Seawater Particulate Matter Research Articles

Energy dispersive X‐ray fluorescence methodology and analysis of suspended particulate matter in seawater for trace element compositions and an intercomparison with high‐resolution inductively coupled plasma‐mass spectrometry

AbstractA modification of energy dispersive X‐ray fluorescence (ED‐XRF) for analysis of trace element concentrations in suspended particulate matter (SPM) in seawater and intercomparison with high‐resolution inductively coupled plasma‐mass spectrometry (HR ICP‐MS) is presented. Approximately 250 SPM samples were collected on polycarbonate track‐etched filters in the Indian Ocean during the U.S. CLIVAR/CO2 Repeat Hydrography meridional section I09N cruise in 2007. Samples were first analyzed by ED‐XRF, a nondestructive technique, for Al, P, Ti, Mn, Fe, Ni, Cu, and Zn and subsequently digested and quantified by HR ICP‐MS, creating two blind, basin‐scale data sets used for a paired statistical comparison. Our results found (1) ED‐XRF analysis using thin‐film principles can quantify the elemental composition of SPM at nanomolar concentrations found in the open ocean; (2) there was excellent agreement between ED‐XRF and HR ICP‐MS analyses for Al, Fe, and Mn and good agreement for P and Ti; (3) analytical differences were the largest for Cu, Ni, and Zn; (4) HR ICP‐MS methods have lower detection limits for most elements when compared to the ED‐XRF; (5) ED‐XRF analysis has a closer agreement to reported values for the NIST SRM 2783 standard and lower relative standard deviations when compared to the HR ICP‐MS. We recommend continued refinement of nondestructive ED‐XRF methods as this would allow for the easy exchange of filtered samples between lab groups for intercalibration and intercomparison of basin‐scale hydrographic cruises and archival for future analysis.

The use of wide-band transmittance imaging to size and classify suspended particulate matter in seawater

An in situ particle imaging system for measurement of high concentrations of suspended particles ranging from 30μm to several mm in diameter, is presented. The system obtains quasi-silhouettes of particles suspended within an open-path sample volume of up to 5cm in length. Benchmarking against spherical standards and the LISST-100 show good agreement, providing confidence in measurements from the system when extending beyond the size, concentration and particle classification capabilities of the LISST-100. Particle-specific transmittance is used to classify particle type, independent of size and shape. This is applied to mixtures of oil droplets, gas bubbles and oil-coated gas bubbles, to provide independent measures of oil and gas size distributions, concentrations, and oil-gas ratios during simulated subsea releases. The system is also applied to in situ measurements of high concentrations of large mineral flocs surrounding a submarine mine tailings placement within a Norwegian Fjord.

Seasonal and spatial variability of light absorption by suspended particles in the southern Baltic: A mathematical description

Abstract This paper analyses the relationships between the light absorption coefficients at 440 nm ap(440) for particles suspended in the surface waters of the southern Baltic Sea and the concentrations of some optically significant constituents in these waters. The analysis covers two main groups of particles: phytoplankton and non-algal. For this purpose we use the extensive database of optical measurements acquired from 2006 to 2013 during 40 cruises of r/v Oceania in various regions of the southern Baltic: open waters, coastal waters, the Gulf of Gdansk, the Pomeranian Bay and river mouths. Expressions are derived for each of these regions to describe the seasonal variations of the dependence of the light absorption coefficients for phytoplankton aph(440) and non-algal particles aNAP(440) on concentrations of chlorophyll a (Tchla) and suspended particulate matter in sea water (SPM). With a knowledge of these dependences, one can determine the overall absorption coefficient for all suspended particles in any part of the Baltic Sea in particular seasons from known Tchla and SPM concentrations using the relationship ap(440) = aph(440) + aNAP(440) = f(Tchla, SPM). These dependences reflect the characteristics of a study area and season, and their application increases the accuracy of determination of the overall absorption properties of suspended particles and their main constituents as confirmed by statistical error reduction, e.g. standard error factor falls from 1.46 to 1.38. The relationships derived in this work can be applied in the local remote sensing algorithms used for monitoring the southern Baltic.

Metal Ions and Hydroperoxide Content: Main Drivers of Coastal Lipid Autoxidation in Riverine Suspended Particulate Matter and Higher Plant Debris

Autoxidation is a complex abiotic degradation process, and while it has long been known and well studied in biological compounds, it has been widely overlooked in environmental samples and as a part of environmental processes. With recent observations showing the magnitude of the involvement of autoxidation in coastal environments, it has become critical to better understand how and why this degradative process takes place. At the riverine/marine interface, recent findings evidenced a spike in autoxidation rates upon the arrival of suspended particulate matter in seawater. In this study, we aimed at identifying autoxidation-favoring factors in vitro by analyzing suspended particulate matter incubated under different conditions. If metal ions have long been known to induce autoxidation in biological systems, we show that they indeed induce autoxidation in particulate matter incubated in water, but also that the content in photochemically-produced hydroperoxides in suspended particulate matter is crucial to the induction of its autoxidation in water.

Biomarkers derived from heterolytic and homolytic cleavage of allylic hydroperoxides resulting from alkenone autoxidation

Laboratory incubation of alkenone mixtures with tert-butyl hydroperoxide and di- tert-butyl nitroxide (radical initiator) in hexane, as a means to simulate alkenone autoxidation processes, rapidly led to the formation of allylic hydroperoxides, whose presence was recently demonstrated in Emiliania huxleyi cells. After incubation in seawater and subsequent reduction with NaBH 4 (to reduce residual hydroperoxides before analysis), these reaction products quickly disappeared and were replaced by complex mixtures of n-alcohols, fatty acids, alkyldiols and hydroxyacids. Methyl alkenones produced saturated n-alkan-1-ols and fatty acids ranging from C 13 to C 16 and two series of C 13−C 16 (ω-1)-hydroxyacids and (1,ω-1)-diols. Ethyl alkenones also afforded C 13−C 16 saturated n-alkan-1-ols and fatty acids, accompanied by the production of C 14−C 17 (ω-2)-hydroxyacids and (1,ω-2)-diols. Deuterium labelling allowed us to show that most of the n-alkan-1-ols, hydroxyacids and alkyldiols resulted from the reduction during the NaBH 4 treatment of the corresponding aldehydes, ketoxyacids and ketoxyaldehydes formed from heterolytic or homolytic cleavages of allylic hydroperoxyl groups resulting from the oxidation of the double bonds of di- and triunsaturated alkenones. Amongst these products, the (ω-1)- and (ω-2)-hydroxyacids formed after NaBH 4 reduction of the (ω-1)- and (ω-2)-ketoxyacids were selected as potential biomarkers for alkenone autoxidation. Re-examination of lipid extracts of post-bloom seawater particulate matter samples from the DYFAMED station in the Ligurian Sea (where strong autoxidative alteration of the lipid distributions had previously been detected) showed the presence of significant amounts of 12-hydroxytetradecanoic, 13-hydroxytetradecanoic, 14-hydroxyhexadecanoic and 15-hydroxyhexadecanoic acids thus providing good evidence that these autoxidative processes occur in natural samples.

Polycyclic aromatic hydrocarbon analysis in different matrices of the marine environment

Polycyclic aromatic hydrocarbons (PAHs) were determined in marine samples of various types, i.e. seawater, sediment and mussel homogenate samples. The samples were spiked with standard PAH mixtures in both polar (acetonitrile) and non-polar ( i-octane) solvents, then extracted. Extraction from seawater was performed by liquid/liquid extraction to hexane (LLE) and with solid phase extraction (SPE) discs. The water samples were filtered and unfiltered seawater, and redistilled water for comparison. The discs with PAHs adsorbed from water samples, and also the sediment and mussel homogenate samples, were extracted with acetonitrile by sonication. PAHs in the disc extracts and from the LLE were cleaned-up using TLC and next determined by GC/MS/IT (with ion-trap) and HPLC-DAD/UV. The analytical procedures were verified with deuterated PAH standard mixtures. The large differences in PAH recoveries (from 12 to 86% for sum, and from 3 to 135% for particular PAHs) do not depend solely on the type of matrix and analytical procedure applied (e.g. standard solvent, volume of evaporated sample), but also on the concentration and molecular structure of the analyte. Usually, only a fraction of each PAH content in the matrix is determined, depending on the particulate matter in seawater and the sorption properties of the solid matrix. The recoveries of deuterated PAHs are higher than those of non-deuterated compounds.

Evaluation of a protocol for the quantification of black carbon in sediments

Formation of highly condensed black carbon (BC) from vegetation fires and wood fuel combustion presumably transfers otherwise rapidly cycling carbon from the atmosphere‐biosphere cycle into a much slower cycling geological form. Recently reported BC fractions of total organic carbon (TOC) in surficial marine sediments span a wide range (2‐90%), leaving it presently unclear whether this variation reflects natural processes or is largely due to method differences. In order to elucidate the importance of BC to carbon burial the specificity of applied methods needs to be constrained. Here the operating range and applicability of a commonly used chemothermal oxidation (CTO) method is evaluated using putative BC standards, potentially interfering substances, and natural matrix standards. Test results confirm the applicability of the method to marine sediments. Integrity tests with model substrates suggest applicability to low‐carbon soils but only with a lower specificity to seawater particulate matter. The BC content of marine sediment samples in a set of studies employing the CTO method proved to be consistent with associated geochemical information. The radiocarbon content of the BC isolate in an environmental matrix standard was shown to be similar to the radiocarbon signature of pyrogenic polycyclic aromatic hydrocarbons (PAHs), here serving as molecular markers of combustion (fraction modern fM of BC was 0.065 ± 0.014 and of PAHs 0.056 ± 0.020), while being clearly distinct from the radiocarbon content of the bulk TOC (fM = 0.61 ± 0.08). Urgent questions such as the global accumulation rate of black carbon in soils and sediments may prove approachable with the chemothermal oxidation technique of BC quantification.

Airborne polarized lidar detection of scattering layers in the ocean

A polarized lidar technique based on measurements of waveforms of the two orthogonal-polarized components of the backscattered light pulse is proposed to retrieve vertical profiles of the seawater scattering coefficient. The physical rationale for the polarized technique is that depolarization of backscattered light originating from a linearly polarized laser beam is caused largely by multiple small-angle scattering from particulate matter in seawater. The magnitude of the small-angle scattering is determined by the scattering coefficient. Therefore information on the vertical distribution of the scattering coefficient can be derived potentially from measurements of the time-depth dependence of depolarization in the backscattered laser pulse. The polarized technique was verified by field measurements conducted in the Middle Atlantic Bight of the western North Atlantic Ocean that were supported by in situ measurements of the beam attenuation coefficient. The airborne polarized lidar measured the time-depth dependence of the backscattered laser pulse in two orthogonal-polarized components. Vertical profiles of the scattering coefficient retrieved from the time-depth depolarization of the backscattered laser pulse were compared with measured profiles of the beam attenuation coefficient. The comparison showed that retrieved profiles of the scattering coefficient clearly reproduce the main features of the measured profiles of the beam attenuation coefficient. Underwater scattering layers were detected at depths of 20-25 m in turbid coastal waters. The improvement in dynamic range afforded by the polarized lidar technique offers a strong potential benefit for airborne lidar bathymetric applications.

Thin-layer chromatography-pyrolysis-gas chromatography-mass spectrometry: a multidimensional approach to marine lipid class and molecular species analysis.

A new multidimensional chromatographic method is described in which material separated into lipid-class bands on silica-coated quartz thin-layer chromatography (TLC) rods (Chromarods) is desorbed using a pyrolysis unit interface and introduced directly into a gas chromatograph-mass spectrometer for molecular species analysis. Steryl esters, wax esters, hydrocarbons, ketones, and fatty-acid methyl esters (FAMEs) are thermally desorbed without pretreatment. In order to desorb free sterols, monoacylglycerols (MAGs), aliphatic alcohols, and free fatty acids, the esters are converted to trimethylsilyl derivatives on the rod. Triacylglycerols and phospholipids are converted to FAMEs by thermochemolysis with tetramethylammonium hydroxide. The method's utility is demonstrated with lipids from seawater particulate matter by first confirming the identity of lipid bands with the appropriate standards. The wax ester-steryl ester TLC band contained no more than 8% steryl esters. Wax esters of up to C42 are detected. In six individual acyl lipid classes, C14-C22 fatty acids are detected with C16 acids predominant in all but wax esters. C16-C22 MAGs are identified in the complex acetone-mobile polar lipid band. The method successfully extends the scope of latroscan TLC-flame-ionization detection on Chromarods, which is a widely used technique for lipid-class analysis. Modification of the pyrolysis probe to handle intact TLC rods is a future objective.

Factors controlling the vertical and spatial transport of metal-rich particulate matter in seawater at the outfall of bauxitic red mud toxic waste

The spatial and vertical distribution of metal-rich particulate material is studied in the Antkkyra Bay (Gulf of Corinth Greece), where bauxitic red mud is discharged from an alumina processing plant. It is revealed that a significant amount of the metalliferous mud released on the seafloor enters the water column in the form of suspended particulate matter. At least at certain periods of the year suspended particulate matter is trapped at certain water layers due to the water mass stratification. It is demonstrated that the red mud reaches the seasurface, upwelling being a major process responsible for its upward dispersion. In the upper seawater layers the suspended matter is transportedin a NW-SE direction whereas in the deeper layers it is transported in a NE-SW direction.

Hydrocarbon and coprostanol levels in seawater, sea-ice algae and sediments near Davis station in eastern Antarctica: A regional survey and preliminary results for a field fuel spill experiment

A survey of hydrocarbons and the sterol coprostanol, together with a hydrocarbon degradation experiment, was conducted in a coastal marine environment in East Antarctica. Aliphatic hydrocarbon levels in sea-ice algae were 1.9–12.5 mg m −2 and in seawater particulate matter 0.07–0.17 μg l −1. Sea-ice algae contained the diatom biomarker, the highly branched isoprenoid (ip) diene ipC 25:2, and Southern Ocean seawater particulate matter samples were distinguished from near shore samples by the presence of nC 21:6. Sea-ice algae and seawater particulate matter samples showed a predominance of even chain n-alkanes. Hydrocarbon levels in sediment samples from anoxic fjord basins were high (45–48 μg g −1) compared to a sub-tidal marine sample (0.7 μg g −1), and were predominantly of bacterial origin. Contaminants detected were linear alkyl benzenes in sewage effluent from Davis station, and polycyclic aromatic hydrocarbons (PAH) which were present in very low levels (parts per trillion) throughout the environment. High levels of 2,6-dimethylnaphthalene were found in anoxic sediment from Ellis Fjord and may arise from a novel bacterial source. Coprostanol concentrations in sediments ranged from 67 to 1280 ng g −1. A dual origin is proposed from marine mammalian faeces and, at several sites, from conversion of algal-derived sterols by anaerobic bacteria. Future studies examining the impact of human sewage from scientific bases or other ventures should use care in interpreting results when such high baseline values, from marine mammalian input, may occur naturally around the Antarctic coast. The potential exists, however, for the technique to distinguish between human and mammalian inputs through measurement of the coprostanol to epicoprostanol ratio, particularly if undertaken with appropriate comparative sampling. Results for a hydrocarbon degradation experiment where a light fuel was applied to an Antarctic beach, showed loss of up to 99% of the fuel within 2 months, mainly by volatilization.

Phosphorus dynamics associated with phytoplankton blooms in eutrophic Mikawa Bay, Japan

Changes in the phosphorus components of the particulate matter in seawater were studied in the eutrophicated waters of Mikawa Bay, Japan, during summer 1981. The contents of particulate phosphorus and hot-water extractable intracellular phosphorus displayed remarkable changes associated with phytoplankton blooms caused by wind-induced or upwelling-associated nutrient enrichment from the bottom water layers. Nanoplankton 25 μm varied from 9 to 49%, the peak values being attained under red-tide conditions. The capacity for phosphorus storage in cells was low in nanoplankton cells, high in large phytoplankton species. Differences in rates of phosphorus storage and growth between nanoplankton and large phytoplankton accounted for fluctuations in particulate phosphorus which were closely associated with fluctuations in phytoplankton blooms in Mikaw Bay.

Cadmium and Lead Cycling Between Water, Sediment, and Biota in an Artificially Contaminated Mud Flat on Borkum (F.R.G.)

A ‘Bremerhaven caisson' was used to investigate the interactions of cadmium (Cd) and lead (Pb) with sea water, particulate matter (SPM), sediments, and biota in an enclosed (13m2) tidal mud flat area on the island of Borkum (FRG). Artificial contamination was accomplished by injecting Cd as a chloride and Pb as a nitrate into the caisson so as to maintain metal concentrations of 100 µg/1 in the inflowing water of each tidal cycle for 25 days. Each component of the system was sampled at selected intervals inside and outside the caisson. The results show that most (85%) of the injected Cd remained in the soluble phase whereas most (90%) of the Pb was transferred to the particulate phase. Cyclic changes in particulate Cd and Pb concentrations occur and indicate that Cd is progressively taken up by the SPM over each tidal cycle, but after an initial rapid uptake, particulate Pb concentrations remain relatively constant in the system. In the sediments, Cd concentrations decrease with depth but increase with time, with the highest increases occurring in the surface sediment layers. Lead concentrations initially remain constant with depth, but eventually Pb becomes enriched in the top 3 cm of the sediments. Biota show an exponential increase in Cd and Pb during the experiment. Lead is enriched relative to Cd by a factor of 2 in mussels despite its low level in the dissolved phase. Infaunal benthic species have lower metal concentrations than the filter feeders.

Some analyses of lipid classes in marine organisms, sediments and seawater using thin-layer chromatography—flame ionisation detection

Applications of the silica gel Chromarod-Iatroscan TH-10 thin-layer chromatography—flame ionisation detection (FID) system for identifying and quantifying the non-polar lipids in a variety of marine samples are presented. Excellent results can be obtained with a speed and sensitivity which is lacking in other analytical procedures. However, the non-linearity of the FID response at the low loadings (< 2 μg) required for most samples of interest makes the use of FID calibration curves mandatory. Seawater and sediment samples contain large amounts of polar lipids, degraded organic matter and pigments which can also interfere with the lipid analyses. Lipid compositional data are presented for the unicellular algae Thalassiosira eccentrica and Emiliania huxleyi, the marine copepods Paralabidocera antarctica and Calanus finmarchicus, seawater particulate matter from northern Tasman Sea waters off the East Australian coast and sediments from Ace Lake, Antarctica and the Great Barrier Reef of Australia.

Problems with accurate carbon measurements in marine sediments and particulate matter in seawater: A new approach1

The determination of carbon concentrations in marine sediments and particulate matter is hindered by the difficulty in analytically partitioning the total carbon between organic carbon and carbonate carbon phases. Attempts to “selectively” remove organic carbon by burning the sample at 500°C, or carbonate carbon by acidifying with HCl, usually affect the carbon of the remaining phase as well.A new approach permits direct measurement of both organic and carbonate carbon in a single sediment sample. The carbonate carbon concentration is determined from the CO2 evolved during phosphoric acid treatment. Subsequently, a concentrated dichromate/sulfuric acid solution is added to the remaining sediment‐acid mixture, and the CO2 liberated from the oxidation of organic carbon is measured. Total carbon is calculated as the sum of organic and carbonate carbon. A LECO carbon analyzer is modified so that the amount of CO2 evolved can be measured by the instrument’s thermal conductivity detector. In addition, total carbon content is determined on another subsample using the LECO dry combustion furnace. This provides a check on the values determined by the H3PO4/dichromate technique. Any other commercially available instrument relying on combustion furnace and thermal conductivity or infrared absorption for CO2 detection could be converted in an analogous manner.

Solubility behavior of atmospheric 7Be in the marine environment

The solubility of natural 7Be from air particulate matter in seawater was determined as a function of time. Adsorption of the thus solubilized 7Be on a variety of substrates was investigated. 7Be appears to be strongly adsorbed on suspended matter and inorganic materials at high suspended loads (> 20 mg 1 −1), but at natural levels (∼1 mg 1 −1) is only partially adsorbed. Further, at natural concentrations of suspended matter, adsorption of 7Be appears to be directly proportional to suspended load. Because a non-steady-state flux of 7Be to the bottom could be expected over its 53-day half-life, 7Be may be a poor tracer of sedimentation rates and sediment redistribution processes.

Some observations on the effect of ozone treatment on suspended particulate matter in seawater

Effects of ozone treatment on suspended particles in seawater have been observed. The observations consist of measuring the particle size distribution using an electronic particle counter before and after treating the sample with ozone. Three kinds of response have been observed in the laboratory and in the field: (i) the total elimination of a peak in the size spectra; (ii) a shift of a peak to a smaller size with correspondingly less volume; and (iii) a mild decrease in the total particle concentration. Our interpretation of these responses as observed in the field are respectively: (i) phytoplankton with a very small amount of refractory structural materials (e.g. naked flagellates); (ii) particles that individually contain both refractory and non-refractory components (e.g. diatoms); and (iii) primarily non-organic and refractory organic materials.

A sediment trap experiment in Funka Bay, Japan: “upward flux” of particulate matter in seawater

Sediment trap experiments were carried out ten times in one year (1977) at three depths in Funka Bay. The material obtained in the traps was analyzed for metals, organic elements and radionuclides, together with the suspended matter in the overlying water column. Two groups with extremely different downward fluxes were found, a group with a small flux increasing with depth, and another with a large flux that is rather constant with depth and is observed only in winter. The flux in winter, and sometimes in the bottom layer below the summer thermocline was larger than the net sedimentation rate for total dry matter or for each chemical constituent. The flux was also larger than the net removal flux for 234Th. A most striking fact is that the specific activity of short-lived 234Th did not decrease in winter, indicating that the large flux in winter was not caused by the re-suspension of old bottom sediments. The concentration of suspended matter in winter was not much greater than that in other seasons. These results suggest that the downward flux observed in sediment trap experiments is not a net removal rate and that there must be an upward particulate flux in the bay.

Upwelled spectral radiance distribution in relation to particulate matter in sea water

Spectral analysis of water color and concurrent measurements of the relative concentration of various particulate and dissolved constituents within a broad range of water types are necessary to quantify ocean color observations and successfully relate them to various biological and physical processes that can be monitored by remote sensing. Some of the results of a Nimbus-G prelaunch cruise in connection with the Coastal Zone Color Scanner (CZCS) experiment, which was carried out in the Gulf of Mexico in October 1977, are presented and discussed. Based upon a small but diverse sample of near-surface measurements, it appears possible to estimate total suspended particulate matter (SPM) to useful accuracies by forming ratios of the spectral radiances measured at wavelengths falling near the centers of certain CZCS bands, viz., 440 nm: 550 nm and 440 nm : 520 nm. Furthermore, the analysis suggests a very high degree of covariation between SPM and phytoplankton pigments except for certain well-defined special cases.

The distribution of particulate matter in the Atlantic Ocean

We have determined the dry weight of suspended particulate matter in seawater in a section through the western Atlantic Ocean from 75°N to 52°S. The concentrations, operationally defined as that weight retained on 0.6-μm and 0.4-μm pore size Nuclepore filters, contained in 1 kg of seawater, range from 5 to 300 μg/kg and show readily explainable regional features. High concentrations are found in surface waters and in association with radpidly moving bottom waters in the Denmark Straits overflow and in Antarctic bottom waters to 15°S. Low concentrations, <12 μg/kg, characterize the mid-water regions of the sub-tropical gyres. High concentrations are seen in sinking Labrador Sea water and in a plume extending at least a kilometer off the bottom at 35°N–40°N where the cruise track intersects the North Atlantic gyre. It is doubtful whether this important phenomenon could be observed by any means other than through particulate observations, either optical or gravimetric, and this provides a unique insight into the scale of vertical turbulent processes.