Composition Of Suspended Particulate Matter Research Articles

The trace element composition of suspended particulate matter in the upper 1000 m of the eastern North Atlantic Ocean: A16N

Samples of total suspended matter were collected from the upper 1000m of the eastern North Atlantic between 62°N and 5°S during the CLIVAR/CO2 Repeat Hydrography section A16N from June to August 2003. Particulate matter samples were analyzed by energy-dispersive X-ray fluorescence for Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, and Pb. Intense seasonal deposition of Saharan dust produces maxima in particulate Fe (>3.3nM) and Al (>10nM) in surface waters between 10 and 20°N. A broad mid-depth enrichment of particulate Fe (>5.4nM) and Al (>19nM) between the equator and 20°N is sustained by vertical transport of lithogenic particles and scavenging of dissolved Fe released by remineralization. Surface distributions of particulate Fe and Al show maxima over a narrower, northerly shifted latitude range and are consistent with the seasonal location of atmospheric deposition associated with the Intertropical Convergence Zone, while the location of the mid-depth maximum reflects the full annual latitude range of surface inputs and suggests similar winter and summer atmospheric fluxes. Spatial offsets between surface maxima in particulate and dissolved Al distributions indicate relatively short residence times (8days and <1year, respectively) for both phases of Al in the equatorial Atlantic, and suggest that temporal sampling biases could have significant effects in models of dust deposition and surface-ocean chemistry. Efficient scavenging of dissolved Al by biogenic particles following the spring bloom in subpolar latitudes results in elevated mixed-layer particulate Al concentrations despite low aeolian inputs. A subsurface minimum in particulate Fe and Al concentrations at 50–200m throughout the transect likely results from efficient transport of lithogenic particles out of the surface layer by aggregation into large organic aggregates. Relative depletion of Fe in suspended particulate matter is observed in vertical profiles coincident with maxima in fluorescence and biogenic particle concentrations. At these depths, dissolved Fe increases from ~10–30% to 50–70% of the total Fe pool, suggesting a biological influence on the partitioning of Fe between particulate and dissolved forms. Metal-to-Al ratios indicate major anthropogenic sources for Cr, Ni, Cu, Zn, and Pb inputs to the surface ocean at latitudes outside of the low-latitude Saharan dust plume. Increased aerosol-Fe solubility in these regions likely contributes to relatively depleted Fe:Al ratios in surface-ocean particulates.

Biogeochemistry of near-bottom suspended particulate matter of the Beaufort Sea shelf (Arctic Ocean): C, N, P, δ 13C and fatty acids

The influence of the Mackenzie River on the source, composition, and distribution of dissolved nutrients and suspended particulate matter (SPM) in near-bottom waters on the Beaufort Sea shelf was determined by measuring particulate organic carbon (POC), particulate nitrogen (PN), particulate phosphorus (PP), elemental ratios (C:N, C:P, N:P), chlorophyll a, bulk δ13C, and fatty acids. The Mackenzie River had a strong influence on the composition of SPM in near-bottom waters across the entire Canadian Beaufort Sea shelf, including the Amundsen Gulf. This influence was strongest at stations near the river mouth and decreased offshore and northeastward towards the Amundsen Gulf, as seen in SPM elemental concentrations, δ13C, and terrestrial plant fatty acid markers. Low C:N ratios and high relative levels of odd-numbered carbon and branched-chained fatty acids (bacterial fatty acid markers) indicated that bacteria were an important contributor to organic matter at stations near the river and on the Mackenzie shelf. Fatty acid analysis allowed detection of a phytoplankton sinking event in the Amundsen Gulf in which polyunsaturated fatty acid (PUFA) levels in near-bottom waters significantly increased from June to July. However, this change in PUFA was not associated with any observed temporal change in chlorophyll a, δ13C, or C:N ratios. These results show that a multiple biomarker approach is necessary in ecosystem studies of dynamic environments such as near-bottom waters or river-influenced shelves.

IMPACT OF ATMOSPHERIC POLLUTION UPON THE HEALTH OF THE POPULATION: SINGULAR EVENTS

Background and Aims: Recent studies point out that the association between morbidity and mortality with atmospheric pollution varies depending upon the region, seasonal period and the heterogeneous chemical composition of suspended particulate matter. From the environmental point of view, many studies exist about variations in PM levels, both on their size distribution as well as their chemical composition, according to certain singular events having an either natural or anthropogenic origin, identified by the analysis of the surrounding orographic, meteorological and environmental characteristics. The objective of this study is to estimate the short-term association between the number of hospital emergency room admissions and atmospheric pollution, evaluated by a lone variable categorized as event. Methods: Ecological study of temporal series relating hospital emergency room admissions caused by the circulatory apparatus cerebrovascular, total cardiac, total respiratory, asthma and chronic pulmonary obstruction and the atmospheric pollution indicated by the presence or not of a singular event in the city of Elche. The following are considered events: a) Saharan intrusion, contributing mineral dust masses from North Africa; b) Atmospheric stability, high stability situations favoring pollution accumulation; c) Regional accumulation, persistent recirculation of contaminated air masses; d) European episode, the entrance of air masses originating in Europe; e) Smoke or collections of particles resulting from incomplete combustion; and f) Firework displays. The magnitude of association was estimated using Poisson regression. Results: The increase in atmospheric pollution during periods of atmospheric stability is associated with an increase of 1.64% (IC 95%: 1.30-2.08%) in hospital admissions from respiratory causes, and specifically from asthma (2.55%) or COPD (1.26%), but not statistically significant. On the other hand, a risk of becoming ill due to cardiovascular causes was obtained in both periods of Saharan intrusion as well as atmospheric stability, but they were not significant either. Conclusions: Singular events are a variable to keep in mind in the study of the impact of atmospheric pollution upon the health of the population. Although these results can only be considered preliminary, as there were only two events – a Saharan intrusion and atmospheric stability – a sufficient number of days did transpire to be studied.

Seasonal variations in the Sr-Nd isotopic compositions of suspended particulate matter in the lower Changjiang River: Provenance and erosion constraints

Suspended particulate matter samples were collected monthly for more than 2 years in Nanjing, China to examine seasonal changes in the Sr-Nd isotopic compositions of the lower Changjiang River (CR). The results indicate that the 87Sr/86Sr ratios of the samples ranges from 0.725352 to 0.738128, and the values of ɛ Nd(0) ranges from −10.55 to −12.29. The Sr-Nd isotopic compositions show distinct seasonal variations. The samples had lower 87Sr/86Sr ratios and higher ɛ Nd(0) values during the flood season than the dry seasons. The seasonal variations primarily reflect the controls of provenance rocks and erosion in different sub-catchments. The relative decrease in 87Sr/86Sr ratios and the increase in ɛ Nd(0) values during the flood season may reflect an increasing in the mechanical erosion rate in the upper basin and the contribution of more sediment from the upper reaches. The end member values of 87Sr/86Sr and ɛ Nd(0) of the samples were 0.728254 and −11.26, respectively.

Trace metal composition of suspended particulate matter in the water column of the Black Sea

We analyzed the chemical composition of suspended matter from the Black Sea for a complete suite of elements used as tracers for various sources and processes. Samples of suspended matter were collected at four stations from the Bosporus to the center of the western gyre during a R/V Bilim cruise in September 2000. Sample depths were from the oxic surface layer, the suboxic zone and the upper part of the anoxic (sulfidic) layer. All samples were analyzed for Al, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Mo, Ag, Cd, Ba, Pb, U and P using ICP-MS, AAS, and spectrophotometer. The main objective of this study was to determine the processes that influence the distributions of particulate trace metals in the water column under various redox environments. The composition of the particulate matter was influenced by lithogenic input from surrounding rivers, biological production in the surface layer, biogeochemical (e.g. redox) processes and anthropogenic inputs. Almost all elemental concentrations decreased from the coastal to the offshore stations to the center of the western gyre. Metal/Al ratios were compared with the ratios of average crust and Danube and Turkish rivers. Deviations from these lithogenic sources were used to examine the anomalies due to geochemical, biological and anthropogenic processes. In general, the largest metal enrichments relative to crust were observed inthe surface samples away from coastal sources. Metal/P ratios were used to compare data for some of the elements with previous data from the open ocean. The Me/P ratios for Cu, Zn, Mo and Ni were much higher than open ocean studies, while the ratios for Cd and Co were comparable. The high Me/P (and Me/Al) for several elements suggest anthropogenic input may contribute to these high surface concentrations. The composition of particulate matter from the suboxic zone showed that some elements were strongly enriched. Enrichments of Mn and Fe in the suboxic zone were observed, as expected. Mn and Fe oxides play an important role in scavenging processes. The redox dependent processes in the suboxic - anoxic interface influence the vertical distribution of U, V, Ni, Co, Cu, Zn, Ba and possibly Mo, Cr. Elements influenced by sulfide formation in the anoxic layer were Fe, Cr, Ni, Co, Mo, and Ag.

Characterization and source determination of stream suspended particulate material in White Clay Creek, USA

Abstract The material exported from a watershed reflects its origin and the processes it undergoes during downhill and downstream transport. Due to its nature as a complex mixture of material, the composition of suspended particulate material (SPM) integrates the physical, biological and chemical processes effecting watershed material. This study will (1) use a sediment fingerprinting approach to quantify the composition and sources of SPM in the White Clay Creek Watershed in SE Pennsylvania and Delaware, USA, (2) examine longitudinal trends in SPM composition and source in first to fourth reaches of the White Clay Creek, (3) quantify the differences in composition and source with hydrologic variations produced by storms and seasonality.

Composition of the suspended particulate matter at the Severnaya Dvina River mouth (White Sea) during the spring flood period

The grain-size and mineral composition of the suspended particulate matter (SPM) of the Severnaya Dvina River mouth is studied, as well as the content of several lithogenic elements in the SPM during the spring flood in May 2004. The data published on the composition of the riverine SPM in the White Sea basin are very poor. The spring flood period when more than half of the annual runoff is supplied from the river to the sea in a short time is understood more poorly. The report considers the comparison results for the grain-size compositions of the SPM and the bottom sediments. The data of laser and hydraulic techniques of the grain-size analysis are compared. The short-period variations of the SPM concentration and composition representing two diurnal peaks of the tide level are studied. It is found that the SPM is mainly transferred during the spring flood as mineral aggregates up to 40 μm diameter. The sandysilty fraction of the riverine SPM settles in the delta branches and channels, and the bulk of the fine pelitic matter is supplied to the sea. The mineral and chemical composition of the Severnaya Dvina River SPM is determined by the supply of substances from the drainage basin. This substance is subjected to intense mechanic separation during the transfer to the sea. The key regularities of the formation of the mineral composition of the SPM during the flood time are revealed. The effect of the grain-size composition of the SPM on the distribution of the minerals and elements studied in the dynamic system of the river mouth are characterized.

Urban and suburban aerosol in Yokohama, Japan: a comprehensive chemical characterization

This article analyses elemental composition of suspended particulate matter (SPM) samples collected monthly from 1999 to 2005 at two locations in Yokohama, Japan. Microwave digestion and inductively coupled plasma mass spectroscopy was employed to measure Mg, Al, Ca, V, Cr, Mn, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Ag, Cd, Cs, Ba, Pb, and Bi. Water-soluble ions (Na(+), NH(4+), K(+), Ca(2+), Cl(-), NO(3-), and SO(4)2-) and carbonaceous mass (elemental and organic carbon) were detected using ion chromatograph and CHN analyzer, respectively. The results indicate that the composition of SPM on one of the sites is determined by automobile emissions and on the other by industrial combustions. The impact of the emission regulations for automobiles in large Japanese cities, which were enacted during 2002 and 2003, on the SPM composition of the samples is also studied.

Seasonal variations of physical and chemical erosion: A three-year survey of the Rhone River (France)

Numerous studies of weathering fluxes have been carried out on major world rivers during the last decade, to estimate CO 2 consumption rates, landscape evolution and global erosion rates. For obvious logistical reasons, most of these studies were based on large scale investigations carried out on short timescales. By comparison, much less effort has been devoted to long term monitoring, as a means to verify the temporal variability of the average characteristics, their trends, and the representativeness of short-term investigations. Here we report the results of a three-year survey (November 2000 to December 2003) of the major and trace element composition of dissolved and suspended matter in the lower Rhone River (France), the largest river of the Mediterranean area. Subsurface water samples were collected in Arles, about 48 km upstream of the estuary, twice a month routinely, and at higher frequency during flood events. During each flood event, the suspended particulate matter (SPM) show the usual trend of clockwise hysteresis with higher SPM concentrations on the rising limb of the flood than at the same discharge on the falling limb. We show that the annual average SPM flux of the Rhone River to the Mediterranean Sea (7.3 ± 0.6 × 10 6 tons yr −1) was largely controlled by the flood events (83% of the solid discharge occurred in less than 12% of the time), and that the precision on the total output flux depends strongly on the precise monitoring of SPM variations during the floods. The chemical composition of water and SPM are characterized by the predominance of Ca 2+ due to the abundance of carbonate rocks in the Rhone watershed. Chemical budgets have been calculated to derive the contributions of atmospheric deposition, carbonate, silicate and evaporite weathering, and anthropogenic inputs. The chemical weathering rate of carbonates is estimated to be 89 ± 5 t km −2 yr −1 compared to 14.4 ± 3 t km −2 yr −1 from silicates. By contrast, the physical erosion rate of silicates is about 51 t km −2 yr −1 against 19 t km −2 yr −1 for carbonates. The steady-state model of Gaillardet et al. (1995) has been applied to the chemical composition of dissolved and solid products. The results show that the Rhone River currently exports much less material than produced at steady-state by weathering in its watershed. The sediment flux inferred from the steady-state calculation (21–56 × 10 6 t yr −1) is on the same order as that estimated in literature for the 19th and the beginning of the 20th centuries. This imbalance may suggest that the Rhone is under a transient erosion regime following climate change (i.e. significant decrease of the flooding frequency since the beginning of the 19th century). On the other hand, the imbalance may also be due to the trapping of alluvion by the numerous dams on the river and its tributaries. Our data corroborate with previous studies that suggest a strong coupling between chemical and physical erosion fluxes, during the hydrological seasonal cycle of the Rhone River. The correlation between physical and chemical transport rates is, however, clearly different from that reported for global annual averages in large world rivers.

Elemental composition of suspended particulate matter and sediments in the coastal environment of Thermaikos Bay, Greece: Delineating the impact of inland waters and wastewaters

An integrate study on the occurrence of major, minor and trace elements in the coastal environment of Thermaikos Gulf, Northern Aegean Sea, was carried out. The elemental composition of marine sediments and suspended particulate matter from Thermaikos Bay as well as the composition of suspended particles from various inland water (3 rivers and 4 streams) and wastewater (4 types of municipal and industrial origin) end up to the gulf was investigated during the period 2005–2006. The elemental profiles and characteristics of particulate matter from the examined water-types were discussed. The pollution status of marine sediments was evaluated by employing enrichment factors and sediment quality guidelines (TEL/PEL, ERM/ERL). Zn, Cu, Pb, As and Ag were found to have significant contribution from anthropogenic sources. Sites located at the northern part of the bay exhibited higher pollution indices and can be considered of medium-high priority. Principal Component Analysis was employed to find out the factors affecting the composition of the sediments and suspended particulate matter and to elucidate similarities/dissimilarities in the elemental profiles between the different water-types.

Lithium, magnesium and uranium isotope behaviour in the estuarine environment of basaltic islands

This study presents major and trace elements and uranium (U), lithium (Li) and magnesium (Mg) isotope data for dissolved and suspended particulate material from estuaries draining dominantly basaltic terrains in Iceland (Borgarfjörður) and Sao Miguel (Povoação) in the Azores archipelago. The concentrations of dissolved sodium (Na), calcium (Ca), potassium (K), sulphate (SO 4), Mg and Li, and 7Li/ 6Li and 26Mg/ 24Mg isotope ratios vary directly as a function of the dissolved chloride concentration [Cl], indicating that these species are non-reactive in these estuaries. However, U appears to be affected either by colloid flocculation or the formation of Fe-oxyhydroxides in Borgarfjörður. The major element composition of suspended particulate material in the estuary at Borgarfjörður shows that the detrital silicates delivered to the estuarine mixing zone are relatively unweathered. Accordingly, the δ 26Mg isotope composition of the suspended material is indistinguishable from that of the parent basalts. However, the ( 234U/ 238U) activity ratios of the suspended material are significantly different from the parent basalt indicating rapid equilibration of the U isotopes between particles and seawater. The Li concentration and δ 7Li isotope composition of the suspended load are also observed to increase with increasing [Cl], consistent with ongoing weathering of detrital material and the formation of secondary minerals in seawater. Depending on the particle residence time in the estuary, this process could remove as much as 15–25% of the global riverine input of Li to the ocean.

Atmospheric aerosols and sedimentation in arid zones of the Atlantic Ocean

The study of atmospheric aerosols over oceans is one of the new priority fields in the investigation of sedimentation in the oceans. Atmospheric transport of sedimentary particles suspended in the air is a link between the sources of matter transport from land, the ocean surface (substance mobilization zone), and bottom sediments [1‐3 and others]. Aeolian transport is especially important as a source of sedimentary matter in arid zones, where river discharge is minimal, especially in the ocean regions located far from the continents. Deserts, semideserts, and savannas in Africa are the main sources of aerosols in the Atlantic. A large number of publications is dedicated to the study of the main regions of outflow and pathways of transport of the African dust to the ocean observed by means of satellite images, calculation of inverse trajectories, identification of minerals and tracer elements, and so on [1‐5 and others]. However, publications estimating the specific contribution of aerosols to the composition of suspended particulate matter (SPM) in the ocean are quite rare. Most such works are dedicated to comparison of aerosol and matter fluxes collected by sedimentation traps in the water column [5 and others]. However, we did not find any publications devoted to comparison of the atmospheric aerosol and oceanic SPM samples taken simultaneously and processed using the same methods.

Composition of Suspended Particulate Matter and Food Environment of Manila Clam, Ruditapes phillippinarum in Banzu Intertidal Sand Flat

Tidal variability of biochemical composition (carbon and nitrogen stable isotopic ratios) and phytopigment content of suspended particulate matter (SPM) in the bottom water were investigated in Banzu Intertidal Sand Flat, Tokyo Bay, Japan and food environment with diet of manila clam, Ruditapes philhppinarum were discussed. Biochemical composition of SPM showed large tidal variations and it was suggested that high tide periods were suitable food environment for clam. The results also indicated that phytoplankton which transported from offshore around high tide is important food source for clam. In addition, results of stable isotope analyses suggest that clam selectivelyintake SPM during high tide periods and assimilate selected components among those SPM.

Particulate organic carbon budget in the open Algero-Balearic Basin (Western Mediterranean): Assessment from a one-year sediment trap experiment

With the aim of improving the knowledge of the open ocean carbon cycle, we present a budget of particulate organic carbon (POC) fluxes carried out in the deep central part of the Algero-Balearic Basin (ABB) at 2850 m water depth based on a single mooring equipped with five automated sediment traps deployed from April 2001 to May 2002 at depths of 250, 845, 1440, 2145 and 2820 m. Suspended particulate matter (SPM) and superficial sediments were also used as indicators of hydrodynamics and carbon burial, respectively. The data reveal that the fraction of primary production buried in the sediment, which finally leads to the sequestration of carbon dioxide from the atmosphere, is 0.16%, lower than the values found in the nearby continental margin regions such as the Alboran Sea (0.48–0.89%) but of the same order as recorded at other Mediterranean sites at similar depths, such as the Ionian Sea (0.11%). As they sink through the water column, the particles exhibit decreases in flux that are similar to those observed elsewhere, but also show variations that appear to correlate with hydrological features of the water masses present in the basin, as revealed by SPM concentrations and compositions. The input of the tyrrhenian deep water (TDW) into the ABB at 800–1500 m of water depth exhibits low suspended POC concentrations and low sinking POC fluxes were also observed in this depth range. Gulf of Lions water mass formation appears to also contribute to elevated suspended POC concentrations and perhaps POC accumulation in the traps and sediments by spreading of dense cold water along the whole ABB that supplied POC at depths higher than 2000 m.

Elemental compositions of atmospheric particulates collected in Japan from 2002 to 2004

Chemical compositions of suspended particulate matter (SPM) in atmosphere collected at Hachioji and Sakata in Japan from 2002 to 2004 were determined by prompt gamma-ray analysis and instrumental neutron activation analysis. About 40 elemental concentrations in SPM could be determined, and enrichment factors and elemental correlations were examined. Several elements such as Cl, Cr, Ag, Sb, and W were largely different between Hachioji and Sakata, although their sources are not clear at present.

River sediments provide a link between catchment pressures and ecological status in a mixed land use Scottish River system

This study evaluates water quality, suspended and bed sediment, ecological and catchment land use data for 13 catchments of the mixed land use River Dee, NE Scotland, where pollution point sources are limited. Samples were collected at key times of biological activity (early and late summers). Mean river water concentrations were smaller in main stem and upland sites and greater in tributaries where agricultural pressures were greater and were 2–41 μgPO 4-P l −1, 8–58 μg total dissolved P l −1 and 1–6 mg l −1 of suspended particulate matter (SPM). SPM was 7–372 times enriched in biologically available P (BAP; determined using an FeO paper strip method) and 2–122 times in organic C relative to bed sediments. Ratios in river water concentrations of BAP attributed to the SPM (0.1–1.0 μgP l −1) to PO 4-P had the greatest range at baseflow (0.01–0.80) with larger values for low land use intensity catchments. During May chlorophyll a concentrations were related to SPM BAP ( p<0.001), but later in summer to PO 4-P, and there was a corresponding change in the organic composition of SPM observed by IR spectroscopy. SPM concentrations and SPM BAP were better related to intensive grassland land use ( p<0.001) than was PO 4-P concentration ( p<0.01) and also predicted abundances of filter feeding macroinvertebrates ( p<0.001). Within this river system SPM quantity and composition proved to be an indicator of river biogeochemical functioning and requires further investigation as a potentially sensitive monitoring tool and to increase our understanding of chemical ecological links.

Distributions of dissolved and particulate elements in the Yangtze estuary in 1997–2002: Background data before the closure of the Three Gorges Dam

Concentrations of 31 particulate elements (Al, As, Ba, Ca, Cd, Ce, Co, Cr, Cs, Cu, Eu, Fe, Hf, La, Lu, Mg, Mn, Ni, P, Pb, Rb, Sb, Sc, Sm, Sr, Th, Ti, V, Y, Yb, and Zn) and 6 dissolved elements (Al, Cd, Cu, Fe, Mn, and Ni) in the Yangtze estuary were determined during the period from 1997 to 2002. The salinity increased monotonously, and suspended particulate matter (SPM) peaked initially and then decreased rapidly in the mixing zone, which lies between 121.5° E and 122.5° E. The elemental composition of SPM was almost constant throughout the estuary, except for an increase of P, Cd, Pb, Sr, Cu, Mg, Cr, Zn, Ni, Ca, and Ba at some stations on the continental shelf. On the other hand, dissolved metal concentrations changed as the salinity increased in the mixing zone: dissolved Cu was diluted conservatively, dissolved Cd and Ni were released from SPM, and dissolved (colloidal) Fe, Al, and Mn increased when SPM increased. By mixing experiments using unfiltered river water and seawater, the conservative mixing of dissolved Cu and the release of dissolved Cd and Ni from SPM were reproduced in the laboratory. Effective dissolved metal concentrations (including the metals released in the mixing zone) in the river were Al (330 nM), Cd (0.39 nM), Cu (23 nM), Fe (72 nM), Mn (8 nM), and Ni (7 nM), values significantly lower than the concentrations of particulate metals, that is, Al (880 μM), Cd (1.7 nM), Cu (300 nM), Fe (230 μM), Mn (5.5 μM), and Ni (240 nM). Riverine metals were transported to the sea mainly in particulate form. The metal input through the Yangtze River has not changed significantly since the 1980s, when previous investigations in the same area (U.S.–China joint cruises in 1980 and 1981, and France–China joint cruises in 1986) were conducted.

Hydrography, oxygen saturation, suspended particulate matter, and chlorophyll- a fluorescence in an oceanic region under freshwater influence

During the northern hemisphere summer of 1999, we analyzed the hydrography, oxygen saturation, suspended particulate matter, and chlorophyll- a fluorescence of the Southern Gulf of Mexico, an oceanic region under the influence of freshwater from the Grijalva–Usumacinta Rivers system. This rivers system induces thermal and haline fronts within the Southern Gulf, with surface temperature and salinity increasing offshore. A westward shelf circulation is inferred from the tilting of isopycnes and cold water on the bottom of the shelf break. Oxygen saturation shows low values in the region under freshwater influence. The composition of suspended particulate matter shows high variability, with the inorganic fraction dominant over the organic fraction. At the edge of the continental slope, the organic fraction is very high within the euphotic layer. The vertical distribution of chlorophyll- a fluorescence indicates different trophic conditions within the water column at three studied regions: the eastern shallow region, the middle shelf, and the continental slope. We found mesotrophic or eutrophic waters at the chlorophyll- a maximum level and oligotrophic waters at the background level. The behavior of the analyzed variables enables us to identify three ecological regions: (1) the inner shelf, where chlorophyll- a fluorescence increases near the seafloor, related to the thermocline; in this region the euphotic layer comprises the entire water column; (2) the middle shelf, with a sharp maximum of chlorophyll- a at mid-depths, strongly associated with the thermocline; and (3) the outer region above the continental slope that shows a deep-level chlorophyll- a maximum associated with low-light conditions. We propose that the vertical structure of chlorophyll- a fluorescence in the study area is dependant on thermal and light structures, and in some cases on the thermal and haline fronts associated with the river plumes, as well as on the regional circulation pattern.

The role of suspended particulate matter in 234Th scavenging and 234Th-derived export fluxes of POC in the Canada Basin of the Arctic Ocean

The concentration and composition of suspended particulate matter (SPM) plays a major role in the removal of particle-reactive nuclides in the ocean. In the Arctic Ocean, SPM concentrations in the deep basins vary widely, over an order of magnitude. Unique features, such as the presence and release of algae from sea ice to the upper waters may result in differing scavenging behavior of suspended particulate matter. In this study, we collected a suite of water samples across a horizontal transect in the western Arctic Ocean, from the coast to the deep Canada Basin, and measured concentrations of SPM, particulate organic carbon (POC) and nitrogen, and activities of dissolved and particulate 234Th. Our data indicate that the concentrations and inventories of SPM is about an order of magnitude higher than those reported for the permanently ice-covered Arctic region, but comparable to the value reported recently for another deep station in the Canada Basin. There is disequilibrium between 238U and total 234Th in the upper waters (∼100 m) indicating active scavenging in the deep basins. Variations in the specific activity of 234Th in the upper ∼100 m indicate differences in the remineralization rates in the deep Canada Basin. Plots between particulate and dissolved removal rate constants and SPM indicate that the biochemical composition of particulate matter could play a significant role on the removal rates of Th. The POC export rate calculated for the upper 50 m of the deep Canada Basin was found to be 1.4 mmol m −2 day −1. The residence times and removal fluxes of particulate and dissolved 234Th calculated for the upper 50 m in our study is compared to the calculated values from published data for other regions in the Arctic Ocean.

Application of EDXRF and Thin Window EPMA for the Investigation of the Influence of Hot Air Heating on the Generation and Deposition of Particulate Matter

This paper presents a systematic micro-analytical study for the assessment of the influence of a typical hot-air “blow-in” heating system on the generation, transport and deposition of suspended particulate matter (SPM) in the church of Rocca Pietore (Italian Alps). This kind of heating system is very popular in cold regions due to its fast response and economic properties. The size, chemical composition and abundance of individual particles responsible for the negative impact on the displayed artworks are determined by ultra-thin window EPMA. EDXRF is used to determine the bulk chemical composition of SPM. Some gaseous pollutants (SO2, NO2 and O3) are sampled with the application of passive diffusion tubes and quantified with ion-chromatography and spectrophotometry. It is pointed out that several deterioration processes, such as the abrasion of the plastered walls, the re-suspension of the particulate pollution and the generation of NO2 gas, arise mainly from using the heating system. Each of these observations is a concern for the preservation of the displayed works of art.