Woei-Lih Jeng

Sedimentary coprostanol in Kaohsiung Harbour and the Tan-Shui Estuary, Taiwan☆

Coprostanol in sediments from Kaohsiung Harbour and the Tan-Shui Estuary has been analysed. In the Kaohsiung Harbour sediments, coprostanol has a concentration range between 0.58 and 128 μg g−1 dry wt with a mean of 20.8 μg g−1 dry wt; higher concentrations are found near the mouths of rivers. Moreover, a significant log-log correlation is found between total coprostanol concentration and oil hydrocarbon concentration (r=0.803∗). In Tan-Shui Estuary sediments, coprostanol ranges in concentration from 1.00 to 230 μg g−1 dry wt with an average of 63.5 μg g−1 dry wt; relatively high levels of coprostanol (> 10 μg g−1) with 5β5β+5α cholestanol ratios > 0.7 indicate positive sewage pollution. This probably results from an input from the sewage outfall, anoxicity, shallow water depths, inadequate tidal flushing, etc. Additionally, highly significant correlations have been found for coprostanol and cholesterol (r=0.986∗) and for cholestanol and cholesterol (r=0.981∗); these relationships are thought to be mediated predominantly by sediment micro-organisms in the reducing environment.

Distribution of terrigenous lipids in marine sediments off northeastern Taiwan

Surface sediments on the continental margin off northeastern Taiwan have been analyzed for terrigenous lipids including n-alkanes, n-fatty alcohols, and sterols. Marine input to the sediments is particularly low based on the average n-C17/n-C29 alkane and n-C16/n-C28 fatty alcohol ratios, 0.15±0.13 and 0.13±0.06, respectively; this may be due to the fact that marine lipids are more prone to degradation than terrestrial ones. The study area has the highest plant wax n-alkane contribution (average carbon preference index 3.9±1.2) among the coastal marine areas surrounding Taiwan; lateral particle transport from the southern East China Sea shelf and river runoff from the east Taiwan coast are considered to be the major contributors. The distributions of plant wax n-alkane and n-alkanol concentrations normalized to total organic carbon (TOC) in the study area generally show maximum values on the upper slope of the southernmost Okinawa Trough, but not for phytosterols. Linear regression of TOC versus plant wax n-alkane concentrations show a weak relationship (r=0.64, p=0.001), and an even weaker relationship (r=0.42, p=0.05) between TOC and plant wax n-fatty alcohol concentrations is found. This could be attributed to several factors: (1) a complex input (not a point source) of terrigenous organic matter to the study area, (2) TOC also including marine organic matter, (3) temporal variations in river flow due to flooding, and (4) different rates of degradation for TOC and individual biomarkers. However, in spite of those factors, TOC and phytosterol concentrations are positively linearly correlated (r=0.85, p<0.001), implying that the dilution of phytosterols in terrigenous organic carbon with marine organic carbon with or without the phytosterols follows a nearly constant ratio, which is remarkable. In addition, the predominant source of diploptene in the sediments does not appear to be of higher plant origin.

Relationship between copper speciation in sediments and bioaccumulation by marine bivalves of Taiwan

This paper evaluates the relationships between copper species in sediments and accumulation by the purple clam (Hiatula diphos) and venus clam (Gomphina aeguilatera) collected from the field and culture (aquaculture) ponds in the polluted coastal area of Lukang, Taiwan. Sediment was sampled along with the molluscs, including oysters (Crassostrea gigas), purple clams (Hiatula diphos), rock-shells (Thais clavigera), venus clams (Gomphina aeguilatera), and hard clams (Meretrix lusoria), from two unique environments of Lukang during the period from August 1993 to July 1994. The data indicate that the total copper concentrations in sediments from culture ponds (185 microg g(-1)) was higher than those of the field (44.0 microg g(-1)). Copper species in sediments were analyzed by a sequential leaching technique. Results show that concentrations of various copper species in the sediments are in the range of 1.14 +/- 0.59 to 13.2 +/- 22.4 microg g(-1) and 0.36 +/- 0.24 to 133 +/- 36.7 microg g(-1) for the two environments, respectively. Also the exchangeable copper in sediment from culture ponds was 15 times higher than that from the field. In addition, the sum of exchangeable and copper carbonates had the highest percentages of copper in both the pond sediment (86.6 %) and the field sediment (50.7 %). Maximum copper concentrations (309 +/- 35.1 microg g(-1)) in oysters were much higher than those in the other benthic organisms by about 4-127 times. Similarly, the data also showed that copper concentrations in Thais clavigera were 12-32 times higher than those in other benthic organisms. Copper concentrations in various benthic organisms differed significantly (p < 0.05) from that in Thais clavigera. This capacity makes Thais clavigera a potential candidate for monitoring copper in marine sediments. In terms of copper species, the best correlation was generally obtained between copper carbonates in sediments and copper concentrations in Hiatula diphos (r = 0.886*). A strong multiple regression correlation (p < 0.05, r2 = 0.7894) also indicates that the copper carbonates may dominate as the available form of copper to Hiatula diphos from various environments in the Lukang coastal area under natural physicochemical conditions.

Coprostanol distribution in marine sediments off southwestern Taiwan.

One of the major industries in southern Taiwan is pigfarming along the Kaoping River; some two million animals are being raised along the river banks. Excretions from pigs, treated and untreated, are discharged directly into the river and eventually carried to the sea. Twenty-four surface sediments and one sediment core off southwestern Taiwan were analyzed to determine quantitatively the extent of coprostanol addition and its distribution and to obtain the input of coprostanol over the past. Geographically, the percent coprostanol is highest around the river mouth, and decreases to about 1% at the shelf break and about 0% at a distance of approximately 40 nautical miles (74 km) from the river mouth. The progressive seaward decline of percent coprostanol from the river mouth can be attributed to [1] dilution of coprostanol by uncontaminated sediment and/or sediment containing relatively lower levels of coprostanol, [2] dilution of coprostanol by biogenic sterols, and [3] probably degradation of coprostanol. Further, the Kaoping Canyon sediments contain relatively high percent coprostanol; this can be attributed to [1] a more direct input of the river sediments because the canyon is well aligned with the river, [2] currents in the canyon being alternate upcanyon and downcanyon which tend to keep sediments in the canyon, and [3] the possible blocking effect of a topographic high in the canyon. A sediment core exhibits comparatively higher percent coprostanol in the top 15 cm, indicating an increased input of coprostanol over the past 20 years.

The effect of a cyclonic eddy on the distribution of lithogenic particles in the southern East China Sea

Off northeastern Taiwan, the collision between the Kuroshio Current (KC) and the East China Sea (ECS) shelf forms a branch current (Kuroshio Branch Current) on the shelf, and the counterclockwise deflection of the subsurface Kuroshio water annually generates a cyclonic eddy, about 70 km in diameter, over the shelf-slope in summer. In this study, the total suspended matter collected from varying water depths over the eddy during August 1994 has been analyzed for Al, which is used as an indicator element to trace lithogenic particle transport. Simultaneously, the measurements of current field, using the Shipboard Acoustic Doppler Current Profiler, and hydrography have also been conducted on the same cruise during the seawater sampling. These offer an opportunity for direct examination of the relationships between circulation patterns and distributions of lithogenic particles to further establish a transport model for lithogenic particles. However, we must emphasize that this is a representative case for the export of terrigenous suspensions delivered from rivers, although the observation was made only in summer. The spatial distribution of particulate Al (PAI) in the upper water displays an Ω shape with high concentrations of PAI close to the Taiwan coast and around the eddy center. It suggests that Taiwan-derived riverborne particulates are the main source for the lithogenic particles in the upper water of the study area. Moreover, the PAI in the upper water is essentially constrained by the cyclonic eddy, and the entrainment and subsequent accumulation of lithogenic particles occur at the eddy center. The 6 μg/l contour of PAI in the upper water almost matches the western boundary of the main stream and branch of the KC across the ECS shelf-slope, and two concentration provinces of PAI can be identified from this contour: one to the west is larger and variable and the other to the east is smaller and uniform. This indicates that the main stream and branch of the KC may confine terrigenous particles to the inshore area where mixing of the lithogenic particle-rich coastal water and the clearer Kuroshio water occurs and may act as a barrier to the offshore transport of terrigenous particles to regions farther away from the coast, toward the north and east. In this study, a conceptual model for the transport of lithogenic particles in the water of the southern ECS is proposed according to the spatial distributions of PAI. This model suggests that the cyclonic eddy at the turning site of the KC may be the important conduit for the indirect transport of terrigenous particles from the ECS shelf and slope to the southern Okinawa Trough or the Pacific Ocean. This is also a valuable example of the role of the eddy system in regulating the distribution and transport of terrigenous particulates.

Hydrothermal signatures in the southern Okinawa Trough detected by the sequential extraction of settling particles

Sediment trap samples collected over 6 months at two depths within the southern Okinawa Trough (SOT) have been analyzed for phase associations of Al, Fe, Mn and Pb by six-stage sequential extraction (SSSE). The deeper samples are characterized by the presence of hydrothermal constituents (such as Mn and likely Fe and Pb), while shallower samples are representative of background-settling particles originating from laterally transported sediments. These results suggest that the extraction scheme is appropriate for detecting particles affected by hydrothermal emanations. Analytical results show that shallower and deeper samples have similar total Al contents and total Fe contents; by contrast, Mn and Pb are 1.7- and 1.6-fold higher in the deeper samples than in the shallower samples, respectively. Additionally, the two depths have almost the same phase associations for Al and Fe, but largely different phase associations for Mn and Pb. Compositional differences in Mn and Pb between the two depths depend essentially on the relative abundance of the fresh oxide fraction. The observed phase association suggests that Mn anomalies in the deeper samples are derived preferentially from adsorptive oxidation of dissolved hydrothermal Mn onto settling particles and/or incorporation of very fine Mn-enriched hydrothermal precipitates within settling particles. Pb anomalies in the deeper samples imply either a similar hydrothermal origin and/or scavenging of dissolved Pb from ambient water by newly formed oxides/hydroxides. The constant concentration of Mn within the deeper samples may reflect phase equilibrium between dissolved Mn and settling particles. Hydrothermally derived fluxes, defined as the fraction from hydrothermal contributions and/or indirectly by processes related to hydrothermal activities, have been estimated at 7.0F3.1 mg/m 2 /day for Fe, 2.3F1.0 mg/m 2 /day for Mn and 0.07F0.03 mg/m 2 /day for Pb. These fluxes are higher than those found at other hydrothermal systems owing to high loads of settling and suspended particles. D 2003 Elsevier B.V. All rights reserved.

Depuration of copper and zinc by green oysters and blue mussels of Taiwan.

This paper describes depuration processes of copper and zinc in green oysters (Crassostrea gigas) and in blue mussels (Mytilus smarangdium) collected from an environment with heavy copper contamination, and then transferred to natural clean seawater. Results show that the total loss of copper content per oyster is an exponential function of exposure time for the first 6 days with a depuration rate of 351 microg g(-1) day(-1) and then levels off. During this exponential decrease period approximately 67% of the copper accumulated in green oysters was depurated. However, when the copper contents in the oysters decreased from 2225 +/- 111 microg g(-1) to 344 +/- 18.7 microg g(-1) the depuration rates decreased from 245 microg g(-1) day(-1) to 0.08 microg g(-1) day(-1). This means that green oysters had a 16-fold higher copper depuration rate (351 microg g(-1) day(-1)) than normal oysters (21.5 microg g(-1) day(-1)) for the first 6 days. However, the depuration of accumulated copper and zinc by the mussels was a fast process in natural clean seawater. About 91% of the accumulated copper was lost during the first 6-day period; copper contents declined from 20.2 +/- 3.41 microg g(-1) to 1.80 +/- 0.21 microg g(-1). Only 36% of the accumulated zinc was lost during a depuration period of 6 days. Calculations show that the biological half-lives of copper in green and normal oysters were 11.6 and 25.1 days, respectively. The biological half-lives of zinc in green and normal oysters were 16.7 and 30.1 days, respectively. In spite of the relatively low initial copper content in blue mussels being 20.2 +/- 3.41 microg g(-1), the biological half-life is only 6.40 days. From these results it is important to emphasise that the fastest turnover rate is for copper in blue mussels. However, zinc is more retentive in blue mussels than copper.

Grain size effect on bound lipids in sediments off northeastern Taiwan

Two box-core sediments off the northeastern Taiwan coast have been collected and examined for the relationship between bound lipids and grain size in the mud fraction (<63 μm). No grain size effect was found for the concentrations of σn-alkanes, σn-fatty acids and σn-alcohols. The ratios of branched-chain to normal fatty acids increased progressively with decreasing particle size and correlated highly with BOC (bound organic carbon), suggesting an increasing bacterial input. Moreover, we observed an increase in the ratios of monounsaturated to saturated fatty acids with decreasing grain size, pointing to an increasing microbial contribution. Particularly interesting is phytol, which demonstrated a remarkable grain size effect; the phytol to BOC ratio increased sharply with decreasing particle size. Major sterols normalized to BOC increased progressively with a decrease in grain size and correlated highly with BOC. The results indicate that a plankton contribution to phytol and sterols increased as particle size decreased. The grain size effect is stronger for phytol than for sterols and branched-chain fatty acids in the sediments.

Alkanol and sterol degradation in a sediment core from the continental slope off southwestern Taiwan

Abstract A sediment core (ca. 36 cm in length and sectioned at 4 cm intervals) collected from the anoxic continental slope off southwestern Taiwan has been analyzed for alkanols and sterols in the extractable and bound forms to understand their degradation in this reducing environment during diagenesis. Generally speaking, the two compound classes (both extractable and bound) degrade faster in the upper core and slower in the lower core; however, extractable phytol degrades sharply from sections 1 to 2 and gradually from section 2 down. The calculated apparent rate constants (y−1) for the extractable phytol, Σn-alkanols, and Σsterols are respectively 0.015, 0.011, and 0.010; and those for the bound phytol, Σn-alkanols, and Σsterols are respectively 0.011, 0.007 and 0.007.The bound form is slightly less reactive than the extractable form.These constants are at least one order of magnitude lower than those reported for two shallow coastal marine sediments--Cape Lookout Bight and Peru, but are similar to or slightly lower than those reported for the anoxic Black Sea deep basin. The interesting result can be attributed to anoxicity which plays the most important role during lipid degradation in the sediment.

Comparative study of sterols in shelf and slope sediments off northeastern Taiwan

Abstract Bottom sediments and suspended matter from the shelf and slope areas off northeastern Taiwan were analyzed for sterol, n -alkanol and n -alkane compositions. The Σ(algal sterols/cholesterol) ratios (mean±1 σ ) were 1.00±0.31 ( n =7) for the shelf sediments, 3.29±0.61 ( n =7) for the slope sediments, and 1.54±0.19 ( n =3) for the suspended matter. The much higher proportion of cholesterol in the shelf sediments is most likely derived from mollusks in the relict sediments. An additional sterol source for the shelf sediments probably is suspended matter in the water column although the shelf has no apparent sedimentation. Results from phytol and n -alkanols suggest recent inputs of lipids from the water column to the shelf. The stanol/stenol ratios are lower for the older shelf sediments than for the younger slope sediments.