Terrestrial Particulate Matter Research Articles

Origins of suspended particulate matter based on sterol distribution in low salinity water mass observed in the offshore East China Sea

The molecular composition and distribution of sterols were investigated in the East China Sea to identify the origins of suspended particulate matter (SPM) in offshore waters influenced by Changjiang River Diluted Water (CRDW). Total sterol concentrations ranged from 3200 to 31,900pgL−1 and 663 to 5690pgL−1 in the particulate and dissolved phases, respectively. Marine sterols dominated representing 71% and 66% in the particulate and dissolved phases, respectively. Typical sewage markers, such as coprostanol, were usually absent at ~250km offshore. However, sterols from allochthonous terrestrial plants were still detected at these sites. A negative relationship was observed between salinity and concentrations of terrestrial sterols in SPM, suggesting that significant amounts of terrestrial particulate matter traveled long distance offshore in the East China Sea, and the Changjiang River Diluted Water (CRDW) was an effective carrier of land-derived particulate organic matter to the offshore East China Sea.

A refined dissolution method for rare earth element studies of bulk carbonate rocks

Extraction of primary geochemical signals from bulk carbonate rocks is a key task in palaeoenvironmental studies. REE behaviour is investigated during stepwise dissolution of carbonate rocks. The experiment is designed to achieve total carbonate dissolution in ten steps, aiming for approximately 10% of the total carbonate to be dissolved in each step using acetic acid. An additional eleventh step using excess acid completed each experiment. Results show that calcite is preferentially dissolved before dolomite though no significant effect on the REE pattern of the rock is observed. Secondary carbonate phases and adsorbates are likely to be dissolved at the beginning of the dissolution process but this does not increase REE concentration though the REE pattern may be altered e.g. lessening of negative Ce anomaly, altering of Eu anomaly, Y/Ho ratio and relative fractionation between LREE and HREE. Non-carbonate minerals e.g. terrestrial particulate matter, Fe–Mn oxyhydroxides and phosphates, are likely to be dissolved towards the end of the total dissolution, especially in the final excess acid step. This should increase REE concentrations and alter REE distribution patterns greatly. In contrast, solutions from intermediate steps are less contaminated. Further, compared with using 10% v/v acetic acid, the solutions obtained using 5%v/v acid return more pristine REE information from the carbonate.A proposed method for REE studies of bulk carbonate rocks requires an initial dissolution of 30%–40% followed by the sampling dissolution of 30%–40% of total carbonate using 5%v/v acetic acid to produce REE information considered to best represent that of the carbonate source water. Following these steps 20%–30% of the carbonate should remain undissolved, thus minimising contamination from non-carbonate minerals.

Utilization of terrestrial organic matter by the bivalve Corbicula japonica estimated from stable isotope analysis

Carbon and nitrogen isotopic ratios in tissue of the bivalve corbicula (Corbicula japonica) and particulate organic matter (POM) were measured along a salinity gradient in the Kushida Estuary, Japan. The bivalve exhibited a gradual isotopic enrichment from the uppermost estuarine site (σ13C=−24.8‰ and σ15N=8.6‰) to the marine site (σ13C=−16.1‰ and σ15N=11.8‰). Using the concentration-weighted mixing model, the bivalves’ food source is estimated from the isotope values for the bivalves and POM from terrestrial plants, marine phytoplankton and benthic microalgae. The results indicated that the contributions of benthic micro algae and phytoplankton were small, while terrestrial particulate matter is significantly important for the corbicula diet, although the contribution varies among sampling sites.

Selection of food sources by Ruditapes philippinarum and Mactra veneriformis (Bivalva: Mollusca) determined from stable isotope analysis

: Carbon and nitrogen isotopic ratios in the body of the bivalves Ruditapes philippinarum and Mactra veneriformis were measured to estimate the role of the bivalves in the ecosystem in an estuary. The isotopic signatures were compared with those obtained from particulate organic matter (POM) in the middle reach of the river, in the estuary, and off the estuary. Both the bivalves showed constant δ13C and δ15N values of approximately −17 and 10 that were significantly enriched compared with those for POM in the habitat (−25 and 4). The relative contributions of terrestrial organic matter to the POM in the habitat and to the bivalve diet were estimated: the former was approximately 90% while the latter approximately 10%. This indicates that the bivalves select marine POM from the organic matter available in their habitat, and play a minor role in the direct removal of terrestrial particulate matter. Temporal changes in δ13C and δ15N for both bivalves were small, but a distinct decrease in δ13C was observed following a period of heavy rain. During rainfall the concentration of terrestrial material increased in the habitat, and the bivalves would then have to change their food sources temporarily.

Organic tracers from biomass burning in atmospheric particulate matter over the ocean

Particulate matter from the atmosphere over the Atlantic Ocean along the South American and African Continents has been analyzed for organic tracers from natural and biomass burning emissions. The major biomarker compounds characterized are natural products from continental vegetation consisting primarily of epicuticular wax components. For example, n -alkanes ranged from C 25 to C 35 , with an odd carbon number predominance and carbon maxima (C max ) at 29 or 31. Concentrations of n -alkanes varied from 0.3 to 680 ng/m 3 . Nevertheless, n -alkanols are the dominant terrestrial tracers in almost all samples (concentrations from 0.1 to 780 ng/m 3 ) and ranged from C 22 to C 34 with an even carbon number predominance. Despite the major presence of the natural tracers, organic components from biomass burning emissions are also present in the particulate matter. The major tracers from this source are thermal degradation products from the biopolymer cellulose, namely the dianhydromonosaccharide derivatives levoglucosan , galactosan, and mannosan. In general, the concentrations of levoglucosan, the major derivative from this source in all samples, varied from 0.0008 to 0.15 ng/m 3 in atmospheric samples collected over the ocean and from 0.04 to 4860 ng/m 3 in terrestrial particulate matter, used as reference in this study. Dehydroabietic acid , another marker compound emitted from burning of Gymnosperm fuel, is also detectable in most oceanic samples at concentrations ranging from 0.0001 to 0.4 ng/m 3 , whereas in terrestrial aerosol particulate matter, this component is present at much higher concentrations (0.23–440 ng/m 3 ). The presence of these tracers in atmospheric particulate matter over the ocean confirms the long-range transport of smoke from biomass burning off the continents.

Biogenic flux of Al to sediment in the central equatorial Pacific Ocean: Evidence for increased productivity during glacial periods

We examined the flux of Al to sediment accumulating beneath the zone of elevated productivity in the central equatorial Pacific Ocean, along a surface sediment transect at 135°W as well as downcore for a 650 kyr record at 1.3°N, 133.6°W. Across the surface transect, a pronounced, broadly equatorially symmetric increase in Al accumulation is observed, relative to Ti, with Al/Ti ratios reaching values 3–4 times that of potential detrital sources. The profile parallels biogenic accumulation and the modeled flux of particulate 234Th, suggesting rapid and preferential adsorptive removal of Al from seawater by settling biogenic particles. Normative calculations confirm that most Al is unsupported by the terrigenous fraction. The observed distributions are consistent with previous observations of the relative and absolute behavior of Al and Ti in seawater, and we can construct a reasonable mass balance between the amount of seawater‐sourced Al retained in the sediment and the amount of seawater Al available in the overlying column. The close tie between Al/Ti and biogenic accumulation (as opposed to concentration) emphasizes that biogenic sedimentary Al/Ti responds to removal‐transport phenomena and not bulk sediment composition. Thus, in these sediments dominated by the biogenic component, the bulk Al/Ti ratio reflects biogenic particle flux, and by extension, productivity of the overlying seawater. The downcore profile of Al/Ti at 1.3°N displays marked increases during glacial episodes, similar to that observed across the surface transect, from a background value near Al/Ti of average upper crust. The excursions in Al/Ti are stratigraphically coincident with maxima in both bulk and CaCO3 accumulation and the excess Al appears to not be preferentially affiliated with opaline or organic phases. Consistent with the similar behavioral removal of Al and 234Th, the latter of which responds to the total particle flux, the Al flux reflects carbonate accumulation only because carbonate comprises the dominant flux in these particular deposits. These results collectively indicate that (1) Al in biogenic sediment and settling biogenic particles is strongly affected by a component adsorbed from seawater. Therefore, the common tenet that Al is dominantly associated with terrestrial particulate matter, and the subsequent use of Al distributions to calculate the abundance and flux of terrestrial material in settling particles and sediment, needs to be reevaluated. (2) The Al/Ti ratio in biogenic sediment can be used to trace the productivity of the overlying water, providing a powerful new paleochemical tool to investigate oceanic response to climatic variation. (3) The close correlation between the Al/Ti productivity signal and carbonate maxima downcore at 1.3°N suggests that the sedimentary carbonate maxima in the central equatorial Pacific Ocean record increased productivity during glacial episodes.