خيارات البحث
النتائج 1731 - 1740 من 4,367
Natural and anthropogenic events influence the soundscapes of four bays on Hawaii Island النص الكامل
2017
Heenehan, Heather L. | Van Parijs, Sofie M. | Bejder, Lars | Tyne, Julian A. | Southall, Brandon L. | Southall, Hugh | Johnston, David W.
The soundscapes of four bays along the Kona Coast of Hawaii Island were monitored between January 2011 and March 2013. Equivalent, unweighted sound pressure levels within standard 1/3rd-octave bands (dB re: 1μPa) were calculated for each recording. Sound levels increased at night and were lowest during the daytime when spinner dolphins use the bays to rest. A tsunami provided an opportunity to monitor the soundscape with little anthropogenic component. We detected a decrease in sound levels and variability in one of the busiest bays. During the daytime in the 3.15kHz 1/3rd octave band, we detected 92 loud outliers from vessels, aquaculture, and military mid-frequency active sonar. During one military mid-frequency active sonar event sound levels reached 45.8dB above median ambient noise levels. The differences found in the bays illustrate the importance of understanding soundscapes to effectively manage noise pollution in marine ecosystems.
اظهر المزيد [+] اقل [-]Assessment of 226Ra, 238U, 232Th, 137Cs and 40K activities from the northern coastline of Oman Sea (water and sediments) النص الكامل
2017
Darabi-Golestan, F. | Hezarkhani, A. | Zare, M.R.
Water and sediment samples were collected from northern coast of Oman Sea covering from Goatr to Hormoz canyon seaport. Water and sediment quality assessment for naturally or anthropogenic radionuclides at Oman Sea as a main strategic golf for trade and transit, is an important issue. Correspondence analysis (CA) by R-mode analysis represents that sigma(T)-temperature-conductivity-O2 parameters are well-correlated with 226Ra, 232Th and 40K. Accordingly Q-mode analysis revealed an indicator samples of ST13W for different radionuclides, ST03W for O2, and simultaneously ST34W-ST21W-ST08W-ST04W for sigma(T) parameters. The CA results overlapped with factor and cluster analysis results that explained 85.8% of total variance of water samples. Descriptive analysis of sediments indicates more significant variation than water samples. The 232Th and 226Ra generally showing that ST13D to ST25D sediments that restricted to Pi Bashk coastline are concentrated from 137Cs and 40K. By comparison with reference-values from Iran and other parts of the world, they are acceptable with respect to environmental and radioisotope hazards.
اظهر المزيد [+] اقل [-]Spatial variation in polycyclic aromatic hydrocarbon exposure in Barrow's goldeneye (Bucephala islandica) in coastal British Columbia النص الكامل
2017
Willie, Megan | Esler, Dan (Daniel) | Boyd, W Sean | Molloy, Philip | Ydenberg, Ronald C.
Barrow's goldeneyes are sea ducks that winter throughout coastal British Columbia (BC). Their diet consists primarily of intertidal blue mussels, which can accumulate PAHs; accordingly, goldeneyes may be susceptible to exposure through contaminated prey. In 2014/15, we examined total PAH concentrations in mussels from undeveloped and developed coastal areas of BC. At those same sites, we used EROD to measure hepatic CYP1A induction in goldeneyes. We found higher mussel PAH concentrations at developed coastal sites. Regionally, goldeneyes from southern BC, which has relatively higher coastal development, had higher EROD activity compared to birds from northern BC. Our results suggest goldeneyes wintering in coastal BC were exposed to PAHs through diet, with higher exposure among birds wintering in coastal areas with greater anthropogenic influence. These results suggest the mussel-goldeneye system is suitable as a natural, multi-trophic-level indicator of contemporary hydrocarbon contamination occurrence and exposure useful for establishing oil spill recovery endpoints.
اظهر المزيد [+] اقل [-]Assessment of heavy metal contamination in sediments along the coast of South Korea using Cs-normalized background concentrations النص الكامل
2017
Song, Yunho | Choi, Man Sik
To assess metal contamination in sediments along the entire coastline of South Korea, we estimated the regional background concentrations of metals and assessed the degree of contamination. Major and heavy metal concentrations, grain sizes, and sedimentation rates were analyzed. Regional background concentrations were established by identifying uncontaminated sediments in the cores, using first-order linear regression of background concentration against Cs concentration. The metal contamination of surface sediments was assessed using Korean sediment quality guidelines and a modified geo-accumulation index (Igeo⁎). In total, 14 sediments exceeded the threshold and probable effects level for Cu, 39 for Zn, and 19 for Pb. Based on Igeo⁎, most sediments were not contaminated with Cr, Co, or Ni, whereas 31% (Zn), 34% (Cu), and 43% (Pb) in total surface sediments were contaminated with other metals; 14% of total sediments were contaminated with Cu, and those above class 2 were concentrated near industrial and shipyard facilities.
اظهر المزيد [+] اقل [-]Exceptionally high abundances of microplastics in the oligotrophic Israeli Mediterranean coastal waters النص الكامل
2017
van der Hal, Noam | Ariel, Asaf | Angel, Dror L.
Seasonal sea surface microplastic distribution was recorded at 17 sites along the Israeli Mediterranean coast. Microplastics (0.3–5mm) were found in all samples, with a mean abundance of 7.68±2.38particles/m3 or 1,518,340particles/km2. Some areas had higher abundances of microplastics than others, although differences were neither consistent nor statistically significant. In some cases microplastic particles were found floating in large patches. One of these patches contained an extraordinary number of plastic particles; 324particles/m3 or 64,812,600particles/km2. Microplastic abundances in Israeli coastal waters are disturbingly high; mean values were 1–2 orders of magnitude higher than abundances reported in other parts of the world. Light-colored (white or transparent) fragments were by far more abundant than all other microplastic colors and types. The results of this study underline the need for action to reduce the flux of plastics to the marine environment.
اظهر المزيد [+] اقل [-]Potential health risk assessment of heavy metals via consumption of caviar of Persian sturgeon النص الكامل
2017
Sobhanardakani, S.
Caviar may contain high levels of toxic metals. Therefore determination of health risk assessment of the heavy metals in this luxury product is vital. In this study, an Inductively Coupled Plasma-Optical Emission Spectrometer and a Direct Mercury Analyzer were used to assess the contents of elements in caviar of wild Persian sturgeon. The results showed that the contents of Ba, Cr, Fe, Hg, Mn and Zn (mgkg−1) in caviar samples were 0.95, 0.27, 71.3, 1.44, 0.01 and 17.0, respectively. Also, Health Risk Index values were within the safe limits (HRI<1), and there is no potential health risk for adults and children via consumption of caviar. Finally, considering the contents of Fe and Hg were higher than Maximum Permissible Limits in the caviar samples related to the discharge of pollutants into the aquatic environment, monitoring of chemicals accumulation in the foodstuff is recommended.
اظهر المزيد [+] اقل [-]Spatial and temporal distribution of pesticides and PCBs in the atmosphere using XAD-resin based passive samplers: A case study in the Quequén Grande River watershed, Argentina النص الكامل
2017
Silva-Barni, M.F. | Gonzalez, M. | Wania, F. | Lei, Y.D. | Miglioranza, K.S.B.
XAD-resin based passive air samplers were deployed at 10 sites in the Quequén Grande River watershed in Argentina during three periods to evaluate the spatial and temporal variations of pesticides and PCBs in the atmosphere. Endosulfan and chlorpyrifos were the most prevalent pesticide because of their continued usage in Argentina, while DDTs, HCHs, chlordanes, dieldrin and heptachlors registered lower levels, reflecting their use in the past. Atmospheric endosulfan levels were 1–2 orders of magnitude higher during the application period (application: 800–12,000 pg/m3, pre- and post-application: <2–350 pg/m3), suggesting that its use in the area continued even after a ban came into effect. The remaining organochlorine pesticides also reached higher concentrations during this period, which is more likely attributable to temperature controlled air-surface exchange than current applications. The highest concentrations of chlorpyrifos were recorded during the application period, in particular at agricultural sites, where its use is wide-spread on soybean fields. The fungicide chlorothalonil was found predominantly at urban sites and in proximity to Quequén harbor, suggesting that its use might be domestic and as a biocide in antifouling paints. A different temporal pattern was observed for the herbicide trifluralin, suggesting its use in the early stages of the wheat-growing season during winter. Limited spatial variations in PCBs levels indicate a diffuse contamination source in the study area, while their relatively high correlation with temperature suggests re-volatilization from local sources. Relative enrichment of lighter PCBs congeners could be attributed to re-evaporation from secondary sources as well as atmospheric transport from urban sites.
اظهر المزيد [+] اقل [-]Probabilistic assessment of high concentrations of particulate matter (PM10) in Beijing, China النص الكامل
2017
Zhang, Zhi-Hong | Hu, Mao-Gui | Ren, Jing | Zhang, Zi-Yin | Christakos, George | Wang, Jin-Feng
Air pollution has become more serious in many developing countries. Heavy particulate matter (PM) air pollution is a major threat to people's respiratory and cardiopulmonary health. It is an important problem for public health research to accurately estimate the spatial distribution of high PM concentrations from a limited number of monitoring stations. In this study, a maximum entropy (MaxEnt) model was adopted to obtain the probability distribution map of high PM10 concentrations. Daily PM10 concentration data from 19 air quality monitoring stations from the years 2008–2011 were collected. Land cover, road density, and meteorological data were selected as explanatory variables entered in the model. A receiver operating characteristic (ROC) analysis was used to evaluate the performance of the MaxEnt model. The area under the ROC curve (AUC) shows that the MaxEnt model fits well in the four year period. AUC is 0.78 in 2008, 0.79 in 2009, 0.81 in 2010, and 0.80 in 2011. A probability distribution map of high PM10 concentration indicates high human health risks in regions of Beijing in areas with dense roads and buildings. During the entire research period from 2008 to 2011, the distribution of high PM10 concentration is relatively stable and it indicates that the trend of high concentration has not changed significantly during the four years. Traffic and land cover are the two most important factors that can explain more than 80% variance of PM10 from 2008 to 2011.
اظهر المزيد [+] اقل [-]A mycological baseline study based on a multidisciplinary approach in a coastal area affected by contaminated torrent input النص الكامل
2017
Fungi include a vast group of eukaryotic organisms able to colonise different natural, anthropised and extreme environments, including marine areas contaminated by metals. The present study aims to give a first multidisciplinary characterisation of marine bottom sediments contaminated by metals (Cd, Co, Cr, Cu, Ni, and Zn), originating in the water leakage from an abandoned Fe-Cu sulphide mine (Libiola, north-western Italy), and evaluate how the chemical and physical parameters of water and sediments may affect the benthic fungal communities. Our preliminary results showed the high mycodiversity of the marine sediments studied (13 genera and 23 species of marine fungi isolated), and the great physiological adaptability that this mycobiota evolved in reaction to the effects of the ecotoxic bottom sediment contamination, and associated changes in the seawater parameters.
اظهر المزيد [+] اقل [-]Aquatic ecotoxicological models and their applicability in Arctic regions النص الكامل
2017
Dose-response modeling is one of the most important steps of ecological risk assessment. It requires concentration-effects relationships for the species under consideration. There are very limited studies and experimental data available for the Arctic aquatic species. Lack of toxicity data hinders obtaining dose-response relationships for lethal (LC50 values), sub-lethal and carcinogenic effects. Gaps in toxicity data could be filled using a variety of in-silico ecotoxicological methods. This paper reviews the suitability of such methods for the Arctic scenario. Mechanistic approaches like toxicokinetic and toxicodynamic analysis are found to be better suited for interspecies extrapolation than statistical methods, such as Quantitative Structure-Activity Relationships/Quantitative Structure Activity-Activity Relationship, ICE, and other empirical models, such as Haber's law and Ostwald's equation. A novel approach is proposed where the effects of the toxicant exposure are quantified based on the probability of cellular damage and metabolites interactions. This approach recommends modeling cellular damage using a toxicodynamic model and physiology or metabolites interactions using a toxicokinetic model. Together, these models provide more reliable estimates of toxicity in the Arctic aquatic species, which will assist in conducting ecological risk assessment of Arctic environment.
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