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1.
The distribution and abundance of thaliaceans were studied in relation to physical and biological variables during summer and winter in the northwest continental shelf of South China Sea. Based on the topography and water mass of the surveyed region, it was divided into three subregions: region I (onshore waters of the east Leizhou Peninsula), region II (onshore waters of the east and southeast Hainan Island) and region III (offshore waters from Leizhou Peninsula to Hainan Island). During summer due to a strong southwest monsoon, a cold eddy and coastal upwelling dominated in regions I and II, respectively, whereas the onshore and offshore waters were vertically mixed during winter due to a strong northeast monsoon. A total of 18 thaliacean species (including 3 subspecies) were collected. The mean species richness was higher in summer compared to winter, with the occurrence of higher values during summer and winter at region II and region III, respectively. The average thaliacean abundance is also higher in summer than in winter, with higher values at region I in summer and no significant difference among three subregions in winter. Doliolum denticulatum and Thalia democratica were the dominant species during summer and winter. The results suggested that the seasonal and spatial distribution of thaliacean richness was considered to be the result of physical factors such as temperature and ocean current in summer and winter. Spatial distribution of thaliacean abundance was affected by chlorophyll a concentration increased by the occurrence of coastal upwelling and cold eddy in summer. Southwest and northeast monsoons are shown to play an important role in shaping the distribution of species richness and abundance of thaliaceans in the northwest continental shelf of South China Sea.  相似文献   

2.
The seasonal ecological response of microzooplankton in the southeastern Arabian Sea is presented. During the spring intermonsoon period, stratification and depletion of nitrate in the surface waters (nitracline was at 60 m depth) cause low integrated chlorophyll a (av. 19±11.3 mg m−2) and primary production (av. 164±91 mgC m−2 d−1). On the other hand, nutrient enrichment associated with coastal upwelling and river influx during the onset and peak summer monsoon resulted in high integrated chlorophyll a (av. 21±6 mg m−2 and av. 29±21 mg m−2, respectively) and primary production (av. 255±94 mgC m−2 d−1 and av. 335±278 mgC m−2 d−1, respectively). During all three periods, diazotropic cyanobacterium Trichodesmium erythraeum dominated in the nutrient depleted surface waters. A general increase in abundance of larger diatoms was evident in the surface waters of the inshore region during monsoon periods. The microzooplankton abundance was found to be significantly higher during the spring intermonsoon (av.241±113×103 ind m−2) as compared to onset of summer monsoon (av. 105±89×103 ind m−2) and peak summer monsoon (av.185±175×103 ind m−2). Microzooplankton community during the spring intermonsoon was numerically dominated by ciliates while heterotrophic dinoflagellate was the dominant ones during the monsoon periods. The high abundance of ciliates during the spring intermonsoon could be attributed to the stratified environmental condition prevailed in the study area which favors high abundance of smaller phytoplankton and cyanobacteria, the most preferred food of ciliates. On the other hand, the dominance of heterotrophic dinoflagellates during the monsoon periods could be linked to their ability to graze larger diatoms which were abundant during the monsoon periods. The overall results show low abundance of microzooplankton in the eastern Arabian Sea during the monsoon periods mainly due to a decline in ciliates abundance. This decline during the monsoon periods could be the result of (a) low abundance of smaller phytoplankton and (b) high stock of mesozooplankton predators (av. 245 ml 100 m−3).  相似文献   

3.
Tides and wind-driven mixing play a major role in promoting post-bloom productivity in subarctic shelf seas. Whether this is also true in the high Arctic remains unknown. This question is particularly relevant in a context of increasing Arctic Ocean stratification in response to global climatic change. We have used a three-dimensional ocean-sea ice-plankton ecosystem model to assess the contribution of tides and strong wind events to summer (June-August 2001) primary production in the Barents Sea. Tides are responsible for 20% (60% locally) of the post-bloom primary production above Svalbard Bank and east of the Kola Peninsula. By contrast, more than 9% of the primary production is due to winds faster than 8 m s−1 in the central Barents Sea. Locally, this contribution reaches 25%. In the marginal ice zone, both tides and wind events have only a limited effect on primary production (<2%). Removing tides or winds faster than 8 m s−1 promotes a regime more sustained by regenerated production with a f-ratio (i.e. the proportion of nitrate-based “new” primary production in the total primary production) that decreases by up to 26% (east of the Kola Peninsula) or 35% (central Barents Sea), respectively. When integrated over all Barents Sea sub-regions, tides and strong wind events account, respectively, for 6.8% (1.55 Tg C; 1 Tg C=1012 g C) and 4.1% (0.93 Tg C) of the post-bloom primary production (22.6 Tg C). To put this in context, this contribution to summer primary production is equivalent to the spring bloom integrated over the Svalbard area. Tides and winds are significant drivers of summer plankton productivity in the Barents Sea.  相似文献   

4.
Bacterioplankton abundance (BA) and biomass (BB) from the eutrophic Pearl River Estuary (PRE) to the oligotrophic northern South China Sea (NSCS) were studied in the wet season. BA was significantly higher (p < 0.05) in PRE (12.51 ± 3.52 × 108 cells L−1), than in the continental shelf neritic province (CSNP, 4.95 ± 2.21 × 108 cells L−1) and in the deep oceanic province (OP, 3.16 ± 1.56 × 108 cells L−1). Nutrient-replete PRE waters (DIN > 100 μM and PO4 > 1 μM) resulted in high chl a and BB, whereas nutrient-depleted offshore waters (DIN <5 μM and PO4 < 0.5 μM) had low biomass. Temperature (>26 °C) was not the controlling factor of BA. BB was significantly correlated with chl a biomass both in PRE and NSCS. The bacteria to phytoplankton biomass (BB/PB) ratio increased clearly along the gradient from near-shore PRE (0.15) to offshore CSNP (0.93) and deep OP (2.75), indicating the important role of small cells in the open ocean compared to estuarine and coastal zones.  相似文献   

5.
Synechococci are small (<1 μm) coccoid prokaryotes that play a significant ecological role in microbial food webs and are important contributors to carbon and nitrogen biogeochemical cycles. Under funding from NOAA and NASA, we developed a time series observatory to understand the seasonal variability of Synechococcus and other phytoplankton. Our goal is to understand the distribution and relative contribution of Synechococcus to the carbon cycle and how they relate to nutrients and temperature. Synechococcus in the southern Mid-Atlantic Bight exhibited a clear seasonal abundance pattern in both inshore and offshore waters—peaking in abundance (11×104 cells ml−1) during warm periods of summer. Synechococci were numerically important during periods of stratification when waters were warm and macronutrients were low. Using a simple algorithm to convert cellular volume to cellular carbon using image analysis, we estimated that Synechococcus cellular carbon ranged from 0.1 to 1.5 pg C per cell and was most significant compared to total particulate carbon in the summer peaking at ∼25% of the total carbon available. No direct correlations were found between Synechococcus abundance and nitrate, nitrite, ammonium, phosphate, and silicate. However, inshore Synechococcus abundance peaked at 104 cells ml−1 when nitrogen concentrations were lowest. Our results suggest that Synechococcus is adapted to warm temperatures and are capable of demonstrating rapid growth during summer when macronutrients are limiting. The ability of Synechococcus to take advantage of high summer temperatures, low nutrient concentrations and low light levels allows them to maintain a picoplankton community during periods of low detritus and nanophytoplankton is nutrient limited. Temperature-dependence is important in altering the size spectrum of the phytoplankton community and affects the carbon cycle on the Mid Atlantic Bight.  相似文献   

6.
The concentrations and sea-to-air fluxes of dissolved methane (CH4) were investigated in the North Yellow Sea during August 2006, January, April and October 2007. Dissolved CH4 concentrations showed obvious seasonal variation, with maximum values occurring in summer and lowest values occurring in winter. The saturations of dissolved CH4 in surface waters ranged from 78.7% to 1679.7% with an average of 252.4%. The estimated atmospheric CH4 fluxes using the Liss and Merlivat (LM86), and Wanninkhof formulae (W92) were (4.2±4.7), (11.6±10.3), (8.5±12.7) and (0.2±1.0), and (6.9±7.3), (14.6±22.3), (13.8±14.3) and (0.4±1.7) μmol·(m2 d)−1, respectively, for spring, summer, autumn and winter. Based on the average annual atmospheric CH4 flux and the area of the North Yellow Sea, the annual CH4 emission was estimated to be (2.4×10−2–4.2×10−2) Tg a−1, which suggests that the North Yellow Sea was a net source of atmospheric CH4.  相似文献   

7.
A three-dimensional baroclinic nonlinear numerical model is employed to investigate the summer upwelling in the northern continental shelf of the South China Sea (NCSCS) and the mechanisms of the local winds inducing the coastal upwelling, associated with the QuikSCAT wind data. First, the persistent signals of the summer upwelling are illustrated by the climatological the Advanced Very High-Resolution Radiometer (AVHRR) Sea Surface Temperature (SST) image over 1985–2006 and field observations in 2006 summer. Then, after the successful simulation of the summer upwelling in the NCSCS, four numerical experiments are conducted to explore the different effects of local winds, including the wind stress and wind stress curl, on the coastal upwelling in two typical strong summer upwelling regions of the NCSCS. The modeled results indicate that the summer upwelling is a seasonal common phenomenon during June–September in the NCSCS with the spatial extent of a basin-scale. Typical continental shelf upwelling characteristics are clearly shown in the coastal surface and subsurface water, such as low temperature, high salinity and high potential density in the east of the Hainan Island, the east of the Leizhou Peninsula and the southeast of the Zhanjiang Bay (noted as the Qiongdong-QD), and the inshore areas from the Shantou Coast to the Nanri Islands of the Fujian Coast (noted as the Yuedong-YD). The analysis of the QuikSCAT wind data and modeled upwelling index suggests that the local winds play significant roles in causing the coastal upwelling, but the alongshore wind stress and wind stress curl have different contributions to the upwelling in the Qiongdong (QDU) and the coastal upwelling in the Yuedong (YDU), respectively. Furthermore, model results from the numerical experiments show that in the YD the stable alongshore wind stress is a very important dynamic factor to induce the coastal upwelling but the wind stress curl has little contribution and even unfavorable to the YDU. However, in the QD the coastal upwelling is strongly linked to the local wind stress curl. It is also found that not only the offshore Ekman transport driven by the alongshore wind stress, the wind stress curl-induced Ekman pumping also plays a crucial effect on the QDU. Generally, the wind stress curl even has more contributions to the QDU than the alongshore wind stress.  相似文献   

8.
In order to study heterotrophic bacterial responses to upwelling in the northern South China Sea (SCS) and the influence of the Pearl River estuarine coastal plume, two cruises were conducted to investigate the distribution of bacterial abundance (BA) in September-October 2004 and 2005, along with measurements of inorganic nutrients, particulate and dissolved organic carbon (POC and DOC) in 2004. Surface BA was 10±2×108 cells l−1 near the Pearl River estuary and 6±1×108 cells l−1 in oligotrophic offshore waters of the SCS in both 2004 and 2005. In contrast, BA was 15±3×108 cells l−1 in western coastal waters during the upwelling period in 2004, and decreased to 10±2×108 cells l−1 in 2005 when upwelling was absent, indicating that upwelling exerted a significant influence on BA (p<0.05). Nutrient addition experiments were conducted and showed that phosphorus availability limited bacterial growth in coastal upwelled waters and near the Pearl River estuary, while bacteria in offshore waters were mainly C limited. The upwelled waters brought up considerable amounts of nutrients to the surface (e.g. DOC ∼70 μM, DIN ∼4 μM and PO4 ∼0.1 μM). However, P addition increased BA and bacterial production (BP) by 20±5% and 30±5%, respectively, in the upwelled water, which was higher than those near the Pearl River estuary (2±1% and 20±3%, respectively) (p<0.05). In the upwelled waters, phosphorus was low relative to nitrogen, which resulted in a high N:P ratio of 40:1 at the surface and hence potential P deficiency in bacteria. Consequently, there was a higher increase in BP in response to a PO4 addition.  相似文献   

9.
We use the hydrographic data obtained during the joint survey of the Yellow Sea by the First Institute of Oceanography, China and the Korea Ocean Research and Development Institute, Korea, to quantify the spatial structures and temporal evolution of the southern Yellow Sea Cold Water Mass (YSCWM). It is indicated that the southern YSCWM is a water mass that develops in summer and decays in fall. In winter, due to the intrusion of the Yellow Sea Warm Current (YSWC), the central area (approximately between 34°N and 35°N, 122°E and 124°E) of the Yellow Sea is mainly occupied by relatively high temperature water (T>10 °C). By contrast, from early summer to fall, under the seasonal thermocline, the central area of Yellow Sea is occupied by cold water (T<10 °C). In summer, the southern YSCWM has two cold cores. One is formed locally southeast of Shandong Peninsula, and the other one has a tongue-like feature occupying the area approximately between 34°N and 37°N, 123°E and 126°E. The bottom layer temperature anomalies from February to July in the cold tongue region, along with the trajectories of the bottom floaters, suggest that the cold water mass in the northeast region has a displacement from the north to the central area of the Yellow Sea during the summer.  相似文献   

10.
In this study are discussed new SEM-EDS analyses performed on glass shards from five cores collected in the Central Adriatic Sea and two cores recovered from the South Adriatic Sea. A total of 26 tephra layers have been characterized and compared with the geochemical features of terrestrial deposits and other tephra archives in the area (South Adriatic Sea and Lago Grande di Monticchio, Vulture volcano). The compositions are compatible with either a Campanian or a Roman provenance. The cores, located on the Central Adriatic inner and outer shelf, recorded tephra referred to explosive events described in the literature: AP3 (sub-Plinian activity of the Somma-Vesuvius, 2710 ± 60 14C years BP); Avellino eruption (Somma–Vesuvius, 3548 ± 129 14C years BP); Agnano Monte Spina (Phlegrean Fields, 4100 ± 400 years BP); Mercato eruption (Somma–Vesuvius, 8010 ± 35 14C years BP; Agnano Pomici Principali eruption (Phlegrean Fields, 10,320 ± 50 14C years BP); Neapolitan Yellow Tuff (Phlegrean Fields, 12,100 ± 170 14C years BP). Some of these layers were also observed in the South Adriatic core IN68-9 in addition to younger (AP2, sub-Plinian eruption, Somma–Vesuvius, 3225 ± 140 14C years BP), and older layers (Pomici di Base eruption, Somma–Vesuvius, 18,300 ± 150 14C years BP). Significant is the tephra record of core RF95-7 that, for the first time in the Adriatic Sea, reports the occurrence of tephra layers older than 60 ka: the well known Mediterranean tephra layers X2 (ca. 70 ka), W1 (ca. 140 ka) and V2 (Roman origin, ca. 170 ka) as well as other tephra layers attributed, on the basis of geochemistry and biostratigraphy, to explosive eruptions occurred at Vico (138 ± 2 and 151 ± 3 ka BP) and Ischia (147–140 ka BP).  相似文献   

11.
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12.
Little information is available on the levels of brominated compounds found in biota from the Korean Peninsula. In this study, Japanese common squids (Todarodes pacificus) were analyzed for 38 polybrominated diphenyl ethers, two methoxylated polybrominated diphenyl ethers and three stereoisomers of hexabromocyclododecane (α, β, and γ-HBCD) from the east and western coasts of the Korean Peninsula. Among 38 PBDEs, 10 PBDEs were detected and their total concentrations ranged from 21 to 292 ng/g lipid wt with a mean concentration of 108 ng/g lipid wt, while two MeO-BDEs and three isomers of HBCDs were detected in all samples. BDE47 showed the highest residual level, followed by BDE99, 154, 153, 28/33. Concentrations of PBDEs and MeO-BDEs were not significantly different between the both sides of the Korean Peninsula; however, HBCD concentrations were higher levels in the East/Japan Sea than the Yellow Sea, indicating that HBCD sources possibly exist in Japan.  相似文献   

13.
Stratification (throughout the year) and low solar radiation (during monsoon periods) have caused low chlorophyll a and primary production (seasonal average 13–18 mg m−2 and 242–265 mg C m−2 d−1, respectively) in the western Bay of Bengal (BoB). The microzooplankton (MZP) community of BoB was numerically dominated by heterotrophic dinoflagellates (HDS) followed by ciliates (CTS). The highest MZP abundance (average 665±226×104 m−2), biomass (average 260±145 mg C m−2) and species diversity (Shannon weaver index 2.8±0.42 for CTS and 2.6±0.35 for HDS) have occurred during the spring intermonsoon (SIM). This might be due to high abundance of smaller phytoplankton in the western BoB during SIM as a consequence of intense stratification and nitrate limitation (nitracline at 60 m depth). The strong stratification during SIM was biologically evidenced by intense blooms of Trichodesmium erythraeum and frequent Synechococcus–HDS associations. The high abundance of smaller phytoplankton favors microbial food webs where photosynthetic carbon is channeled to higher trophic levels through MZP. This causes less efficient transfer of primary organic carbon to higher trophic levels than through the traditional food web. The microbial food web dominant in the western BoB during SIM might be responsible for the lowest mesozooplankton biomass observed (average 223 mg C m−2). The long residence time of the organic carbon in the surface waters due to the active herbivorous pathways of the microbial food web could be a causative factor for the low vertical flux of biogenic carbon during SIM.  相似文献   

14.
Nutrients, chlorophyll-a (Chl-a), and environmental conditions were extensively investigated in the northern East China Sea (ECS) near Cheju Island during five research cruises from 2003 to 2007. In the eastern part of the study area, surface waters were characterized only by the Tsushima Current Water (TCW) during all five cruises. However, the western surface waters changed with season and were characterized by the Yellow Sea Cold Water (YSCW) in spring, the Changjiang Diluted Water (CDW) in summer, and the Yellow Sea Mixed Water (YSMW) in autumn. In spring and autumn, relatively high concentrations of nitrate and phosphate were observed in the surface waters in the western part of the study area, where vertical mixing brought large supplies of nutrients from deep waters. Changes in wind direction occasionally varied the inflow of the Changjiang plume in summer, clearly causing the annual variation in surface nitrate and phosphate concentrations in summer. In summer, the surface distribution of nitrate and phosphate did not coincide with that of silicate in the study area, which probably resulted from the significant drop in the Si:N ratio in the Changjiang plume since construction of the Three Gorges Dam (TGD). Despite large temporal and spatial variations in surface Chl-a concentrations, depth-integrated Chl-a concentrations exhibited little variation temporally and spatially. In the study area, surface Chl-a concentration did not well reflect the standing stocks of phytoplankton. The vertical distribution of Chl-a showed large temporal and spatial variations, and the main factor controlling the vertical distribution of Chl-a in summer was the availability of nitrate. The thermohaline front may play an important role for accumulation of phytoplankton biomass in spring and autumn.  相似文献   

15.
Dilution experiments were used to investigate the phytoplankton growth and microzooplankton grazing in the continental shelf area of northeastern South China Sea during 30 June and 7 July, 2008, occurring about a week after Typhoon Fengshen. We detected negative phytoplankton growth rates (−0.03 to −2.02 d−1) and measured grazing rates of microzooplankton on phytoplankton in size-fractionations of 20-200 μm (1.25±0.44 d−1), 3-20 μm (1.48±0.63 d−1) and <3 μm (1.02±0.42 d−1). Results showed significant correlations between phytoplankton growth and microzooplankton grazing rates, between phytoplankton and ciliate abundance, and between the dominant phytoplankton Thalassionema nitzschioides and the dominant ciliate Helicostomella longa (p<0.05). Phytoplankton decay, due to nutrient-limited conditions occurring with the fading of upwelling and spreading of freshwater plume after Typhoon Fengshen, may account for negative phytoplankton growth rates in this study. Synergism in the specific size-selective grazing of various species, including ciliates and heterotrophic dinoflagellates, may contribute to similar grazing rate on phytoplankton in different size-fractionations, at the integrated level. Interactions between phytoplankton and microzooplankton, including grazing selectivity, top-down and bottom-up control between phytoplankton and microzooplankton may contribute to these findings. Our results indicate that under conditions of negative phytoplankton growth microzooplankton grazing may reduce energy loss from the epipelagic waters by retrieving energy from the decaying phytoplankton community.  相似文献   

16.
The southern Yellow Sea (SYS), located to the north of the East China Sea (ECS), was considered part of the ECS when Tsunogai et al. (1999) proposed the “continental shelf pump” (CSP) hypothesis. However, the original CSP carbon dioxide (CO2) uptake flux (2.9 mol C m−2 yr−1) appears to have been overestimated, primarily due to the differences between the SYS and the ECS in terms of their CO2 system. In this paper, we estimated air-sea CO2 fluxes in the SYS using the surface water partial pressure of CO2 (pCO2) measured in winter, spring, and summer, as well as that estimated in fall via the relationship of pCO2 with salinity, temperature, and chlorophyll a. The results indicate that overall, the entire investigated area was a net source of atmospheric CO2 during summer, winter, and fall, whereas it was a net sink during spring. Spatially, the nearshore area was almost a permanent CO2 source, while the central SYS shifted from being a CO2 sink in spring to a source in the other seasons of the year. Overall, the SYS is a net source of atmospheric CO2 on an annual scale, releasing ∼7.38 Tg C (1 Tg=1012 g) to the atmosphere annually. Thus, the updated CO2 uptake flux in the combined SYS and ECS is reduced to ∼0.86 mol C m−2 yr−1. If this value is extrapolated globally following Tsunogai et al. (1999), the global continental shelf would be a sink of ∼0.29 Pg C yr−1, instead of 1 Pg C yr−1 (1 Pg=1015 g).The SYS as a net annual source of atmospheric CO2 is in sharp contrast to most mid- and high-latitude continental shelves, which are CO2 sinks. We argue that unlike the ECS and the North Sea where carbon on the shelf could be exported to the open ocean, the SYS lacks the physical conditions required by the CSP to transport carbon off the shelf effectively. The global validity of the CSP theory is thus questionable.  相似文献   

17.
Cruises to Bering Strait and the Chukchi Sea in US waters from late June in 2002 to early September in 2004 and the Russian–American Long-term Census of the Arctic (RUSALCA) research cruise in 2004 covered all major water masses and contributed to a better understanding of the regional physics, nutrient dynamics, and biological systems. The integrated concentration of the high nitrate pool in the central Chukchi Sea was greater in this study than in previous studies, although the highest nitrate concentration (∼22 μM) in the Anadyr Water mass passing through the western side of Bering Strait was consistent with prior observations. The chlorophyll-a concentrations near the western side of the Diomede Islands ranged from 200 to 400 mg chl-a m−2 and the range in the central Chukchi Sea was 200–500 mg chl-a m−2 for the 2002–2004 Alpha Helix (HX) cruises. Chlorophyll-a concentrations for the 2004 RUSALCA cruise were lower than those from previous studies. The mean annual primary production of phytoplankton from this study, using a 13C–15N dual-isotope technique, was 55 g C m−2 for the whole Chukchi Sea and 145 g C m−2 for the plume of Anadyr–Bering Shelf Water in the central Chukchi Sea. In contrast, the averages of annual total nitrogen production were 13.9 g N m−2 (S.D.=±16.2 g N m−2) and 33.8 g N m−2 (S.D.=±14.1 g N m−2) for the Chukchi Sea and the plume, respectively. These carbon and nitrogen production rates of phytoplankton were consistently two-or three-fold lower than those from previous studies. We suggest that the lower rates in this study, and consequently more unused nitrate in the water column, were caused by lower phytoplankton biomass in the Bering Strait and the Chukchi Sea. However, we do not know if the lower rate of production from this study is a general decreasing trend or simply temporal variations in the Chukchi Sea, since temporal and geographical variations are substantially large and presently unpredictable.  相似文献   

18.
Lead concentrations and isotopes in aerosols from Xiamen, China   总被引：1，自引：0，他引：1  
To investigate the magnitude and origin of lead (Pb) pollution in the atmosphere of Xiamen, China, 40 aerosol samples were collected from the coast of Xiamen from January to December 2003. All these samples were measured for Pb isotopic compositions (208Pb/206Pb = 2.10897 ± 0.00297, 207Pb/206Pb = 0.85767 ± 0.00159, n = 40) using a Multi-collector-Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS). Thirty-five out of forty samples were also measured for Pb concentrations (79.1 ± 38.3 ng/m3, n = 35) by Atomic Absorption Spectroscopy (AAS). The results indicate that the Pb concentrations display significant seasonal variations while Pb isotopic ratios remain relatively constant. The Pb concentrations were high in January and February, abruptly decreased in March, remained relatively constant (but low) from April to August, and then gradually increased from September to December. This corresponds to the rainless climate in winter and rain scavenging in summer. The higher Pb concentration of Xiamen aerosols in winter and spring may be also caused by long-range transferred anthropogenic Pb during the northeastern monsoon seasons. Although the use of leaded gasoline in Xiamen was banned in 2000, our new data indicate that the Pb annual concentrations of aerosols in Xiamen increased about 12% when compared to the data measured between 1991 and 1993. Thus, Pb pollution in the atmosphere of Xiamen has not receded even after the phase-out of leaded gasoline. Our results further confirm the previous studies’ conclusion that the primary source of atmospheric Pb in China, especially in South China, is the vast combustion of lead-containing coal, not leaded gasoline.  相似文献   

19.
The glassfish, Ambassis jacksoniensis, is a key, mid-level species in an estuarine food web on the east coast of Australia. Estuaries are subject to contamination from urban and industrial activities. The biokinetics of Cd, Se and Zn accumulation by glassfish from water and food were assessed using radioisotopes. Metal uptake from water was not regulated over the range of water metal concentrations examined. Metal uptake from food was assessed using brine shrimp (Artemia sp.) fed radio-labelled algae. The assimilation efficiency from food was 9.5 ± 2.5%, 23 ± 2.2% and 4.6 ± 0.6% for Cd, Se and Zn, respectively. The potential for biomagnification was low for all metals. Food is the main metal uptake pathway for glassfish, with 97%, 99% and 98% of the uptake of Cd, Se and Zn, respectively, estimated to be from food.  相似文献   

20.
Total mercury was analyzed as a function of body length, season, and diet in four commercially and recreationally important marine fish, bluefish (Pomatomus saltatrix), goosefish (Lophius americanus), silver hake (Merluccius bilinearis), and summer flounder (Paralichthys dentatus), collected from continental shelf waters of the northwest Atlantic Ocean. Mercury levels in the dorsal muscle tissue of 115 individuals ranged from 0.006 to 1.217 μg/g (wet weight) and varied significantly among species. The relationship between predator length and mercury concentration was linear for bluefish and summer flounder, while mercury levels increased with size at an exponential rate for silver hake and goosefish. Mercury burdens were the highest overall in bluefish, but increased with size at the greatest rate in silver hake. Seasonal differences were detected for bluefish and goosefish with mercury levels peaking during summer and spring, respectively. Prey mercury burdens and predator foraging habits are discussed as the primary factors influencing mercury accumulation.  相似文献   

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