Chin-Chang Hung

Surface distributions of carbon chemistry parameters in the East China Sea in summer 2007

[1] Comprehensive carbon chemistry data including total alkalinity (TA), dissolved inorganic carbon (DIC), pH, fugacity of CO 2 and other pertinent data (i.e., temperature, salinity, and levels of nitrate and chlorophyll a) were measured in surface waters of the East China Sea (ECS) shelf in July 2007. The results show that spatial variations in these parameters closely correspond to the distributions of various water types. The Changjiang Diluted Water (CDW) and Yellow Sea Water (YSW) areas are the two major sinks of atmospheric CO 2 ; the Coastal Upwelling Water (CUW) area is the most important CO 2 source, whereas the Kuroshio Water and Taiwan Current Warm Water areas are weak sources. The entire ECS acted as a sink for atmospheric CO 2 , with a flux of -2.4 to - 4.3 mmol C m -2 d -1 during the study period. Identification of the CUW source area suggests that previous studies might have overestimated CO 2 uptake by the ECS in summer. Our results further suggest that high biological production might be responsible for the strong sink in the CDW area but that high input of TA from the Huanghe River, which led to an elevated TA/DIC ratio, could have resulted in formation of a significant CO 2 sink in the YSW area. The present data set represents the most comprehensive CO 2 survey in the ECS to date and can thus be used as a baseline for monitoring future changes in the CO 2 system arising from the construction of the Three Gorges Dam in the middle stretch of the Changjiang River.

Gravity Flows Associated with Flood Events and Carbon Burial: Taiwan as Instructional Source Area

Taiwans unique setting allows it to release disproportionately large quantities of fluvial sediment into diverse dispersal systems around the island. Earthquakes, lithology, topography, cyclone-induced rainfall, and human disturbance play major roles in the catchment dynamics. Deep landslides dominate the sediment-removal process on land, giving fluvial sediment distinct geochemical signals. Extreme conditions in river runoff, sediment load, nearshore waves and currents, and the formation of gravity flows during typhoon events can be observed within short distances. Segregation of fresh biomass and clastic sediment occurs during the marine transport process, yet turbidity currents in the Gaoping Submarine Canyon carry woody debris. Strong currents in the slope and back-arc basin of the Okinawa Trough disperse fine-grained sediments rapidly and widely. Temporal deposition and remobilization may occur when the shallow Taiwan Strait acts as a receptacle. Taiwan can therefore serve as a demonstration of the episodic aspect of the source-to-sink pathway to both the coastal and deep-ocean environments.

Relationships between persistent organic pollutants and carbonaceous materials in aquatic sediments of Taiwan

Recent studies have shown that many persistent organic pollutants (POPs, e.g., polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and various pesticides), are strongly associated with carbonaceous materials (including organic carbon (OC) and black carbon (BC)). We hypothesize that carbonaceous materials can be used as a first-order pollution index, to indicate areas where POP pollution may require further investigation. We tested our hypothesis and found that strong, positive correlations between BC and OC contents versus the concentrations of PCBs (and PAHs) existed in estuarine sediments of the Danshui River in 2005 and 2008. Thus, our preliminary results demonstrate that POC and BC are potential indicators of the POP pollution potential in fluvial sediments of the Danshui River in Taiwan. This innovative approach can provide a simple, relatively inexpensive and expedient means to monitor concentrations of POPs in polluted aquatic sediments of Taiwan, and/or those having a legacy of POP inputs.

Polycyclic aromatic hydrocarbons in surface sediments of the East China Sea and their relationship with carbonaceous materials.

This study measured concentrations of polycyclic aromatic hydrocarbons (PAHs) in surface sediments in the East China Sea (ECS) to investigate possible sources and fate of PAHs. Total concentration of PAHs in the sediments of the ECS ranged from 22 to 244 ng g(-1), with the highest levels in the coastal area and outer shelf. The observed PAH results showed elevated levels in both inner and outer shelf areas, a finding that is different from predictions by an ocean circulation model, suggesting that terrestrial sources are important for PAH contaminations in the ECS, while sediment resuspension, tidal changes and lateral transport may be important in affecting the distribution of PAHs in the outer shelf. The distribution of PAHs in the surface sediments of the ECS is similar to the distribution of carbonaceous materials (e.g., particulate organic carbon and black carbon), suggesting that carbonaceous materials may strongly affect the distribution of PAHs.

Nutrient supply in the Southern East China Sea after Typhoon Morakot

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Occurrence of azaarenes in sediments of the Danshuei River, Taiwan: the use of azaarenes as indicator of anthropogenic source to the estuarine system.

Azaarenes belong to the newly identified classes of anthropogenic pollutants. To our knowledge, this study presents the first result of pollution history of azaarenes and their controlling factors in estuary. To understand the transport mechanisms, surface sediment samples were collected from 18 sites of the Danshuei River during the summer and the winter of 2005. The highest concentrations of azaarene, 21.9 ng g−1 for 2‐ring, 9.89 ng g−1 for 3‐ring, and 9.17 ng g−1 for 4‐ring, were observed in midstream surface sediments near the Shi–Zi–Tou waste water pumping station. Therefore, this waste water pumping station not only provides a good sediment accumulation environment but also discharges small particle size sediments, which contain mass amounts of azaarenes into the Danshuei River. This research also finds highly significant covariations among 3‐ring and 4‐ring azaarenes, which suggests similar source strengths and transport mechanisms for these compounds. Additionally, core samples were collected from two sites of the Danshuei River and analyzed to determine the pollution history. Values found in the core sediments correspond to pollution events in recent history. Contaminant inputs via in situ burning of dumping field and wastewater discharge for the periods of 1975–1985 and 2004–2005, respectively, were two major sources of azaarenes to the Danshuei River.

Total and organic mercury concentrations in the muscles of Pacific albacore (Thunnus alalunga) and bigeye tuna (Thunnus obesus).

Muscles of 115 North Pacific albacore (ALB, Thunnus alalunga) and 75 Pacific bigeye tuna (BET, Thunnus obesus), collected from 2001 to 2006, were analyzed. No ALB, but 13 large BET had organic mercury (OH g) concentrations exceeding 1 μg g(-1) wet weight. For both ALB and BET, total mercury (THg) and OH g concentrations were significantly and positively correlated with fork length (FL) and body weight. The muscle Hg bioaccumulation rates of BET were higher than those of ALB, particularly in the adult fish. Moreover, the lines had crossover points among the two species that imply the young BET (FL<110 cm) contains lower muscle Hg concentrations than ALB of the same size. The suggested weekly dietary intake of ALB and small-BET meats is 340 g, and of BET meat it is 150 g for a 60-kg person based on the provisional tolerable weekly intake (PTWI) of methylmercury set by the WHO.

Reply to comment by Jinchun Yuan et al. on “Reduction of primary production and changing of nutrient ratio in the East China Sea: Effect of the Three Gorges Dam?”

[1] A brief discussion is presented here in response to Yuan et al.’s [2007] comment on our paper entitled ‘‘Reduction of primary production and changing of nutrient ratio in the East China Sea: Effect of the Three-Gorges Dam?’’ [Gong et al., 2006]. [2] First, we would like to point out that our research provides sufficient seasonal variations using accurate chlorophyll a (Chl a) data in the traditionally nutrient-rich (TNR) region of the East China Sea, as determined in several previous high-frequency sea-based investigations [Gong et al., 1996, 2003, 2006]. In contrast, Yuan et al. [2007] used questionable Chl a data (derived from the SeaWiFS OC4 algorithm: see second point) to study the inter-annual variations in Chl a in the entire East China Sea. This is clearly apparent in Figure 1 which illustrates the comparison between our average sea-based Chl a concentrations in the entire East China Sea (solid brown stars in Figure 1) and the SeaWiFS-derived Chl a data reported in Figure 2 of Yuan et al.’s comment. The results show that the SeaWiFS-derived Chl a data were substantially higher than our sea-based Chl a data. There can be no question that Yuan et al.’s [2007] data were invalid. [3] Second, we further question the accuracy of the SeaWiFS-derived Chl a data for the East China Sea which were used in Yuan et al.’s [2007] comments. Our reasons are as follows: [4] (1) It is widely believed that the standard SeaWiFSOC4 chlorophyll algorithm is only valid for ‘‘Case 1 waters’’ [O’Reilly et al., 1998; Carder et al., 1999]. But this type of global algorithm is flawed when it comes to ‘‘Case 2 waters’’ [Mueller and Austin, 1995; International Ocean-Colour Coordinating Group, 2000; Liew et al., 2001; Gong, 2004]. The key reason for the algorithmic failure in the case of ‘‘Case 2 waters’’ is that there is interference from the strong absorption of colored dissolved organic matter (CDOM) in the blue band that overlaps with phytoplankton chlorophyll absorption. When the absorption coefficient due to colored dissolved organic matter at 380 nm (acdom(l = 380 nm)) is greater than 0.1 m 1 [Mueller and Austin, 1995], the ocean waters are regarded as ‘‘Case 2 waters’’, and the use of the global satellite ocean-color OC4 algorithm is inappropriate. But unfortunately, Yuan et al. [2007] used the OC4 algorithm to process their Chl a data for the East China Sea, a region with ‘‘Case 2 waters.’’ [5] (2) O’Reilly et al. [1998] collected a large data set including coincident in-situ chlorophyll and remote sensing information to evaluate the performance of a wide variety of ocean color chlorophyll algorithms for SeaWiFS data. One of their conclusions is that, while the performance of the OC4 was superior to that of the OC2, it is not as suitable as the initial operational algorithm for SeaWiFS-derived Chl a data because its use requires accurate atmospheric correction and on-orbit calibrations in four bands (instead of two). They explain that this can only be assessed after the collection of sufficient data to validate and fine-tune sensor calibrations. It is currently widely known that atmospheric pollution in the shelf area of the East China Sea is very serious because of rapid industrial development in the coastal cities of China. Additionally, the high frequency of Asian dust storms has been observed in the East China Sea. As a result, the SeaWiFS-derived Chl a data are not likely very accurate without proper atmospheric correction. A second conclusion by O’Reilly et al. [1998] is that ‘‘Case 2 waters’’ present additional complications and challenges as their properties change depending on whether they are dominated by CDOM, nochlorophyllous particles, or a variable mix of both [Carder et al., 1989]. In short, specific algorithms or different parameterizations are required to process data from different regions. [6] (3) Gong [2004] presented CDOM data for four seasons from surface waters of the entire East China Sea. These data showed that the values of acdom(l = 325 nm) were higher than 0.2 m 1 (equivalent to acdom(l = 380 nm) = 0.1 m ) for most of the shelf waters year-round (Figure S1 of the auxiliary material). Figure S1 clearly shows that the values of acdom(l = 380 nm) in the TNR region are always higher than 0.1 m . These results support the optical classification of the TNR region as ‘‘Case 2 waters.’’ Additionally, a significant overestimation of the SeaWiFS-derived Chl a concentrations (2.3 mg m ) at a station located about 200 km east off the Changjiang River mouth (see star-symbol in Figure S1a) was found in

Enhanced Particulate Organic Carbon Export at Eddy Edges in the Oligotrophic Western North Pacific Ocean

Mesoscale eddies in the subtropical oligotrophic ocean are ubiquitous and play an important role in nutrient supply and oceanic primary production. However, it is still unclear whether these mesoscale eddies can efficiently transfer CO2 from the atmosphere to deep waters via biological pump because of the sampling difficulty due to their transient nature. In 2007, particulate organic carbon (POC) fluxes, measured below the euphotic zone at the edge of warm eddy were 136–194 mg-C m−2 d−1 which was greatly elevated over that (POC flux = 26–35 mg-C m−2 d−1) determined in the nutrient-depleted oligotrophic waters in the Western North Pacific (WNP). In 2010, higher POC fluxes (83–115 mg-C m−2 d−1) were also observed at the boundary of mesoscale eddies in the WNP. The enhanced POC flux at the edge of eddies was mainly attributed to both large denuded diatom frustules and zooplankton fecal pellets based on scanning electron microscopy (SEM) examination. The result suggests that mesoscale eddies in the oligotrophic waters in the subtropical WNP can efficiently increase the oceanic carbon export flux and the eddy edge is a crucial conduit in carbon sequestration to deep waters.

Observations of a freshwater pulse induced by Typhoon Morakot off the northern coast of Taiwan in August 2009

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