Refinar búsqueda
Resultados 1041-1050 de 4,044
Biocompatible poly(vinyl alcohol) nanoparticle-based binary blends for oil spill control Texto completo
2016
Fouad, Rasha Refaat | Aljohani, Hind Abdullah | Shoueir, Kamel Rizq
In the current study, biocompatible and biodegradable blends based on poly(vinyl alcohol) nanoparticles – PVAn mixed with either chitosan (Ch) or starch (St) – were prepared and investigated as nanoabsorbents for oil elimination from wastewater. The use of water/dimethyl sulfoxide (DMSO) as a mixed solvent is the key factor for preparing aggregated PVAn, which is further mixed with Ch or St. Nanoblends were applied as oil absorbents, and the results showed that PVAn/St possess high adsorption capacity than PVAn/Ch and PVAn. The maximum sorption capacities (qg/g) of the PVAn/Ch sorbents for hydraulic oil, kerosene, and toluene were 33.6, 73.96, and 93.1g/g, respectively. The absorbed oil could be rapidly recovered by simple mechanical squeezing and reused without any other modification. The blends showed excellent reusability and could be reused for at least 10 times with minimal losses. The current study demonstrates the application of these blends as an ideal alternative sorbent for oil spillage cleanup.
Mostrar más [+] Menos [-]In situ soft sediment nutrient enrichment: A unified approach to eutrophication field experiments Texto completo
2016
Douglas, Emily J. | Pilditch, Conrad A. | Hines, Laura V. | Kraan, Casper | Thrush, Simon F.
Adding fertiliser to sediments is an established way of studying the effects of eutrophication but a lack of consistent methodology, reporting on enrichment levels, or guidance on application rates precludes rigorous synthesis and meta-analysis. We developed a simple enrichment technique then applied it to 28 sites across an intertidal sandflat. Fertiliser application rates of 150 and 600gNm−2 resulted in pore water ammonium concentrations respectively 1–110 and 4–580×ambient, with greater elevations observed in deeper (5–7cm) than surface (0–2cm) sediments. These enrichment levels were similar to eutrophic estuaries and were maintained for at least seven weeks. The high between-site variability could be partially explained by the sedimentary environment and macrofaunal community (42%), but only at the high application rate. We suggest future enrichment studies should be conducted in situ across large environmental gradients to incorporate real world complexity and increase generality of conclusions.
Mostrar más [+] Menos [-]Sources and sinks of microplastics in Canadian Lake Ontario nearshore, tributary and beach sediments Texto completo
2016
Ballent, Anika | Corcoran, Patricia L. | Madden, Odile | Helm, Paul A. | Longstaffe, Fred J.
Microplastics contamination of Lake Ontario sediments is investigated with the aim of identifying distribution patterns and hotspots in nearshore, tributary and beach depositional environments. Microplastics are concentrated in nearshore sediments in the vicinity of urban and industrial regions. In Humber Bay and Toronto Harbour microplastic concentrations were consistently >500 particles per kg dry sediment. Maximum concentrations of ~28,000 particles per kg dry sediment were determined in Etobicoke Creek. The microplastic particles were primarily fibres and fragments <2mm in size. Both low- and high-density plastics were identified using Raman spectroscopy. We provide a baseline for future monitoring and discuss potential sources of microplastics in terms of how and where to implement preventative measures to reduce the contaminant influx. Although the impacts of microplastics contamination on ecosystem health and functioning is uncertain, understanding, monitoring and preventing further microplastics contamination in Lake Ontario and the other Great Lakes is crucial.
Mostrar más [+] Menos [-]Antifouling paint booster biocides (Irgarol 1051 and diuron) in marinas and ports of Bushehr, Persian Gulf Texto completo
2016
Saleh, Abolfazl | Molaei, Saeideh | Sheijooni Fumani, Neda | Abedi, Ehsan
In the present study, antifouling paint booster biocides, Irgarol 1051 and diuron were measured in ports and marinas of Bushehr, Iran. Results showed that in seawater samples taken from ports and marinas, Irgarol was found at the range of less than LOD to 63.4ngL−1 and diuron was found to be at the range of less than LOD to 29.1ngL−1 (in Jalali marina). 3,4-dichloroaniline (3,4-DCA), as a degradation product of diuron, was also analyzed and its maximum concentration was 390ngL−1. Results for analysis of Irgarol 1051 in sediments showed a maximum concentration of 35.4ngg−1 dry weight in Bandargah marina. A comparison between the results of this study and those of other published works showed that Irgarol and diuron pollutions in ports and marinas of Bushehr located in the Persian Gulf were less than the average of reports from other parts of the world.
Mostrar más [+] Menos [-]Damage and recovery assessment of the Philippines' mangroves following Super Typhoon Haiyan Texto completo
2016
Long, Jordan | Giri, Chandra | Primavera, Jurgenne | Trivedi, Mandar
We quantified mangrove disturbance resulting from Super Typhoon Haiyan using a remote sensing approach. Mangrove areas were mapped prior to Haiyan using 30m Landsat imagery and a supervised decision-tree classification. A time sequence of 250m eMODIS data was used to monitor mangrove condition prior to, and following, Haiyan. Based on differences in eMODIS NDVI observations before and after the storm, we classified mangrove into three damage level categories: minimal, moderate, or severe. Mangrove damage in terms of extent and severity was greatest where Haiyan first made landfall on Eastern Samar and Western Samar provinces and lessened westward corresponding with decreasing storm intensity as Haiyan tracked from east to west across the Visayas region of the Philippines. However, within 18months following Haiyan, mangrove areas classified as severely, moderately, and minimally damaged decreased by 90%, 81%, and 57%, respectively, indicating mangroves resilience to powerful typhoons.
Mostrar más [+] Menos [-]Offshore produced water management: A review of current practice and challenges in harsh/Arctic environments Texto completo
2016
Zheng, Jisi | Chen, Bing | Thanyamanta, Worakanok | Hawboldt, Kelly | Zhang, Baiyu | Liu, Bo
Increasing offshore oil and gas exploration and development in harsh/Arctic environments require more effective offshore produced water management, as these environments are much more sensitive to changes in water quality than more temperate climates. However, the number and scope of studies of offshore produced water management in harsh/Arctic environments are limited. This paper reviews the current state of offshore produced water management, impacts, and policies, as well as the vulnerability, implications and operational challenges in harsh/Arctic environments. The findings show that the primary contaminant(s) of concern are contained in both the dissolved oil and the dispersed oil. The application of emerging technologies that can tackle this issue is significantly limited by the challenges of offshore operations in harsh/Arctic environments. Therefore, there is a need to develop more efficient and suitable management systems since more stringent policies are being implemented due to the increased vulnerability of harsh/Arctic environments.
Mostrar más [+] Menos [-]Geogenic metal mobility in a coastal inlet impacted by cannery discharge, Magdalena Bay, Baja California Sur, Mexico Texto completo
2016
O'Shea, Beth | Capistrano, Christian | Lee, William
Magdalena Bay is an important habitat for marine organisms, some of which have been the subject of metal bioaccumulation studies. Cannery waste is discharged into the bay providing a plausible source of contamination but this study finds that some metals occur geogenically. Bay sediments and rocks (n=59) were analyzed for total metals and clustered (HCA) into two distinct groups with PCA indicating concentrations of Cr, Cu, Mn, and Ni influenced samples near ophiolite outcrops, which reported some metal concentrations exceeding averages in the crust by an order of magnitude (up to 4450ppm Cr and 1269ppm Ni). Metals at the cannery are rarely elevated above crustal averages except Zn (max. 160ppm), however, acid-extracted Zn was below recommended sediment quality guidelines in contrast to 80% of ophiolitic samples reporting Ni extractability exceeding such guidelines. This study raises awareness of geogenic metals when considering sources of contamination in marine environments.
Mostrar más [+] Menos [-]Evaluation of an urban modelling system against three measurement campaigns in London and Birmingham Texto completo
2016
Srimath, Srinivas T.G. | Sokhi, Ranjeet | Karppinen, Ari | Singh, Vikas | Kukkonen, Jaakko
The results of three measurement campaigns are presented in this study. The campaigns have been undertaken at an urban roadside site in London, for more than a year and three months in 2003–2004 and for a year in 2008, and at an urban background site in Birmingham, U.K, for about four months in 2002. The concentrations of PM2.5, PM10, NOx and NO2 were predicted using the roadside dispersion model CAR-FMI, combined with a national U.K. emission model, a meteorological pre-processor, and measured values at urban background stations. The agreement of the predicted and measured hourly and daily time-series has been assessed statistically for all of the campaigns and pollutants. For instance, the Indices of Agreement (IA) in all the campaigns ranged from 0.68 to 0.78, 0.87, from 0.70 to 0.80, and from 0.61 to 0.83 for PM2.5, PM10, NOx and NO2, respectively. However, in case of the campaigns in London, both the PM fractions and the nitrogen oxide concentrations were under-predicted. The model performance in terms of atmospheric stability, wind speeds and other factors was analysed, and reasons for the disagreement of predictions and measurements have been discussed. It is useful to consider the model performance statistics for several measurement campaigns simultaneously, as some of the results were found to be specific only to one or two campaigns. The spatial concentration distribution of NOx in London for 2008 has also been presented.
Mostrar más [+] Menos [-]Coral microbial community dynamics in response to anthropogenic impacts near a major city in the central Red Sea Texto completo
2016
Ziegler, Maren | Roik, Anna | Porter, Adam | Zubier, Khalid | Mudarris, Mohammed S. | Ormond, Rupert | Voolstra, Christian R.
Coral-associated bacteria play an increasingly recognized part in coral health. We investigated the effect of local anthropogenic impacts on coral microbial communities on reefs near Jeddah, the largest city on the Saudi Arabian coast of the central Red Sea. We analyzed the bacterial community structure of water and corals (Pocillopora verrucosa and Acropora hemprichii) at sites that were relatively unimpacted, exposed to sedimentation & local sewage, or in the discharge area of municipal wastewaters. Coral microbial communities were significantly different at impacted sites: in both corals the main symbiotic taxon decreased in abundance. In contrast, opportunistic bacterial families, such as e.g. Vibrionaceae and Rhodobacteraceae, were more abundant in corals at impacted sites. In conclusion, microbial community response revealed a measurable footprint of anthropogenic impacts to coral ecosystems close to Jeddah, even though the corals appeared visually healthy.
Mostrar más [+] Menos [-]Study of chemical species associated with fine particles and their secondary particle formation at semi-arid region of India Texto completo
2016
Satsangi, P.G. | Pipal, A.S. | Budhavant, K.B. | Rao, P.S.P. | Taneja, A.
The fine particles (PM2.5) were collected for 24 h from Agra atmosphere and chemically characterized during the one year study period. The average concentration of PM2.5 was 90.21 ± 20.62 μg m−3 which is higher than NAAQS and WHO annual standards and their seasonal trend was winter > summer > monsoon. Ionic study indicates that cations were dominant in comparison to anions. Seasonally, F−, Ca2+ and Mg2+ were higher during summer period and Cl−, NO3−, NH4+ and K+ were higher during monsoon period while SO42− was higher during winter season. The ratios Ca2+/Na+, Mg2+/Na+ and SO42−/Na+ were higher, while Cl−/Na ratio was lower than sea water ratio indicating the incorporation of non marine constituents in aerosols. The observed Cl−/Na+ (average 0.71) deviate considerable from the Sea water ratio suggesting either a fractionation of Cl− or enrichment of Na+ as there was significant deviation from marine sources. Linear correlation was observable between nss-Ca2+ and nss-Mg2+ with HCO3− throughout the annual seasonal cycle (HCO3−: Ca = 0.59, HCO3−: Mg2+ = 0.53) suggesting the origination of these species from soil dust. The calculated conversion ratio of ‘S’ (CRS) was lower than ‘N’ (CRN) which suggests that the secondary formation of NO3− aerosol from NO2 was more predominant than SO42−. Trajectory analysis indicates that long range transportation also contributes to PM2.5 mass over the measurement site.
Mostrar más [+] Menos [-]