguished by an older substage (13.2–10.2 Ma) with relatively high abundances of productivity-related diatoms and common productivity-related depositional intervals interspersed with CaCO 3 dissolution intervals and a younger Carbonate Crash substage (10.2–8.0 Ma) with weaker brief productivity intervals, high CaCO 3 dissolution, and moderately high numbers of upwelling diatom species, (3) the Biogenic Bloom Regime (8.0–4.5 Ma) marked by extended periods of high opal and CaCO 3 deposition with a maximum between 7.0 and 6.4 Ma, and (4) a Pliocene–Modern Regime (4.5–0 Ma) with lower productivity and high cyclic CaCO 3 dissolution. Changes in production and dissolution result from reorganizations of nutrient supply to the equatorial Pacific, not by higher wind-driven upwelling. We propose that nutrients were more accessible in the Miocene because of a combination of factors including higher organic matter degradation in the upper water column and deep-intermediate nutrient pathways that efficiently recycled nutrients to upwelling zones. Closure of the Central American Seaway was likely a prime cause of the Biogenic Bloom. • XRF scanning measures sediment chemical composition and biogenic component%. • Elemental ratios track high export production intervals in the equatorial Pacific. • Diatom assemblage responds partly to production, partly to surface ocean properties. • Erratic large abrupt changes in export production mark middle Miocene Pacific. • Central American Seaway closure causes extended late Miocene Biogenic Bloom.

Determining riverine sediment storage mechanisms of biologically reactive phosphorus in situ using DGT.

Phosphorus (P) is the main reason many surficial water bodies in the UK are currently failing to meet the chemical standards set by the Water Framework Directive (WFD). This work focuses on the role of sediments in the upper reaches of the River Taw in the South West of the UK. Point and diffuse sources of P have been identified as well as a number of mitigation measures applied or planned to address the issues. However, it is unknown what effect these sources have had on the river's sediments and how they will react to diminishing inputs of P into the water column in the future. The diffusive gradient in thin-films (DGT) method is utilised in situ to quantify and identify labile, potentially bioavailable P fluxes and potential storage mechanisms at sites of known diffuse and point P inputs. In the vicinity of a heavily contaminated point source, data present here shows that sediments are still acting as a sink. The proposed mechanism for this is the formation of a 'calcium cap' which provides a geochemical barrier between the sediment and overlying water to prevent loss of labile P. The strong correlation between calcium and total P under most circumstances supports this hypothesis. This conclusion provides some confidence that even though P concentrations in some sediments are significantly elevated, mobility between the sediment and overlying water is restricted. In the context of routine monitoring against WFD targets, the molybdenum blue method generally employed to determine soluble reactive phosphorus was shown to not be equivalent to the DGT labile P pool, especially at pristine or moderately point/diffuse influenced sites. This is likely due to desorption of weakly bound P from colloids, which is unavailable to DGT devices. These results have the potential to be scaled up to the full catchment or other catchments which exhibit similar physical and chemical sediment composition and provide a stronger foundation for management and target setting than current monitoring approaches.

Skład Chemiczny Osadów Bagiennych z Doliny Luciąży (Torfowisko Bęczkowice na Równinie Piotrkowskiej)

AbstraktAnalizę geochemiczną przeprowadzono dla osadów organicznych z torfowiska Bęczkowice w środkowym biegu doliny rzeki Luciąża. Z profilu B-1, zlokalizowanego w południowej części doliny, pobrano do analiz geochemicznych 60 próbek osadów (do głębokości 3,00 m), reprezentujących 5-cm segmenty rdzenia. W próbkach tych oznaczono straty na prażeniu w temperaturze 550°C, informujące o zawartości materii organicznej oraz oznaczono pierwiastki o wymowie paleogeograficznej: Na, K, Mg, Ca, Fe, Mn i metale ciężkie: Cu, Zn i Pb. Stosując analizę skupień wydzielono sześć lokalnych poziomów geochemicznych (LGZ), różniących się istotnie pod względem składu chemicznego osadów. Dla serii osadów torfowych określono również związki korelacyjne pomiędzy analizowanymi metalami, a także materią organiczną oraz obliczonymi wskaźnikami geochemicznymi: Ca/Mg, Na/K, Na+K+Mg/ Ca, Fe/Ca, Fe/Mn, Cu/Zn, pozwalającymi na rekonstrukcję warunków akumulacji analizowanych osadów. W toku analizy składowych głównych zidentyfikowano 10 głównych czynników, z których wybrano trzy pierwsze PC1, PC2 i PC3, wyjaśniające łącznie 84,4% wariancji. Do czynników kształtujących skład chemiczny holoceńskich osadów organicznych w środkowej części doliny Luciąży zaliczono produktywność biologiczną ekosystemu torfowego, procesy denudacji chemicznej i mechanicznej w zlewni (zwłaszcza dostawę allochtonicznej materii mineralnej), wzrost udziału wód opadowych w bilansie wodnym torfowiska oraz działalność człowieka.

Skład Chemiczny Osadów Bagiennych Z Doliny Rawki (Torfowisko Kopanicha, Równina Łowicko-Błońska)

AbstraktAnalizę geochemiczną przeprowadzono dla osadów organicznych z torfowiska Kopanicha w dolinie środkowej Rawki. Z profilu Kop-1, zlokalizowanego w centralnej części mokradła, pobrano do analiz geochemicznych 59 próbek osadów (do głębokości 3,1 m), reprezentujących 2,5-cm segmenty rdzenia. W próbkach tych oznaczono straty na prażeniu w temperaturze 550°C, informujące o zawartości materii organicznej oraz oznaczono pierwiastki o wymowie paleogeograficznej: Na, K, Mg, Ca, Fe, Mn i metale ciężkie: Cu, Zn i Pb. Stosując analizę skupień wydzielono siedem lokalnych poziomów geochemicznych (LGZ ), różniących się istotnie pod względem składu chemicznego osadów. Dla serii osadów torfowych określono również związki korelacyjne pomiędzy analizowanymi metalami, a także materią organiczną oraz obliczonymi wskaźnikami geochemicznymi: Ca/Mg, Na/K, Na+K+Mg/ Ca, Fe/Ca, Fe/Mn, Cu/Zn, pozwalającymi na rekonstrukcję warunków akumulacji analizowanych osadów. W toku analizy składowych głównych zidentyfikowano 10 głównych czynników, z których wybrano trzy pierwsze - PC 1, PC 2 i PC 3, wyjaśniające łącznie 78,98% wariancji. Do głównych czynników kształtujących skład chemiczny holoceńskich osadów organicznych w dolinie Rawki zaliczono sorpcję metali przez materię organiczną i uwodnione tlenki żelaza, zmienność akumulacji minerałów ilastych w środowisku sedymentacyjnym, warunki oksydacyjno-redukcyjne oraz działalność człowieka.

Preventing the formation of scaling in the water cycle

The problems of scaling in the cooling equipment of synthetic ammonia production. Theoretical and experimental study on the choice of a method of preventing the formation of scale (scale formation). Shows a diagram of connections with anti-scale methods of thermal resistance, given the physico-chemical phenomena at the ground level of functioning of chemical engineering systems and properties of water-technological system (PTS). Selected reagent method using complexing to control scaling in heat exchange equipment at low degrees of supersaturation crystallizing systems. The boundaries and applicability of formal statistical models in the description of the Cree-crystallization of sparingly soluble salts from solutions through the formation of the nuclear complex. On the basis of theoretical and experimental studies determined the dose and conditions of entry-hydroxyethyl reagent denfosfonovoy acid (HEDP) and its zinc complex Zn-HEDP in vodoobo-cycle company commander in the production of synthetic ammonia (branch "Nitrogen" of "UCC" URALCHEM"). Presents chemical compositions of sediments and the results of processing the back of the cooling water solutions HEDP, which increased performance capacitor turbocharger syngas to normative values.

Major factors influencing the elemental composition of surface estuarine sediments: The case of 15 estuaries in Portugal

Upper sediments (0–5cm) were sampled in 94 sites of water bodies of the fifteen Portuguese estuaries characterized by distinct settings of climate, topography and lithology, and marked by diverse anthropogenic pressures. Confined areas recognized as highly anthropogenic impacted, as well as areas dominated by erosion or frequently dredged were not sampled. Grain size, organic carbon (Corg), Al and trace elements (As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn) were determined. Normalisation of trace element concentrations to Al and Corg, correlations between elements and Principal Component Analysis (PCA) allowed identifying elemental associations and the relevance of grain-size, lithology and anthropogenic inputs on sediment chemical composition. Whereas grain-size is the dominant effect for the majority of the studied estuaries, the southern estuaries Mira, Arade and Guadiana are dominated by specific lithologies of their river basins, and anthropogenic effects are identified in Ave, Leça, Tagus and Sado. This study emphasizes how baseline values of trace elements in sediments may vary within and among estuarine systems.

Effects of grain size distribution on mineralogical and chemical compositions: a case study from size‐fractional sediments of the Huanghe (Yellow River) and Changjiang (Yangtze River)

The influence of hydrodynamics on the chemical composition of sediments is based on the uneven distribution of element abundances in different size fractions. In this study, 72 size‐fractional sediments from the Huanghe (Yellow River) and Changjiang (Yangtze River) riverbeds were measured with XRD, SEM, ICP‐AES and ICP‐MS. The analysis results show that the mineral and chemical characteristics change with grain size in the Huanghe and Changjiang sediments. According to the principal components analysis, three independent geochemical factors were found. The first factor elements, Zr, Hf, Th, U, Y, La and TiO2 are influenced by the existence of heavy minerals. The second factor elements, Al2O3, alkalis, alkaline earth (excluding Ca and Sr) and most of the transitional metals are dominated by clay minerals. The third factor group includes Ca and Sr, which were controlled by calcium‐bearing mineral contents and chemical weathering intensities. The various grain size distributions greatly affect the mineralogical and chemical compositions of bulk sediments. Compared to other size fractions, the 5–6PHI size fractions of the Huanghe and Changjiang sediments have special mineralogical and chemical compositions, and intermediate volume percentages. Weight or volume percentage of each size fraction may be more suitable than mean grain‐size of the bulk sediment to elucidate the grain size effects. Chemical Index of Alteration (CIA) values increase steeply with decreasing grain size, while Weathering Index of Parker (WIP) values are relatively stable. Because of the big influence of the abundance of clay minerals on CIA values, it is questionable to use CIA as a proxy of weathering intensity. Considering the clay mineral effects, stability in values and heterogeneous material properties, WIP has the potential to indicate the chemical weathering intensity of sediments. Copyright © 2014 John Wiley & Sons, Ltd.

Chemical composition of sediments in Baikal deep-water boreholes as a basis for reconstructions of climatic and environmental changes

Earlier reconstructions of climatic and environmental changes from data of deep-water drilling on the Akademichesky Ridge in Lake Baikal were based both on the content of biogenic silica or the abundance of diatom valves and on the results of X-ray diffraction (XRD) analysis of the sediment mineralogy. It was established that clay minerals are the main carrier of information about climatic variations in a drainage basin. The content of biogenic silica strictly correlates with two chrystallochemical parameters: the abundance of smectite beds in illite–smectite and the abundance of illite. However, detailed analysis of clay minerals calls for exclusive XRD techniques without mass determination of minerals in the sediments of long Baikal cores. We propose a new approach to determine the mineral composition of bottom sediments, based on their chemical composition. We compared the average chemical compositions of Pleistocene, Pliocene, and Miocene core sediments from the boreholes BDP-96 and BDP-98 and sediments of the Paleo-Barguzin River avandelta and recognized groups of chemical elements marking warm and cold climatic periods. However, the difference in the chemical compositions of sediments in warm and cold periods is insignificant. Since an XRD analysis of mineral composition is usually performed for short time intervals, it was necessary to identify cold and warm intervals by the mineral composition calculated from the chemical composition of sediments. The mineral contents were estimated using the Selektor software. Based on the average contents of chemical elements, we computed the mineral composition of the bottom sediments throughout the BDP-98 section and studied its warm and cold periods. We have established that feldspars weakly respond to climatic changes, their contents show minor variations in warm and cold epochs, whereas the contents of mica minerals change seriously. Thus, clay minerals, together with biogenic silica, are a good indicator of paleoclimatic environmental changes.

Ground/satellite observations and atmospheric modeling of dust storms originating in the high Puna‐Altiplano deserts (South America): Implications for the interpretation of paleo‐climatic archives

AbstractThis study provides a detailed description of the sources, transport, dispersion, and deposition of two major dust events originating from the high‐altitude subtropical Puna‐Altiplano Plateau (15–26°S; 65–69°W) in South America. A long and severe drought provided the right conditions for the onset of both events in July 2009 and 2010. Dust was transported SE and deposited over the Pampas region and was observed to continue to the Atlantic Ocean. Dust monitoring stations located downwind recorded both events, and samples were characterized through chemical and textural analysis. Through a combination of meteorological data and satellite observations (CALIPSO and MODIS detectors), we estimate the emission flux for the 2010 event. This estimate was used to constrain the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) transport model and simulate the dust event. Both satellite imagery and model results agree in the location and extension of the dust cloud. CALIPSO detected dust between ~6000 and ~8500 m a.s.l., which remained at this height during most of its trajectory. The dust cloud mixed with a strong convective system in the region, and the associated precipitation brought down significant amounts of dust to the ground. Dust particle size analysis for both events indicates that near the sources dust samples show median modes of 12.4–14.1 µm, similar to modes observed 1300 km away. Chemical composition of sediments from potential dust sources shows distinct signatures within the Puna‐Altiplano Plateau, the Puna sector being clearly different from the Altiplano area. In addition, both sources are markedly different from the Patagonian chemical fingerprint. These results have important implications to improve the interpretation of paleo‐environmental archives preserved on the Argentine loess, Antarctic ice cores, and Southern Ocean marine sediments.

Sediment Contamination in Lyons Creek East, a Tributary of the Niagara River: Part I. Assessment of Benthic Macroinvertebrates

Sediments in Lyons Creek East (Welland, Ontario), a tributary of the Niagara River and part of the Niagara River Area of Concern, which exceed screening-level environmental-quality criteria for multiple contaminants, were assessed for biological impacts using information from multiple lines of evidence. An initial chemical survey indicated the primary contaminants of concern to be polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), zinc, and p,p'-DDE due to frequent exceedences of sediment guidelines. A subsequent study focused on the chemical composition of sediment, status of benthic invertebrate communities, contaminant bioaccumulation in resident benthos, and sediment toxicity to laboratory-exposed organisms. Chemical and biological conditions in the creek were compared with those in reference creeks using both multivariate (cluster analysis and ordination) and univariate (regression) techniques. Sediment PCBs (≤ 19 μg/g), PAHs (≤ 63 μg/g), and Zn (≤ 7969 μg/g) were increased above the sediment-quality guidelines along most of the creek; however, the upper 1.5 km portion of the creek was the most highly contaminated and therefore the main focus for biological study. Although severe toxicity was evident at several locations in the upper creek, resident benthic communities were minimally affected by sediment contamination. The cause of toxicity was likely related to a combination of stressors, including PCBs, PAHs, and metals. Due to its biomagnifiable nature, bioaccumulation focused on PCBs; concentrations in resident macroinvertebrates were ≤ 2 orders of magnitude greater than those found in reference creeks and were above tissue residue guidelines, indicating a potential risk for consumers of benthos. This risk was not limited to the upper 1.5 km where other effects were seen.

Characteristics of bottom sediments of Lake Widryńskie

AbstractThe aim of this study was to determine the chemical composition of Lake Widryńskie bottom sediments (max. depth. 27.0 m, area 123.9 ha). The sampling of bottom sediments was conducted once, on 16 August 2010. Sampling was made in 10 specific areas. Among the 10 samples, 4 samples were taken from the littoral and sublittoral zones, while the rest were taken from the profundal zone. The dominant component of the sediments was silica and calcium carbonates were subdominant. Based on the survey, it was determined that silica occurred in greater numbers in littoral sediments, while in sublittoral sediments there was increased participation in the chemical composition of organic matter. The elements that build a capacity complex were a small percentage of the dry weight of sediment. Sediment from the vicinity of inflows contains higher amounts of silica, which confirmed the impact of the catchment on the chemical composition of sediments.

Geochemical Assessment of a Subtropical Reservoir: A Case Study in Curitiba, Southern Brazil

AbstractSuspended particles and dissolved substances in water provide reactive surfaces, influence metabolic activity and contribute to the net sediment deposition. It therefore plays an important part in the ecology and quality of the water mass. The water quality in reservoirs is crucial and it is naturally maintained by flushing and sedimentation, which continuously remove phosphorus from the water. In some reservoirs, however, these removal processes are countered by recycling of ions which could play a key role to start and/or maintain the eutrophic state. The combination of macro‐, trace‐ and microanalysis techniques can be useful to trace pollution sources through a chemical fingerprint, whether be during an acute environmental disaster or a long‐term release of pollutants. The water quality and total metal content of reservoir sediments were assessed in a reservoir, situated in the capital of the Paraná State, in the South‐Eastern part of Brazil. The goal of this paper was to determine the metal presence in the sediment and metal and ionic speciation in the Green River reservoir water. Water and bed sediment samples, collected from various sites during 2008 and 2009, were investigated using XRF, ICP‐OES, ICP‐MS, XRD and zeta potential measurements. Based on the results, the heavy metal concentration and chemical composition of the suspended matter in the water samples, as well as the sediment's chemical composition will be discussed.

How important is it to integrate riverine suspended sediment chemical composition with depth? Clues from Amazon River depth-profiles

The vertical variability in mineralogical, chemical and isotopic compositions observed in large river suspended sediments calls for a depth-integration of this variability to accurately determine riverine geochemical fluxes. In this paper, we present a method to determine depth-integrated chemical particulate fluxes of large rivers, based on river sampling along depth-profiles, and applied to the Amazon Basin lowland tributaries. The suspended particulate matter (SPM) concentration data from depth-profiles is modeled for a number of individual grain size fractions using the Rouse model, which allows to predict the grain size distribution of suspended sediment throughout the whole river cross-section. Then, using (1) the relationship between grain size distribution and the Al/Si ratio (2) relationships between the Al/Si ratio and the chemical concentrations, the chemical composition of river sediment is predicted throughout the river cross-section, and integrated to yield the depth-integrated chemical particulate flux for a number of chemical elements (e.g. Si, Al, Fe, Na, REEs, …). For elements such as Al, Fe, REEs, Th, the depth-integrated flux is around twice as high as the one calculated from river surface sample characteristics. For Na and Si, the depth-integrated flux is three times higher than the “surface” estimate, due to the enrichment of albite and quartz at the bottom of the river. Depth-integrated 87Sr/ 86Sr composition of suspended sediment, also predictable using this method, differs by more than 10 −3 from the surface sample composition. Finally, potential implications of depth-integrated estimates of Amazon sediment chemistry are explored. Depth-integration of particulate 87Sr/ 86Sr isotopic ratios is necessary for a reliable use of Sr isotopes as a provenance tracer. The concept of steady-state weathering of a large river basin is revisited using depth-integrated sediment composition. This analysis shows that, in the Amazon Basin river, the previously observed discrepancy between (1) weathering intensities of channel surface sediment and (2) silicate-derived dissolved fluxes is only slightly accounted for by the vertical variability of suspended sediment weathering intensities. This observation confirms that most large rivers basins are not eroding at steady-state.

Chemical composition of sediments from marine shallow-water hydrothermal mounds in Wakamiko submarine crater revealed by multiple prompt gamma-ray analysis

Multiple prompt gamma-ray analysis (MPGA), a new radionuclide quantification method with high energy resolution, was applied to sediments from a marine shallow-water hydrothermal mound. Surface sediments around mounds were collected from the Wakamiko submarine crater located in Kagoshima Bay, southwest Japan, where the hydrothermal system was different from those at other marine shallow-water hydrothermal mounds. All samples were desalted and MPGA measurements were performed for 4,500 s (real time). Event data were obtained using eight Canberra-Eurisys CLOVER Ge detectors. The size of the list data that included all multiple events was from 1.19 to 19.2 GB. We could obtain concentrations of 32S, 55Mn, 75As, 157Gd, 39K, 149Sm, 56Fe, and 85Rb with high sensitivity by MPGA. Furthermore, 32S, 85Rb, and 55Mn have characteristic concentrations only at a mound, not at control sampling sites, suggesting that sediments were sulfurated by magmatic fluids at this mound.

Composition and formation conditions of sediments in the Doroninskoe soda lake (eastern Transbaikalia)

It has been established that the southern and eastern parts of the Doroninskoe soda lake bottom with the depth less than 4–4.5 m are mainly composed of micrograined quartz-feldspar sand. Silty-clayey kaolinite-hydromica particles predominate from the depth more than 4–4.5 m. Low maturity of clastic material and its insignificant role in the formation of soda minerals in the lake have been established. Very high concentrations of Cl and Na, as well as high concentrations of S and P, are specific characteristics of the chemical composition of sediments. Distribution of chemical elements is governed by a complex action of the mechanical, alkaline, sorption, and hydrosulfuric barriers. With increasing depth and distance from the shore, concentrations of Ti, Ce, Na, Mn, La, Ca, Co, and Cu increase by 3–3.5 times; Fe, P, V, and Zn, by 4.5–5 times; Mg, Ni, and Cr, by 6–7.5 times; and Cl and S, by 10–15 times. The sharp increase in the contents of Ti, Fe, Mn, Ce, and La is related to the formation of zircon-ilmenite placer horizons. Concentrations of Si, K, and Ba show negative correlation with the psammite component. The Pb content does not depend on the barrier factor.

Abrupt change of sediment records in the southern South China Sea during the last glacial period and its environment significance

Chemical compositions of sediments at core NS07-25 (6°39.945′N, 113°32.936′E; water depth 2006 m) are analyzed to discuss abrupt change of sediment records in the southern South China Sea (SCS) during the last glacial period and its environmental implications. Major and trace elements experienced three significant changes, which occurred at 31.9, 26.1 and 18.5 ka BP respectively. At 31.9 ka BP when sea-surface temperature remained relatively low, terrigenous sediment flux increased but biogenic activities weakened greatly. At 26.1 ka BP, both terrigenous sediment flux and biogenic fractions number were steady. However, some elemental ratios changed noticeably at that time. Before 26.1 ka BP, core sediments with low Nb/Ta but high Zr/Hf ratios were mainly derived from the paleo-Mekong and/or Molengraaff Rivers exposed on the Sunda Shelf at that time. After 26.1 ka BP, sediments with high Nb/Ta but low Zr/Hf ratios probably relate to strengthened impact of deep water current. Since 18.5 ka BP, sea level ascended rapidly from ∼110 m below the present, terrigenous sediment flux decreased and biogenic activities strengthened continuously, probably related with the East Asian monsoon evolution.

Reconstruction of human influence during the last two centuries on two small oxbow lakes near Warsaw (Poland)

Short sediment cores from two small oxbow lakes located in the Vistula valley near Warsaw (Poland) were analysed for chemical composition and zooplankton (Cladocera) remains. The results of these analyses were evaluated using ordination techniques and the results were used to reconstruct the history of human impact of the lakes. The cores were dated using the 210Pb method. These analyses show that the collected sediments (60 cm- and 67 cm-long-cores) were deposited during the last 150–200 years. Cladocera assemblages were different in the two lakes; however, Bosmina longirostris was dominant among subfossil Cladocera species in both lakes. The presence of this species indicates the high trophic state of the lakes. Changes in Cladocera species composition suggest that a significant increase in the lakes’ trophic levels has occurred since the 1920s. The change could be related to the construction of flood dikes along the river Vistula, the isolation of the studied lakes from the river, changes in land use, or some combination of these factors. The chemical composition of sediments, particularly the increase in phosphorus and sulphur concentrations, confirms that the construction of dikes against flood was the major factor inducing eutrophication of the oxbow lakes. This study shows that the Warsaw small water bodies are especially sensitive to local disturbances caused by human activity, mainly water management, land use changes and agriculture.

Estimation of the sources of pelagic sediments from the South Pacific Ocean to the Antarctic Ocean

In order to estimate the source in pelagic sediments, principal component analysis (PCA) was applied to the data matrix which was made by chemical compositions of sediments measured by instrumental neutron activation analysis (INAA) and prompt gamma-ray analysis (PGA). The results of PCA represented 3-factor models in each sediment, explaining 58–98% of the total variations in the sediments. A comparison of eigenvectors of terrigenous elements indicated the existence of 2 sources. Group 1 is suggested to be continental dust, whereas Group 2 is suggested to be volcanic rock. Variation of K/Ti ratio and Eu anomaly of sediments supported the above results.

Chemical and mechanical erosion rates in Iceland as deduced from river dissolved and solid material

This study investigates dissolved, suspended loads and sands of major Icelandic rivers and determines chemical and mechanical erosion rates as well as rates of CO₂ consumption by the chemical weathering. A steady state model of erosion is used to locally calculate the river suspended load fluxes needed to balance chemical weathering. The total dissolved solid concentrations range from 20 to 179 mg/kg. The highest concentrations are for spring fed rivers draining young rocks in the vicinity of active volcanoes, and the lowest for direct runoff rivers draining old Tertiary rocks. Total dissolved loads, “corrected” for atmospheric, geothermal, and magmatic inputs are used together with mean annual discharges to estimate low-temperature chemical erosion rates of 16 to 111 t/km²/yr. These rates increase with runoff but decrease with the age of the rocks. Icelandic chemical erosion rates are higher than the world average for silicate rocks, reflecting both high reactivity of the basalt and high runoff, but lower than those for other basalt-draining rivers (in Réunion, Java, Azores or Deccan). CO₂ consumption rates associated to chemical denudation range between 0.18 and 2.12 10⁶ mol/km²/yr with an average value of 0.74 10⁶ mol/km²/yr, higher than the world average for rivers draining silicate rocks. Chemical compositions of suspended sediments and sands are similar, showing a very low weathering stage. The elements most soluble during the weathering show slightly lower concentrations in the suspended sediments. River sediment chemical compositions are assumed to reflect a mixture between 3 initially pristine rock end-members: high Mg-basalt, tholeiite and rhyolite. The most insoluble elements (REE and Th) are used to re-define the mean chemical composition of the initially unaltered rocks of each drainage basin. A mass budget between the unaltered rock of the catchments and the river dissolved and suspended loads (steady state model of erosion) is used to calculate the average annual solid load of the rivers, which range from 650 to 4300 mg/l. For some rivers there is a good agreement between calculated and measured suspended loads but for others the calculated load is much higher than the measured one. The difference stems from groundwater inputs, man-made dams and other sedimentary traps. If the relevancy of the steady state model of erosion can be questioned, the accuracy of sediment load measurements is also questionable. Pros and cons of both methods are argued. The calculated solid loads lead to very high mechanical erosion rates, ranging from 940 to 10200 t/km²/yr. Those increase with the glacier cover but decrease with the age of the catchment rocks. Icelandic mechanical erosion rates rank among the maximum reported rates, underscoring the importance of glaciers, tectonics, glassy basaltic rocks and high runoff. In association with low chemical weathering rates, these place Icelandic rivers as an end-member in the observed anti-correlation between mechanical to chemical erosion ratios and temperature for volcanic islands.

Characterising physicochemical sediment conditions at selected bacterial decayed wooden pile foundation sites in the Netherlands, Germany, and Italy

We investigated the relationship between wood degradation caused by erosion bacteria and the physicochemical properties of foundations with wooden piles from sites in the Netherlands, Germany, and Italy. Wooden foundation piles have been widely used to stabilise urban settlements along coastal areas and river sites for several millennia. Recently a number of these buildings have suffered from structural instability because their foundations have suddenly lost supporting strength. This loss of strength has been associated with the activity of erosion bacteria that can colonise and destroy wood under low-oxygen conditions, such as those that exist below the groundwater level. Knowledge of bacterial species involved in this process and their growth requirements is sparse, but it has been documented that the damage to wooden foundation piles caused by these bacteria can occur relatively rapidly. Redox potential (platinum electrodes) measurements, sediment, and sedimental water samples were obtained from nine European sites. Sediments were characterised and analysed for total contents of carbon, nitrogen, sulphur, phosphate, and major cations, whereas sedimental water was analysed for pH, conductivity, total and dissolved carbon and nitrogen, NH 4 + , NO 3 - , SO 4 2 - , PO 4 3 - , Cl - , and major cations. The chemical sediment composition was governed mainly by sediment type (sand, clay), whereas sediment water composition reflected the exposure to sea or freshwater and the redox status of the sampling location. Bacterial wood decay was detected at all sites but with different magnitude orders reflecting the different environments. When the physicochemical properties of sedimental water from foundations in sandy sediments were compared with wood degradation levels, it was observed that decreasing total nitrogen concentration, but not that of phosphate, accompanied increasing bacterial wood decay.