Abstract This study is to investigate the spatial and temporal variabilities of geochemical and carbon isotopic compositions of particles collected in the region off northeast Taiwan. Organic carbon isotopic compositions (d13Corg), total organic carbon content (TOC) and C/N ratio were determined in sediment particles collected at different water depths from three time-series sediment traps (at T12, T13, and T18 stations, respectively). The results showed abnormally high mass fluxes than those previously found. Generally they increase with water depths, implying both the transport from Lanyang-Hsi River and the resuspension from the seafloor. TOC contents range from 0.5 to 1.5wt% and decrease with depths. This can be attributed to changes in the surface productivity, lateral transport and organic preservation. The organic carbon isotopic compositions range between -21 and -25o/oo, which falls well within the d13Corg values of continental margin sediments. The lower d13Corg values at T12 station than those at T13 station can be attributed to the large terrestrial inputs. It is noted that d13Corg values decrease with depths, suggesting a significant contribution of the horizontal transport of particles to the settling process.

Previous studies have shown that the continental shelf and slope area off northeastern Taiwan is a region where the material exchange processes between the East China Sea and open ocean are most rigorous under the influences of the Kuroshio and the monsoons. In order to understand the topographic effects on the particulate flux and the transport path of the settling particles in this region, this study has conducted a series of field measurements using time-series sediment traps and current meters as tools. The temporal and spatial variations on the current, the particulate flux and the particle-size distribution as well as the activity and flux of 210 Pb and 210 Po are presented in this thesis. The biological productivity and the runoff of main rivers from Taiwan were not correlated with the particulate fluxes in our study area. However, the variations of the particulate flux in the canyon and on the slope areas were clearly affected by the tidal currents, showing good positive correlation with their amplitudes. The particulate, 210 Pb and 210 Po fluxes all showed an increase toward the ocean bottom but a decrease away from the shore, suggesting that the transports of particle and particle reactive elements were strongly influenced by the lateral transport process in the study area. Highest fluxes were observed in the Mien-Hua Canyon(MHC) and the lower slope southwest of the canyon. Intermediate values were observed in the South Okinawa Trough and the North Mien-Hua Canyon(NMHC). The intercanyon slope and the shallow traps in the NMHC had lowest values. The particulates and particle reactive elements were transported out of the shelf or upper slope area essentially through the MHC toward the slope southwest of the canyon. The NMHC and the intercanyon area were not major pathways for these materials. The fluxes of particle, 210 Pb and 210 Po in the study area were generally at least an order of magnitude greater than those observed from other continental margins in the world, except for the lowest values at the intercanyon station and the shallow water in the NMHC. Thus the continental margin off northeastern Taiwan is one of the most important areas for material exchanges with open oceans in the world. The trapped particulates were mainly silt with variable sand fractions. High sand contents were observed in the MHC and the lower slope southwest of the canyon, the intermediate values were in the outlet of the MHC and the NMHC, and the lowest in the South Okinawa Trough. This shows that the sand content decreases awayfrom the shore. On the contrary, silt and clay fractions in percent increase away from the shore. Under the influence of tidal currents, the settling sand particles in the MHC and its adjacent lower slope were laterally transported from resuspended sandy sediments of the continental shelf and upper slope area adjoining the head of the MHC. The fluxes of sand, silt and clay all decreased toward the South Okinawa Trough but increased toward the bottom. This particle-size distribution pattern also reflected the effect of lateral transport process in the study area. Variations of the 210 Pb activity in this study area were generally correlated inversely with the particulate flux and the sand content, indicating the effect of dilution of the mass flux and the sand content, but were positively correlated with the silt and clay contents because they were major 210 Pb scavengers. No apparent correlations of 210 Po with the mass flux and the three particle-size fractions were observed, suggesting that the variation of 210 Po activity was not related to the mass fluxes or the three particle-size fractions. High 210 Pb activities were found to be associated with high contents of POC, Mn and Fe. Correlations of 210 Pb with both Mn and Fe indicate that the oxide and hydroxide precipitates of Mn and Fe supplied from sediments on the continental shelf, upper slope area and submarine hydrothermal activities might serve as important mechanisms for enhanced 210 Pb scavenging. The relationship between the 210 Pb activity and the POC content might reflect either the settling mode of the fine particles incorporated with fecal pellets or aggregates, or sharing the same source with fine particles. The variatio ns of 210 Po activity were not correlated with Mn, Fe, major components or biogenic components, implying that the association of 210 Po with biogenic components might be masked by the enormous terrigenous materials. Except for the upper-trap samples collected at the intercanyon slope and the NMHC, the 210 Po activity was lower than the 210 Pb activity with 210 Po/210 Pb ratios less than unity. Based on comparisons of 210 Pb and 210 Po with relevant parameters and references of past studies, we can propose several possible mechanisms to explain why the ratios were less then unity: 1. 210 Pb was preferentially scavenged by advecting and settling particulates of terrigenous origin. 210 Po, known to be biophilic, might remain associated with the suspended organic particulates which could be dissolved or not settling. Moreover, the oxide and hydroxide precipitates of Mn and Fe in the study area would further enhance the scavenging of 210 Pb. 2. The particulates in suspension were favorable for differentiation between 210 Pb and 210 Ponuclides while those settled in sediments would allow them to grow toward the secular equilibrium. Therefore, the trapped particulates might be in frequent suspension and short in deposited sediments during their lateral transport. 3. The 210 Pb supplied from the East Asia aerosol in large quantity was accumulated in water column abd carried by the Kuroshio to the study area. The intrusion and eddies of Kuroshio off northeastern Taiwan could bring large amount of 210 Pb into the region of continental shelf and slope, allowing particulates to scavenge 210 Pb more effectively from the surrounding water. The upper trap in the NMHC and that in the intercanyon site yield lowest particulate flux but highest POC content. With less terrigenous material and more biogenic components in these samples, 210 Po/210 Pb ratios were greater than unity and variations of 210 Pb activity were hardly correlated with those of POC contents but were inversely correlated with those of Mn contents. However, the 210 Po activities of upper trap at the intercanyon site were well positively correlated with POC and PIC contents, indicating effects of the fresh biogenic particles. Based on the mass balance calculations of particulate and 210 Pb fluxes, current data and other related data gathered in this study, we may infer the sedimentation dynamics and transport path of the settling particles below 300m depth in the study area. Under the influence of tidal oscillation, terrigenous sediments on the shelf and the shelf break as well as the upper slope would be resuspended and carried into the MHC and transported further away. Most of the sand particles would deposit in the canyon while part of the silt and clay would be transported to the South Okinawa Trough directly and the rest to the lower slope southwest of the MHC. The particulate flux at the lower slope southwest of MHC might also have a portion of particulates swept from the upper slope by the Kuroshio eddies. As the NMHC and the intercanyon sites are located in the central area of the Kuroshio eddies, the particulates from the continental shelf and upper slope area would be blocked, resulting in very low particulate fluxes. High particulate fluxes observed in the lower NMHC trap should largely be due to resuspension of the sediments from the banks of the canyon.

Abstract ¡@¡@The present study was undertaken to understand the accumulation of PCBs in the marine environment of Taiwan. Samples including oyster drills, oysters, sediments and seawater were collected from the West coast of Taiwan and analyzed by GC/ECD and GC/MS. ¡@¡@The concentration of PCBs in sediments was 31.05¡ã406.38 pg/g dry wt with the highest one at Tong-Kung. The PCBs in cultural oysters from Tong-Kung was 3.80 pg/g wet wt. Concentrations of PCBs in wild oysters from Tai-Si, Chi-Ku, and Pu-Dai were 123.57 pg/g wet wt, 2.93 pg/g wet wt, and 2.08 pg/g wet wt, respectively. The concentrations of PCBs in snails were in the range of 78.24 to 796.96 pg/g wet wt with the highest one from Tong-Kung. A positive correlations between the concentrations of PCBs in seawater and sediment (r=0.78; p<0.01) and in oysters and snails were also observed(r=0.79; p<0.01). The bioaccumulation of PCBs from seawater to oysters was about 72 times, and the biomagnification of PCBs from oysters to snails was 10 times.

Laser ablation inductively coupled plasma mass spectrometry¡]LA- ICP-MS¡^has been applied to the determination of V¡ACr¡ACu¡AZn¡ACd¡ATl and Pb in soil and sediment samples. The powder were pressed into a pellet for LA-ICP-MS analysis,Triron X-100 was used as the modifier to enhance the ion signals.The influences of instrument operating conditions ¡]laser ablation and ICP-MS¡^and pellet preparation on the ion signals were reported. For Cr determination, the ICP-MS was operated under the DRC mode which alleviated the mass overlap interference significantly. Standard addition method and isotope dilution method were used for the quantitation work. The powder sample was spiked with suitable amount of element standard and/or enriched isotope, well mixed, dried, well mixed and then pressed into a pellet for LA-ICP-MS analysis.This method has been applied to the determination of V¡ACr¡ACu¡AZn¡ACd¡ATl and Pb in NIST SRM 2709 San Joaquin soil reference materials and NIST SRM 2711 Montana soil reference materials. The analysis results were agreed with the certified values. The precision between sample replicates was better than 10% with LA-ICP-MS method. Detection limits estimated from standard addition curves were about 260-620,3-5,0.3-1 and 9-20 ng g-1 for Cr¡ACu¡AZn¡ACd¡ATl and Pb, respectively, in different samples.

In order to understand the source, transport pathway and sink of settling particulates in the sea off northeast Taiwan, three moorings with six sediment traps (about 100 m and 300 m above bottom) were deployed on the northern slope of the Ilan ridge (T17S and T18S) and in the South Okinawa trough (T19S). The mooring deployed at T17S was lost due to a connecting ring which was rusted and broken. The duration of the mooring was 6 months (late November, 1999 to early May, 2000) with sampling intervals at 15 days each. When the moorings were recovered, seawater samples were collected for filtration near each station and a box core at T19S was also taken so that the settling particulates, suspended particulates and bottom sediments can be compared for their characteristics. The results show that higher apparent mass fluxes were observed in January, February and early April, 2000 at T18S. The apparent mass fluxes vary between 11 and 91 g/m2/d at T18S, and between 6 and 22 g/m2/d at T19S. The time-series variations of the Pb-210 activity are between 46 and 76 dpm/g at T18S, and between 79 and 122 dpm/g at T19S, the values of which are much higher than those of T18S. The temporal Po-210 variations range between 18 and 90 dpm/g at T18S, and from 65 to 193 dpm/g at T19S. The Po-210 activity and its variation are greater at T19S than at T18S. The 210Po/210Pb activity ratios are less than unity at about 0.8 at T18S, and greater than unity at about 1.3 at T19S. The total Po-210 activity in all water columns varies between 0.2 and 16 dpm/100kg while the total Pb-210 activity varies between 28 and 43 dpm/100kg. The mean total 210Po/210Pb activity ratio is about 0.3, indicating that Po-210 was easily scavenged and removed from water columns by particulate matter. The box core taken at T19S has Po-210 activity ranging from 54 to 121 dpm/g and Pb-210 activity from 51 to 90 dpm/g. The 210Po/210Pb activity ratio is greater than unity in the upper 6 cm, indicating an excess of Po-210 activity. Below 6 cm Po-210 and Pb-210 are nearly at equilibrium. The 210Po/210Pb activity ratios in the water columns observed after the first deployments were higher than those observed after the second deployments. However, the 210Po/210Pb activity ratios of the settling particulates collected from the first trap deployments were lower than those from the second trap deployments. These changes might be attributed to earthquakes which occurred mainly before the second mooring period. These earthquakes could have caused a large quantity of terrigenous particulates with higher 210Po/210Pb activity ratio to be transported out to the study area in addition to resuspended shelf and slope sediments. These settling particulates, being enriched in organic matter with higher activity ratio, could preferentially scavenge Po-210 from the water column, resulting in much higher 210Po/210Pb activity ratios.

Cold seeps are areas of high biomass in the deep-sea, the impacts of these food-rich environments upon the sediment community is unknown in the Gulf of Mexico. The structure and function of benthic communities was investigated at food-rich and food-limited sites on the northern Gulf of Mexico continental slope. Cold seeps were richer in macrofauna densities and total sediment respiration, but were poorer in biomass and taxa diversity than normal slope communities. Decreased diversity is seen at most chemosynthetic communities and suggests a competition for resources. The spatial extent of these results at seeps is unknown and may be a localized, bioenhancement effect caused by seeping fluids.

Runoff from road construction and maintenance sites is responsible for erosion and deposition of sediments in the receiving water bodies. In addition to soil particles from erosion, runoff also transports other pollutants such as rubber, toxic metals, automobile fluids, car exhausts (which settle with the rain), pesticides, fertilizers, and other debris. Compost has been used effectively as a valuable soil amendment to aid plant growth. Berms (mounds) of compost placed at the top or bottom of steep slopes can be used to slow the velocity of water and provide additional protection for receiving waters. However, a downside of the application of composted organic material is the potential degradation of runoff water quality. Overloading with nitrogen and phosphorus causes eutrophication, which reduces the suitability of waterways for beneficial uses. A field testing of the berms coupled with a laboratory analysis of the testing water will provide a basis for the impact of the compost berms on the runoff water quality. The study of the impact of compost on the runoff water quality was investigated. The objective of this study was to evaluate the performance of berms made from various materials such as dairy manure compost, yard waste compost and composted bio-solids mixed with wood chips in a ratio of 50:50 on the runoff water quality, as well as, the sediment removal efficiencies. Field tests were performed on the berms to simulate conventional rainfall runoff and the tested water was collected as time-weighted samples and analyzed in the laboratory. Several variables were investigated during this study. Results of this investigation demonstrated that the effectiveness of this application was hampered by the structural instability of the berm. A 100% failure rate was observed in the berms tested. Optimum performance was observed in yard waste compost berms, which introduced the least amount of contaminants into the water. However, some masking effect could be present due to berm failures. In fact, the actual sediment removal by the berms could not be determined. The study of compost filter berms showed some evidence of the existence of first flush effect.

Since 1970, U.S. Army Corps of Engineers, Galveston District, has been using dredged sediments from the Houston ship channel to create and restore salt marshes in Galveston Bay. Some projects have failed due to excessive sediment erosion or siltation. The research reported here applies an engineering approach to analysis of tidal creeks in natural and beneficial use marshes of Galveston Bay. The hydrodynamic numerical model, DYNLET, was used to assess circulation in marsh channels. A preliminary sediment transport model was developed to analyze erosion and deposition for the same channels. In situ flume experiments were conducted to determine the sediment erodibility in natural and constructed marshes. A natural reference marsh, Elm Grove, was studied to understand marsh hydrodynamics and model calibration. The model results show that DYNLET can largely duplicate the marsh hydrodynamics and the sediment transport model can provide preliminary indication of erosion in tidal creeks. Analysis of the preliminary channel layout of the beneficial-use marsh demonstrated that channels will have sufficient circulation and optimum velocities.

The time-series sediment traps were deployed in the northern South China Sea (NSCS) to collect settling particles to study the spatial and temporal variations of particle fluxes, particle sources and particle compositions. Each recovered sample was analyzed to determine the particle flux, major compositions (OM, Carbonate, opal and lithogenic materials) and trace metals (Al, Fe, Mn, Cd, Zn). The data were employed to elucidate the biochemical processes in controlling particle and chemical fluxes. The results show that the particle fluxes vary significantly in time and space, and were apparently related to terrestrial inputs and monsoon-effected processes. Episodic events such as typhoon and earthquakes also effected the fluxes considerably. Vertical fluxes generally decreased with depth for biogenic components (POC, carbonate, opal) but increased with depth for the lithogenic component. Most lithogenic fluxes below the surface were likely derived from lateral transport and decreased with distance away from Taiwan Island. Biogenic fluxes in surface layers were generally higher in winter than in otherseasons, which may be resulted from the elevated primary production in winter. Typhoons also enhanced biogenic fluxes in surface layers but biogenic fluxes were diluted in deep layers by strong lithogenic fluxes. Carbonate dominated the biogenic fluxes in the upper layer and may play as the major ballast in the transportation of biogenic materials through the water column. The C/N ratios of organic matter increased generally with depth implying that nitrogen was preferentially decayed over carbon through the water column. Lithogenic elements such as Al, Fe, Mn were closely correlated and increased in fluxes with depth. However, microelements associated with biogenic materials (Cd, Zn) displayed a significant decrease in content with depth, showing a rapid recycling in water columns.

Submarine canyons are common features on continental margins worldwide. They are important natural conduits for transfer of terrigenous sediments to the deep sea, and thus, preferential pathways for shelf-slope exchange. The purpose of this study is to understand the biogenic particle transport in the seasons according two sediment trap moorings deployed in the Gaoping submarine canyon. The T6KP mooring was deployed in dry season while the T7KP mooring was deployed in wet season. Two typhoons, Kalmaegi and Fung Wong, invaded Taiwan during 16-18 and 26-29 July within the deployment of T7KP. We discussed the influence of rainfall and river discharge on biogenic particle transport based on results of the two sediment traps. The foraminiferal abundance in sediment traps in comparison with plankton tows was discussed regarding the particle transport mechanism of the water column in the Gaoping submarine canyon. The biogenic particle transport was a tide-dominated situation and displayed a periodic variation in dry season. In wet season, fine grain fraction (less than 63 micro meter) was dominant in the particle size and sedimentary condition was flood-dominated. The sedimentary condition was back to the tide-dominated state approximately 15 days after Kalmaegi typhoon (16-18, July). The activities of 210Pb and 234Th in the lower trap of T7KP mooring were an order less than that in T6KP mooring, indicating particles scavenge nuclides of the water column less effectively in wet season than in dry season. The absolute abundances of foraminifera in the canyon revealed that the biogenic particle was influenced by the terrigenous input and was different between dry and wet seasons. Seasonal variations of total flux and relative abundance of living foraminifera were evident in the upper 200 m water column near the Gaoping submarine canyon. Therefore, the seasonal variations of living foraminifera might be reflected on the biogenic particle transport in different seasons in the Gaoping submarine canyon.