Particulate Trace Metal Concentrations Research Articles

Significant Impact of Hydrothermalism on the Biogeochemical Signature of Sinking and Sedimented Particles in the Lau Basin

AbstractIron (Fe) is an essential micronutrient for diazotrophs, which are abundant in the Western Tropical South Pacific Ocean (WTSP). Their success depends on the numerous trace metals, particularly Fe, released from shallow hydrothermal vents along the Tonga Arc. This study aimed to explore the spatio‐temporal impact of hydrothermal fluids on particulate trace metal concentrations and biological activity. To identify the composition of sinking particles across a wide area of the WTSP, we deployed sediment traps at various depths, both close and further west of the Tonga Arc. Seafloor sediments were cored at these deployment sites, including at a remote location in the South Pacific Gyre. The sinking particles were composed of a large amount of biological material (up to 88 mg d−1), indicative of the high productivity of the region. A significant portion of this material (∼21 ± 12 wt.%) was lithogenic of hydrothermal origin, as revealed through Al‐Fe‐Mn tracing. The sinking material showed similar patterns between lithogenic and biogenic fractions, indicating that hydrothermal input within the photic layer triggered surface production. A hydrothermal fingerprint was suggested in the sediments due to the high sedimentation rates (>47 cm kyr−1) and the presence of large, heterogeneous, metal‐rich particles. The presence of nearby active deep hydrothermal sources was suspected near the Lau Ridge due to the large particle size (1–976 μm) and the significant excess of Fe and Mn (2–20 wt.%). Overall, this study revealed that hydrothermal sources have a significant influence on the biogeochemical signature of particles in the region.

Glacial meltwater and sediment resuspension can be important sources of dissolved and total dissolvable aluminum and manganese to coastal ocean surface waters

AbstractThe supply of aluminum (Al) and manganese (Mn) to the Gulf of Alaska from coastal sources is poorly constrained. Here, we investigate the seasonality of sources to better constrain Al and Mn cycling in the coastal Gulf of Alaska region and add to our understanding of seasonal and interannual inputs. We examine Mn and Al behavior over the shelf to distinguish between redox‐induced release of dissolved trace metals (i.e., diffusion from sediments), sediment resuspension, and meltwater release. Data suggest that, prior to the onset of stratification in the spring, shelf sediment resuspension from deep mixing is an important mechanism for trace metal delivery to surface waters. As spring and summer ensue, increased meltwater discharge coupled with increased surface water temperatures result in stratification of the water column within the coastal Gulf of Alaska, and meltwater becomes a more important source of Al and Mn to the surface waters. The limited data available suggest that a redox‐driven flux of Mn from shelf sediments is not as important as the meltwater flux during the summer. In addition, dissolved trace metal concentrations in meltwater‐influenced plumes over the shelf exhibit conservative mixing, while particulate trace metal concentrations do not behave conservatively. This indicates that there are different physical controls (particle settling vs. mixing) on the spatial distributions of dissolved and particulate Al and Mn in coastal waters, the manifestation of which are likely highly variable and dependent on the trace metal composition of the river and the hydrodynamics governing this interaction at any given time.

A novel device for trace metal‐clean sampling of bottom water and suspended particles at the ocean's lower boundary: The Benthic Trace Profiler

AbstractThe benthic boundary layer plays a crucial role in the exchange of trace metals between surface sediments and the water column. So far it has been difficult to study dissolved–particulate interactions of trace metals in this highly reactive interface layer due to the lack of suitable sampling methods. We developed a new device, called Benthic Trace Profiler (BTP), which enables simultaneous sampling of near‐bottom water and suspended particles in high depth resolution within the first 3 m above the seafloor. The device was tested successfully in the Baltic Sea. The concentrations of several trace metals (Co, Ni, Cu, Zn, and Cd) in the collected bottom waters overlapped with concentrations in water column samples above collected with conventional methods. This observation indicates that the sampling device and method is trace metal clean. The trace metals Fe and Mn showed concentration gradients within the benthic boundary layer indicating an upward diffusive flux. This observation is consistent with a diffusive benthic flux of these trace metals across the sediment–water interface, which was independently verified using pore‐water profiles. Suspended particles can be used to study precipitation processes and to determine the carrier phases of trace metals. The BTP fulfilled all the intended requirements as it allowed a simultaneous, uncontaminating and oxygen‐free sampling of seawater and suspended particles to gather high‐resolution profiles of dissolved and particulate trace metal concentrations above the seafloor. The device closes the gap between water column and sediment sampling and helps researchers to better understand trace metal exchange processes across the ocean's lower boundary.

Tracing iron along the flowpath of East Australian Current using iron stable isotopes

The mechanisms delivering iron (Fe) to Southern Ocean surface waters and resulting capacity for the oceanic drawdown of CO2 are important to constrain in a changing climate. The East Australian Current (EAC) is a major western boundary current flowing south along the eastern margin of Australia, hypothesized to play an important role in entraining Fe from a variety of potential sources and supplying Fe to large annual spring phytoplankton blooms in HNLC waters. We report Fe concentration and Fe isotope (δ56Fe) profiles for both dissolved and particulate phases at stations within the EAC, in the frontal mixing zone, and in subantarctic waters along the southward flowpath of the EAC in early spring. Mixed layer dFe concentrations declined from EAC source waters (0.32–0.53 nmol kg−1) into subantarctic waters (0.27–0.42 nmol kg−1) with a concurrent deepening of the ferricline. Particulate trace metal concentrations indicate robust inputs of lithogenic particles to subtropical EAC waters, potentially impacted by advection of shelf sedimentary particles and evidence of a significant supply from local aerosol deposition. The isotopic composition of pFe in the EAC (0.3 ± 0.1‰) is similar to prior reports of aerosol δ56Fe and upper ocean δ56pFe in the western Pacific and isotopically heavier than average values for the bulk continental crust. In EAC surface waters, isotopically light δ56dFe values (0.11–0.16‰) are observed likely due to reductive release of dFe from lithogenic particles in the photic zone with a particle-dissolved phase fractionation (Δ56FedFe–pFe) of −0.1 to −0.4‰. At depth, elevated dFe concentrations and a heavy δ56dFe signature suggest a non-reductive release of dFe from lithogenic particles via desorption or dissolution processes with a Δ56FedFe–pFe of +0.3‰. During southward transit of EAC waters, mixed layer dFe pools become increasingly heavy due to biological uptake through the frontal mixing zone and into subantarctic waters. We also observe differences in particulate trace metal concentrations in intermediate waters between subantarctic stations that could result from entrainment of sedimentary particles during transit over the relatively shallow South Tasman Rise.

HVAC filtration of particles and trace metals: Airborne measurements and the evaluation of quantitative filter forensics.

Filters installed in the heating, ventilation, and air-conditioning (HVAC) systems can serve as air-cleaning and sampling devices for indoor particles. The purpose of this article is to evaluate these dual roles. An occupied home with a central HVAC system equipped with a Minimum Efficiency Reporting Value (MERV, from ASHRAE Standard 52.2) 11 filter was monitored for six weeks. Weekly airborne gravimetric and real-time sampling was performed to measure the particle size distribution and the concentration of total suspended particles (TSP), PM10, PM2.5, PM1, and 12 trace metals. The weekly system runtimes were intentionally changed to provide a wide range of weekly filtration volumes. The quantitative filter forensics (QFF) concentrations of particulate matter (PM) and trace metals were calculated using the analysis of the dust collected on the HVAC filter, the filtration volume, and filter in-situ efficiency. The results indicated that filtration was not influential to remove PM and trace metals as the concentrations during the weeks with continuous HVAC operation were not consistently lower than those during the other weeks. This suggests the dominance of other particle and trace metal source and loss mechanisms weakens the influence of filtration in this home. The QFF evaluation results indicated that the concentration of TSP and over half of the tested trace metals (e.g., Pb, Cd, Ni, V, Sb, K, and Sr) could be estimated by QFF within a factor of two when compared to airborne sampling results. PM10, PM2.5, and PM1 concentrations were significantly underestimated by QFF potentially due to the limitations of size distribution analysis by a laser diffraction particle sizer (LDPS) for the detection of <1μm particles. Overall, while QFF was promising for TSP and some trace metals, improvement in size distribution analysis could extend the application of QFF for airborne sampling.

Investigation on trace metal speciation and distribution in the Scheldt estuary

The biogeochemical behavior of Cd, Co, Cr, Cu, Ni and Pb along the historically polluted Scheldt estuary (Belgium - The Netherlands) was investigated in this study. As never studied before in this area, labile trace metals were measured using the passive sampling technique of Diffusive Gradients in Thin-films (DGT), while total dissolved and particulate trace metal concentrations were assessed using classic active sampling techniques. This dual approach allowed us to highlight the variations of trace metal speciation and distribution in the estuarine surface waters, considering environmental and physicochemical gradients along the transect. The large data set obtained was then compared with literature data of historical measurements along the Scheldt (from 1980 until now), but also from other estuaries. As emphasized by our results, trace metal mobility and partitioning along the Scheldt estuary was mainly driven by biogeochemical reactions which were strongly influenced by gradients of specific estuarine physico-chemical parameters, such as salinity, turbidity, temperature and so on. Hence, all species of trace metals displayed a non-conservative behavior. More precisely, dissolved labile fractions of trace metals showed higher levels in the middle estuary, where many solubilization and remobilization processes occurred due to turbulent mixing mechanisms and an increasing salinity. Our study confirmed the decreasing trend historically observed for particulate metals along the Scheldt, as well as the rising concentrations recorded for dissolved trace metals which might also lead to an increase of their labile fraction measured by the DGT. Finally, these preliminary results suggested that a more regular monitoring of labile metal along the Scheldt estuary is essential to have an in-depth understanding of trace metal speciation and to review bioavailability of trace metals within estuarine ecosystems.

Particulate trace metal dynamics in response to increased CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; and iron availability in a coastal mesocosm experiment

Abstract. Rising concentrations of atmospheric carbon dioxide are causing ocean acidification and will influence marine processes and trace metal biogeochemistry. In June 2012, in the Raunefjord (Bergen, Norway), we performed a mesocosm experiment, comprised of a fully factorial design of ambient and elevated pCO2 and/or an addition of the siderophore desferrioxamine B (DFB). In addition, the macronutrient concentrations were manipulated to enhance a bloom of the coccolithophore Emiliania huxleyi. We report the changes in particulate trace metal concentrations during this experiment. Our results show that particulate Ti and Fe were dominated by lithogenic material, while particulate Cu, Co, Mn, Zn, Mo and Cd had a strong biogenic component. Furthermore, significant correlations were found between particulate concentrations of Cu, Co, Zn, Cd, Mn, Mo and P in seawater and phytoplankton biomass (µgC L−1), supporting a significant influence of the bloom in the distribution of these particulate elements. The concentrations of these biogenic metals in the E. huxleyi bloom were ranked as follows: Zn &lt; Cu ≈ Mn &lt; Mo &lt; Co &lt; Cd. Changes in CO2 affected total particulate concentrations and biogenic metal ratios (Me : P) for some metals, while the addition of DFB only significantly affected the concentrations of some particulate metals (mol L−1). Variations in CO2 had the most clear and significant effect on particulate Fe concentrations, decreasing its concentration under high CO2. Indeed, high CO2 and/or DFB promoted the dissolution of particulate Fe, and the presence of this siderophore helped in maintaining high dissolved Fe. This shift between particulate and dissolved Fe concentrations in the presence of DFB, promoted a massive bloom of E. huxleyi in the treatments with ambient CO2. Furthermore, high CO2 decreased the Me : P ratios of Co, Zn and Mn while increasing the Cu : P ratios. These findings support theoretical predictions that the molar ratios of metal to phosphorous (Me : P ratios) of metals whose seawater dissolved speciation is dominated by free ions (e.g., Co, Zn and Mn) will likely decrease or stay constant under ocean acidification. In contrast, high CO2 is predicted to shift the speciation of dissolved metals associated with carbonates such as Cu, increasing their bioavailability and resulting in higher Me : P ratios.

Trace metal geochemistry of remote rivers in the Canadian Arctic Archipelago

Trace metals are essential micronutrients for phytoplankton, as well as useful tracers of biogeochemical processes in aquatic systems. The largest Arctic rivers are known to play an important role in the cycling of trace metals in the Arctic Ocean; however, these systems account for little more than half of Arctic freshwater discharge, leaving a major gap in our understanding of the trace metal geochemistry from smaller river systems. This is especially problematic for rivers draining the Arctic coastal margins, as these continuous permafrost systems are anticipated to be particularly sensitive to climate change. This study presents the first observations of dissolved and particulate trace metal concentrations and lead isotopes in 14 rivers in the Canadian Arctic Archipelago (CAA). Dissolved concentrations of aluminum, iron, manganese, nickel, copper, zinc, cadmium, and lead display clear spatial variability in their distributions. Small rivers located in the central islands of the CAA have remarkably low concentrations of these trace metals, while the rivers draining the southern continental landmass have higher values. This geographic variability in dissolved metal concentrations reflects both differences in bedrock geology and the South-North environmental gradients in the Archipelago. We extrapolate these findings to estimate the dissolved trace metal concentrations for other rivers draining the CAA based on their geographic location. Elemental ratios measured in the suspended particulate matter in several rivers indicates a significant enrichment of nickel, copper, zinc, and lead over the crustal composition. In particular, lead isotope composition shows an extremely large range, varying from the highly radiogenic Tree River (206Pb/207Pb: 1.5121) in the south, to the relatively unradiogenic Glacier River (206Pb/207Pb: 1.0153) in the central CAA. Lack of correlation between the Pb isotopic composition and Pb enrichment, suggests Pb is derived from within the watershed. This work presents the first observations of dissolved and particulate trace metal concentrations in small coastal draining rivers from the CAA, an important first step in developing a baseline against which to evaluate future change in the high Arctic.

Trace metal speciation in North Sea coastal waters.

Most trace metals exhibit a dual role in marine waters, acting as nutrients at low concentration and being toxic at high concentration. But besides concentration range, speciation is also an important factor. They both show both seasonal and spatial variations. A thorough comparison between total dissolved and particulate concentrations estimated from manual sampling and an assessment of the bioavailability using Diffusive Gradients in Thin Films (DGT) has been performed in this work for Cd, Co, Cu, Ni and Pb, at several sampling points of the Belgian Coastal Zone (BCZ). Additional information to trace back the origin and identify the anthropogenic fingerprint of Suspended Particulate Matter (SPM) was measured using stable carbon isotope measurements in particulate organic matter. Our results show that: (i) particulate and total dissolved metal concentrations are higher at two stations, one in the harbor of Oostende and one offshore; (ii) dissolved and particulate trace metal concentrations do not correlate with the dissolved labile fractions; and (iii) SPM in the harbor zone is likely from allochthonous sources, while in the offshore station marine origin has been evidenced. Our results indicate that, even though contamination is higher in the harbor zones, the trace metal toxicity, which is linked to the metal bioavailability, is most likely not higher than in the open sea. However, with increasing acidification of the ocean, a shift from particulate to dissolved phase might lead to increasing adverse effects on the coastal environment.

Accumulation processes of trace metals into Arctic sea ice: distribution of Fe, Mn and Cd associated with ice structure

Biogeochemical cycling of trace metals in sea ice is important to the productivity of the Arctic Ocean. Unfortunately, the processes by which trace metals accumulate into sea ice are poorly understood. To gain a clearer understanding of the mechanisms behind trace metal accumulation, dissolved (D, <0.2 μm), and labile particulate (LP = Total Dissolvable – Dissolved) iron (Fe), manganese (Mn), and cadmium (Cd) concentrations were compared to the structure observed in sea ice. Samples were pre-concentrated via solid-phase extraction on NOBIAS Chelate PA-1 resin and analyzed on a Graphite Furnace Atomic Absorption Spectrometer. Using photographic analysis for the percentage of pore microstructure and δ18O analysis, sea ice structure was determined to be snow ice, granular ice (frazil ice), mixed ice (granular and columnar ice) and columnar ice. Salinity and nutrients were low, indicating brine drainage and multi-year ice. High trace metal concentrations in snow ice indicated meteoric snow was a source of trace metals to sea ice. High concentrations of LPFe in granular ice indicated entrainment of suspended particulate trace metals by frazil ice during the formation of the granular ice structure. Whereas the high concentrations of DFe and DMn in granular ice may have been due to reduction from LPFe and LPMn after particle entrainment, indicating chemical transformation processes. Low dissolved and labile particulate trace metal concentrations in mixed and columnar ice indicated a release due to brine drainage. Our study clearly indicates that the differences observed in trace metals among sea ice structures, showed that sea ice formation, chemical reduction and brine release were the processes driving trace metal accumulation and release in the Arctic sea ice.

Particulate Trace Metal Composition and Sources in the Kuroshio Adjacent to the East China Sea: The Importance of Aerosol Deposition

AbstractThe Kuroshio, flowing through the eastern end of the East China Sea, transports terrestrial material to the Northwestern Pacific Ocean. Along the Kuroshio path, we collected size‐fractionated suspended particles in the upper 200 m to investigate the composition and sources of particulate trace metals. Demonstrated by Al‐ and P‐normalized elemental ratios, we found that anthropogenic aerosol deposition was the major source of most particulate trace metals in the Kuroshio region although the impact of bottom resuspension and riverine input may be significant at some specific regions. As seen in our previous studies in the South China Sea and the Western Philippine Sea, this study concluded that anthropogenic aerosol deposition is the dominant particulate trace metal source in the surface water of the Northwestern Pacific Ocean and its marginal seas. Compared to particulate trace metal composition obtained in other open oceans, we found that the distribution patterns of particulate trace metal composition in the surface waters are closely associated with aerosol deposition fluxes. In regions with low deposition, the particulate trace metal concentrations were extremely low and metal to P ratios were all comparable to their intracellular quota previously proposed. In regions with high deposition, metal to P ratios were highly elevated in comparison to their intracellular quota and metal to Al ratios were deviated from lithogenic ratios to various extents. The globally consistent distribution patterns validate trace metal stoichiometry concept in plankton intracellularly and the primary role of aerosol deposition on deciding particulate trace metal composition in oceanic surface water globally.

Spatial and Temporal Distribution of Trace Metals (Cd, Cu, Ni, Pb, and Zn) in Coastal Waters off the West Coast of Taiwan

Surface water samples were collected along the west coast of Taiwan during two expedition cruises which represent periods of different regional climatic patterns. Information on hydrochemical parameters such as salinity, nutrients, suspended particulate matter (SPM), and Chlorophyll a concentrations were obtained, and dissolved and particulate trace metal (Cd, Cu, Ni, Pb, and Zn) concentrations were determined. Spatial variations were observed and the differences were attributed to (1) influence of varying extents of terrestrial inputs from the mountainous rivers of Taiwan to the coast, and (2) urbanization and industrialization in different parts of the island. Geochemical processes such as desorption (Cd) and adsorption to sinking particles (Pb) also contributed to the variability of trace metal distributions in coastal waters. Results showed temporal variations in chemical characteristics in coastal waters as a consequence of prevailing monsoons. During the wet season when river discharges were higher, the transport of particulate metals was elevated due to increased sediment loads. During the dry season, lower river discharges resulted in a lesser extent of estuarine dilution effect for chemicals of anthropogenic sources, indicated by higher dissolved concentrations present in coastal waters associated with slightly higher salinity.

Relationships Between Geochemical Parameters (pH, DOC, SPM, EDTA Concentrations) and Trace Metal (Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn) Concentrations in River Waters of Texas (USA)

Water samples from eight major Texas rivers were collected at different times during 1997–1998 to determine the dissolved and particulate trace metal concentrations, expected to show differences in climate patterns, river discharge and other hydrochemical conditions, and human activities along the different rivers. Specifically, two eastern Texas rivers (Sabine, Neches) lie in a region with high vegetation, flat topography, and high rainfall rates, while four Central Texas rivers (Trinity, Brazos, Colorado, and San Antonio) flow through large population centers. Relatively high dissolved organic carbon (DOC) concentrations in the eastern Texas rivers and lower pH led to higher Fe and Mn concentrations in river waters. The rivers that flow through large population centers showed elevated trace metal (e.g., Cd, Pb, Zn) concentrations partly due to anthropogenically produced organic ligands such as ethylenediaminetetraacetic acid (EDTA) present in these rivers. Trace metal levels were reduced below dams/reservoirs along several Texas rivers. Statistical analysis revealed four major factors (suspended particulate matter [SPM], EDTA, pH, and DOC) that can explain most of the observed variability of trace metal concentrations in these rivers. SPM concentrations directly controlled particulate metal contents. Variation in pH correlated with changes of dissolved Co, Fe, Mn, and Ni, and particulate Mn concentrations, while DOC concentrations were significantly related to dissolved Fe concentrations. Most importantly, it was found that, more than pH, EDTA concentrations exerted a major control on dissolved concentrations of Cd and Zn, and, to a lesser extent, Cu, Ni, and Pb.

The relevance of defining trace metal baselines in coastal waters at a regional scale: The case of the Portuguese coast (SW Europe)

The Water Framework Directives aims a reduction in concentration of hazardous substances in the marine environment. Consequently, there is a need to distinguish between anthropogenically influenced metal concentrations from natural background levels. To better achieve this goal in the Portuguese coast, dissolved and particulate trace metal (TM) concentrations along the Portuguese coast were determined in 46 sites distance 1–3 km from the shoreline. Dissolved values ranged within the following intervals: 0.01–0.89 nM for Cd, 0.01–3.37 nM for Co, 0.90–45.4 nM for Cu, 3.30–140 pM for Hg, 1.88–15.1 nM for Ni, 0.01–0.15 nM for Pb and 1.40–62.0 nM for Zn. Whereas Cd, Co, Cu, Ni and Zn were enhanced in the southern coast, while Pb values were higher in the central part of the western coast. Mercury concentrations showed punctual increases all along the coast. Values of trace metals in suspended particulate matter varied in a broad range: 36–2902 μmol g−1 for Al, 0.10–15.1 nmol g−1 for Cd, 1.50–165 nmol g−1 for Co, 50.0–990 nmol g−1 for Cu, 2.80–76.4 nmol g−1 for Hg, 22–1471 nmol g−1 for Ni, 10.0–347 nmol g−1 for Pb and 416–10,981 nmol g−1 for Zn. Higher values for Al, Ni and Co were found in the central part of the western coast. However, Cd, Cu, Pb and Zn increased their levels from the north coast towards the central and south areas. The variability of both dissolved and particulate metals appears to be mainly associated with oceanographic conditions and continental inputs at North and central areas of the coast, and in the south coast to geological features rather than to anthropogenic pressures. On the basis of these results, regional baseline concentrations are proposed for the three typologies in Portuguese coastal waters defined under the Water Framework Directive.

Evolution of trace metal and organic pollutant concentrations in the Scheldt River Basin and the Belgian Coastal Zone over the last three decades

For the present study, a comprehensive dataset on trace metals (Cd, Cu, Hg, Pb and Zn), PAHs (polycyclic aromatic hydrocarbons), PCBs (polycyclic chlorinated biphenyls) and PCDD/Fs (polycyclic chlorinated dibenzodioxins/furans) in the Scheldt River Basin and the Belgian Coastal Zone was gathered. The resulting time trends for emissions and concentrations measured in the aquatic system itself are presented, discussed and compared to comparable long-term studies.For most of those pollutants atmospheric and aquatic emission data are available from 1985 onward. Earliest studies about pollutants in the Scheldt Estuary go back to 1978 and the general trend observed for their concentrations in the estuary agrees fairly well with the evolution of their emissions. Until the end of the nineties trace metal concentrations decreased at the fluvial and marine end-members of the estuary. However, recent surveys indicate that the dissolved trace metal concentrations particularly in the estuary increased again, while their emissions did not. No historical data about PCDD/Fs' concentrations in the Scheldt River Basin and the Belgian Coastal Zone are available. However, the time trend of the PCDD/F concentrations in human milk corroborates their atmospheric emission reductions.The particulate trace metal concentrations in the Belgian Coastal Zone and in the mouth of the Scheldt Estuary follow the same trend. Nevertheless, Scheldt estuarine inputs to the Greater North Sea decrease slower than those of other estuaries.In sediments of the Upper Scheldt River, a clear decrease for Cd, Pb and Zn, but not for Cu was observed between 1980 and 2007. Also PAH concentrations in those sediments are not decreasing during the last 10years.A time lag exists between the moment that a reduction in the emission of a given pollutant is realized and the decrease of its concentration in the receiving aquatic environment.

Behaviors of dissolved and particulate Co, Ni, Cu, Zn, Cd and Pb during a mesoscale Fe-enrichment experiment (SEEDS II) in the western North Pacific

During mesoscale Fe enrichment (SEEDS II) in the western North Pacific ocean, we investigated dissolved and particulate Co, Ni, Cu, Zn, Cd and Pb in seawater from both field observation and shipboard bottle incubation of a natural phytoplankton assemblage with Fea ddition. Before the Fe enrichment, strong correlations between dissolved trace metals (Ni, Zn and Cd) and PO43-, and between particulate trace metals (Ni, Zn and Cd) and chlorophyll-a were obtained, suggesting that biogeochemical cycles mainly control the distributions of Ni, Zn and Cd in the study area. Average concentrations of dissolved Co, Ni, Cu, Zn, Cd and Pb in the surface mixed layer (0–20m) were 70 pM, 4.9, 2.1, 1.6, 0.48 nM and 52 pM, respectively, and those for the particulate species were 1.7 pM, 0.052, 0.094, 0.46, 0.037 nM and 5.2 pM, respectively. After Fe enrichment, chlorophyll-a increased 3 fold (up to 3 mg/L) during developing phases of the bloom (12 days). Mesozooplankton biomass also increased. Particulate Co, Ni, Cu and Cd inside the patch increase in the concentrations, but there were no analytically significant differences between concentrations inside and outside the patch. The bottle incubation with Fe addition (1 nM) showed an increase in chlorophyll-a (8.9 mg/L) and raised the particulate fraction up to 3–45% for all the metals, accompanying changes in Si/P, Zn/P and Cd/P. These results suggest that Fe addition lead to changes in biogeochemical cycling of trace metals. The comparison between the mesoscale Fe enrichment and the bottle incubation experiment suggests that although Fe was a limiting factor for the growth of phytoplankton, the enhanced biomass of mesozooplankton also limited the growth of phytoplankton and the transformation of trace metal speciation during the mesoscale Fe enrichment. Sediment trap data and the elemental ratios taken up by phytoplankton suggest that export loss was another reason that no detectable change in the concentrations of particulate trace metals was observed during the mesoscale Fe enrichment.

Evaluation of levels, sources and distribution of toxic elements in PM10 in a suburban industrial region, Rio de Janeiro, Brazil

The Oswaldo Cruz Foundation Campus (FIOCRUZ), in a suburban region of the city of Rio de Janeiro, was selected as a case study to assess the pollution released from vehicle and industrial facilities in Basin III, the most polluted area of the city. Concentrations of particulate matter (PM10) and trace metals in airborne particles were determined in an intensive field campaign. The samplings were performed every six days for 24 h periods, using a PM10 high volume sampler, from September 2004 to August 2005. PM10 mass concentrations were determined gravimetrically and the metals by ICP-OES. For PM10, the arithmetic mean for the period is 169 +/- 42 microg m(-3) which is 3.4 times the national recommended standard of 50 microg m(-3). Additionally, 51% of the samplings exceeded the recommended 24 h limit of 150 microg m(-3). Ca, Mg, Fe, Zn and Al were the metals that presented the higher concentrations. The correlation matrix gave two main clusters and three significant principal components (PC). Both PC1 and PC2 are associated to crustal, vehicular and industrial emissions while PC3 is mainly associated to geological material. Enrichment factors for Zn, Cu, Cd and Pb indicate that for these elements, anthropic sources prevail over natural inputs. PM10 levels showed a good correlation with hospital admissions for respiratory diseases in children and elderly people.

Evaluation of levels, sources and distribution of airborne trace metals in seven districts of the Baixada Fluminense, Rio de Janeiro, Brazil

Abstract The main goal of this work is to assess the concentrations of total suspended particles (TSP) and airborne particulate trace metals in seven districts of the Baixada Fluminense, a region of the Metropolitan area of Rio de Janeiro, where the pollution sources are local industries, vehicular emissions and natural inputs. The sampling was performed using a high volume pump. The TSP levels were determined by gravimetry and the metals by inductively coupled plasma optical emission spectroscopy (ICP-OES). Geometrical means between 55.4±15.9 and 241.5±40.0 μg m −3 were determined for TSP, which are higher than both the Brazilian primary and secondary standards of air quality. Enrichment factors show that Zn, Cu, Cd and Pb are due to anthropic emissions. Zn, Cu and Cd levels are high in comparison with other urban and industrial areas. Mean concentrations are 1.1–88 times, 2.9–60.9 times and 3.0–130.0 times higher than reported values for other industrial areas, for Zn, Cu and Cd, respectively. It was not possible to identify a geometrical or seasonal distribution within the Baixada Fluminense area performing cluster and principal component analyses.

Distribution of size-fractionated particulate trace metals collected by bottles and in-situ pumps in the Gulf of Maine–Scotian Shelf and Labrador Sea

The distribution of size-fractionated particulate trace metals (Al, Fe, Mn, Pb, Cu, V, and Co) was investigated in the Gulf of Maine–Scotian Shelf and Labrador Sea by collection of particulate matter using water bottles (Go-flo) and large volume in-situ pumps (Challenger Oceanic Systems and Services). Trace metal procedural filter blanks for Poretics membrane filters (0.4- and 10 μm pore size) and Nitex screens (53 μm mesh size) were sufficiently low that metal concentrations could be measured reliably. These results validate the use of Challenger Oceanics Systems and Services in-situ pumps for collection of particulate trace metals (Al, Fe, Mn, Pb, Cu, V, and Co) in shelf, slope, and open ocean Atlantic waters. In the Gulf of Maine–Scotian Shelf and Labrador Sea, trace metal concentrations per volume filtered generally decrease with increasing particle size for all metals. In the upper 250 m of slope waters of the Gulf of Maine–Scotian Shelf and in the Labrador Sea, trace metal concentrations in all particle sizes are lower than in shelf waters. Higher particulate metal concentrations in shelf waters are consistent with an increase in the supply of these trace metals with proximity to continental sources. In addition, an increase in particulate trace metal concentrations in shelf waters with depth is attributed to an input from resuspended sediment.

Metals in airborne particulate matter in the industrial district of Santa Cruz, Rio de Janeiro, in an annual period

Abstract The main goal of this work is to assess the concentrations of total suspended particles (TSP) and airborne particulate trace metals in the Industrial District of Santa Cruz, Rio de Janeiro, Brazil, where the main pollution sources are the local industries. The sampling was performed using a high-volume pump. The TSP levels were determined by gravimetry and the metals by inductively coupled plasma atomic emission. A geometrical mean of 87±40 μg m−3 was determined for TSP for the period March 2001–February 2002, which is higher than both the Brazilian primary and secondary standards of air quality. Metals concentrations were compared with literature values for other regions of the world and with air quality standards of regulatory agencies. Mn, Fe, Zn, Cu, Cr and Al levels are higher than the reported values for other industrial and urban areas around the world. Mn, Cr and Ni concentrations are higher than the US-EPA standards. Cluster and principal component analysis were used to get some insight about the sources of metals and the correlations among them.