细化搜索
结果 771-780 的 1,908
Effects of an oil spill on benthic community production and respiration on subtropical intertidal sandflats
2013
Lee, Li-Hua | Lin, Hsing-Juh
This study determined effects of an oil spill on subtropical benthic community production and respiration by monitoring CO2 fluxes in benthic chambers on intertidal sandflats during emersion before and after an accidental spill. The oil spill decreased sediment chlorophyll a concentrations, altered benthic macrofaunal community, and affected ecological functioning by suppressing or even stopping microalgal production, increasing bacterial respiration, and causing a shift from an autotrophic system to a heterotrophic system. Effects of the oil spill on the macrofauna were more severe than on benthic microalgae, and affected sedentary infauna more than motile epifauna. Despite the oil spill’s impact on the benthic community and carbon metabolism, the affected area appeared to return to normal in about 23days. Our results suggest that the prompt response of benthic metabolism to exposure to petroleum hydrocarbons can serve as a useful indicator of the impact of an oil spill.
显示更多 [+] 显示较少 [-]Temporal and spatial distribution of red tide outbreaks in the Yangtze River Estuary and adjacent waters, China
2013
Liu, Lusan | Zhou, Juan | Zheng, Binghui | Cai, Wenqian | Lin, Kuixuan | Tang, Jingliang
Between 1972 and 2009, evidence of red tide outbreaks in the Yangtze River Estuary and adjacent waters was collected. A geographic information system (GIS) was used to analyze the temporal and spatial distribution of these red tides, and it was subsequently used to map the distribution of these events. The results show that the following findings. (1) There were three red tide-prone areas: outside the Yangtze River Estuary and the eastern coast of Sheshan, the Huaniaoshan–Shengshan–Gouqi waters, and the Zhoushan areas and eastern coast of Zhujiajian. In these areas, red tides occurred 174 total times, 25 of which were larger than 1000 km2 in areal extent. After 2000, the frequency of red tide outbreaks increased significantly. (2) During the months of May and June, the red tide occurrence in these areas was 51% and 20%, respectively. (3) Outbreaks of the dominant red tide plankton species Prorocentrum dong-haiense, Skeletonema costatum, Prorocentrum dantatum, and Noctiluca scientillan occurred 38, 35, 15, and 10 times, respectively, during the study interval.
显示更多 [+] 显示较少 [-]Analysis of temporal and spatial variability of total column ozone over West Africa using daily TOMS measurements
2013
Oluleye, Ayodeji | Okogbue, Emmanuel Chilekwu
The aim of this study was to examine the temporal and spatial total column ozone distribution in West Africa using Total Ozone Mapping spectrometer (TOMS) daily data for five years between 2001 and 2005 in fifteen locations. In this study, certain significant observations emerged: weather activity particularly the rainfall producing mechanism (dynamic of the wind systems) was responsible for about 62% ozone distribution in the region. Ozone maximum and minimum concentrations over all the stations were 305 DU and 232 DU respectively producing an average range of 73 DU (only about 27.03% of the mean value). Ozone has a seasonal distribution with minimum occurring during the dry season and maximum occurring during the wet season. A decreasing rate of about –0.6 DU/year was found for the region. Interannual ozone characteristics revealed an oscillating feature similar to Quasi – biennial Oscillation (QBO) footprints which indicated the importance of stratosphere – troposphere exchange to ozone distribution in the region. Furthermore, lag of about one or two months occurs between south (lower latitude) and north (higher latitude) monthly ozone maximums.
显示更多 [+] 显示较少 [-]Rapid method demonstration project at four New Jersey marine beaches using real time quantitative Polymerase Chain Reaction (qPCR)
2013
Ferretti, James A. | Tran, Hiep V. | Peterson, Sarah J. | Loftin, Virginia
Real time quantitative Polymerase Chain Reaction (qPCR) was used at four marine bathing beaches in New Jersey as part of a demonstration project to evaluate the potential for use of qPCR as part of a routine beach monitoring program. Split sample analyses for Enterococcus spp. using membrane filtration (MF) and qPCR were performed for 11weeks during the summer of 2011 using swimming advisories based on qPCR results. Comparison of qPCR and MF results from split samples indicated that there was an 82% overall agreement rate between the two methods. Results from the qPCR tests were available by noon the same day of sample collection and swimming advisories were posted on a dedicated website. The qPCR method can be more labor intensive and requires a higher level of training to perform, however, qPCR was able to assess beach water quality in a timelier manner compared to conventional MF techniques.
显示更多 [+] 显示较少 [-]Trace element content of seagrasses in the Leschenault Estuary, Western Australia
2013
Kilminster, Kieryn
Estuarine environments are particularly vulnerable to human impacts. In this study, trace elements in Ruppia megacarpa, Halophila ovalis, sediment and porewater were analysed to assess the potential contamination of the Leschenault Estuary, Western Australia, from a primarily agricultural drain. Sediment concentrations of Cd, Cu, Mn, and Ni and were highest nearest the drain while Al, As, Cr, Fe and Zn and were highest further from the drain. H. ovalis showed greater accumulation of Fe, Al, and As than R. megacarpa. Concentrations of Fe, Al, As, and Ni were generally higher in below-ground plant parts than above, suggesting uptake of these trace elements via the sediment-route pathway. This study suggested that the drain was a source of Cu and Mn, with these elements entering the estuary through water inflows. As and Fe, were highest furthest from the drain suggesting input of trace elements from sources other than the drain under study.
显示更多 [+] 显示较少 [-]Source characterization and spatio–temporal evolution of the metal pollution in the sediments of the Basque estuaries (Bay of Biscay)
2013
Legorburu, Irati | Rodríguez, José Germán | Borja, Angel | Menchaca, Iratxe | Solaun, Oihana | Valencia Rincón, Victoriano | Galparsoro, Ibon | Larreta, Joana
According to Water Framework Directive requirements, Member States must identify and analyze effects derived from human pressures in aquatic systems. As different kind of pressures can impact water bodies at different scales, analyses of spatio-temporal evolution of water bodies becomes essential in order to understand ecosystem responses. In this investigation, an analysis of spatio-temporal evolution of sedimentary metal pollution (Cd, Cr, Cu, Hg, Ni, Pb, Zn) in 12 Basque estuaries (Bay of Biscay) is presented. Data collected in extensive sampling surveys is the basis for the GIS-based statistical approach used. The implementation of pollution abatement measures is reflected in a long-term decontamination process, mostly evident in estuaries with highest historical sediment pollution levels. Spatial evolution is determined by either naturally occurring or human driven processes. Such spatial processes are more obviously being reflected in estuaries with lower historical sediment pollution levels.
显示更多 [+] 显示较少 [-]Direct measurement of dissolved N2 and denitrification along a subtropical river-estuary gradient, China
2013
Wu, Jiezhong | Chen, Nengwang | Hong, Huasheng | Lu, Ting | Wang, Longjian | Chen, Zhuhong
The spatial pattern and seasonal variation of denitrification were investigated during 2010–2011 in the Jiulong River Estuary (JRE) in southeast China. Dissolved N2 was directly measured by changes in the N2:Ar ratio. The results showed that excess dissolved N2 ranged from −9.9 to 76.4μmolL−1. Tidal mixing leads to a seaward decline of dissolved gaseous concentrations and water–air fluxes along the river-estuary gradient. Denitrification at freshwater sites varied between seasons, associated with changes in N input and water temperature. The denitrification process was controlled by the nitrate level at freshwater sites, and the excess dissolved N2 observed at the tidal zone largely originated from upstream water transport. Compared to other estuaries, JRE has a relative low gaseous removal efficiency (Ed=12% of [DIN]; annual N removal=24% of DIN load), a fact ascribed to strong tidal mixing, coarse-textured sediment with shallow depth before bedrock and high riverine DIN input.
显示更多 [+] 显示较少 [-]Eutrophication, risk management and sustainability. The perceptions of different stakeholders in the northern Baltic Sea
2013
Lundberg, Cecilia
The environmental condition of the Baltic Sea is not only of concern for natural scientists. The awareness of the deteriorating state of the ecosystem has become an issue of interdisciplinary interest, and the amount of organizations with the marine environment and ecosystem health on the agenda is large. To present holistic and sustainable solutions and results of the actions taken, an active cooperation between all stakeholder groups and levels are needed. How different stakeholders in the northern Baltic Sea perceive the structures and assessments of the eutrophication were analyzed by semi-structured interviews with 17 stakeholders representing authorities, scientists, NGOs and national interest organizations. The focus was the view of the governance structures, risk assessment, management and communication. There was an overall consensus that eutrophication is a serious problem. Still variations in the opinions both within and between the stakeholder groups were seen. The scientists were most divergent from the rest.
显示更多 [+] 显示较少 [-]Satellite observations and modeling of oil spill trajectories in the Bohai Sea
2013
Xu, Qing | Li, Xiaofeng | Wei, Yongliang | Tang, Zeyan | Cheng, Yongcun | Pichel, William G.
On June 4 and 17, 2011, separate oil spill accidents occurred at two oil platforms in the Bohai Sea, China. The oil spills were subsequently observed on different types of satellite images including SAR (Synthetic Aperture Radar), Chinese HJ-1-B CCD and NASA MODIS. To illustrate the fate of the oil spills, we performed two numerical simulations to simulate the trajectories of the oil spills with the GNOME (General NOAA Operational Modeling Environment) model. For the first time, we drive the GNOME with currents obtained from an operational ocean model (NCOM, Navy Coastal Ocean Model) and surface winds from operational scatterometer measurements (ASCAT, the Advanced Scatterometer). Both data sets are freely and openly available. The initial oil spill location inputs to the model are based on the detected oil spill locations from the SAR images acquired on June 11 and 14. Three oil slicks are tracked simultaneously and our results show good agreement between model simulations and subsequent satellite observations in the semi-enclosed shallow sea. Moreover, GNOME simulation shows that the number of ‘splots’, which denotes the extent of spilled oil, is a vital factor for GNOME running stability when the number is less than 500. Therefore, oil spill area information obtained from satellite sensors, especially SAR, is an important factor for setting up the initial model conditions.
显示更多 [+] 显示较少 [-]Variations of 210Po and 210Pb concentration in mussels (Mytilus galloprovincialis) from Didim and Izmir Bay (Turkish coast of Aegean Sea)
2013
Aközcan, S. | Uğur Görgün, A.
In this study, the activity concentrations of 210Po and 210Pb were determined in mussels (Mytilus galloprovincialis) collected from Didim and Izmir Bay (Turkish coast of Aegean Sea) during the period of April 2006–March 2007. The concentrations activity of 210Po were determined spectroscopically through its 5.30MeV alpha particle emission, using 209Po as an internal tracer. The 210Pb activity concentrations were determined from the ingrowth of 210Po, assuming zero initial 210Po activity. The results of 210Po and 210Pb activity concentrations were found to vary between 34±9 and 1855±98Bqkg−1 dry weight and ND (lower than limit of detection) – 64±6Bqkg−1 dry weight, respectively. 210Po/210Pb ratio ranged between 1.00 and 106.87. The highest 210Po activities were found in mussels collected from Didim.
显示更多 [+] 显示较少 [-]