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Результаты 1111-1120 из 4,241
Chemical analysis of particulate products of aged 1,3,5-trimethylbenzene secondary organic aerosol in the presence of ammonia
2017
Huang, Mingqiang | Xu, Jun | Cai, Shunyou | Liu, Xingqiang | Hu, Changjin | Gu, Xuejun | Zhao, Weixiong | Fang, Li | Zhang, Weijun
Ammonia (NH3) gas-aging of secondary organic aerosol (SOA) results in the formation of organonitrogen compound is an important class of brown carbon. The particulate products of aged 1,3,5-trimethylbenzene (135-TMB) SOA in the presence of NH3 were measured by UV–Vis spectrophotometer, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), and aerosol laser time-of-flight mass spectrometer (ALTOFMS) in present study. Experimental results indicated that NH3 has significant promotion effect on 135-TMB SOA formation. Organic ammonium salts, such as ammonium methyl glyoxylate, ammonium 3,5-dimethylbenzoate, which are formed from NH3 reactions with gaseous organic acids were detected as the principal particulate products of NH3-aged 135-TMB SOA. 4-methyl-imidazole-2-acetaldehyde, 4-methyl- 1H-imidazole and other imidazole products via the heterogeneous reactions between NH3 and dialdehydes of 135-TMB SOA were newly measured. The formation of imidazole products suggests that some ambient particles contained organonitrogen compounds may be come from this mechanism. The results of this study may provide valuable information for discussing SOA aging mechanisms and new route for NH3 deposition.
Показать больше [+] Меньше [-]Effects of pH on the growth and NH4-N uptake of Skeletonema costatum and Nitzschia closterium
2017
Gu, Xingyan | Li, Keqiang | Pang, Kai | Ma, Yunpeng | Wang, Xiulin
Ocean acidification (OA) and eutrophication intensifies in coastal sea under anthropogenic impact. OA coupled with the NH4-N source effect in coastal water is likely to affect the planktonic ecosystem. In this work, Skeletonema costatum and Nitzschia closterium were chosen as typical species of diatom in Chinese coastal ecosystems to test the potential effect of OA and NH4-N. Results showed that the growth and NH4-N uptake of S. costatum and N. closterium were significantly inhibited by pH decline. The maximum uptake rate is higher than the maximum growth rate, implying that NH4-N was assimilated faster for S. costatum and N. closterium with decreasing pH. Therefore, the inhibition rate of the growth of the two diatoms by the coupling effect of OA and eutrophication (pH7.45) is higher that than in the coastal sea by the end of the 21st century (pH7.71).
Показать больше [+] Меньше [-]Plastic ingestion in oceanic-stage loggerhead sea turtles (Caretta caretta) off the North Atlantic subtropical gyre
2017
Pham, Christopher K. | Rodríguez, Yasmina | Dauphin, Axelle | Carriço, Rita | Frias, João P.G.L. | Vandeperre, Frederic | Otero, Vanessa | Santos, Marco R. | Martins, Helen R. | Bolten, Alan B. | Bjorndal, Karen A.
Juvenile oceanic-stage sea turtles are particularly vulnerable to the increasing quantity of plastic coming into the oceans. In this study, we analysed the gastrointestinal tracts of 24 juvenile oceanic-stage loggerheads (Caretta caretta) collected off the North Atlantic subtropical gyre, in the Azores region, a key feeding ground for juvenile loggerheads. Twenty individuals were found to have ingested marine debris (83%), composed exclusively of plastic items (primarily polyethylene and polypropylene) identified by μ-Fourier Transform Infrared Spectroscopy. Large microplastics (1–5mm) represented 25% of the total number of debris and were found in 58% of the individuals sampled. Average number of items was 15.83±6.09 (±SE) per individual, corresponding to a mean dry mass of 1.07±0.41g. The results of this study demonstrate that plastic pollution acts as another stressor for this critical life stage of loggerhead turtles in the North Atlantic.
Показать больше [+] Меньше [-]Environmental drivers of sheltering behaviour in large reef fishes
2017
Kerry, James T. | Bellwood, David R.
Studies of shelter use can provide key insights into the ecology, and structural needs of mobile organisms. Using videos, we examined the usage of tabular corals by large reef fishes, over a 10week period, compared to multiple environmental drivers: visibility, tide (and depth), irradiance, wind speed (as a proxy for wave energy) and water temperature. We found that two of these predictor variables (visibility and wind speed) had a significant effect and together accounted for almost half of the variation in tabular coral usage by fishes. Increases in both variables correlated with increased shelter use. To date use of shelters by fishes has primarily been attributed to UV avoidance. Our results support this notion as more turbid conditions (reduced visibility) have an attenuating effect on UV irradiance. Additionally, tabular corals may reduce the energetic costs of increased wave energy by reducing incidental water velocity beneath the structure.
Показать больше [+] Меньше [-]Arsenic and mercury concentrations in marine fish sourced from local fishermen and fish markets in mine-impacted communities in Ratatotok Sub-district, North Sulawesi, Indonesia
2017
Bentley, Keith | Soebandrio, Amin
Mesel gold mine, Ratatotok Sub-district, North Sulawesi, Indonesia deposited about 4.5millionm3 of detoxified tailings containing arsenic (As) and mercury (Hg) via a submarine pipeline into Buyat Bay. As and Hg analysis of 216 fish muscle tissue composites from subsistence fishermen, local markets and a reference market confirmed that mean As levels were comparable between locations (range 1.71 to 2.12mg/kg wet weight (ww)) and <10% of the Australia New Zealand standard. Mean Hg concentrations were highest for the artisanal fishermen group (0.23mg/kg ww), similar between the local markets (0.11–0.14mg/kg ww) and lower at the reference market (0.04mg/kg ww). A 12-month fish availability study identified that the results were due to the different coral and deep ocean species assemblages. All mean values were <50% of the FAO/WHO/Codex standard for Hg. The results confirmed that there was no contamination from the deposited submarine tailings.
Показать больше [+] Меньше [-]Toxicity of oil and dispersant on the deep water gorgonian octocoral Swiftia exserta, with implications for the effects of the Deepwater Horizon oil spill
2017
Frometa, Janessy | DeLorenzo, Marie E. | Pisarski, Emily C. | Etnoyer, Peter J.
Benthic surveys of mesophotic reefs in the Gulf of Mexico post Deepwater Horizon (DWH) showed that Swiftia exserta octocorals exhibited significantly more injury than in years before the spill. To determine the vulnerability of S. exserta to oil and dispersants, 96h toxicity assays of surrogate DWH oil water-accommodated fractions (WAF), Corexit® 9500 dispersant, and the combination of both (CEWAF) were conducted in the laboratory. Fragment mortality occurred within 48h for some fragments in the dispersant-alone and oil-dispersant treatments, while the WAF group remained relatively unaffected. The 96h LC50 values were 70.27mg/L for Corexit-alone and 41.04mg/L for Corexit in CEWAF. This study provides new information on octocoral sensitivity to toxins, and indicates that combinations of oil and dispersants are more toxic to octocorals than exposure to oil alone. These results have important implications for the assessment of effects of the DWH spill on deep-water organisms.
Показать больше [+] Меньше [-]Phospholipid fatty acid (PLFA) analysis for profiling microbial communities in offshore produced water
2017
Fan, Fuqiang | Zhang, Baiyu | Morrill, Penny L.
A method based on phospholipid fatty acid (PLFA) analysis for profiling microbial communities in offshore produced water was optimized. The operation parameters affecting final PLFA profiling performance from the solid phase extraction (SPE) purification and fatty acid methyl esters (FAMEs) yielding process were investigated. Under the selected conditions, 92.9%, 96.3% and 92.8% of the spiked phospholipid standards C16:1 (cis-9) PC, C18:1 (cis-9) PC, and C19:0 PC were recovered, respectively, using 10mL methanol as elution solvent on a non-commercial SPE column. Over 90% of spiked C19:0 PC was recovered before sample transesterification. Four parameters including alkaline reagent, volume of acid for neutralization, time and temperature for FAMEs derivatization were examined. Gas Chromatography-Mass Spectrometry (GC-MS) was used to analyze FAMEs and the method linearities, recoveries of 29 FAMEs during transesterification, detection limits, relative standard deviations were presented. The results provided valuable information for biological reservoir souring control.
Показать больше [+] Меньше [-]Determination of hydrocarbons transported by urban runoff in sediments of São Gonçalo Channel (Pelotas – RS, Brazil)
2017
Sanches Filho, Pedro J. | Böhm, Emerson M. | Böhm, Giani M.B. | Montenegro, Gissele O. | Silveira, Lucas A. | Betemps, Glauco R.
A high concentration of hydrocarbons in the environment is indicative of pollution. To evaluate the effect of hydrocarbons transported by urban runoff, the present study analyzed total petroleum hydrocarbons (TPHs), aliphatic hydrocarbons (AHs), unresolved complex mixture (UCM), and n-alkanes of the sediments of the canal that cross the urban area of Pelotas, Rio Grande do Sul, Brazil. The carbon preference index (CPI), terrigenous/aquatic ratio (TAR), and pristane/phytane ratio were determined. The TPH content ranged from 177,043.7μg·kg−1±13.4% to 5,892,667.0μg·kg−1±5.9%. The total aliphatic content ranged from 116,268.8μg·kg−1±11.1% to 2,393,592.6μg·kg−1±7.7%, indicating chronic contamination of n-alkanes petrogenic and biogenic sources. The levels of hydrocarbons (TPH, AHs, and n-alkanes) were considered relatively high, confirming the effect of urban runoff on the drainage system of cities and their consequent effect on the estuarine region of Patos Lagoon and other water resources.
Показать больше [+] Меньше [-]Management and environmental risk study of the physicochemical parameters of ballast water
2017
Shipping is a vital industry for the global economy. Stability of ships, provided by ballast water, is a crucial factor for cargo loading and unloading processes. Ballast water treatment has practical significance in terms of environmental issues, ecosystem, and human health, because ships discharge this water into the environment before loading their cargos. This study reviews the common methods for ballast water management – exchange, heating, filtration, ultrasonic treatment, ultraviolet irradiation, chemicals, and gas supersaturation – to select the best one. This study compares water temperature, salinity, dissolved oxygen, polycyclic aromatic hydrocarbons (PAHs), and heavy metals (Co, Cr, Ni, Pb) for ballast tanks of selected ships with the recipient port environment in the Persian Gulf as a case study. The exchange of ballast water in the ocean and/or its treatment on board to prevent inadvertent effects on the environment's physicochemical conditions is related to vessel characteristics, legislation, and the environmental condition. Ecological risk study showed that the salt content in ballast water is close to that of seawater, but the values of Cr (2.1mg/l) and Ni (0.029mg/l) in ballast water are higher than those in seawater (1 and 0.004mg/l, respectively).
Показать больше [+] Меньше [-]Characteristics and sources of anthropogenic and biogenic hydrocarbons in sediments from the coast of Qatar
2017
Rushdi, Ahmed I. | Al-Shaikh, Ismail | El-Mubarak, Aarif H. | Alnaimi, Hajer A.J.A. | Al-Shamary, Noora | Hassan, Hassan M. | Assali, Mazen Abou
Surface sediment samples from the coastal zone of Qatar were collected and analyzed to determine the characteristics, and sources of anthropogenic and biogenic hydrocarbons. The main compounds in these surface sediments included n-alkanes, methyl n-alkanoates, diterpenoids, hopanes, steranes, phthalate esters, polycyclic aromatic hydrocarbons (PAHs) and unresolved complex mixture (UCM). Their total concentrations ranged from 18.7±3.7–81.1±7.5ng/g (3.7±0.6–10.4±4.8%) for n-alkanes, 8.3±2.3–51±3.4ng/g (3.0±2.0–5.6±2.0%) for methyl n-alkanoates, 1.8±0.1–10.5±1.0ng/g (1.0±0.5–0.4±0.1%) for diterpenoids, 0.0–79.3±7.4ng/g (0.0–7.9±0.6%) for hopanes, 0.0–32.9±7.9ng/g (0.0–6.5±1.0%) for steranes, 0.7±0.1–36.3±3.4ng/g (0.1±0.1–1.9±3.4%) for phthalates, 0.30±0.2–7.8±0.7ng/g (0.02±0.04–0.42±0.72%) for PAHs, and 38±9–609±57ng/g (38.5±13.4–56.5±13.4%) for UCM. The major sources of these lipids were anthropogenic petroleum residues and plasticizers (80–89%), with lesser amounts from natural higher plants and microbial residues (11–20%). Petroleum residues and plasticizer inputs to the coastal sediments of Qatar likely affect the marine ecosystems and associated species groups as well as shallow coastal nursery and spawning areas.
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