Уточнить поиск
Результаты 881-890 из 2,512
Deepwater marine litter densities and composition from submersible video-transects around the ABC-islands, Dutch Caribbean Полный текст
2014
Debrot, A.O. | Vinke, E. | van der Wende, G. | Hylkema, A. | Reed, J.K.
Baseline data on anthropogenic seafloor debris contamination in the year 2000 is provided for 24 submersible video transects at depths of 80–900m, off the Dutch ABC-islands (Aruba, Bonaire, Curaçao), in the southeastern Caribbean Sea. In total, 202 objects were documented from a combined 21,184m of transect, ranging from sandy lower island-slope to rocky upper island-slope habitat. Debris densities differed significantly with depth. Highest debris accumulation (0.459 items 100m−2 or 4590 items per km2) occurred at depths of 300–600m on more shallow-sloping (20–30°) sand and silt bottoms. The overall average debris density was 0.27 objects per 100m2 (or 2700 items per km2), which is an order of magnitude higher than most other deepwater debris studies. What we describe may be representative for other small, populated, steep volcanic Caribbean islands. Food and beverage-related items were the single largest usage category identified (44% of objects; mostly glass beverage bottles).
Показать больше [+] Меньше [-]All aboard! A biological survey of ballast water onboard vessels spanning the North Atlantic Ocean Полный текст
2014
Steichen, Jamie L. | Schulze, Anja | Brinkmeyer, Robin | Quigg, Antonietta
Global movement of nonindigenous species, within ballast water tanks across natural barriers, threatens coastal and estuarine ecosystem biodiversity. In 2012, the Port of Houston ranked 10th largest in the world and 2nd in the US (waterborne tonnage). Ballast water was collected from 13 vessels to genetically examine the eukaryotic microorganism diversity being discharged into the Port of Houston, Texas (USA). Vessels took ballast water onboard in North Atlantic Ocean between the Port of Malabo, Africa and Port of New Orleans, Louisiana, (USA). Twenty genera of Protists, Fungi and Animalia were identified from at least 10 phyla. Dinoflagellates were the most diverse and dominant identified (Alexandrium, Exuviaella, Gyrodinium, Heterocapsa, Karlodinium, Pfiesteria and Scrippsiella). We are reporting the first detection of Picobiliphytes, Apusozoa (Amastigomonas) and Sarcinomyces within ballast water. This study supports that global commerce by shipping contributes to long-distance transportation of eukaryotic microorganisms, increasing propagule pressure and invasion supply on ecosystems.
Показать больше [+] Меньше [-]Could ocean currents be responsible for the west to east spread of aquatic invasive species in Maritime Canadian waters? Полный текст
2014
Brickman, D.
The circulation in the shelf seas of Maritime Canada is predominantly in the northeast–southwest direction. Despite the mean northeast–southwest flow, a number of AIS invasions have been observed to proceed in the opposite direction – from the Gulf of Maine, around Nova Scotia, and into the southern Gulf of St. Lawrence. Flow fields from a numerical circulation model are used to investigate whether these invasions could be due to drift in ocean currents. Particle tracking experiments are performed and probability density functions (PDFs) derived that describe the probability of drifting a given upstream distance in a given drift time. Analysis of these PDFs revealed that for invasions that took 20–40y to occur, propagule drift in ocean currents could be responsible for the upstream spread, while this was not the case for short timescale invasions (<10y). Rafting could be responsible for both short and long timescale invasions.
Показать больше [+] Меньше [-]Sedimentary records of hydroxylated and methoxylated polybrominated diphenyl ethers in the southern Yellow Sea Полный текст
2014
Fan, Ying | Lan, Jing | Zhao, Zongshan | Zhao, Meixun
Although hydroxylated (OH-) and methoxylated (MeO-) polybrominated diphenyl ethers (PBDEs) have caused much concern in recent years, few reports had discussed on their input history. In this study, we measured the contents of nine MeO-BDEs, ten OH-BDEs, and total organic carbon (TOC) of two sediment cores from the southern Yellow Sea. 6-MeO-BDE-47, 2′-MeO-BDE-68, 6-OH-BDE-47, and 2′-OH-BDE-68 were the predominant congeners in HH12, while only 2′-OH-BDE-68 and 6-OH-BDE-47 were frequently detected in core HH11. The records showed that OH-/MeO-BDEs in both cores had increased rapidly since the 1950s. Their existence was detected at the bottom layers (∼1800s) prior to the production of PBDEs (1960s), thus OH-/MeO-BDEs originate from natural origins rather than artificial PBDEs. Comparisons between TOC and OH-/MeO-BDEs indicated that TOC is a potential factor affecting the accumulation of OH-/MeO-BDEs in marine environments. Similar trends and significant correlations between OH-BDEs and MeO-BDEs suggest their common origins or interconversion.
Показать больше [+] Меньше [-]Development and application of an oil spill model with wave–current interactions in coastal areas Полный текст
2014
Guo, WeiJun | Hao, Yanni | Zhang, Li | Xu, Tiaojian | Ren, Xiaozhong | Cao, Feng | Wang, Shoudong
The present paper focuses on developing a numerical oil spill model that incorporates the full three-dimensional wave–current interactions for a better representation of the spilled oil transport mechanics in complicated coastal environments. The incorporation of surface wave effects is not only imposing a traditional drag coefficient formulation at the free surface, but also the 3D momentum equations are adjusted to include the impact of the vertically dependent radiation stresses on the currents. Based on the current data from SELFE and wave data from SWAN, the oil spill model utilizes oil particle method to predict the trajectory of individual droplets and the oil concentration. Compared with the observations in Dalian New Port oil spill event, the developed model taking into account wave–current coupling administers to giving better conformity than the one without. The comparisons demonstrates that 3D radiation stress impacts the spill dynamics drastically near the sea surface and along the coastline, while having less impact in deeper water.
Показать больше [+] Меньше [-]Uncharted sources of particle bound polycyclic aromatic hydrocarbons from South Asia: Religious/ritual burning practices Полный текст
2014
Dewangan, Shippi | Pervez, Shamsh | Chakrabarty, Rajan | Zielinska, Barbara
This paper deals with the real–world emissions of particle bound polycyclic aromatic hydrocarbons (PAHs) emitted from different religious and ritual burning practices in India. The emission factors (EFs) of various PAHs were characterized over integrated stages of burning practices including pyrolysis, flaming and smoldering. Sampling was carried out in selected five different types of religious and ritual places: Hindu Temples (HT), Muslim Holy shrines (MG), Buddhist Temples (BT), Hindu Marriage Places (MP) and Cremation Centers (Hindu Funeral Pyre) (CC); where burning practices mostly include natural and synthetic biomaterials in different proportions. Seventy PAHs were analyzed and grouped in light PAHs (LPAHs=25) and heavy PAHs (HPAHs=45) according to number of benzene rings present and respective molecular weights. The average EF of total PAHs (TPAHs) from MP, MG, BT, HT and CC is estimated as 77.04±5.39, 99.09±6.02, 90.35±6.76, 22.78±1.57, and 77.15±6.16mg kg−1, respectively. Country level emission budget of particulate bound TPAHs from religious and ritual burning practices has also been evaluated to 0.47Gg yr−1; contributed ~23% of the 2.07Gg yr−1 – Indian emission budget of PAHs from unknown sources reported earlier.
Показать больше [+] Меньше [-]Levels and neurodevelopmental effects of polycyclic aromatic hydrocarbons in settled house dust of urban dwellings on preschool–aged children in Nanjing, China Полный текст
2014
Wang, Bing–Ling | Pang, Shu–Tao | Zhang, Xiao–Ling | Li, Xi–Ling | Sun, Yong–Gang | Lu, Xiao–Mei | Zhang, Qi | Zhang, Zheng–Dong
This study investigated levels and possible determinants of polycyclic aromatic hydrocarbons (PAHs) in settled house dust of urban dwellings with preschool–aged children in Nanjing, China. The possible neurodevelopmental effects of house–dust PAHs on the children were also investigated. Settled house dust was collected from 203 urban houses. Fifteen PAHs were measured using an HPLC with a fluorescence detector and wavelength programming. The Child Behavior Checklist and the Gesell Development Inventory were used to evaluate the overall development of the children. PAHs were detected in settled house dust of >90% of houses, where high molecular weight PAHs predominated. Most PAHs with two or three rings were found at significantly higher levels in indoor compared with outdoor dust. PAH isomeric ratios showed that PAHs with four or more rings might be derived from outdoor coal burning sources. Naphthalene was found at lower concentrations in houses with more hours of natural ventilation, while pyrene, chrysene (Chr) and benzo[k]fluoranthene (BkF) were present at higher concentrations in these houses. A higher floor level correlated with lower levels of PAHs, especially those with four or more rings, while older houses had higher PAH levels. Benzo[a]pyrene (BaP) and indeno[1,2,3–cd]pyrene levels were positively associated with most behavioral problem scores. Higher BaP and benzo[g,h,i]perylene levels showed lower Gesell language development quotient (DQs), and higher Chr and BkF were associated with lower Gesell social skill DQs. In conclusion, 15 PAHs are ubiquitous in urban settled house dust, where outdoor coal burning and indoor cooking oil fumes are the two main sources of PAHs in Nanjing, China. Natural ventilation, floor level and residence age potentially influence house dust PAH levels. The potential adverse effect of postnatal exposure to PAHs on the behavior and neurodevelopment of preschool–aged children requires follow up in larger studies.
Показать больше [+] Меньше [-]Revisiting methods for the determination of bioavailable metals in coastal sediments Полный текст
2014
Peña-Icart, Mirella | Mendiguchía, Carolina | Villanueva-Tagle, Margarita E. | Pomares-Alfonso, Mario S. | Moreno, Carlos
A simple methodology for the determination of bioavailability of fourteen metals in coastal sediments has been developed by simulating the conditions of digestive process of marine fishes. With this aim, a representative sediment composite sample was treated with hydrochloric acid solutions at different pH values, temperatures and contact times, in the presence and absence of Pepsin and Trypsin. The addition of Pepsin and Trypsin did not affect the extraction of most elements. As a result of the present study, the digestion with a hydrochloric acid solution at pH 1, 40°C and 12h is proposed. Adjustments of the temperature and time reaction could be made according to the specific ecosystem under study. The amount of metal extracted by other methods based on acetic acid was lower than that extracted by HCl treatment proposed.
Показать больше [+] Меньше [-]Assessment of ecological quality of coastal lagoons with a combination of phytobenthic and water quality indices Полный текст
2014
Christia, Chrysoula | Giordani, Gianmarco | Papastergiadou, Eva
Coastal lagoons are ecotones between continents and the sea. Coastal lagoons of Western Greece, subjected to different human pressures, were classified into four different types based on their hydromorphological characteristics and monitored over a three year period for their biotic and abiotic features. Six ecological indices based on water quality parameters (TSI-Chl-a, TSI-TP, TRIX), benthic macrophytes (E-MaQI, EEI-c) and an integrated index TWQI, were applied to assess the ecological status of studied lagoons under real conditions. The trophic status ranged from oligotrophic to hypertrophic according to the index applied. The ecological quality of transitional water ecosystems can be better assessed by using indices based on benthic macrophytes as changes in abundance and diversity of sensitive and tolerant species are the first evidence of incoming eutrophication. The multi-parametric index TWQI can be considered appropriate for the ecological assessment of these ecosystems due to its robustness and the simple application procedure.
Показать больше [+] Меньше [-]Compositions and constituents of freshwater dissolved organic matter isolated by reverse osmosis Полный текст
2014
Zhang, Yulong | Huang, Wen | Ran, Yong | Mao, Jingdong
Dissolved organic matter (DOM) from riverine and lacustrine water was isolated using a reverse osmosis (RO) system. Solid-state 13C nuclear magnetic resonance (13C NMR) was used to quantitatively evaluate the compositions and constituents of DOM, which are compared with previous investigations on marine DOM. Results indicated that concentration factor (CF) was a key metric controlling yield and sorption of DOM on the RO system. The sorption was likely non-selective, based on the 13C NMR and δ13C analyses. Carbohydrates and lipids accounted for 25.0–41.5% and 30.2–46.3% of the identifiable DOM, followed by proteins (18.2–19.8%) and lignin (7.17–12.8%). The freshwater DOM contained much higher alkyl and aromatic C but lower alkoxyl and carboxyl C than marine DOM. The structural difference was not completely accounted for by using structure of high molecular weight (HMW) DOM, suggesting a size change involved in transformations of DOM during the transport from rivers to oceans.
Показать больше [+] Меньше [-]